Structure and energetics of Ga-rich GaAs(001) 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 f(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 f(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 th