Partial Recovery of Dynamic RON Versus OFF-State Stress Voltage in p-GaN Gate AlGaN/GaN Power HEMTs

Dynamic Ron dispersion due to buffer traps is a well-known issue of GaN power high electron mobility transistors (HEMTs), critically impacting their performance and stability. Several works show that the dynamic Ron reaches a maximum for some off-state drain-source voltage ( VDS,off ) value typically in the range of several hundred volts and then partially recovers to smaller values. In this work, we propose a quantitative explanation for this behavior, attributing it to the charging/discharging dynamics of carbon (C)-related buffer traps. We characterize the dynamic Ron in packaged p-GaN gate AlGaN/GaN HEMTs with a custom measurement setup. We find that in these devices, the relative Ron increase reaches a maximum of 60% for VDS,off≈100 -200 V, partially recovering to about 30% as VDS,off is raised to 500 V. We ascribe this behavior to the partial neutralization of C-related acceptor traps in the buffer due to trapping of holes produced by a high-field generation mechanism. This explanation is supported by calibrated 2-D numerical simulations, that successfully reproduce the experimentally observed Ron reduction only when including a hole generation mechanism.