Resonant Raman scattering in GaAs

Abstract

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 $\frac{{E}_{0}}{{E}_{0}}+{\ensuremath{\Delta}}_{0}$ and the two-dimensional $\frac{{E}_{1}}{{E}_{1}}+{\ensuremath{\Delta}}_{1}$ 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 $2\mathrm{LO}(\ensuremath{\Gamma})$ 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 $\ensuremath{\Gamma}$. Forbidden LO scattering is explained well by the Fr\"ohlich coupling mechanism, not only its resonance shape near ${E}_{0}+{\ensuremath{\Delta}}_{0}$ and near ${E}_{1}$ but also the ratio of its strength to that of TO scattering. $2\mathrm{LO}(\ensuremath{\Gamma})$ scattering is attributed to an iterated electron-one-phonon scattering process caused also by the Fr\"ohlich interaction.