AlGaN/GaN high-electron-mobility transistors with transparent gates by Al-doped ZnO

AlGaN/GaN high-electron-mobility transistors(HEMTs) with Al-doped ZnO(AZO) transparent gate electrodes are fabricated,and Ni/Au/Ni-gated HEMTs are produced in comparison.The AZO-gated HEMTs show good DC characteristics and Schottky rectifying characteristics,and the gate electrodes achieve excellent transparencies.Compared with Ni/Au/Ni-gated HEMTs,AZO-gated HEMTs show a low saturation current,high threshold voltage,high Schottky barrier height,and low gate reverse leakage current.Due to the higher gate resistivity,AZO-gated HEMTs exhibit a current-gain cutoff frequency(fT) of 10GHz and a power gain cutoff frequency(fmax) of 5GHz,and lower maximum oscillation frequency than Ni/Au/Ni-gated HEMTs.Moreover,the C-V characteristics are measured and the gate interface characteristics of the AZO-gated devices are investigated by a C-V dual sweep.