CAREER: Low-Temperature Growth of High Crystallinity GeSn on Amorphous Materials for Advanced Optoelectronics

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Technical Description: The research objective of this CAREER project is to grow large-grained and single-crystal GeSn directly on amorphous materials at temperatures below 500 degrees Celsius as a gateway towards advanced optoelectronics on dielectric layers and glass substrates. Growing high crystallinity semiconductor thin films on amorphous substrates has long been a significant challenge in materials science that could break through the limitations of conventional methods such as epitaxy and wafer bonding. In this project, the research team investigates a new approach based on eutectic-mediated growth in Ge-Sn system to achieve high crystallinity GeSn alloy on amorphous substrates at low temperatures. Incorporation of Sn into Ge during the eutectic-mediated growth also transforms Ge towards a direct gap semiconductor with significantly improved optoelectronic properties. Furthermore, nanoscale geometrically-confined nucleation is applied to achieve single-crystal-like GeSn on amorphous layers for high performance optoelectronic devices. The fundamental materials science of related nucleation and growth mechanisms are studied both experimentally by microscopy and diffraction analyses and theoretically via Phase Field modeling. The research also investigates defects in GeSn and methods to reduce and passivate them for optimal optoelectronic properties.Non-technical Description: This project investigates a potentially transformative technology for applications in cost-effective, high-efficiency tandem solar cells as well as three-dimensional photonic circuits on future generations of silicon microchips. The principal investigator (PI) not only integrates the research project with graduate and undergraduate education, but also offers hands-on laboratory experiences related to this research project for 10th-11th grade students. The PI also plans to share interesting educational activities at the level of Scientific American with the general public via YouTube and other public media.