Abstract
Abstract This thesis presents a theoretical study and numerical simulation of spin transport in a quasi 1D semiconductor system. The main purpose of this thesis is to achieve a spin filtering device to generate spin polarization. Specifically, we investigate the spin transport under the effects of both the Rashba spin-orbit and the subband coupling as well as under the influence of a magnetic impurity in the wire. In this thesis, we examine a quasi-one dimensional InAs wire with wire width about 40nm. A potential barrier/ well is introduced in the wire by using a gate voltage, with the length of barrier/ well width varying from 100 to 600 nm. The magnetic impurity includes two parts: (i) the spin-flip part, meaning the impurity magnetic moment part, which can flip the electron spin during scattering, and (ii) the non-flip part, meaning the coulomb part, which can be attractive, repulsive or neutral, and conserves the electron spin during scattering. A theory is developed to calculate the spin-dependent electron transmission through the wire, and numerical data are presented. The direction of the magnetic moment and the sign of the non-flip part are found to be critical to the spin filtering. The barrier height / well depth can be tuned via the electric gate, providing a direct and efficient means to optimize the filtering.