Localized Excitons and Breaking of Chemical Bonds at III-V (110) Surfaces

Abstract

Electron-hole excitations in the surface bands of GaAs(110) are analyzed using constrained density-functional theory calculations. The results reveal formation of autolocalized Frenkel-type excitons which merge in microscopic ``droplets'' due to attraction initiated by exciton-induced unrelaxation of the surface. A substantial weakening of the bonding of the topmost Ga atom is found in such an ``exciton droplet.'' This finding suggests a microscopic mechanism of laser-induced emission of the neutral Ga atoms from GaAs and GaP (110) surfaces.