Experimental and Simulation Study on the Failure Mechanism of GaN HD-GIT Under Overcurrent Stress

This article investigates the failure mechanisms of the gallium nitride high electron mobility transistors (GaN HEMTs) under overcurrent stress. The overcurrent behavior of GaN hybrid drain-embedded gate injection transistor (HD-GIT) devices was evaluated under different stress conditions, and the primary failure modes were identified. The waveforms of the GaN devices during overcurrent events were analyzed in stages, and the physical mechanisms underlying each stage were analyzed. Numerical technology computer-aided design (TCAD) simulations were conducted to analyze the electric field distribution and the variations in electron mobility during overcurrent stress. Both thermal runaway and drain/substrate breakdown failures were investigated through simulation analysis. The results indicate that thermal runaway failure in GaN HEMTs occurs due to the accumulation of thermal stresses in the access region, which is triggered by the reduction in electron mobility and an increase in the electric field within the channel. The drain and substrate breakdown failure are mainly caused by the high vertical electric field between the drain and substrate due to hole injection from the drain p-GaN region. Furthermore, the failure mechanisms were validated through experimental tests.