Effects of Annealing on the Interface Properties between Ni and p-GaN

The effects of annealing on the interface properties between p-GaN and Ni were investigated by ultra-violet photoemission spectroscopy. Photoemission spectra of p-GaN showed the existence of oxidized Ga, however, the oxidized Ga disappeared by Ni deposition. In addition, photoemission spectra of Ni/p-GaN after annealing showed the generation of metal-like Ga and the formation of Ni islands. These results indicate that the Ni deposition on GaN and subsequent annealing have an effect of making clean surface of GaN. Such cleaning effect and the island formation may play an important role in ohmic contact formation.