Spin injection and spin control in magnetic/non-magnetic semiconductor quantum structures

本研究的目的是建立自旋电子学设备的基础技术，其中信息是由自旋产生和处理的。本文设计并制备了铁磁/非磁性半导体量子结构，并通过电学和光学手段控制载流子、原子核、激子和磁性离子的自旋态，研究了这些结构中独特的光学、电学和磁学性质。本文的研究成果总结为：1。我们通过系统的实验证明了p-铁磁/n^+-非磁性半导体隧道结中电子自旋注入的效率敏感地取决于n^+-GaAs界面层的厚度和掺杂浓度，并给出了优化条件2。利用时间分辨法拉第旋转技术研究了各向异性g因子和超精细相互作用对n-GaAs/AlGaAs（110）量子阱的影响。我们观察到动态核极化的双稳性和迟滞性，并通过自洽计算得到了很好的再现。我们还评估了动态核极化的程度为30%。我们证明了在门控n-GaAs/AlGaAs（110）量子阱中，可以通过改变背景电子密度和栅极电场来控制超精细相互作用和动态核极化。我们证明了实验观察可以用金属-绝缘体跃迁来解释，超精细相互作用敏感地依赖于金属-绝缘体跃迁。

The purpose of the research is to establish fundamental technology for spintronics devices in which information is born and processed by spins. Here, we designed and fabricated ferromagnetic/non-magnetic semiconductor quantum structures and investigated the unique optical, electrical, and magnetic properties in those structures by controlling the spin states of carriers, nuclei, excitons, and magnetic ions with electrical and optical means. The achievements of the research are summarized as :1.We manifested that the efficiency of electrical electron spin injection in p-ferromagnetic/n^+-non-magnetic semiconductor tunnel junction sensitively depends on the thickness and doping concentration of n^+-GaAs interface layer by performing a systematic experiments, and showed the optimized condition.2.We studied the effect of anisotropic g-factor and hyperfine interaction in n-GaAs/AlGaAs (110) quantum wells by time-resolved Faraday rotation technique. We observed bistability and hysteresis of dynamic nuclear polarization, which were well reproduced by self-consistent calculation. We also evaluated the degree of dynamic nuclear polarization to be 30%.3.We demonstrated that the hyperfine interaction and dynamic nuclear polarization can be controlled by changing the background electron density with gate electric field in a gated n-GaAs/AlGaAs (110) quantum well. We showed that the experimental observation can be explained by metal-insulator transition, on which the hyperfine interaction depends sensitively.