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Lower Temperature Si Thin Films by Metal Induced Growth for Lower Cost Solar Cells

Published online by Cambridge University Press:  31 January 2011

Peter T Mersich
Affiliation:
pmersich@buffalo.edu, University at Buffalo, Electrical Engineering, 332 Bonner Hall, Buffalo, New York, 14150, United States
Wayne A Anderson
Affiliation:
waanders@eng.buffalo.edu, University at Buffalo, Electrical Engineering, Buffalo, New York, United States
Rossman F Giese
Affiliation:
glgclay@buffalo.edu, University at Buffalo, Geology, Buffalo, New York, United States
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Abstract

Metal induced growth (MIG) was used to form epitaxial thin films of microcrystalline Si (μc-Si). By substituting Al as the catalyst metal in place of the usual Ni, x-ray diffraction (XRD) confirmed that μc-Si was successfully grown at temperatures between 350-525°C. At 525°C, a preferred orientation of (220) Si was observed with additional (111) and (311) Si orientations, while a temperature of 350°C resulted in a shift in preferred orientation to (111) Si. The lower limit for Al thickness was found to be between 10-20 nm with little crystallization and a smooth surface observed at 10 nm with XRD and SEM, respectively. Electrical measurements on Schottky diodes revealed space-charge limited conduction (SCLC) with an exponential distribution of trap levels due to diffusion of Al atoms into the Si, which was supported by analysis with energy dispersive x-ray spectroscopy (EDX) near the film surface. By depositing a thin layer of Co on top of Al prior to sputtering, the films exhibited increased crystallinity and a more uniform surface likely due to increased confinement of Al atoms. Electrical measurements demonstrated a shift from SCLC to thermionic emission in resulting Schottky diodes.

Type
Research Article
Copyright
Copyright © Materials Research Society 2010

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