PHONON-DISPERSION IN MULTICOMPONENT SUPERLATTICES

The phonon spectra of a three-component semiconductor superlattice (SSL) with GaAs, GaSb, AlAs as components along the growth direction are studied by using a one-dimensional transfer matrix method where one of the components, GaSb, is lattice mismatched with the other two, for various thicknesses. The eigen-displacements are plotted for various frequencies and thicknesses keeping the thickness of the GaSb layer constant. Also, the frequencies of the confined LO modes of AlAs and GaSb are plotted as functions of the effective wave vector for various thicknesses of the constituting components forming the SSL and compared with the bulk dispersion curves. It is observed that the phonon dispersion in a multicomponent SSL is similar to that of a two-component SSL, but the large magnitude of lattice parameters of GaSb and its small thickness qualitatively change the superlattice dispersion relation, a feature not reported so far.