Outline Motivation Structures of Si/SiGe Heterojunction Phototransistor

Outline

• Motivation

• Structures of Si/SiGe Heterojunction Phototransistor

• Electrical measurement results

• Optical dc measurement results

• Side-Wall Terminal Technique & Optical Transient Measurement Results at 850nm

• Conclusion

Outline

• Motivation

• Structures of Si/SiGe Heterojunction Phototransistor

• Electrical measurement results

• Optical dc measurement results

• Side-Wall Terminal Technique & Optical Transient Measurement Results at 850nm

• Conclusion

Photo-transistor for Fiber Communication Application

• Extremely High Responsivity

• Over ~10A/W
• Much lower operation voltage than Avalanche Photodiode (APD)
• Much lower cost than APD and semiconductor optical amplifier (SOA)

• Circuit Level Integration

• HBT+HPT (Hetero-junction Photo-transistor) OEIC1 !!
• Lower fabrication cost than p-i-n+HBT OEIC

• Analog fiber communication application of HPT2

• Clock recover O-E circuit, O-E Mixer

• Speed is critical issue for the application of HPT!!

• Optical fT for analog fiber application1
• Electrical f3dB for digital fiber application
• We will demonstrate a novel method to improve the gain-bandwidth product of HPT in this presentation !!

Why Si/SiGe Based HPT ?

• Low Responsivity of Si based p-i-n Photodetectors (PDs)1

• High operation gain of photo-transistor can overcome this drawback

• Much Lower Operation Voltage than APD

• Without voltage or temperature control circuit
• Low cost !!

• High gain/speed2, yield and reliability of SiGe HBT

• In plane structure of Si/SiGe based HBT has higher yield and reliability than etch-mesa structure of III-V based HBT3

• Si/SiGe based TIA+HPT

• Almost without modification of standard TIA fabrication process
• Low cost!!

• Analog nonlinear application of SiGe based HPT

• Clock recover O-E circuit, O-E Mixer

Outline

• Motivation

• Structures of Si/SiGe Heterojunction Phototransistor

• Electrical measurement results

• Optical dc measurement results

• Side-Wall Terminal Technique & Optical Transient Measurement Results at 850nm

• Conclusion

Cross-Sectional and Top Views of Fabricated Si/SiGe HPT

Outline

• Motivation

• Structures of Si/SiGe Heterojunction Phototransistor

• Electrical measurement results

• Optical dc measurement results

• Side-Wall Terminal Technique & Optical Transient Measurement Results at 850nm

• Conclusion

Gummel Plot of Si/SiGe HPT with/without MQW

fT fmax of Si/SiGe HPT with/without MQW

Outline

• Motivation

• Structures of Si/SiGe Heterojunction Phototransistor

• Electrical measurement results

• Optical dc measurement results

• Side-Wall Terminal Technique & Optical Transient Measurement Results at 850nm

• Conclusion

Outline

• Motivation

• Structures of Si/SiGe Heterojunction Phototransistor

• Electrical measurement results

• Optical dc measurement results

• Side-Wall Terminal Technique & Optical Transient Measurement Results at 850nm

• Conclusion

Speed limits the application of HPT in the field of digital fiber communication

• Speed limits the application of HPT in the field of digital fiber communication

• Poorer speed performance than p-i-n or APD
• What are the prior arts to improve speed performance of HPT ?

• Base termination technique1,2,3

• Turn on the B-E junction to remove the excess hole at base
• Significant speed enhancement 1,2
• Huge dc power consumption (dark current)!!
• At the expense of optical gain1,2!!
• What is the optimum solution?

General solutions for speed enhancement in III-V and Si based HPTs

• General solutions for speed enhancement in III-V and Si based HPTs

• Especially suitable to SiGe based HPTs with planar structure

• Significant speed improvement with less gain sacrifice and increase in dark current

• Open a new field for HPTs OEIC (Opto-Electronic Integrated Circuit)

Bandwidth-Responsivity Products of Different Types of HPT

Outline

• Motivation

• Structures of Si/SiGe Heterojunction Phototransistor

• Electrical measurement results

• Optical dc measurement results

• Side-Wall Terminal Technique & Optical Transient Measurement Results at 850nm

• Conclusion

Conclusion

• Two types of SiGe based HPT are demonstrated

• MQW structure at B-C junction can improve responsivity significantly

• Side-wall terminal technique can improve the speed performance of two HPT structures significantly with less gain reduction and eliminate huge dc power consumption

• Ordinary HPT structure has the application of 850nm short reach 2.5G/bits data communication

• MQW HPT structure has the application of 850nm optoelectronic mixer