Phonons in GaAs/AlAs superlattices grown along the [111] direction

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Abstract
We present Raman-scattering data for GaAs/AlAs superlattices grown on GaAs substrates along the [111] 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 have frequencies which map closely those of the parent materials in the [111] direction of k space. We also observe folded acoustic-phonon modes. The results of a lattice-dynamical calculation for these superlattices on the basis of the shell model are presented, with special emphasis on the angular dispersion of ‘‘interface’’ modes.