Electrical properties of metal contacts on laser-irradiated <i>n</i>-type GaN

The electrical properties of metal contacts on laser-irradiated n-type GaN were investigated using synchrotron radiation photoemission spectroscopy. A KrF excimer laser pulse of 600 mJ/cm2 onto GaN led to a decrease in the Ni Schottky barrier height from 0.91 to 0.47 eV, resulting in the formation of a nonalloyed Ohmic contact with a specific contact resistivity of 1.7×10−6 Ω cm2. Metallic Ga decomposed from GaN by laser irradiation was transformed into GaOx, playing a role in promoting outdiffusion of N atoms. A large number of N vacancies were produced, forming a degenerated GaN layer near the surface, resulting in the good Ohmic contact.