Structure and energetics of Ga-rich GaAs(0 0 1) surfaces

The atomic structures and energies of Ga-rich GaAs(0 0 1) surface reconstructions are examined by means of first-principles total-energy calculations based on a real-space multigrid method. Our calculations confirm the existence of the novel ζ(4×2) structure suggested by Lee et al. [Phys. Rev. Lett. 85 (2000) 3890]. (4×6) surface reconstructions suggested to explain STM experiments are found to be unstable. The calculations indicate that the adsorption of Ga adatoms in the trenches of the ζ(4×2) surface could possibly explain the observed structures. The diffusion of Ga/As adatoms on the Ga-rich GaAs surface is predicted to be anisotropic and should preferably take place parallel to the [1 1 0]/[1 1̄ 0] direction, respectively.