Investigations on SiN-Passivated Γ-Gate Al0.27Ga0.73N/GaN High Electron Mobility Transistors

SiN-passivated Gamma-gate Al0.27Ga0.73N/GaN high electron mobility transistors with different SiN layer thicknesses (15, 30, and 45 nm) have been comprehensively investigated over a wide temperature range of 300-450 K. By using the shifted exposure method, the effective reduction in gate length, the SiN surface passivation, and the formation of a 0.6 mu m long field plate upon the gate-drain region are achieved at the same time. The present Gamma-gate devices demonstrate improved device gain, current drive capability, wide temperature range linearity, and superior thermal threshold stability characteristics compared to a conventional device fabricated by using the identical optical mask. Different dependences among power and microwave/noise performances on the SiN thickness of the Gamma-gate devices are also studied. The proposed design provides good potential for high temperature, high gain, and high linearity circuit applications.