Low-energy oscillations in the E-0 photoreflectance spectra of homoepitaxial n-GaAs/n(+)-GaAs Samples with n=10(15)-10(16) cm(-3) and n+ approximate to 10(18) cm(-3)

The nature of the long-wavelength region of the E-0 photoreflectance spectr a is studied in n-GaAs/n(+)-GaAs homoepitaxial samples with n = 10(15)-10(1 6) cm(-3), n(+) approximate to 10(18) cm(-3), and the epitaxial film width d = 1-5 mum. The analysis of the published data, the quantitative analysis of experimental spectra, and our own experiments based on a novel technique , lead us to the conclusion that the low-energy oscillations originate in t he electromodulation mechanism that takes place in the region of the film-s ubstrate interface. The periodic modulation of the electric field near the film-substrate interface is induced by the isotropic diffusion of nonequili brium minority carriers that are created in the neutral volume of epitaxial films under the action of laser excitation. The characteristic time consta nts of various photoreflectance components are estimated by combining the q uantitative analysis of spectral line shapes with the analysis of experimen tal phase diagrams. (C) 2000 MAIK "Nauka/Interperiodica".