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 Angstrom at 600 degreesC for 5 min in air ambient. For HFET and MOSHFET with a gate length of 1.2 mum, 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 degreesC 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 degreesC 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. (C) 2004 American Institute of Physics.