Improvement of breakdown characteristics of AlGaN/GaN HEMT with U-type gate foot for millimeter-wave power application

In this study, physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of AlGaN/GaN high electron mobility transistor (HEMT) with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for U-gate device. U-gate AlGaN/GaN HEMTs are of great feasibility through adjusting the etching conditions of inductively coupled plasma system, without introducing any extra process step. The simulation results are confirmed by the experimental measurements. These features indicate that U-gate AlGaN/GaN HEMTs might be promising candidates for millimeter-wave power application.