Study of Light-Induced Changes in the Optoelectronic Quality of Ga-Doped Silicon Wafers
DOI:
https://doi.org/10.52825/siliconpv.v4i.3452Keywords:
Light-Induced Degradation (LID), Light and Elevated Temperature Induced Degradation (LeTID), Metastable Defects, Czochralski p-type Silicon, Ga-Doped SiliconAbstract
Light-induced degradation (LID) of boron-doped (B-doped) Czochralski silicon (Cz-Si) due to the formation of boron-oxygen (B-O) defects is a very well-known phenomenon that limits the stability of solar cells. To overcome the detrimental effects of B-O defects, the silicon industry has adopted gallium-doped wafers. However, it has been reported that Ga-doped Cz-Si-based solar cells are affected by light and elevated temperature induced degradation (LeTID), and the origin of this phenomenon at wafer level remains unclear. In this work we investigate light-induced changes in Ga-doped p-type Cz-Si wafers of different resistivities and compare them to the well-known degradation response of B-doped substrates. Through controlled illumination–temperature experiments and photoconductance-based carrier lifetime measurements, we analyse the evolution of minority carrier lifetime and the metastable nature of the lifetime-limiting defects. It was found that upon light-soaking at room temperature for 24 hours, Ga-doped wafers exhibit an average increment in the carrier lifetime, but a drop is observed under dark annealing at 200 ºC for 10 min. This behavior, which has an opposite dynamic to the traditional B-O activation/deactivation process in B-doped wafers, might suggest the existence of a metastable defect in Ga-doped samples. By applying a higher temperature during the light-soaking step, the average carrier lifetime values of Ga-doped samples decrease around 30%, and no recovery is observed under dark annealing conditions at 70 or 200 ºC. Moreover, our results of cyclability suggest that the defects dynamic in Ga-doped Cz-Si is not reversible. The results provide new insights into the mechanisms governing stability in Ga-doped silicon at bare wafer level and their implications for reliable, high-efficiency solar cell manufacturing.
Downloads
References
[1] J. Schmidt, A. G. Aberle, and R. Hezel, "Investigation of carrier lifetime instabilities in Cz-grown silicon," in Conf. Rec. 26th IEEE Photovolt. Spec. Conf. (PVSC), Anaheim, CA, USA, 1997, pp. 13–18, doi: https://doi.org/10.1109/PVSC.1997.
[2] J. Schmidt and K. Bothe, "Structure and transformation of the metastable boron- and oxygen-related defect center in crystalline silicon," Phys. Rev. B, vol. 69, Art. no. 024107, Jan. 2004, doi: https://doi.org/10.1103/PhysRevB.69.024107.
[3] K. Bothe, R. Sinton, and J. Schmidt, "Fundamental boron–oxygen-related carrier lifetime limit in mono- and multicrystalline silicon," Prog. Photovolt.: Res. Appl., vol. 13, no. 4, pp. 287–296, Jun. 2005, doi: https://doi.org/10.1002/pip.586.
[4] C. Sun, D. Chen, F. Rougieux, R. Basnet, B. Hallam, and D. Macdonald, "Kinetics and dynamics of the regeneration of boron-oxygen defects in compensated n-type silicon," Sol. Energy Mater. Sol. Cells, vol. 195, pp. 174–181, Jul. 2019, doi: https://doi.org/10.1016/j.solmat.2019.03.016.
[5] S. Jafari, Y. Zhu, F. Rougieux, J. A. T. De Guzman, V. P. Markevich, A. R. Peaker, and Z. Hameiri, "Boron-oxygen related light-induced degradation of Si solar cells: Transformation between minority carrier traps and recombination active centers," in Proc. 47th IEEE Photovolt. Spec. Conf. (PVSC), Calgary, AB, Canada, Jun. 2020, pp. 689–692, doi: https://doi.org/10.1109/PVSC45281.2020.9300371.
[6] S. Jafari, M. Figg, and Z. Hameiri, "Investigation of light-induced degradation in gallium- and indium-doped Czochralski silicon," Sol. Energy Mater. Sol. Cells, vol. 251, Art. no. 112121, Feb. 2023, doi: https://doi.org/10.1016/j.solmat.2022.112121.
[7] K. Ramspeck, S. Zimmermann, H. Nagel, A. Metz, Y. Gassenbauer, B. Birkmann, and A. Seidl, "Light induced degradation of rear passivated mc-Si solar cells," in Proc. 27th Eur. Photovolt. Sol. Energy Conf. Exhib., Frankfurt, Germany, Sep. 2012, pp. 861–865, doi: https://doi.org/10.4229/27thEUPVSEC2012-2DO.3.4.
