A complete characterization of the GaAs surface treated with (NH4)(2)S-x solution is investigated in order to explain the bandedge photoluminescence improvement of the GaAs surface observed after sulfur treatment. Photoluminescence, surface-state density, and surface chemistry of the (NH4)(2)S-x-treated GaAs surface are analyzed and compared with results from the literature. It is shown that the photoluminescence intensity is not directly controlled by surface-state density at midgap but seems to be correlated with the formation of sulfur bonds such as As-S and Ga-S, which are believed to create surface traps in the bandgap located near the valence band maximum and which appear to control band bending near the surface. To the authors’ knowledge, this is the first experimental proof of such implication of the Ga-S and As-S bonds in the improvement of the GaAs surface electrical quality.