MULTIPLE-ORDER RAMAN-SCATTERING AND THE DENSITY OF VIBRATIONAL-STATES IN ALPHA-GAAS

Raman scattering in amorphous GaAs is interpreted in the framework of a model taking into account multiple-order processes. This model describes, first, the background signal, which systematically underlies the first-order bands, and second, the temperature dependence of both Stokes and anti-Stokes Raman spectra. The coupling between the light and the vibrational modes is shown to be dependent on the extended or localized character of the implied modes. As a consequence of this analysis, a different method of achieving experimentally the density of vibrational states of amorphous systems is proposed. In GaAs, the data show remarkable agreement with theoretical calculations.