GaN Vertical p-i-n Diodes in Avalanche Regime: Time-Dependent Behavior and Degradation

This paper shows that vertical GaN-on-GaN p-i-n diodes are able to withstand long-term operation in moderate avalanche conduction regime, thus proving the excellent stability of the gallium nitride material system. Under constant stress in stronger avalanche regime, the devices show a significant increase in the series resistance, a slight increase in forward voltage and a measurable increase in avalanche voltage. Degradation is ascribed to the generation of defects, a process which is likely occurring in the intrinsic region. The time-dependence of the performance loss is explained by considering the simultaneous presence of field-assisted trapping in the avalanche region and of charge de-trapping in the medium-field region of the devices. An interpretative model based on these assumptions is proposed to explain the full set of the experimental data.