Current transport across the emitterhyphen;base potential spike in AlGaAs/GaAs heterojunction bipolar transistors

摘要

The recent observation of an emitterhyphen;base potential spike explains the origin of the high offset voltage of theNpnAl0.5Ga0.5As/GaAs heterojunction bipolar transistor. A new model is proposed in the paper to explain the higher turn on voltage of the emitterhyphen;base junction caused by the potential spike. This model treats the current transport mechanism across aphyphen;nheterojunction to be a balanced twohyphen;step process, i.e., thermionic emission followed by Shockley diffusion, instead of the conventionally believed onehyphen;step diffusion process. The correct procedures to extract the potential spike height from the measured offset voltage are also established.