Abstract: The electronic properties of GaAa are dramatically improved in samples treated with aqueous solntion of sodinm sulfide nonahydrate (Na₂S·9H₂O).Experimental results show that the characteristic curves of capacitance-voltage (C-V) vary shape for the Na₂S·9H₂O treated samples, and that its potential barrier capacitance is higher than that of the untreated sample. The X-ray phtoelectron spectroscopy (XPS) reveals that the oxygen on the GaAs surface treated with Na₂S·9H₂O is remarkably removed, and that the peak of the binding energy of As varies from the background peak 1321.00 eV to 1321.47 eV, a shift of 0.47 ey. The sulfur depth profile on the GaAs surface is determined by the secondary ion masss pectroscopy (SIMS). New S-As bonds and compound of arsenic sulfide are formed on the GaAs surface, making the "pinned" Fermi level improved. The surface state density and surface recombination center on the sodium salfide treatment sample have been greatly reduced, which is favorable for controlling the charge in GaAs.

Key words: SIMS, aqueous solution of sodium sulfide nonahydrate, XPS