X-ray absorption spectroscopy investigations on oxidized Ni/Au contacts top-GaN

X-ray absorption spectroscopy was used to investigate the electronic struct ure of as-deposited and oxidized Ni/Au contacts to p-GaN and to elucidate t he mechanism responsible for low impedance. X-ray absorption near edge spec tra of Ni K- and L-3,L-2-edges clearly indicate formation of NiO on the sam ple surface after annealing. The reason for low impedance may be attributed to increase in hole concentration and existence of p-NiO layer on the surf ace.