Ga adatom diffusion on an As-stabilized GaAs(001) surface via missing As dimer rows: First-principles calculation

We have investigated the microscopic processes of Ga adatom diffusions on an As-stabilized GaAs(001) surface by the first-principles pseudopotential method. The results show that Ga adatoms diffuse on the surface by passing through the missing As dimer rows. Comparison with the results of scanning tunneling microscopy (STM) experiments during molecular beam epitaxy (MBE) growth suggests that low As pressure increases the surface Ga adatom diffusion by a formation of the continuous Ga adatom diffusion path. This is consistent with the fact that low temperature growth is possible by migration enhanced epitaxy (MEE), in which As and Ga sources are supplied alternately.