Investigation of Performance Degradation in Enhancement-Mode GaN HEMTs under Accelerated Aging

In this paper, the performance degradation of enhancement-mode (E-mode) GaN HEMFs under accelerated aging is presented in detail. A real-time degradation monitoring tool is essential to prevent costly shutdowns and minimize safety concerns. Specifically, a DC power cycling setup is first designed which operates within the safe operating area (SOA) of the device to mimic the field operation and accelerate the aging process. The E-mode GaN devices are mounted on a custom designed PCB adaptor to accommodate the curve tracer where all the parasitics are carefully controlled to minimize the measurement errors. Using the curve tracer, the parameter shifts are periodically monitored at certain aging cycles. From the experimental results, it is observed that the on-state resistance and the threshold voltage are gradually increasing over the aging cycles, which makes it potential failure precursors. Meanwhile, a variation in the transfer characteristics is observed, and the transconductance decreases as the device is aged. Finally, a detailed theoretical analysis is provided to explain this parameter shift in experiments.