Type-II InP/GaAsSb double-heterojunction bipolar transistors with fMAX > 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/GalnAs 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. (C) 2014 The Japan Society of Applied Physics