| 研究実績の概要 |
Thin SiNW solar cells fabricated by using pre-chemical etch and post-mechanical polish for proving low Si material consumption and developing into the flexible devices were continued to study from the last fiscal year for the photovoltaic applications. With the SiNW formation on these thin wafers, the vertical Al-catalyzed SiNWs were better controlled on post-polished Si substrate and the higher NW density and smaller NW diameter were also observed. The light reflectance of both SiNWs could reduce to lower than 20%. The power conversion efficiencies of thin SiNW solar cells were achieved upon 5.0%. The p-Si/i-Ge core-shell NW structures were studied for NW transistor applications. The hole gas accumulation in the i-Ge shell region induced by unintentional Al-doped p-Si core was observed. The thin B-doped Si intermediate layer in the p-Si/p-Si/i-Ge core-double shell NW and B doping in the p-Si shell outermost layer of the p-Si/i-Ge/p-Si core-double shell NW structures with various B concentrations were successfully improved the hole gas generation. The asymmetrical broadening (the Fano effect) confirmed the induced hole gas accumulation in the i-Ge shell region induced by Al-doped p-SiNW core and an additional B-doped Si thin intermediate layer or the p-Si outermost shell. All Si optical phonon peaks showed a larger downshift from the value of bulk Si, corresponding to the impurity doping of Al in p-SiNW core and increase B in the thin Si intermediate layer or the p-Si outermost shell. All experimental results of this year were presented in 7 conferences.
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