First-principles investigation of Ga adatom migration on a GaAs(111)A surface

The migration of Ga adatoms on a (1 1 1)A GaAs surface was investigated by calculating the total energy at various absorption sites by using the first-principles pseudopotential method. The Ga-vacancy structure, which has been experimentally observed, was assumed as the reconstructed surface structure. Although it was expected that the Ga-vacancy sites on the surface would be the most stable for Ga adatoms, the calculations showed that it is not. Some mechanisms stabilizing the Ga-vacancy sites may play an important role in epitaxial growth processes. Based on the obtained energy potential surface, the migration barrier height was estimated to be about 0.4 eV. This height is much lower than that for GaAs(0 0 1) surfaces, consistent with the observation of a rather long diffusion length for Ga adatoms on (1 1 1)A surfaces. (C) 1999 Elsevier Science B.V. All rights reserved.