Electron spin resonance study of hydrogenated microcrystalline silicon–germanium alloy thin films |
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| Authors: | CW Chang T Matsui M Kondo |
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| Institution: | 1. Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan;2. Industrial Technology Research Institute, Chu Tung, Hsin Chu 310, Taiwan;3. Tokyo Institute of Technology, Yokohama 226-8503, Japan;1. Colorado Energy Research Institute, Colorado School of Mines, Golden, CO, USA;2. National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, CO, USA;3. Department of Physics and Astronomy, University of Toledo, Toledo, OH, USA;4. Department of Physics, Syracuse University, Syracuse, NY, USA |
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| Abstract: | Paramagnetic defects of undoped hydrogenated microcrystalline silicon–germanium alloys (μc-Si1?xGex:H) grown by low temperature (200 °C) plasma-enhanced chemical vapor desposition (PECVD) have been measured by electron spin resonance (ESR) and compared with those of hydrogenated amorphous silicon–germanium (a-Si1?xGex:H). The spin density of μc-Si1?xGex:H increases with Ge content and shows a broad maximum of ～1017 cm?3 at x ～ 0.5, which reasonably accounts for the decreased photoconductivity. While the Ge dangling bond defects prevail in a-Si1?xGex:H for Ge-rich compositions, we detected no ESR signal in μc-Si1?xGex:H for x > 0.75 where an electrical change occurs from weak n- to strong p-type conduction. These results indicate that dangling bonds are charged in large densities due to the presence of the acceptor-like states in undoped μc-Si1?xGex:H. |
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