Self-Enhanced Unclamped-Inductive-Switching Robustness of High-Voltage p-GaN Gate HEMT on Sapphire Substrate

A novel self-enhanced unclamped-inductive-switching (UIS) behavior of high-voltage p-gallium nitride (GaN) gate high-electron-mobility transistor (HEMT) on sapphire substrate (GaN-on-sapphire HEMT) is first discovered and investigated. In addition to the traditional LC-like resonance behavior of GaN-on-Si HEMT, the UIS behavior of GaN-on-sapphire HEMT deviates significantly and exhibits temperature-dependent failure voltage, indicating that impact ionization may be induced by the high electric field (E-field) and dominates the failure phenomenon. Furthermore, Technology Computer-Aided Design (TCAD) simulations and output capacitance characterization are carried out, which collectively confirm this mechanism. As the inductive energy is dissipated by impact ionization current, the overvoltage of GaN-on-sapphire HEMT is 32.1% lower than the theoretical resonant voltage. Finally, the UIS robustness of GaN-on-sapphire HEMT is self-enhanced.