Spin-flip Raman scattering in InGaAs/GaAs quantum dots

Strong spin-flip Raman scattering (SFRS) from self-assembled n-doped InGaAs/GaAs quantum dots as well as from an undoped sample has been observed in external magnetic fields up to 10 T. In both cases the SFRS exhibits a strong dependence on the geometry of the experiment. The predominant Raman signal is attributed to a spin-flip of a resident electron induced by a photocreated exciton. The magnetic field dependencies of the electronic Raman shift, measured in Voigt- and tilted Faraday-geometry, demonstrate similar slopes (vertical stroke g vertical stroke eparallel ∼0.62 and vertical stroke g vertical stroke eperpendicularto ∼0.54), but tend to different Raman shifts at zero magnetic field. In tilted Faraday-geometry the Raman shift tends to δ=0.4 cm-1, it depends also on the optical excitation energy as well as on the annealing temperature of the samples. The offset at B=0 T can be related to excitonic exchange interaction and to additional nuclear magnetic fields acting on the resident electrons. At B=10 T the electronic spin-flip shift is larger in tilted Faraday- than in Voigt-geometry, which originates from an electron g factor anisotropy. The electron g factor dispersion has been measured across the emission band of the inhomogeneously broadened quantum dot ensemble.