Raman scattering of & superlattices grown along the [012] direction

We report the observation of confined phonon modes in (GaAs${)}_{{\mathrm{n}}_1}$/(AlAs${)}_{{\mathrm{n}}_2}$ superlattices grown along the [012] direction. These modes have frequencies which map closely those of the optical phonons of bulk GaAs and AlAs. In near-resonance conditions we observe up to three overtones or combinations of GaAs (AlAs) confined and interface phonons [for a sample with parameters ($n_1$,$n_2$)=(21,25) monolayers] or as combinations of only interface modes [for ($n_1$,$n_2$)=(6,42) monolayers]. Lattice-dynamical calculations for these superlattices show good agreement with experimentally observed TO and LO confined and interface mode frequencies in the GaAs optical-phonon region.