Dept. of Electrical & Computer Engineering, Institute for Materials Research, The Ohio State University
Fri, May 11, 2012, 3:30 pm - Fri, May 11, 2012, 5:00 pm
The monolithic integration of high-efficiency III-V compound solar cells with low-cost, robust, and scalable Si substrates has been a driving force in fundamental photovoltaics materials research for decades, due to the potential for a marked increase in performance-to cost ratio. While SiGe has previously been demonstrated as a successful platform for III-V/Si integration, another route that has seen comparatively less attention, but with several significant advantages, exists through the direct integration of III-V materials on Si via nearly lattice-matched GaP. Recent advances in our group, including the development of a heterovalent growth methodology for defect-mitigated heteroepitaxy of GaP on Si, and a semi-transparent GaAsγP1-γ metamorphic buffer/virtual substrate system, have enabled the integration of high-quality III-V materials with low-cost Si substrates. This materials integration scheme thereby provides access to III-V lattice constants ranging between that of GaP and GaAs and direct bandgaps from 1.42 – 2.25 eV, all without the use of potentially problematic Al- and N-containing alloys. These advancements will not only directly enable the achievement of low-cost multijunction III-V/Si solar cells with ideal bandgap profiles that can break the 50% efficiency barrier, but also have the potential to impact a wide range of (opto)electronic applications, from enhanced CMOS to UV/visible photodetectors to green light emitters. Details of the GaP/Si process, and the growth and analysis of metamorphic III-V photovoltaic materials, will be discussed, including early-generation prototype GaAsP solar cells exhibiting great promise for future high-efficiency III-V/Si multijunction photovoltaics.
Tyler Grassman is currently a postdoctoral researcher in the Department of Electrical and Computer Engineering at The Ohio State University. He received his B.A. in Chemistry at the University of Oregon, followed by his M.S. and Ph.D. in Materials Science and Engineering from the Jacobs School of Engineering at the University of California, San Diego. His research interests include the integration of dissimilar materials, the development, growth, and characterization of advanced semiconductor materials, the study of materials surfaces and interfaces, and the use of advanced semiconductor materials for alternative energy production and energy efficiency applications.