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Two tone inter-modulation distortion measurements were performed at 18 GHz to characterize the nonlinearity of Type-I InP/InGaAs/InP and Type-I/II AlInP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs). Two-dimensional hydrodynamic (HD) simulations were also performed, showing that the base push-out and charge accumulation effects are the dominant physical origins of nonlinearity for the Type-I DHBT at high current densities. Comparatively, the Type-I/II DHBT exhibits no such effects. Hence, we conclude that DHBTs having a Type-I/II energy band alignment will have an inherent linearity advantage compared to DHBTs with the Type-I energy band alignment.

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.