| Abstract: | We experimentally evaluated the interface state density of Ga N MIS-HEMTs during time-dependent dielectric breakdown(TDDB). Under a high forward gate bias stress, newly increased traps generate both at the Si Nx/Al Ga N interface and the Si Nx bulk, resulting in the voltage shift and the increase of the voltage hysteresis. When prolonging the stress duration, the defects density generated in the Si Nx dielectric becomes dominating, which drastically increases the gate leakage current and causes the catastrophic failure. After recovery by UV light illumination, the negative shift in threshold voltage(compared with the fresh one) confirms the accumulation of positive charge at the Si Nx/Al Ga N interface and/or in Si Nx bulk, which is possibly ascribed to the broken bonds after long-term stress. These results experimentally confirm the role of defects in the TDDB of Ga N-based MIS-HEMTs. |
