Published in J. Vac. Sci. Technol. A 16, 1641 (1998).

Wurtzite GaN Surface Structures Studied by Scanning Tunneling Microscopy and Reflection High Energy Electron Diffraction

A. R. Smith, V. Ramachandran, 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

We report studies of the surface reconstructions for both the Ga-face and the N-face of wurtzite GaN films grown using molecular beam epitaxy. N-face reconstructions are primarily adatom-on-adlayer structures which can be formed by room temperature sub-monolayer Ga deposition. These structures undergo reversible order-disorder phase transitions to 1x1 in the temperature range of 200-300°C. Ga-face reconstructions, on the other hand, require annealing to high temperatures (600-700°C) in order to form, and in most cases they are stable at those temperatures. The film polarity is found to be determined by the initial nucleation stage of the film growth.

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