Overvoltage Ruggedness and Dynamic Breakdown Voltage of P-Gate GaN HEMTs in High-Frequency Switching up to Megahertz

Surge-energy and overvoltage ruggedness of power devices are desired in many power applications. For the GaN high-electron-mobility transistor (HEMT), a device without avalanche capability, its surge-energy and overvoltage ruggedness are both determined by its transient breakdown voltage (BV), which was recently found to be dynamic (i.e., time- and frequency-dependent). However, the switching frequency ($F_{\text{SW}}$) in previous overvoltage studies is only a few kilohertz. This work, for the first time, developed a testbed for high-voltage GaN HEMTs enabling continuous overvoltage switching with a Fsw up to 1 MHz. Two types of 600/650-V commercial p-gate GaN HEMTs were tested under 1 MHz overvoltage switching. Both of them showed good ruggedness. The gate injection transistor showed a nearly $F_{\text{SW}}$-independent dynamic BV, while the Schottky-type p-gate GaN HEMT showed a decreasing dynamic BV at higher $F_{\text{SW}}$, e.g., 270-V lower when Fsw increases from 2 kHz to 1 MHz. These behaviors were explained by the buffer trapping/de-trapping in two types of GaN HEMTs and were validated via TCAD simulation. This work unveils the true overvoltage margin of GaN HEMTs in high-frequency converters.