Article PreviewArticle PreviewArticle PreviewIn this paper the structural and electrical evolution of Au/Ni contacts to p-type gallium nitride (GaN) upon annealing in different atmospheres was monitored. Rapid annealing of the contacts in an oxidizing atmosphere (N2/O2) resulted into a lower specific contact resistance (ρc) with respect to annealing in non-reacting ambient (Ar). The formation of a nickel oxide (NiO) layer was observed on the surface of the sample annealed in N2/O2, while was not present at the interface with p-GaN. The improvement of the contacts was associated with a reduction of the Schottky barrier height from 1.07 eV (Ar annealing) to 0.71 eV (N2/O2 annealing), as determined by the temperature dependence of the ρc. Local electrical measurements demonstrated the formation of inhomogeneous barriers. The electrical measurements were correlated with the different microstructure of the …