Monte Carlo methods were used to model the adatom migration of cations in AlxGa1-xAs, where x was equal to 0, 0.5 or 1, and the resultant atomic arrangements on a reconstructed As-stabilized GaAs(001) surface with an adatom coverage of up to 0.5. It was found that the cation adatom migration depended strongly upon the adatom coverage of the surface. Randomly impinging cations occupied lattice sites on the As dimers at coverages of less than 0.1. As the coverage was increased from 0.1 to 0.3, the impinging cations migrated mainly along the missing dimer rows. At a coverage of more than 0.3, adatoms tended to favor lattice sites on the As dimers; including those with non-tetrahedral coordination. In the case of Al0.5Ga0.5As, lattice sites along the missing dimer were occupied mainly by Al adatoms, while those on As dimers were favored by Ga adatoms. This was because Al adatom migration was several times slower than Ga adatom migration. The resultant atomic arrangements were explained in terms of a coverage dependence of the migration potential.

T.Ito, K.Shiraishi, T.Ohno: Applied Surface Science, 1994, 82-83, 208-13