STUDIES OF THE UV OZONE OXIDATION OF GAAS USING ANGLE-RESOLVED X-RAY PHOTOELECTRON-SPECTROSCOPY

Angle‐resolved x‐ray photoelectron spectroscopy (ARXPS) has been used to study the composition of oxides grown on 〈110〉 and 〈100〉 GaAs during exposure to UV/ozone. The effects of substrate treatments on oxide growth were compared on 〈100〉 surfaces exposed to an HF treatment and thermal desorption of the oxide and 〈110〉 surfaces prepared by in situ cleaving. Short‐term (10 min) oxidation of 〈110〉 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 acid‐etched 〈100〉 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 〈110〉 substrates are again depleted in arsenic just below the interface. UV/ozone oxidation of 〈100〉 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 (λ) 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. Copyright © 1990 John Wiley & Sons Ltd.