REACTION OF OXYGEN WITH INSITU H2S-TREATED GAAS (001) SURFACES

The reaction of oxygen with H2S-treated GaAs (001) surfaces was studied using Auger electron spectroscopy and reflection high-energy electron diffraction. GaAs surfaces in situ treated with H2S gas were exposed to pure oxygen gas with and without simultaneous light illumination of a halogen lamp. It was shown that the oxygen uptake on a H2S-treated surface is much less than that on an untreated bare GaAs surface. Surfaces exposed to oxygen were heated in an ultrahigh-vacuum environment in order to study the desorption of the reacted oxygen. The oxygen Auger signal was found to easily disappear when the surface was heated to 520-degrees-C, leaving sulfur atoms on the surface. The oxide formed on a bare GaAs surface with light illumination was found to be relatively thick; it did not desorb completely until it was heated to about 550-degrees-C. These results indicate that oxide on a H2S-treated surface is formed only on the top surface.