Indium surface diffusion on InAs (2×4) reconstructed wetting layers on GaAs(001)

In this paper we present a study of In surface diffusion on InAs wetting layers deposited on the (001) surface of GaAs. The α₂(2×4) and β₂(2×4) reconstructions stabilized by a high In concentration are considered. The low symmetry of the α₂(2×4) reconstruction allowed us to understand the effect of the wetting-layer symmetry on the adsorbate diffusion. We find that (i) the diffusion coefficient value is larger for In motion on the α₂ reconstruction than on the β₂ reconstruction. This is due to the presence on β₂ of an additional As dimer that rises locally the potential energy surface and offer an additional site to which the In adatom can bind strongly. (ii) The In adsorption sites located within the As dimers have to be taken into account properly for these specific reconstructions, since they greatly affect the value of the diffusion coefficient. This is in contrast to what happens for the other reconstructions reported in the literature. (iii) The adsorbate diffusion is highly anisotropic with the [1̅ 10] direction favored over the [110] direction, due to the presence of low-potential channels along [1̅ 10]. (iv) The anisotropy is slightly smaller on the α₂ reconstruction than on the β₂ reconstruction because on the β₂ there is an additional diffusion channel along the [1̅ 10] direction.