We study the effect of the impurity density on lifetimes and relaxationlengths of electron spins in the presence of a static electric field in an-type GaAs bulk. The transport of electrons and the spin dynamics aresimulated by using a semiclassical Monte Carlo approach, which takes intoaccount the intravalley scattering mechanisms of warm electrons in thesemiconductor material. Spin relaxation is considered through theD'yakonov-Perel mechanism, which is the dominant mechanism in III-Vsemiconductors. The evolution of spin polarization is analyzed by computing thelifetimes and depolarization lengths as a function of the doping density in therange 10^{13} - 10^{16} cm^{-3}, for different values of the amplitude of thestatic electric field (0.1 - 1.0 kV/cm). We find an increase of the electronspin lifetime as a function of the doping density, more evident for latticetemperatures lower than 150 K. Moreover, at very low intensities of the drivingfield, the spin depolarization length shows a nonmonotonic behaviour with thedensity. At the room temperature, the spin lifetimes and depolarization lengthsare nearly independent on the doping density. The underlying physics isanalyzed.
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