Exploring Short-Circuit Failure Mechanism of Cascode GaN HEMT

This letter reveals the in-depth failure mechanisms of Cascode GaN devices under a single pulse short circuit event through simulation-based analysis and experimental validations. Under precisely controlled short circuit conditions, a unique “recovery” failure phenomenon is observed, which results in two main burned regions: (i) the drain corner surrounded by gate fingers, and (ii) the drain pad connection metal. Thermal simulations identify the drain corner as the primary failure origin. The failure process is then revealed by an equivalent circuit model. The high electric fields induce thermal breakdown of the dielectric, creating a conductive path that increases total drain current. The burned area subsequently becomes highly resistive again, reducing drain current while maintaining significant leakage. Under high bus voltage, Joule heating ultimately triggers catastrophic device destruction. Furthermore, a Schmitt trigger-based detection method experimentally confirms the first burned area as the initiation site of the short-circuit failure.