Atomic and electronic structure of N-terminated GaN(000) (1 × 1) surface

The atomic and electronic structures of the polar GaN(000) surface were investigated by x-ray photoelectron diffraction (XPD) and ab initio density-functional theory (DFT) calculations. A well-ordered GaN(000) surface of a free-standing GaN wafer was prepared by sample annealing in a NH₃ atmosphere. A N-terminated bare (1 × 1) structure was confirmed. An electronic band structure was investigated by DFT calculations. The surface state at the top of the valence band was localized for a relaxed (1 × 1) structure. The energy loss function (ELF) was computed in the framework of the many-body perturbation theory. Plasmon loss peak positions were found to be in good agreement with reflection-electron energy loss spectroscopy (REELS) measurements.