Modeling the Changes in the Current-Voltage Characteristics of Vertical GaN-on-GaN p-i-n Diodes Under Electrical Stress

We analyze and model the changes in the electrical properties of vertical GaN-on-GaN p-i-n diodes submitted to electrical stress. The analyzed devices were treated with hydrogen plasma to minimize surface leakage. Constant-current stress tests were carried out to investigate the stability of the electrical characteristics of the samples. The results indicate the existence of two phases: 1) for short stress times, we detected a lowering in the turn-on voltage (VON), with no significant variation in series resistance, which was ascribed to an increase in injection efficiency at the anode contact and 2) for longer stress times, the turn-on voltage stabilized, but the series resistance showed a measurable decrease (-35%). Based on TCAD simulations, the observed behavior is ascribed to the diffusion of hydrogen from the p+ contact layer toward the junction. A model based on Fick's second law was developed, finding good agreement with the experimental data.