SELENIUM TREATED (110) SURFACES OF GAAS AND INP - VALENCE-BAND AND GEOMETRIC STRUCTURE

The molecular beam deposition of selenium onto ultra-high-vacuum cleav ed (110) surfaces of GaAs and InP and subsequent annealing leads to th e formation of a thin, stable, Se rich reacted layer with distinct str uctural and electronic properties. The Se treated surfaces were invest igated using both angle resolved core level and valence band soft X-ra y photoemission spectroscopies at the TGM2 beamline of the BESSY stora ge ring in order to determine the Se induced surface band structure an d the geometric arrangement within the Se modified layer. The surface bands were determined along the GAMMABAR-XBAR and the GAMMABAR-XBAR' d irections of the substrate. The comparison between clean cleaved and S e treated surfaces reveals strong modifications due to the Se incorpor ation. An ordered arrangement of the Se atoms gives rise to diffractio n effects in the photoemission signals. The diffraction patterns were calculated for different Se adsorption models using the multiple scatt ering cluster approximation with spherical wave corrections (MSCA-SWC) .