Spin transport in semiconductors in the degenerate (DG) and diffusion regimes is investigated. We analyze semiconductor DG and nondegenerate regimes and study optically polarized spin transport in GaAs under a weak bias. The results obtained in the spin transport experiments show that the effect resulting from the spin current in GaAs increases in the DG regime, in consistence with the theoretical investigation based on the generalized Einstein relation. The effect is found to be increased with decreasing temperature or increasing doping density. The results are also discussed based on a spin drift-diffusion model. 頲008 American Institute of Physics.