A new optical method for in situ monitoring of epitaxial growth is proposed and applied to the growth of GaAs by metalorganic chemical vapor deposition. The growth process is investigated using optical reflection while triethylgallium and arsine are alternately supplied to the growing surface. Linearly polarized 325-nm He-Cd laser light is irradiated at a 20° angle with respect to the (001)-oriented GaAs substrate surface. Laser light with a polarization E vector that is perpendicular to the substrate surface is more efficiently reflected during the triethylgallium flow period than during the arsine flow period due to the different optical absorption between Ga- and As-atomic surfaces. Therefore, we call this the “surface photo-absorption” (SPA) method. This method provides a means for real-time control and in situ study of epitaxial growth by metalorganic chemical vapor deposition. A strong and persistent oscillation in the reflection intensity is observed when triethylgallium and arsine are alternately supplied.
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