X-ray photoelectron spectroscopy with argon ion depth profiling was employed to investigate sulfur deposition from a standard 3H(2)SO(4):H2O2:H2O etchant onto (100) GaAs. From these experiments it appears that etching with 3H(2)SO(4):H2O2:H2O leaves a mixed sulfide/oxide layer, with free sulfur at the top surface of this layer. The sulfide within the layer was found to be bound to gallium, and recognition of the presence of sulfur allowed the clarification of the Ga(3d) photoelectron peak position for Ga2O3. No evidence of sulfate formation was found. Removal of the sulfur contamination using a solution of HCl:H2O was investigated. Also, atmospheric contamination of samples exposed to room conditions for six months was observed.