Insulating gallium oxide layer produced by thermal oxidation of gallium-polar GaN

The benefits of dry oxidation of n -GaN for the fabrication of metal-oxide-semiconductor structures are reported. GaN thin films grown on sapphire by MOCVD were thermally oxidized for 30, 45 and 60 minutes in a pure oxygen atmosphere at 850 °C to produce thin, smooth GaO_x layers. The GaN sample oxidized for 30 minutes had the best properties. Its surface roughness (0.595 nm) as measured by atomic force microscopy (AFM) was the lowest. Capacitance-voltage measurements showed it had the best saturation in accumulation region and the sharpest transition from accumulation to depletion regions. Under gate voltage sweep, capacitance-voltage hysteresis was completely absent. The interface trap density was minimum (D_it = 2.75×10¹⁰ cm^-2eV^-1) for sample oxidized for 30 mins. These results demonstrate a high quality GaO_x layer is beneficial for GaN MOSFETs.