Far-infrared analysis of lattice vibrations in ZnSe/ZnCdSe superlattices

The results of the first measurements of far-infrared lattice reflection spectra of ZnSe/ZnCdSe superlattices grown on a GaAs substrate by molecular-beam epitaxy are presented. It is shown by a dispersion analysis of the experimental spectra measured at temperatures 300 and 10 K that, in the superlattices under study, instead of two TO modes corresponding to two different layers ZnSe and ZnCdSe of the superlattice only one TO mode is observed which has a frequency between the frequencies of the two layers. The existence of a single transverse mode in the lattice reflectivity spectrum of the ZnSe/ZnCdSe superlattice has been explained by a convergence of the vibrational modes under the effect of internal elastic strains.