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GANEXT Newsletter No. 03 April 2020

GaN Technology for Optoelectronics & Electronics

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GANEXT | GaN Technology for Optoelectronics & Electronics Newsletter No. 03 | 2

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IMPORTANT NOTE: The end of GaNeX Cluster of Excellence program (Labex 2012-2019) was scheduled on December 2019. However, the French government decided to expand the labex program for five additional years, in order to further strengthen the synergy between French academic research organizations and industrial players in the field of GaN optoelectronics and electronics. Therefore, GANEXT Cluster of Excellence program will replace and succeed GaNeX for the next five years (2020-2024). Accordingly, the GANEXT newsletter will follow and adapt to the new program, focusing on scientific publications, patent applications and press releases related to optoelectronics (LED, µ-LED, laser, photonics, etc.) and electronics (power, RF, advanced electronics, etc.), ruling out publications which are not related to one of these two families of applications. For instance, publications dealing with MEMS, sensors, photovoltaics, nanostructures, semi-polar and non-polar materials, fundamental physics, etc. that do not obviously relate to optoelectronic or electronic applications will not be included in the GANEXT newsletter. Besides, a panel of GANEXT experts will continue to interact with Knowmade team in order to select the most relevant publications of the month, consistently with GANEXT’s ongoing projects.

TABLE OF CONTENTS

METHODOLOGY ........................................................................................................... 3

SCIENTIFIC PUBLICATIONS............................................................................................ 4

OPTOELECTRONICS ....................................................................................................... 4

ELECTRONICS .............................................................................................................. 16

PRESS RELEASES ......................................................................................................... 33

PATENT APPLICATIONS .............................................................................................. 65


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METHODOLOGY


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SCIENTIFIC PUBLICATIONS Selection of new scientific articles

OPTOELECTRONICS Group leader: Bruno Gayral (CEA)

Information selected by Julien Brault (CNRS-CRHEA) and Maria Tchernycheva (CNRS-C2N) Material-to-device performance correlation for

AlGaN-based solar-blind p–i–n photodiodes Centre for Nano Science and Engineering, Indian Institute of

Science, Bangalore, 560012, India

Semiconductor Science and Technology

https://doi.org/10.1088/1361-6641/ab5df8

We report on crystalline quality-to-device

performance correlation for self-powered

Al0.40Ga0.60N, p–i–n ultraviolet (UV) photodetectors

on c-plane sapphire. The active p–i–n detector stack

was grown over an AlN buffer. Careful optimization of

the nucleation density on growth surface helped

achieve a two-orders and one-order of magnitude

reduction in the screw and edge dislocation density in

the buffer layer, respectively. This resulted in a nine-

orders of magnitude reduction in the reverse leakage

current from 4.3 mA to 4.2 pA (at 10 V).

Correspondingly, a thirteen-fold enhancement in the

zero-bias external quantum efficiency (EQE) from 3.4%

to 45.5%, when measured under 289 nm front-

illumination was also observed. The detector epi-stack

grown over the optimal AlN buffer layers led to the

realization of high-performance p–i–n detectors with

a dark current density below 4 nA cm−2 at 10 V and a

zero-bias EQE of 74.7% under back-illumination. This

is one of the highest zero-bias EQE reported for solar-

blind detectors realized on template-free and mask-

free III-nitrides grown using metal organic chemical

vapor deposition on any substrate. The deep-UV-to-

visible rejection ratio exceeded 106 while the deep-

UV-to-near UV rejection exceeded 103. The thermal-

noise limited detectivity was estimated to be 4 × 1014

cm Hz1/2 W−1. Hopping conduction along screw

dislocation-mediated localized trap states was found

to be the dominant carrier transport mechanism in the

samples exhibiting high reverse leakage. For these

samples, the responsivity (photocurrent) exhibited an

exponential variation with reverse bias and a

nonlinear variation with input optical power. This is

explained using a hole-trapping associated gain

mechanism and its impact on the transient

characteristics of the detectors is investigated. A 6 × 1

linear array of the highest EQE detectors was realized

and detector performance parameters were found to

be comparable before and after wire bonding. This

study is expected to enhance the understanding of III-

nitrides-based vertical, self-powered detectors and

benefit the development of high-performance, focal

plane arrays using less complicated growth

techniques.

Strongly localized carriers in Al-rich AlGaN/AlN single

quantum wells grown on sapphire substrates OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055

Regensburg, Germany

Institut für Festkörperphysik, Technische Universität Berlin,

Hardenbergstr. 36, 10623 Berlin, Germany

Journal of Applied Physics

https://doi.org/10.1063/1.5144152

Carrier dynamics in AlGaN-based single quantum well

(QW) structures grown on sapphire are studied by

means of time-integrated and time-resolved

photoluminescence spectroscopy (PL) in a wide

temperature range from 5 K to 350 K. The samples

cover a broad compositional range, with aluminum

contents ranging between 42% and 60% and QW

widths between 1.5 nm and 2.5 nm. All samples reveal

the characteristic “S”-shape temperature dependence

of the PL emission energy as frequently reported in

InGaN-based systems, albeit with significantly larger

localization strengths of up to 60 meV. It is shown that

in the compositional range investigated, carrier

localization is determined primarily by the QW width

and, in contrast, exhibits a much weaker dependence

on aluminum concentration. By the combination of

time-integrated and time-resolved PL measurements,

the localization of carriers is demonstrated to have a

significant impact on the recombination dynamics of

AlGaN/AlN QWs grown on sapphire, heavily affecting

the internal quantum efficiency and efficiency droop

even in standard LED operation conditions.

https://doi.org/10.1088/1361-6641/ab5df8

https://doi.org/10.1063/1.5144152


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Simultaneous emission–detection operation of

vertical-structure LED Nanjing University of Posts and Telecommunications,

Nanjing, People's Republic of China

Japanese Journal of Applied Physics

https://doi.org/10.35848/1347-4065/ab7215

The overlap between the emission and detection

spectra of an LED allows one single LED to exhibit both

light emission and detection simultaneously, wherein

the LED can function as a transmitter and a receiver at

the same time for communication using light. Here, we

report the simultaneous emission–detection

operation of vertical-structure LEDs, which are

implemented on an III-nitride-on-silicon platform. The

III-nitride epitaxial films are thinned without an etch

hard mask to suppress optically-confined modes

inside the LED. The simultaneous emission–detection

operation occurs when the forward voltage of the LED

is larger than the turn-on voltage V th. The measured

current is a sum of the driving current and the

photocurrent generated by external light. By

integrating a feedback circuit, the photocurrent is

extracted from the superimposed current and

consequently converted into a control signal to

regulate the driving current, leading to the automatic

adjustment of light output of the LED.

Room-temperature operation of AlGaN ultraviolet-B

laser diode at 298 nm on lattice-relaxed

Al0.6Ga0.4N/AlN/sapphire Innovative Devices R&D Center, Asahi-Kasei Corporation,

Fuji, Shizuoka 416-8501, Japan

Faculty of Science and Technology, Meijo University,

Nagoya, Aichi 468-8502, Japan

Graduate School of Regional Innovation Studies, Mie

University, Tsu, Mie 514-8507, Japan

Akasaki Research Center, Nagoya University, Nagoya, Aichi

464-8603, Japan

Applied Physics Express

https://doi.org/10.35848/1882-0786/ab7711

An AlGaN ultraviolet-B laser diode at 298nm was

realized at room temperature using pulse operation.

The laser diode has a lattice-relaxed Al0.6Ga0.4N layer

from the underlying AlN/sapphire template and a

composition-graded p-AlGaN cladding layer. The

multimodal laser spectrum with proper polarization

properties at 298 nm was obtained over the threshold

current at 0.90 A corresponding to 67kA.cm–2. By

broadening the width of the p-electrode to 11.5μm,

the threshold current density decreased to 41kA.cm–2.

Evidence for trap-assisted Auger recombination in

MBE grown InGaN quantum wells by electron

emission spectroscopy Materials Department, University of California, Santa

Barbara, California 93106, USA

Institute of Applied Research, Vilnius University, Sauletekio

9-3, 10222 Vilnius, Lithuania

Laboratoire de Physique de la Matière Condensée, CNRS,

Ecole Polytechnique, IP Paris, 91128 Palaiseau Cedex,

France

Applied Physics Letters

https://doi.org/10.1063/1.5125605

We report on the direct measurement of hot electrons

generated in the active region of blue light-emitting

diodes grown by ammonia molecular beam epitaxy by

electron emission spectroscopy. The external

quantum efficiency of these devices is <1% and does

not droop; thus, the efficiency losses from the

intrinsic, interband, electron–electron–hole, or

electron–hole–hole Auger should not be a significant

source of hot carriers. The detection of hot electrons

in this case suggests that an alternate hot electron

generating process is occurring within these devices,

likely a trap-assisted Auger recombination process.

Ultraviolet Stimulated Emission in AlGaN Layers

Grown on Sapphire Substrates using Ammonia and

Plasma‐Assisted Molecular Beam Epitaxy Institute of Physics of NAS of Belarus, 68 Nezalezhnasci Ave,

Minsk, 220072 Belarus

physica status solidi a

https://doi.org/10.1002/pssa.201900927

Ammonia and plasma‐assisted (PA) molecular beam

epitaxy modes are used to grow AlN and AlGaN

epitaxial layers on sapphire substrates. It is

determined that the increase of thickness of AlN

buffer layer grown by ammonia‐MBE from 0.32 μm to

1.25 μm results in the narrowing of 101 X‐Ray rocking

curves whereas no clear effect on 002 X‐Ray rocking

curve width is observed. It is shown that strong GaN

https://doi.org/10.35848/1347-4065/ab7215

https://doi.org/10.35848/1882-0786/ab7711

https://doi.org/10.1063/1.5125605



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decomposition during growth by ammonia‐MBE

causes AlGaN surface roughening and compositional

inhomogeneity, which leads to deterioration of its

lasing properties. AlGaN layers grown by ammonia‐

MBE at optimized temperature demonstrate

stimulated emission (SE) peaked at λ = 330 nm, 323

nm, 303 nm and 297 nm with the SE threshold values

of 0.7 MW cm−2, 1.1 MW cm−2, 1.4 MW cm−2 and 1.4

MW cm−2, respectively. In comparison to these,

AlGaN layer grown using PA‐MBE pulsed modes

(migration‐enhanced epitaxy, metal‐modulated

epitaxy, and droplet elimination by thermal annealing)

shows a SE with a relatively low threshold (0.8 MW

cm−2) at the considerably shorter wavelength of λ =

267 nm.

Theoretical analysis of a white-light LED array based

on a GaN nanorod structure National Center for International Joint Research of

Electronic Materials and Systems, Henan Key Laboratory of

Laser and Opto-electric Information Technology, School of

Information Engineering, Zhengzhou University, Zhengzhou

450052, China

Department of Traffic Information Engineering, Henan

College of Transportation, Zhengzhou 450005, China

Institute of Photonics and Optoelectronics, and Department

of Electrical Engineering, National Taiwan University, No. 1,

Section 4, Roosevelt Road, Taipei 10617, Taiwan

Applied Optics

https://doi.org/10.1364/AO.387059

Based on the experimentally demonstrated In content

distribution in the InGaN/GaN quantum wells on a

two-section GaN nanorod (NR) sidewall, a white-light

light-emitting diode (LED) without phosphor is

designed and simulated. Following the dependencies

of the In diffusion length and incorporation ratio on NR

geometric variables of a theoretical model, the height,

radius, and tapering section geometry of the GaN NR

are designed for controlling the relative intensities of

a blue and a yellow emission component to mix into

white light. The higher-In upper section of the NR is

first excited to emit a relatively stronger yellow

component when injection current is low. As the

injection current increases, more current spreads into

the lower-In lower section, eventually leading to a

stronger blue emission component. The proposed NR

LED structure provides an alternative solution for

phosphor-free white-light generation.

Intrinsically p-type cuprous iodide semiconductor for

hybrid light-emitting diodes Peta Lux Inc., 3F TLi Building, 12 Yanghyeon-ro, 405 beon-

gil, Jungwon-gu, Seongnam-si, Gyeonggi-do, 13438,

Republic of Korea

Department of Electrical and Computer Engineering and

Center for Quantum Information Processing, University of

Seoul, 163 Seoulsiripdae-ro, Dongdaemun-gu, Seoul, 02504,

Republic of Korea

Physics Department, Charles E. Schmidt College of Science,

Florida Atlantic University, 777 Glades Road, Boca Raton, FL,

33431-0991, USA

Post-Silicon Semiconductor Institute, Korea Institute of

Science and Technology Hwarang-ro 14 gil, Seoungbuk-ku,

Seoul, 02792, Republic of Korea

Department of Physics, Kyung Hee University, 26

Kyungheedae-ro, Dongdaemun-gu, Seoul, 02447, Republic

of Korea

Electronics Department, Catholic University of Daegu, 13

Hayang-Ro, Hayang-Eup, Gyeongsan-si, Gyeongbuk, 38430,

Republic of Korea

WONIK IPS, 75 Jinwisandan-ro, Jinwi-myeon, Pyeingtaek-si,

Gyeonggi-do, 17709, Republic of Korea

TLi Inc., 10 F TLi Building, 12 Yanghyeon-ro, 405 beon-gil,

Jungwon-gu, Seongnam-si, Gyeonggi-do, 13438, Republic of

Korea

Department of Materials Science & Engineering, Yonsei

University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722,

Republic of Korea

Yonsei-KIST Convergence Research Institute, 50 Yonsei-ro,

Seodaemun-gu, Seoul, 03722, Republic of Korea

Scientific Reports

https://doi.org/10.1038/s41598-020-61021-2

Cuprous halides, characterized by a direct wide band-

gap and a good lattice matching with Si, is an intrinsic

p-type I-VII compound semiconductor. It shows

remarkable optoelectronic properties, including a

large exciton binding energy at room temperature and

a very small piezoelectric coefficient. The major

obstacle to its application is the difficulty in growing a

single-crystal epitaxial film of cuprous halides. We first

demonstrate the single crystal epitaxy of high quality

cuprous iodide (CuI) film grown on Si and sapphire

substrates by molecular beam epitaxy. Enhanced

photoluminescence on the order of magnitude larger

than that of GaN and continuous-wave optically

https://doi.org/10.1364/AO.387059

https://doi.org/10.1038/s41598-020-61021-2


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pumped lasing were found in MBE grown CuI film. The

intrinsic p-type characteristics of CuI were confirmed

using an n-AlGaN/p-CuI junction that emits blue light.

The discovery will provide an alternative way towards

highly efficient optoelectronic devices compatible

with both Si and III-nitride technologies.

On the origin for the hole confinement into apertures

for GaN-based VCSELs with buried dielectric

insulators School of Electronics and Information Engineering, Hebei

University of Technology, Key Laboratory of Electronic

Materials and Devices of Tianjin, 5340 Xiping Road, Beichen

District, Tianjin, 300401, China

State Key Laboratory of Reliability and Intelligence of

Electrical Equipment, 5340 Xiping Road, Beichen District,

Tianjin, 300401, China

Optics Express

https://doi.org/10.1364/OE.385787

A better lateral current confinement is essentially

important for GaN-based vertical-cavity-surface-

emitting lasers (VCSELs) to achieve lasing condition.

Therefore, a buried insulator aperture is adopted.

However, according to our results, we find that the

current cannot be effectively laterally confined if the

insulator layer is not properly selected, and this is

because of the unique feature for GaN-based VCSELs

grown on insulating substrates with both p-electrode

and n-electrode on the same side. Our results indicate

that the origin for the current confinement arises from

lateral energy band bending in the p-GaN layer rather

than the electrical resistivity for the buried insulator.

The lateral energy band in the p-GaN layer can be

more flattened by using a buried insulator with a

properly larger dielectric constant. Thus, less bias can

be consumed by the buried insulator, enabling better

lateral current confinement. On the other hand, the

bias consumption by the buried insulator is also

affected by the insulator thickness, and we propose to

properly decrease the insulator layer thickness for

reducing the bias consumption therein and achieving

better lateral current confinement. The improved

lateral current confinement will correspondingly

enhance the lasing power. Thanks to the enhanced

lateral current confinement, the 3dB frequency will

also be increased if proper buried insulators are

adopted.

GaN Single Nanowire p–i–n Diode for High-

Temperature Operations ECE Department, Hong Kong University of Science and

Technology, Kowloon 999077, Hong Kong

School of Information Science and Technology,

ShanghaiTech University, Shanghai 201210, China

ACS Appl. Electron. Mater.

https://doi.org/10.1021/acsaelm.9b00801

III-Nitride single nanowire (NW)-based p–i–n diode

was fabricated using a top–down etching method and

its electrical and optoelectronic characteristics were

investigated from room temperature to high

operation temperatures up to 150 °C. The NW p–i–n

diode exhibited good rectifying I–V properties at all

measurement temperatures and the forward current

could be further enhanced when the temperature was

increased. Simulation-based data fitting revealed that

the enhanced conduction was a result of increased

carrier concentration inside the NW, especially holes

in the drift layer, as well as reduced contact resistance.

The reverse leakage current was kept low even at

elevated temperatures so that the UV (∼365 nm)

responsivity remained high for a wide temperature

range, suggesting the feasibility of NW p–i–n diode for

rectifying purposes and UV photon detection

applications in high-temperature environments.

Room-temperature operation of near-infrared light-

emitting diode based on Tm-doped GaN with ultra-

stable emission wavelength Division of Materials and Manufacturing Science, Graduate

School of Engineering, Osaka University, 2-1 Yamadaoka,

Suita, Osaka 565-0871, Japan

Journal of Applied Physics

https://doi.org/10.1063/1.5140715

Near-infrared (NIR) light with a wavelength of 650–

950 nm is used for various biomedical applications.

Although NIR emitters are typically based on GaAs-

related materials, they contain toxic elements, and the

emission wavelength can easily shift during the device

operation due to temperature changes and current

injection levels. On the other hand, Tm3+, which is one

of the rare-earth ions, can generate ultra-stable NIR

luminescence with a wavelength of ∼800nm, based on

3H4–3H6 transitions in a 4f shell, and we have recently

https://doi.org/10.1364/OE.385787

https://doi.org/10.1021/acsaelm.9b00801

https://doi.org/10.1063/1.5140715


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focused on Tm-doped GaN (GaN:Tm) based light-

emitting diodes (LEDs) as novel NIR emitters. In this

paper, we present a demonstration of a NIR-LED based

on GaN:Tm grown by the organometallic vapor phase

epitaxy method with optimized growth conditions and

structures, where the parasitic reaction is well

suppressed. NIR luminescence from the GaN:Tm-

based LED is derived from 3H4–3H6 transitions of

Tm3+ ions and consists of three dominant peaks at

795, 806, and 814 nm. The turn-on voltage of the NIR-

LED is ∼6.9 V, and it is significantly lower than the

previously reported electroluminescent devices based

on GaN:Tm with impact ionization processes. From a

current dependence of the electroluminescence

spectra and temperature-dependent

photoluminescence for the NIR-LED, the peak shifts

are determined to be <7.6 pm/mA and ∼1.3 pm/K,

respectively.

Growth of strain-relaxed InGaN on micrometer-sized

patterned compliant GaN pseudo-substrates Department of Electrical and Computer Engineering,

University of California Santa Barbara, Santa Barbara,

California 93106, USA

Materials Department, University of California, Santa


Department of Physics, University of California, Santa



https://doi.org/10.1063/5.0001480

The compliant behavior of high fill-factor 10 × 10 μm2

square patterned 60–140 nm thick GaN-on-porous-

GaN tiles was demonstrated by utilizing porous GaN as

a semi-flexible underlayer. High resolution x-ray

diffraction measurements showed a larger a-lattice

constant of InGaN layers deposited on these

patterned GaN-on-porous GaN pseudo-substrates in

comparison to those deposited on co-loaded planar

GaN-on-sapphire templates. Additionally, InGaN

based light emitting diode (LED) structures deposited

on these GaN pseudo-substrates exhibited room

temperature electroluminescence at 547 nm

compared to 506 nm for the LED structures grown on

co-loaded planar GaN on sapphire templates,

corresponding to a redshift of around 40 nm. The

longer emission wavelength was associated with the

higher indium incorporation into the InGaN quantum

wells deposited on the compliant GaN pseudo-

substrates, owing to a reduced lattice mismatch

between the quantum well and the n-InGaN base

layers grown on the compliant pseudo-substrates, due

to the composition pulling effect.

Development of microLED Department of Electrical and Computer Engineering, Texas

Tech University, Lubbock, Texas 79409, USA


https://doi.org/10.1063/1.5145201

This perspective provides an overview of early

developments, current status, and remaining

challenges of microLED (μLED) technology, which was

first reported in Applied Physics Letters in 2000 [S. X.

Jin, J. Li, J. Z. Li, J. Y. Lin and H. X. Jiang, "GaN Microdisk

Light Emitting Diodes," Appl. Phys. Lett. 76, 631

(2000)]. Today, microLED is recognized as the ultimate

display technology and is one of the fastest-growing

technologies in the world as technology giants utilize

it on a wide range of products from large flat panel

displays and televisions, wearable displays, and virtual

reality displays to light sources for the neural interface

and optogenetics. It is anticipated that the collective

R&D efforts worldwide will bring microLED products

not only to the mass consumer electronic markets but

also to serve the society on the broadest scale by

encompassing sectors in medical/health, energy,

transportation, communications, and entertainment.

Role of underlayer for efficient core-shell InGaN QWs

grown on m-plane GaN wire sidewalls Univ. Grenoble Alpes, CEA, IRIG, PHELIQS, NPSC, Grenoble

38000, France

Univ. Grenoble Alpes, CNRS, Institut Néel, Grenoble 38000,

France

Univ. Grenoble Alpes, CEA, IRIG, MEM, LEMMA, Grenoble

38000, France

Univ. Grenoble Alpes, CEA, IRIG, MEM, NRS, Grenoble

38000, France

ACS Appl. Mater. Interfaces

https://doi.org/10.1021/acsami.9b19314

Different types of buffer layers like InGaN underlayer

(UL) and InGaN/GaN superlattices are now well-

known to significantly improve the efficiency of c-

plane InGaN/GaN based light emitting diodes (LEDs).

https://doi.org/10.1063/5.0001480

https://doi.org/10.1063/1.5145201

https://doi.org/10.1021/acsami.9b19314


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The present work investigates the role of two different

kinds of pre-growth layers (low In-content InGaN UL

and GaN UL namely “GaN spacer”) on the emission of

core-shell m-plane core-shell single InGaN/GaN

quantum well (QW) grown around Si-doped c -̅GaN

microwires obtained by silane-assisted MOVPE.

According to photo- and cathodoluminescence

measurements performed at room temperature, an

improved efficiency of light emission at 435 nm with

internal quantum efficiency > 15 % has been achieved

by adding a GaN spacer prior to the growth of QW. As

revealed by scanning transmission electron

microscopy, an ultra-thin residual layer containing Si

located at the wire sidewall surfaces favors the

formation of high-density of extended defects

nucleated at the first InGaN QW. This contaminated

residual incorporation is buried by the growth of GaN

spacer and avoids the structural defect formation,

therefore explaining the improved optical efficiency.

No further improvement is observed by adding the

InGaN UL to the structure, which is confirmed by

comparable values of the effective carrier lifetime

estimated from time-resolved (TR) experiments.

Contrary to the case of planar c-plane QW where the

improved efficiency is attributed to a strong decrease

of point defects, the addition of an InGaN UL seem to

have no influence in the case of radial m-plane QW.

Realization of ultra-high quality InGaN platelets to be

used as relaxed templates for red microLEDs NanoLund, Lund University, Box 118, S-221 00 Lund,

Sweden

RISE Research Institutes of Sweden AB, 22370 Lund, Sweden

Division of Synchrotron Radiation Research, Department of

Physics, Lund University, Box 118, S-221 00 Lund, Sweden

Department of Mechanical Engineering, Lund University,

Box 118, S-22100 Lund, Sweden

ACS Appl. Mater. Interfaces

https://doi.org/10.1021/acsami.0c00951

In this work, arrays of predominantly relaxed InGaN

platelets with indium contents of up to 18%, free from

dislocations and offering a smooth top c-plane, are

presented. The InGaN platelets are grown by metal-

organic vapor phase epitaxy on a dome-like InGaN

surface formed by chemical mechanical polishing of

InGaN pyramids defined by six equivalent {101 1̅}

planes. The dome-like surface is flattened during

growth, through the formation of bunched steps,

which are terminated when reaching the inclined

{101 1̅} planes. The continued growth takes place on

the flattened top c-plane with single bilayer surface

steps initiated at the six corners between the c-plane

and the inclined {101 1̅} planes, leading to the

formation of high quality InGaN layers. The top c-plane

of the as-formed InGaN platelets can be used as a

high-quality template for red microLEDs.

Graphene‐Assisted Epitaxy of Nitrogen Lattice

Polarity GaN Films on Non‐Polar Sapphire Substrates

for Green Light Emitting Diodes State Key Laboratory for Mesoscopic Physics and Frontiers

Science Center for Nano-optoelectronics School of Physics,

Peking University, Beijing 100871, P. R. China

State Key Laboratory of Integrated Optoelectronics, College

of Electronic Science and Engineering, Jilin University,

Changchun 130012, P. R. China

Electron Microscopy LaboratorySchool of Physics, Peking

University, Beijing 00871, P. R. China

Collaborative Innovation Center of Quantum Matter, Beijing

100871, P. R. China

Advanced Functional Materials

https://doi.org/10.1002/adfm.202001283

Lattice polarity is a key point for hexagonal

semiconductors such as GaN. Unfortunately, only Ga‐

polarity GaN have been achieved on graphene till now.

Here, the epitaxy of high quality nitrogen‐polarity GaN

films on transferred graphene on non‐polar sapphire

substrates by molecular beam epitaxy is reported. This

success is achieved through atomic nitrogen

irradiation, where C N bonds are formed in graphene

and provide nucleation sites for GaN and leading to N‐

polarity GaN epitaxy. The N‐polarity characteristics are

confirmed by chemical etching and transmission

electron microscopy measurement. Due to the higher

growth temperature of InGaN at N‐polarity than that

at Ga‐polarity, green light emitting diodes are

fabricated on the graphene‐assisted substrate, where

a large redshift of emission wavelength is observed.

