SPIN ELECTRONICS: III-V/Mn Ferromagnetic Semiconductors for Device Applications

0224206罗本建议书是对21世纪自旋电子学计划NSF 02-036的响应。该计划的重点是III-V/Mn材料及其异质结构的生长、表征和器件研究。该计划的目标是开发铁磁共振带间隧道二极管(FRITD)和偏振可调红外发光二极管。为了为这些器件开发优化的材料，并演示原理操作的证明，器件结构将在材料生长的同时进行制造和测试，以提供对材料工作的直接反馈。布法罗大学(UB)对这些器件的组成材料的结构、输运/磁输运、光学和磁性进行了初步研究，揭示了与在高片层密度下掺入磁性Mn++离子有关的几个有趣的问题。更重要的是，人们发现这些材料的结构、光学、输运和磁性是紧密联系在一起的。这些研究表明，需要从原子水平设计材料，以便同时优化电传输、光学和磁性；这是该计划的关键任务之一。具体地说，为了解决这些复杂的问题，建议成立一个多学科的研究小组，对III-V基铁磁材料/结构、基本性质、自旋注入/界面效应和器件进行全面研究。在这项拟议的工作中，布法罗大学小组将：1)制作系统的系列样品，其中的Mn的亚单分子层被插入到III-V晶格中；2)探索作为生长条件的函数的磁性、电输运、光学特性和结构质量；3)优化生长条件以产生最高的居里温度；4)制造和测试器件结构。它将利用现有的基础设施，包括合作研究和学生互动，这些基础设施已经为正在进行的自旋电子材料开发项目建立，该项目由美国国防高级研究计划局(DARPA)支持，专注于其他材料。该项目将资助三名全日制研究生，通过与相关工作的协同，这是一项实质性的努力。这一计划的成功将直接影响到自旋电子学领域的关键问题，即提高居里温度，生产适合于实际器件的材料和自旋注入到半导体异质结中。与目前在DARPA支持的项目中研究的其他材料相结合，UB的材料工作是全国最强的之一。器件的制备和表征将在解决与涉及III-V材料的自旋注入以及电子(而不是空穴)自旋注入的可能性相关的材料研究中的瓶颈问题方面发挥主导作用。

0224206LuoThis proposal was received in response to the Spin Electronics for the 21st Century Initiative, Program Solicitation NSF 02-036. The proposal focuses on growth, characterization and device studies of III-V/Mn materials and their heterostructures. The goal of this program is to develop ferromagnetic resonant interband tunneling diodes (FRITD) and polarization tunable infrared light emitting diodes. In order to develop optimized materials for these devices, and to demonstrate proof of principle operation, device structures will be fabricated and tested in parallel with the materials growth to provide direct feedback to the materials effort. Preliminary studies at the University at Buffalo (UB) of structural, transport/magneto-transport, optical and magnetic properties of the constituent materials for these devices have revealed several interesting problems associated with the incorporation of magnetic Mn++ ions at high sheet densities. More importantly, it was found that the structural, optical, transport and magnetic properties of these materials are closely connected. These studies demonstrate the need for designing materials from the atomic level so that electrical transport, optical and magnetic properties are simultaneously optimized; this is one of the key tasks of this program. Specifically, to tackle these complex problems, it is proposed to form a multidisciplinary research team to carry out comprehensive studies of III-V-based ferromagnetic materials/structures, fundamental properties, spin injection/interface effects and devices. In this proposed work, the University at Buffalo group will: 1) fabricate systematic sets of samples of GaAs/Mn, GaSb/Mn, and InAs/Mn digital alloys, in which submonolayers of Mn are inserted in the III-V lattice; 2) explore the magnetic, electrical transport, optical properties and structural quality as a function of growth conditions; 3) optimize growth conditions to produce the highest Curie temperatures; 4) fabricate and test device structures.The program is formulated to maximize student involvement in multidisciplinary research by engaging engineering and physics students working together to reach common goals. It will utilize existing infrastructure, both for collaborative research and for student interactions, which has been established for the on-going spintronic materials development project supported by the Defense Advanced Research Project Agency (DARPA) focusing on other materials. A total of three full-time graduate students will be supported in this program, a substantial effort made possible by the synergism with the related work. The success of this program will have immediate impact on the key problems in the area of spintronics, namely, improving the Curie temperature and producing materials suitable for practical devices and spin injection into semiconductor heterostructures. Combined with the other materials currently studied in the DARPA-supported project, the materials effort at UB represents one of the strongest in the country. The device fabrication and characterization will lead the way in resolving bottlenecks in materials research related to spin-injection involving III-V materials, and the possibility of electron (rather than hole) spin injection.