Characterization of GaAs-(001) Surface Photo-Oxide Formed by Visible-Light Irradiation

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Abstract
The effects of visible-light irradiation (70-280 mW/cm2) on oxidation of a GaAs (001) surface under an oxygen atmosphere (3.6×101 and 8.6×104 Pa) were investigated by temperature programmed desorption and X-ray photoelectron spectroscopy (XPS). XPS showed that irradiation at an intensity of 140 mW/cm2 increased the amount of surface oxygen by about 15% over dark oxidation of the corresponding oxygen exposure. Under 540°C isothermal conditions, the oxide desorption rate was initially low, but reached its maximum level with a time delay, showing the existence of expanding voids in the oxide layer during desorption. Light irradiation, as well as higher oxygen exposure, decreased the initial desorption rate, and increased the time delay by up to 6.4 min. This is interpreted as indicating that irradiation reduces the density of the weak parts in the oxide layer through an increase in the oxide thickness.