N-Polar GaN Cap MISHEMT With Record Power Density Exceeding 6.5 W/mm at 94 GHz

A novel N-Polar GaN cap (MIS) high electron mobility transistor demonstrating record 6.7-W/mm power density with an associated power-added efficiency of 14.4% at 94 GHz is presented. This state-of-the-art power performance is enabled by utilizing the inherent polarization fields of N-Polar GaN in combination with a 47.5-nm in situ GaN cap layer to simultaneously mitigate dispersion and improve access region conductivity. These excellent results build upon past work through the use of optimized device dimensions and a transition from a sapphire to a SiC substrate for reduced self-heating.