Reliability of enhancement-mode p-GaN gate GaN HEMT with multiple field plates

Abstract

In this paper, we fabricate enhancement-mode p-GaN gate GaN HEMTs with multiple field plates (MFPs) and analyze the reliability of the devices by means of simulation and experiment. Simulations of the electric-field distribution indicate that the MFPs effectively weaken the electric field peak near the gate to below the theoretical breakdown value and smooth the electric field between the gate edge and drain-side field plate edge. The simulated electric field peak leading to the breakdown of the device with MFPs at high drain voltage is located at the drain edge, which is validated by experimental results. The GaN HEMTs with MFPs exhibit excellent long-term reliability under high temperature and drain voltage, while deviations from threshold voltage and on-resistance were observed in the device subjected to drain stress. We attribute these deviations to electron accumulation and high field-assisted detrapping processes in the p-GaN layer. This investigation provides new insight into the mechanism of variations in threshold voltage and on-resistance under off-state drain stress.