Optimization of InP/GaInAs heterojunction bipolar transistors and phototransistors

The tradeoffs encountered in monolithic integration of p-i-n photodetectors and heterojunction bipolar transistors are described. For further improving the frequency performance of the individual transistors, the main challenges related to epitaxy are shortening of the base transit time by band gap engineering, and the proper grading of the base emitter and base collector junctions.