In-situ R DS(on) Characterization and Lifetime Projection of GaN HEMTs Under Repetitive Overvoltage Switching

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 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 into the electron trapping mechanism.