AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistor with oxidized Ni as a gate insulator

We fabricated the AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistor (MOSHFET) using the oxidized Ni(NiO) as a gate oxide and compared electrical properties of this device with those of a conventional AlGaN/GaN heterostructure field-effect transistor (HFET). NiO was prepared by oxidation of Ni metal of 100 A at 600°C for 5 min in air ambient. For HFET and MOSHFET with a gate length of 1.2 μm, the maximum drain currents were about 800 mA/mm and the maximum transconductances were 136 and 105 mS/mm, respectively. As the oxidation temperature of Ni increased from 300 to 600°C the gate leakage current decreased dramatically due to the formation of insulating NiO. The gate leakage current for the MOSHFET with the oxidized NiO at 600°C was about four orders of magnitude smaller than that of the HFET. Based on the dc characteristics, NiO as a gate oxide is comparable with other gate oxides.