Fine structure of the exciton in a single asymmetric CdTe quantum dot

Zero-dimensional excitons localized in CdTe/ZnTe nanostructures have been s tudied by spatially resolved magnetophotoluminescence spectroscopy. At zero magnetic field, exciton transitions present a doublet structure linearly p olarized along two orthogonal directions. We attribute this doublet structu re to bright exciton states \ +/- 1 > split by the local asymmetry of the l ocalization potential. With increasing magnetic field oriented along the gr owth axis, a mixing of dark exciton states \ +/- 2 > and bright exciton sta tes is observed for localization sites that present a large zero-field spli tting. This allows a direct estimate of the electron and hole g-factors and of the isotropic exchange energy for strongly localized heavy-hole exciton s. (C) 2000 Elsevier Science B.V. All rights reserved.