Kinetics of native oxide film growth on epiready GaAs

The evolution of the native oxide layer on polished epiready GaAs wafers has been studied over a period of almost 2 years using grazing incidence X-ray reflectivity and surface photoabsorption. Using computer-simulated reflectivity profiles to fit the X-ray data, the thickness, density and effective roughness of the oxide layer was measured as a function of time. Surface photoabsorption measurements within a metal-organic vapour phase epitaxy reactor indicated that, after about 5 months, oxide species appeared that required higher temperatures to desorb. There was no difference in the oxide species present for wafers stored in air or in an inert atmosphere. The data suggest that the thickening occurs by reaction of the oxide with the bulk semiconductor material.