AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors with ZnO gate layer and (NH4)2Sx surface treatment

Abstract

The AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) with ZnO gate insulator deposited using a vapor cooling condensation system were fabricated. The AlGaN surface treatment using (NH4)2Sx was performed to improve the quality of the interface between the ZnO layer and AlGaN layer. The (NH4)2Sx-treated MOS-HEMTs exhibited a higher saturation drain-source current of 0.74 A/mm, a maximum extrinsic transconductance of 200 mS/mm, an unit gain cutoff frequency of 9.1 GHz, a maximum frequency of oscillation of 17.1 GHz, and the Hooge’s coefficient of 8.28×10−6. The improved performances of the (NH4)2Sx-treated MOS-HEMTs were attributed to the reduction in surface states.