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

The macroscopic dielectric function of a superlattice is used to describe 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 tensor derived from a linear chain model that can take account of the effects of interface roughness. The method gives a unified description of interface 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 measurements.