Fine structure of the trion triplet state in a single self-assembled semiconductor quantum dot

The emission from the charged biexciton is used to monitor the energy structure of the trion triplet state in a negatively charged CdSe/ZnSe quantum dot. The isotropic part of the electron-hole exchange interaction regroups the otherwise sixfold degenerated state in three Kramers doublets. The energy separation between the radiative pairs with total spin projection F-z = +/-3/2 and +/-1/2 is 1.6 meV. The anisotropic part mixes states with DeltaF(z) = +/-2 resulting in a partly linearly polarized transition dipole. Application of magnetic field lifts the degeneracy of the Kramers doublets. The g factors also manifest the anisotropic state mixing. (C) 2002 American Institute of Physics.