Strong variation of the exciton g factors in self-assembled ${\mathrm{In}}_{0.60}{\mathrm{Ga}}_{0.40}\mathrm{As}$ quantum dots

The magnetic-field dependence of energy and polarization of the low excitation photoluminescence from self-assembled ${\mathrm{In}}_{0.60}{\mathrm{Ga}}_{0.40}\mathrm{As}$ quantum dots has been studied by single dot spectroscopy. For the spin splitting of the emission lines at 8 T three different characteristic values, $-1.5$ meV, $-0.3$ meV, and $+0.3\mathrm{}$ meV are observed. For dots with small spin splittings, no indication for ground shell biexciton emission can be found, in contrast to dots with a large splitting. These findings suggest that the emission in the dots with a weak Zeeman interaction originates from charged excitons whose formation becomes possible from dopants in the nearest surrounding of the dot structures. The presence of these dopants modifies the electronic band structure and thus also the g factors of the carriers.