Photochemical Production of Metallic Gallium on Cleaved GaAs Surfaces: Time-Resolved Measurements using Laser and Synchrotron Radiation,

In the course of investigations of electronic processes on laser excited semiconductor surfaces cleaved in ultrahigh vacuum, we have discovered the accumulation of Ga islands on GaAs 110 induced by laser pulse fluences far below those previously reported for irreversible surface modification. We have characterized these islands by core and valence photoelectron spectroscopy and by scanning electron microscopy. The photoemission spectra show a satellite of lower binding energy in the Ga 3d spectra which grows along with a metallic edge in the band gap. Because the Ga islands can be produced at fluences as low as 1 mJcm2, for which the lattice temperature rise is insignificant, as described below, it is evident that a photochemical decomposition of the GaAs surface is occurring.