Abstract
Angleβresolved xβray photoelectron spectroscopy (ARXPS) has been used to study the composition of oxides grown on γ110γ and γ100γ GaAs during exposure to UV/ozone. The effects of substrate treatments on oxide growth were compared on γ100γ surfaces exposed to an HF treatment and thermal desorption of the oxide and γ110γ surfaces prepared by in situ cleaving. Shortβterm (10 min) oxidation of γ110γ cleaved surfaces resulted in a mixture of Ga and As stoichiometric oxides, with arsenic depletion of the underlying GaAs substrate. Less arsenic depletion of the substrate occurs for acidβetched γ100γ GaAs oxidized under the same conditions. Extended UV/ozone oxidation (60 min) of these substrates yields oxide films that are less stoichiometric, with an arsenic oxide phase segregating nearer to the surface. Cleaved γ110γ substrates are again depleted in arsenic just below the interface. UV/ozone oxidation of γ100γ GaAs surfaces prepared by thermal desorption produced oxide films of uneven thickness, which yielded poor ARXPS profile results. The Laplace Transform model of Bussing and Holloway was modified to allow the use of different electron inelastic mean free path (Ξ») values for surface oxide and substrate. The range of values used to test the modified equation did not cause significant changes of the depth profile.