Analytical Model for the Threshold Voltage of ${p}$ -(Al)GaN High-Electron-Mobility Transistors

Abstract

An analytical model for the calculation of the threshold voltage for enhancement-mode (E-mode) p-(Al)GaN high-electron-mobility transistors (HEMTs) is presented. The ON-state behavior (at low output voltages) of both p-GaN HEMTs and p-AlGaN HEMTs-including the gate injection transistor-are discussed in detail, and closed expressions for the threshold voltage V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> of both devices are deduced. It is found that the threshold voltage values for both devices are close to one another, and that there is an ideal upper limit when the p-type doping in the AlGaN gate is perfectly tailored, yielding more positive threshold voltages. This ideal case might be difficult to realize technologically, but can serve as a benchmark for the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> of p-(Al)GaN HEMTs.