XPS study of surface chemistry of epiready GaAs(1 0 0) surface after (NH₄)₂S_x passivation

The results of systematic XPS studies of wet sulfide passivation capabilities to remove the native oxides and excess arsenic at the epiready GaAs(1 0 0) native surfaces are presented. Different procedures of dipping an epitaxy-ready sample (at room and elevated temperatures) in an ammonium polysulfide (NH₄)₂S_x solution combined with a UHV flash annealing were used. The surface chemistry after each processing step was investigated by the inspection of the XPS As3d and Ga3d spectra taken using an enhanced surface sensitivity mode. The analysis revealed that the procedure of sulfidation itself removes native oxides and that both As-S and Ga-S bondings are created, and when combined with subsequent UHV annealing, diminishes excess As efficiently. Moreover, the results are in agreement with our previous work on the surface Fermi level position of (NH₄)₂S_x-treated samples.