Movement of Current Filaments and its Impact on Avalanche Robustness in Vertical GaN P-N diode Under UIS stress

Power semiconductor devices encounter stressful switching conditions in power electronic circuits [1]. Therefore, avalanche capability in power devices is highly desired, and its study is extremely important for realizing robust devices. Fortunately, GaN P-N junction possess avalanche capability, making vertical GaN devices with intrinsic P-N junctions robust against breakdown [2]. Most recently, vertical GaN P-N diodes with avalanche breakdown voltage up to 6 kV were reported [3]. However, most of these studies were done under DC, and a very few have investigated the avalanche behavior under circuit-level stresses such as unclamped inductive switching (UIS) stress. We previously reported unform and robust avalanche in our in-house fabricated 1.3 kV vertical GaN-on-GaN P-N diodes [4]. In our present work we extend our study to report the observation and role of current filament (microplasma tube) formed during avalanche conditions using the 1.3 kV GaN-on-GaN vertical P-N diode under UIS stress. We infer that the robustness in avalanche increased due to the movements of current filaments relieving the thermal stress.