Temperature dependent diffusion and epitaxial behavior of oxidized Au/Ni/p-GaN ohmic contact

The temperature dependent diffusion and epitaxial behavior of oxidized Au/Ni/p-GaN ohmic contact were studied with Rutherford backscattering spectroscopy/channeling (RBS/C) and synchrotron X-ray diffraction (XRD). It is found that the Au diffuses to the surface of p-GaN to form an epitaxial structure on p-GaN after annealing at 450 °C. At the same time, the O diffuses to the metal–semiconductor interface and forms NiO. Both of them are suggested to be responsible for the sharp decrease in the specific contact resistance (ρc) at 450 °C. At 500 °C, the epitaxial structure of Au develops further and the O also diffuses deeper into the interface. As a result, the ρc reaches the lowest value at this temperature. However, when annealing temperature reaches 600 °C, part or all of the interfacial NiO is detached from the p-GaN and diffuses out, which cause the ρc to increase greatly.