These results open a new avenue for the polarity

modulation of III‐nitride films based on 2D materials,

and also pave the way for potential application in

longer wavelength light emitting devices.

https://doi.org/10.1021/acsami.0c00951

https://doi.org/10.1002/adfm.202001283


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Subwavelength-scale nanorods implemented

hexagonal pyramids structure as efficient light-

extraction in Light-emitting diodes Department of Materials Science and Engineering, Pohang

University of Science and Technology (POSTECH), Pohang,

790-784, Korea

Division of Advanced Materials Science, Pohang University

of Science and Technology (POSTECH), Pohang, 790-784,

Korea

Scientific Reports

https://doi.org/10.1038/s41598-020-62257-8

Subwavelength-scale nanorods were implemented on

the hexagonal pyramid of photochemically etched

light-emitting diodes (LEDs) to improve light

extraction efficiency (LEE). Sequential processes of Ag

deposition and inductively coupled plasma etching

successfully produce nanorods on both locally

unetched flat surface and sidewall of hexagonal

pyramids. The subwavelength-scale structures on flat

surface offer gradually changed refractive index, and

the structures on side wall of hexagonal pyramid

reduce backward reflection, thereby enhancing

further enhancement of the light extraction efficiency.

Consequently, the nanorods implemented LED shows

a remarkable enhancement in the light output power

by 14% compared with that of the photochemically

etched LEDs which is known to exhibit the highest light

output power. Theoretical calculations using a

rigorous coupled wave analysis method reveal that the

subwavelength-scale nanorods are very effective in

the elimination of TIR as well as backward reflections,

thereby further enhancing LEE of the LEDs.

TE/TM mode full-spatial decomposition of AlGaN-

based deep ultraviolet light-emitting diodes Wuhan National Laboratory for Optoelectronics, Huazhong

University of Science and Technology, Wuhan 430074,

People's Republic of China

Journal of Physics D: Applied Physics

https://doi.org/10.1088/1361-6463/ab740b

The full-spatial decomposition of transverse electric

(TE)/transverse magnetic (TM) mode in AlGaN-based

deep ultraviolet light-emitting diodes (DUV-LEDs) has

been experimentally investigated by introducing self-

built light intensity test system mainly composed of

angle resolution bracket, Glan–Taylor prism and

spectrometer. Through roughening the sapphire

sidewall, the extraction efficiency of DUV-LED is

improved, for both TE and TM mode light with no

polarization selectivity. The introduction of self-built

light intensity metrology system has been reflected via

scribing the sapphire sidewalls using various laser

conditions, which show a reliability in the

enhancement validation of the light extraction

efficiency. More importantly, the self-built light

intensity test system enables effective feedback on

epitaxial structures and chip structure design and

provides a new perspective to design high efficiency

AlGaN-based DUV-LEDs.

Self-Aligned Hierarchical ZnO Nanorod/NiO

Nanosheet Arrays for High Photon Extraction

Efficiency of GaN-Based Photonic Emitter Department of Advanced Convergence Technology,

Research Institute of Advanced Convergence Technology,

Korea Polytechnic University, Gyeonggi-do 15073, Korea

Department of Nano & Semiconductor Engineering, Korea

Polytechnic University, Gyeonggi-do 15073, Korea

Department of Electrical Engineering and Computer

Science, University of Michigan, Ann Arbor, MI 48109, USA

Micromachines

https://doi.org/10.3390/mi11040346

Advancements in nanotechnology have facilitated the

increased use of ZnO nanostructures. In particular,

hierarchical and core–shell nanostructures, providing

a graded refractive index change, have recently been

applied to enhance the photon extraction efficiency of

photonic emitters. In this study, we demonstrate self-

aligned hierarchical ZnO nanorod (ZNR)/NiO

nanosheet arrays on a conventional photonic emitter

(C-emitter) with a wavelength of 430 nm. These

hierarchical nanostructures were synthesized through

a two-step hydrothermal process at low temperature,

and their optical output power was approximately

17% higher than that of ZNR arrays on a C-emitter and

two times higher than that of a C-emitter. These

results are due to the graded index change in

refractive index from the GaN layer inside the device

toward the outside as well as decreases in the total

internal reflection and Fresnel reflection of the

photonic emitter.

https://doi.org/10.1038/s41598-020-62257-8

https://doi.org/10.1088/1361-6463/ab740b

https://doi.org/10.3390/mi11040346


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A new model on recombination dynamics of polar

InGaN/GaN MQW LED and IQE measurement Laboratory of optoelectronic materials & detection

technology, Guangxi Key Laboratory for the Relativistic

Astrophysics, School of Physics Science & Technology,

Guangxi University, Nanning, 530004 People's Republic of

China

Center on Nanoenergy Research, Guangxi University,

Nanning, 530004 People's Republic of China

HC Semitek Corporation, Zhangjiagang, 215600 People's

Republic of China


https://doi.org/10.1088/1361-6641/ab73ed

Understanding the recombination nature in a polar

InGaN/GaN multiple quantum well (MQW) light-

emitting diode (LED) or similar device is critical for

their further performance enhancements. This paper

reports a new theoretical model for investigating the

recombination dynamics in MQW LEDs, which more

comprehensively takes both localized exciton

recombination (LER) and free carrier recombination

(FCR) into account. The obtained rates for LER, FCR

and nonradiative recombination show a clear picture

of recombination paths in a commercial blue MQW

LED wafer. They can be also used to calculate the

internal quantum efficiency without involving any

extra measurements or prerequisites. This model may

provide a universal solution to express the

complicated recombination dynamics in various kinds

of MQW LEDs.

Room-temperature continuous-wave operation of

green vertical-cavity surface-emitting lasers with a

curved mirror fabricated on {20−21} semi-polar GaN R & D Center, Sony Corporation, 4-14-1 Atsugi, Kanagawa,

Japan


https://doi.org/10.35848/1882-0786/ab7bc8

We demonstrate a room-temperature continuous-

wave operation of green vertical-cavity surface-

emitting laser (VCSEL) with a 20 μm long cavity

possessing a dielectric curved mirror formed over a

{20−21} semi-polar gallium nitride substrate. The

emission wavelength and the threshold current were

515 nm and 1.8 mA, respectively. We also confirmed

that white light is generated by overlaying three prime

colors of light, i.e. red, blue and green, emitted only

from VCSEL.

GaN-based vertical cavity surface emitting lasers

with lateral optical confinements and conducting

distributed Bragg reflectors Department of Materials Science, Meijo University, 1-501

Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan

Akasaki Research Center, Nagoya University, Furo-cho,

Nagoya 468-8603, Japan


https://doi.org/10.35848/1347-4065/ab6e05

We aimed to further improve performances of GaN-

based vertical cavity surface emitting lasers (VCSELs)

by applying a combination of conducting distributed

Bragg reflectors (DBRs) and lateral optical

confinement structures simultaneously, generally

used in GaAs-based VCSELs. Si-doped conducting

AlInN/GaN DBRs and buried SiO2 apertures were

adopted in the GaN-based VCSELs. By comparing the

VCSELs and micro LEDs to those with undoped non-

conducting DBRs, we found that lower device

resistances and more uniform lateral current

distributions were obtained with the conducting DBRs.

At the same time, the maximum light output power of

2.6 mW was observed from the VCSEL with the

conducting DBR while 4.4 mW was obtained from the

VCSEL with undoped DBR. Inferior characteristics of a

GaInN quantum well active region was found on the

Si-doped conducting DBR.

Effect of dislocation density on optical gain and

internal loss of AlGaN-based ultraviolet-B band lasers Department of Materials Science and Engineering Meijo

University, Nagoya 468-8502, Japan

Graduate School of Regional Innovation Studies, Mie

University, Tsu 514-8507, Japan

Asahi-Kasei Corporation, Fuji, Shizuoka 416-8501, Japan

Akasaki Research Center, Nagoya University, Nagoya 464-

8603, Japan


https://doi.org/10.35848/1882-0786/ab7caf

We investigated the dependence of the lasing

threshold power density, optical gain, and internal loss

on the dislocation density of an optically pumped

AlGaN-based ultraviolet-B band laser. Reducing the

https://doi.org/10.1088/1361-6641/ab73ed

https://doi.org/10.35848/1882-0786/ab7bc8

https://doi.org/10.35848/1347-4065/ab6e05

https://doi.org/10.35848/1882-0786/ab7caf


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dislocation density was found to not only increase the

optical gain by reducing the non-radiative

recombination centers but also reduce the internal

loss. Furthermore, this reduction in internal loss was

appropriately explained using an increased scattering

model based on an increase in the refractive index

fluctuations formed by the dislocations.

Investigation of coherency stress-induced phase

separation in AlN/AlxGa1-xN superlattices grown on

sapphire substrates Key Laboratory of Semiconductor Materials Science, and

Beijing Key Laboratory of Low Dimensional Semiconductor,

Materials and Devices, Institute of Semiconductors, Chinese

Academy of Sciences, P. O. Box 912, Beijing 100083,

People’s Republic of China

Center of Materials Science and Optoelectronics

Engineering, University of Chinese Academy of Sciences,

Beijing 101408, People’s Republic of China

Research Center of Electronic Manufacturing and Packaging

Integration, School of Power and Mechanical Engineering,

Wuhan University, Wuhan 430072, People’s Republic of

China

CrystEngComm

https://doi.org/10.1039/D0CE00147C

AlN/AlGaN superlattices (SLs) structure has been

proven promising for various applications including

deep ultraviolet light-emitting diodes. However, phase

separation in AlGaN of SLs leads to undesirable

changes in the optical and electrical properties of SL-

based devices. Herein, we investigate the influence of

the pulse duration on the compositional structure and

surface morphology of the upper AlGaN layer of

AlN/AlGaN SLs, grown on CVD-deposited single crystal

AlN template/sapphire substrate by pulsed metal-

organic chemical vapor deposition (MOCVD). Spectral

transmittance measurements reveal that phase

separation happened in the AlxGa1-xN layer of SLs

with inhomogeneous distribution of the aluminum

composition. The coherency stress and strain profiles

of AlN/AlGaN SLs were evaluated by finite element

simulations. High compressive stress in the upper

AlxGa1-xN layer and tensile stress in the underlying

AlN layer were observed for the SLs with a long pulse

duration. This increased stress in SLs facilitates the

exclusion of aluminum atoms, thus leading to the

apparent phase separation in the upper AlxGa1-xN

layer of SLs. Additionally, the effect of the shear strain

component at the interfaces on the piezoelectric

polarization of epitaxial layers was also discussed. This

study paves the avenue for preventing the phase

separation during the AlN/AlGaN SLs growth by

controlling the pulse mode configuration, thereby

offering new perspectives for the growth of high-

quality AlGaN epitaxial layers targeted for practical

applications.

In situ fabrication of Al surface plasmon

nanoparticles by metal–organic chemical vapor

deposition for enhanced performance of AlGaN deep

ultraviolet detectors State Key Laboratory of Luminescence and Applications,

Changchun Institute of Optics, Fine Mechanics and Physics,

Chinese Academy of Sciences, Changchun 130033, People's

Republic of China

Center of Materials Science and Optoelectronics

Engineering, University of Chinese Academy of Sciences,

Beijing 100049, People's Republic of China

College of Materials Science and Engineering, Shenzhen

University, Shenzhen 518071, People's Republic of China

Key Laboratory of Advanced Structural Materials, Ministry

of Education, Changchun University of Technology,

Changchun 130012, People's Republic of China

Nanoscale Advances

https://doi.org/10.1039/D0NA00022A

Al nanoparticles (NPs) have been proven to be the

efficient choice for plasmon enhanced AlGaN-based

ultraviolet (UV) photodetectors. Previous studies have

mainly been focused on the ex situ preparation of Al

NPs, but the in situ growth of Al NPs is more desired.

In this work, we predict the feasibility for in situ

growth of Al surface plasmon NPs on AlGaN-based UV

photodetectors by first-principles calculations, and

realized it experimentally by metal–organic chemical

vapor deposition. For metal–semiconductor–metal

type AlGaN-based photodetectors with in situ grown

Al surface plasmons, the peak of responsivity was at

288 nm, enhanced 9 times more than that without Al

NPs at 10 V bias. The in situ growth method of Al NPs

in the present work provides an efficient method for

improving the performance of AlGaN-based UV

photoelectric devices.

https://doi.org/10.1039/D0CE00147C

https://doi.org/10.1039/D0NA00022A


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Anisotropic properties of pipe-GaN distributed Bragg

reflectors Department of Materials Science and Engineering,

Innovation and Development Center of Sustainable

Agriculture, Research Center for Sustainable Energy and

Nanotechnology, National Chung Hsing University,

Taichung, 145 Xingda Rd., South Dist., Taichung 402, Taiwan

Department of Applied Materials and Optoelectronic

Engineering, National Chi Nan University, No.1, University

Rd., Puli Township, Nantou 545, Taiwan

Department of Chemical Engineering, Feng Chia University,

Seatwen, Taichung 407, Taiwan

Department of Electrical Engineering, Yale University, 15

Prospect St, New Haven, Connecticut, USA

Nanoscale Advances

https://doi.org/10.1039/C9NA00743A

We report here a simple and robust process to convert

periodic Si-doped GaN/undoped-GaN epitaxial layers

into a porous-GaN/u-GaN distributed Bragg reflector

(DBR) structure and demonstrate its material

properties in a high-reflectance epitaxial reflector.

Directional pipe-GaN layers with anisotropic optical

properties were formed from n+-GaN : Si layers in a

stacked structure through a lateral and doping-

selective electrochemical etching process. Central

wavelengths of the polarized reflectance spectra were

measured to be 473 nm and 457 nm for the pipe-GaN

reflector when the direction of the linear polarizer was

along and perpendicular to the pipe-GaN structure.

The DBR reflector with directional pipe-GaN layers has

the potential for a high efficiency polarized light

source and vertical cavity surface emitting laser

applications.

High doping efficiency in p-type Al-rich AlGaN by

modifying Mg doping planes State Key Laboratory of Optoelectronic Materials and

Technologies, School of Electronics and Information

Technology, Sun yat-sen University, Guangzhou 510275,

People’s Republic of China

Materials Advances

https://doi.org/10.1039/D0MA00026D

High doping efficiency of Mg dopant in Al-rich AlGaN

is highly desired for the AlGaN based deep ultraviolet

optoelectronics. In this work, the Mg doping planes

were modified by the pulsed group-III source,

according to the first-principles calculation results on

the Mg substituting Al or Ga on the surface and in the

bulk of Ai-rich AlGaN. The Mg-delta-doped AlxGa1-xN

(x~0.42) layer, using pulsed Ga source to modify the

doping planes, exhibits a very high hole concentration

of 8.3 × 1018 cm-3, which is 67% higher than that of

the reference one. A record doping efficiency of 51.9%

was achieved and the consequent resistivity is as low

as 0.51 Ω·cm. It was found that the Mg incorporation

was significantly enhanced and the acceptor activation

energy (EA) was substantially reduced, contributing to

the high doping efficiency. The improved

incorporation is attributed to the enhanced Mg

substitution for Al at the doping planes and the

increased substitution for Ga in the bulk by the

modification, whereas the decreased EA is ascribed to

the enlarged valence-band bending. This method

provides a simple and effective way to realize efficient

p-type doping of Al-rich AlGaN.

Multi-wavelength light emission from InGaN

nanowires on pyramid-textured Si (100) substrate

grown by stationary plasma-assisted molecular beam

epitaxy Guangdong Provincial Key Laboratory of Optical

Information Materials and Technology, South China

Academy of Advanced Optoelectronics, South China Normal

University, Guangzhou 510006, People’s Republic of China

National Center for International Research on Green

Optoelectronics, South China Normal University,

Guangzhou 510006, People’s Republic of China

Academy of Shenzhen Guohua Optoelectronics, Shenzhen

518110, People’s Republic of China

Research Institute for Soft Matter and Biomimetics, Fujian

Provincial Key Laboratory for Soft Functional Materials

Research, Department of Physics, Xiamen University,

Xiamen 361005, China

Nanoscale

https://doi.org/10.1039/D0NR00071J

We demonstrate multi-wavelength light emission

from InGaN nanowires (NWs) monolithically grown on

pyramid-textured Si (100) substrates by plasma

assisted molecular beam epitaxy (PA-MBE) at

stationary conditions. Taking advantage of the highly

unidirectional source materials beam fluxes, the In

content of the NWs is tuned on the different pyramid

facets due to varied incidence angle. This is confirmed

by distinct NW morphologies observed by scanning

https://doi.org/10.1039/C9NA00743A

https://doi.org/10.1039/D0MA00026D

https://doi.org/10.1039/D0NR00071J


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electron microscopy (SEM) and by energy-dispersive

X-ray (EDX) element mapping. Photoluminescence

(PL) and cathodoluminescence (CL) reveal multiple

lines originating from InGaN NWs on the different

pyramid facets. The anomalous temperature

dependence of the emission wavelength results from

carrier redistribution between localized or confined

states, spontaneously formed within the NWs due to

composition fluctuations, verified by high-resolution

EDX element analysis. First-principles calculations

show that the pyramid facet edges act as a barrier for

atom migration and enhance atom incorporation. This

leads to uniform composition within the facets for not

too high growth temperature, consistent with the

SEM, EDX and CL results. At elevated temperature,

InGaN decomposition and In desorption is enhanced

on facets with low growth rate, accompanied by Ga

inter-facet migration, leading to non-uniform

composition over the Ga migration length which is

deduced to around 580 nm. Our study presents a

method for the fabrication of multi-wavelength light

sources by highly unidirectional MBE on textured Si

substrates towards color temperature tunable solid-

state lighting and RGB light-emitting diode (LED)

displays

Over 10 Gbps VLC for Long-Distance Applications

Using a GaN-Based Series-Biased Micro-LED Array Department of Physics, Institute of Photonics, University of

Strathclyde, Glasgow, G1 1RD, U.K.

Li–Fi Research and Development Centre, Institute for Digital

Communications, The University of Edinburgh, Edinburgh,

U.K.

IEEE Photonics Technology Letters

https://doi.org/10.1109/LPT.2020.2981827

By employing a GaN-based series-biased micro-light

emitting diode (μ-LED) array and orthogonal

frequency division multiplexing modulation format, a

high-speed free-space visible light communication

system for long-distance applications has been

demonstrated. The blue series-biased μ LED array,

which consists of 3×3 , 20 μm -diameter μ LED

elements, presents promising performance with an

optical power and −6dB electrical modulation

bandwidth of over 10 mW and 980 MHz, respectively.

Record data transmission rates have been successfully

achieved at different free-space distances. Within 5 m

transmission distances, over 10 Gbps data rates at the

forward error correction (FEC) floor of 3.8×10−3 are

accomplished. Extending the transmission distances to

20 m, the data rates are maintained at the Gbps level

at the FEC floor.

Ultrafast UV AlGaN Metal–Semiconductor–Metal

Photodetector With a Response Time Below 25 ps Laboratory for Laser Energetics, University of Rochester,

Rochester, NY, USA

IEEE Journal of Quantum Electronics

https://doi.org/10.1109/JQE.2020.2981043

Aluminum-gallium-nitride photodetectors were

successfully fabricated with micrometer-scale metal–

semiconductor–metal structures and tested with

ultrafast, UV laser pulses. The measurements were

done with single-shot oscilloscopes. Pulse-broadening

effects caused by the measurement system were

systematically evaluated and reduced to resolve the

intrinsic response time of the detector. The best-

performing devices showed a response time of below

25 ps and dark currents below 20 pA. The devices

showed linear response with the bias voltage and the

laser energy.

Efficient Carrier Transport for AlGaN-Based Deep-UV

LEDs With Graded Superlattice p-AlGaN Optoelectronics and MOEMS Group, CSIR-CEERI, Pilani,

India

IEEE Transactions on Electron Devices

https://doi.org/10.1109/TED.2020.2974408

In this article, a novel graded superlattice (SL) p-AlGaN

structure for deep ultraviolet light-emitting diode

(DUV LED) capable of emitting 273 nm has been

studied. It is observed that the output power in the

case of graded SL p-AlGaN LED structure (GSLED) is

significantly high (7.68-fold higher, at the current

density of 200 A/cm 2 ) compared with a conventional

structure. Moreover, noticeable improvements in the

maximum value of external quantum efficiency, as

well as the efficiency droop, are achieved with the

modified structures. The abrupt potential barrier

height in conventional DUV LED (CLED) obstructs the

hole injection inside the quantum well region. On the

contrary, smoother band variation in GSLED prevents

https://doi.org/10.1109/LPT.2020.2981827

https://doi.org/10.1109/JQE.2020.2981043

https://doi.org/10.1109/TED.2020.2974408


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potential barrier height of hole and causes ease in the

flow of hole into the quantum well (QW) region. Also,

the electron concentration in the multiple-quantum-

well (MQW) region for GSLED is increased by around

100% due to the reduced leakage of electrons toward

the p-region.

Analysis of Factors Affecting Optical Performance of

GaN-Based Micro-LEDs with Quantum Dots Films School of Electric Communication Technology, Shenzhen

Institute of Information Technology, Shenzhen 518072,

China

School of Power & Mechanical Engineering, Wuhan

University, Wuhan 430072, China

Shenzhen Key Lab for Advanced Quantum Dot Display and

Lighting, Department of Electrical & Electronic Engineering,

Southern University of Science &Technology, Shenzhen

518055, China

Academy for Advanced Interdisciplinary Studies, Southern

University of Science and Technology, Shenzhen 518055,

China

Crystals

https://doi.org/10.3390/cryst10030203

Optical performance in terms of light efficiency, color

crosstalk and ambient contrast ratio were analyzed for

blue GaN-based micro-light emitting diodes (micro-

LEDs) combined with red/green quantum dots (QDs)-

polymethyl methacrylate (PMMA) films. The thickness

and mass ratio of QDs films are two critical factors in

affecting the performance of micro-LEDs. Firstly, the

precise optical modeling of QDs-PMMA films is

established based on the double integrating sphere

(DIS) testing system and inverse adding doubling

algorithm (IADA) theory. Red and green QDs-PMMA

films are composed of ZnCdSe/ZnS QDs and green

ZnCdSeS/ZnS QDs, respectively. The fundamental

optical parameters of QDs-PMMA films, including

scattering, absorption and anisotropy coefficients, are

obtained successfully. Secondly, based on these

optical parameters, the Monte Carlo ray tracing

method is applied to analyze the effect of a QDs-

PMMA film’s thickness and mass ratio on the optical

performance of micro-LEDs. Results reveal that the

light efficiency first increases and then decreases with

the increase of a QDs film's thickness or mass ratio,

owing to the scattering characteristics of QDs.

Different from the variation tendencies of light

efficiency, the crosstalk between adjacent pixels

increases as the QDs-PMMA film's thickness or mass

ratio increases, and the ambient contrast ratio is kept

stable when the thickness increases. The mass ratio

variation of QDs film can change the optical

performance of micro-LEDs more effectively than

thickness, which demonstrates that mass ratio is a

more important factor affecting the optical

performance of micro-LEDs.

https://doi.org/10.3390/cryst10030203


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ELECTRONICS Group leader: Farid Medjoub (CNRS-IEMN)

Information selected by Farid Medjoub (CNRS-IEMN), Jean-Claude Dejaeger (CNRS-IEMN) and Yvon Cordier (CNRS-CRHEA)

Improved DC-RF dispersion with epitaxial passivation

for high linearity graded AlGaN channel field effect

transistors Department of Electrical and Computer Engineering, The

Ohio State University, Columbus, OH 43210, United States

of America

Qorvo, Inc., Richardson, TX 75081, United States of America


https://doi.org/10.35848/1882-0786/ab7480

We demonstrate DC-RF dispersion-free graded AlGaN

channel transistor with an epitaxial passivation. The

device used for this experiment was an AlGaN channel

polarization-graded field effect transistor (PolFET)

with Al-composition grading from 0% to 30%. We were

able to reduce the dispersion to almost zero current

collapse and zero knee-walkout for pulsed I–V up to 30

V drain quiescent bias condition with epitaxial

passivation, compared to 8 V knee-walkout and 25%

current collapse for PolFETs with traditional PECVD

SiNx for the same measure conditions. We also report

large signal power density and two-tone linearity for

these devices up to X-band frequencies.

Improved DC performance and current stability of

ultrathin-Al2O3/InAlN/GaN MOS-HEMTs with post-

metallization-annealing process Graduate School of Information and Science Technology

and Research Center for Integrated Quantum Electronic

(RCIQE), Hokkaido University, Sapporo 060-8628, Japan

Fujitsu Laboratories Ltd, Atsugi, Kanagawa 243-0197, Japan


https://doi.org/10.1088/1361-6641/ab708c

We evaluated the effect of the post-metallization-

annealing (PMA) process on drain current stability of

InAlN/GaN metal-oxide-semiconductor high electron

mobility transistors (MOS-HEMTs) with a 1 nm thick

ultrathin-Al2O3, by focusing on the Al2O3/InAlN

interface properties. We clarified that the

improvement in DC characteristics (drain current, on-

state resistance, and transconductance) with PMA was

attributed to the decrease in sheet resistance (R sh),

and the current collapse evaluated by pulsed I–V

characteristics was effectively suppressed, because of

the reduction in the electronic states at the

Al2O3/InAlN interface. Transmission electron

microscope analysis of the Al2O3/InAlN structures

revealed that the bond disorder at the Al2O3/InAlN

interface was significantly recovered after PMA. It is

considered that the PMA process is effective in

enhancing the relaxation of dangling bonds and/or

point defects at the Al2O3/InAlN interface, leading to

the improved DC performance and current stability for

the Al2O3/InAlN/GaN MOS-HEMTs.

