Relaxation of Electron Spin during High-Field Transport in GaAs Bulk

A semiclassical Monte Carlo approach is adopted to study the multivalley spin depolarization of drifting electrons in a doped n-type GaAs bulk semiconductor, in a wide range of lattice temperature ($40<T_L<300$ K) and doping density ($10^{13}<n<10^{16}$cm$^{-3}$). The decay of the initial non-equilibrium spin polarization of the conduction electrons is investigated as a function of the amplitude of the driving static electric field, ranging between 0.1 and 6 kV/cm, by considering the spin dynamics of electrons in both the $\Gamma$ and the upper valleys of the semiconductor. Doping density considerably affects spin relaxation at low temperature and weak intensity of the driving electric field. At high values of the electric field, the strong spin-orbit coupling of electrons in the $L$-valleys significantly reduces the average spin polarization lifetime, but, unexpectedly, for field amplitudes greater than 2.5 kV/cm, the spin lifetime increases with the lattice temperature. Our numerical findings are validated by a good agreement with the available experimental results and with calculations recently obtained by a different theoretical approach.