The dc and rf characteristics for InP/InGaAs heterojunction bipolar transistors having a single heterojunction design were measured and compared with those for double heterojunction devices that employ a composite collector. Although the composite-collector design improves the breakdown characteristics of our devices the rf performance was not as good. This we partially attribute to the collector heterojunction, which causes "current blocking".
Performance prediction of InP/GaAsSb double heterojunction bipolar transistors for THz applications