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

这份提案是为了响应21世纪的自旋电子学倡议，计划征集NSF 02-036。该提案的重点是研究各种自旋发光二极管(自旋发光二极管)中的自旋注入现象。拟议的工作既有实验部分，也有理论部分。在这项提议的实验部分中使用的所有器件的核心都有一个AlGaAs(N)/GaAs/Algas(P)发光二极管。二极管发射的圆极化被用来确定限制在GaAs层中的载流子的相对自旋布居。在基于锌锰硒的自旋发光二极管中，锌锰硒接触层是自旋极化电子的来源。在这个研究得很好的系统中，我们将利用远红外(FIR)单色光来探索电子和空穴在器件不同部件处的共振加热效应。通过选择FIR波长和外部施加的磁场，可以研究加热对器件特定组件(GaAs层、AlGaAs层或ZnMnSe层)中特定载流子(电子或空穴)的二极管输出的影响。此外，我们将使用特殊设计的n型调制掺杂的ZnMnSe自旋LED来研究限制在每个二极管的GaAs量子阱中并占据多个朗道能级的电子的布居统计。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。这样的器件预计只需要几百个高斯就能工作，而最近开发的铁基自旋LED需要几特斯拉才能工作，在这些自旋LED中，易磁化轴位于铁层平面。最后，我们计划探索AlGaMnAs作为一种潜在的自旋极化空穴注入器。在这一建议的理论部分，我们描述了对自旋注入LED中发生的几个重要现象的研究，这些现象影响了这些器件的运行和效率。我们建议研究载流子在GaAs势垒中的俘获过程，以及随后对最低限制子带E1和H1的能量弛豫。我们将探索声子发射和相关的自旋翻转过程的作用。拟议工作的实验部分和理论部分之间的密切和协同关系预计将有助于该项目的成功。拟议工作的一个教育方面将涉及该项目中的两名本科生(来自物理和/或电子工程)与研究生和合作研究人员密切合作。REU计划将要求为本科生提供支持

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