EFFECTS OF ION-BOMBARDMENT ON THE CHEMICAL-REACTIVITY OF GAAS(100) - VARIATION OF BOMBARDING ION MASS

The effect of the mass of the bombarding ion on the chemical reactivity of ion-bombarded GaAs(100) was investigated by X-ray photoelectron spectroscopy. Chemically cleaned (1:1 HCl(conc)/H2O) GaAs was ion bombarded with 3-keV 3He+, Ne+, Ar+, and Xe+ at a constant fluence (1017 ions/cm2) and subsequently exposed to O2 in the range 107–1011 langmuirs and H2O at 1013 langmuirs. Ion-bombarded GaAs exposed to O2 yields Ga2O3, As2O3, and As2O5, with Ga2O3 being the major component. Exposure of ion-bombarded GaAs to H2O yields GaO(OH) and Ga(OH)3. Ion-bombarded GaAs shows an increased chemical reactivity compared to that of chemically cleaned GaAs, and the enhancement in reactivity was shown to be directly related to the mass of the bombarding ion. Upon exposure to either O2 or H2O, GaAs ion bombarded with 3-keV Xe+ ions exhibited the greatest chemical reactivity, which suggests that defects caused by ion bombardment are concentrated at the surface and play a role in the enhanced chemical reactivity. The damage caused by ion bombardment was also investigated by optical reflectivity in the visible and near-ultraviolet region, by Raman spectroscopy and by current-voltage and capacitance-voltage measurements. Ion bombardment forms a structurally damaged near-surface layer. The depth of damage is inversely related to the mass of the bombarding ion. X-ray photoelectron spectroscopy detected crystal damage in the form of As depletion that extends through the first 60 Å of the GaAs crystal in all cases, with the magnitude of As depletion increasing with increasing ion-bombardment mass. Bombardment of GaAs with 3-keV Xe+ ions produces a greater defect density at the surface, leading to increased chemical reactivity. © 1990, American Chemical Society. All rights reserved.