In p+ GaAs thin films, under excitation by a tightly-focused laser, the spatial profile of the spin polarization is monitored as a function of excitation power. It is found that photoelectron diffusion depends on spin, as a direct consequence of the Pauli principle which causes a concentration dependence of the spin stiffness. Thermoelectric currents are also predicted to depend on spin under degeneracy (spin Soret currents), but these currents play a relatively small role in this case. The spin dependence of the mobility is also found weak. Conversely, ambipolar coupling with holes increases the steady-state photo-electron density at the place of excitation and therefore the amplitude of the degeneracy-induced polarization decrease at the place of excitation.
Degeneracy of a photoelectron gas is shown to strongly affect spin polarized electron transport since the Pauli
principle dictates a concentration dependence of the spin stiffness and of the mobility. This causes a spin
dependence of the diffusion constant D. A spin-dependence of D as large as 50 % is measured using polarized
microluminescence imaging in p+ GaAs thin films, revealing a novel spin filter effect. The charge diffusion
constant also depends on spin via a second order effect.
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