COUPLED PHONON PHOTON EXCITATIONS IN SEMICONDUCTOR SUPERLATTICES

Coupled phonon-photon excitation field structure and dispersion in bin ary semiconductor superlattices are studied using a local theory with retardation. The material layers are characterized by the frequency-de pendent isotropic dielectric permittivities. Numerical calculations ha ve been carried out for GaAs/AlAs superlattices with the layer thickne ss ratio d(1)/d(2)<1 and d(1)/d(2)>1 in the case of in-plane propagati on of p-polarized electromagnetic waves. Seven main dispersion branche s and two series of additional ones related to confined modes are obta ined. The latter are found to exist just below the transverse optical phonon frequencies of constituent materials. The branches characterize d by different types of field symmetry are found to intersect in the a bsence of damping. The conditions of the crossing points existence are estimated.