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Advanced LIGO High-Power Photodiodes

Advanced LIGO High-Power Photodiodes. David Jackrel, PhD Candidate Dept. of Materials Science and Engineering Advisor: James S. Harris LSC Conference, LLO March 17 th -21 st , 2003. LIGO-G030069-00-Z. Outline. Introduction High-Power Results High Efficiency Process Predictions.

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Advanced LIGO High-Power Photodiodes

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  1. Advanced LIGO High-Power Photodiodes David Jackrel, PhD Candidate Dept. of Materials Science and Engineering Advisor: James S. Harris LSC Conference, LLO March 17th-21st, 2003 LIGO-G030069-00-Z

  2. Outline • Introduction • High-Power Results • High Efficiency Process • Predictions

  3. Photodiode Specifications

  4. GaInNAs vs. InGaAs GaInNAs 25% InGaAs 53% InGaAs 1064nm light  1.13eV

  5. InGaAs vs. GaInNAs PD Designs 2 m GaInNAs lattice-matched to GaAs!

  6. Heterojunction Band Gap Diagram InAlAs and GaAs transparent at 1.064m  Absorption occurs in I-region (in  E-field ) p- i- n- N-layer: In.22Al.78As or GaAs Eg2=2.0-1.4eV I-layer: In.22Ga.78As, or Ga.88In.12N.01As.99 Eg1=1.1eV P-layer: In.22Al.78As or GaAs Eg2=2.0-1.4eV

  7. Rear-Illuminated PD Advantages • High Power • Linear Response • High Speed Conventional PD Adv. LIGO Rear-Illuminated PD

  8. DC Device Response

  9. DC Device Efficiency Ext. Efficiency Bias (Volts) Optical Power (mW)

  10. - N+ GaAs Substrate - Epitaxial Layers - Au Contacts - Polyimide Insulator - SiNx AR Coating - AlN Ceramic High Efficiency Detector Process (1) 2. Etch Mesa – H2SO4:H2O2:H20 and Passivate in (NH4)2S+ 1. Deposit and Pattern P-Contact 4. Flip-Chip Bond 3. Encapsulate Exposed Junction

  11. - N+ GaAs Substrate - Epitaxial Layers - Au Contacts - Polyimide Insulator - SiNx AR Coating - AlN Ceramic High Efficiency Detector Process (2) 5. Thin N+ GaAs Substrate 7. Saw, Package and Wire-Bond 6. Deposit AR Coating & N-Contact

  12. Surface Passivation Results

  13. Predictions

  14. Conclusion • High-Power Results • 300mW (@ 3MHz B.W.) • 60% External Efficiency • High-Efficiency Process • < -30 Volts realized (on un-mounted devices) • Working out processing • Predictions (by Next LSC…) • 1 Watt (@ 1MHz B.W.) • 90% External Efficiency

  15. MBE Crystal Growth N Plasma Source • 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=450-600C Atomic source of nitrogen needed  Plasma Source!

  16. P-I-N Device Characteristics • Large E-field in I- region • Depletion Width  Width of I- region • RC time constant • Absorbs a specific 

  17. Full Structure Simulated by ATLAS

  18. DC Device Efficiency

  19. Free-Carrier Absorption N+ S-I

  20. Surface Passivation Results (2)

  21. (NH4)2S+ Surface States GaAs(111)A GaAs(111)B (Green and Spicer, 1993)

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