We investigated the effect of different annealing atmospheres on contact behaviour of Ni/Au contacts on moderately doped p-GaN layers. We used the annealing gases N-2, O-2, Ar, and forming gas (N-2/H-2) at varying annealing temperatures from 350 degreesC to 650 degreesC in steps of 50 degreesC. The p-GaN samples were either metalorganic chemical vapor deposition or molecular beam epitaxy grown. Contact characterization was done after each annealing step by using the circular transmission line model. Specific contact resistances were determined to be in the low 10 (4)Omega cm(2) range for oxidized contacts. Accompanying chemical analysis using depth resolved Auger electron spectroscopy revealed that NiO was formed and Au diffused towards the interface, whereas annealing in forming gas prevented oxidation and did not lead to Ohmic behaviour.