X-ray photoelectron spectroscopy study on effects of ultra-high-pressure annealing on surface of Mg-ion-implanted GaN

Abstract

The effects of ultra-high-pressure annealing (UHPA) on the surface of Mg-ion-implanted GaN were investigated by X-ray photoelectron spectroscopy (XPS). After Mg ion implantation or Mg–N co-implantation, GaN was annealed at 1400 °C for 5 min under a nitrogen pressure of 1 GPa. No deterioration of the surface stoichiometry occurred after UHPA despite the extremely high annealing temperature. The angle-resolved XPS with calibration showed that the surface Fermi level was pinned at 0.5 eV from the conduction band edge after dehydrogenation subsequent to UHPA. However, the absence of pinning at the charge neutrality level showed that surface disorder was absent after UHPA. The surface photovoltaic effect as evidence of the achievement of p-type conduction even in the near-surface region was more remarkable for Mg–N-ion-implanted samples after dehydrogenation subsequent to UHPA. There is the possibility that the density of N-vacancy-related defects was reduced more by Mg–N co-implantation.