A PHOTOEMISSION-STUDY OF THE (2 X-2) RECONSTRUCTIONS OF GAAS 111) SURFACES

The [111] surfaces GaAs have been examined using soft X-ray photoemiss ion (SXPS) following the thermal desorption of a protective As cap. A change in As and Ga 3d core-level lineshape has been correlated with a known phase transition from an As-trimer (2 x 2) reconstruction to a Ga-vacancy (2 x 2) with increasing temperature. The photoemission from the Ga-vacancy surface is found to be very similar to the cleaved (11 0) surface, on which a rehybridization occurs resulting in the separat ion of empty and filled surface orbitals on to Ga and As atoms respect ively. The (111)B surface also yields a (2 x 2) reconstruction after d e-capping, with the As-rich nature of the As-trimer reconstruction cau sing the Ga emission to be entirely bulk-like. Two surface components are found in the As 3d emission, which are attributed to trimer and re st-atom features on the surface.