H2S ADSORPTION ON THE (110) SURFACES OF III-V SEMICONDUCTORS

The adsorption of H2S on cleaved (110) surfaces of InP, GaP and GaAs h as been studied by core level soft X-ray photoelectron spectroscopy (S XPS) and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) using synchrotron radiation. H2S adsorption occurs at room temperatur e on InP and GaP. At low exposures (up to 5 L) the surface component o f the cation spectra (In 4d, Ga 3d) is strongly reduced while that of the P 2p core level spectra is replaced by a component at higher bindi ng energy. The S 2p spectrum shows a single component and the valence band spectra show sharp new features. This adsorbate can be removed by gentle annealing. Adsorption on GaAs does not occur at room temperatu re, but low temperature (200 K) adsorption yields SXPS and ARUPS spect ra which indicate that this low exposure adsorption process is essenti ally the same for all three substrates. A model of dissociative adsorp tion consistent with these photoelectron data is presented.