Comprehensive Microscopic Analysis of Laser-Induced High Doping Regions in Silicon

Gundel, Paul; Suwito, Dominik; Jäger, Ulrich; Heinz, Friedemann D.; Warta, Wilhelm; Schubert, Martin C.

doi:10.1109/ted.2011.2158649

Cited by 18 publications

(18 citation statements)

References 21 publications

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“…In recent years, with the advent of micro‐photoluminescence spectroscopy (μ‐PLS) tools, equipped with confocal optics, microstructures in Si wafers and solar cells can be investigated with very high spatial resolution, enabling the study of dislocation clusters, grain boundaries, metal and oxide precipitates, and locally laser‐doped regions . Currently, there are several μ‐PLS‐based methods to assess doping densities of heavily‐doped layers in c‐Si wafers and solar cells, proposed by different authors . Woehl et al and Gundel et al applied μ‐PLS measurements at room temperature on carefully cross‐sectioned and polished solar cell precursors to reveal the depth profile of heavily‐doped regions, based on the shift of the photoluminescence (PL) peak caused by bandgap narrowing.…”

Section: Introductionmentioning

confidence: 99%

Quantification of Sheet Resistance in Boron‐Diffused Silicon Using Micro‐Photoluminescence Spectroscopy at Room Temperature

et al. 2017

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A micro‐photoluminescence‐based technique is presented, to quantify and map sheet resistances of boron‐diffused layers in silicon solar cell precursors with micron‐scale spatial resolution at room temperature. The technique utilizes bandgap narrowing effects in the heavily‐doped layers, yielding a broader photoluminescence spectrum at the long‐wavelength side compared to the spectrum emitted from lightly doped silicon. By choosing an appropriate spectral range as a metric to assess the doping density, the impacts of photon reabsorption on the analysis can be avoided; thus, an accurate characterization of the sheet resistance can be made. This metric is demonstrated to be better representative of the sheet resistance than the surface doping density or the total dopant concentration of the diffused layer. The technique is applied to quantify sheet resistances of 12‐μm‐wide diffused fingers in interdigitated back‐contact solar cell precursors and large diffused areas. The results are confirmed by both 4‐point probe and time‐of‐flight secondary‐ion mass spectrometry measurements. Finally, the practical limitations associated with extending the proposed technique into an imaging mode are presented and explained.

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Section: Introductionmentioning

confidence: 99%

Quantification of Sheet Resistance in Boron‐Diffused Silicon Using Micro‐Photoluminescence Spectroscopy at Room Temperature

et al. 2017

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“…This fact has been demonstrated by the detection of dislocations [7] and certain levels of mechanical stress [8], [9] in the regions processed by laser. In addition to these micro-structural studies, other analysis such as the study of the composition [10], the estimation of the doping level [8], [9], and the study of the electronic properties [11], [12] of LPRs have been also carried out in the last years. Most of these investigations are exclusively focused on the study of the features and properties of the locally molten material volume, however, no detailed analyses at the surrounding area of LPRs have been performed up to now.…”

Section: Introductionmentioning

confidence: 91%

Microscale Characterization of Surface Recombination at the Vicinity of Laser-Processed Regions in c-Si Solar Cells

Roigé

Ossó

Martı́n

et al. 2016

IEEE J. Photovoltaics

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Laser firing processes have emerged as a technologically feasible approach to fabricate local point contacts or local doped regions in advanced high-efficiency crystalline-Si (c-Si) solar cells. In this work we analyze the local impact induced by the laser pulse on the passivation layers, which are commonly present in advanced c-Si solar cell architectures to reduce surface recombination. We use micro-photoluminescence (PL) measurements with a spatial resolution of 7 µm to evaluate the passivation performance at the surroundings of laser processed regions (LPRs). In particular, we have studied LPRs performed on SiCx/Al2O3-and Al2O3-passivated c-Si wafers by an IR (1064 nm) laser. Micro-PL results show that passivation quality of c-Si surface is affected up to about 100 µm away from the LPR border, and that the extension of this damaged zone is correlated to the laser power and to the presence of capping layers. In the final part of the work, the observed decrease in passivation quality is included into an improved 3D simulation model that gives accurate information about the recombination velocities associated to the studied LPRs.

