Spin Electronics: Optical Studies of Spin Injection in Semiconductor/Semiconductor and Metal/Semiconductor Heterostructures

该提案是响应21世纪世纪自旋电子学倡议，计划征集NSF 02-036而收到的。该提案的重点是研究各种自旋发光二极管（自旋LED）中的自旋注入现象。 拟议的工作有一个实验以及理论的组成部分。 将在本提案的实验部分中使用的所有设备在其核心处具有AlGaAs（n）/GaAs/AlGAs（p）发光二极管。 二极管发射的圆偏振被用来确定限制在GaAs层中的载流子的相对自旋布居。 在基于ZnMnSe的自旋LED中，ZnMnSe接触层是自旋极化电子的源。 在这个研究系统中，我们将探索在使用远红外（FIR）单色光的设备的各个组件的电子和空穴的共振加热的效果。 选择FIR波长和外部施加的磁场允许研究加热对器件特定组件（GaAs，AlGaAs或ZnMnSe层）中特定载流子（电子或空穴）的二极管输出的影响。 此外，我们将使用专门设计的，n型调制掺杂ZnMnSe自旋发光二极管研究电子的人口统计限制在GaAs量子阱的每个二极管，并占据了一些朗道水平。 第二种类型的自旋LED将使用铁磁层作为自旋极化电子源，其易磁化轴垂直于层轴。 这种器件预计仅需要几百高斯来操作，而最近开发的Fe基自旋LED所需的几个特斯拉，其中易磁化轴位于Fe层平面中。 最后，我们计划探索AlGaMnAs作为一个潜在的自旋极化空穴注入器。 在这个建议的理论部分，我们描述了几个重要的现象，发生在自旋注入LED和影响这些设备的操作和效率的调查。 我们打算研究载流子在GaAs威尔斯阱中的俘获过程以及随后的能量弛豫到最低限制子带e1和h1。 声子发射和相关的自旋翻转过程的作用将被探讨。 拟议工作的实验和理论组成部分之间的密切和协同关系预计将有助于项目的成功。拟议工作的教育方面将涉及两名本科生（来自物理和/或EE）与研究生和合作研究人员密切合作。 支持本科生将要求从REU计划

This proposal was received in response to the Spin Electronics for the 21st century Initiative, Program solicitation NSF 02-036. The proposal focuses on the study of spin injection phenomena in a variety of spin Light Emitting Diodes (spin-LEDs). The proposed work has an experimental as well as a theoretical component. All the devices that will be used in the experimental part of this proposal have an AlGaAs(n)/GaAs/AlGAs(p) light emitting diode at their core. The circular polarization of the diode emission is used to determine the relative spin population of carriers confined in the GaAs layer. In ZnMnSe based spin-LEDs the ZnMnSe contact layer is the source of spin polarized electrons. In this well studied system we will explore the effects of resonant heating of the electrons and holes at various components of the device using far infrared (FIR) monochromatic light. Choice of FIR wavelength and of the externally applied magnetic field allows the study of the effects of heating on the diode output of a particular carrier (electron or hole) in a specific component of the device (GaAs, AlGaAs or ZnMnSe layer) . In addition we will be using specially designed, n-type modulation doped ZnMnSe spin LEDs to study the population statistics of electrons confined in the GaAs quantum well of each diode and occupying a number of Landau levels. The second type of spin-LED will use a ferromagnetic layer as spin polarized electron source with the easy magnetization axis perpendicular to the layer axis. Such a device is expected to require only a few hundred Gauss to operate, as opposed to a few tesla required by the recently developed Fe-based spin LEDs in which the easy magnetization axis lies in the Fe layer plane. Finally we plan to explore AlGaMnAs as a potential spin polarized hole injector. In the theoretical component of this proposal we describe investigations of several important phenomena that take place in spin injection LEDs and affect the operation and efficiency of these devices. We propose to investigate the capture process of the carrier in the GaAs wells and the subsequent energy relaxation to the lowest confinement subbands e1 and h1. The role of phonon emission and the associated spin-flip processes will be explored. A very close and synergistic relationship between the experimental and the theoretical components of the proposed work is expected to contribute to the success of the project.An educational aspect of the proposed work will involve two undergraduate students in the program (from Physics and/or EE) working closely with graduate students and the co-investigators. Support for the undergraduate students will be requested from the REU program