Simulation of Structure Parameters' Influence on the Threshold Voltage of Normally‐Off p‐GaN/AlGaN/GaN Transistors

Abstract

The influence of different parameters of p-GaN/AlGaN/GaN structure on a threshold voltage of transistors is studied. The parameters that are varied are the thickness of the p-type GaN layer, its doping concentration, doping concentration of the GaN channel layer, and Schottky barrier height. Increasing the thickness of the p-GaN layer is found to increase the threshold voltage. Also, increasing doping concentration of the p-GaN layer increases the threshold voltage. The doping concentration of the GaN channel layer has the decisive effect on the possibility to use capacitance measurement for the threshold voltage assessment. Simulations show an interesting result of the Schottky barrier height threshold voltage dependence. For higher Schottky barrier height, lower threshold voltage is received, which is connected with the contribution of the negative differential capacitance of the p-GaN layer. This starts to increase for higher positive voltage if the Schottky barrier height is lower.