ELECTRONIC-PROPERTIES OF ANTIMONY MONOLAYERS ON III-V (110)SURFACES -A COMPARATIVE-STUDY BY REFLECTANCE ANISOTROPY SPECTROSCOPY AND MICROSCOPIC TIGHT-BINDING CALCULATIONS

A systematic investigation of the structural, electronic and optical p roperties (by means of Raman spectroscopy and reflectance anisotropy s pectroscopy (RAS)) has been done for clean and antimony-covered(110) G aAs, InP, InAs, and GaP surfaces, We present here the theoretical inte rpretation of the experimental reflectance anisotropy spectra for InAs (110) and GaP(110) surfaces, both clean and Sb covered. The different contributions to the optical spectra, originating from surface-to-surf ace (SS), bulk-to-bulk (BB) and mixed surface-to-bulk (SB) and bulk-to -surface (BS) state transitions, are discussed in detail on the base o f microscopic calculations, Good agreement of the theoretical results and experimental data allows us to clarify the origin of the surface o ptical modification during Sb adsorption, The appearance of strong exc itonic effects for clean and Sb-covered GaP(110) surfaces is hypothise d.