Type-II InP/GaAsSb double-heterojunction bipolar transistors with<i>f</i>_MAX&gt; 700 GHz

Abstract

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 fMAX 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 fT = 429 GHz and fMAX = 715 GHz. To the best of the authors' knowledge, this is the highest reported fMAX for InP/GaAsSb-based DHBTs to date.