Manifestation of interaction effects in Raman spectra of CdTe quantum-dot layers with ZnTe narrow barriers

Abstract

The Raman spectra of superlattices consisting of layers of CdTe self-assembled quantum dots separated by ZnTe narrow barriers with thicknesses of 10 and 5 monolayers are investigated. It is found that, apart from the bands previously observed at frequencies of ∼120 and ∼140 cm−1 for samples with thicker barriers (25 and 12 monolayers), the Raman spectra exhibit a band at ∼147 cm−1 in the frequency range of CdTe vibrational modes. This band is attributed to a symmetric vibrational mode of a pair of quantum dots with oppositely directed oscillations of the dipole moments. It is this type of vibrational mode in the material surrounding the ZnTe quantum dot that accounts for the shift of the band at ∼200 cm−1 near the LO mode of ZnTe vibrations toward lower frequencies.