Folded acoustic phonons in GaAs/AlAs superlattices grown on non(100-oriented surfaces

Abstract We present Raman spectra for folded acoustic phonons in GaAs/AlAs superlattices grown along the [111], [211] and [311] direction. The symmetry of these directions offer the possibility of observing transverse and longitudinal polarized folded acoustic phonons. The observed doublets of folded acoustic phonons are in accordance with the predicted selection rules, their frequencies and strengths are in agreement with calculations based on the continuum model. In the case of the (311)-oriented sample, folded-phonon to Brillouin ratios are calculated using elasto-optic constants of GaP in lieu of AlAs.