Analytical modelling of base transit time and early voltage of InP/InGaAs Heterojunction Bipolar Transistor for nonuniform base doping profile

InP/InGaAs Heterojunction Bipolar Transistors have increasingly become important due to their high speed performance. Base transit time is an important factor to determine the speed of these devices. An analytical model is developed here to predict the variation of base transit time (τ
_b
) and Early voltage (V
_A
) with composition of InGaAs base, as well as with base doping profile. Dependance of band gap on composition is also taken into account in the model.