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Open Access Nano Commentary

Generation of high photocurrent in three-dimensional silicon quantum dot superlattice fabricated by combining bio-template and neutral beam etching for quantum dot solar cells

Makoto Igarashi12, Weiguo Hu12, Mohammad Maksudur Rahman12, Noritaka Usami3 and Seiji Samukawa124*

Author affiliations

1 Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 9808577, Japan

2 Japan Science and Technology Agency, CREST, 5 Sanbancho, Chiyoda, Tokyo 1020075, Japan

3 Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai, 9808577, Japan

4 WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai, 9808577, Japan

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Citation and License

Nanoscale Research Letters 2013, 8:228  doi:10.1186/1556-276X-8-228

Published: 15 May 2013

Abstract

We fabricated a three-dimensional (3D) stacked Si nanodisk (Si-ND) array with a high aspect ratio and uniform size by using our advanced top-down technology consisting of bio-template and neutral beam etching processes. We found from conductive atomic microscope measurements that conductivity became higher as the arrangement was changed from a single Si-ND to two-dimensional (2D) and 3D arrays with the same matrix of SiC, i.e., the coupling of wave functions was changed. Moreover, our theoretical calculations suggested that the formation of minibands enhanced tunneling current, which well supported our experimental results. Further analysis indicated that four or more Si-NDs basically maximized the advantage of minibands in our structure. However, it appeared that differences in miniband widths between 2D and 3D Si-ND arrays did not affect the enhancement of the optical absorption coefficient. Hence, high photocurrent could be observed in our Si-ND array with high photoabsorption and carrier conductivity due to the formation of 3D minibands.

Keywords:
Si nanodisk; Aspect ratio; Photocurrent; Miniband