PHONON-DISPERSION IN QUASI-PERIODIC SEMICONDUCTOR SUPERLATTICES

The phonon spectra of unstrained and strained quasiperiodic semiconduc tor superlattices (QSSL) have been calculated using one-dimensional li near chain model. We consider two types of quasiperiodic systems, name ly canter triadic bar (CTB) and Fibonacci sequences (FS), constituting of AlAs, GaAs and GaSb of which the latter two have a lattice mismatc h of about 7%. The calculations have been made using transfer matrix m ethod and also with and without the inclusion of strain. We present th e results on phonon spectra of two component CTB and two as well as th ree component FS semiconductor superlattices (SSL), thickness and orde r dependence on LO mode of GaAs, effect of strain on LO frequency of G aAs. The calculated results show that the strain generated due to latt ice mismatch reduces significantly the magnitudes of the confined opti cal phonon frequency of GaAs.