Basic Research of a Spin Transistor Based on the Quantum Transport in an Inhomogeneous Magnetic Field

点击翻译按钮获取中文摘要

This project has been aimint at the analysis of the band structures and the quantum carrier transport in both diluted magnetic semiconductors and nano structures composed of compound semiconductors. We have obtained the following results so far :・Analysis of the band structures of semiconductor nano structures such as quantum wells and quantum wires taking the spin-orbit interaction into accountFrom this analysis, we have concluded the conventional parabolic band approximation is no longer appropriate to predict and design optical properties of quantum nano structures. We have also found an external electric field significantly affects the band structures of such nano structures (Stark effect) which can be precisely simulated by taking into account both the multi-band effective mass theory and the the spin-orbit coupling.・Analysis of the quantum transport of carriers in nano structuresWe describe a method for calculating quantum transport of carriers in nano structures. In this method, we use the lattice-Wigner Weyl formalism of the field operators to deduce the quantum mechanical distribution function (Wigner-Weyl function) in which multiband-effective-mass theory is taken into account. The physical quantities such as carrier densities and particle flow densities can be more readily computed from the distribution function than conventional methods. The formulation is applied to analyze quantum hole transport in a double barrier resonant tunneling diode. As a result, the current-voltage characteristics show considerable band-mixing nature of the light hole and the heavy hole. This theory may be applicable to analyze quantum transport of carriers in quantum optical devices such as quantum-well lasers and electro-optical modulators where the band-mixing effect plays an important role.