[8] M. Winter, D. C. Walter, and J. Schmidt, "Carrier lifetime degradation and regeneration in gallium- and boron-doped monocrystalline silicon materials," IEEE J. Photovolt., vol. 11, no. 4, pp. 866–872, Jul. 2021, doi: https://doi.org/10.1109/JPHOTOV.2021.3070474.
[9] M. Winter, D. C. Walter, B. Min, R. Peibst, R. Brendel, and J. Schmidt, "Light and elevated temperature induced degradation and recovery of gallium-doped Czochralski-silicon solar cells," Sci. Rep., vol. 12, Art. no. 8089, May 2022, doi: https://doi.org/10.1038/s41598-022-11831-3.
[10] K. Fraser, D. Blanc-Pelissier, S. Dubois, J. Veirman, F. Tanay, and M. Lemiti, "A new model for light-induced degradation by B–O defects in p- and n-type silicon," Energy Procedia, vol. 38, pp. 542–550, 2013, doi: https://doi.org/10.1016/j.egypro.2013.07.315.
[11] A. Herguth, G. Schubert, M. Käs, and G. Hahn, "Investigations on the long time behavior of the metastable boron–oxygen complex in crystalline silicon," Prog. Photovolt.: Res. Appl., vol. 16, no. 2, pp. 135–140, Mar. 2008, doi: https://doi.org/10.1002/pip.779.
[12] M. Xie, C. Ren, L. Fu, X. Qiu, X. Yu, and D. Yang, "An industrial solution to light-induced degradation of crystalline silicon solar cells," Front. Energy, vol. 11, no. 1, pp. 67–71, Mar. 2017, doi: https://doi.org/10.1007/s11708-016-0430-x.
[13] S. W. Glunz, S. Rein, J. Knobloch, W. Wettling, and T. Abe, "Comparison of boron- and gallium-doped p-type Czochralski silicon for photovoltaic application," Prog. Photovolt.: Res. Appl., vol. 7, no. 6, pp. 463–469, Nov.–Dec. 1999, doi: https://doi.org/10.1002/(SICI)1099-159X(199911/12)7:6.
[14] C. Chen, H. Yang, J. Wang, J. Lv, and H. Wang, "Investigating the viability of PERC solar cells fabricated on Ga- instead of B-doped monocrystalline silicon wafer," Sol. Energy Mater. Sol. Cells, vol. 227, Art. no. 111134, Jul. 2021, doi: https://doi.org/10.1016/j.solmat.2021.111134.
[15] Z. Hu, L. Yang, T. Zhao, L. Song, A. Hsu, D. He, Y. Cai, H. Yu, D. Yang, and X. Yu, "Higher stability of p-type Ga-doped Czochralski silicon for light and elevated-temperature induced degradation: Insights into Ga-related precursors," Sol. Energy Mater. Sol. Cells, vol. 282, Art. no. 113357, Jan. 2025, doi: https://doi.org/10.1016/j.solmat.2024.113357.
[16] N. E. Grant, P. P. Altermatt, T. Niewelt, R. Post, W. Kwapil, M. C. Schubert, and J. D. Murphy, "Gallium-doped silicon for high-efficiency commercial passivated emitter and rear solar cells," Solar RRL, vol. 5, no. 4, Art. no. 2000754, Apr. 2021, doi: https://doi.org/10.1002/solr.202000754.
[17] J. Horzel, S. Mack, I. Voicu Vulcanean, K. Zimmermann, S. Pingel, W. Kwapil, F. Maischner, H. Höffler, S. Bashardoust, D. Wagenmann, J. Greulich, J. Seif, A. Steinmetz, and J. Rentsch, "High lifetime Ga-doped Cz-Si for carrier-selective junction solar cells," Solar RRL, vol. 7, no. 8, Art. no. 2200613, Apr. 2023, doi: https://doi.org/10.1002/solr.202200613.
[18] F. Kersten, P. Engelhart, H.-C. Ploigt, A. Stekolnikov, T. Lindner, F. Stenzel, M. Bartzsch, A. Szpeth, K. Petter, J. Heitmann, and J. W. Müller, "Degradation of multicrystalline silicon solar cells and modules after illumination at elevated temperature," Sol. Energy Mater. Sol. Cells, vol. 142, pp. 83–86, Nov. 2015, doi: https://doi.org/10.1016/j.solmat.2015.06.015.
[19] D. Chen, P. Hamer, M. Kim, C. Chan, A. Ciesla, F. Rougieux, Y. Zhang, M. Abbott, and B. Hallam, "Hydrogen-induced degradation: Explaining the mechanism behind light- and elevated temperature-induced degradation in n- and p-type silicon," Sol. Energy Mater. Sol. Cells, vol. 207, Art. no. 110353, Mar. 2020, doi: https://doi.org/10.1016/j.solmat.2019.110353.
