Evidence of Back-Gating and its Impact on Breakdown in GaN-on-Si HEMTs with Carbon Doped Buffer Under Pulsed Conditions

In this study we reveal that under pulsed conditions back-gating induced breakdown mechanism can take place in GaN-on-Si HEMTs with a carbon-doped buffer. Experiments and TCAD simulations depict that under pulsed stress, high dv/dt at the drain terminal results in a high voltage buildup in the substrate due to capacitive coupling, which acts as a back-gate. Source side channel electrons lose confinement due to the induced back-gate bias, resulting in the drain-to-source punch-through breakdown. DC breakdown mechanism is also studied for comparison and shows different breakdown mechanism compared to pulsed case. FE-SEM microscopy, experiments with field plate and rise time variations, and various substrate terminations help validate these findings.