Exploring of Bulk and Structure Inversion Asymmetry in GaAs/AlGaAs Quantum Well Structures Applying Spin Photogalvanics

本计画旨在研究半导体量子井结构中之体反转与结构反转不对称性。量子阱结构中的反转不对称性及其操纵对于半导体系统中自旋极化电子的产生、操纵和探测起着重要的作用。为了获得关于BIA和SIA的信息，我们将使用我们小组在项目第一部分的框架中开发的新技术。该技术是基于太赫兹辐射引起的光电流效应的研究，包括磁光电流效应，循环光电流效应和自旋光电流效应。该项目的重点是研究BIA和SIA在不同晶体取向的各种III-V化合物材料中的作用。特别地，反转不对称性随温度、量子阱形状和载流子密度的变化的行为将被研究。我们在（110）取向结构上获得的初步结果表明，结构反转不对称性可以通过改变（110）掺杂层的位置可控地调节到零。这种方法应扩展到（001）生长的结构提供的信息，需要获得完美的对称结构与零Rashba常数和结构具有相等的Rashba和Dresselhaus自旋分裂的生长条件。后一种结构应该显示出极长的自旋弛豫时间，并且对于实现基于自旋输运的器件特别感兴趣。

The project is aimed to the investigation of bulk (BIA) and structure (SIA) inversion asymmetry in semiconductor quantum well (QW) structures. Inversion asymmetry in QW structures and its manipulation play an important role for the generation, manipulation and detection of spin polarized electrons in semiconductor systems. To gain the information on BIA and SIA we will use a novel technique developed by our group in the framework of the first part of the project. The technique is based on investigation of terahertz radiation induced photogalvanic effects, comprising magneto-photogalvanic effect, circular photogalvanic effect and spin-galvanic effect. The project is focused on investigation of BIA and SIA in various Ill-V-compound materials of different crystallographic orientations. In particular, the behavior of the inversion asymmetry upon variation of temperature, QW shape and carrier density will be studied, Our preliminary results obtained on (llO)-oriented structures demonstrated that the structure inversion asymmetry can be controllably tuned to zero by variation of (-doping layer positions. This method should be extended to (00l)-grown structures providing an information on growth conditions needed to obtain perfectly symmetric structures with zero Rashba constant and structures with equal Rashba and Dresselhaus spin splittings. The latter structures should show extremely long spin relaxation times and are of particular interest for realization of spin transport based devices.