PHONONS IN MULTILAYERED STRUCTURES .3. A POLARIZATION EFFECT

We have used a modified version of the layer method and a microscopic valence force field model (VFFM) including polarization fields to calc ulate both bulk and localized phonon modes for a planar interface. Pol arization effects have been taken into account by a perturbative techn ique, which includes both the short-range interactions (up to second n earest neighbours) between atoms as well as the long-range Coulomb for ces due to atomic ionicity. We consider both InAs/GaSb and GaAs/AlAs l ayered systems. Dispersion curves along the symmetry directions are ca lculated, indicating that the interface modes are highly localized and the polarization field has an effect on the localized states. Our res ults agree reasonably well with recent Raman measurements.