Hot electron spin diffusion in n-type GaAs

We use two-color magneto-optical Kerr (MOKE) microscopy to study low-temperature electron spin diffusion in bulk n-type GaAs (n = 1.4 × 1016 cm−3). We show that simple drift-diffusion models do not describe the spin diffusion for above-bandgap optical spin injection correctly. By variation of the excitation energy and lattice temperature we demonstrate that this discrepancy is caused by the influence of the pump-induced local overheating of the electron system with respect to the lattice, which persists over length scales comparable to the spin diffusion length. Consideration of this hot carrier effect is crucial for a reliable extraction of spin propagation parameters from optical experiments.