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“…Some works have already reported methods for quantifying doping densities in Si via room-temperature PL studies. 11,24 In these studies, the recorded PL spectra are fitted in order to obtain the reduced band gap energy E g , which then is correlated with the corresponding doping level. Despite the fact that this methodology can be applied to room-temperature measurements, it is more precise for cryogenic temperature studies where the contribution of phonon energies to indirect radiative transitions is much lower and then the resulting narrower PL lines can be more precisely fitted.…”

Section: B Doping Density Quantification Via Micro-pl Spectroscopymentioning

confidence: 99%

“…5 for quantifying the doping density of a laser doped region (LPR). Gundel et al 11 have already employed confocal PL measurements to quantify doping densities in cross-sections of laserprocessed point contacts. The PL analysis of the LPR presented here was performed using the two same objectives and experimental configuration employed to obtain the calibration curves presented above.…”

Section: B Doping Density Quantification Via Micro-pl Spectroscopymentioning

confidence: 99%

“…8 Confocal micro-PL spectroscopy has become during the last few years an important experimental tool for developing novel and comprehensive studies of advanced solar cell concepts 9 with micron resolution. In particular, micro-PL measurements have been extensively used to perform highresolution spatially resolved studies of different properties and material features, including the analysis of microstructural defects, 10 the estimation of doping densities, 11,12 and the detection of precipitates and impurities. 13 In confocal micro-PL measurements, a laser light is focused onto the surface of the sample to be studied by microscope objectives, and the backscattered PL signal is collected via a confocal aperture.…”

Section: Introductionmentioning

confidence: 99%

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Effects of photon reabsorption phenomena in confocal micro-photoluminescence measurements in crystalline silicon

Roigé

Alvarez

Jaffré

et al. 2017

Journal of Applied Physics

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Confocal micro-photoluminescence (PL) spectroscopy has become a powerful characterization technique for studying novel photovoltaic (PV) materials and structures at the micrometer level. In this work, we present a comprehensive study about the effects and implications of photon reabsorption phenomena on confocal micro-PL measurements in crystalline silicon (c-Si), the workhorse material of the PV industry. First, supported by theoretical calculations, we show that the level of reabsorption is intrinsically linked to the selected experimental parameters, i.e., focusing lens, pinhole aperture, and excitation wavelength, as they define the spatial extension of the confocal detection volume, and therefore, the effective photon traveling distance before collection. Second, we also show that certain sample properties such as the reflectance and/or the surface recombination velocity can also have a relevant impact on reabsorption. Due to the direct relationship between the reabsorption level and the spectral line shape of the resulting PL emission signal, reabsorption phenomena play a paramount role in certain types of micro-PL measurements. This is demonstrated by means of two practical and current examples studied using confocal PL, namely, the estimation of doping densities in c-Si and the study of back-surface and/or back-contacted Si devices such as interdigitated back contact solar cells, where reabsorption processes should be taken into account for the proper interpretation and quantification of the obtained PL data. Published by AIP Publishing.

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Comprehensive Microscopic Analysis of Laser-Induced High Doping Regions in Silicon

Cited by 18 publications

References 21 publications

Quantification of Sheet Resistance in Boron‐Diffused Silicon Using Micro‐Photoluminescence Spectroscopy at Room Temperature

Quantification of Sheet Resistance in Boron‐Diffused Silicon Using Micro‐Photoluminescence Spectroscopy at Room Temperature

Microscale Characterization of Surface Recombination at the Vicinity of Laser-Processed Regions in c-Si Solar Cells

Effects of photon reabsorption phenomena in confocal micro-photoluminescence measurements in crystalline silicon

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