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.
