AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors using oxide insulator grown by photoelectrochemical oxidation method

A photoelectrochemical oxidation method was used to directly grow oxide layer on AlGaN surface. The annealed oxide layer exhibited β- Ga₂O₃ and α-Al₂O₃ crystalline phases. Using a photoassisted capacitance-voltage method, a low average interface-state density of 5.1 × 10¹¹ cm^-2 · eV^-1 was estimated. The directly grown oxide layer was used as gate insulator for AlGaN/GaN MOS high-electron mobility transistors (MOS-HEMTs). The threshold voltage of MOS-HEMT devices is -5 V. The gate leakage currents are 50 and 2 pA at forward gate bias of V_GS = 10 V and reverse gate bias of V_GS = -10 V, respectively. The maximum value of gm is 50 mS/mm of V_GS biased at -2.09 V.