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Abstract: The barrier effect of Pt and Ni has been investigated in the Ti/Al/Pt/Au and Ti/Al/Ni/Au Ohmic contacts to n-GaN, respectively. Severe indiffusion of Pt and Au has been found in the 800°C annealed Au/Pt/Al/Ti/n-GaN samples. However, Ni does not penetrate into the n-GaN and shows better barrier effect for preventing Au penetration into Au/Ni/Al/Ti/n-GaN samples. The reaction between Ga and Pt has also been identified in the samples annealed at 600°C. At the same time, the electrical degradation was found for the Ti/Al/Pt/Au samples aged at 600°C. However, no obvious degradation was found for the aged Ti/Al/Ni/Au samples. It is suggested that the reaction between Ga and Pt may cause the electrical degradation of the Ti/Al/Pt/Au metallization system. [Copyright &y& Elsevier]

Abstract: The influence of various annealing temperatures on microstructure evolution of oxidized Ni(20nm)/Au(20nm) 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. [Copyright &y& Elsevier]

Abstract: The annealing time-dependent diffusion behavior of oxidized Au/Ni/p-GaN ohmic contact was studied with Rutherford backscattering spectroscopy/Channeling (RBS/C). It was found that, at 500°C, 1min annealing caused obvious indiffusion of Au, O and outdiffusion of Ni. And the Au even has diffused to the p-GaN/metal interface. According to the annealing time-dependent RBS spectra and referring to the correspondent specific contact resistance of the samples, it is suggested that indiffusion of Au and formation of NiO at the interface are among the critical mechanisms for the formation of low resistance ohmic contact with Au/Ni/p-GaN contact structure. [Copyright &y& Elsevier]