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Advanced LIGO Photodiode Development

______

David Jackrel, PhD Candidate

Stanford University

Dept. of Materials Science and Engineering

James S. Harris

Hannover, Germany

August 20th, 2003

LIGO-G030495-00-Z

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Outline

Motivation & Introduction AdLIGO PD Specifications Device Materials and Design

InGaAs vs. GaInNAs

Device Results Thinned Device QE InGaAs & GaInNAs I-V 2m Thick GaInNAs Absorption

Predictions

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Advanced LIGO Schematic

Power Stabilization

Auxiliary Length Sensing

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Photodiode Specifications

LIGO I Advanced LIGO

Detector

Bank of 6PDs

Power Stabilizati

on

RF Detection GW Channel

Steady-State Power

0.6 W 1W/ 10 – 100mW 30mW

Operating

Frequency

~29 MHz 100 kHz 200MHz 100 kHz

Quantum

Efficiency

80% > 80% 95%

e.g. 1W/0.70=1.43W

Resonating Tank Circuit Thinned Substrate

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GaInNAs vs. InGaAs

GaInNAs

25% InGaAs

53% InGaAs

1064nm light 1.13eV

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InGaAs vs. GaInNAs PD Designs

2 m

GaInNAs lattice-matched to

GaAs!

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Rear-Illuminated PD Advantages

Conventional PD Adv. LIGO Rear-Illuminated PD

High Power Linear

Response High Speed

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Development Flow-Chart

AdLIGO Photodiodes

InGaAs GaInNAs

500um

Substrate

150um

Substrate1um I-Layer 2um I-Layer

100um

Substrate

100um

Substrate

90% QE

@

1 Watt

90% QE

@

1 Watt

~70% QE

@

Low-Power

60% QE

@

300mW

500um

Substrate

Stanford

& Vendor???

Hamamatsu

Product

30% QE

@

300mW

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Thinned Device QE (10mW)

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Thinned Device QE (w/ 100m, 3e17cm-3 Substrate)

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DC Device Efficiency (w/ ARC)E

xt.

Eff

icie

ncy

Optical Power (mW)

Bias (Volts)

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InGaAs vs. GaInNAs Dark Current

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InGaAs vs. GaInNAs Dark Current

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GaInNAs Device Transmission

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Predictions (I think we can do it…)

DetectorPower

Stabilization

RF Detection

GW Channel

Diameter 4.5mm 1.5mm 1mm

Bias -25V -25V -25V

Steady-State Power

1130mW 110mW 50mW

3-dB 1/RC Bandwidth

3MHz30MHz

( 180MHz)60MHz

Quantum Efficiency

~ 90% ~ 90% ~ 90%

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Laser Interferometer Gravitational Wave Observatory (LIGO)

Arm Length 4km

Beam Tube Diameter 4 ft.

Vacuum Pressure ~10-10 atm

Differential Strain ~10-18 m

180W

1064nm

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MBE Crystal Growth

Effusion cells for In, Ga, Al

Cracking cell for As Abrupt interfaces Chamber is under

UHV conditions to avoid incorporating contaminants

RHEED can be used to analyze crystal growth in situ due to UHV environment

T=450-600C

N Plasma Source

Atomic source of nitrogen needed Plasma Source!

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Heterojunction Band Gap Diagram

N-layer:

In.25Al.75As or GaAs

Eg2=2.0-1.4eV

P-layer:

In.25Al.75As or GaAs

Eg2=2.0-1.4eV

I-layer:

In.25Ga.75As, or Ga.88In.12N.01As.99

Eg1=1.1eV

n-

i-

p-

InAlAs and GaAs transparent at 1.064m

Absorption occurs in I-region (in E-field )

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Full Structure Simulated by ATLAS

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High Efficiency Detector Process (1)

1. Deposit and Pattern P-Contact

2. Etch Mesa – H2SO4:H2O2:H20 and Passivate in (NH4)2S+

3. Encapsulate Exposed Junction

4. Flip-Chip Bond

- N+ GaAs Substrate

- Epitaxial Layers

- Au Contacts

- Polyimide Insulator

- SiNx AR Coating

- AlN Ceramic

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High Efficiency Detector Process (2)

6. Deposit AR Coating & N-Contact

7. Saw, Package and Wire-Bond

- N+ GaAs Substrate

- Epitaxial Layers

- Au Contacts

- Polyimide Insulator

- SiNx AR Coating

- AlN Ceramic

5. Thin N+ GaAs Substrate

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Free-Carrier Absorption

(1-T-R) and (1-T-R)/(1-R)

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

850 950 1050 1150 1250 1350 1450 1550 1650 1750

Wavelength (nm)

Ab

sorp

tio

n (

no

rm.)

GaAs N+

GaAs S-I

GaAs N+ (W)

GaAs S-I (W)

32.9% N+

S-I

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Free-Carrier Absorption

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Free-Carrier Absorption

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Free-Carrier Absorption 5e17cm^-3

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Thinned Device QE (w/ ARC)

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Photodiode Specifications

LIGO I Advanced LIGO

Detector

Bank of 6PDs

Power Stabilizati

on

RF Detection GW Channel

Steady-State Power

0.6 W 1W/ 10 – 100mW 30mW

Operating

Frequency

~29 MHz 100 kHz 200MHz 100 kHz

Quantum

Efficiency

80% > 80% 90%-95%

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Thinned Device Photocurrent

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DC Device Response

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DC Device Efficiency

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Free-Carrier Absorption

A = 1 – exp(-tsub•fc) , fc = Nd * 3e-18

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Surface Passivation Results (2)

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(NH4)2S+ Surface States

(Green and Spicer, 1993)

GaAs(111)A GaAs(111)B

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Surface Passivation Results

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Large InGaAs Devices, –20V Bias

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InGaAs vs. GaInNAs Dark Current

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GaInNAs Dark Current

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InGaAs Dark Current

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GaInNAs H2SO4 vs. (NH4)2S+

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GaInNAs H2SO4 vs. (NH4)2S+

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Theoretical Saturation Powers

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Theoretical Saturation Powers

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RC-Circuit Bode Plot

3-dB

30MHz

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RC- and LCR- Transmittance

RC-Circuit

LCR-Circuit

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LCR- Circuit Impedance

s

iV

RCZ

Zin

out

20

1||

||||

0

s

iV

RCZ

Zin

out

20

1||

||||

0

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RC- vs. LCR-Circuits

RC- PD acting as a Low-Pass Filter LCR #1- PD // Inductor as a Tuned Band-Pass Filter (with large R=50)

LCR #2,3- PD // Inductor as a Tuned Band-Pass Filter (Rs=1)

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Transfer Function LCR #3