Ferromagnetic Semiconductor Nanostructures

该项目涉及与传统电子学和铁磁性材料的杂化有关的材料问题，是增强现有信息存储设备的候选材料，并为基于自旋注入和自旋操纵的新型类似电子器件(自旋电子学)提供成分。这项工作的目的是合成新型的铁磁半导体纳米结构，以便从根本上了解它们的磁性、输运和光学性质。目标包括：(I)全面了解磁性及其与半导体性质的关系；(Ii)提高居里温度；(Iii)改善光学性质。东北大学的分子束外延装置将合成III-V铁磁半导体的新材料和新结构。一个主要的焦点是探索除锰以外的过渡金属离子，从铬开始，但也要改善含锰材料。一些理论和实验研究表明，III-V材料中的铬具有较高居里温度的潜力。Pi‘s群已经发展了大约一年，最近发现了高达700K的转变温度，带隙工程将有助于研究磁性离子的电子能级依赖关系。例如，在砷化镓中，铬有一个类受主的跃迁，即禁带宽度。通过将Sb和As合金化，受主能量可以降低到与GaAs中的Mn相当的水平。改变磁性离子的能级对于测试和发展半导体中铁磁性的理论模型很重要。磁性和输运实验将用来研究半导体载流子和铬离子之间的相互作用。量化这种相互作用对于阐明在(Ga，Cr)As磁化过程中观察到的磁极化子内部和之间的耦合以及在输运测量中观察到的载流子局域化效应是很重要的。这个项目解决了材料科学中与重大技术相关的主题领域中的基础材料研究问题，并强调研究和教育的整合。该研究计划提供了在使用尖端科学设备方面的实践经验的绝佳机会。研究生和本科生将参与纳米结构材料的设计、合成、表征和科学。广泛的资源和协作方面，为从事跨学科前沿研究的研究生和本科生提供了特殊的教育和培训机会。***

This project addresses materials issues relevant to the the hybridization of conventional electronics with ferromagnetic materials, candidates for enhancing present information storage devices, as well as providing ingredients for novel electronic-like devices based on spin injection and spin manipulation (spintronics). The objective of the proposed work is to synthesize novel ferromagnetic semiconductor nanostructures in order to gain fundamental understanding of their magnetic, transport, and optical properties. Goals include: (i) comprehensive understanding of the magnetism and its relation to the semiconducting properties; (ii) higher Curie temperatures; and (iii) improved optical properties. Novel materials and structures of III-V ferromagnetic semiconductors will be synthesized in Northeastern's MBE facility. A primary focus is the exploration of transition metal ions other then Mn, beginning with Cr, but also to improve Mn containing materials. Several theoretical and experimental studies indicate that Cr in III-V materials has the potential for high Curie temperatures. The PI's group has been growing (Ga,Cr,Mn)As for about one year and has recently discovered transition temperatures as high as 700 K. Bandgap engineering will be used to facilitate the investigation of the dependence of electronic energy levels of magnetic ions. For example, Cr has an acceptor-like transition that is midgap in GaAs. By alloying antimony with arsenic, the acceptor energy can be reduced to a level comparable to Mn in GaAs. Varying the energy level of magnetic ions is important for testing and developing theoretical models of ferromagnetism in semiconductors. Magnetic and transport experiments will be used to examine the interaction between the semiconductor carriers and Cr ions. Quantifying this interaction is important for elucidating the coupling within and between magnetic polarons observed in the magnetization of (Ga,Cr)As and the carrier localization effects observed in transport measurements. %%% This project addresses basic materials research issues in a topical area of materials science with significant technological relevance, and places emphasis on the integration of research and education. The research program provides excellent opportunities for hands-on experience in the use of sophisticated scientific equipment. Graduate and undergraduate students will be involved in the design, synthesis, characterization, and science of nanostructured materials. The broad resources, and collaborative aspects, provide special opportunities for education and training of graduate and undergraduate students involved in interdisciplinary forefront research. ***