Low-temperature electron-spin relaxation is studied by the optical orientation method in bulk n-GaAs with donor concentrations from 10 14 cm Ϫ3 to 5ϫ10 17 cm Ϫ3 . A peculiarity related to the metal-to-insulator transition is observed in the dependence of the spin lifetime on doping near n D ϭ2ϫ10 16 cm Ϫ3 . In the metallic phase, spin relaxation is governed by the Dyakonov-Perel mechanism, while in the insulator phase it is due to anisotropic exchange interaction and hyperfine interaction
We report on the optical manipulation of the electron spin relaxation time in a GaAs-based heterostructure. Experimental and theoretical study shows that the average electron spin relaxes through hyperfine interaction with the lattice nuclei, and that the rate can be controlled by electron-electron interactions. This time has been changed from 300 ns down to 5 ns by variation of the laser frequency. This modification originates in the optically induced depletion of an n-GaAs layer.
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