Dynamic OFF-State Current (Dynamic I_OFF) in p-GaN Gate HEMTs with an Ohmic Gate Contact

The OFF-state drain leakage characteristics in 600-V p-GaN HEMTs with an ohmic gate contact are investigated under dynamic switching conditions instead of commonly used quasi-static measurement setup. It is found that fast dynamic OFF-state leakage current (dynamic I_OFF) is substantially higher than the slow-ramping quasi-static I_OFF due to the weaker trapping effect in the buffer layer. With sufficiently large positive ON-state gate bias, further increase in dynamic I_OFF is observed and is attributed to ON-state hole injection that leads to energy band lowering in the buffer. The underlying physical processes are explained by the dynamic behavior of the traps in the buffer layer. This letter indicates that the I_OFF under practical switching operations is much higher than the static measurement results and should be used to evaluate dynamic OFF-state power consumption in the p-GaN HEMTs with an ohmic gate contact.