X-RAY PHOTOELECTRON AND AUGER-ELECTRON SPECTROSCOPY STUDY OF ULTRAVIOLET OZONE OXIDIZED, P2S5(NH4)2S TREATED GAAS(100) SURFACES

In this report we discuss the results of a study undertaken to investigate the composition and thermal stability of ultraviolet/ozone oxidized, P2S5/(NH4)2S treated GaAs(100) surfaces. In particular, we have used x-ray photoelectron spectroscopy and Auger electron spectroscopy to probe the oxide and interface at room temperature and as a function of annealing temperature. The room temperature data indicate that S is buried between the oxide overlayer and the GaAs substrate. This oxide contains a variety of As and Ga bonding configurations which, after moderate annealing, are transformed into thermally more stable phases, such as As2O3 and Ga2O3. Complete desorption of the oxide occurs after annealing at 600-degrees-C. Annealing the as-oxidized surface to high temperatures also has a profound effect on the S. Heating the sample to 495-degrees-C causes some S to diffuse towards the oxide surface, while annealing at higher temperatures leads to S diffusion into the GaAs substrate. Even after complete desorption of the O, a small amount of S remains embedded in the GaAs lattice.