Spin Electronics: High Temperature Ferromagnetic Semiconductor Materials and Devices

这笔赠款是由工程局电气和通信系统司以及化学和运输系统司共同资助的。 该提案是响应21世纪世纪自旋电子学倡议，计划征求NSF 02-036。该提案的重点是稀磁半导体（DMS），这是未来电子和光电器件的有前途的材料，利用电子的电荷和自旋。这些材料在自旋阀、非易失性磁性随机存取存储器、量子计算和其他自旋极化输运和光学器件中具有潜在的应用。最近的大部分工作集中在III-V DMS上，其显示出优异的低温铁磁性能。具有105 K居里温度的DMS替代III-V族合金已经实现，但是，由于难以制备同时具有高居里温度和磁化强度的材料，它们在薄膜异质结构中的应用受到限制。然而，铁磁半导体外延的最新进展表明，具有高居里温度的III-V材料应该是可以实现的。此外，包括假III-V族化合物II-IV-V2黄铜矿的其它半导体系统最近已显示具有高居里温度。建议的工作建立在我们最近的示范InMnAs合金的过渡温度超过300 K制备的金属有机气相外延（MOVPE），以及我们发现的高Tc II-IV-V2化合物。MOVPE使得能够制备具有高磁化的III-V DMS，这是通过体技术不可能的。待研究的具体系统包括：InMnAs和II-IV-V2化合物ZnMnP 2和MnGeP 2。虽然这些半导体已经显示出相当大的前景，但磁性物质的性质还没有得到很好的理解。在所提出的计划DMS晶体，薄膜和量子结构将沉积一系列的磁性离子浓度，以优化居里温度和磁化。将确定原子结构和磁性之间的关系，并与理论进行比较。 这些计算将使用高精度的完全线性化增强平面波（FLAPW）方法。特别令人感兴趣的是在何种程度上发生的磁性离子集群和它们的作用，形成高居里温度的合金。将使用的实验技术包括高分辨率透射电子显微镜、扩展X射线精细结构分析、温度和磁场相关磁化测量、霍尔效应和磁光测量。几种薄膜自旋电子和光电异质结构将被制备和测量其自旋相关的性质。该计划将涉及在磁性半导体材料和器件研究的博士研究生和本科生的培训。桑迪亚国家实验室和西北大学之间的合作。大学将进一步发展。与美国的国际合作。将在韩国的蔚山进行。

This grant has been co-funded by the Division of Electrical and Communications Systems, and the Division of Chemical and Transport Systems in the Engineering Directorate. This proposal was received in response to the Spin Electronics for the 21st century initiative, Program Solicitation NSF 02-036. The proposal focuses on diluted magnetic semiconductors (DMS), which are promising materials for future electronic and opto-electronic devices that utilize both the charge and the spin of electrons. These materials have potential uses in spin valves, non-volatile magnetic random access memories, quantum computation and other spin polarized transport and optical devices. Much of the recent work has focused on the III-V DMS which have shown excellent low temperature ferromagnetic properties. DMS substitutional III-V alloys with Curie temperatures of 105 K have been realized Their utilization in thin film heterostuctures, however, has been limited because of difficulties in preparing materials with both a high Curie temperature and magnetization. Nevertheless, recent advances in the epitaxy of ferromagnetic semiconductors indicate that III-V materials with high Curie temperatures should be realizable. Furthermore other semiconductor systems including the pseudo III-V compounds II-IV-V2 chalcopyrites have been recently shown to have high Curie temperatures. The proposed work builds upon our recent demonstration of InMnAs alloys with transition temperatures in excess of 300 K prepared by metal-organic vapor phase epitaxy (MOVPE) as well as our discovery of high Tc II-IV-V2 compounds. MOVPE enables the preparation of III-V DMS with high magnetization not possible by bulk techniques. Specific systems to be investigated include: InMnAs, and II-IV-V2 compounds ZnMnP2 and MnGeP2. While these semiconductors already show considerable promise, the nature of the magnetic species is not well understood. In the proposed program DMS crystals, thin films and quantum structures will be deposited with a range of magnetic ion concentrations to optimize both the Curie temperature and magnetization. The relationship between the atomic structure and magnetic properties will be determined and compared to theory. The highly accurate fully linearized augmented plane wave (FLAPW) method will be used for these calculations. Of specific interest is the extent to which magnetic ion clustering occurs and their role in the formation of alloys with high Curie temperatures. Experimental techniques to be used included high resolution transmission electron microscopy, extended x-ray fine structure analysis (EXAFS), temperature and field dependent magnetization measurements, Hall effect and magneto-optical measurements. Several thin film spintronic electronic and opto-electronic heterostructures will be fabricated and their spin dependent properties measured. The program will involve the training of both doctoral graduate and undergraduate students in magnetic semiconductor materials and device research. Collaborations between Sandia National Laboratories and Northwestern. University will be further developed. International collaboration with U. of Ulsan, South Korea will be undertaken.