Large Area Vertical Gallium Oxide Schottky Diodes Neil Taylor 10/07/2020
Large Area Vertical
Gallium Oxide
Schottky DiodesNeil Taylor
10/07/2020
Radiation Detection• Alpha Spectroscopy
• Reprocessing Spent Nuclear Fuel• Environmental Sampling• Health Physics• Nuclear Forensics
• Gamma Spectroscopy• Neutron Activation Analysis
• Neutron Detectors• Reactor Power• Radiation Safety• Special Nuclear Material Detection Nuclear Regulatory Commission. “Stages of the Nuclear Fuel Cycle.” Web.13 April 2019.
https://www.nrc.gov/materials/fuel-cycle-fac/stages-fuel-cycle.html
Wide Bandgap Semiconductors
Silicon Silicon Carbide
Gallium Nitride
Gallium Oxide
Bandgap (eV) 1.14 3.23 3.4 4.9
Melting Point (°C)
1,400(200)
2,730 2,500 1,800
Breakdown Voltage
(MV/cm)
0.3 ~3 ~5 ~8
Polytypes 1 >250 2 5
Commercialization
Very High High Medium Low
Cost $ $$ $$ $
2nd Generation devices
15 mm
15 mm
Processing Flow for Vertical Ga2O3
Schottky Diode (3rd)1. Wafer dicing
• Dice the wafers into 15×15 mm2
2. Ohmic Back Contact
• RCA Cleaning
• Metal deposition by E-beam: Ti /Al /Ni/Au
• Rapid Thermal Annealing
3. Passivation
• Al2O3 deposition
• SiO2 deposition
4. Top Schottky contact
• Standard photolithography process: PR Coat/Pattern/Develop
• Metal deposition by E-beam: Ni/Au
Schematic of 3rd vertical Ga2O3 Schottky diode
Ni/Au Schottky contact
n-type Ga2O3 substrate
11 μm n--Ga2O3 (n~1.4×1016 cm-3)
Ti/Al/Ni/Au ohmic contact
Al2O3/SiO2 Al2O3/SiO2
FIV Measurement
FIV Analysis
• 105 total contacts tested
• Ideality range of 1.05-1.52 with an average of 1.12
• Barrier height range of 0.81-1.13 eV with an average of 0.98 eV
IS = AART2e
−qφBKBT
I = Is(e−
qV
nKBT)
RIV Measurement
CV Measurement
CV Analysis
• 105 contacts tested
• Doping concentration: average of 1.39e16
• Barrier height average of 1.13 eV
1
𝐶2=
2
𝑞𝑁𝐷𝜀𝑠𝜀𝑜𝐴2 (𝑉𝑏𝑖 − 𝑉)
FIV Temperature
Temperature Analysis
Spectroscopy Setup
• Determine alpha spectroscopy detector capabilities
• Vacuum chamber, CAEN preamplifier, CAEN high voltage power supply, CAEN digitizer, oscilloscope, and spectroscopy software
• Alpha sources and X-ray tube
FIV Analysis
• Calculation of depletion depth based on doping of epitaxial layer
• Similar results from CV Measurement (1.43 microns at -30V)
• SRIM calculations show 5.486 MeV alpha has a 14.3 µm range in Ga2O3
Conclusions
• Successfully fabricated GaO Schottky diodes with large area contacts
• Devices operated with breakdown voltages of ~400V for 2nd
generation and ~700V for third generation
• Devices show quite linear response to temperature up to 300C
• Future generation devices can be improved through edge termination, lower background and epitaxial doping, and lower defect density
• Continued testing of devices for radiation detection both X-rays and alpha particles
Questions?
This material is based upon work partially supported by the Department of Energy / National Nuclear Security Administration under Award Number(s) DE-NA0003921.
Neil Taylor is supported by the ETI Fellowship.
Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any
agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any
specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement,
recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state
or reflect those of the United States Government or any agency thereof.
• Collaborators• Yonngchao Yu, Mihee Ji, Tolga Aytug, Ivan Kravchenko, Pooran Joshi, M.
Parans Paranthaman
• Advisor: Dr Raymond Cao