Frequency response of HBTs as photodetectors

Abstract
The frequency response of HBT photodetectors fabricated by the MMIC HBT process has been experimentally investigated. 3-dB bandwidths of 2 GHz and more than 20 GHz have been achieved in a CE (common emitter) HBT and a CB (common base) HBT, respectively. The photoresponse of the CEHBT is approximately 25 dB higher than that of the CBHBT at 1 GHz. The CEHBT has a higher signal-to-noise ratio than a PIN/50- Omega FET amplifier at 10 GHz.