A collector current model for InAlAs/InGaAsSb/InGaAs double heterojunction bipolar transistors with non-ideal effects

摘要

A collector current model incorporating electron diffusion in the base and thermionic emission at the abrupt B-E heterojunction is derived and applied to inCaAsSb heterojunction bipolar transistors (HBTs). Parameters extracted from the model include effective base doping concentration, conduction band discontinuity (△E_c) at the base-emitter junction, and emitter resistance. The calculated current from the model is consistent with the measured result. It is found that a high collector current ideality factor is resulted from a nonzero △E_c and a low effective base doping concentration. Moreover, a nonzero △E_c makes the high-injection effect almost invisible in collector current characteristics, even if it actually exists.