Resonant Raman scattering of submono-layer CdSe/ZnSe superlattices

We present Raman scattering and photoluminescence study at different temperatures of CdSe/ZnSe superlattices with mono- and submono-layer depositions of CdSe. On the basis of transmission electron microscopy and optical studies it is currently believed that such depositions lead to formation of flat CdZnSe islands with 10-100 nm lateral dimensions. At room temperatures we have observed only a strong resonance Raman scattering by LO-phonon of barrier ZnSe. At temperature about 20 K resonance Raman spectra showed a broad structured phonon peak that could be deconvoluted into a narrow peak attributed to the barrier LO-phonon of ZnSe and a broad peak at lower frequencies, which gained intensity as the excitation energy was tuned closer to the localized exciton transition. Therefore, we attribute this latter peak to averaged scattering of LO-phonons in the CdxZn1-xSe islands with different Cd composition. The average concentration of Cd was estimated as x = 0.2. Our Raman data confirm exciton localization in the islands at low temperatures. Folded acoustic phonons of the superlattices were observed. (C) 2000 Elsevier Science B.V. All rights reserved.