The influence of AlN nucleation layer on RF

transmission loss of GaN buffer on high resistivity Si

(111) substrate Department of Materials Science and Engineering, National

Chiao Tung University, University Rd. 1001, Hsinchu 30010,

Taiwan

IMEC, Kapeldreef 75, Leuven B-3001, Belgium


https://doi.org/10.1088/1361-6641/ab7149

A sufficiently low transmission loss in radio frequency

(RF) is one of the critical requirements for GaN-on-Si

RF devices to achieve high performance. We have

systematically studied the mechanism and effect of

the AlN nucleation layer on the RF loss of the GaN-on-

Si device buffer stack. Our results show that the RF loss

is strongly influenced by the growth parameters of the

AlN nucleation layer during epitaxial process. It is

observed that the AlN nucleation layer grown at a low

thermal budget with a low density of deep surface pits

can efficiently reduce the AlN/Si interface loss by

suppressing the conductive channel at AlN/Si interface

which is governed largely by the thermal diffusion of

Al and Ga into the Si substrate. By optimizing the

growth process of the AlN nucleation layer, the RF loss

of the GaN-on-Si device buffer can be dramatically

reduced by up to ~40%.

https://doi.org/10.35848/1882-0786/ab7480

https://doi.org/10.1088/1361-6641/ab708c

https://doi.org/10.1088/1361-6641/ab7149


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A modified analytical model for AlGaN/GaN FinFETs

I – V characteristics Department of Electrical Engineering, Capital University of

Science and Technology, Islamabad, Pakistan


https://doi.org/10.1088/1361-6641/ab6101

In this paper, a high electron mobility transistor's

(HEMT) analytical model, which is based on the

vertical operation of Schottky barrier gate, has been

modified for the I−V characteristics of rectangular

shaped AlGaN/GaN FinFETs having three-sided

Schottky barrier gate operation. The proposed model

includes the effect of the tri-gate structure on sheet

carrier concentration (n s ) of the device. A three

dimensional Poisson equation is solved keeping in

view, the device geometry and applied potentials, to

get the effect of the side gates on n s . It is

demonstrated that n s of a FinFET depletes relatively

faster than its HEMT counterpart due to the extra

fields caused by the side gates. Knowing bias

dependent n s , FinFET I−V expressions are developed

and tested on AlGaN/GaN FinFETs of varying gate

lengths (L g = 0.4 – 1.0 μm) for the above threshold

regime. A good agreement between the experimental

and modeled characteristics is observed, which

demonstrates the validity of the proposed model in

predicting the DC characteristics of tri-gate

AlGaN/GaN FinFETs.

Failure analysis of normally-off GaN HEMTs under

avalanche conditions University of Valencia, Department of Electronic

Engineering, E-46100 Burjassot, Spain

Fraunhofer Institute for Integrated Systems and Device

Technology, D-91058 Erlangen, Germany


https://doi.org/10.1088/1361-6641/ab6bad

Gallium nitride (GaN) high electron-mobility

transistors (HEMTs) are promising devices in the

power electronics field owing to their wide bandgap

(WBG). However, all the potential advantages

provided by their WBG require reliability

improvement. In industrial applications, robustness is

one of the main factors considered by circuit

designers. This study focuses on the observation of the

degradation behavior of the main waveforms of

unclamped inductive-switching (UIS) test circuits of

two different commercial GaN HEMT structures. The

relevance of this study lies in the potential applications

of these devices to high-voltage applications and

automotive systems where they are subjected to

many UIS events over their lifetime. This study shows

that avalanche does not occur on these devices;

therefore, the breakdown is caused by the high

voltage. A deeper analysis of the breakdown

mechanism is achieved using a curve/tracer analyzer,

lock-in thermography, and focused ion beam. These

experiments reveal that impact ionization is the main

failure mechanism that causes breakdown in both

structures.

Growth and Characterization of Nitrogen‐Polar

AlGaN/AlN Heterostructure for High‐Electron‐

Mobility Transistor Graduate School of Sciences and Technology for Innovation,

Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi,

755-8611 Japan

Materials Research & Development Laboratory, Japan Fine

Ceramics Center (JFCC), 2-4-1 Mutsuno, Atsuta, Nagoya,

Aichi, 456-0023 Japan

physica status solidi b

https://doi.org/10.1002/pssb.201900589

A nitrogen‐polar (N‐polar) AlGaN/AlN high‐electron‐

mobility transistor (HEMT) is proposed, and the

generation of a 2D electron gas (2DEG) is simulated.

The band diagram of N‐polar (Al)GaN/AlN shows the

generation of the 2DEG, whereas that of the

conventional metal‐polar (Al)GaN/AlN structure

shows the generation of a 2D hole gas. Furthermore,

the concentration of the 2DEG is considerably high

even when the (Al)GaN layer is as thin as a few

nanometers. N‐polar AlGaN/AlN is grown on sapphire

substrates with a misorientation angle of 2°;

furthermore, atomic force microscope measurements

in a range of 5 × 5 μm2 demonstrate that the root‐

mean‐square value obtained from atomic force

microscopy of N‐polar AlGaN is approximately 0.7 nm.

N‐polar AlGaN layers with a thickness of

approximately 40–60 nm with more than 50% Al

content are almost coherently grown on the N‐polar

AlN layer with a thickness of approximately 400 nm.

https://doi.org/10.1088/1361-6641/ab6101

https://doi.org/10.1088/1361-6641/ab6bad

https://doi.org/10.1002/pssb.201900589


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Improved conduction in GaN Schottky junctions with

HfO2 passivation layers through post-deposition

annealing Department of Electronic and Electrical Convergence

Engineering, Hongik University, Sejong 30016, Republic of

Korea


https://doi.org/10.35848/1347-4065/ab71d6

The conduction in GaN Schottky junctions with HfO2

passivation layers can be improved by post-deposition

annealing (PDA). Surface defects and ionic states of

Ga-polar GaN removed by PDA lead to the formation

of downward bend banding with a positive surface

polarity. X-ray photoelectron spectroscopy is utilized

to assess the effects of PDA on the atomic composition

and surface polarity changes at the HfO2/GaN

interface and GaN surface. The leakage current level

and ideality factor of the GaN Schottky junctions

improved from 4.73 × 10−6 A cm−2 to 8.21 × 10−8 A

cm−2 and from 1.47 to 1.14, respectively. With the

application of PDA, the flow of leakage current

through the Schottky metal area reduced as the

surface defect states were removed.

GaN-on-diamond technology platform: Bonding-free

membrane manufacturing process School of Engineering, University of Glasgow, Glasgow G12

8LT, United Kingdom

School of Engineering, Cardiff University, Cardiff CF24 3AA,

United Kingdom

Center for Device Thermography and Reliability (CDTR), H.

H. Wills Physics Laboratory, University of Bristol, Bristol BS8

1TL, United Kingdom

Department of Materials Science and Metallurgy, University

of Cambridge, 27 Charles Babbage Road, Cambridge CB3

0FS, United Kingdom

AIP Advances

https://doi.org/10.1063/1.5129229

GaN-on-diamond samples were demonstrated using a

membrane-based technology. This was achieved by

selective area Si substrate removal of areas of up to 1

cm × 1 cm from a GaN-on-Si wafer, followed by direct

growth of a polycrystalline diamond using microwave

plasma chemical vapor deposition on etch exposed N-

polar AlN epitaxial nucleation layers. Atomic force

microscopy and transmission electron microscopy

were used to confirm the formation of high quality,

void-free AlN/diamond interfaces. The bond between

the III-nitride layers and the diamond was validated by

strain measurements of the GaN buffer layer.

Demonstration of this technology platform is an

important step forward for the creation of next

generation high power electronic devices.

The Origin and Influence of Compensatory Current in

AlGaN/GaN HEMT Type Heterostructures with Two

Conducting Channels on the Hall Measurements The Faculty of Microsystem Electronics and Photonics,

Wroclaw University of Science and Technology,

Janiszewskiego 11/17, 50‐372 Wroclaw, Poland

physica status solidi a


The second conducting channel was created in

AlGaN/GaN type HEMT (High Electron Mobility

Transistors) heterostructures deposited by the

MOVPE (Metal Organic Vapour Phase Epitaxy) process

in which the pressure was change during the growth

of buffer GaN layer to ensure its high‐resistivity. It was

stated that second, parasitic, conducting channel was

induced as a result of the non‐intentional doping that

occurred at the GaN‐GaN interface. The Hall

measurements in wide range of temperatures, from

77 K to 420 K, was used to obtain the sheet resistivity,

sheet carrier concentration and electron mobility of

the heterostructures. The theoretical model of the

multilayer transport in AlGaN/GaN type HEMT

heterostructures, based on equivalent circuit allow for

estimation of compensatory current. Based on the

theoretical model the correction map for the Hall

measurement of the samples with two conducting

channels was evaluated. The measured electron

mobility μmeas obtained from the Hall measurement

was applied for determination of the 2DEG (two‐

dimensional electron gas) mobility μ1 of the samples

with two conducing channels using the equation μ1 =

αμmeas. It was observed that the appropriate

correction coefficient α depends on second channel

parameters i.e. the sheet resistance and mobility of

the second conducing channel.

https://doi.org/10.35848/1347-4065/ab71d6

https://doi.org/10.1063/1.5129229



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GaN power switches on the rise: Demonstrated

benefits and unrealized potentials Department of Electrical Engineering, The Pennsylvania

State University, University Park, Pennsylvania, 16802, USA


https://doi.org/10.1063/1.5133718

As a wide bandgap semiconductor with high

breakdown field, GaN is expected to outperform the

incumbent Si technology for power switching

applications. Advances in GaN epitaxial growth, device

technology, and circuit implementations have resulted

in high-performing power switches based on the GaN

high electron mobility transistor (HEMT) structure.

Demonstrated system benefits have validated the real

value of GaN power switching technology. However,

the full potential of GaN power switching technology

is still far from being exploited. Various factors,

including the size of electrodes and wiring, non-

optimal E-field shaping, and substrate capacitive

coupling, are limiting the performance of GaN HEMT

power switches. Emerging device structures, such as,

vertical transistors and multichannel superjunction

transistors, have the potential to overcome some of

those limitations, thereby bringing the performance

benefits of the GaN power switching technology to a

new level. Understanding the underlying physics is

important to the success of the emerging device

structures.

Interface charge engineering in down-scaled AlGaN

(<6 nm)/GaN heterostructure for fabrication of GaN-

based power HEMTs and MIS-HEMTs University of Chinese Academy of Sciences, 100049 Beijing,

China

Institute of Microelectronics of Chinese Academy of

Sciences, 100029 Beijing, China

School of Physics, Peking University, 100871 Beijing, China


https://doi.org/10.1063/1.5134886

The physical mechanism for recovery of 2D electron

gas (2DEG) in down-scaled AlGaN/GaN

heterostructures with SiNx layers grown by low-

pressure chemical vapor deposition (LPCVD) was

investigated by means of Hall-effect characterization,

scanning Kelvin probe microscopy (SKPM), and self-

consistent Poisson–Schrödinger calculations.

Observations using SKPM show that the surface

potential of the AlGaN/GaN heterostructure remained

nearly unchanged (∼1.08 eV) as the thickness of the

AlGaN barrier was reduced from 18.5 to 5.5 nm and

likely originated from the surface pinning effect. This

led to a significant depletion of 2DEG from 9.60 × 1012

to 1.53 × 1012 cm−2, as determined by Hall

measurements, toward a normally OFF 2DEG channel.

Based on a consistent solution of the Schrödinger–

Poisson equations and analytical simulations,

approximately 3.50 × 1013 cm−2 of positive fixed

charges were confirmed to be induced by a 20-nm

LPCVD-SiNx passivation over the AlGaN/GaN

heterostructures. The interface charge exerted a

strong modulation of band bending in the down-

scaled AlGaN/GaN heterostructure, contributing to

the efficient recovery of 2DEG charge density

(∼1.63 × 1013 cm−2). E-mode ultrathin-barrier

AlGaN/GaN metal–insulator–semiconductor high-

electron-mobility transistors with a low ON-resistance

(RON), high ON/OFF current ratio, and steep

subthreshold slope were implemented using LPCVD-

SiNx passivation.

A unified model for vertical doped and polarized

superjunction GaN devices State Key Laboratory of Electronic Thin Films and Integrated

Devices, University of Electronic Science and Technology of

China, Chengdu 610054, China

The Edward S. Rogers, Sr., Department of Electrical and

Computer Engineering, University of Toronto, Toronto,

Ontario M5S 3G4, Canada


https://doi.org/10.1063/1.5142855

A unified model is proposed to characterize the

breakdown voltage (BV) and specific on-resistance

(Ron,sp) for vertical doped superjunction (d-SJ) and

polarized superjunction (p-SJ) GaN power devices. This

study is based on the recently published

compensated-pillar superjunction (cp-SJ) structure. A

two-dimensional model for the electric field is

analytically formulated using the Green's function

method. Numerical calculations and TCAD simulations

demonstrate that, for a given pillar depth, the p-SJ

device has a lower BV than the d-SJ device with a wide

pillar width. However, when the pillar width is less

https://doi.org/10.1063/1.5133718

https://doi.org/10.1063/1.5134886

https://doi.org/10.1063/1.5142855


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than 200 nm, both devices demonstrate a maximum

BV that is close to the intrinsic structure. The Ron,sp

unified model for the cp-SJ device, taking into account

the junction field-effect transistor (JFET) effect in the

drift region, also demonstrates that the p-SJ device has

a superior Ron,sp over the d-SJ device. Considering the

recently published impact ionization coefficients, the

BV of the p-SJ device is analytically modeled as a

function of the pillar depth. Finally, by applying the

Lambert W-function, an exact closed-form

relationship between Ron,sp and BV is presented.

Superior growth, yield, repeatability, and switching

performance in GaN-based resonant tunneling

diodes NAS-NRC Postdoctoral Research Fellow Residing, U.S. Naval

Research Laboratory, Washington DC 20375, USA

U.S. Naval Research Laboratory, Washington DC 20375, USA

Department of Electrical and Computer Engineering, The

Ohio State University, Columbus, Ohio 43210, USA

Departments of Physics and Electrical Engineering, Wright

State University, Dayton, Ohio 45435, USA

Jacobs Engineering Group, Hanover, Maryland 21076, USA


https://doi.org/10.1063/1.5139219

We report the direct measurement of record fast

switching speeds in GaN/AlN resonant tunneling

diodes (RTDs). The devices, grown by plasma-assisted

molecular-beam epitaxy, displayed three repeatable

negative differential resistance (NDR) regions below a

bias of +6 V. A room temperature peak-to-valley

current ratio (PVCR) > 2 was observed, which

represents a marked improvement over recent

reports. Measurements carried out on hundreds of

devices, of varying sizes, revealed a yield of ∼90%.

Repeatability measurements consisting of 3000

sweeps resulted in a standard deviation, relative to

the mean, of < 0.1%. Temperature dependent

measurements combined with non-equilibrium

Green's function based quantum transport

simulations suggest the presence of both three-

dimensional (3D) and two-dimensional (2D) emitters,

giving rise to three NDR regions. Finally, a valley

current density vs perimeter-to-area-ratio study

indicates the presence of a surface leakage current

mechanism, which reduces the PVCR.

Modulation of the two-dimensional electron gas

channel in flexible AlGaN/GaN high-electron-

mobility transistors by mechanical bending Department of Mechanical Engineering, University of

Houston, Houston, Texas 77204-4006, USA

Texas Center for Superconductivity at UH (TcSUH) and

Advanced Manufacturing Institute (AMI), University of

Houston, Houston, Texas 77204, USA

Materials Science and Engineering Program, University of

Houston, Houston, Texas 77204, USA

Department of Mechanical Engineering, The Pennsylvania

State University, University Park, Pennsylvania 16802, USA

Korea Photonics Technology Institute (KOPTI), Gwangju

61007, South Korea

Department of Photonic Engineering, Chosun University,

Gwangju 61452, South Korea

Advanced Semiconductor Laboratory, King Abdullah

University of Science and Technology (KAUST), Thuwal

23955, Saudi Arabia


https://doi.org/10.1063/1.5142546

We investigate the effect of strain on the two-

dimensional electron gas (2DEG) channel in a flexible

Al0.25Ga0.75N/GaN high-electron-mobility transistor

(HEMT) by mechanical bending to prove the concept

of active polarization engineering to create

multifunctional electronic and photonic devices made

of flexible group III-nitride thin films. The flexible

HEMTs are fabricated by a layer-transfer process and

integrated with a 150-μm-thick Cu film. The strain

values are estimated from high-resolution x-ray

diffraction and Raman spectroscopy in 4-cm bend-

down and −4-cm bend-up test conditions. The strain-

induced piezoelectric polarization can alter the charge

density of the 2DEG in the channel at the AlGaN/GaN

interface and thus modify the output characteristics of

the flexible HEMTs. Accordingly, output characteristics

show an increase in output current by 3.4% in the

bend-down condition and a decrease by 4.3% in the

bend-up condition. Transfer characteristics show a

shift of threshold voltage, which also supports the

2DEG channel modulation during bending.

Computational simulation based on the same

structure confirms the same current modulation effect

and threshold voltage shift. Furthermore, the

electrical characteristics of the flexible HEMTs show a

repeatable dependence on the strain effect, which

https://doi.org/10.1063/1.5139219

https://doi.org/10.1063/1.5142546


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offers potential for electro-mechanical device

applications.

AlGaN/GaN high electron mobility transistors on

diamond substrate obtained through aluminum

nitride bonding technology Institut d’Electronique de Microélectronique et de

Nanotechnologie (IEMN), UMR 8520, Université de Lille,

Avenue Poincaré, BP60069, 59652 Villeneuve d’Ascq Cedex,

France

Laboratoire d’Analyse et d’Architecture des Systèmes

(LAAS), 7 Avenue du Colonel Roche, 31031 Toulouse, France

CRHEA-CNRS, Centre de Recherche sur l'Hétéro-Epitaxie et

ses Applications, Rue Bernard Grégory, 06560 Valbonne,

France

Journal of Vacuum Science & Technology B

https://doi.org/10.1116/1.5143418

Transfer technology is now becoming very attractive

not only for new technologies such as flexible

technology but also for solid state technologies when

performances are limited by technological barriers

that have to be overcome. In this last context, the

transfer of high electron mobility transistors (HEMTs)

on diamond substrates represents an opportunity to

improve the thermal dissipation when the device

operates at high radio frequency power levels. Up to

now, the technological process for the transfer of

these transistors is not detailed in the literature. In this

article, the first demonstration of AlGaN/GaN HEMTs

on diamond substrates by transfer technology

obtained through sputtered aluminum nitride (AlN)

layers bonding at low temperature is reported.

Devices are first fabricated on AlGaN/GaN epilayers

grown on silicon (Si) substrates. Afterward,

AlGaN/GaN thin films with devices are released from

the Si growth substrate and transferred at 160 °C onto

a diamond substrate thanks to an AlN bonding layer. A

full description of the transfer technology and all the

technological limits and risks are presented. The

transferred device provides a maximum DC drain

current density IDS Max of 690 mA mm−1 at VGS = 0 V.

Furthermore, a cutoff frequency fT of 85 GHz and a

maximum oscillation frequency fMAX of 106 GHz are

extracted from S-parameter measurements.

Optimization of Mesa Etch for a Quasi-Vertical GaN

Schottky Barrier Diode (SBD) by Inductively Coupled

Plasma (ICP) and Device Characteristics Shenzhen Institute of Wide-bandgap Semiconductors,

Shenzhen 518000, China

Institute of Microelectronics, Chinese Academy of Sciences,

Beijing 100029, China

Department of Microelectronics, Delft University of

Technology, Delft 2628 CD, The Netherlands

Nanomaterials

https://doi.org/10.3390/nano10040657

The optimization of mesa etch for a quasi-vertical

gallium nitride (GaN) Schottky barrier diode (SBD) by

inductively coupled plasma (ICP) etching was

comprehensively investigated in this work, including

selection of the etching mask, ICP power, radio

frequency (RF) power, ratio of mixed gas, flow rate,

and chamber pressure, etc. In particular, the

microtrench at the bottom corner of the mesa sidewall

was eliminated by a combination of ICP dry etching

and tetramethylammonium hydroxide (TMAH) wet

treatment. Finally, a highly anisotropic profile of the

mesa sidewall was realized by using the optimized

etch recipe, and a quasi-vertical GaN SBD was

demonstrated, achieving a low reverse current density

of 10−8 A/cm2 at −10 V.

Effects of Recessed-Gate Structure on AlGaN/GaN-

on-SiC MIS-HEMTs with Thin AlOxNy MIS Gate School of Electronic and Electrical Engineering, Hongik

University, Seoul 04066, Korea

Department of Electrical and Computer Engineering, Seoul

National University, Seoul 08826, Korea

Metamaterial Electronic Device Research Center, Hongik

University, Seoul 04066, Korea

Materials

https://doi.org/10.3390/ma13071538

This study investigated the effects of a thin aluminum

oxynitride (AlOxNy) gate insulator on the electrical

characteristics of AlGaN/GaN-on-SiC metal-insulator-

semiconductor high electron mobility transistors (MIS-

HEMTs). The fabricated AlGaN/GaN-on-SiC MIS-

HEMTs exhibited a significant reduction in gate

leakage and off-state drain currents in comparison

with the conventional Schottky-gate HEMTs, thus

enhancing the breakdown voltage. The effects of gate

https://doi.org/10.1116/1.5143418

https://doi.org/10.3390/nano10040657

https://doi.org/10.3390/ma13071538


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recess were also investigated while using recessed

MIS-HEMT configuration. The Johnson’s figures of

merit (= fT × BVgd) for the fabricated MIS-HEMTs were

found to be in the range of 5.57 to 10.76 THz·V, which

is the state-of-the-art values for GaN-based HEMTs

without a field plate. Various characterization

methods were used to investigate the quality of the

MIS and the recessed MIS interface.

Role of polarity in SiN on Al/GaN and the pathway to

stable contacts Adroit Materials, Inc., 2054 Kildaire Farm Rd., Cary NC

27518, United States of America

Department of Electrical and Computer Engineering, North

Carolina State University, Raleigh, NC 27695-7911, United

States of America

Department of Materials Science and Engineering, North

Carolina State University, Raleigh, NC 27695-7919, United

States of America


https://doi.org/10.1088/1361-6641/ab7775

Despite being the most widely used dielectric for

passivation of GaN-based lateral devices, amorphous

silicon-nitride still faces many stability challenges,

which arise from its complex bulk electronic and

interface properties on the polar (Al)GaN surfaces. In

this investigation, SiN has been applied as an ultra-thin

interlayer (~3–5 nm) in vertical contact structures on

Ga-polar and N-polar GaN templates to study the

metal–insulator–semiconductor- (MIS-) like system

and better understand the interaction between the

polar surface and its dielectric overlayer. We describe

the role of amphoteric ≡Si centers in SiN in passivating

and providing the polarization countercharge to

Al/GaN of different polarities. The consequent

requirements of the concentration profile of the

amphoteric defects and the corresponding chemical

profile of SiN is discussed. The importance of SiN

surface termination and their influence on the

interface potential on Al/GaN that determines device

performance and reliability is also shown. Finally, a

pathway to highly stable and reliable ohmic contacts

to n-type Ga-polar GaN without instabilities associated

with metal directly alloying with GaN as in the case of

traditional contacts is proposed.

Insight into gate dielectric reliability and stability of

SiO2/GaN MOS devices Graduate School of Engineering, Osaka University, Suita,

Osaka 565-0871, Japan


https://doi.org/10.35848/1347-4065/ab7fe6

Gate dielectric reliability and stability of SiO2/GaN

metal–oxide–semiconductor (MOS) capacitors were

systematically investigated by means of area-

dependent and time-dependent dielectric breakdown

(TDDB) characteristics. It was found that, although

high-temperature post-deposition annealing (PDA)

that causes Ga diffusion in SiO2 gate dielectrics has

only a minor impact on electrical properties of the

SiO2/GaN interfaces, PDA at temperatures above 800

°C severely degrades dielectric reliability and stability

of GaN MOS devices. Area dependences of time-zero

and TDDB characteristics revealed the formation of

local weak spots and generation of uniform charge

trapping sites throughout the gate oxides depending

on the PDA temperatures. Determinant factors for

dielectric reliability of SiO2/GaN gate stacks and

reasonable measures for improving their reliability

and stability are discussed on the basis of the

experimental findings.

Study on the effect of diamond layer on the

performance of double-channel AlGaN/GaN HEMTs Key Lab of Wide Bandgap Semiconductor Materials and

Devices, School of Microelectronics, Xidian University, Xi'an

710071, People's Republic of China

School of Mechano-electric Engineering, Xidian University,

Xi'an, 710071, People's Republic of China

National Key Laboratory of Application Specific Integrated

Circuit (ASIC), Hebei Semiconductor Research Institute,

Shijiazhuang 050051, People's Republic of China


https://doi.org/10.1088/1361-6641/ab7773

The thermal effect is an important reliability issue for

GaN-based devices. The impact of the diamond layer

on double-channel AlGaN/GaN HEMTs (DC-HEMTs) is

first investigated in this paper by Sentaurus TCAD

simulation. By utilizing the diamond layer, the lattice

temperature along the channel can be modulated and

becomes more even. The results show that the peak

lattice temperature can be reduced by 64 K when the

https://doi.org/10.1088/1361-6641/ab7775

https://doi.org/10.35848/1347-4065/ab7fe6

https://doi.org/10.1088/1361-6641/ab7773


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power dissipation increases to 46 W mm−1 in the DC-

HEMT with a diamond layer. A 1 μm thick diamond

layer is regarded as the optimized thickness when

considering the temperature reduction and cost. With

the help of the diamond layer, the saturated drain

current and transconductance of DC-HEMTs are

increased by 0.21 A mm−1 and 22 mS mm−1,

respectively. Meanwhile, peak f T and f max can be

enhanced by 4.7 GHz and 10.3 GHz, respectively.

These results show that diamond layers have great

potential in lattice temperature reduction and

performance and reliability improvement of DC-

HEMTs.

Delay analysis of high-electron mobility transistors

under high drain bias Infineon Technologies AG, Germany

Institute for Electronics Engineering, Friedrich-Alexander-

Universität Erlangen-Nürnberg, Germany


https://doi.org/10.1088/1361-6641/ab78f5

In this work, we present a new delay analysis of high-

electron-mobility transistors (HEMTs), in which we

show that the total intrinsic delay can be separated

into six distinct contributions. We distinguish between

delays caused by the capacitive coupling between

electrodes, the quasi-static charge distribution within

the device and a dynamic delay originating from on-

state charge flow. An analytical expression for the

dynamic delay is established in the form of a delay

density using a position dependent image charge

analysis. This delay density allows us to show

graphically the position dependence of the delay

contributions of mobile charge throughout the

depletion region. Furthermore, the dynamic delay is

separated into a component dependent on the length

of the gate electrode and a drain delay component

dependent on the drain voltage bias. The influence of

high drain bias on the delay components is

investigated with the aid of GaN HEMT device

simulations and measurements, showing the relative

importance of scaling the gate and the drain regions.

The RF delay analysis reported here is based upon the

definition of small-signal current gain and elucidates

the effect of position dependent mobile charge within

a HEMT, clarifying the requirements for device scaling.

