Muonium in Wurtzite Structured Semiconductors

在纤锌矿结构半导体中由μ素（Mu）形成的缺陷态使用一系列相关技术进行了研究，称为μ子自旋旋转，共振和弛豫，或mSR。 μ 鎓是一种非常轻的氢同位素，其中正μ介子取代了质子。 这些研究的结果提供了这些材料中孤立的氢杂质的行为的关键信息。 重点将放在第三族氮化物和II-VI化合物上;特别是目前正在开发的用于短波长激光器和其他电光应用的宽禁带材料。 氢是这些材料中的一种重要杂质，它与其他杂质发生反应，改变相关的电学和光学特性，因此了解其影响对于将这些材料用于特定用途至关重要。 对μ 鎓的研究将产生关于所谓钝化络合物的孤立氢前体的信息，这是很难通过任何其他手段获得的。 将获得H（Mu）的各种位点和电荷状态，将检查每个状态的运动或扩散特性，并表征这些状态之间的各种转变。 该项目遵循了立方半导体中Mu的非常成功的研究，其中开发了Mu状态和过渡的动力学的完整模型。 六方纤锌矿结构有两倍多的网站穆钻石或锌结构，使所观察到的网站和过渡更困难的分配。 Mu在一些II-VI族化合物中除了通常的深能级状态外还形成浅施主;因此将在II-VI族合金中研究从深能级到浅能级的交叉行为。 这个项目的最终目标是提供足够详细的描述所观察到的μ状态，一个准确的动力学模型的纤维锌矿材料中的μ可以实现。 其他半导体的经验表明，穆的结果产生半定量模型H杂质。这项研究将与学生谁将接受培训，在21世纪世纪的科学/技术劳动力有用的就业做准备进行。了解氢杂质在为蓝光和紫外激光器以及其他光学应用开发的半导体中的作用，对于将这些材料用于特定用途至关重要。 然而，氢杂质行为的许多方面一直极难直接研究。 在这个项目中，我们研究了一种被称为μ 鎓的人工产生的杂质，它是通过将一种短寿命粒子植入这些材料中而形成的。 μ素在本质上所有重要性质上都模仿了氢的行为，但更容易研究。 我们计划研究的材料包括氮化镓、氮化铝和其他半导体化合物。 这些激光材料有一个共同的结构，称为纤锌矿，我们的主要目标是开发一个完整的模型，这种结构的材料中的μ 鎓（氢）杂质的行为。 我们以前对更常见的半导体（如具有立方结构的硅和砷化镓）中的μ 鎓进行了非常成功的研究，提供了立方半导体中孤立氢杂质性质的详细图像，并作为当前工作的指导。 该项目的结果将提供实验数据，用于与目前用于预测技术上重要的纤锌矿半导体中氢行为的理论计算进行比较。 这项工作的成功完成将允许氢对短波长激光材料的电学和光学特性的长期影响的更好的模型，以及这些影响如何在典型的设备使用条件下通过各种处理步骤和老化进行修改。这项研究将与学生一起进行。他们将接受当代凝聚态物理和材料科学前沿领域的培训，为进入21世纪的科学/技术劳动力做准备。

The defect states formed by muonium (Mu) in wurtzite structured semiconductors are investigated using a series of related techniques known as muon-spin rotation, resonance, and relaxation, or mSR. Muonium is effectively a very light isotope of hydrogen in which a positive muon replaces the proton. Results of these studies provide crucial information on the behavior of isolated hydrogen impurities in these materials. The focus will be on the group-III nitrides and the II-VI compounds; in particular, the wide gap materials currently being developed for short wavelength lasers and other electro-optical applications. Hydrogen is an important impurity in these materials that reacts with other impurities to modify the related electrical and optical properties, thus understanding its effects is crucial to engineering these materials for specific uses. The muonium studies will yield information on the isolated hydrogen precursor to so-called passivation complexes that is very difficult to obtain by any other means. The various sites and charge states for H (Mu) will be obtained, the motion or diffusive characteristics of each state will be examined, and various transitions between these states characterized. This project follows very successful studies of Mu in the cubic semiconductors in which a complete model of the dynamics of Mu states and transitions was developed. The hexagonal wurtzite structure has twice as many sites for Mu as diamond or zincblende structures making assignments of the observed sites and transitions more difficult. Mu forms a shallow donor in some of the II-VI compounds in addition to the usual deep-level states; thus the crossover from deep to shallow behavior will be investigated in II-VI alloys. The ultimate goal of this project is to provide sufficiently detailed characterization of the observed Mu states that an accurate dynamic model of muonium in the wurtzite materials can be realized. Experience with other semiconductors indicates that the Mu results yield a semi-quantitative model for H impurities. This research will be conducted with students who will receive training in preparation for useful employment in the scientific/technical workforce of the 21st Century. Understanding the role of hydrogen impurities in the semiconductors being developed for blue and UV lasers and other optical applications is crucial to engineering these materials for specific uses. However, many aspects of the behavior of hydrogen impurities have been extremely difficult to study directly. In this project, we investigate an artificially produced impurity known as muonium that is formed by implanting a short lived particle into these materials. Muonium mimics the behavior of hydrogen in essentially all its important properties, but is far easier to study. The materials we plan to investigate include gallium nitride, aluminum nitride and other semiconductor compounds. These laser materials have a common structure known as wurtzite and our main goal is to develop a complete model of the behavior of muonium (hydrogen) impurities in materials with this structure. Our previous very successful studies of muonium in more common semiconductors, such as silicon and gallium arsenide which have a cubic structure, provided a detailed picture of the properties of isolated hydrogen impurities in the cubic semiconductors and serves as a guide for the current work. The results of this project will provide the experimental data for comparison to the theoretical calculations currently being used to predict the behavior of hydrogen within the technologically important wurtzite semiconductors. Successful completion of this work will allow a better model of the long term effects of hydrogen on the electrical and optical properties of short wavelength laser materials, and how these effects may be modified by various processing steps and aging under typical device use conditions. This research will be conducted with students. They will receive training in a forefront area of contemporary condensed matter physics and materials science in preparation to enter the scientific/technical workforce of the 21st Century.