Modeling and Simulation of Heterojunction Bipolar Transistors

Advances in growing nanostructure semiconductor thin films of different electronic properties and with a layer thickness approaching atomic dimensions have provided new opportunities in basic physics studies and device applications. Realization of the full potential of nanoscale heterostructures for electronic and optoelectronic device technologies requires reliable and precise predictive process and performance simulation models that are consistent with the fundamental principles of solid state physics and quantum mechanics. In this chapter, we present a general methodology, atomistic materials theory based modeling, for predicting device performance in technologically important heterostructure bipolar devices that can proceed relatively independently of experiment. The models incorporated within this general approach are extended sp 3 tight binding theory of band structures and extended drift-diffusion theory of charge carriers. Using this scheme, we have investigated the heteroemitter band alignment and charge carrier transport properties and performance of AlGaAs/GaAs heterostructure bipolar transistors (HBTs). Comparison with available experimental data shows a good agreement with the predictions of extended sp 3 tight binding theory for band offsets and extended drift-diffusion model for charge transport and device performance. Some of the issues pertinent to the modeling of Npn AlGaAs/GaAs HBTs are discussed.