High-frequency AlGaN/GaN T-gate HEMTs on

extreme low resistivity silicon substrates Institute of Electronics Engineering, National Tsing Hua

University, Hsinchu 30013, Taiwan

Innovation Technology Research Center, Global Wafers Co.

Ltd., Hsinchu 30013, Taiwan


https://doi.org/10.35848/1347-4065/ab70a5

The T-gate high frequency AlGaN/GaN high electron

mobility transistors (HEMTs) are demonstrated on an

8 inch extremely-low resistivity (ELR) silicon substrate

with a resistivity of ~2.5 mΩ cm to investigate the

potential of using the ELR Si substrate for RF

applications. The devices are also fabricated on the 60

Ω cm substrate for comparison. The 0.1 μm T-gate is

realized by e-beam lithography to improve the high

frequency characteristics of the devices. The short-

circuit current gain cutoff frequency (f T), the

maximum oscillation frequency (f max), and maximum

transconductance (g m,max) of 27 GHz, 71 GHz and

247 mS mm−1 can be achieved, respectively. The

obtained high frequency performance is among the

best reported to date for the GaN HEMTs on such low

resistivity silicon substrates.

Increasing threshold voltage and reducing leakage of

AlGaN/GaN HEMTs using dual-layer SiN x stressors School of Microelectronics, Southern University of Science

and Technology (SUSTech), Shenzhen 518055, People's

Republic of China

Department of Electronic and Computer Engineering, The

Hong Kong University of Science and Technology (HKUST),

Hong Kong, People's Republic of China

School of Engineering and Computer Science, Washington

State University, Vancouver, WA 98686, United States of

America

Department of Materials Engineering, The University of

British Columbia, Vancouver, BC V6T 1Z4, Canada

GaN Device Engineering Technology Research Center of

Guangdong, Shenzhen 518055, People's Republic of China

The Key Laboratory of the Third Generation Semi-

conductor, Shenzhen 518055, People's Republic of China


https://doi.org/10.1088/1361-6641/ab73ea

In this work, AlGaN/GaN HEMTs with dual-layer SiN x

stressors (composed of a low-stress layer and a high-

https://doi.org/10.1088/1361-6641/ab78f5

https://doi.org/10.35848/1347-4065/ab70a5

https://doi.org/10.1088/1361-6641/ab73ea


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stress layer) were investigated. The low-stress padding

layer solved the surface damage problem which was

caused during the deposition of the high-stress SiN x

and provided a good passivated interface. The HEMTs

with the dual-layer stressors showed a 1 V increase in

the threshold voltage (V th ) with comparable DC and

RF amplification performance to the baseline devices.

Moreover, the off-current (I off ) was shown to be

reduced by one to three orders of magnitude in the

strained devices. The reduction in the off-currents was

a result of the lower electric field in AlGaN, which

suppressed the gate injection current. These

improvements using the dual-layer stressor scheme

supports strain engineering as an effective approach

in the pursuit of the normally-off operation of

AlGaN/GaN HEMTs.

Analysis of trap and recovery characteristics based on

low-frequency noise for E-mode GaN HEMTs with p-

GaN gate under repetitive short-circuit stress School of Electronic and Information Engineering, South

China University of Technology, Guangzhou 510641,

People's Republic of China

Science and Technology on Reliability Physics and

Application of Electronic Component Laboratory,

Guangzhou 510610, People's Republic of China

Journal of Physics D: Applied Physics

https://doi.org/10.1088/1361-6463/ab713a

In this letter, the degradation and recovery

characteristics of E-mode AlGaN/GaN high-electron

mobility transistors (HEMTs) were investigated under

repetitive short-circuit (SC) stress. Output, transfer,

transconductance and gate-leakage characteristics

were analyzed in detail before and after repetitive SC

stress. After stress, the electrical characteristics of the

devices gradually degraded as the SC pules increased.

Low-frequency noise measurements are performed

over the frequency range of 1 Hz–10 KHz by increasing

SC pulses. Furthermore, the recovery tendency of DC

characteristics and trap density is observed between

repetitive SC measurements, and this physically

confirms that the mechanism of the performance

degradation could be attributed to the trapping and

releasing processes of electrons in the p-GaN layer and

AlGaN barrier layer of AlGaN/GaN HEMTs, which

change the electric field distribution under the gate.

Effect of surface treatment on electrical properties of

GaN metal–insulator–semiconductor devices with

Al2O3 gate dielectric Department of Electrical and Electronic Engineering, Xi'an

Jiaotong–Liverpool University, Suzhou, People's Republic of

China

Department of Electrical Engineering and Electronics,

University of Liverpool, Liverpool, United Kingdom

Department of Electrical and Computer Engineering, the

National University of Singapore, Singapore, Singapore

Department of Chemistry, Xi'an Jiaotong–Liverpool

University, Suzhou, People's Republic of China


https://doi.org/10.35848/1347-4065/ab7863

This research proposes an economical and effective

method of 1-octadecanethiol (ODT) treatment on GaN

surfaces prior to Al2O3 gate dielectric deposition.

GaN-based metal–insulator–semiconductor (MIS)

devices treated by HCl, O2 plasma and ODT are

demonstrated. ODT treatment was found to be

capable of suppressing native oxide and also of

passivating the GaN surface effectively; hence the

interface quality of the device considerably improved.

The interface trap density of Al2O3/GaN was

calculated to be around 3.0 × 1012 cm−2 eV−1 for

devices with ODT treatment, which is a relatively low

value for GaN-based MIS devices with Al2O3 as the

gate dielectric. Moreover, there was an improvement

in the gate control characteristics of MIS-HEMTs

fabricated with ODT treatment.

Suppression of short-channel effects in normally-off

GaN MOSFETs with deep recessed-gate structures Corporate Research & Development Center, Toshiba

Corporation, 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki

212-8582, Japan


https://doi.org/10.35848/1347-4065/ab6b7f

We have demonstrated the suppression of short-

channel effects (SCEs) in normally-off GaN metal-

oxide-semiconductor field-effect transistors

(MOSFETs) with deep recessed-gate structures. TCAD

simulation results show that the electric field

concentration is effectively reduced at the recessed

edge of MOSFETs with deeper recessed-gate

structures. To demonstrate suppression of SCEs,

https://doi.org/10.1088/1361-6463/ab713a

https://doi.org/10.35848/1347-4065/ab7863

https://doi.org/10.35848/1347-4065/ab6b7f


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MOSFET gate structures with recess depths ranging

from 45 to 165 nm were fabricated and evaluated.

Experimental results show that deeper recessed-gate

structures are highly effective for suppressing drain-

induced barrier lowering and improving subthreshold

swing and threshold voltage roll-off.

Balanced-to-Doherty Mode-Reconfigurable Power

Amplifier With High Efficiency and Linearity Against

Load Mismatch Department of Electrical and Computer Engineering,

University of Central Florida, Orlando, FL 32816 USA

Department of Electrical and Computer Engineering,

University of Central Florida, Orlando, FL 32816 USA

IEEE Transactions on Microwave Theory and Techniques

https://doi.org/10.1109/TMTT.2020.2979844

A balanced-to-Doherty (B2D) mode-reconfigurable

power amplifier (PA) is presented in this article, which

is endowed with a unique capability of maintaining

high linearity and high efficiency against load

mismatch. The Doherty operation of this PA is based

on a new Doherty PA (DPA) architecture configured

from an ideal balanced amplifier, named quasi-

balanced DPA (QB-DPA). This article, for the first time,

analytically proves that the QB-DPA is functionally

equivalent to a standard DPA. Most importantly, this

new discovery enables PA reconfiguration between

the Doherty and balanced modes. With the tunability

implemented using a silicon-on-insulator (SOI)-based

single-pole-double-throw (SPDT) switch, a

reconfigurable B2D PA prototype using GaN

technology is demonstrated at 3.5 GHz, exhibiting the

state-of-the-art linear DPA performance in the

nominal 50-Ω load condition. Specifically, the Doherty

mode achieves a continuous-wave measurement

efficiency of 70% and 54.5% at the maximum output

power of 41.9 dBm and 6-dB power back-off,

respectively. In the modulated long-term evolution

(LTE) evaluation, the DPA exhibits -37-dB adjacent

channel power leakage (ACPR) and 2.36% error vector

magnitude (EVM) at the maximum rated power of 34.5

dBm while achieving a 42.4% efficiency. It is

experimentally demonstrated that the Doherty (QB-

DPA) mode is well resistant to load mismatch with high

efficiency across a majority portion of the 2:1 voltage

standing wave ratio (VSWR) circle, while the

combination of Doherty and balanced modes can

ensure a constantly linear performance of the B2D PA

(e.g., 2.2%-5% of EVM) under the entire mismatch

condition.

Threshold voltage control of non-recessed GaN MOS

HEMTs and recessed GaN MOS FETs by Al x Ga1−x N

back barrier Technology Division/Renesas Semiconductor

Manufacturing Co., Ltd., Shiga 520-8555, Japan

Technology Division/Renesas Semiconductor

Manufacturing Co., Ltd., Naka, Ibaraki 312-8504, Japan


https://doi.org/10.35848/1347-4065/ab778a

Threshold voltage (V th) control of a GaN MOS

transistor by Al x Ga1−x N back barrier was

systematically studied. Non-recessed GaN MOS

HEMTs and recessed GaN MOS FETs with an Al x Ga1−x

N (x = 0%, 3%, 5%, 8%) back barrier layer were

fabricated on the same 6-inch GaN-on-Si wafers and

characterized. Al2O3 gate-insulator thickness was

changed from 20 to 100 nm to evaluate the

Al2O3/GaN interface fixed charge. The V th of the GaN

MOS transistor increases with increasing in Al content

x of the Al x Ga1−x N back barrier layer and decreasing

in Al2O3 thickness. The dependences of V th on Al

content x and Al2O3 thickness were different between

non-recessed and recessed transistor. The different

dependences of V th on Al content x and Al2O3

thickness were explained well by the newly introduced

surface donor model, which compensate not only the

surface polarization charge but also the surface

electric field.

Fabrication of AlGaN/GaN MISHEMT with dual-metal

gate electrode and its performances School of Electronics Engineering, Kyungpook National

University, Daegu, 41566, Republic of Korea

Center for BioMicroSystems, Brain Science Institute, Korea

Institute of Science and Technology (KIST), Seoul, 02792,

Republic of Korea

Applied Physics A

https://doi.org/10.1007/s00339-020-3453-4

In this study, we investigated AlGaN/GaN metal–

insulator–semiconductor high-electron-mobility

transistors (MISHEMTs) with single-metal gate (SMG)

and dual-metal gate (DMG) structures through

https://doi.org/10.1109/TMTT.2020.2979844

https://doi.org/10.35848/1347-4065/ab778a

https://doi.org/10.1007/s00339-020-3453-4


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experimental measurements and technology

computer-aided design simulation. The DMG structure

consists of nickel (Ni) in the source-side gate and

titanium (Ti) in the drain-side gate metals for the

distribution of an electric field. The measurement

results demonstrate that the fabricated AlGaN/GaN

DMG–MISHEMT produces improved device

performances; this includes higher drain current (ID),

higher transconductance (gm), and higher breakdown

voltage than the SMG–MISHEMT. The improvement is

due to the distribution of an electric field. In addition,

in terms of current collapse characteristics, the DMG–

MISHEMT exhibited a small change rate in ID at

various quiescent bias points. These results mean that

a DMG structure leads to excellent electrical

characteristics.

GaN HEMTs on Si with Regrown Contacts and

Cutoff/Maximum Oscillation Frequencies of 250/204

GHz School of Electrical and Computer Engineering, Cornell

University, Ithaca, NY 14853 USA

Veeco Instruments Inc., Somerset, NJ 08873 USA

Department of Materials Science and Engineering, Cornell

University, Ithaca, NY 14853 USA

Kavli Institute for Nanoscience, Cornell University, Ithaca,

NY 14853 USA

IEEE Electron Device Letters

https://doi.org/10.1109/LED.2020.2984727

This work demonstrates the high-frequency and high-

power performance capacity of GaN high electron

mobility transistors (HEMTs) on Si substrates. Using a

T-gate and n++-GaN source/drain contacts, the

InAlN/GaN HEMT with a gate length of 55 nm and a

source-drain spacing of 175 nm shows a maximum

drain current ID,MAX of 2.8 A/mm and a peak

transconductance gm of 0.66 S/mm. The same HEMT

exhibits a forward-current-gain cutoff frequency fT of

250 GHz and a maximum frequency of oscillation

fMAX of 204 GHz. The ID,MAX, peak gm and fT-fMAX

product are among the best reported for GaN HEMTs

on Si, which are very close to the state-of-the-art

depletion-mode GaN HEMTs on SiC without a back

barrier. Given the low cost of Si and the high

compatibility with CMOS circuits, GaN HEMTs on Si

prove to be particularly attractive for cost-sensitive

applications.

Millimeter-Wave AlGaN/GaN HEMTs with 43.6%

Power-Added-Efficiency at 40 GHz Fabricated by

Atomic Layer Etching Gate Recess Key Laboratory of Microelectronic Devices & Integrated

Technology, Institute of Microelectronics of Chinese

Academy of Sciences, Beijing 100029, China

University of Chinese Academy of Sciences, Beijing 100049,

China

Key Laboratory of Microelectronic Devices & Integrated




https://doi.org/10.1109/LED.2020.2984663

Low damage atomic layer etching (ALE) gate recess is

developed for fabrication of millimeter-wave

AlGaN/GaN high-electron-mobility transistors

(HEMTs). Plasma ion induced bombardments to the

AlGaN barrier is effectively suppressed by the ALE

recess, contributing to a well-controlled recessed

surface morphology. The suppressed lattice damage

to AlGaN/GaN heterostructure is also reflected by a

significantly reduced gate leakage as well as an

invisible threshold voltage shift associated with

damage induced traps. With a 0.15-μm T-gate

fabrication technology, a high power-gain cutoff

frequency fMAX of 205 GHz has been achieved. The

ALE-recessed AlGaN/GaN HEMTs exhibits a record

high power-added-efficiency (PAE) of 43.6% at 40 GHz

in a continuous-wave mode. The associated gain and

output power density are also remarkably improved

compared with controlled HEMTs with conventional

gate recess process.

PEALDInvestigation of SiNx and AlN Passivation for

AlGaN/GaN High-Electron-Mobility Transistors: Role

of Interface Traps and Polarization Charges Department of Electronic and Computer Engineering, The

Hong Kong University of Science and Technology, Hong

Kong

IEEE Journal of the Electron Devices Society

https://doi.org/10.1109/JEDS.2020.2984016

In this work, we studied the mechanisms and

switching properties of AlGaN/GaN high-electron-

mobilitytransistors (HEMTs) passivated by

amorphous-SiNx and monocrystal-like AlN. The effects

of interface traps and polarization charges on current

https://doi.org/10.1109/LED.2020.2984727

https://doi.org/10.1109/LED.2020.2984663



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collapse are investigated by TCAD simulations and

experimental characterizations. Surface/interface

deep levels can be compensated by both shallow

donor-like traps (SiNx passivation) and polarization

charges (AlN passivation) at

passivation/heterostructure interface, but with

different levels of effectiveness under fast switching

conditions. SiNx-passivation introduces shallow

donor-like trap states with short time constant that

favors a fast emission of trapped electrons in the

access region and suppressed current collapse, but

nevertheless exhibits more severe time-dependent

recovery of dynamic ON-resistance. For AlN

passivation, interface traps are compensated by the

fixed positive polarization charges and the OFF-state

depletion region (in the 2DEG channel) is formed

predominantly by electric-field effect, leading to an

immediate accumulation of high channel electron

concentration after switching the HEMT devices back

to ON-state and instant response of drain current to

gate and drain bias. The field plate structure is

necessary in SiNx-passivated devices for both current

collapse suppression and electric field alleviation.

With AlN passivation, the field plate can be solely

designed for achieving more uniform electric field

distribution for gate reliability concern without the

concern of current collapse.

Noise performance of an AlGaN/GaN monolithic

microwave integrated circuit (MMIC) low-noise

amplifier under laser exposure University of Messina, Department of Engineering, 98166

Messina, Italy

Scienze Fisiche e Scienze della Terra, University of Messina,

Dipartimento di Scienze Matematiche e Informatiche,

98166 Messina, Italy

IET Microwaves, Antennas & Propagation

https://doi.org/10.1049/iet-map.2019.0776

The aim of this study is to disclose how the

performance of a gallium nitride (GaN)-based X-band

low-noise amplifier is modified by applying a blue-ray

(404 nm) laser beam. The tested amplifier employs an

aluminium gallium nitride/GaN (AlGaN/GaN) high

electron mobility transistor on silicon carbide whose

dc and noise behaviour have been first analysed with

and without optical illumination. Mild improvement of

the gain together with severe degradation of the noise

figure has occurred during light exposure with the

amplifier operating according to the recommended

bias condition. Conversely, pronounced improvement

of the performance has taken place when the

amplifier has been biased close to the transistor pinch-

off point. The results presented in this work follow a

previous intense activity carried out on devices and

amplifiers based on gallium arsenide technology.

Design Strategies for Mesa-Type GaN-Based Schottky

Barrier Diodes for Obtaining High Breakdown Voltage

and Low Leakage Current State Key Laboratory of Reliability and Intelligence of

Electrical Equipment, School of Electronics and Information

Engineering, Hebei University of Technology, Tianjin

300401, China

Key Laboratory of Electronic Materials and Devices of

Tianjin, Hebei University of Technology, Tianjin 300401,

China

Department of Photonics, Institute of Electro-optical

Engineering, National Chiao Tung University, Hsinchu

30010, Taiwan

Department of Electrical Engineering and Computer

Sciences, Tsinghua-Berkeley Shenzhen Institute (TBSI),

University of California at Berkeley, Berkeley, CA 94720 USA


https://doi.org/10.1109/TED.2020.2978007

In this article, we have systematically investigated the

impact of different structural parameters on the

breakdown voltage for GaN-based trench MIS barrier-

controlled Schottky (TMBS) rectifier. Compared with

the planar Schottky rectifier, the TMBS rectifier has

field plates on the mesa sidewalls so that the drift

region can be depleted in a 2-D manner, which helps

to decrease the electric field at the metal/mesa

interface. However, the adoption of mesas can make

the electric potential lines at the mesa corner dense

and has large curvatures. Therefore, the premature

breakdown can occur when the electric field therein

reaches the critical condition. We find that the electric

field profiles can be affected by insulation layer

thickness, mesa width, trench depth, and different

types of insulation layers. Then, we increase the

breakdown voltage by homogenizing the electric field

distribution in the mesa region, e.g., the electric field

at mesa corners can be decreased by adopting

properly thick sidewall insulator and small trench

depth. Meanwhile, TMBS rectifier using sidewall

https://doi.org/10.1049/iet-map.2019.0776

https://doi.org/10.1109/TED.2020.2978007


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insulating material with a large dielectric constant

more favors a large breakdown voltage.

1.4-kV Quasi-Vertical GaN Schottky Barrier Diode

With Reverse p-n Junction Termination Key Laboratory of Advanced Photonic and Electronic

Materials, School of Electronic Science and Engineering,

Nanjing University, Nanjing, China

IEEE Journal of the Electron Devices Society


In this paper, we demonstrate high-performance

quasi-vertical GaN-on-Sapphire Schottky barrier

diodes (SBD) with a reverse GaN p-n junction

termination (RPN). The SBD has a current output of 1

kA/cm 2 at VF=2.5 V, a low Von of 0.66 V ± 0.017 V, a

low Ron,sp of 1.4 mΩ⋅ cm 2 , current ON/OFF ratio of

over 109 (−3 V~3 V). By introducing the RPN, the

breakdown voltage can boost from 459 V to 1419 V,

and power figure-of-merit (FOM) can reach 1438

MV/cm 2 . It is shown that the presence of the RPN

with a suitable anode recess depth can generate an

electric field (EF) opposite to the built-in EF at the

center of the second top p-n junction, which can

decrease the EF peak intensity and make the electric

field more uniformly distributed inside the device.

Finally, the leakage current of the SBD is inhibited and

the breakdown voltage is increased.

A 177-183 GHz High-Power GaN-based Frequency

Doubler with over 200 mW Output Power National Key Laboratory of ASIC, Hebei Semiconductor

Research Institute, Hebei, Shijiazhuang 050051, China


https://doi.org/10.1109/LED.2020.2981939

A GaN Schottky barrier diode (SBD) on SiC for

frequency doubler applications was fabricated with a

N-/N+ GaN stack of 200 nm / 1500 nm in thickness and

5×1017 cm-3 / 8×1018 cm-3 in doping densities,

respectively. A cut-off frequency of 459 GHz at zero

bias and reverse breakdown voltage of 15.4 V were

obtained. A quartz glass circuit with flip-chip-mounted

GaN SBDs was inserted between split-waveguide

blocks to form a balanced frequency doubler. When

driven with 2 W input power in pulsed mode,

measured output power was 200-244 mW from 177-

183 GHz with efficiency 9.5-11.8%.

MEMS Chip with Amplifier for 4-Watt Power

Combining up to 100 GHz State Key Laboratory of Millimeter Waves, School of

Information Science and Engineering, Southeast University,

Nanjing 210096, P. R. China

Science and Technology on Monolithic Integrated Circuits

and Modules Laboratroy, Nanjing 210016, P. R. China

IEEE Transactions on Components, Packaging and

Manufacturing Technology

https://doi.org/10.1109/TCPMT.2020.2980958

Millimeter-wave and terahertz bands are very

attractive for high resolution radars and fifth-

generation communication and beyond, nevertheless,

it is very challenging to achieve high output power in

silicon. To address this crucial issue, this paper firstly

presents an in-house developed silicon

micromachining process. Using this process, power

combiner is formed in silicon waveguide, by dry

etching and bonding two 8-inch silicon wafers.

Benefiting from the hollow, symmetrical and

accurately assembled waveguide structure, the power

combiner features a measured low loss of 0.2 dB and

high amplitude/phase balance of ±0.15 dB/±2° from

92 to 96 GHz. Moreover, based on this power

combiner and an in-house fabricated power amplifier

in Gallium nitride (GaN), this paper further

demonstrates a power combing prototype with a

typical output power of 4 W, a power-added efficiency

of higher than 12.9%, and a combining efficiency of

higher than 92%.

High Linearity and High Gain Performance of N-Polar

GaN MIS-HEMT at 30 GHz Electrical and Computer Engineering Department,

University of California – Santa Barbara, Santa Barbara, CA

93106, USA


https://doi.org/10.1109/LED.2020.2980841

Though GaN HEMTs have primarily been used for

power amplification, they are also well suited for

receiver applications. In the front-end of receivers,

non-linearities, third-order intermodulation products

lead to in-band signal distortion. The intermodulation


https://doi.org/10.1109/LED.2020.2981939

https://doi.org/10.1109/TCPMT.2020.2980958

https://doi.org/10.1109/LED.2020.2980841


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distortion is primarily dominated by transconductance

and its derivatives. In this paper, we report on N-polar

GaN MIS-HEMTs able to simultaneously achieve high

gain (12.7 dB) and excellent linearity performance

(OIP3/PDC of 15 dB) for low-power receiver

application at 30 GHz. With a two-tone load-pull input-

bias sweep, we demonstrate that the linearity of high

performance HEMTs is sensitive to bias, and we

present our measurement methodology to

accommodate this.

Switching Performance Analysis of Vertical GaN

FinFETs: Impact of Inter-Fin Designs College of Electrical Engineering, Zhejiang University,

Hangzhou 310027, China

Center for Power Electronics Systems, Virginia Polytechnic

Institute and State University, Blacksburg, VA 24061 USA

Microsystems Technology Laboratories, Massachusetts

Institute of Technology, Cambridge, MA 02139 USA

IEEE Journal of Emerging and Selected Topics in Power

Electronics

https://doi.org/10.1109/JESTPE.2020.2980445

This work studies the switching performance of

vertical GaN power FinFETs and proposes new inter-

fin designs to improve it. The inter-fin region has been

found to be an important limiting factor for FinFET

switching performance. The time taken to (dis)charge

the dielectric parasitic capacitances and drift layer in

the inter-fin regions severely limits the device turn-

(on)off speed. Three new inter-fin designs are

proposed, based on (a) reduced fin-to-fin spacing, (b)

oxide full-filling and (c) splitgate structures. 1.2 kV, 80

mΩ vertical GaN FinFETs with these designs were

evaluated by a well-calibrated device-circuit

mixedmode TCAD simulation. Both the reduced-fin-

spacing structure and the oxide full-filling reduce the

dielectric parasitic capacitances, but only lead to small

reduction (less than 10%) in switching losses. Much

better improvement is obtained with the split-gate

structure, which removes the gate metal in the inter-

fin region and exposes the drift layer to the field lines

from the source metal. During the turn-(on)off of the

transistor with a split-gate structure, the drift layer

underneath the inter-fin gap region is (dis)charged by

a combination of the drain-to-source and gate

currents, leading to shorter switching times and lower

switching losses. By utilizing the split-gate structure,

simulations predict a 58% improvement in the

switching figure-of-merit and 38% lower switching

losses in 1.2 kV vertical GaN power FinFETs. These

results provide key understanding and design

guidelines for power FinFETs. Finally, an 800 V buck

converter using a 1.2 kV GaN FinFET half-bridge

module is simulated, showing excellent efficiency

when operating at multi-megahertz frequency and

revealing the requirement for device thermal

management. This highlights the great potential of

vertical GaN power FinFETs for future high-frequency

medium-voltage power applications.

