Fine structure of biexciton emission in symmetric and asymmetric CdSe/ZnSesingle quantum dots

The influence of quantum dot (QD) asymmetry on the emission of single three -dimensionally confined biexcitons in II-VI semiconductor nanostructures ha s been studied by magnetophotoluminescence spectroscopy. Investigating both the biexciton and the single-exciton transition in the same single QD, we obtain a unified picture of the impact of electron-hole exchange interactio n on the fine structure and the polarization properties of optical transiti ons in QDs. The exchange splitting is demonstrated to have a strong influen ce on the derivation of the biexciton binding energy, which we determine to be about 17 meV, much less than the separation between exciton and biexcit on lines (approximate to 24 meV) in the spectra.