Improved breakdown voltage and dynamic R_on characteristics in normally-off GaN-based HEMTs featuring fully-recessed and bilayer-dielectric gate structure

Abstract The degradation of dynamic on-resistance ( R on ) is a major challenge in GaN-based high electron mobility transistors, which seriously affects their performance and reliability. The degradation area of dynamic R on mainly comes from two aspects. One is the region below the gate that also affects the threshold voltage ( V th ) of the devices. The other one is the interface region of the gate to drain access. The optimal device exhibits a V th of 0.97 V, a small V th hysteresis of only 20 mV, a high current density of 723 mA mm −1 , and a breakdown voltage of 810 V which can be further boosted when additional field plate design is employed. It is found that when high voltage drain stress is applied, a positive V th shift is induced, leading to a decrease in the effective gate driving voltage, and thus the dynamic R on of the devices is increased. Of particular concern are the effects of dielectric layer and/or interface of the access region on the dynamic R on degradation, which can be alleviated by removing the dielectric layer from the access region.