Improved DC and RF Performance of Novel MIS p-

GaN-Gated HEMTs by Gate-All-Around Structure Institute of Electronics Engineering, National Tsing Hua

University, Hsinchu 30013, Taiwan

Innovation Technology Research Center, Global Wafers

Company Hsinchu 300, Taiwan


https://doi.org/10.1109/LED.2020.2980584

In this study, we report a novel structure of

enhancement-mode metal-insulator-semiconductor

high electron mobility transistor (E-mode MIS HEMT)

with p-GaN gate by gate-all-around technology. The

gate-all-around structure is fabricated by depositing

an insulator and gate to surround the p-GaN mesa. The

p-GaN length is smaller than the gate length, which

would easily turn on the two dimensional electron gas

(2DEG) of channel and result in a higher drain current

and thus improve the device performance. The gate-

all-around p-GaN MIS HEMT has better gate control,

better transconductance, and lower gate leakage

current. The device exhibits a threshold voltage (Vth)

of 1.5 V, a maximum transconductance (Gm.max) of

101 mS/mm, and a drain saturation current density

(JDS,max) of 412 mA/mm at a gate bias (Vg) of 5 V. The

most important achievement is that the gate leakage

current at Vg = 5 V is only 10-8 mA/mm. Moreover, the

ratio of drain current density to gate leakage current

density (JDS/JGS) is 108 at Vg = 5 V. Finally, the cut-off

frequency (ft) and maximum oscillation frequency

(fmax) of microwave pe

https://doi.org/10.1109/JESTPE.2020.2980445

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Distinct Failure Modes of AlGaN/GaN HEMTs Under

ESD Conditions Department of Electronic Systems Engineering, Indian

Institute of Science, Bangalore, India

Center for Nanoscience and Engineering, Indian Institute of

Science, Bangalore, India


https://doi.org/10.1109/TED.2020.2974508

This article reports the distinct failure mechanisms and

insights on device degradation of AlGaN/GaN high

electron mobility transistors (HEMTs) under

electrostatic discharge (ESD) stress conditions. The

role of device surface, MESA isolation, and gate

Schottky junction in defining the degradation type is

discovered. Premature breakdown at the MESA

Schottky junction and dislocation induced failure in

the active region and their consequences on ESD

robustness are reported. Physical mechanisms

responsible for snapback instability in transmission

line pulsing (TLP) characteristics are discussed. Change

in device failure from soft to hard with pulsewidth is

revealed. Finally, the role of contact resistivity, surface

diffusion, and channel electric field and its fringing

effect at contacts are analyzed in context to ESD

failure of AlGaN/GaN HEMTs. Various stages of device

degradation during TLP stress are captured on-the-fly

using high-resolution (HR) optical microscopy and

high-speed Si charge-coupled device (CCD) detector.

Postdevice failure, damaged regions are analyzed

using transmission electron microscopy and scanning

electron microscopy together with in situ energy-

dispersive X-ray spectroscopy to probe details of

failure mechanisms involved. Finally, based on the

learning from this article, design guidelines for an ESD

robust HEMT are proposed.

Experimental Study on the Short-Circuit Instability of

Cascode GaN HEMTs Department of Electrical Engineering and Information

Technologies, University of Naples Federico II, Naples, Italy


https://doi.org/10.1109/TED.2020.2974518

This article presents an experimental investigation on

the short-circuit (SC) instability of several

commercially available cascode gallium nitride (GaN)

high-electron-mobility transistors (HEMTs). In the SC

test, self-sustained oscillation is observed during the

SC transient. The SC oscillation features some unique

characteristics. The gate resistor shows very weak

damping effect on the SC oscillation. The SC oscillation

thereby cannot be suppressed by utilizing a large gate

resistor. With the increase in the dc-bus voltage, the

SC oscillation greatly amplifies and becomes more

unstable. When the dc-bus voltage reaches 200–250

V, catastrophic failure occurs. In the SC test, two

distinct failure modes, which are related to the failure

of low-voltage (LV) MOSFET and depletion-mode

HEMTs (DHEMTs), are identified. Based on the

experimental evidence and simulation study, the root

causes of the failure are clarified in the end.

Identification of Trap States in p-GaN Layer of a p-

GaN/AlGaN/GaN Power HEMT Structure by Deep-

Level Transient Spectroscopy Department of Electronic and Computer Engineering, The

Hong Kong University of Science and Technology, Kowloon,

Hong Kong

Key Laboratory of Microelectronic Devices and Integrated




https://doi.org/10.1109/LED.2020.2980150

In this work, the deep-level transient spectroscopy

(DLTS) is conducted to investigate the gate stack of the

p-GaN gate HEMT with Schottky gate contact. A

metal/p-GaN/AlGaN/GaN heterojunction capacitor is

prepared for the study. The DLTS characterization

captures the transient capacitance change in the

stack, from which the capacitance of the metal/p-GaN

Schottky junction can be extracted. By proper

selection of the rate window, the impacts of the hole

insufficiency effect are avoided during trap states

evaluation. Thus, the information of deep energy

levels in the p-GaN layer is revealed, which consists of

an electron trap state with activation energy of 0.85

eV and a hole trap state with activation energy of 0.49

eV. The identification of these trap states in the p-GaN

layer provides a physical foundation for understanding

the threshold voltage instability in Schottky-type p-

GaN gate power HEMTs.

https://doi.org/10.1109/TED.2020.2974508

https://doi.org/10.1109/TED.2020.2974518

https://doi.org/10.1109/LED.2020.2980150


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Novel Drain-Connected Field Plate GaN HEMT

Designs for Improved VBD–RON Tradeoff and RF PA

Performance Department of Electronic Systems Engineering, Indian

Institute of Science, Bengaluru, India


https://doi.org/10.1109/TED.2020.2976636

TCAD studies are performed to develop physical

insights into the breakdown behavior of drain-

connected field plate-based GaN HEMTs. Using the

developed insights, to mitigate the performance

bottleneck caused by the lateral drain-connected field

plate design, we have proposed novel vertical-field-

plate designs. The proposed designs alleviate the

channel electric field by uniformly distributing it

vertically into the GaN buffer region. As a result, the

proposed vertical and dual-field-plate design offer 2×

and 3× improvements in breakdown voltage,

respectively, compared with the design without field

plate. Similarly, compared with a design with a lateral

field plate, a 50% improvement in the breakdown

voltage was seen with dual-field-plate architecture. RF

power amplifier (PA) performance extracted using

load-pull simulations demonstrates an improved RF

PA linearity at higher drain bias, improved output

power, efficiency, and PA gain for HEMTs with dual-

and vertical-field-plate designs.

Al0.65Ga0.35N/Al0.4Ga0.6N Micro-Channel

Heterojunction Field Effect Transistors with Current

Density Over 900 mA/mm Electrical and Computer Engineering Department, The Ohio

State University, Columbus, OH 43210 USA

Electrical Engineering Department, University of South

Carolina, Columbia, SC 29208 USA


https://doi.org/10.1109/LED.2020.2977997

We report on the demonstration of high current

density in Al0.65Ga0.35N/Al0.4Ga0.6N heterojunction

field effect transistors with micro-channels enabled by

enhanced contact injection. Devices with a gate length

of 100 nm exhibited a maximum current density of 910

mA/mm and a maximum transconductance of 140

mS/mm. A current gain cut off frequency of 20 GHz

and maximum oscillation frequency of 36 GHz were

obtained. Large-signal load-pull characterization of

the transistors showed output power density of 2.7

W/mm at 10 GHz. The current density and output

power density represent the state-of-art performance

for high Al-composition AlGaN channel transistors.

Comprehensive Design of Device Parameters for GaN

Vertical Trench MOSFETs State key Laboratory of Wide Band-Gap Semiconductor

Materials and Devices, School of Microelectronics, Xidian

University, Xi’an 710071, China

Testing center, Sichuan Institute of Solid-State Circuits,

CETC, Chongqing 400060, China

IEEE Access

https://doi.org/10.1109/ACCESS.2020.2977381

In this work, device parameters for GaN vertical trench

MOSFETs have been investigated systematically to

further improve the device characteristics. The n- GaN

drift layer, the p+ GaN layer and the trench gate are

designed and optimized systematically using Silvaco

ATLAS 2-D simulation, in order to get the best trade-

off between VBR and specific on-resistance Ron.

Three-terminal breakdown curves, the electron

concentration, current density and electric field

strength distributions have been presented to analyze

the breakdown characteristics. The correlations

between different parameters and different initial

conditions are considered, and the eight parameters

are optimized comprehensively. After the final

optimization, record high FOM of 4.8 GW/cm2, VBR of

2783 V, average electric field Edrift of 1.98 MV/cm and

a low Ron of 1.6 mΩ·cm2 are obtained for drift layer

thickness of 14 μm. The product of the thickness Lp

and doping density Np of p+ GaN layer can determine

the breakdown mechanism, and punch through

mechanism would occur when Lp·Np is lower than a

certain value. The results indicate there exists large

optimization room for fabricated GaN vertical trench

MOSFETs, and the device characteristics can be

further improved through the methodology in this

paper for high power and high voltage applications.

https://doi.org/10.1109/TED.2020.2976636

https://doi.org/10.1109/LED.2020.2977997

https://doi.org/10.1109/ACCESS.2020.2977381


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Bias-Dependent Electron Velocity Extracted From N-

Polar GaN Deep Recess HEMTs Electrical and Computer Engineering Department,

University of California Santa Barbara, Santa Barbara, CA,

USA


https://doi.org/10.1109/TED.2020.2973081

This article reports on the extraction of the electron

velocity as a function of gate bias from N-polar GaN

deep recess high-electron-mobility transistors

(HEMTs) designed for mm-wave power amplification.

Bias-dependent small-signal S-parameter

measurements are used to obtain small-signal

equivalent circuit parameters, which are applied to a

transit delay model. The model accounts for fringing

capacitance to arrive at an electron velocity associated

with the transit of the physical gate length. A peak

electron velocity of 1.4×107 cm/s was obtained at a

drain current of 700 mA/mm corresponding to a

channel charge density of 0.3×1013 cm −2 . At higher

current, the velocity slowly decreased with the

electron velocity crossing below 107 cm/s at 1.8

A/mm. This behavior was found to be in good

agreement with a previously proposed model based

on optical phonon scattering at the source injection

point. An analysis of the delay components is used to

provide guidance for the factors influencing the device

performance.

E-Mode p-n Junction/AlGaN/GaN (PNJ) HEMTs Department of Electrical and Electronic Engineering,

Southern University of Science and Technology, Shenzhen,

China

Department of Electronic and Computer Engineering, The

Hong Kong University of Science and Technology, Hong

Kong


https://doi.org/10.1109/LED.2020.2977143

In this work, we demonstrate a GaN-based p-n

junction gate (PNJ) HEMT featuring an n -GaN/ p -

GaN/AlGaN/GaN gate stack. Compared to the more

conventional p -GaN gate HEMT with a Schottky

junction between the gate metal and p -GaN layer, the

p-n junction can withstand higher reverse bias at the

same peak electric-field as the depletion region

extends to both the n -side and p -side, while

exhibiting lower leakage current. The PNJ-HEMT

shows a positive threshold voltage ( VTH ) of 1.78 V, a

small gate leakage (∼10−3 mA/mm @ VGS=10V ). In

particular, a large forward gate breakdown voltage of

19.35 V at 25 °C and 19.70 V at 200 °C was achieved

with the PNJ-gate HEMT.

https://doi.org/10.1109/TED.2020.2973081

https://doi.org/10.1109/LED.2020.2977143


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ELECTRONICS

PI expands range of InnoSwitch3 ICs incorporating robust 750 V GaN transistors PowerElectronicsNews

Power Integrations announced an expansion of its InnoSwitch3 families of offline CV/CC flyback switcher ICs. The

new INN3x78C devices incorporate a smaller “size 8” 750 V PowiGaN transistor, enabling compact, efficient

power supplies delivering between 27 W and 55 W without heatsinks. The ICs are housed in the same high-

creepage, safety-compliant InSOP-24D package as larger members of the GaN-based InnoSwitch3 families, which

target up to 120 W.

Known for exceptional efficiency – up to 94% efficient across line and load, PowiGaN technology is also extremely

robust, making them highly resistant against line surges and swells commonly seen in regions with unstable mains

voltage. This enables OEMs to specify a single power supply design to be used worldwide. Applications for the

new parts include USB PD and high-current chargers/adapters for mobile devices, as well as set-top boxes,

displays, networking and gaming products and appliances – especially those aiming to comply with the planned

European Energy Labeling Regulation.

5G RF Issues Send Soitec Seeking New Wafer Material eetimes

BARCELONA – Despite the Mobile World Congress cancellation, the pursuit of 5G grows fiercer by the hour,

especially among electronics players who are hitting silicon performance limits for 5G RF front-end modules.

Among the candidate materials to supplant silicon are compound materials such as gallium nitride (GaN), gallium

arsenide (GaAs), and silicon carbide (SiC), along with piezoelectrics, which are being used to improve filters. GaAs

has been used for power amplifiers in 4G and 5G handsets. GaN has begun gaining traction for power amplifiers

in 5G mmWave markets.

More and more RF fabless chip companies are seeking “new materials to solve their

problems,” Paul Boudre, CEO of Soitec, told EE Times this week in an interview here.

Together with CEA-Leti, Soitec (Grenoble, France) pioneered silicon-on-insulator (SOI)

substrates. Already very successful with RF SOI wafers (used by RF chip companies to make

switches and antenna tuners for smartphones), Soitec is poised to expand by branching into

the new world of compound materials.

Boudre described a Soitec plan “to develop, generate and offer new materials based on our engineered

substrates” for fabless chip companies. A list of Soitec’s new material adventures includes:

• Piezoelectric-on-insulator (POI) engineered substrates — used to produce high-performance surface

acoustic wave (SAW) filter components for 4G and the 5G New Radio (NR) bands

• GaN-on-Si, GaN-on-SiC epiwafers. Soitec last year acquired Imect’s spinoff EpiGaN in Belgium, which

developed the epiwafers. By integrating EpiGaN into Soitec and bankrolling the necessary tools, Soitec

plans to enter the high-volume manufacturing base for the 5G GaN power amplifier market.

https://www.powerelectronicsnews.com/pi-expands-range-of-innoswitch3-ics-incorporating-robust-750-v-gan-transistors/

https://www.eetimes.com/5g-rf-issues-send-soitec-seeking-new-wafer-material/


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• Soitec will this year start sampling SiC wafers based on the company’s proprietary technology called Smart

Cut.

Soitec’s Smart Cut process allows Soitec engineers to define materials, grow single-crystalline layers of those

materials, and then transfer those layers from one substrate to another. This makes it possible to create active

layers of a wafer that can be managed independently from the supporting mechanical substrates.

Soitec’s goal, applying Smart Cut to SiC, is to significantly improve SiC at the substrate and device levels both in

cost and quality.

The bulk of Soitec’s products are based on FD-SOI and RF-SOI substrates, both of which leverage Smart Cut

technology. Soitec, similarly by using Smart Cut, has also recently put POI into volume production. Next up are

Smart Cut-based SiC wafers, scheduled for sampling later this year.

Why SiC?

But why SiC now? Even with a boom in demand, SiC faces two big challenges. First, there aren’t enough SiC wafers

to go around. Second, when it comes to yield rate, SiC sucks.

Soitec has engineered new Smart Cut SiC wafers with these problems in mind, first by substantially improving the

quality of the SiC layer on the substrate, and second by transitioning from current 6-inch SiC wafers to 8-inch

wafers in order to reduce the cost. Soitec currently has a SiC-wafer pilot line in Grenoble.

To bolster its efforts, Soitec last fall announced a joint development program with Applied Materials. Applied

joined with Soitec to get engaged in materials engineering innovations for silicon carbide technology.

Thomas Piliszczuk, Soitec’s executive vice-president of global strategy, cited two potentially

large markets for Smart Cut-based SiC. One is for EV inverters, aiming for major battery-life

improvements. Another is to capture “5G base-station demand for high-power efficiency and

stringent linearity in power amplifiers.”

Given the shortage of SiC wafers on the market today, what’s Soitec’s business model? Boudre

said, “It’s a good question. We can be SiC wafer providers ourselves, or we can partner with

others by licensing.” Either way, he said, “Our goal is to reinforce SiC wafer supplies, improve its quality and

transition it to 6-inch wafers. All of this will help make the cost structure of SiC wafers competitive.”

In search of new materials beyond silicon

RF semiconductor designers are scrambling for new materials/designs/architecture for 5G systems. But why?

Because 5G uses more different high-frequency

bands to enable high speed data transmission,

the number of power amplifiers, filters,

switches, LNA, antenna tuners that must go

inside 5G RF front-end modules are multiplying

at a bewildering rate. The sheer volume of parts

and components — many remain discrete — is

a headache for smartphone designers who must

squeeze all those RF modules into a 5G phone.

5G smartphone developers are also worried

about the quality, thermal dissipation and

efficiency of RF components, because they

could bog down RF front-end modules’

performance.


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Moreover, not every RF component uses the same material or same technology. As noted, POI is used to improve

filters. GaAs has been the leading material for power amplifiers (PA). But many PA suppliers today are taking a

hard look at GaN. On another hand, RF SOI, a specialized SOI process, has become the standard for making such

RF chips as switch devices and antenna tuners, for 3G, 4G and 5G smartphones and other products.

As Boudre explained, Soitec’s RF-SOI, available since 2016, has gained a lot of RF component customers. These

customers opened Soitec’s eyes, because every RF fabless company is looking for new materials and substrates

to build chips that meet the stringent requirements of 5G’s RF.

One example is power amplifiers for smartphones and base stations.

PA chips in 5G wireless applications are much different from those employed in 4G networks. Broadband

modulation for 5G transmissions demands high-power efficiency and strict linearity from power amplifiers.

Moreover, 5G networks will employ phased-array antennas to focus and steer multiple beams. With a 4×4 phased-

array antenna, for example, the power amplifier must operate at much lower power than for the single-beam

signals currently common in cellular systems.

The story gets even more complicated with a 5G network transmitting at millimeter wave (mmWave) frequencies.

Compared to a sub-6GHz systems, a mmWave counterpart faces even more complicated RF design challenges.

Multiple-input multiple-output (MIMO) antennas are a 5G necessity, because they must serve many devices in

densely deployed environments. They will require power amplifier chips with high-power efficiency and stringent

linearity. Phased-array MIMO antennas with numerous RF front-end components will also ask for power

amplifiers that offer greater integration at lower cost.

The strict requirements imposed by 5G handsets and base stations for power amplifiers led Soitec to aquire

EpiGaN.

For both 5G infrastructure and handset architectures, mandatory attributes for RF semiconductor devices are

“efficiency, compactness, low cost, high power density and linearity,” according to an article co-written by Markus

Behet, Joff Derluyn, Stefan Degroote and Marianne Germain at Soitec’s GaN business unit. The article said,

“Judged in terms of wideband performance, power density and efficiency, legacy technologies — essentially

silicon LDMOS (laterally-diffused metal-oxide semiconductor) or GaAs — are no match for GaN HEMTs (High-

electron-mobility transistor), regardless of whether they are grown on silicon or SiC.”

In the authors’ opinion, GaN technology is “meeting stringent thermal specifications for 5G, while preserving

valuable PCB space for the tightly clustered massive MIMO antenna arrays. In base stations, discrete designs are

already being replaced by space-saving multi-function GaN MMICs and multi-chip modules.”

What about Qualcomm?

Given the emergence of all these new materials — beyond silicon — supposedly to enable the integration of 5G

mmWave RF front-end modules, what’s Qualcomm’s solution?

Qulacomm examined the available options, but in the end, the company chose silicon-based RF solutions,

observed Claire Troadec, Power & Wireless Division director at Yole Développement.

Most likely this is because it was Qualcomm’s first-generation 5G mmWave RF front-end module, noted Boudre.

He is confident that RF solutions leveraging GaN-on-Si technology, for example, could come into play, maybe in

the company’s third or fourth generation of 5G RF modules.

GaN on SiC vs. GaN on Si

EpiGaN has developed both GaN-on-SiC and GaN-on-Si epiwafers. What are the differences between the two?


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Piliszczuk explained that both target the same market. “Today GaN on SiC has leadership” because it is more

mature, he said. “Multiple device makers are working today on GaN-on-Si solutions also for handsets.”

In applications, GaN on SiC is used today for wireless infrastructure (4G/LTE base stations), defense,

communication satellite applications “where highest performance and reliability is mandatory,” observed

Piliszczuk. “GaN on SiC is also a strong contender for 5G MIMO infrastructure,” he added.

Piliszczuk acknowledged that GaN on Si has similar RF performance as GaN on SiC, but is less mature and has

thermal constraints associated with the use of the silicon substrate.

But Soitec is bullish on GaN on Si, because presumably, it can take advantage of the significant economies of scale

inherent in silicon processing. Piliszczuk believes it can “open up new high-volume and consumer markets.”

According to Soitec, 200mm GaN-on-Si products are available today from EpiGaN/Soitec. He noted that GaN-on-

Si is also a strong contender for 5G infrastructure and handsets.

Yole Développement’s Antoine Bonnabel, technology and market analyst for RF devices and technologies within

the Power & Wireless division, remains more cautious.

He told EE Times, “GaN on Si is not yet mature enough to be used commercially.” Meanwhile, “GaN on SiC is today

used.” He explained that both approaches target the same application: power amplification for high frequencies.

According to Bonnabel, “The issue today is that GaN-on-SiC technologies are too expensive compared to silicon-

based solutions. This is the case especially for low-power power amplifiers for massive MIMO, or for power

amplifiers with less than 3 GHz frequencies. In addition, it cannot be integrated for small power applications like

massive MIMO.”

In his opinion, “GaN on SiC is only used when no other solution exists, such as for high-power power amplification

in frequencies over 3 GHz: typically 20W power amplifiers for band n77 – n79 currently in pilot / deployment

phase.”

On the other hand, Bonnabel said, “GaN-on-Si solutions are not as good as GaN-on-SiC approaches, but they can

potentially be lower cost.”

This means, he explained, that GaN on Si could compete on lower power amplification with Si-based LDMOS

technology, thanks to a low-enough price and its integration capability (which GaN on SiC does not have).

Bonnabel concluded, “If Soitec or other players manage to manufacture good quality GaN on Si at reasonable

prices, it could clearly compete with Silicon-based technology. And therefore, it will penetrate the lower power

amplifiers market for massive MIMO. At the end, it could also replace GaN-on-SiC solutions for higher power

applications.”

Asked about Soitec’s EpiGaN gambit, Yole’s analyst said, “Soitec has a long history in entering new innovative

markets and managing to offer the best-in-class substrates. At Yole, we expect the company to do the same with

GaN technologies.”

Future of alternative materials & structures

Researchers are looking ahead of the future where chip designers can leverage different materials in 3D

integration. Earlier this month, Nadine Collaert, program director at Imec, discussed in a plenary session at the

ISSC: “The industry is moving to higher frequencies and higher efficiency. One option is combining III-V materials

(e.g. GaN and SiC) with CMOS to get the benefits of both materials.” She said, “That can be done with 3D

integration,” showing several examples including an image of a 3D nano-ridge with a III-V material grown on a

silicon-on-insulator (SOI) substrate. However, she cautioned, “There’s a lot of work that needs to go into enabling

this.”


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Soitec CEO Boudre, during the interview in Barcelona, noted that RF chip companies want a variety of options

when it comes to technologies they can use to make their chips. Depending on the design and architecture of

their RF front-end solutions, “We think it’s our job to offer to our customers a broad range of solutions a la carte

— ranging from FD-SOI, RF-SOI to GaN and SiC.” In his mind, there will be opportunities to create a range of a new

kind of engineered substrates.

“We think there will be a day when we can develop GaN-on-SiC on Si, for example. Why not?”

Mission Microwave’s GaN-based BUCs support Envistacom’s SatCom terminal upgrade program SemiconductorToday

Mission Microwave Technologies LLC of Santa Fe Springs, CA, USA, which manufactures gallium nitride (GaN)-

based solid-state power amplifiers (SSPAs) and block up-converters (BUCs), and Envistacom of Atlanta, GA, USA,

a provider of communications, cyber and intelligence operations solutions to the US Department of Defense (DoD)

and coalition partners in the aerospace, defense and intelligence communities, have confirmed the initial orders

of a major satellite ground terminal upgrade program for a US Government customer.

Envistacom teamed with Mission Microwave to create an opportunity for their customer to replace legacy

traveling-wave tube amplifiers (TWTA)-based block up-converters (BUCs) with solid-state BUCs based on gallium

nitride (GaN) technology. The initial upgrade platforms include 200 tactical terminals in support of the US Army’s

Project Manager Mission Network (PM MN).

Mission Microwave is providing Envistacom with 200W Ku-band and 50W Ka-band BUCs to replace legacy TWTA-

based up-converters. Mission Microwave says that its competency in designing compact and highly efficient

amplifiers has enabled Envistacom to offer their customer an upgrade path that will extend the life and utility of

this tactical SatCom terminal fleet of over 600 terminals. If taken to completion, the upgrade program could result

in orders of about $44m for Mission Microwave.

“The end-users of our products rely on proven SatCom system providers like Envistacom to bring the benefits of

solid-state designs to the tactical edge,” says Mission Microwave’s VP of sales & marketing Steve Richeson. “We

worked with Envistacom’s engineering team to navigate the complexities of the upgrade and certification process

for these terminals. Envistacom’s reputation and knowledge of the tactical customers’ expectations has made it

possible for Mission Microwave to bring these benefits to critical field operators,” he adds. “We expect the trend

of replacing high-power TWTAs with SSPAs to be a significant market for the foreseeable future. Envistacom has

been a critical partner in bringing this to market.”

“Our tactical customers demand the reliability, performance and lower total cost of ownership associated with

solid-state amplifiers,” says Russ Coolman, product manager, Envistacom. “Mission Microwave’s innovative

application of GaN technology has enabled the use of solid-state BUCs at power levels that were previously not

practical.”

Room-temperature bonded GaN/diamond interface improves cooling of HEMTs SemiconductorToday

A room-temperature bonding technique for integrating wide-bandgap materials such as gallium nitride (GaN) with

thermally conducting materials such as diamond could boost the cooling effect on GaN devices and facilitate

better performance through higher power levels, longer device lifetime, improved reliability and reduced

manufacturing costs, reports the USA’s Georgia Tech, in collaboration with Japan’s Meisei University and Waseda

University (Zhe Cheng et al, ‘Interfacial Thermal Conductance across Room-Temperature-Bonded GaN/Diamond

Interfaces for GaN-on-Diamond Devices’, ACS Appl. Mater. Interfaces, 2020, 12, 8376−8384). The work was

http://www.semiconductor-today.com/news_items/2020/mar/mission-microwave-120320.shtml

http://www.semiconductor-today.com/news_items/2020/mar/gatech-180320.shtml


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supported by a multi-disciplinary university research initiative (MURI) project (grant no. N00014-18-1-2429) from

the US Office of Naval Research (ONR). The technique could have applications for wireless transmitters, radars,

satellite equipment and other high-power and high-frequency electronic devices.

The surface-activated bonding technique uses an ion source in a high-vacuum environment to first clean the

surfaces of the GaN and diamond, which activates the surfaces by creating dangling bonds. Introducing small

amounts of silicon into the ion beams facilitates forming strong atomic bonds at room temperature, allowing the

direct bonding of the GaN and single-crystal diamond that allows the fabrication of high-electron-mobility

transistors (HEMTs).

