Reduction of gate leakage current in AIGaN/GaN MOSHFET using NiO

AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) were fabricated by using thermally oxidized Ni (NiO) as a gate insulator and a surface passivation layer. NiO was prepared by oxidizing Ni metal of 100 Å at 300 - 600°C for 5 min in air ambient. Auger electron spectroscopy revealed that NiO was formed with a thickness of NiO greater than the initial thickness of the Ni metal. As the oxidation temperature increased, the gate leakage current decreased dramatically due to the formation of insulating NiO. The gate leakage current of the NiO-MOSHFET was about four orders of magnitude smaller than that of the HFET. NiO-MOSHFET showed no current collapse because NiO passivation of the AlGaN surface prevented trapping of electrons at the surface.