Electron and hole g factors and exchange interaction from studies of the exciton fine structure in In0.60Ga0.40As quantum dots

Self-assembled In0.60Ga0.40As quantum dots (QD's) have been studied by sing le dot magnetophotoluminescence spectroscopy (B less than or equal to 8 T). At B = 0 a splitting of the exciton (X) emission is observed which we ascr ibe to an asymmetry of the confinement potential. With increasing B the emi ssion splits into a quadruplet corresponding to the m = +/-2 and +/-1 X sta tes, which originates from a reduction of the cubic symmetry of the QD's. F rom 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 fo und to be enhanced over bulk values by about an order of magnitude due to t he increase of the e-h overlap in the QD's.