Resonant Raman scattering from confined phonons and interface phonons in a GaAs/GaAlAs superlattice

Abstract
The authors have studied the optic phonons of a GaAs/GaAlAs superlattice (dGaAs=55 AA, dGaAlAs=175 AA) using resonance Raman spectroscopy. Resonance was obtained with the n=2 electron-heavy-hole exciton of the GaAs quantum well, and with a bound exciton of the GaAlAs layers. Several optical modes have been observed that are confined to the GaAs layers, whose energies agree well with neutron scattering measurements of bulk GaAs phonon dispersion. In this sample there is no clear evidence for modes confined to the GaAlAs layers. The authors have also observed, in the region of the AlAs-like modes of the GaAlAs layers, an additional broad band intermediate in energy between the LO and TO modes. This scattering is found to be resonant with both the GaAs and GaAlAs electronic states, and its shape is consistent with model predictions for interface phonons.