Optimizing phosphorus diffusion for photovoltaic applications: Peak doping, inactive phosphorus, gettering, and contact formation
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Optimizing_phosphorus_diffusion_for_photovoltaic_a.pdf
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Author(s)
Dastgheib-Shirazi, Amir
Min, Byungsul
Steyer, Michael
Hahn, Giso
del Cañizo, Carlos
Altermatt, Pietro P.
Wagner, Hannes
Morishige, Ashley Elizabeth
Buonassisi, Anthony
Date Issued
May 2016
Journal
Journal of Applied Physics
Publisher
American Institute of Physics (AIP)
Citation
Wagner, Hannes et al. “Optimizing Phosphorus Diffusion for Photovoltaic Applications: Peak Doping, Inactive Phosphorus, Gettering, and Contact Formation.” Journal of Applied Physics 119, 18 (May 2016): 185704 © 2016 Author(s)
Version
Final published version
Abstract
The phosphosilicate glass (PSG), fabricated by tube furnace diffusion using a POCl₃ source, is widely used as a dopant source in the manufacturing of crystalline silicon solar cells. Although it has been a widely addressed research topic for a long time, there is still lack of a comprehensive understanding of aspects such as the growth, the chemical composition, possible phosphorus depletion, the resulting in-diffused phosphorus profiles, the gettering behavior in silicon, and finally the metal-contact formation. This paper addresses these different aspects simultaneously to further optimize process conditions for photovoltaic applications. To do so, a wide range of experimental data is used and combined with device and process simulations, leading to a more comprehensive interpretation. The results show that slight changes in the PSG process conditions can produce high-quality emitters. It is predicted that PSG processes at 860 °C for 60 min in combination with an etch-back and laser doping from PSG layer results in high-quality emitters with a peak dopant density N[subscript peak] = 8.0 × 10¹⁸cm⁻³ and a junction depth dj= 0.4 μm, resulting in a sheet resistivity ρ[subscript sh] = 380 Ω/sq and a saturation current-density J₀below 10 fA/cm². With these properties, the POCl₃ process can compete with ion implantation or doped oxide approaches.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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DOI of Published Version
https://doi.org/10.1063/1.4949326
