Current transport across the emitter-base potential spike in AlGaAs/GaAs heterojunction bipolar transistors

The recent observation of an emitter-base potential spike explains the origin of the high offset voltage of the Npn Al0.5Ga0.5As/GaAs heterojunction bipolar transistor. A new model is proposed in the paper to explain the higher turn on voltage of the emitter-base junction caused by the potential spike. This model treats the current transport mechanism across a p-n heterojunction to be a balanced two-step process, i.e., thermionic emission followed by Shockley diffusion, instead of the conventionally believed one-step diffusion process. The correct procedures to extract the potential spike height from the measured offset voltage are also established.