Electron and HolegFactors and Exchange Interaction from Studies of the Exciton Fine Structure inIn0.60Ga0.40AsQuantum Dots

Self-assembled ${\mathrm{In}}_{0.60}{\mathrm{Ga}}_{0.40}\mathrm{As}$ quantum dots (QD's) have been studied by single dot magnetophotoluminescence spectroscopy ( $B\le 8\mathrm{T}$). At $B=0\mathrm{}$ a splitting of the exciton ( $X$) emission is observed which we ascribe to an asymmetry of the confinement potential. With increasing $B$ the emission splits into a quadruplet corresponding to the $m=\pm 2$ and $\pm 1X$ states, which originates from a reduction of the cubic symmetry of the QD's. From the spectroscopic data we obtain values for the electron ( $e$) and hole ( $h$) $g$ factors. We also determine the $X$ singlet-triplet splitting which is found to be enhanced over bulk values by about an order of magnitude due to the increase of the $e-h$ overlap in the QD's.