STANFORD High-Power High-Speed Photodiode for LIGO II David Jackrel Ph.D. Candidate- Dept. of Materials Science & Eng. Advisor- Dr. James S. Harris March.

STANFORD

High-Power High-Speed Photodiode for LIGO II

David Jackrel

Ph.D. Candidate- Dept. of Materials Science & Eng.

Advisor- Dr. James S. Harris

March 15th, 2001

LIGO-G010122-00-Z

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Outline

Introduction Photodiode Specifications &

Development Device Structure & Materials

Diode Electrical Characterization Contact Resistance I-V Characteristics C-V Characteristics

Future Plans

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Photodiode Specifications

Parameter LIGO I LIGO II (old) LIGO II (new)

Steady-State Power

0.6 W ~10 W ~1 W

Operating Frequency

29 MHz ~100 MHz ~100 kHz

Quantum Efficiency

80% 90% 90%

Transient Damage

3 Joules / 10 ms

100 Joules /10 ms (?)

100 Joules /10 ms (?)

Signal/Noise 1.4e10 Hz 3.1e10 Hz 3.1e10 Hz

Spatial Uniformity

1% RMS 0.1% RMS 0.1% RMS

Surface Backscatter

1e-4 / sr 1e-6 / sr 1e-6 / sr

Detector Design

Bank of 6(+) PDs

1 PD(~3 mm dia.)

1 PD(1-3 mm dia.)

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Photodiode Development

June 1999- Came on the project Passed Quals Began Training on MBE Machine and Processing

Procedure

March 2000: 1st Round Wafers Materials Analysis Electronic Properties Not Good

June 2000: 2nd Round Wafers Materials Analysis (Transmission, XRD, TEM, SEM) Electronic Properties Characterized (TLM, I-V, C-V)

March 2001- Future: 3rd Round Wafers Electronic Properties Optoelectronic Properties (Bandwidth, QE, Power

Response)

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P-I-N Device Characteristics

Large E-field in I- region

Depletion Width Width of I- region

Frequency response

max (sat/WI)

RC time constant

Tuned to a specific

1

IW

IsJ

Js

WAKC

CR

/0

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Band Gap Diagram w/ Heterojunctions

InAlAs Optically transparent to 1.06m radiation

Absorption occurs in i-region

N-layer:

In.22Al.78As

Eg2=2.0eV

P-layer:

In.22Al.78As

Eg2=2.0eV

I-layer:

In.22Ga.78As

Eg1=1.1eV

n-

i-

p-

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InGaAs/GaAs PD Structure

•P-I-N structure

•InGaAs for i-layer

•InAlAs for the n- and p- layers

•MBE

•Grading layer

•AR coating & Au/Pt contacts

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Rear-Illuminated PD Advantages

High Power Linear

Response High Speed

Proposed PD (Rear-Illuminated)Conventional PD

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MBE Surface Kinetics

Adsorption Physisorption Chemisorption

Surface migration

Incorporation Thermal

desorption

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III-V Lattice Constants and Band Gaps

InAlAs and InGaAs well lattice matched

InAlAs much wider band gap

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Lattice Mismatched Growth

Lattice Constant for InxGa(1-x)As:

a=5.6536+0.4054x

In.4Ga.6As: hc 100Å

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TEM Images of Confined Dislocations

Device Layers:

-few dislocations

Graded Buffer:

-many dislocations

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Graded Buffer Dislocations

Biaxial stress in film causes dislocations to glide

Misfit growth often results in surface striations

Hsu, et al. (1992)

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P- and N- Contacts

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TLM (Transmission Line Model)

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TLM Measurements: P-Contact

Short d, R, Slope Long d, R, Slope

#673, n-12, lengths 1-7

-0.1

-0.05

0

0.05

0.1

-6 -4 -2 0 2 4 6

V (volts)

I (A

mp

s)

1/Slope vs. Length Indexy = 6.7862x + 8.2118

R2 = 0.9892

0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Length Index

Res

ista

nce

(O

hm

s)

Rc = 8.2/2 = 4.1

Rs = 6.8 / 10m = 0.68/m

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P-Contact Resistance (#673)

p-673, Before & After Anneal

6

8

10

12

0 5 10 15 20

Structure #

Rc

(Oh

ms)

