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Chemical etching to dissolve dislocation cores in multicrystalline silicon
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Gregori, N. J., Murphy, John D., Sykes, J. M. and Wilshaw, P. R. (2012) Chemical etching to dissolve dislocation cores in multicrystalline silicon. Physica B: Condensed Matter, Vol.407 (No.15). pp. 2970-2973. doi:10.1016/j.physb.2011.07.049 ISSN 0921-4526.
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Official URL: http://dx.doi.org/10.1016/j.physb.2011.07.049
Abstract
Multicrystalline silicon wafers are used for approximately half of all solar cells produced at present. These wafers typically have dislocation densities of up to ∼106 cm−2. Dislocations and associated impurities act as strong recombination centres for electron–hole pairs and are one of the major limiting factors in multicrystalline silicon substrate performance. In this work we have explored the possibility of using chemical methods to etch out the cores of dislocations from mc-Si wafers. We aim to maximise the aspect ratio of the depth of the etched structure to its diameter. We first investigate the Secco etch (1K2Cr2O7 (0.15 M): 2HF (49%)) as a function of time and temperature. This etch removes material from dislocation cores much faster than grain boundaries or the bulk, and produces tubular holes at dislocations. Aspect ratios of up to ∼7:1 are achieved for ∼15 μm deep tubes. The aspect ratio decreases with tube depth and for ∼40 μm deep tubes is just ∼2:1, which is not suitable for use in bulk multicrystalline silicon photovoltaics. We have also investigated a range of etches based on weaker oxidising agents. An etch comprising 1I2 (0.01 M): 2HF (49%) attacked dislocation cores, but its etching behaviour was extremely slow (<0.1 μm/h) and the pits produced had a low aspect ratio (<2:1).
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Engineering > Engineering | ||||
Journal or Publication Title: | Physica B: Condensed Matter | ||||
Publisher: | Elsevier BV | ||||
ISSN: | 0921-4526 | ||||
Official Date: | 2012 | ||||
Dates: |
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Volume: | Vol.407 | ||||
Number: | No.15 | ||||
Page Range: | pp. 2970-2973 | ||||
DOI: | 10.1016/j.physb.2011.07.049 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access |
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