Lattice strain and lattice dynamics of ZnSe-ZnTe strained-layer superlattices

Lattice strain and lattice dynamics of ZnSe-ZnTe strained-layer superlattices (SLSs) were examined by means of transmission electron microscopy and Raman scattering. Superlattice structures were confirmed from both transmission electron diffraction patterns and bright field images of the samples. Lattice distortions which originated from misfit strains were observed by the lattice image mode. The crystallinity of the adjacent layers was degraded when the layer thickness became large and polycrystalline structures were observed when the layer thickness exceeded the critical layer thickness. Raman scattering was used to assess the magnitude of the strain in the SLSs. Optical phonon frequencies of the components in SLSs were different from those frequencies of the bulk materials. The frequency shifts were used to quantify the strains in the SLSs. The observed shifts corresponded to the calculated values.