Published in Surf. Sci. 423, 70 (1999).

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

A. R. Smith, R. M. Feenstra
Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
D. W. Greve
Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
M.-S. Shin, M. Skowronski
Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
J. Neugebauer
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
J. E. Northrup
Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, California 94304

Abstract

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 2x2, 5x5, 6x4, and ``1x1'', 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 2x2 reconstruction. A model composed of N-adatoms, Ga-adatoms, and Ga-vacancies is proposed for the 5x5 reconstruction.

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