CHEMICAL-SHIFT IN OPTICAL REFLECTION SPECTRA OBSERVED DURING III-V-SEMICONDUCTOR METALORGANIC CHEMICAL VAPOR-DEPOSITION GROWTH BY SURFACE PHOTOABSORPTION METHOD

Spectral dependence of optical reflection from a growing surface is measured in situ during metalorganic chemical vapor deposition of As-based III-V semiconductors, InAs, GaAs, AlAs and AlGaAs by surface photo-absorption method. When one monolayer of group III atom is deposited on an As-stabilized surface, the spectral dependence of reflectivity change shows a chemical shift in the visible light region. The spectrum is red-shifted in the order of AlAs, AlGaAs, GaAs and InAs. The photon energy when the spectrum curve is rising correlates well with the heat of formation in group III atom-As tetrahedral bond, and is almost independent of the underlying layer composition. This result supports the assumption that the observed reflectivity difference between group III atom surface and As-stabilized surface in the visible light region is mainly caused by the photo-absorption process of the surface III-As chemical bond.