SELECTION-RULES AND DISPERSION OF GAAS/ALAS MULTIPLE-QUANTUM-WELL OPTICAL PHONONS STUDIED BY RAMAN-SCATTERING IN RIGHT-ANGLE, FORWARD, AND BACKSCATTERING INPLANE GEOMETRIES

We present a detailed experimental study of optical phonon Raman scattering in GaAs/AlAs multiple quantum wells for several in-plane geometries. By exploiting a waveguided structure, we performed 90°, forward, and backscattering experiments with dispersed light propagating along the layers. Using these geometries, phonons with various propagation directions and polarized both parallel and perpendicular to the growth axis can be probed. The 90°data complete and correct earlier results obtained for the same geometry by Zucker et al., bringing them into accord with later experimental and theoretical work. Moreover, in-plane forward scattering data are reportd as a complementary check to these experiments. We discuss selection rules and scattering mechanisms, and compare the results with phonon energies calculated within a continuum model based on linear combinations of LO, TO, and interface modes. We find a very good agreement between the experiment and the predictions of the established theory of phonon modes and Raman scattering in semiconductor heterostructures. © 1995 The American Physical Society.