Published in Phys. Rev. B 68, 205317 (2003).

Reconstructions of the AlN(0001) Surface

C. D. Lee (a), Y. Dong (a), R. M. Feenstra (a), J. E. Northrup (b), and J. Neugebauer (c)
(a) Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
(b) Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, California 94304
(c) Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany


Reconstructions of the AlN(0001) surface are studied. For moderately Al-rich surfaces, surface reconstructions with symmetry of 2rt(3)x2rt(3)-R30 deg and 5rt(3)x5rt(3)-R30 deg are found on the basis of scanning tunneling microscopy and low-energy electron diffraction observations. Such surfaces display a predominantly 2x6 pattern in reflection high-energy electron diffraction. Auger electron spectroscopy indicates an Al coverage for such surfaces of 2-3 monolayers. Based on this result and on first principles total energy calculations it is argued that these reconstructions involve a laterally contracted Al adlayer structure similar to that previously proposed for GaN(0001). At higher Al coverages a thick, flat Al film is found to form on the surface. For Al-poor conditions, additional surface reconstructions with rt(3)xrt(3)-R30 deg and 2x2 periodicities are observed.

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