Modeling the Impact of Mg Out-Diffusion on Threshold Voltage of p-GaN/AlGaN/GaN HEMT

Abstract

This article presents a novel analytical model for the threshold voltage ( ${V}_{T}$ ) of p-GaN/AlGaN/GaN high-electron-mobility transistors (HEMTs), taking into account the influence of magnesium (Mg)-dopant out-diffusion from the top p-GaN layer into the AlGaN barrier and GaN layer. The proposed model incorporates realistic Mg out-diffusion profiles to accurately estimate ${V}_{T}$ of these normally off devices. Rigorous validation of the analytical model is conducted using experimental data and well-calibrated TCAD simulations, covering a wide range of device parameters and Mg out-diffusion profiles. Furthermore, the model enables the assessment of individual contributions of Mg dopants in the AlGaN and unintentionally doped (UID)-GaN layers. It also facilitates the estimation of the effects of growth duration and temperature of the p-GaN layer on the device’s threshold voltage.