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Micro-spectroscopy on silicon wafers and solar cells.

Gundel P, Schubert MC, Heinz FD, Woehl R, Benick J, Giesecke JA, Suwito D, Warta W - Nanoscale Res Lett (2011)

Bottom Line: This is demonstrated on micro defects in multicrystalline silicon.In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates.With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstr, 2, 79110 Freiburg, Germany. paul.gundel@ise.fraunhofer.de.

ABSTRACT
Micro-Raman (μRS) and micro-photoluminescence spectroscopy (μPLS) are demonstrated as valuable characterization techniques for fundamental research on silicon as well as for technological issues in the photovoltaic production. We measure the quantitative carrier recombination lifetime and the doping density with submicron resolution by μPLS and μRS. μPLS utilizes the carrier diffusion from a point excitation source and μRS the hole density-dependent Fano resonances of the first order Raman peak. This is demonstrated on micro defects in multicrystalline silicon. In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates. This can be attributed to the strong stress dependence of the carrier mobility (piezoresistance) of silicon. With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.

No MeSH data available.


Related in: MedlinePlus

Hole density contrast and stress around a nickel precipitate. The green lines mark the directions of high compressive (negative) stress, which tend to show a lower hole density contrast (recombination activity). In areas of high tensile (positive) stress, the hole density contrast is increased (higher recombination activity).
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Figure 9: Hole density contrast and stress around a nickel precipitate. The green lines mark the directions of high compressive (negative) stress, which tend to show a lower hole density contrast (recombination activity). In areas of high tensile (positive) stress, the hole density contrast is increased (higher recombination activity).

Mentions: Figure 9 shows, that high compressive stress correlates with lower recombination activities along the lines of high compressive stress and that high tensile stress correlates with higher recombination activities. This effect can be explained by the strong piezoresistance of silicon [21]: The carrier flux to the precipitate surface with its high surface recombination velocity [22,23] is proportional to the carrier mobility [24]. This change in mobility increases/reduces the carrier flux for tensile/compressive stress and hence, leads to a high/lower recombination activity in the respective directions. Another origin of the observed correlation between stress and recombination activity could be the formation of dislocations due to stress. However this formation would relax the stress and thus lead to a reduction of the correlation between stress and recombination activity. Details on the impact of stress on the recombination activity and a quantitative analysis can be found in [25,26].


Micro-spectroscopy on silicon wafers and solar cells.

Gundel P, Schubert MC, Heinz FD, Woehl R, Benick J, Giesecke JA, Suwito D, Warta W - Nanoscale Res Lett (2011)

Hole density contrast and stress around a nickel precipitate. The green lines mark the directions of high compressive (negative) stress, which tend to show a lower hole density contrast (recombination activity). In areas of high tensile (positive) stress, the hole density contrast is increased (higher recombination activity).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211253&req=5

Figure 9: Hole density contrast and stress around a nickel precipitate. The green lines mark the directions of high compressive (negative) stress, which tend to show a lower hole density contrast (recombination activity). In areas of high tensile (positive) stress, the hole density contrast is increased (higher recombination activity).
Mentions: Figure 9 shows, that high compressive stress correlates with lower recombination activities along the lines of high compressive stress and that high tensile stress correlates with higher recombination activities. This effect can be explained by the strong piezoresistance of silicon [21]: The carrier flux to the precipitate surface with its high surface recombination velocity [22,23] is proportional to the carrier mobility [24]. This change in mobility increases/reduces the carrier flux for tensile/compressive stress and hence, leads to a high/lower recombination activity in the respective directions. Another origin of the observed correlation between stress and recombination activity could be the formation of dislocations due to stress. However this formation would relax the stress and thus lead to a reduction of the correlation between stress and recombination activity. Details on the impact of stress on the recombination activity and a quantitative analysis can be found in [25,26].

Bottom Line: This is demonstrated on micro defects in multicrystalline silicon.In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates.With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstr, 2, 79110 Freiburg, Germany. paul.gundel@ise.fraunhofer.de.

ABSTRACT
Micro-Raman (μRS) and micro-photoluminescence spectroscopy (μPLS) are demonstrated as valuable characterization techniques for fundamental research on silicon as well as for technological issues in the photovoltaic production. We measure the quantitative carrier recombination lifetime and the doping density with submicron resolution by μPLS and μRS. μPLS utilizes the carrier diffusion from a point excitation source and μRS the hole density-dependent Fano resonances of the first order Raman peak. This is demonstrated on micro defects in multicrystalline silicon. In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates. This can be attributed to the strong stress dependence of the carrier mobility (piezoresistance) of silicon. With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.

No MeSH data available.


Related in: MedlinePlus