[20] W. Kwapil, J. Dalke, R. Post, and T. Niewelt, "Influence of dopant elements on degradation phenomena in B- and Ga-doped Czochralski-grown silicon," Solar RRL, vol. 5, no. 5, Art. no. 2100147, May 2021, doi: https://doi.org/10.1002/solr.202100147.
[21] T. Niewelt, F. Schindler, W. Kwapil, R. Eberle, J. Schön, and M. C. Schubert, "Understanding the light-induced degradation at elevated temperatures: Similarities between multicrystalline and float-zone p-type silicon," Prog. Photovolt.: Res. Appl., vol. 26, no. 8, pp. 533–542, Aug. 2018, doi: https://doi.org/10.1002/pip.2954.
[22] D. Bredemeier, D. Walter, S. Herlufsen, and J. Schmidt, "Lifetime degradation and regeneration in multicrystalline silicon under illumination at elevated temperature," AIP Adv., vol. 6, no. 3, Art. no. 035119, Mar. 2016, doi: https://doi.org/10.1063/1.4944839.
[23] D. Bredemeier, D. Walter, and J. Schmidt, "Light-induced lifetime degradation in high-performance multicrystalline silicon: Detailed kinetics of the defect activation," Sol. Energy Mater. Sol. Cells, vol. 173, pp. 2–5, Dec. 2017, doi: https://doi.org/10.1016/j.solmat.2017.08.007.
[24] D. Bredemeier, D. C. Walter, and J. Schmidt, "Lifetime degradation in multicrystalline silicon under illumination at elevated temperature: Indications for the involvement of hydrogen," in AIP Conf. Proc., vol. 1999, no. 1, Art. no. 130001, Aug. 2018, doi: https://doi.org/10.1063/1.5049320.
[25] T. H. Fung, M. Kim, D. Chen, A. Samadi, C. E. Chan, B. J. Hallam, S. Wenham, and M. Abbott, "Influence of bound hydrogen states on carrier-induced degradation in multi-crystalline silicon," in AIP Conf. Proc., vol. 1999, no. 1, Art. no. 130004, Aug. 2018, doi: https://doi.org/10.1063/1.5049323.
[26] M. A. Jensen, A. Zuschlag, S. Wieghold, D. Skorka, A. E. Morishige, G. Hahn, and T. Buonassisi, "Evaluating root cause: The distinct roles of hydrogen and firing in activating light- and elevated temperature-induced degradation," J. Appl. Phys., vol. 124, no. 8, Art. no. 085701, Aug. 2018, doi: https://doi.org/10.1063/1.5041756.
[27] C. Vargas, K. Kim, G. Coletti, D. Payne, C. Chan, S. Wenham, and Z. Hameiri, "Influence of silicon nitride and its hydrogen content on carrier-induced degradation in multicrystalline silicon," in Proc. 33rd Eur. Photovolt. Sol. Energy Conf. Exhib., Amsterdam, The Netherlands, 2017, pp. 561–564.
[28] U. Varshney, M. Abbott, A. Ciesla, D. Chen, S. Liu, C. Sen, M. Kim, S. Wenham, B. Hoex, and C. Chan, "Evaluating the impact of SiNx thickness on lifetime degradation in silicon," IEEE J. Photovolt., vol. 9, no. 3, pp. 601–607, May 2019, doi: https://doi.org/10.1109/JPHOTOV.2019.2896671.
[29] F. Kersten, J. Heitmann, and J. W. Müller, "Influence of Al₂O₃ and SiNₓ passivation layers on LeTID," Energy Procedia, vol. 92, pp. 828–832, Aug. 2016, doi: https://doi.org/10.1016/j.egypro.2016.07.079.
[30] J. Kamphues, A. Schmid, R. Fischer-Süßlin, G. Hahn, and F. Geml, "Influence of AlOx interlayers on LeTID kinetics in Ga-doped Cz-Si," SiliconPV Conf. Proc., vol. 1, 2024, doi: https://doi.org/10.52825/siliconpv.v1i.842.
Downloads
Published
How to Cite
Conference Proceedings Volume
Section
License
Copyright (c) 2026 Andres Pardo Perdomo, Nerea Dasilva Villanueva, Özlem Coşkun, Usman Ali Shah, Luis Jaime Caballero, Cristian Antoine Ortiz, Nathan Muller, Çağrı Taha Delikanlı, Ece Çamkara, Meriç Çalışkan Arslan, Carlos del Cañizo Nadal, David Fuertes Marrón
This work is licensed under a Creative Commons Attribution 4.0 International License.
Accepted 2026-07-07
Published 2026-09-10
Funding data
-
Clean Energy Transition Partnership
Grant numbers PCI2024-155050-2 -
Ulusal Metroloji Enstitüsü, Türkiye Bilimsel ve Teknolojik Araştirma Kurumu,Türkiye Bilimsel ve Teknolojik Araştırma Kurumu
Grant numbers 224N163