INTERFACE AND CONFINED OPTIC PHONON MODES FOR SUPERLATTICES IN THE LONG-WAVELENGTH LIMIT

The macroscopic dielectric function of a superlattice is used to descr ibe the angular dependence of the superlattice's confined phonons and their associated polaritons at long wavelengths. Results are shown for short-period GaAs/AlAs superlattices making use of a dielectric tenso r derived from a linear chain model that can take account of the effec ts of interface roughness. The method gives a unified description of i nterface and confined optic phonon modes in the long-wavelength limit, and provides precise information about the angular dependence of mode frequencies that are accessible to micro-Raman and far infrared measu rements.