Negative circular polarization of photoluminescence of large InP/(In,Ga)P quantum dots was studied subject to a magnitude and direction of a magnetic field. In a field tilted relative to the average optically oriented electron spin, a deviation of the dependences from the isotropic case is observed. Using spin-flip Raman scattering it was determined that the electron $g$ factor is isotropic $g_z=g_x=1.52\pm 0.05$, where $z$ is the structure growth axis. It is shown that the peculiarities of the behavior of optical orientation in a magnetic field are caused by the anisotropy of the electron spin relaxation time: the relaxation time of the spin component directed along the QD growth axis appears to be large relative to the relaxation time in the plane (${{\tau }_s}_z\gg {{\tau }_s}_x$). This case is not typical for an electron in QDs with the direct band gap in momentum space, since the dominant spin relaxation mechanism is usually due to the isotropic hyperfine interaction with the nuclear spins. The observed stabilization of the electron spin along the QDs growth axis is characteristic for the exciton-type spin dynamics determined by the isotropic electron-hole exchange interaction.

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• Spin blockade
• Spin dynamics
• Spintronics
• Quantum dots
• Photoluminescence