GaN high electron mobility transistors (HEMTs) have limited avalanche capability and usually fail catastrophically in voltage overshoot up to their dynamic breakdown voltage (BVdyn). This work presents the first comparative study of the parametric shift and recovery of three mainstream GaN HEMTs in repetitive overvoltage switching near their BVdyn. In each switching cycle, a voltage overshoot up to 90% of BVdyn was applied during the turn-OFF process. As the switching prolongs, all devices showed shifts in threshold voltage and saturation current, and these shifts saturated in less than 1-million cycles. These shifts are believed to be induced by the trapping of the holes generated in the impact ionization (I. I.). The device's post-stress recovery was found to be dominated by the hole de-trapping and through-gate removal, which highly depends on the gate stack. The gate injection transistor showed a fast natural recovery benefitted from the efficient hole removal through the Ohmic gate. The hole de-trapping in the Schottky-type p-gate HEMT can be described by the Poole-Frenkel emission, allowing for the accelerated recoveries at negative gate bias and high temperatures. The hole removal in the metal-insulator-semiconductor (MIS) HEMT is blocked by the gate insulator, preventing a natural recovery. The MIS-HEMT can be recovered by applying positive gate and substrate biases, which facilitate the hole recombination in the channel. This work shows the good overvoltage robustness of all three GaN HEMTs and unveils effective methods for their post-stress recovery, as well as suggests the significant impacts of I. I. and hole dynamics on the overvoltage ruggedness of GaN HEMTs near BVdyn.
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering