Improvement of electrical and optical properties of p-GaN Ohmic metals under ultraviolet light irradiation annealing processes

We report the improvement of electrical and optical properties of p-GaN Ohmic metals, ZnNi(10nm)∕Au(10nm), by ultraviolet (UV) light irradiation. After UV light irradiation, the specific contact resistance of p-GaN decreased slightly from 2.99×10−4to2.54×10−4Ωcm2, while the transmittance of the contact layer increased form 75% to 85% at a wavelength of 460nm. In addition, the forward voltage of InGaN∕GaN light-emitting diode chip at 20mA decreased from 3.55to3.45V, and the output power increased form 18to25mW by UV light irradiation. The low resistance and high transmittance of the p-GaN Ohmic metals are attributed to the reduced Shottky barrier by the formation of gallium oxide and the increased oxidation of p-Ohmic metals, respectively, due to ozone generated form oxygen during UV light irradiation.