Native Defects and Impurities in Zinc Oxide Studied with Optical and Magnetic Resonance Techniques

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Technical. This project makes use of a variety of optical and magnetic resonance techniques to determine fundamental behavior of atomic-scale defects in two wide-band-gap semiconducting materials, zinc oxide (ZnO) and aluminum nitride (AlN). Five specific research areas are tar-geted, four in ZnO and one in AlN. In ZnO, these include the trapping of hydrogen in oxygen va-cancies, the release of hidden hydrogen, the formation of defect complexes involving Zn vacan-cies, and the wavelength dependences of photoinduced changes in charge state. In AlN, the pri-mary donors, acceptors, and their simpler complexes will be identified and characterized. The proposed investigations in ZnO and AlN emphasize the use of EPR/ENDOR techniques to iden-tify models of specific defect complexes. At the same time, correlations with optical absorptions and emissions will be established. Sample modifications will include high-temperature anneals and electron irradiations. Magnetic resonance, optical, and electrical characterization tools will be employed; magnetic resonance techniques include electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and solid-state nuclear magnetic resonance (NMR). Optical techniques include photoluminescence (PL), photoluminescence excitation (PLE), Raman, and absorption. Temperature-dependent Hall effect measurements will provide electrical information. Non-Technical. The project addresses fundamental research issues in a topical area of elec-tronic/photonic materials science having technological relevance. This project includes graduate and undergraduate student mentoring, visits to non-PhD institutions in the region where the co-PIs will present talks, and the integration of wide-band-gap semiconductor-based research exam-ples (including demonstrations) into the materials physics courses at West Virginia University. Students will gain valuable experience in a wide variety of advanced spectroscopic materials characterization techniques. These students are also provided opportunities, through project col-laborators, to work with scientists at both government labs and other universities. Such interac-tions will ensure a practical applications-oriented side to our fundamental studies. On a broader scale, an increased understanding in the fundamental defect properties of these semiconductors may have significant societal impacts: improved light emitters in the ultraviolet and visible spec-tral regions, more efficient and cost-effective solid-state lighting, improved gas sensors, im-proved scintillators for portable nuclear detectors, photocatalysis of hydrogen, and emerging ar-eas--magnetic semiconductors and spintronics.