Published in J. Cryst. Growth 209, 355 (2000).

Structure of Clean and Arsenic-covered GaN(0001) Surfaces

V. Ramachandran, C. D. Lee, and R. M. Feenstra
Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
A. R. Smith
Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701
J. E. Northrup
Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, California 94304
D. W. Greve
Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213


The effect of trace arsenic on the growth and surface structure of GaN(0001) has been studied. We find that a partial pressure of only 10-9 Torr of arsenic during molecular beam epitaxial growth significantly modifies the growth kinetics. Such a small background pressure of arsenic leads to an arsenic-terminated surface displaying a 2x2 reconstruction during growth which is absent for the clean surface. First-principles theoretical calculations show that As-terminated surfaces are energetically more favorable than Ga-terminated surfaces for arsenic pressures of 10-9 Torr, and structural models for the As-adatom 2x2 reconstruction are presented.

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