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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. [ABSTRACT FROM AUTHOR]

We study the propagation of electron spin density polarization and spin currents in n-doped semiconductors within the two-component drift-diffusion model in an applied electric field (E). The drift and diffusion contributions to the spin currents are examined, which shows how the spin current could be enhanced. We find that there is a crossover field (Ex), where the drift and diffusion contribute equally to the spin current in the downstream direction. This suggests a possible way to identify whether the process for a given E would be in the drift or diffusion regime. We derive the expression for Ex and show that the intrinsic spin diffusion length in a semiconductor can be calculated directly from Ex. The results will be useful in obtaining transport properties of the carriers’ spin in semiconductors. This investigation, however, highlights the need for further experiments to be conducted to measure Ex in semiconductors. [ABSTRACT FROM AUTHOR]

The size and dependences of second-order optical effects in Cu-doped cadmium iodide nanocrystals are analyzed. The results are described by discussing photoinduced kinetics of the electron-phonon anharmonic interaction and nanosized quantum confined effect, the vital roles played in the observed effects.