Localized interface optical phonon modes in a semi-infinite superlattice with a cap layer

We investigate the existence and characteristics of the localized interface optical phonon modes (IOPMs) in a semi-infinite AlAs-GaAs superlattice with a cap layer consisting of ternary mixed crystal AlxGa1-xAs in the dielectric continuum approximation. We find that the introduction of two-mode behaviour of the ternary mixed crystal of the cap layer or the semi-infinite uniform dielectric medium leads to rich and varied localized mode spectra with interesting features. Moreover, it is also found that the localized IOPMs are sensitive to the concentration x, the thickness of the cap layer and the type of semi-infinite uniform dielectric medium. A brief analysis of these results is given. It is expected that the localized IOPMs can be artificially controlled by adjusting the parameters of the proposed micro-structures.