Monte Carlo simulation of spin-polarized transport in a semiconductor heterostructure and spin injection through a Schottky barrier

A method for Monte Carlo simulation of 2D spin-polarized electron transport in III-V semiconductor heterojunction Field Effect Transistors (FETs) is presented. In the simulation, the electron dynamics in coordinate and in-plane momentum space is treated semiclassically. The density matrix description of the spin is incorporated in the Monte Carlo method to account for the spin polarization dynamics. The spin-orbit interaction in the spin FET lead to both coherent evolution and dephasing of the electron spin polarization. Spin-independent scattering mechanisms, including optical phonons, acoustic phonons and ionized impurities, are implemented in the simulation. These scattering processes produce spin dephasing through the spin-orbit interaction. The electric field is determined self-consistently from the charge distribution resulting from the electron motion.; Utilizing the above model, we study the in-plane transport of spin-polarized electrons in III-V semiconductor quantum wells (QWs). Monte Carlo simulations have been carried out for temperatures in the range 77--300 K. The above model is also applied to study spin-polarized transport properties of 2D electron gas in semiconductor spin-FET structure. The specific symmetry of spin-orbit terms (Rashba and Dresselhaus) leads to strong anisotropy of spin dynamics in the low field regime. Coherent spin evolution and spin dephasing are investigated for different orientations of the device channel related to the crystallographic axes. Efforts have been made to suppress spin dephasing while conserving coherent oscillation of spin polarization required for spin-FET design. Results derived from this study provide useful information to assist in optimization of the spin-FET performance.; As an important step forward, the Monte Carlo model developed above is further extended to incorporate the spin injection through the Schottky barrier which is a very important topic in spintronics. In this extended model, the spin polarization and the energy distribution function of the injection rate for electrons are determined by the thermionic emission and tunneling process. With the extended Monte Carlo model, effect of the width of a step-doping region near the Schottky contact on the spin injection is investigated. Useful information is provided for the barrier design to achieve efficient spin injection and high spin-polarized current in spintronic devices.