Second Breakdown and Robustness of Vertical and Lateral GaN Power Field‐Effect Transistors

Robustness of GaN power field-effect transistors, including the vertical UMOSFET, vertical DMOSFET, and lateral p-AlGaN gate HEMT is studied by analyzing their safe operating areas (SOA) using finite-element-analysis device simulation. At off-state gate voltages, the devices are forced into high-voltage, high-current avalanche breakdown. Assuming isothermal conditions at 300 K, the simulated DMOSFET SOA exhibits high robustness, while the UMOSFET and the p-AlGaN gate HEMT experiences current snapback. The simulated robustness of both the DMOSFET and the UMOSFET degrades when realistic temperature dependence is included in the non-isothermal case, with current filamentation in high dissipation areas, leading to a more pronounced current snapback.