Size dependence of the exciton g-factor in self-assembled CdTe/ZnTe quantum dots

We study exciton spin splitting of single quantum dots in a highly inhomogeneous self-assembled CdTe/ZnTe quantum dot sample. By spatial imaging of individual dots in applied magnetic field (using a solid immersion lens) and by analyzing the circular polarization of the PL emissions, we measure both the spin splitting and the diamagnetic shift of zero-dimensional excitons. We determine that the absolute value of exciton g-factor decreases from 4 to about 2 as the emission energy decreases from 2.35 eV to 1.85 eV. At the same time, we observe an increase of the diamagnetic shift up to 100 $\mu $eV. Such small values indicate strong spatial confinement of the excitons, as the diamagnetic shift corresponding to the bulk Bohr radius ($\sim $10nm) which equal 600 $\mu $eV. From the diamagnetic shift we estimate that the diameter of CdTe quantum dots ranges from 1nm to 6nm. These results imply that the g-factor and thus the spin splitting of a quantum dot exciton is strongly enhanced for quantum dots with smaller size of the confining potentials. The work was supported by NSF grants nr 9975655 and 0071797 and PBZ-KBN-044/P03/2001.