Low-resistant and high-transparent Ru/Ni ohmic contact on p-type GaN

We report a low-resistant and high-transparent Ru-based ohmic contact on p-type GaN through oxidation annealing under O2 atmosphere. A low resistivity of 4.5×10−5 Ω cm2 and high light transmittance (84.6%) were simultaneously obtained from oxidized Ru (50 Å)/Ni (50 Å) contact. The RuO2 formed on p-type GaN played a role in reducing the effective Schottky barrier height for injection of holes and NiO layer produced on the RuO2 acted as a diffusion barrier for the outdiffusion of released Ga and N atoms, resulting in the reduction of the contact resistivity as well as the enhancement of light transmission.