Degradation and Recovery of GaN HEMTs in Overvoltage Hard Switching Near Breakdown Voltage

Joseph P. Kozak, Qihao Song, Ruizhe Zhang, Yunwei Ma, Jingcun Liu, Qiang Li, Wataru Saito, Yuhao Zhang

    Research output: Contribution to journalArticlepeer-review

    19 Citations (Scopus)


    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 article 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 poststress recovery was found to be dominated by the hole detrapping 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 detrapping 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 article shows the good overvoltage robustness of all three GaN HEMTs and unveils effective methods for their poststress recovery, as well as suggests the significant impacts of I. I. and hole dynamics on the overvoltage ruggedness of GaN HEMTs near BVdyn.

    Original languageEnglish
    Pages (from-to)435-446
    Number of pages12
    JournalIEEE Transactions on Power Electronics
    Issue number1
    Publication statusPublished - Jan 1 2023

    All Science Journal Classification (ASJC) codes

    • Electrical and Electronic Engineering


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