Phonon properties of GaAs/AlAs superlattice grown along the [110] direction

We report Raman scattering studies of GaAs/AlAs superlattices grown along the [110] direction. The appearance of distinct x-ray satellite peaks around the Bragg reflections demonstrates the formation of highly ordered periodic superlattice structures. The confined-optical-phonon modes corresponding to the three optical bulk branches as well as the folded-acoustic-phonon modes are observed. The confined modes have frequencies which map closely onto those of the optical phonons of the parent materials in the [110] direction ({Γ}--K--X) of k space. We also observe resonant Raman scattering by confined-optical and in-plane (interfacelike) vibrational overtones and their combinations. The results of a lattice-dynamical calculation for this superlattice is also presented with special emphasis on angular dispersion and the mixed polarization of superlattice modes.