INTERACTION OF ATOMIC-HYDROGEN WITH NATIVE OXIDES ON GAAS(100)

GaAs (100) covered with its native oxides is exposed to increasing doses of low energy atomic hydrogen in order to test the possibility of using it for surface cleaning at moderate temperatures. Hydrogen molecules are dissociated using a hot filament, and samples are exposed to atomic hydrogen at room temperature and at 300-degrees-C with doses between 100 L and 100 kL of H-2. The chemical modifications are characterized by ultraviolet and x-ray photoelectron spectroscopies. Exposures to atomic hydrogen contribute to clean the surfaces at both temperatures. At room temperature, As oxides completely desorb below 30 kL. The substrate is not degraded but one monolayer (ML) of C and Ga oxides remain on the surface upon hydrogenation up to 100 kL. Heating the sample to 300-degrees-C stimulates the reaction of As oxides with the substrate and the desorption of reaction products to a larger extent. Above 10 kL, the thickness of the remaining contaminating layer is inferior to 1 ML. After exposures above 5 kL, superficial As depletion is observed in the substrate before complete cleaning is achieved, however no traces of metallic Ga are detected.