The resulting interface layer from GaN to single-crystal diamond is just 4nm thick, allowing heat dissipation up to

two times more efficient than in state-of-the-art GaN-on-diamond HEMTs by eliminating the low-quality diamond

left over from nanocrystalline diamond growth. Diamond is currently integrated with GaN using crystalline growth

techniques that produce a thicker interface layer and low-quality nanocrystalline diamond near the interface.

Additionally, the new process can be performed at room temperature using surface-activated bonding

techniques, reducing the thermal stress applied to the devices.

Picture: Cross-section bright-field high-resolution STEM images of GaN-diamond interfaces bonded by

surface-activated bonding technique. (Zhe Cheng, Georgia Tech)

“This technique allows us to place high-thermal-conductivity materials much closer to the active device regions in

gallium nitride,” notes Samuel Graham, the Eugene C. Gwaltney Jr School Chair and Professor in Georgia Tech’s

George W. Woodruff School of Mechanical Engineering. “The performance allows us to maximize the performance

for gallium nitride on diamond systems. This will allow engineers to custom design future semiconductors for

better multi-functional operation.”

For high-power electronic applications using materials such as GaN in miniaturized devices, heat dissipation can

be a limiting factor in power densities imposed on the devices. By adding a layer of diamond, which conducts heat

five times better than copper, engineers have tried to spread and dissipate the thermal energy.

However, when diamond films are grown on GaN, they must be seeded with nanocrystalline particles about 30nm

in diameter, and this layer of nanocrystalline diamond has low thermal conductivity – which adds resistance to

the flow of heat into the bulk diamond film. In addition, the growth takes place at high temperatures, which can

create stress-producing cracks in the resulting transistors.


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“In the currently used growth technique, you don’t really reach the high-thermal-conductivity properties of the

microcrystalline diamond layer until you are a few microns away from the interface,” Graham says. “The materials

near the interface just don’t have good thermal properties. This bonding technique allows us to start with ultra-

high thermal conductivity diamond right at the interface.”

By creating a thinner interface, the surface-activated bonding technique moves the thermal dissipation closer to

the GaN heat source.

“Our bonding technique brings high-thermal-conductivity single-crystal diamond closer to the hotspots in the GaN

devices, which has the potential to reshape the way these devices are cooled,” believes the paper’s first author

Zhe Cheng, a recent Georgia Tech Ph.D. graduate. “And because the bonding takes place near room temperature,

we can avoid thermal stresses that can damage the devices.”

That reduction in thermal stress can be significant, going from as much as 900MPa to less than 100MPa with the

room-temperature technique. “This low-stress bonding allows for thick layers of diamond to be integrated with

the GaN and provides a method for diamond integration with other semiconductor materials,” Graham says.

Beyond GaN and diamond, the technique can be used with other semiconductors, such as gallium oxide, and other

thermal conductors such as silicon carbide. Graham says that the technique has broad applications to bond

electronic materials where thin interfacial layers are advantageous.

“This new pathway gives us the ability to mix and match materials,” he says. “This can provide us with great

electrical properties, but the clear advantage is a vastly superior thermal interface. We believe this will prove to

be the best technology available so far for integrating wide-bandgap materials with thermally conducting

substrates.”

In future work, the researchers plan to study other ion sources and evaluate other materials that could be

integrated using the technique.

“We have the ability to choose processing conditions as well as the substrate and semiconductor material to

engineer heterogenous substrates for wide-bandgap devices,” Graham says. “That allows us to choose the

materials and integrate them to maximize electrical, thermal and mechanical properties.”

VisIC launches 100kW motor inverter reference design for 800V power-bus based on D3GaN SemiconductorToday

VisIC Technologies Ltd of Nes Ziona, Israel – a fabless developer of power conversion devices based on gallium

nitride (GaN) metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) for the automotive,

data-center and industrial markets – has cooperated with the University of Texas at Austin to develop a 100kW

inverter reference design that can be used as a base for a 800V power-bus motor inverter in electric vehicle (EV),

industrial, PV and other applications.

Wide-bandgap (WBG) power technology is fast becoming the technology of choice to replace silicon in EV motor

drives to achieve better efficiency. It is commonly viewed that GaN technology will be used primarily in the 400V

power-bus due to its lower cost compared with other WBG technologies, and silicon carbide (SiC) is commonly

used in the high-voltage 800V power-bus for higher-power applications. VisIC says that the new 100kW inverter

reference design proves that GaN technology can also be used in the 800V power-bus applications, producing the

most cost-effective solution for both the 400V and 800V EV power-bus.

http://www.semiconductor-today.com/news_items/2020/mar/visic-180320.shtml


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Based on VisIC’s unique D3GaN technology, the 100kW inverter reference design can be adapted to work both

under 800V and 900V power-bus. The firm says that the GaN devices have highly thermally efficient SMD

packaging, high threshold voltage, fast switching and easy paralleling for what is claimed to be most cost-effective,

highly efficient and reliable inverter solution for EVs.

The estimated peak efficiency can reach 99.3% with 40kHz switching frequency, due to the low switching losses

of D3GaN devices. The total dimension is 26.9cm x 21.4cm x3.5cm with liquid cooling heatsink. The power density

is 50kW/liter including the liquid cooling. The total weight is about 2.5kg.

“Previously GaN has demonstrated its superior performance in achieving high power density for chargers,” says

Dr Alex Huang, director of The Semiconductor Power Electronics Center at University of Texas at Austin. “Thanks

to VisIC GaN’s superior packaging concept and low losses, we believe high power density can also be achieved in

very high-power application such as traction inverters,” he comments.

“We are very happy with the cooperation with University of Texas as they’ve shown professional power design

and innovative system solution,” says VisIC’s chief technology officer Gregory Bunin. “This breakthrough will also

enable the 800V EV power-bus to benefit from the GaN low-cost and high-efficiency technology and provide cost-

effective EV cars.”

As the IEEE Applied Power Electronics Conference and Exposition (APEC 2020) in New Orleans (15-19 March) has

been cancelled, the inverter reference design is now planned to be displayed in booth 9-137 at PCIM 2020 (Power

Conversion and Intelligent Motion) in Nuremberg, Germany (28-30 July).

Transphorm’s GaN FETs used in HZZH’s 98%-efficient power module SemiconductorToday

Transphorm Inc of Goleta, near Santa Barbara, CA, USA — which designs and manufactures JEDEC- and AEC-Q101-

qualified high-voltage gallium nitride (GaN) field-effect transistors (FETs) — says that Hangzhou Zhongheng

Electric Co Ltd (HZZH) has developed an ultra-efficient, GaN-based power module. The 3kW ZHR483KS uses

Transphorm’s GaN devices to reach 98% efficiency, making it the telecoms industry’s most efficient GaN-powered

module to date, it is reckoned. Original design manufacturers (ODMs) can swap the ZHR483KS — which offers

standardized output connector configurations — with existing same-wattage power modules to achieve a high-

reliability, higher-performing solution at a lower overall system cost.

Currently in production, the ZHR483KS is HZZH’s first GaN-based power solution and is the flagship product for a

new product line. The module’s input voltage ranges from 85V to 264V, while its output voltage ranges from 42V

to 58V. Transphorm’s TPH3205WS GaN devices are used in an interleaved bridgeless totem-pole PFC to achieve

98% efficiency at half load. The GaN devices lower the power module’s switching and driving losses, leading to

the ZHR483KS outperforming preceding modules that used superjunction silicon MOSFETs.

“We sought a power transistor that would enable us to develop a more efficient yet cost-effective solution for

our customers,” says HZZH’s chief technology officer Dr Guo. “We considered silicon carbide devices but could

not achieve the desired advantages at low voltages,” he adds. “We then vetted several GaN manufacturers’

devices, and ultimately selected Transphorm’s GaN FETs due to their reliability, device cost, and simple

implementation.”

Transphorm’s GaN FETs are two-chip normally-off devices available in standard TO-XXX packages and PQFN

modules that can be driven with common off-the-shelf drivers. The existing Gen III family offers what is claimed

to be the GaN semiconductor industry’s highest threshold voltage at 4V and highest gate robustness at ±20V.

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These features enable customers to easily design in highly reliable GaN solutions to gain the technology’s high-

power density benefits.

“Transphorm develops each generation of its GaN platform with four key factors in mind: reliability, drivability,

designability, and reproducibility,” says Kenny Yim, VP of Asia sales. “We’re proud that HZZH selected us as its

GaN partner as it affirms that those four factors are what our customers need to disrupt their markets. They result

in our GaN being designed into a wide range of multi-kilowatt power systems that are setting industry records,”

he adds. “We anticipate HZZH will continue to innovate as our collaboration continues on future products.”

Eta develops 4” semi-insulating GaN wafers SemiconductorToday

Eta Research of Lingang Free Trade Zone, Shanghai, China, which was founded in 2015 to develop free-standing

gallium nitride (GaN) wafers, has developed semi-insulating 4” GaN. The firm claims to be first to commercially

develop semi-insulating free-standing GaN wafers at this size.

Eta uses the hydride vapor phase epitaxy (HVPE) method to produce GaN wafers. To compensate the

unintentional n-type dopants, a deep-level co-doping strategy was used to achieve high resistivity. Whereas iron

doping has been the most prevalent choice for semi-insulating GaN, Eta uses carbon doping. Secondary-ion mass

spectroscopy (SIMS) data shows the carbon concentration to be in the range of 5E17–3E18/cm3. The

unintentional n-type dopants of oxygen and silicon are below 1E17/cm3. The resistivity has been measured by

Hall measurement and I-V curve, which result in room-temperature resistivity greater than 1E9Ω-cm.

The crystal and wafer quality specifications of the semi-insulating GaN wafers remains the same as the company’s

n-type GaN wafers. XRD rocking curves of both the (002) and (102) are <100 arcsec and typically 50–60 arcsec.

The dislocation density has been measured by cathodo-luminescence (CL) to be 1E6/cm2. The lattice radius of

curvature is greater than 10m. Total thickness variation (TTV) and bow can be controlled within 30μm for 100mm

wafers. The surface has an epi-ready polish with roughness <0.3nm for a 10μm x 10μm atomic force microscope

(AFM) measurement and <1.0nm for 239μm x 318μm optical interferometry measurement.

The market for semi-insulating GaN wafers is for RF HEMT devices. The RF device market is experiencing high

growth due to the implementation of 5G and other wireless communication applications. GaN is a useful

semiconductor material for high power and high frequency RF devices, but the industry is almost exclusively

producing GaN HEMTs on silicon carbide (SiC) substrates. GaN-on-GaN RF devices will have lower dislocation

density device layers and no buffer layer is required, so the firm expects that higher power and better

performance will result from RF devices made on GaN substrates.

“Due to the very limited supply, size and quality of semi-insulating GaN wafers, there has only been a limited body

of research work conducted on GaN RF devices grown homoepitaxially,” says CEO Troy Baker. “We plan to work

with customers to prove the value proposition of GaN wafers for RF devices. We are very optimistic about the

performance gains that could be made using semi-insulating GaN wafers,” he adds. “The wafers are currently

available for sale and the company is building new HVPE reactors with carbon doping capability. In addition, we

are able to provide MOCVD [metal-organic chemical vapor deposition] epi layers on GaN wafers.”

Each wafer will be shipped with a detailed wafer inspection form. Standard products are 2” and 4” wafers, and

customized sizes are available as well.

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EPC launches first product in new ePower Stage IC family SemiconductorToday

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA – which makes enhancement-mode gallium nitride

on silicon (eGaN) power field-effect transistors (FETs) for power management applications – has launched an 80V,

12.5A power stage integrated circuit designed for 48V DC-DC conversion used in high-density computing

applications and in motor drives for e-mobility.

The EPC2152 is a single-chip driver plus eGaN FET half-bridge power stage using the firm’s proprietary GaN IC

technology. Input logic interface, level shifting, bootstrap charging and gate drive buffer circuits along with eGaN

output FETs configured as a half-bridge are integrated within a monolithic chip. This results in a chip-scale LGA

form-factor device that measures only 3.9mm x 2.6mm x 0.63mm.

When operated in a 48V-to-12V buck converter at 1MHz switching frequency, the EPC2152 ePower Stage achieves

a peak efficiency above 96% with a solution that is 33% smaller in size on the printed circuit board (PCB) compared

with an equivalent multi-chip discrete implementation, it is reckoned.

The EPC2152 is the first offering in what will be a wide-range family of integrated power stages available in chip-

scale package (CSP) as well as multi-chip quad flat modules (QFM). Within a year the family will fill out with

products capable of operating at high frequency up to 3-5MHz range as well as high current from 15A to 30A per

power stage.

The family of products makes it easy for designers to take advantage of the significant performance improvements

made possible with GaN technology, says EPC. Integrated devices in a single chip are easier to design, easier to

layout, easier to assemble, save space on the PCB, and increase efficiency, the firm adds.

“Discrete power transistors are entering their final chapter. Integrated GaN-on-silicon offers higher performance

in a smaller footprint with significantly reduced engineering required,” says CEO & co-founder Alex Lidow. “This

new family of integrated power stages is the next significant stage in the evolution of GaN power conversion, from

integrating discrete devices to more complex solutions that offer in-circuit performance beyond the capabilities

of silicon solutions and enhance the ease of design for power systems engineers.”

The EPC90120 development board is a 80V maximum device voltage, 12.5A maximum output current, half-bridge

featuring the EPC2152 Integrated ePower Stage. This 2” x 2” (50.8mm x 50.8mm) board is designed for optimal

switching performance and contains all critical components for easy evaluation of the EPC2152 Integrated ePower

Stage.

The EPC2152 ePower Stage is priced at $5.03 each in 1000-unit volumes. The EPC90120 development board is

price at $123.75 each.

PiTrans project results in AlScN-based SAW resonators for smartphones SemiconductorToday

The ever-growing mobile data transfers in the wake of 5G require the use of more and higher frequency ranges,

all of which need to be accommodated within a single mobile device. The demands on radio frequency (RF)

components are hence constantly increasing. The Fraunhofer Institute for Applied Solid State Physics IAF of

Freiburg, Germany has developed novel, compact and energy-efficient high-frequency/high-bandwidth RF filters

to meet those needs (‘Enhanced electromechanical coupling in SAW resonators based on sputtered non-polar

Al0.77Sc0.23N (112-0)112-0 thin films’, Appl. Phys. Lett. 116, 101903 (2020)). During the project ‘PiTrans – AlScN

− Development of novel piezoelectric materials’ (running from 2015 to 2020) the researchers managed to grow

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aluminum scandium nitride (AlScN) with the required industrial specifications and to realize novel electroacoustic

devices for smartphones.

The amount of RF components built into a single smartphone has increased significantly over the past years and

there is no end in sight. Predicting this trend in 2015, the PiTrans project set out to develop and produce improved

RF piezo-transducers with ternary AlN-based nitrides as the piezo-active layer. Within the five years of the project,

the researchers succeeded in growing highly crystalline AlScN layers and realizing surface acoustic wave (SAW)

resonators that meet the increasing requirements of the industry.

For growth of the material, which is also promising for other power electronic applications, a modern magnetron-

sputtering infrastructure was established at Fraunhofer IAF. The project was funded by a ‘Fraunhofer Attract’

excellence stipend program and was successfully completed in January under the leadership of Dr Agnė

Žukauskaitė.

Potential and challenges of AlScN

AlScN remains the most promising new material to replace conventional aluminum nitride (AlN) in RF filter

applications inside mobile phones. By introducing scandium (Sc) into AlN, the electromechanical coupling and

piezoelectric coefficient of the material is increased, enabling a more efficient mechanical-to-electric energy

conversion. This allows the production of much more efficient RF devices. However, the instability of the

piezoelectric AlScN crystal phase has so far been a problem for industrial use of the material, as segregation of

wurtzite-type AlN and cubic ScN usually occurs during growth. “Back in 2015, we knew the potential of AlScN, but

we needed to find the right conditions to grow it in a stable and scalable process,” recalls Žukauskaitė.

Successful growth and device development

In the course of the project, the researchers at Fraunhofer IAF managed to grow highly crystalline AlScN layers

with a wide range of compositions up to a Sc content of 41%. Good homogeneity of the layers was achieved across

the entire silicon wafer up to 200mm in diameter, which meets the requirements of industrial productions.

Besides these industry-relevant results, the project team also succeeded in realizing epitaxial growth on lattice-

matched sapphire (Al2O3) substrates through a special magnetron sputter epitaxy (MSE) method of deposition,

which will be useful for future material research.

Picture: Piezoelectric properties of AlScN layers produced at IAF compared with results of other research

institutes. © Fraunhofer IAF


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In addition to the material development, the researchers produced three generations of test structures to

demonstrate the performance of the AlScN thin films. The implementation of MSE to produce AlScN/Al2O3-based

resonators yielded an electromechanical coupling increase of up to 10% at 2GHz frequency. In a collaboration

with the companies Evatec and Qualcomm, a non-polar AlScN thin film was also developed that further improves

the electromechanical coupling of SAW resonators. This technology is currently being further researched, and first

results have recently been published in a scientific paper.

AlScN for other applications

“We see AlScN as a very promising candidate for enabling future applications that capitalize on the piezoelectric

effect, such as sensor technologies and high-electron-mobility transistors [HEMTs],” says Žukauskaitė. The success

of the PiTrans project led to the acquisition of two further projects involving AlScN technology at Fraunhofer IAF.

In the project mAgnes, wide-bandgap current sensors (such as those used in e-cars) are being researched; and in

the project SALSA the research team is developing new types of switchable HEMTs. Both projects benefit from

the developed expertise in AlScN growth and AlScN-based device development as well as the necessary

infrastructure established at Fraunhofer IAF.

Transphorm and Microchip combine GaN and DSP technology SemiconductorToday

Transphorm Inc of Goleta, near Santa Barbara, CA, USA — which designs and manufactures JEDEC- and AEC-Q101-

qualified 650V gallium nitride (GaN) field-effect transistors (FETs) for high-voltage power conversion applications

— has announced a partnership to integrate the dsPIC33CK digital signal controller board of microcontroller

provider Microchip Technology Inc of Chandler, AZ, USA with its 4kW AC-to-DC bridgeless totem pole power factor

correction (PFC) evaluation board, which features the firm’s latest Gen IV GaN technology. Building on

Transphorm’s application support capabilities, Microchip’s worldwide technical support team will also be

available to developers working with the integrated Transphorm solution.

As a result, customers can access an evaluation board offering more than 99% efficiency and pre-programmed

firmware off the shelf, now backed with global support to further simplify AC-to-DC power system designs.

“The control requirements of GaN power systems using the bridgeless totem-pole power factor correction is

different than what is used to control traditional CCM boost PFCs which has long been a new challenge for some

ODMs,” says Philip Zuk, Transphorm’s VP of worldwide technical marketing and North American sales. “Two

industry leaders have partnered to reduce that knowledge gap,” he adds. “We’re giving customers access to a

disruptive GaN solution backed by a world-class global support team.”

Microchip’s dsPIC digital signal controllers (DSCs) are supported by a set of embedded design tools created to

empower developers, even those with limited expertise. These tools provide intuitive graphic user interfaces for

device initialization in Microchip’s free MPLAB X Integrated Development Environment. The software tools are

complemented by a full line of programmer, debugger and emulator accessories.

The DSC-integrated solution is used in Transphorm’s TDTTP4000W066C-KIT, featuring:

• 650V 35mΩ Gen IV GaN FET (TP65H035G4WS);

• input voltage: 85-265VAC, 47-63Hz;

• input current: 18Arms; 2kW at 115VAC, 4kW at 230VAC;

• output voltage: 387VDC ± 5VDC (programmable);

• deadtime: programmable;

• PWM frequency: 66kHz;

• power factor: >0.99.


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The evaluation board is designed around Microchip’s dsPIC33CK digital power plug in module (PIM) to control the

PFC powertrain. The kit includes a pre-programmed PIM that features:

• Microchip’s AEC-Q100-qualified dsPIC33CK256MP506 digital signal controller;

• 100MIPS for faster deterministic performance in time-critical control applications;

• Dual Flash Panels – to enable live update of code while power supply is running;

• High analog integration for reduced BOM costs and minimum system size;

• PWMs with 250ps resolution.

Firmware updates for the dsPIC33CK PIM will be available for download from Microchip’s website.

“Microchip’s dsPIC DSCs are designed to meet the demanding control needs associated with newer digital power

topologies,” says Joe Thomsen, Microchip’s vice president of MCU16. “We are proud to work alongside a

likeminded industry disruptor, Transphorm, to provide our customers this reference design including

Transphorm’s proven GaN devices. Our dsPIC33CK PIMs will offer engineers the flexibility and worldwide support

that many designers need for their high-power solutions.”

The TDTTP4000W066C-KIT is available through Digi-Key and Mouser.

Transphorm customers currently working with the prior-generation evaluation board — the TDTTP4000W066B-

KIT — can still take advantage of the dsPIC33CK PIM integration by contacting Transphorm for a conversion

daughter card.

EPC issues 11th reliability report SemiconductorToday

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA – which makes enhancement-mode gallium nitride

on silicon (eGaN) power field-effect transistors (FETs) for power management applications – has issued its Phase

Eleven Reliability Report, documenting the strategy used to achieve its field reliability record. This strategy relied

on tests forcing devices to fail under a variety of conditions to create stronger products to serve demanding

applications such as LiDAR for autonomous vehicles (AVs), LTE base stations, vehicle headlamps, and satellites.

Testing devices to the point of failure creates an understanding of the amount of margin between data-sheet

limits and products in application. More importantly, intrinsic failure mechanisms of devices are identified. The

knowledge of these intrinsic failure mechanisms is used to determine the root cause of failures. Knowledge of the

behavior of a device over time, temperature, electrical or mechanical stress can provide users with an accurate

representation of the safe operating life of a product over a more general set of operating conditions.

The report is divided into seven segments, each dealing with a different failure mechanism:

Section 1: Intrinsic failure mechanisms impacting the gate electrode of eGaN devices.

Section 2: Intrinsic mechanisms underlying dynamic RDS(on).

Section 3: Safe operating area (SOA).

Section 4: Testing devices to destruction under short-circuit conditions.

Section 5: Custom test to assess reliability over long-term LiDAR pulse stress conditions.

Section 6: Mechanical force stress testing.

Section 7: Field reliability.

“eGaN devices have been in volume production for over ten years and have demonstrated very high reliability in

both laboratory testing and high-volume customer applications,” says CEO & co-founder Dr Alex Lidow. “The

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release of EPC’s 11th reliability report represents the cumulative experience of millions of devices over a ten-year

period and five generations of technology [amounting to 123 billion device hours]. These reliability tests have

been undertaken to continue our understanding the behavior of GaN devices over a wide range of stress

conditions,” he adds.

“The results of our reliability studies show that GaN is an extremely robust technology that continues to improve

at a rapid pace,” Lidow continues. “EPC is committed to subjecting GaN devices to rigid reliability standards and

sharing the results with the power conversion industry.”

OPTOELECTRONICS

Everlight launches UVC LED series for medical treatment, water and air purification/sterilization SemiconductorToday

Taiwan-based Everlight Electronics Co Ltd has launched its ELUC3535NUB series of UVC LED products, which use

epitaxial and flip-chip technology on a sapphire substrate, for sterilization applications.

Popular markets for UV applications are curing, medical treatment, photocatalyst and counterfeit testing.

Recently, rapid growth of demand in UV markets has been seen, especially in air purification and the sterilization

of standing or running water. Everlight has invested in LED technology for many years and has developed UVA

and UVC products. There are already existing 2016, 3535 and 4545 packages for UVA (UV black light radiation,

360-410nm) including low to high wattages and several kinds of emitting angles for individual customer options.

Packaged in inorganic quartz glass with an emission wavelength of 280nm, the new ELUC3535NUB UVC LED Series

(3.5mm x 3.5mm x 1.4mm) spans three different intensity levels (2mW, 10mW and 30mW), making it suitable for

applications such as medical treatment, water or air purification and sterilization of germs, viruses or mold.

Furthermore, the ELUC3535NUB LEDs can be used for deodorizing and bactericidal treatment, when installed for

example in a modern smart toilet. A similar effect can also be achieved by using the firm’s UVA3535 (1.8W, 120℃)

LEDs in combination with titanium dioxide (TiO2).

Plessey extends Data-Vµ micro-LED product family with passive-matrix micro-display SemiconductorToday

UK-based Plessey, which develops embedded micro-LED technology for augmented-reality and mixed-reality

(AR/MR) display applications, has added passive-matrix micro-LED displays to its Data-Vµ product family.

Following the launch of its Data-Vµ segmented micro-LED display

products in 2019, Plessey has now extended the range with the

introduction of passive-matrix pixelized micro-LED displays, based

on the firm’s proprietary monolithic gallium nitride on silicon (GaN-

on-Si) technology.

These fully addressable micro-displays can provide the high-

brightness/low-power image source demanded by the advanced

compact optical projectors embedded in AR/MR information

systems. The displays can be customized to provide the specific resolution and color that customers require to

present their dynamic content specific to their applications. These applications can take advantage of the high

brightness and contrast inherent in Plessey’s micro-LED technology to produce visual images that can be viewed

under a wide range of environmental conditions and at low power consumption.

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Plessey has demonstrated its first monochrome passive-matrix micro-LED display with a resolution of 48 x 36

monochrome pixels using its native technology capability and a new pixel architecture that improves light

extraction. The roadmap for this platform includes the development of higher-resolution displays up to 128 RGB

x 128 (or 384 x 128 monochrome) by the end of 2020.

“Micro-LED displays are now the go-to technology for next-generation developments requiring power-efficient

and ultra-bright displays,” says senior micro-LED product sales manager Leon Baruah. “With the introduction of

our Data-Vµ passive-matrix displays, applications where dynamic content needs to be displayed in a small form

factor that is outdoor readable without compromising on battery life have become reality.”

The Data-Vµ passive-matrix displays are designed to be driven from a driver IC, requiring no active-matrix

backplane. The drive architecture, along with its small form factor, makes the Data-Vµ passive-matrix displays a

suitable and cost-effective solution for AR smart glasses and head-mounted displays for navigation, sport &

leisure, wearables and optical instruments where dynamic content can be displayed, reckons Plessey.

