Impact of surface photovoltage on photoemission from Ni/p-GaN

Abstract Surface studies on the Ni films on p-GaN concentrated on photoelectron spectroscopies are presented. We found the surface condition on which the surface photovoltage (SPV) effect, caused by an excitation source, leads to the appearance of a quasi-Fermi level located above the Fermi level of the electron energy analyzer. The energy shifts of core-level lines were also noted due to this. This means that for meta/semiconductor systems some energy shifts of peaks observed do not have to result from a chemical reaction and may be done through SPV effects. The formation of the interface, as well as its physicochemical and structural analysis, were carried out in situ under ultrahigh vacuum. Ni films were vapour deposited onto the Mg-doped GaN, (0 0 0 1)-oriented. X-ray and ultraviolet light sources were applied in photoemission experiments. The low-energy electron diffraction technique was employed for surface structure investigation.