Influence of various annealing temperatures on microstructure evolution of oxidized Ni/Au ohmic contact to p-GaN studied by synchrotron X-ray diffraction

Abstract The influence of various annealing temperatures on microstructure evolution of oxidized Ni(20 nm)/Au(20 nm) ohmic contact to p-GaN was studied by synchrotron X-ray diffraction (XRD). In association with the variation of the specific contact resistance ( ρ c ), it is observed that NiO and Au began to form partially epitaxial structure on p-GaN at 450 °C, which played a critical role in lowering down the ρ c . At 500 °C, the epitaxial structure of Au and NiO was improved further while the lowest ρ c was reached. However, at 600 °C, the epitaxial structure of NiO was transformed to polycrystalline structure again with a sharp increase of ρ c . Therefore, it is suggested that the degradation of the epitaxial structure of NiO is responsible for the sharp increase of ρ c .