Low-resistance ohmic contacts to p-type GaN

Low-resistance ohmic contacts with high transparency to p-type GaN have been developed by oxidizing Ni/Au thin films. Compared to the metallic Ni/Au contacts, the oxidized Ni/Au contacts exhibited lower specific contact resistance and much improved transparency. The transparency was from 65% to 80% in the wavelength of 450–550 nm. A specific contact resistance below ${\text{1.0×10}}^{\text{−4}}\mathrm{ \Omega }{\mathrm{cm}}^{\mathrm{2}}$ was obtained by oxidizing Ni(10 nm)/Au(5 nm) on p-type GaN. The mechanism of low-resistance ohmic contact could be related to the formation of NiO.