Effect of structural defects consisting of ternary mixed crystals on localized interface optical modes in superlattices

The localized interface optical-phonon modes lying in a minigap of AlAs-GaAs superlattice with structural defects consisting of ternary mixed-crystal AlxGa1-xAs are studied in the dielectric continuum approximation. We find that three localized interface optical modes appear in each frequency minigap for certain structural parameters. Two of them are antisymmetric with respect to the center of the defect layers and display interesting features significantly different from those in the structure with a binary crystal defect layer. However, the third mode with symmetric property shows similar behavior as that in the structure with a binary crystal defect layer.