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

研究的目的是建立自旋电子学器件的基础技术，其中信息是由自旋产生和处理的。在这里，我们设计和制造铁磁/非磁性半导体量子结构，并研究了独特的光学，电学和磁学性质，在这些结构中通过控制载流子，原子核，激子和磁性离子的自旋状态与电气和光学手段。本文的主要研究成果如下：1.通过系统的实验研究，证实了p-铁磁/n^+-非磁半导体隧道结中电子自旋注入效率对n^+-GaAs界面层厚度和掺杂浓度的敏感性，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n^+-GaAs/AlGaAs（110）量子威尔斯阱中各向异性g因子和超精细相互作用的影响。我们观察到了动态核极化的双稳性和滞后现象，这些现象被自洽计算很好地再现。3.在n-GaAs/AlGaAs（110）量子阱中，通过改变背景电子密度，可以控制超精细相互作用和动态核极化。我们发现，实验观察可以解释的金属-绝缘体转变，超精细相互作用的敏感依赖。

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.