The reflectance spectra ofnhyphen;type GaAs samples with carrier densities from 3times;1016to 3times;1018cmminus;3have been measured in the spectral range 55ndash;1000 cmminus;1. Except for slight discrepancies in the vicinity of the reflectance minima, the classical Drude model provides an excellent description of the freehyphen;carrier effects in the reflectance. The discrepancies may be accounted for by a depletion layer at the surface or by a quantumhyphen;mechanical scattering theory. Inhomogeneities in the carrier density are measured by scanning the surface of the sample with a small aperture at a fixed frequency. The effect of mechanical polishing on the reflectance is analyzed in terms of a damaged layer. Reflectance measurements are also used to characterize samples consisting of epitaxial films of GaAs on GaAs substrates.
展开▼
