Spin and exchange effects in CdSe/ZnSe quantum dots probed by single-dot spectroscopy

The influence of exchange interaction on the eigenstate symmetry in a varie ty o CdSe/ZnSe single quantum dots is studied by photoluminescence spectros copy. The lifting of spin degeneracy of the optically allowed exciton state s results in a linearly polarized doublet of both the single exciton and th e biexciton transitions, with an energy splitting reflecting: the symmetry of the dots. Comparing different single dots, we found that most of the dot s are almost symmetric, i.e. have an energy splitting < 0.2 meV, while stro ngly asymmetric dots (i.e. a symmetry lower than D-2d) with energy splittin gs up to about 1 meV are predominantly oriented along the [1 1 0]1 acid [1 (1) over bar 0] axes of the crystal. (C) 2000 Elsevier Science B.V. All rig hts reserved.