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Proceedings Paper

Characterization of β-FeSi2 films as a novel solar cell semiconductor
Author(s): Yasuhiro Fukuzawa; Teruhisa Ootsuka; Naotaka Otogawa; Hironori Abe; Yasuhiko Nakayama; Yunosuke Makita
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Paper Abstract

β-FeSi2 is an attractive semiconductor owing to its extremely high optical absorption coefficient (α>105 cm-1), and is expected to be an ideal semiconductor as a thin film solar cell. For solar cell use, to prepare high quality β-FeSi2 films holding a desired Fe/Si ratio, we chose two methods; one is a molecular beam epitaxy (MBE) method in which Fe and Si were evaporated by using normal Knudsen cells, and occasionally by e-gun for Si. Another one is the facing-target sputtering (FTS) method in which deposition of β-FeSi2 films is made on Si substrate that is placed out of gas plasma cloud. In both methods to obtain β-FeSi2 films with a tuned Fe/Si ratio, Fe/Si super lattice was fabricated by varying Fe and Si deposition thickness. Results showed significant in- and out-diffusion of host Fe and Si atoms at the interface of Si substrates into β-FeSi2 layers. It was experimentally demonstrated that this diffusion can be suppressed by the formation of template layer between the epitaxial β-FeSi2 layer and the substrate. The template layer was prepared by reactive deposition epitaxy (RDE) method. By fixing the Fe/Si ratio as precisely as possible at 1/2, systematic doping experiments of acceptor (Ga and B) and donor (As) impurities into β-FeSi2 were carried out. Systematical changes of electron and hole carrier concentration in these samples along variation of incorporated impurities were observed through Hall effect measurements. Residual carrier concentrations can be ascribed to not only the remaining undesired impurities contained in source materials but also to a variety of point defects mainly produced by the uncontrolled stoichiometry. A preliminary structure of n-β-FeSi2/p-Si used as a solar cell indicated a conversion efficiency of 3.7%.

Paper Details

Date Published: 12 May 2006
PDF: 10 pages
Proc. SPIE 6197, Photonics for Solar Energy Systems, 61970N (12 May 2006); doi: 10.1117/12.663892
Show Author Affiliations
Yasuhiro Fukuzawa, Kankyo Semiconductors Co., Ltd. (Japan)
Teruhisa Ootsuka, Tateyama Kagaku Co., Ltd. (Japan)
Naotaka Otogawa, Kankyo Semiconductors Co., Ltd. (Japan)
Hironori Abe, Tateyama Kagaku Co., Ltd. (Japan)
Yasuhiko Nakayama, Kankyo Semiconductors Co., Ltd. (Japan)
Yunosuke Makita, Kankyo Semiconductors Co., Ltd. (Japan)
Tateyama Kagaku Co., Ltd. (Japan)

Published in SPIE Proceedings Vol. 6197:
Photonics for Solar Energy Systems
Andreas Gombert, Editor(s)

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