Bridgelux launches eighth generation of COB LEDs, deliver 185lm/W efficacy at 3000K 80 CRI SemiconductorToday

Bridgelux Inc of Fremont, CA, USA (a vertically integrated manufacturer of solid-state light sources for lighting

applications) has announced its eighth generation of chip-on board (COB) LED products, delivering luminous

efficacy of up to 185lm/W across its V Series, Vero Series and Vero SE Series families at nominal drive current.

This performance is benchmarked at the popular 3000K 80 CRI (color rendering index) point, with efficacies above

200lm/W possible at other color points across the industry’s broadest range bof COB products.

In addition to reclaiming the industry lead in COB efficacy, it is claimed, the products have the following additional

features:

• nominal light output optimized to align with traditional lamp standards;

• standard warranty of up to 10 years;

• efficacy improvements of up to 10% compared with previous product generations;

• up to 3x overdrive capability, delivering a 30% increase in maximum lumens per LES (light-emitting

surface) size;

• increased lumens per dollar, further reducing the cost of solid-state lighting;

• optical and mechanical consistency with previous generations, enabling a seamless upgrade path

leveraging existing ecosystem components;

• broad range of COB size and performance options from LES 8mm to LES 29mm;

• improved alignment with industry-standard drive currents, enabling the use of economical LED drivers to

further reduce costs;

• technologically equivalent with existing Bridgelux seventh-generation COB LM-80 data.

With more efficient light sources available for an entire lighting ecosystem, customers are now better equipped

to meet evolving energy standards and rebate incentive programs without compromises in quality of light, says

the firm.

In addition launching new Gen 8 products, Bridgelux continues to expand its portfolio of human-centric lighting

solutions. New products under development include the new Vesta Thrive COB (said to be the first tunable white

natural-spectrum light source); expansions in the Vesta Flex dual-channel driver and controls family to now

include Casambi and Silvair control modules; and the new Vesta SE (the first dim-to-warm and tunable white COBs

with integrated holders to simplify and standardize mechanical, optical, and electrical connections).

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“The lighting market continues to evolve, with some suppliers reducing their focus on lighting,” says CEO Tim

Lester. “Bridgelux is a technology partner for our customers that remains committed to lighting. Our expanded

portfolio further enhances our ability to support our customers in navigating the market transition toward human-

centric lighting, the right light, in the right place, at the right time,” he adds.

Bridgelux Gen 8 products are available now for sampling and ordering, with production shipments commencing

in April.

Aluminium gallium nitride on silicon carbide for ultraviolet diodes SemiconductorToday

University of California Santa Barbara (UCSB) in the USA has been using silicon carbide (SiC) substrates to grow

aluminium gallium nitride (AlGaN) structures aimed at 278nm deep ultraviolet (UV-C, 100-280nm wavelength)

light-emitting diodes (LEDs) [Burhan K. SaifAddin et al, ACS Photonics, published online 27 January 2020]. The

researchers used surface roughening of thin-film flip-chip devices to boost light-extraction efficiency (LEE) by a

factor of 3 over smooth-faced LEDs.

“The ability to grow AlGaN LEDs on SiC with low TDD [threading dislocation density] opens new ways to fabricate

high-brightness, high-power UV LEDs with high LEE,” the team comments. The 260-280nm wavelength range

enables efficient disinfection by breaking up DNA and RNA molecules of pathogens. The researchers are keen to

combat antibiotic-resistant bacteria such as Clostridium difficile (C. diff.), which is indeed difficult to kill using

chemical methods. By contrast, UV disinfection reduced C. diff. levels by 30%, according to University of North

Carolina researchers in 2010.

Fabricating efficient UV-C LEDs has been challenging due to a number of factors. Material quality can be improved

by using SiC rather than sapphire, due to a closer lattice and thermal expansion match. However, UV-C light is

strongly absorbed in SiC, unlike sapphire, due to its narrower bandgap. Indeed, sapphire is often used for UV-C

LEDs for this reason.

Low-pressure metal-organic chemical vapor deposition was carried out on 2-inch 6H SiC on the silicon face of a c-

plane (0001) crystal orientation. The AlGaN layers began with a 3.2μm AlN buffer grown in steps at 1200°C and

1000°C (Figure 1). The Al content was reduced with an 1100nm Al0.80Ga0.20N interlayer, and then 550nm n-

Al0.60Ga0.40N grown at 1175°C. The multi-quantum well (MQW) region consisted of four pairs of 2.7nm/9nm

Al0.39Ga0.61N/Al0.60Ga0.40N wells/barriers. The structure also included an AlGaN electron-blocking layer (EBL).

Figure 1: (a) Schematic of the UV−C LED structure. (b) APT 3D reconstruction of active layer showing EBL layer

and four MQWs; (c) 1D concentration profile extracted from APT reconstruction along [0001] direction.

Sampling volume dimension 20nmx20nmx50nm from dotted rectangle in (a).

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The AlN buffer was crack-free due to a “novel substrate pretreatment” (annealing in ammonia/hydrogen at

1250°C) and a multi-step 3x(3D/2D) growth process reported by UCSB in 2018. The AlN buffer also achieved a

reduced threading dislocation density of ~109/cm2.

The researchers used atomic probe tomography (APT) to study the material, in what the team claims was its first use on UV-LED structures.

The material was then fabricated into thin-film flip-chip devices in TO-39 headers. The SiC growth substrate was

removed using a sulfur hexafluoride plasma etch. The team used potassium hydroxide solution to roughen the

flipped AlN light-emission surface, increasing light output by reducing reflection back into the LED material. Also,

the p-GaN thickness was reduced as much as possible, since the material is absorbing of UV-C radiation. These

two measures, along with increasing the reflectivity of the p-contact, are estimated to increase the light-extraction

efficiency by a factor of 3 over smooth-surface devices.

Figure 2: (a) EQE as function of current density for different 278nm UV LEDs processed from same epitaxial

sample. (b) Unflipped UV LED on SiC schematic with p-side up. (c,d) Thin-film flip-chip (TFFC) UV LED (area

~0.1mm2), (c) before and (d) after surface roughening.

At 95mA injection current, the roughened UV-C LED had 7.6mW (82mW/mm2) light output power and 1.8%

external quantum efficiency. The slope efficiency was 89μW/mA. The turn-on voltage was 4.3V. The LEE was

estimated at 33%, the highest reported for AlGaN LEDs, the team claims.

Indium tin oxide as cladding for more efficient green laser diodes SemiconductorToday

Researchers based in China have used indium tin oxide (ITO) as an upper cladding component in green laser diodes

(LDs) rather than the more usual aluminium gallium nitride (AlGaN), reducing thresholds to as low as 1.6kA/cm2

[Lei Hu et al, Photonics Research, vol8, p279, 2020]. A conventional AlGaN-clad laser diode with the same

structure otherwise achieved a threshold of 5kA/cm2.

The team from Suzhou Institute of Nano-Tech and Nano-Bionics and University of Science and Technology of China

hope to use their work to fill the ‘green gap’ for efficient laser diodes between the near-infrared to red range, and

the blue to near-ultraviolet. The central range of the gap is 500-550nm wavelength range. At the same time, these

wavelengths are in the center of the visible spectrum, 380-794nm, and hence are key in red-green-blue display

applications.

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The low refractive index of ITO (about 2) should enable better confinement of the light generated in the laser

cavity, compared with higher-index AlGaN. Also, ITO deposition is a relatively low-temperature process (around

300°C), which reduces thermal damage to the indium gallium nitride (InGaN) multiple quantum wells (MQWs)

that generate the green light.

The researchers designed three laser diode structures with varying p-Al0.08Ga0.92N cladding thickness, which

were grown by metal-organic chemical vapor deposition (MOCVD) on c-plane GaN substrates (Figure 1). The

cladding thicknesses were 150nm, 300nm and 500nm. The cladding was actually deposited as a 2.5nm/2.5nm p-

AlGaN/p-GaN superlattice (SL) with 8% average Al content, with the aim of reducing series resistance.

Figure 1: Hybrid laser diode with ITO cladding layer or conventional laser diode with Pd/Pt/Au electrode.

The n-side cladding was designed to consist of Al0.07Ga0.93N. The InGaN waveguide layers had 4% indium

content on the n-side and were unintentionally doped on the p-side. The electron-blocking layer (EBL) contained

15% Al.

The material was processed into ridge-waveguide laser diodes with inductively coupled plasma (ICP) etch, 200nm

silicon dioxide ICP CVD, and 200nm ITO evaporation at 300°C. The p-electrode metal was titanium/gold, while the

n-contact was through titanium/aluminium/titanium/gold deposited on the back of the wafer. A conventional

laser diode without ITO was fabricated on a 500nm p-AlGaN cladding sample, where the p-electrode consisted of

palladium/platinum/gold (Pd/Pt/Au). The laser diode cavities were formed by cleaving the fabricated devices and

coating the facets with dielectric layers.

The devices were subjected to 0.4μs current pulses at a rate of 10kHz with a view to eliminating self-heating

effects. The threshold of the conventional laser diode without ITO came in at 5kA/cm2 current density. The slope

efficiency of the light output power was 0.16W/A.

The ITO device with the thinnest AlGaN cladding of 150nm reduced the threshold to 2.5kA/cm2. The sloped

efficiency increased to 0.20W/A. The intermediate cladding laser diodes also showed reduced thresholds to a

lesser extent. The 300nm-clad laser diode also showed increased slope efficiency of 0.19W/A.


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The light output wavelengths were just above 500nm: 506nm, 512nm and 508nm, for the ITO laser diodes with

500nm, 300nm and 150nm p-AlGaN cladding, respectively. The conventional device wavelength was 505nm. The

researchers attribute the wavelength variation to different MOCVD growth temperatures. These values are

toward the blue end of the 495nm-570nm green range.

Studying the subthreshold light emission suggested increased non-radiative recombination in the samples with

thicker p-AlGaN cladding. The researchers comment; “We believe that the increasing non-radiative recombination

centers result from the increasing thermal budget due to increasing growth time of the p-AlGaN cladding layer.”

AlGaN is generally grown at raised temperature that tends to degrade the InGaN in the light-emitting MQWs and

the waveguide layers. The team points particularly to the extended growth time at high temperature as damaging

to the QW structure.

Simulations suggest that the lower light absorption of the ITO cladding material is not a particularly significant

factor in reducing the threshold, except in so far as it enables a thinner p-AlGaN cladding layer.

The team also carried out simulations that suggested that reducing the Al content in the p-AlGaN cladding to 3.5%

could improve hole concentration and injection efficiency, further reducing thresholds. A laser diode was

fabricated with 300nm 3.5% Al-content p-cladding, and the threshold was reduced to 1.6kA/cm2. This compared

with 2.9kA/cm2 for the 300nm 8%-Al cladding laser diodes. Also, the slope efficiency increased slightly from

0.19W/A to 0.20W/A.

Figure 2: (a) Light output power versus current density curves for ITO laser diodes with 300nm p-AlGaN

cladding layers with 8% and 3.5% Al-content. (b) Current density versus voltage for 3 different laser diodes.

The 3.5%-Al cladding laser diode also showed reduced operating voltage of 0.6V lower than the conventional laser

diode with 4kA/cm2 injection current density. This indicated reduced series resistance from the thinner AlGaN.

The researchers used the improved performance to construct a laser diode with 400mW light output power. The

high performance was enabled by a 15μm-wide, 1200μm-long ridge with the front facet reflectivity reduced to

40%. The threshold current density was 3.9kA/cm2. The slope efficiency was 0.44W/A, and the current injection

at 400mW output was 9kA/cm2.


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KONKA enters micro-LED pilot production with Aixtron AIX G5+ C and AIX 2800G4-TM MOCVD systems SemiconductorToday

Deposition equipment maker Aixtron SE of Herzogenrath, near Aachen, Germany says that China-based KONKA

Group Co Ltd has ordered multiple AIX G5+ C and AIX 2800G4-TM metal-organic chemical vapor deposition

(MOCVD) systems to build its own volume production of gallium nitride (GaN)-based and arsenide-phosphide

(AsP)-based mini- and micro-LEDs. KONKA, which recently announced its plans to enter the North American

consumer electronics market in 2020, established its micro-LED initiative as a joint venture with Chongqing

Liangshan Industrial Investment Co. Most recently, the Chinese electronics manufacturer has launched its Smart

Wall micro-LED TV.

Micro-LED technology is on the verge of superseding existing display technologies for next-generation consumer

products. Since displays made of micro-LEDs consist of micron-sized LED arrays forming individual sub-pixel

elements, they offer the lowest power consumption while simultaneously exhibiting superior pixel density,

contrast ratio and brightness. Compared with existing LCD and OLED technologies, micro-LEDs open new

opportunities for the design of consumer mobile products as well as premium TV displays.

“Aixtron’s market-leading fully automated MOCVD tools AIX G5+ C and AIX 2800G4-TM perfectly meet our

tightened wavelength uniformity requirements for micro-LED manufacturing,” comments Dr Allen Tsai, general

manager & CEO at Chongqing KONKA Optoelectronics Technology Research Institute Co Ltd. “The advanced

Planetary technology stands out due to excellent wavelength uniformity, high yield and efficient high-volume

manufacturing at lowest cost per wafer. Besides our commercial market entry for micro-LED applications,

Chongqing KONKA and Micro Crystal Transfer Group will develop new technologies and applications based on

GaN materials,” he adds.

“Following the recent qualification of our AIX G5+ C tool for micro-LED production means another step forward

in the commercialization of our system technology for micro-LED manufacturing,” says Aixtron president Dr Bernd

Schulte. “We are looking forward to the further cooperation with KONKA,” he adds. “Aixtron will continue to

support the joint effort between Chongqing KONKA and Micro Crystal Transfer Group for their development of

new technologies and applications based on GaN materials.”

Plessey to Work with Facebook on Micro LED Display Technology for AR/VR Applications LEDInside

Plessey, the UK-based Micro LED display developer focusing on AR/MR display

application, announced that it is collaborating with Facebook, providing its

technology to support Facebook building prototype and develop new

technologies for potential use in the AR/VR space. Plessey has been focusing on

Micro LED-based AR display technology and it was rumored that Apple had plan

to acquire Plessey with its interest in AR smart glasses. However, now Plessey

teams up with Facebook and will license its technology to the social media giant

for creating innovative applications based on AR/VR/MR technologies.

Dr Keith Strickland, co-CEO and CTO of Plessey, said, “We are delighted to announce this new commercial

agreement with Facebook. Plessey has been at the forefront of Micro LED display development and this

agreement recognizes the significant advances in our capabilities that we have made in recent years and we very

much look forward to working with Facebook to help bring their vision to life.”

Facebook has been interested in AR technology for long. The company acquired VR headset maker Oculus VR in

2014 and purchased computer vision startup Scape Technologies to set up AR capability. It is said that Facebook

aims to release AR wearable product between 2023 and 2025.

http://www.semiconductor-today.com/news_items/2020/mar/aixtron-170320.shtml

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Bringing Micro LEDs to the Dimensions of the Silicon Industry with ALLOS’ 200 mm and 300 mm GaN-on-Si Epiwafers LEDInside

To address the wafer size mismatch and to tackle the yield challenge in Micro LED production, ALLOS has applied

its unique strain-engineering to show outstanding uniformity and reproducibility for 200 mm GaN-on-Si epiwafers.

Additionally the company reports about its success on the roadmap to 300 mm.

Yield plays a crucial role to make Micro LED displays successful. It has a direct impact on the manufacturing

complexity and cost. To enable the needed cost reductions, large wafer diameters are essential. This is particularly

true for Micro LED applications in which wafers from CMOS-lines are integrated with LED epiwafers, e.g. by

bonding. Here the matching wafer diameter even has an enabling role comparing to the smaller diameters

available from GaN-on-sapphire. The ALLOS team has already used its unique strain-engineering technology to

push the wavelength uniformity further and further, showing 200 mm GaN-on-Si LED epiwafers on Veeco’s Propel

with STDEV of as little as 0.6 nm in February 2019.

With its latest results, ALLOS can now show excellent reproducibility for this technology with a wavelength

uniformity of consistently below 1 nm STDEV for 200 mm. “At the same time we achieve all other production

requirements like bow of < 40 µm and SEMI-standard thickness of 725 µm. These parameters are very important

when bonding CMOS wafers to LED epiwafers,” is added by Alexander Loesing, one of the co-founders of ALLOS,

who continues, “These results are particularly impressive because our technical team is really pushing the

boundaries of GaN technology only with very limited time and resources available for this work.”

Figure 1: (Left) Reproducibility of wavelength uniformity on 200-mm GaN-on-Si epiwafers for Micro LED

application, (Right) 300-mm epiwafers for Micro LED.

Commenting on the achievement, Dr. Atsushi Nishikawa, the CTO of ALLOS pointed out: “Already our predecessor

company AZZURRO had been first in the market with commercial 150 mm and later 200 mm GaN-on-Si epiwafer

products. Making 300 mm was the next natural challenge. When the first reactor designed for such large wafers,

the Veeco ImPulse, became available we proceeded to tackle the challenge.”

ALLOS confirmed that its technologies scale successfully to 300 mm on this new reactor. In particular, ALLOS’

unique technologies for strain-engineering and superior crystal quality work on 300 mm as expected.

“Being among the first to push III/nitride technology to 300 mm is very exciting for us. It proves how robust our

strain-engineering technologies are and we are looking forward to establish this technology for Micro LED

customers” is added by Nishikawa, who is also one of the co-founders of ALLOS.

https://www.ledinside.com/news/2020/3/allos_microled


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Scaling up from 100 mm diameter – the typical wafer dimension for GaN-on-sapphire – has an even bigger

business impact for Micro LEDs than in other parts of the LED industry. Beside the well-known effects of lower

cost per area when using larger diameters, the jump to 200 mm and 300 mm GaN-on-Si for Micro LED production,

enables the usage of CMOS facilities that have a much lower cost and additionally higher production accuracy

than conventional LED lines. A further effect arises because most Micro LED manufacturing concepts either

include mass transfer technologies that are using large area transfer-stamps or monolithically integrated displays:

Figure 2: Scaling wafer dimensions: Additional cost benefit by better area utilization due to matching

rectangular shape of display or transfer stamp to circular shape of wafer.

Summarizing the 300 mm advantages, Loesing concludes, “For Micro LED displays the better area utilization of

larger wafer sizes can easily account for 40 % cost advantage from 300 mm epiwafers for this step alone. Together

with the other cost advantages and the production benefits offered by CMOS lines this results in leading industry

players evaluating Micro LED displays based on 300 mm GaN-on-Si.”

Seoul Viosys and UCSB Find the Characteristics of Green and Blue InGaN Micro LEDs down to 1 μm LEDInside

A team with researchers at Seoul Viosys and University of California Santa Barbara (UCSB) published a study

focuses on features of Micro LEDs as their size goes smaller at 1 to 10 μm.

External quantum efficiency (EQE) of Micro LEDs usually reduces when Micro LEDs get smaller, which becomes an

issue for Micro LED technology builders. To further understand the relation between EQE and chip size, a research

team of Seoul Viosys and UCSB focus on Micro LEDs down to 1 μm to compare the EQE trend for blue and green

InGaN Micro LEDs.

The team published their results on Applied Phyics Letter in February 2020, titled “Comparison of size-dependent

characteristics of blue and green InGaN microLEDs down to 1 μm in diameter.”

The team addressed that they only utilized standard semiconductor processing techniques to develop the down

to 1 μm InGaN Micro LEDs for the study. They compared blue and green InGaN Micro LEDs and found that green

https://www.ledinside.com/news/2020/3/microled_eqe


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LEDs were more efficient than blue LEDs when they turn smaller than 10μm, meaning that green LEDs were less

affected by the size in EQEs.

With the results, researchers also proposed that red InGaN Micro LED may be an approach when manufacturing

smaller size full color Micro LED devices.

Based on the study, the team hopes InGaN Micro LEDs with increased brightness and reliability in smaller size can

lead to advanced display applications for smartphones, AR glasses and 4K TVs, according to the report covered by

Semiconductor Today.

The team also claimed that it is the first study of Micro-LED EQE trends for mesa dimensions below 5μm, despite

commercial demands.

China Companies to Order Equipment for Micro LED Production LEDInside

The spreading coronavirus epidemic did not stop industry players from

progressing advanced technology development. Chinese companies

recently reported new orders and subsidies for equipment to push Micro

LED technology development.

The biggest LED wafer and chip producer Sanan Optoelectronic reported

that its subsidiary Sanan Semiconductor has received subsidies from the

Quanzhou government in March for purchasing equipment. The amount

of the subsidies was RMB 143 million (US$ 20.16 million). Sanan

Semiconductor has formed partnership with TCL to establish a joint

laboratory for Micro LED development in the beginning of March.

The other China company, the Konka Group, has also ordered several equipment from Germany’s AIXTRON for

Micro LED pilot production. According to AIXTRON, Konka will use the tools to set up production line of GaN-based

and AsP-based Mini- and Micro LEDs.

https://www.ledinside.com/news/2020/3/china_microled_production


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Micro LED + LiDAR, the Key Technologies for Apple to Push AR Products and Applications? LEDInside

AR applications and devices are one of the major focuses of Apple at the moment. The company has shown its

interests in AR technology development and considered that AR wearable glasses may replace smartphones in

the near future. Rumors about Apple to reveal its AR smart glasses soon have been going on as well.

Apple launched the new iPad Pro adopting LiDAR Scanner and releases the latest ARKit 3.5 which enables app

developers to take advantage of the new LiDAR Scanner to capture 3D features of the surrounding environment.

ARKit 3.5 also includes instant AR objects placement, improved motion capture and people occlusion for more

diverse applications.

The LiDAR Scanner adopted iPad Pro is regarded as the first product for Apple to march towards the AR field. It is

also expected that the new iPhone scheduled in September 2020 will equipped with full 3D sensing solution to

further expand Apple’s AR equipment.

Meanwhile, AR smart glasses are considered the target product which Apple has continued the development.

Apple is reportedly progressing its AR smart glasses with optical sensor developers. In addition, the report of

MacRumors noted that the leaked code from an internal version of iOS 14 indicated Apple’s testing on its new

AR/VR headsets.

Based on the recently unveiled patents of Apple, the company is likely

to build their AR smart glasses based on Micro LED technology. Micro

LED with high brightness, high resolution and low power consumption

may enable flexible design and light weight wearable products.

According to Bloomberg’s report in October 21, 2019, Apple might introduce AR headset that pairs with the new

5G iPhone or other portable devices. Since Apple introduced the new iPad Pro with LiDAR and technology is also

anticipated to come with the new iPhone, these devices may be supporting Apple’s smart glasses in the further

to intensify advanced AR applications.

Ecosense Acquires Assets from Soraa LEDInside

U.S.-based LED technology company Ecosense announced that it has acquired assets from Soraa, co-founded by

Nobel Laureate Shuji Nakamura focusing on full-spectrum LED lamps.

Under the terms of the deal, Ecosense acquires the Soraa name, intellectual property and lamps, including the

company's signature VIVID, BRILLIANT™ HL and HEALTHY™ product lines. This move is the first foray into the

professional lamp category for Ecosense.

"This acquisition accelerates our strategy into the next wave of lighting," explained Mark

Reynoso, CEO of Ecosense. "Soraa has an unparalleled reputation for beam and spectral

quality. Their intellectual property and technology portfolio—including ZEROBLUE™, full

spectrum, and healthy lighting—highly complements our own intellectual property and

related technologies. We will prioritize enhancing and accelerating their antibacterial

technology to market."

Nakamura commented, "Soraa is a pioneer in full spectrum and circadian lighting.

Combining with Ecosense, we significantly expand our leadership and intellectual

property rights in these and related fields. We are excited about our next phase of growth together."

To maintain consistency and quality of service, Soraa will continue to operate as its own distinct brand.

https://www.ledinside.com/news/2020/3/ar_apple_lidar_microled

https://www.ledinside.com/news/2020/3/soraa_ecosense


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VerLASE Introduces Novel Mass Transfer Technique for Micro LED Displays LEDInside

Micro LED technology builder VerLASE introduced a novel mass transfer technique for Micro LED display

production based on its “Large Area Assembly Platform” (LAAP), which the company revealed in June, 2019. With

similar concept, the company transfer the technology into a simpler, semiconductor-fab compatible solution

based on Photo-Mechanical Actuation (PMA).

According to VerLASE, the solution uses a novel formulation comprising of fab compatible chemistries and transfer

stamp architecture in a unique way to deterministically pick-up a large number of microdies, translate them to

the desired drop-off location on a substrate and then dispense them with very high accuracy and speed. This

microdie dispensing can be done globally or locally by individually addressing microdies, as programmed.

Simplistically, the Transfer Stamp follows a 3-ply construction: a thin transparent substrate, a patterned PMA

formulation, and a stiffer material dubbed “Barrier Ribs” surrounding the patterned PMA formulation as

illustrated below:

The substantially transparent and flexible Transfer stamp allows for accurate alignment with the donor LED source

wafer and the microdies held on it, as well as the receiving target interposer or display backplane.

VerLASE noted that the solution can work with different ways to pick up the microdies while it used a proprietary

method. And the dies dispensing is accomplished by either flood or selective exposure of the PMA material in the

Transfer Stamp to light. The novel photo-reactive chemistry undergoes light induced physical contraction under

illumination by a light source.

As the PMA material contracts under this light illumination pulling the attached microdies with it, the “Barrier

Ribs” act as a hard, physical stop forcing the bonding interface holding the microdies to the PMA material to give

way, thus releasing the microdies. The bonding strength of the microdie / PMA material interface can be varied

as necessary such that it is low enough for detaching the microdie without the microdie structurally failing.

https://www.ledinside.com/news/2020/3/verlase_microled_masstransfer


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Existing exposure tools coupled with binary chrome photo masks and scanning low power laser systems allow for

a highly multiplexed, addressable mass release of microdies or local dispensing of microdies as desired.

PMA material formulations being investigated at this time are Photo-Actuated, primarily single use chemistries,

but other options could also be applied with future development.

A full wafer transfer stamp as illustrated above, scalable to 6 inch or larger, can be constructed with existing

tooling with very high precision at low cost. Cost of scaling, replicating and having a variety of SKUs is incremental,

allowing for a wide variety of display patterns and pitches to be serviced.

Furthermore, the Transfer stamp, once constructed, can be mated and used with minimally modifying existing,

semiconductor equipment. The full wafer transfer stamp should allow for the mass transfer of microdies on the

order of less than 5μm.

