AlGaN/GaN MOS-HEMTs With Gate ZnO Dielectric Layer

The vapor cooling condensation system is used to grow ZnO insulator films of low carrier concentration and high resistivity as the gate dielectrics for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs). The saturation drain-source current and the maximum extrinsic transconductance are measured as 0.61 A/mm and 153 mS/mm, respectively. The gate leakage currents, determined with the forward gate bias of V-GS = 3.5 V and the reverse gate bias of V-GS = -12 V, applied are 1.21 x 10(-4) A/mm and 7.16 x 10(-6) A/mm, respectively. The unit gain cutoff frequency and maximum frequency of the oscillation are also measured as 7.2 and 11.5 GHz, respectively. The low-frequency noise obtained is well fitted with a 1/f function in the linear region. Hooge's coefficient a is extracted as 9.74 x 10(-5) when the MOS-HEMTs operate at 100 Hz and V-GS = -4 V. The current recoveries of the gate and drain lags are determined to be 61% and 47% for the MOS-HEMTs, respectively.