Synergistic experimental and theoretical studies of the growth and characterization of near-single crystal semiconductors on glass

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AbstractTechnical: This project aims at the fundamental study of the growth of near-single crystal Ge on non-crystalline substrates such as glass. A glass substrate does not have a well ordered atomic lattice and therefore cannot induce the growth of epitaxial semiconductors. A key challenge is whether it is possible to grow a single crystal film on glass at all. In this project it is proposed to use a biaxial CaF2 buffer layer on glass to induce an epitaxial growth of near-single crystal Ge films. The biaxial CaF2 layer, which possesses strong out-of-plane and in-plane texture orientations, will be grown using an oblique angle deposition technique. The aims of the proposed research are to (a) understand the fundamental mechanism of the heteroepitaxial growth of near-single crystal Ge films on biaxial CaF2 buffer layer, and (b) to characterize the structural defects and electronic properties of the epitaxial Ge films, and (c) to understand the fundamental nature of the defects in the Ge films, in particular, the small angle grain boundaries, using classical and quantum mechanical atomistic methods. The expectation is that these near-single crystal Ge films may possess superior device quality properties compared to those polycrystalline films fabricated by conventional means on glass where the grains are randomly oriented. The strategy proposed in this research is robust and may stimulate more study on the growth of other semiconductors on amorphous substrates.Nontechnical: To date, high performance semiconductor devices are made out of single crystal semiconductor films grown on single crystal substrates. However, single crystal substrates are too expensive for large area applications such as display and solar cells. Most low-cost commercial large area devices are made of either polycrystalline or amorphous semiconductors on glass or metal substrates with less than ideal efficiency and long term stability problems. In this project the PIs are aiming to create a near-single crystal semiconductor films such as Ge grown on glass. The knowledge gained from this study can aid researchers to design and functionalize textures to obtain the desirable physical properties of thin films. It is projected that these near-single crystal semiconductor films should possess substantially better performance than that of the films deposited by conventional means on glass for large area electronics applications. This interdisciplinary work, research will be integrated with education and outreach activities. In addition to training graduate students, students supported through the NSF-REU and Rensselaer-sponsored URP (Undergraduate Research Participation) programs will also participate in the research. Outreach activities will include open houses and summer programs on campus for high school juniors/seniors. These efforts will enhance and stimulate students' interest in pursuing science or engineering careers.