Evidence of Hot-Electron Degradation in GaN-Based MIS-HEMTs Submitted to High Temperature Constant Source Current Stress

This letter demonstrates that GaN-based MIS-HEMTs submitted to stress with high-temperature, high drain bias, and constant source current (HTSC stress) may show degradation modes that are not detectable during standard high temperature reverse bias (HTRB) stress. Based on a number of stress/recovery experiments, we demonstrate the following novel results: 1) the combined presence of high drain bias and constant drain-source current (HTSC stress) can lead to a significant increase in ON-resistance (RON) that is not detected under conventional HTRB stress; 2) RON increases without changes in the threshold voltage, indicating that charge trapping takes place in the access regions, and not under the gate; 3) the RON increase has a monotonic dependence on the source current flowing during stress; and 4) for the same stress current level, the RON increase has a negative dependence on temperature. The strong correlation between RON increase and source current and the negative temperature coefficient strongly support the hypothesis that trapping originates from the injection of hot electrons toward the gate-drain access region.