As a full wafer transfer stamp and at microdie sizes of less than 5 μm, transfer rates in excess of over 10 million

microdies per unit transfer event should be routinely possible, enabling a wide variety of display resolutions and

display sizes to be economically manufactured.

VerLASE expects to produce displays with above 400 ppi for smartphone sizes with the method which achieves

high thruputs and with provisions for in-line metrology and in-process repair.

Global LED Companies Launch UVC LED Products to Meet Growing Demands LEDInside

The coronavirus has now declared a worldwide pandemic by the World Health

Organization and the infected numbers continues to rise all over the world. Products

used for preventing infection thus became bestsellers everywhere. Featuring

disinfecting function, UVC LED embedded products are also drawing attentions in

the market. LED companies who have been progressing UV LED technologies now

leverage their strengths to launch UV LED products for meeting the surging

demands for disinfection applications.

Lextar, the vertical integrated LED company based in Taiwan, debuted new UV LED packages in January 2020.

With proprietary optical design, the products can concentrate power and optimize disinfection efficiency. UVC

LED products with 15mW and below are used in disinfecting water bottle while the PU88 series can be applied in

daily necessities disinfection such as cutleries, tooth brushes or pacifiers.

EVERLIGHT also launched its UVC LED series products in 1Q20. Power range of its 280nm UVC packages covers

2mW/10mW/30mW and can effectively diminish E.coli and Staphylococcus aureus. The UVC LEDs can be

embedded in portable products such as disinfection box or flash light for killing microorganisms on phones, glasses

and other. UVC LEDs integrated with UVA products in smart toilet also enable both disinfection and deodorization.

Another Taiwan-based UV LED expert, High Power Lighting (HPL) continues its

collaboration with clients and will introduce UVC LED equipped air conditioners

this year. In addition, the company developed a flowing water disinfection module

under that brand Bioraytron, the joint brand of HPL and Epileds. With its unique

optical design, the water disinfection module achieves a disinfection rate of

99.99% based on a single 20mW UVC LED chip in 3L/min.

https://www.ledinside.com/node/31145


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Lite-On’s UV-C LEDs have a peak wavelength at 275nm with SGS certificated dust and water proof at IP 58 and

99.99% (Log4) disinfection rate to meet the requirements of different sterilization products. The UV LEDs can

effectively prevent the growth of E.coli and staphylococcus aureus while diminish different types of bacteria and

viruses effectively under different radiation and time.

The company has worked on UVC LED technology for many years with a completed product

lines with proprietary packaging technique, providing excellent brightness and life stability.

Lite-On’s UVC LEDs are adopted by leading electronics brands in Europe, the U.S., Japan

and Korea for household sterilization. In response to the current needs of epidemic

prevention, portable sterilization products developed by small and medium manufacturers

such as drinking water sterilization, portable sterilization, car air purifier, has boosted sales

volume three time higher compared to the sales last year. Demand is expected to continue

growing as people all over the world are combating the coronavirus epidemic.

The UV LED subsidiary of Seoul Semiconductor, Seoul Viosy,

recently announced that its inquiries for UV LED products

has increased more than five times compared to previous

month. Lifetime of its Violeds UV LED products was

improved to more than 50,000 hours; and the technology

has been adopted by NASA for disinfection on the

International Space Station. Also some Chinese automotive

companies are evaluating the possibility of using Seoul’s

violeds UV LED technology in sterilization systems for vehicle

interiors.

Violumas, the UV division of Flip Chip Optounder the Cofan Group, focuses on high power UVC LED technology

and aims to double the power of its UVC LED products this year. The company has worked with its clients on a

wide range of disinfection applications covering water disinfection, surface disinfection, food applications and

more.

Japan’s Stanley also targets high power UVC LEDs. Its exclusive AIN UV LED technology enables the company to

build a 265nm UVC LED which was claimed to have better inactivation effects in killing bacteria and viruses.

Stanley has achieved 50mW with its UVC LED products and will be able to achieve 200mW soon. The company

aims to collaborate with Tier-1 automotive OEM in Japan, Asia-Pacific and Europe and has launched 2L/min,

10L/min, and 100L/min UVC LED products for water disinfection.

LEDinside will launch the latest report, "TrendForce 2020 Deep UV LED Application Market and Branding

Strategies" providing cross analyses on applications and sales channels to discuss major trend of deep UV

applications and targed market in 2020 soon. The report will cover application fields including home appliances,

commercial space, automotive field, water purifier, and other potential markets to discuss branding strategies in

those channels.


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Samsung Includes Epistar for Micro LED Chip Supply LEDInside

Samsung has added Epistar, the Taiwan based LED chip provider, as a supplier of Micro LED chips to diversity its

supply chain, reported Korean media, TheElec.

The report said that Samsung included Epistar to its Micro LED

supply chain to secure its promise for launching Micro LED TVs in

the second half of 2020. Samsung revealed its Micro LED TV lineup

earlier this year at CES 2020. The company aims to debut four sizes

Micro LED TVs covering 75 inches, 88 inches 93 inches and 110

inches to the market in Europe, North America and the Middle East

this year.

To achieve the goal, Samsung has to ensure sufficient supply of Micro LED chips. The Korean company currently

work with Taiwan’s PlayNitride and China’s Sanan for chip. Epistar has announced the plan to expand production

capacity for miniaturized LED chips to meet the increasing demands from its clients. The news of Samsung adding

the chip maker into its supply chain also matches Epistar’s expansion in production capacity.

Epistar is reportedly supplying Mini LED chips for Apple’s new products including iPad Pro and MacBook Pro for

2020 and 2021 which are said to be adopting Mini LED technology.

BluGlass reports progress in Laser Diode business and micro-LED and LED programs, and cost saving for 2020 SemiconductorToday

BluGlass Ltd of Silverwater, Australia (which was spun off from the III-nitride department of Macquarie University

in 2005) has presented an operational update to shareholders, detailing recent developments in its direct-to-

market Laser Diode business unit (launched last October), recent progress on its micro-LED and LED programs,

and cost-saving measures for the remainder of the 2020 financial year.

BluGlass is developing and commercializing RPCVD as a low-temperature, ammonia-free alternative to traditional

manufacturing technologies. RPCVD is said to offer electronics manufacturers performance advantages including

higher-performing, lower-cost devices. The firm recently demonstrated patented ‘active as grown’ RPCVD tunnel

junctions for LED wafers, which provide a solution for the challenge of efficiency droop by combining multiple

LEDs in a single vertical LED stack (with the potential to generate greater light output for less power).

Technology update: Laser Diode development progress

BluGlass has engaged with prospective laser diode customers to develop bespoke designs for a range of end-

product applications from industrial cutting and welding to biomedical devices.

Current customer engagement programs include verified optical designs of standard laser diodes that the firm

has successfully modelled and simulated. The technology team has also delivered promising epitaxial results with

the implementation of several design improvements. BluGlass expects to deliver laser diode products to

customers for testing by the end of this calendar year.

The firm has also processed new remote-plasma chemical vapor deposition (RPCVD) tunnel-junction laser diode

test structures demonstrating good initial performance. These novel tunnel-junction laser diode structures

successfully replace the heavily lossy and resistive p-AlGaN cladding layers needed in standard laser diodes, says

BluGlass. By adding an RPCVD-grown tunnel junction, the p-type layers can be replaced by significantly less lossy

https://www.ledinside.com/news/2020/3/samsung_epistar_microled

http://www.semiconductor-today.com/news_items/2020/apr/bluglass-080420.shtml


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and resistive n-type device layers, paving the way for significant performance improvements with reduced optical

loss in laser diodes.

The initial device structures confirm the viability of these RPCVD-grown n-type layers for tunnel junction laser

diode applications. Further work is ongoing on development of the laser diode tunnel-junction layers’ initial

performance.

RPCVD tunnel junctions offer performance and cost advantages for the manufacture of high-brightness GaN laser

diodes, says BluGlass, including higher-performing devices with reduced optical loss as well as productivity and

cost improvements.

BluGlass has published a technical explainer document on the performance advantages of RPCVD for laser diodes

that can be download from www.bluglass.com.au/laser-diodes.

Laser diode test facilities

The BluGlass US-based Test Facility is on track for completion and full operation in June. It will provide the firm

with the flexibility to test laser diode chip, bar and packaged devices across a variety of product wavelengths. The

capabilities enable initial R&D testing during product development but will ultimately enable fully automated

testing of commercial volumes of the laser diode products.

The laser diode product development roadmap remains on-track to deliver repeat customer revenues anticipated

to commence in early 2021.

Supply-chain qualification

BluGlass says that it continues to develop and strengthen its global supply chain in the current operating

environment by working with and qualifying multiple partners on the fabrication of laser diode devices. Due to

the current issues surrounding COVID-19 quarantine, several of its US fabrication suppliers have been temporarily

closed or are operating on reduced capacity, however a primary supplier remains fully operational. To date, there

has been only minor disruption to BluGlass’ critical product design activities. In preparation for potential impacts,

discussions are underway with several backup suppliers.

Micro-LED update

BluGlass continues to advance its R&D on micro-LEDs, in particular its long-wavelength LEDs for red-green-blue

(RGB) applications. The firm has recently demonstrated progress towards developing RPCVD-grown red LEDs.

Micro-LED foundry customer orders for the quarter have been impacted by COVID 19, with several customers

currently on hold and unable to process and test devices. Despite the facility disruption, communication and

preparation for the next design iterations and orders continue.

Cascade LED update

BluGlass has continued to demonstrate iterative improvements in the light output of cascade LED test structures

using RPCVD tunnel junctions. The firm is waiting to process cascade LED chips to benchmark these latest

developments, currently being fabricated overseas.

A new video showing sequential green and blue light emission from an RPCVD-grown tunnel-junction cascade LED

is available to watch at www.bluglass.com.au/video.


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One of the key limitations for the commercial adoption of the firm’s RPCVD tunnel-junction technology for

traditional LED applications is the challenge of the added voltage from the tunnel-junction layers. BluGlass

remains confident that further reduction of tunnel-junction voltage for traditional LEDs is achievable with

additional development iterations.

However, this challenge is not as critical for cascade LED applications (two LEDs grown in a single stacked chip).

The additional small increase in voltage is potentially negated by the performance improvements offered by

cascade LEDs to address efficiency droop and drive smaller-form-factor, higher-efficiency LEDs.

BluGlass says it has made good progress in optimizing the key mechanisms required to drive individual LED

performance (the top and bottom LEDs) in cascade structures.

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OTHER

Odyssey names former MACOM executive Alex Behfar as executive chairman & acting CEO SemiconductorToday

Odyssey Semiconductor Inc, which is developing high-voltage power switching components and systems based

on proprietary gallium nitride (GaN) processing technology, has appointed Alex Behfar (a member of the board of

directors since June 2019) as executive chairman & acting CEO.

The appointment comes as Odyssey’s GaN foundry in Ithaca, NY, USA is in the final stage of being transformed

into a facility for GaN transistor fabrication and development. The foundry is nearly fully operational.

Former chairman & CEO Dr Richard Brown has been named chief technical officer, and will oversee efforts to

accelerate the development of a prototype of the firm’s technology to produce GaN-based high-voltage switching

power conversion devices and systems that may quickly supplant silicon carbide (SiC) as the dominant premium

power-switching device material, it is believed.

Behfar has over 30 years of experience in the semiconductor industry. He currently serves as a mentor for Cornell

University’s Praxis Center for Venture Development and is president of technical and business consulting firm

Ulexus Consulting. From January 2016 to January 2019, Behfar served as MACOM’s senior VP & chief scientist,

Photonics. From December 2014 to January 2016, he was MACOM’s senior VP & general manager, Photonic

Solutions. In 2000, Behfar founded BinOptics Corp, a supplier of indium phosphide (InP) lasers for data centers,

mobile backhaul, silicon photonics and access networks, and served as its chairman & CEO from inception through

to its $230m acquisition by MACOM in December 2014. Prior to BinOptics, he worked at IBM for more than 10

years in various capacities, including Laser Enterprise, where he designed the first commercially viable high-power

830nm and 980nm gallium arsenide (GaAs)-based lasers. Laser Enterprise was later sold by IBM to Uniphase and

is now part of II-VI Inc. He also served as IBM’s worldwide cross-functional Intellectual Assets Program Manager

for optoelectronics and telecommunications.

Behfar has been awarded over 50 US patents. He holds an M.S. and a Ph.D. in Electrical Engineering from Cornell

University and a B.Sc. in Electrical and Electronic Engineering from King's College, University of London.

http://www.semiconductor-today.com/news_items/2020/apr/bluglass-080420.shtml

http://www.semiconductor-today.com/news_items/2020/mar/odyssey-130320.shtml


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Brown has 18 years of experience in the design and fabrication of semiconductor devices, specializing in GaN and

related materials. Prior to Odyssey, he was a visiting scientist at Cornell University, where he worked on

developing GaN-based transistors for radio-frequency communications applications. He was also a founding

member and device scientist at Avogy Inc, a company funded by Khosla Ventures. Brown holds a B.S., M.S. and

Ph.D. in Electrical and Computer Engineering from Cornell University.

GaN-based systems outperform silicon and SiC-based systems due to the superior material properties of GaN. To

date, GaN devices have proven difficult to process using standard semiconductor processing methods. Odyssey

says that it has developed a novel processing modification that will allow GaN to be processed in a manner that,

for the first time, will make production of high-voltage GaN power switching devices viable.

The premium power switching device market - which is described as applications where silicon-based systems

perform insufficiently - is projected to reach over $3.5bn by 2025 and is currently dominated by silicon carbide.

This growth is driven largely by the rapid adoption of electric vehicles (EV) and hybrid electric vehicles (HEV) and

the growing number of installations of renewables such as solar and wind power as well as increased demand for

more efficient industrial motor drives.

Porous GaN firm Porotech completes £1.5m seed round SemiconductorToday

Gallium nitride (GaN) material technology developer Poro Technologies (Porotech, a recent spin-off from the UK’s

University of Cambridge) has closed a £1.5m seed round investment to develop a pilot plant in Cambridge and its

first major products. The seed round was co-led by the University of Cambridge’s commercialization arm

Cambridge Enterprise and IQ Capital Partners, joined by Martlet Capital and a syndicate of angel investors from

Cambridge Angels and Cambridge Capital Group.

Porotech says that its unique production process allows the controlled creation of a new class of porous GaN

semiconductor materials and structures that provide enhanced functionality. Porous GaN could be regarded as a

semiconductor composite of solid GaN and air. It enables Porotech to engineer a wide range of material properties

(optical, mechanical, thermal and electrical) and consequently offers an entirely new material platform for

semiconductor devices to be built upon.

Porotech’s porous GaN wafers, material technologies and device solutions can also deliver multi-functional wafers

with the material properties and functionalities targeted to the specific final device application for the cost-

effective manufacture of LEDs, lasers, power electronics, quantum light sources, sensors and solar cells.

With its process and product IP portfolio, scale-up and instrumentation solutions, and interdisciplinary expertise

in semiconductor materials and devices and materials chemistry, Porotech’s licensing business model (involving

proving by making) is to commercialize its unique material platform technology and device solutions in

conjunction with its partners and foundry network.

Porotech’s co-founders CEO Dr Tongtong Zhu, CSO professor Rachel Oliver and CTO Dr Yingjun Liu.

http://www.semiconductor-today.com/news_items/2020/apr/porotech-080420.shtml


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“Gallium nitride is a material poised to have impact across electronics and optoelectronics — from efficient power

transistors to quantum devices — and the introduction of porous architectures can extend its capability in all

these realms,” reckons professor Rachel Oliver, chief scientific officer & co-founder of Porotech and director of

the Cambridge Centre for Gallium Nitride at the University of Cambridge.

“Gallium nitride is the semiconductor material of the future. It is on the rise to revolutionise and transform the

electronics industry,” believes CEO & co-founder Dr Tongtong Zhu. “Porotech is at the forefront of this particular

revolution, where we have developed the first production technique that allows the integration of porous GaN in

tailored forms to significantly increase performance of real-world electronic and optoelectronic devices and

applications,” he adds.

Porotech was the winner of Cambridge Enterprise’s Postdoc Business Plan Competition 2018 and won the golden

award of the 5th China ‘Internet Plus’ Innovation and Entrepreneurship Competition in October 2019.


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PATENT APPLICATIONS

More than 160+ new patent families (inventions) were published in March 2020.

Other patent applicants Airbus Operations, Aisin Aw, Ampleon Netherlands, Analog Devices, Asahi Kasei, Asti Global, China Three Gorges University, Cree, CRRC Zhuzhou Institute, Daegu Gyeongbuk Institute of Science & Technology, Delta Electronics, Electric Power Research Institute of State Grid Shandong Electric Power, Facebook Technologies, Ferric, Furukawa, GaN Systems, Gwangju Institute of Science & Technology, Hefei Irico Epilight Technology, Infineon Technologies, Institute of Semiconductors, Jiangnan University, Jiaxing Super Lighting Electric Appliance, Kim Katherine Ann, Korea Institute of Ceramic Engineering & Technology KICET, Korea Photonics Technology Institute, Korea University Industrial & Academic Collaboration Foundation, Kunshan Govisionox Optoelectronics, Kunshan New Flat Panel Display Technology Center, Lg Electronics, Lin Guan Wei, Lu De Jia, Nanjing Changfeng Aerospace Electronic Equipment, Nanjing Zike Photoelectric Technology, National Taiwan University, Nitride Semiconductors, No 55 Institute of China Electronics Science & Technology, Qualcomm, Samsung Electronics, Semiconductor Components Industries, Shenzhen Third Generation Semiconductor Research Institute, Shenzhen Times Innovation Technology, Shenzhen University, Showa Denko, Siemens, Sino Crystal Semico, Siyang Grande Electronics, SLT Technologies, South China Normal University, South China University of Technology, Stanley Electric, State Grid Corporation of China (SGCC), Sumitomo Heavy Industries, Sun Yat Sen University, Suzhou Huashi Wireless Technology, Suzhou Institute of Nano Technology & Nano Bionics Chinese Academy of Sciences, SZ DJI Technology, Technische Universitaet Darmstadt, Texas Instruments, Tohoku University, Tokuyama, Torex Semiconductor, United Arab Emirates University, University Beijing, University of Electronic Science & Technology of China, University of Texas at Austin, University of Tokushima, University of Xiamen, Velodyne Lidar.


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Notable new patent applications

Method for manufacturing an electronic device Publication Number: WO2020/058256, FR3086097 Patent Applicant: CEA The present application relates to a method for manufacturing an electronic device, more particularly an electroluminescent device made of indium-gallium nitride (InGaN) or aluminium-gallium nitride (AIGaN), comprising the following successive steps: a) performing an ion implantation of indium or aluminium in an upper portion (105a) of a first monocrystalline layer (105) of gallium nitride (GaN), so as to amorphise the upper portion (105a) of the first layer (105) and preserve the crystal structure of a lower portion (105b) of the first layer (105); and b) performing a solid-phase recrystallisation annealing of the upper portion (105a) of the first layer (105), resulting in the upper portion (105a) of the first layer (105) being transformed into a crystalline layer of indium-gallium nitride (InGaN) or aluminium-gallium nitride (AIGaN).

Gallium nitride enhancement mode device Publication Number: WO2020/055984 Patent Applicant: ANALOG DEVICES

An enhancement mode compound semiconductor field-effect transistor (FET) includes a source, a drain, and a gate located therebetween. The transistor further includes a first gallium nitride-based hetero-interface located under the gate and a buried region, located under the first hetero-interface, the buried p-type region configured to determine an enhancement mode FET turn-on threshold voltage to permit current flow between the source and the drain.

Reducing bowing of materials before wafer-to-wafer bonding for led manufacturing Publication Number: US20200083400, WO2020/055889 Patent Applicant: FACEBOOK Disclosed herein are techniques relating to wafer-to-wafer bonding for manufacturing light-emitting diodes (LEDs). In some embodiments, a method includes reducing bowing of a layered structure including a semiconductor material and a substrate on which the semiconductor material is formed by generating breakages, fractures, or at least one region of weakened bonding within the layered structure. The method also includes bonding a base wafer to the semiconductor material, removing the substrate from the semiconductor material, and forming a plurality of trenches through the semiconductor material to produce a plurality of LEDs.

https://sobjprd.questel.fr/sobj/servlet/get_pds/WO202058256A1.pdf?userid=QPRK1002&type=0&pdfid=93501322&ekey=907


https://sobjprd.questel.fr/sobj/servlet/get_pds/US20200083400A1.pdf?userid=QPRK1002&type=0&pdfid=93323576&ekey=985


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Semiconductor structure and preparation method thereof Publication Number: WO2020/047814

Patent Applicant: ENKRIS SEMICONDUCTORS

A semiconductor structure, comprising: a substrate (1); a nucleation layer (3) located above the substrate (1); and a metal nitride thin film (2) located between the nucleation layer (3) and the substrate (1). The metal nitride thin film (2) is deposited between the substrate (1) and the nucleation layer (3), suppressing the diffusion of atoms in the material of the substrate (1), significantly reducing the thickness of the nucleation layer (3), and reducing the total thermal resistance of the semiconductor structure.

Method for manufacturing an optoelectronic device comprising a plurality of diodes Publication Number: US20200091224, FR3086100, EP3624192, CN110896084 Patent Applicant: CEA A method of manufacturing an optoelectronic device, including: a) transferring, onto a connection surface of a control circuit, an active diode stack including at least first and second semiconductor layers of opposite conductivity types, so that the second semiconductor layer in the stack faces the connection surface of the control circuit and is separated from the connection surface of the control circuit by at least one insulating layer; b) forming in the active stack trenches delimiting a plurality of diodes, the trenches extending through the insulating layer and emerging onto the connection surface of the control circuit; and c) forming in the trenches metallizations connecting the second semiconductor layer to the connection surface of the control circuit.

Doped buffer layer for group III-V devices on silicon Publication Number: US20200075314, DE102019117018, CN110875387, KR10-2020-0026733 Patent Applicant: TSMC Various embodiments of the present application are directed towards a group III-V device including a seed buffer layer that is doped and that is directly on a silicon substrate. In some embodiments, the group III-V device includes the silicon substrate, the seed buffer layer, a heterojunction structure, a pair of source/drain electrodes, and a gate electrode. The seed buffer layer overlies and directly contacts the silicon substrate. Further, the seed buffer layer includes a group III nitride (e.g., AlN) that is doped with p-type dopants. The heterojunction structure overlies the seed buffer layer. The source/drain electrodes overlie the heterojunction structure. The gate electrode overlies the heterojunction structure, laterally between the source/drain electrodes. The p-type dopants prevent the formation of a two-dimensional hole gas (2DHG) in the silicon substrate, along an interface at which the silicon substrate and the seed buffer layer directly contact.





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UV LED and display Publication Number: US20200098832 Patent Applicant: NITRIDE SEMICONDUCTORS

A UV-LED is disclosed. The UV-LED includes a sapphire substrate, a u-GaN buffer layer formed on the sapphire substrate, an n-GaN contact layer formed on the u-GaN buffer layer, an InGaN light emitting layer formed on the n-GaN contact layer, and a p-GaN layer formed on the InGaN light emitting layer. The UV-LED has a quadrate planar shape with at least one side having a chip size of 50 μm or less.

High-resolution display device Publication Number: KR10-2020-0027792, US20200075665 Patent Applicant: SAMSUNG ELECTRONICS A high-resolution display device is provided. The high-resolution display device includes a light-emitting layer including a first semiconductor layer, an active layer, and a second semiconductor layer, a plurality of transparent electrodes respectively formed on the second semiconductor layer in sub-pixel regions, a first electrode connected to the first semiconductor layer, a plurality of second electrodes connected to the plurality of transparent electrodes, a color-converting layer arranged over the light-emitting layer and configured to emit light of a predetermined color based on light generated by the light-emitting layer, which are sequentially stacked on a substrate including a plurality of sub-pixel regions. One or more ion injection regions corresponding to current injection regions corresponding to the plurality of the sub-pixel regions is formed in the second semiconductor layer.

Method for growth of a merged crystal by bonding at least a 1st and 2nd crystal to an adhesion layer to form a tiled substrate and growing a crystalline composition over said tiled substrate Publication Number: US20200087813 Patent Applicant: SORAA

Techniques for processing materials in supercritical fluids including processing in a capsule disposed within a high-pressure apparatus enclosure are disclosed. The disclosed techniques are useful for growing crystals of GaN, AlN, InN, and their alloys, including InGaN, AlGaN, and AlInGaN for the manufacture of bulk or patterned substrates, which in turn can be used to make optoelectronic devices, lasers, light emitting diodes, solar cells, photoelectrochemical water splitting and hydrogen generation devices, photodetectors, integrated circuits, and transistors.





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Semiconductor device Publication Number: US20200091330, CN110911490 Patent Applicant: TOSHIBA

According to one embodiment, a semiconductor device comprises a first nitride semiconductor layer on a substrate and a second nitride semiconductor layer on the first nitride semiconductor layer. The second nitride semiconductor layer has a larger bandgap than the first nitride semiconductor layer. Source and drain electrodes are on the second nitride semiconductor layer. A gate electrode is between the source electrode and the drain electrode. A third nitride semiconductor layer of p-type conductivity is on the second nitride semiconductor layer between the drain electrode and the gate electrode and spaced from the drain electrode.

A III-V semiconductor device and a method for forming a III-V semiconductor device comprising an edge termination structure Publication Number: EP3627559 Patent Applicant: IMEC According to an aspect of the present inventive concept there is provided a method for forming a III-V semiconductor device comprising:forming a III-V semiconductor layer stack comprising in a bottom-up direction: a drain contact layer, a drift layer, a channel layer, a body contact layer and a source contact layer, wherein the drain contact layer, the drift layer and the source contact layer have a first conductivity type and the channel layer and the body contact layer have a second conductivity type opposite the first conductivity type,forming a set of gate structures extending through the source contact layer, the body contact layer and the channel layer,forming a set of source contacts contacting the source contact layer, andforming an edge termination structure, wherein forming the edge termination structure comprises:forming a drain contact extending through the layer stack and contacting the drain contact layer, andforming an insulating region extending vertically through the layer stack, into the channel layer such that a thickness portion of the channel layer remains under a bottom of the insulating region, wherein the remaining thickness portion of the channel layer forms a reduced surface field, RESURF, layer.


https://sobjprd.questel.fr/sobj/servlet/get_pds/EP3627559A1.pdf?userid=QPRK1002&type=0&pdfid=93473893&ekey=1008


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