Comparative Study of GaN and GaAs Based Heterojunction Bipolar Transistors

Abstract

In this study, the base-width modulation of GaN and GaAs based heterojunction bipolar transistor is analyzed using an enhanced drift-diffusion model. This work has been done to understand the concept of base width modulation clearly for designing GaN and GaAs based power transistors. The considered structure of this study is: n-type AlGaN/AlGaAs layer as an emitter, p-type GaN/GaAs as a base and n-type GaN/GaAs as a collector. In order to illustrate the difference between GaAs and GaN we have changed the material of the structure without changing the doping concentrations. The emitter and collector widths are remain fixed, while the base width is varied in order to find the optimized base for providing high collector current density. For these structures the emitter-base junction turn on voltage must be greater than 2.7 V. The effect of C-B voltage on the base width is significant. The neutral base-width Xb is a function of C-B voltage which is varied by varying the C-B voltage changes from 2 to 70 volt. The change in neutral base width leads to a significant change in the collector current density. Finally an optimized GaN and GaAs based structure is proposed and also which structure gives better performance between these two has been investigated later.