Calculated far-infrared lattice absorption spectra of cadmium telluride doped with beryllium

Abstract

The impurity-induced infrared lattice absorption has been calculated for a zinc-blende-type crystal in the low-concentration limit of substitutional impurities. The impurity is described by a nearest-neighbor perturbation model where along with the change in mass at the impurity site, the changes in the central and noncentral impurity-host crystal interactions have been considered. A numerical estimate has been made for impurity-induced infrared absorption in CdTe doped with Be impurities after employing a seven-parameter second-neighbor-ionic model. The main features of the experimentally observed absorption have been reasonably explained. The observed absorption peak at 61 ${\mathrm{cm}}^{-1\mathrm{}}$ is seen to be an impurity-activated one-phonon acoustic band rather than a resonant mode suggested earlier by Sennett et al.