Investigation of Halogen Interaction with the Ga-rich GaAs(001) Surface

Atomic and electronic structures for a number of GaAs(001) surface geometries were studied within the density functional theory in order to re-examine the energy stability of surface reconstructions in the Ga-rich limit. It was confirmed that among geometries with (4×2) symmetry so-called ζ-model is most stable but the Ga-rich (2×4) reconstructions stabilized by dimerized Ga and As atoms are found to be energetically favored. Comparative study of the halogens (F, Cl, I) adsorption on the -GaAs(001)-(4×2) surface were performed. The energetically preferable positions for all considered halogens are found on-top sites above dimerized and undimerized Ga atoms. The electronic properties of the semiconductor surface and its change upon halogen adsorption are discussed. It was shown that the interaction of halogen with the Ga dimerized atoms leads to the weakening of the chemical bonds between surface atoms that determines the initial stage of surface etching.