Failure mechanisms of GaN HEMTs in single event destructive short-circuit at different VDS voltage levels

In this work, the short-circuit (SC) robustness of 650 V normally-off SP-GaN HEMTs is investigated. The devices under test (DUTs) were subjected to single-event destructive SCs at different drain-source voltage levels. Overall, the DUTs exhibited a significant withstand time of several hundred microseconds. The experimental results first reveal the absence of a critical SC energy threshold, indicating that energy alone does not govern the failure mechanism. Instead, device failure is found to be more thermally driven, occurring once the junction temperature exceeds a specific limit. To support this conclusion, the junction temperature (Tj) evolution during the SC event was estimated using a highly simplified thermal model with a uniform heat dissipation based on the finite-element method (FEM), implemented in ANSYS APDL and calibrated with device geometries and material parameters extracted from its construction analysis. The simulation results show that all DUTs reached nearly the same Tj threshold at the instant of failure, regardless of the applied VDS. However, due to the simplifying assumptions underlying the FEM simulations presented in this study, the estimated temperatures should be regarded as indicative rather than exact.