Base charge accumulation and push-out effects on nonlinearity of Type-I InP/InGaAs/InP and Type-I/II AlInP/GaAsSb/InP double heterojunction bipolar transistors

The influence of energy band alignment on carrier transport and signal integrity is investigated on fabricated Type-I InP/InGaAs/InP and Type-I/II AlInP/GaAsSb/InP DHBTs. The Type-I double heterojunction bipolar transistor (DHBT) requires the use of a transition region (setback and superlattice layer) in base-collector hetero-interface to minimize the conduction band discontinuity that can cause current blocking in the collector I-V characteristics. Despite the effort, Type-I DHBT exhibits gain compression and base charge accumulation at high current injection, giving a nonlinear microwave operation. In contrast, the Type-I/II DHBT has a favorable band alignment and permits hot electron injection without impedance in both emitter-base and base-collector junctions, resulting in considerable microwave linearity improvement.