Squares: Before Anneal

Circles: After Anneal

2

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P-Contact Resistance (#649)

p-649, Before & After Anneal

4

6

8

10

12

0 5 10 15 20

Structure #

Rc

(Oh

ms) Squares:

Before Anneal

Circles: After Anneal2

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N-Contact Character

#649, n-3, length-1

y = 0.0002x5 - 5E-05x4 + 0.0004x3 - 7E-05x2 - 0.0007x + 7E-05

R2 = 0.9998

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

-4 -2 0 2 4

V (Volts)

I (A

mp

s)

n-#649, n-3, length-7y = 0.2513x + 0.0001

R2 = 0.9998

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

V (Volts)

I (A

mp

s)

Before Annealing:

Not Ohmic (Schottky)

After Annealing:

Ohmic

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N-Contact Resistance (After Anneal)

1/Slope vs/ Length Indexn-#649, n-3

y = -0.0312x + 4.3661

R2 = 0.0948

3.9

4

4.1

4.2

4.3

4.4

4.5

4.6

0 1 2 3 4 5 6 7 8

Length Index

Res

ista

nce

(O

hm

s)

Not very linear!

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N- and P- Contact Resistance

Resistance:

Test Pad

(1200 m2)

Resistance:

Actual Contacts

Resistivity

N - Contact

2.1 0.36 m 0.00175 /m2

P – Contact

4.5 2.8 m 0.00375 /m2

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I-V Characteristics

#673, n6Rear-up, Probe Station

-0.02

0

0.02

0.04

0.06

0.08

0.1

0.12

-4 -3 -2 -1 0 1 2 3

V (volts)

I (a

mp

s)

(-0.278mA @ -3V)

(#673 Rectified, #649 Did not…)

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I-V Characteristics: Reverse Bias

#673, n6, curve-aRear-up, Probe Station

-0.0025

-0.002

-0.0015

-0.001

-0.0005

0

-12 -10 -8 -6 -4 -2 0

V (volts)

I (a

mp

s)

(-2.1mA @ -10V)

Wrong shape (defects?)

Large Current Values

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I-V Characteristics: Semi-Log Plot

#673n6: ln (I) vs. V

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

2

0.03 0.53 1.03 1.53

V

ln (I

)

Ideal R-G

Ideal:

Slope = 11.4

q/kT = 38.6

n1 = 3.39

I01 = 0.83A

R-G:

Slope = 10.13

q/2kT = 19.3

n2 = 3.82

I02 = 2.26A

I0 = 3.09 A

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Possible Explanation: Carrier Hopping

Defects in the I-layer Alternative Transport Mechanism

Ev

Ec

+ -

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I-V Characteristics: Light vs. Dark

#673, n6, curves-d,eSoldered, Dark and Illuminted

-0.0014

-0.0012

-0.001

-0.0008

-0.0006

-0.0004

-0.0002

0

-6 -4 -2 0

V (Volts)

I (A

mp

s)

A, Dark

A, Illum.

I-layer not fully depleted at zero bias…

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C-V Characteristics (#673)

#673, n-?, trial-s

1.50E-09

1.70E-09

1.90E-09

2.10E-09

2.30E-09

2.50E-09

2.70E-09

2.90E-09

3.10E-09

3.30E-09

0 1 2 3 4 5 6 7Reverse Bias (-Volts)

C (

F)

2.09nF

3.05nF

Theoretical C 0.40nF

depletion width 0.39m

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Capacitance, WD, and ND

WD 0.5m

ND 1016cm-3

(@ 10V bias)

WD 2.0m

ND 1015cm-3

(@ 5V bias)

(Sze, S. M., Physics of Semiconductor Devices, 1969)

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Future Plans: InGaAs/InAlAs

Less defects Test QE

Buffer Layers

Defects Materials

Analysis

Front Illum.

Thin Substrate

Bandwidth TLM Test QE

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Future Plans: Nd:YAG & Nitrides

Nd:YAG LASER Testing Set-up at Stanford (w/ help from Mike

Z.) Compliment Faster Device Turn-Around

Nitride System: InGaNAs Quaternary No Graded Buffer But, Still Rear-Illuminated