Theoretical Study Of The Quantum Transport In The Extended Datta-Das Spin Field Effect Transistor

We study the quantum transport of the electron in the ferromagnetic-semiconductor- ferromagnetic (F/S/F) system, with consideration of the transmission and conductance properties affected by such as the Rashba and Dresselhaus Spin-orbit coupling (SOC), ferromagnetic (FM) leads, potential barriers, band mismatch and external magnetic fields.In the first, we make a brief introduction of the content and history of spintronics in chapter one. The Hamiltonian of the spin-orbit terms with both the Rashba and Dresselhaus in solid materials and quantum devices are discussed based on the prototype in the Dirac equation. And then, in the second chapter we introduce some basic methods for solving the problems about electron transport in F/S/F system. Furtherly, we investigate the scattering problem when the electron transport through the spin field effect transistors (SFET) with a normal incidence angle, and eatablish a set of functions by using the Griffth’s boundary conditions. The transmission probability and reflection probability are obtained, the conductance variations of the SOC strength and device size are also discussed in this situation. As following, we mainly study the transmission and conductance properties in the extended Rashba-Dresselhaus SFET. By adopting the analytical and numerical results we investigate the different behavior of the transmission and conductance for different and complicate effects of the Rashba and Dresselhaus SOC, incident electron, potential barriers and band mismatch. At the same time, we study the transmission and conductance properties in the fourth chapter as taking into the strength of the FM leads, and get that the SOC terms can modulate the spin electron transport more distinct. Moreover, in chapter five, we also consider the effects of the external magnetic field effect and the direction of the two FM leads, by numerical calculation we find that the external magnetic field makes an excllent modulation to the electron spin polarization. In the last chapter, we study the electron transport through the Rashba-Dresselhaus SFET with an oblique incidence. By using the same calculation methods we get the variations of the transmission and spin polarization properties versus the device size, electron incident angle and potential barrier strength. By investigating of the electron transport of the Rashba-Dresselhaus SFET, we get more profound understanding about the F/S/F transport system. The studies of these systems also make an important guidable meaning in factual applications of the device manufacting and analyzing.