FOLDED ACOUSTIC PHONONS IN GAAS ALAS SUPERLATTICES GROWN ON NON-(100)-ORIENTED SURFACES/

We present Raman spectra for folded acoustic phonons in GaAs/AlAs supe rlattices grown along the [111], [211] and [311] direction. The symmet ry of these directions offer the possibility of observing transverse a nd longitudinal polarized folded acoustic phonons. The observed double ts of folded acoustic phonons are in accordance with the predicted sel ection rules, their frequencies and strengths are in agreement with ca lculations based on the continuum model. In the case of the (311)-orie nted sample, folded-phonon to Brillouin ratios are calculated using el asto-optic constants of GaP in lieu of AlAs.