Effect of emitter-base spacer design on the performance of InP/GaAsSb/InP DHBTs grown by MOCVD

Abstract

Effect of spacer layer design between InP emitter and GaAsSb base in InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) grown by MOCVD was investigated. A very thin tensile-strained GaAs layer, or a thin GaInP layer, or combination of both was inserted between InP emitter and GaAsSb base to mitigate Sb segregation and/or eliminate electron pile-up between emitter and base. With a base sheet resistances of ~ 1800 ohm/sq for all devices, DHBTs with a GaAs spacer, a GaInP spacer and the combination demonstrate a current gain of 24, 49 and 64, respectively. The conduct band discontinuity ΔEc at InP/GaAsSb interfaces and the current blocking effect are effectively eliminated by employing the combination of GaAs and GaInP layers.