Halogen diffusion on a Ga-stabilized $\zeta$-GaAs(001)–(4 $\times$ 2) surface

The atomic and electronic structure of a Ga-stabilized GaAs(001) surface with the $\zeta$(4 $\times$ 2) reconstruction and halogens in a number of symmetric sites on the surface are calculated by the plane-wave projector augmented wave method. The energy barriers of halogen-atom diffusion on this surface are calculated, which allow determination of the most preferred paths of their migration. It is shown that there is a low barrier (0.17–0.23 eV) for the diffusion of all halogens under consideration (I, Br, Cl, F) along the surface gallium dimer, whereas the barrier is significantly higher for diffusion between adjacent gallium dimers. In general, the energy barriers for halogen diffusion in both directions ([110] and [1–10]) point to their high surface mobility, despite high binding energies at a number of surface adsorption sites.