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

We fabricated enhancement-mode p-GaN gate GaN HEMT with multiple field plates (MFPs) and analyzed the reliability of devices by means of simulation and experiment in this paper. The simulation of electric-field distribution indicates that the MFPs effectively weaken the electric field peak near gate to below 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 device with MFPs at high drain voltage is located on drain edge, which is validated by experimental results. The GaN HEMTs with MFPs exhibit excellent long-term reliability under high temperature and high drain voltage, while deviations of threshold voltage and on-resistance were observed in the device subjected to drain stress. We attribute the deviations to electron accumulation and high field-assisted detrapping process in the p-GaN layer. This investigation will provide some new insight into understanding the mechanism of variations in threshold voltage and on-resistance under off-state drain stress.