High efficient 850 nm and 1,310 nm multiple quantum well SiGe/Si heterojunction phototransistors with 1.25 plus GHz bandwidth (850 nm)

The Si/sub 0.5/Ge/sub 0.5//Si multiple quantum wells (MQW) are placed between the base and collector of Si/SiGe heterojunction bipolar transistors as light absorbing layers. The phototransistor with high responsivity and bandwidth at 850 nm is demonstrated. Efficient near infrared (1,310 nm) photoresponse also achieved in this device. The results indicate the Si/SiGe phototransistor is suitable for front-end photoreceivers in the high-speed optical communication applications.