GaN(0001) Surface Structures Studied Using Scanning Tunneling Microscopy and First-Principles Total Energy Calculations

Surface reconstructions occurring on the (0001) surface of wurtzite GaN are studied using scanning tunneling microscopy, electron diffraction, and Auger electron spectroscopy. The family of reconstructions found on this face includes 2×2, 5×5, 6×4, and “1×1”, in order of increasing surface Ga/ N ratio. Detailed experimental results are presented for each of these reconstructions. First-principles total energy calculations are employed to identify possible model structures. An adatom model, with N-adatoms occupying H3 sites, is proposed for the 2×2 reconstruction. A model composed of N-adatoms, Ga-adatoms, and Ga-vacancies is proposed for the 5×5 reconstruction.