FRG: Tailoring the Properties of Dilute Nitride Semiconductor Alloys

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Technical: This project explores the relationship between indium composition (and lattice parameter) and the energy bandgap for InGaAsN alloys. The collaborative experimental and theoretical approach aims to understand and control the atomic to nanometer-scale structure of dilute nitride semiconductor alloys, in order to tailor the properties of heterostructures for a variety of applications. The project is interdisciplinary integrating expertise in materials science, physics, and electrical engineering; experimentalists at the U-Michigan and the U-Notre Dame and theorists at Ucollege in Cork, Ireland will strive for greater understanding of microstructure and properties of dilute nitride semiconductor heterostructures. To this end, the precise synthesis conditions needed to manipulate the microstructure and consequent electronic states and optical emission efficiencies of these alloys will be identified. Dilute nitride alloy films will be synthesized using plasma-assisted molecular-beam epitaxy. The microstructure will be tailored using a novel approach to seed compositional patterns using pregrowth In- and Ga- focused-ion-beam implantation. The atomic-to-nanometer-scale structure will be characterized using in-situ scanning tunneling microscopy (STM), as well as cross-sectional STM and transmission electron microscopy, high-resolution x-ray diffraction, and nuclear reaction analysis. Elastic properties will be determined with real-time measurements of wafer curvature during growth, and nearfield Raman spectroscopy following growth. The electronic states will be examined using scanning tunneling spectroscopy, near-field piezorelectivity, and resistivity and Hall measurements, in conventional and gated configurations. Optical properties will be determined using absorption and photoluminescence, magneto-luminescence, and near-field scanning optical microscopy. All of these results will be interpreted using a complementary set of computational studies, including density functional theory and tight-binding calculations to interpret STM images and determine the effects of N clustering on elastic properties; as well as continuum and effective-mass based calculations of the effects of N clusters on the electron mobility and optical properties. The work accomplished in this project will lay the foundation for a larger effort to develop novel electronic, optoelectronic, and photovoltaic devices.Non-Technical: The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new understanding and capabilities in electronic devices. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The approach is interdisciplinary integrating expertise in materials science, physics, and electrical engineering, bringing together experimentalists at the U-Michigan and the U-Notre Dame and theorists at U-College in Cork, Ireland. This creates unique education and training opportunities for graduate, undergraduate, and high school students working together as part of a team effort in forefront electronic materials research. The project includes (a) the creation of a multi-disciplinary scientific learning environment for students at a variety of levels (from K12 to graduate) and from several underrepresented groups (including women, African-Americans, and Latinos), and (b) the creation of new knowledge expected to enable new technologies that will benefit society.