THIN-BASE INGAAS HETEROJUNCTION BIPOLAR-TRANSISTOR WITH PARABOLICALLYGRADED INGAALAS EMITTER

We describe an InGaAs heterojunction bipolar transistor lattice-matche d to InP with a parabolically graded quaternary In(Ga1-xAlx)As emitter and a thin base. We obtain a room-temperature common-emitter DC curre nt gain of more than 100, indicating the successful operation of the p arabolic grading. High-frequency properties are equally promising, wit h current gain cutoff frequencies up to 125 GHz. These studies provide evidence for a significant reduction of base and collector transit ti mes at high current densities, due to the velocity overshoot effect.