Spectral Dependence of Optical Reflection during Flow-Rate Modulation Epitaxy of GaAs by the Surface Photo-Absorption Method

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Abstract
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 incident light at the Brewster angle. This configuration minimizes the bulk GaAs contribution in light reflection. The small reflection light intensity change in the growing process is thus detected with a high signal-to-noise ratio. The spectral dependence of the SPA signal during flow-rate modulation epitaxy of GaAs was found to be composed of anisotropic and isotropic wavelength regions which correspond to the absorption spectra of surface chemical species. These spectra can be ascribed to the optical absorption of the chemical bond between surface Ga (or As) atom and underlying As (or Ga) plane with anisotropy and the optical absorption of the chemical bond related to the surface Ga atom, which is perpendicular to the (001) surface.