TCAD Simulations of Degradation Mechanism in p-GaN Gate HEMTs under Gate Stress

In this paper we perform physical simulations of p-GaN gate HEMTs to study the time-dependent-gate-breakdown (TDGB) phenomenon when subject to constant-voltage stress (CVS). Leveraging on the advanced capabilities of Ginestra TCAD software, we show for the first time a simulation methodology able to model and explain the onset of gate breakdown experimentally measured in p-GaN gate HEMTs during a CVS. In our simulations we activate the thermochemical (TC) model for the defect generation which, due to a strongly field-dependent rate, creates traps in the p-GaN close to the gate contact, resulting in the gate current increase. We also perform a statistical analysis of this phenomenon and we show how, by adding randomization effects in the simulation, we can also reproduce the temporal dispersion of breakdown events.