Surface photo-absorption (SPA) is a newly developed in-situ optical monitoring technique for the epitaxial growth process. This method is based on the reflectivity measurement of p-polarized light incident at the Brewster angle. This configuration minimizes the bulk GaAs contribution to the total light reflection. The small change in reflected light intensity between Ga and As atomic surfaces during GaAs growth is thus detected with a high signal-to-noise ratio. By using this characteristic, GaAs growth rate can be monitored in-situ on an atomic scale. In addition to the in-situ monitoring of growth rate, the decomposition processes of Ga and As precursors in MOVPE can be studied by SPA. We demonstrate an investigation of the decomposition process of Ga organometallic, and discuss the growth mechanism of atomic layer epitaxy.
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