Resonant Raman scattering in GaAs

We report measurements of resonant first- and second-order Raman scattering in GaAs with exciting photon energies covering the entire visible spectrum. Two sets of energy gaps were investigated: the three-dimensional E₀{E₀}+₀ and the two-dimensional E₁{E₁}+₁ critical points. The symmetry components of the second-order spectrum were separated and observed structures were interpreted by comparison with neutron scattering data. For a theoretical description of the Raman cross section we used either experimental values or a model description of the electric susceptibility. The resonance behavior could be explained for nearly all observed scattering processes with the exception of 2LO () and forbidden LO scattering by assuming for first order the electron-one-phonon and for second order the renormalized electron-two-phonon deformation potential coupling. Second-order deformation potentials are given as well as a comparison of the theoretically and experimentally determined ratios of the electron-one-phonon deformation potential near L to that near. Forbidden LO scattering is explained well by the Fr\"ohlich coupling mechanism, not only its resonance shape near E₀+₀ and near E₁ but also the ratio of its strength to that of TO scattering. 2LO () scattering is attributed to an iterated electron-one-phonon scattering process caused also by the Fr\"ohlich interaction.