Modeling, design and performance of InP/InGaAs double-heterojunction bipolar transistors

The authors present measurements of InP/InGaAs double-heterojunction bipolar transistors (DHBTs) where the design has been guided by simulation results from energy-band and small-signal models. Both the energy-band model and small-signal model commence with the material parameters, process parameters, and device geometry. The energy-band model is used to investigate the insertion of layers to reduce the electron-blocking effect at the base-collector conduction-band discontinuity. The small-signal model is used to optimize the layer structure to provide a high unity-gain bandwidth, f/sub T/. The fabricated devices range in size from 60 mu m*60 mu m to 9 mu m*9 mu m (emitter size). The 9- mu m*9- mu m devices exhibit a small-signal current-gain in excess of 400 and a maximum f/sub T/ of 39 GHz. The measured high-frequency performance agrees closely with the simulation results of the small-signal model.<>