Effects of passivation on breakdown voltage and leakage current of normally-off InAlN/GaN MISHFETs—a simulation study

Effects of passivation on breakdown characteristics of normally-off InAlN/GaN MISHFETs have been investigated via physics based simulations. The product of passivation layer permittivity and thickness is found to dramatically affect breakdown voltage, due to alleviation of peak electric field at the gate edge on the drain side, leading to a much smoother field distribution in the channel. A proposed structure with a 985 nm TiO2 top and 15 nm HfO2 bottom passivation stack exhibits a breakdown at ~750 V with leakage current ~4 μA mm−1, showing ~15× increase in breakdown voltage compared to the structure without the TiO2 top layer (50 V).