Permanent degradation of p-GaN HEMTs due to repetitive overvoltage stress during hard turn-off switching

This study investigates the long-term impact of dynamic overvoltage stress on GaN HEMTs using a newly designed test circuit, UIS3, a variant of classic UIS, which isolates key stress factors. Devices were subjected to short-duration repetitive overvoltage stress near and below their dynamic breakdown voltage. Characterization before and after stress reveals permanent degradation in , and , suggesting deep-trapping or structural damage within the device. A distinct alteration in the curve is observed, may indicate less spreading of the electric-field within the device. degradation is also noted, likely due to trapping effects, with partial recovery at room temperature. Higher stress levels accelerate failure. Waveform analysis and post-failure characterization indicate a short-circuit failure mode, likely due to partial dielectric breakdown during overvoltage events. These results provide new insights into GaN HEMT degradation mechanisms under high-voltage stress.