A real GaAs surface is covered with a relatively thick layer (~nm) of native oxide responsi- ble for the surface Fermi level pinning within the band gap of the semiconductor. The method presented in this work is the sulphur passivation by treating the semiconductor in sulphide solutions that combines both chemical and electronic passivation by reducing the surface state density (e.g., pure ammonium sulphide and sulphur monochloride). The passivated surface was examined by SEM, EDS and XPS techniques, that put into evidence the existence of an adherent layer of sulphur compound as a result of chemical interaction of sulphur ions with n-GaAs surface.