Type-II InP/GaAsSb double-heterojunction bipolar transistors withfMAX> 700 GHz

The "type-II" staggered band lineup at the base-collector junction of InP/GaAsSb double-heterojunction bipolar transistors (DHBTs) eliminates the current blocking effect observed in InP/GaInAs DHBTs and allows the use of a pure binary InP collector that provides a high breakdown voltage and good thermal conductivity. Improvement of the power gain cutoff frequency f MAX requires a reduction in base resistance and/or base-collector capacitance. We have decreased the base contact resistivity by in situ Ar sputtering immediately prior to the base contact deposition. The resulting DHBTs simultaneously feature f T = 429 GHz and f MAX = 715 GHz. To the best of the authors' knowledge, this is the highest reported f MAX for InP/GaAsSb-based DHBTs to date.