Transient voltage overshoot is a common phenomenon in GaN high electron mobility transistors (HEMTs) under high slew rate switching conditions. The dynamic parametric instability under such stress is a critical concern for GaN applications. This work, for the first time, accurately characterized the evolution of dynamic on-resistance (R_DS(on)) in GaN HEMTs under repetitive voltage overshoot up to billions of switching cycles. The dynamic R_DS(on) increase was found to be the dominant device degradation under overvoltage switching. Such findings were obtained from a high-frequency, repetitive, unclamped inductive switching (UIS) test with active temperature control and accurate in-situ R_DS(on) monitoring. A physics-based model was proposed to correlate the dynamic R_DS(on) drift with the peak overvoltage, and a good agreement with experimental data was achieved. This model was further used to project the lifetime of GaN HEMTs. For 100 V rated GaN HEMTs switched under 100 kHz and 120 V spikes, the model projects less than 10% dynamic R_DS(on) shift over 25 years of continuous operation. This work addresses the major concerns of overvoltage switching reliability of GaN HEMTs and provides new insights of the electron trapping mechanism.

IEEE Xplore
Ruizhe Zhang, Ricardo Garcia, Robert Strittmatter, Yuhao zhang, Shengke Zhange
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