The Device Instability of p-GaN Gate HEMTs Induced by Self-Heating Effect Investigated by on-State Drain Current Injection (DCI) Technique

In this work, the device stability of p-GaN gate HEMTs under self-heating effect is comprehensively investigated by the ON-state drain current injection (DCI) technique. By delicately modulating the DCI condition, the devices exhibit different chip temperatures ranging from 40 °C to 150 °C, while the devices show quite distinguishing instability behaviors. Particularly, substantial threshold voltage shift and saturation drain current degradation is constantly observed in the device with severe self-heating effect after DCI stress. Significant ${V}_{\text{th}}$ shift of +0.83 V and saturation current reduction up to 18% are observed after the DCI stress, corresponding to a chip temperature of ~150 °C. After the device degradation, the device characteristics show a recoverable dynamic. By investigating the gate leakage current together with the electrothermal device TCAD simulation, ${V}_{\text{th}}$ instability induced by the self-heating is revealed to be the electron trapping in the p-GaN gate-stack, while the saturation drain current degradation originates from a composited action of thermally enhanced electron trapping/de-trapping in p-GaN gate-stack as well as the access region at the hot spot close to the source field plate. The results reported in this work suggest that self-heating is a critical issue that may cause unstable operation of p-GaN gate HEMTs. The revealed underlying mechanisms are beneficial for further improving device stability.