The spin diffusion/transport in n-type (001) GaAs quantum well at high
temperatures (≥120 K) is studied by setting up and numerically solving the
kinetic spin Bloch equations together with the Poisson equation
self-consistently. All the scattering, especially the electron-electron Coulomb
scattering, is explicitly included and solved in the theory. This enables us to
study the system far away from the equilibrium, such as the hot-electron effect
induced by the external electric field parallel to the quantum well. We find
that the spin polarization/coherence oscillates along the transport direction
even when there is no external magnetic field. We show that when the scattering
is strong enough, electron spins with different momentums oscillate in the same
phase which leads to equal transversal spin injection length and ensemble
transversal injection length. It is also shown that the intrinsic scattering is
already strong enough for such a phenomena. The oscillation period is almost
independent on the external electric field which is in agreement with the
latest experiment in bulk system at very low temperature [Europhys. Lett. {\bf
75}, 597 (2006)]. The spin relaxation/dephasing along the diffusion/transport
can be well understood by the inhomogeneous broadening, which is caused by the
momentum-dependent diffusion and the spin-orbit coupling, and the scattering.
The scattering, temperature, quantum well width and external magnetic/electric
field dependence of the spin diffusion is studied in detail.Comment: 12 pages, 6 figures, to be published in J Appl. Phy