XPS analysis of surface chemistry of near surface region of epiready GaAs(1 0 0) surface treated with (NH4)2Sx solution

In this work we analyze the effect of (NH)2Sx wet treatment on the GaAs(1 0 0) covered with ‘‘epiready’’ oxide layer without any pretreatment in order to check the removal of oxides and carbon-related contamination, and the formation of sulfur species. The sulfidation procedure consisted of epiready sample dipping (at room and 40 8C temperatures) in an ammonium polysulfide solution combined with a UHV flash annealing up to 500 8C. The inspection of the XPS As 2p3/2 and Ga 2p3/2 spectra taken at surface sensitive mode revealed: (i) the temperature-dependent reduction of the amount of GaAs oxides and carbon contamination after sulfidation, and almost their complete removal after subsequent annealing, (ii) the creation of sulfur bonds with both Ga and As, with more thermally stable Ga–S bonds, and (iii) the slight reduction in elemental arsenic amount.