Photogalvanic effects in HgTe quantum well structures and all-electric detection of radiation polarization

最近，人们对利用半导体量子阱结构中载流子的自旋和它们的电荷来实现自旋电子学和自旋光电子学等新概念很感兴趣。自旋光电子学的一个新方面是在低对称性量子结构中产生自旋光电流。在我们以前对II-V半导体结构所做的工作中，我们已经证明，如果满足一些一般的对称性要求，量子阱中电子的非平衡自旋极化必然与势垒中的电流联系在一起。本项目旨在利用这些现象研究SiGe量子结构中的自旋输运。应该研究两种类型的自旋光电流：圆形光电流效应和自旋-电偶效应。虽然在p型SiGe结构中已经观察到了圆形光电流效应，但对于n型材料中的CPGE和SiGe量子阱中的自旋-电偶效应，还只有初步的数据。实验将与理论发展同步进行。因此，我们应该深入了解这些新的自旋相关现象的本质。应用自旋光电流，可以获得有关SiGe量子阱中自旋输运的基本信息，包括与自旋有关的量子阱能带结构和自旋弛豫过程的细节。实验应使用红外辐射，使单极自旋取向非常接近于电子自旋注入条件。这些关于SiGe结构的数据特别重要，因为这种材料是一种很有前途的自旋电子学系统。该项目的进一步目标之一是开发一种新的自旋光电子器件：一种具有亚纳秒时间分辨率的快速室温螺旋度红外辐射探测器。

Lately, there is much interest in the use of the spin of carriers in semiconductor quantum well structures together with their charge to realize novel concepts like spintronics and spin-optoelectronics. One of the new aspects of spin-optoelectronics is the generation of spin photocurrents in low symmetric quantum structures. In our previous work carried out on II-V semiconductor structures it has been shown that a non-equilibrium spin polarization of electrons in a quantum well is inevitably linked with an electric current in the well if some general symmetry requirements are met. This project is directed towards the investigation of spin transport in SiGe quantum structures applying these phenomena. Two types of spin photocurrents should be studied: the circular photogalvanic effect and the spin-galvanic effect. While the circular photgalvanic effect is already observed in p-type SiGe structures, to the CPGE in n-type materials and to the spin-galvanic effect in SiGe quantum wells there are only preliminary data. Experiments will be paralleled by theoretical development. As a result we should get insight into the nature of these new spin-related phenomena. Applying the spin photocurrents the basic information on spin transport in SiGe quantum wells comprising the spin related details of the band structure of quantum wells and spin relaxation processes should be obtained. Experiments should be carried out using infrared radiation which results in the monopolar spin orientation being very close to the condition of the electrical spin injection. These data obtained for SiGe structures are of particular importance because this material is a promising system for spin-based electronics. One of the further aims of this project is to develop a new spin-optoelectronic device: a fast room temperature helicity sensitive detector for infrared radiation with subnanosecond time resolution.