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Influence of Dopant Elements on Degradation Phenomena in B- and Ga-Doped Czochralski-grown Silicon

: Kwapil, W.; Dalke, J.; Post, R.; Niewelt, T.

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Solar RRL 5 (2021), No.5, Art. 2100147, 10 pp.
ISSN: 2367-198X
Journal Article, Electronic Publication
Fraunhofer ISE ()
Photovoltaik; Silicium-Photovoltaik; feedstock; Kristallisation; wafering; Charakterisierung von Prozess- und Silicium-Materialien; Dotierung und Diffusion

The response of lifetime samples made from boron- and gallium-doped Czochralski-grown silicon from the same producer to light- and elevated temperature-induced degradation (LeTID) conditions (varying illumination at 75 °C), to dark anneals (DAs) at 175 °C, and the temporary recovery (TR) reaction under different conditions is investigated. It is found that Ga-doped samples behave very differently than their B-doped counterparts: while the carrier lifetime remains at a high level if an illumination equivalent to 1 sun at 75 °C is applied, strong carrier lifetime degradation occurs at low light intensities. A capture cross-sectional ratio in degraded Ga-doped samples of ~26 is found, which is typical for the LeTID defect. TR of this degraded state is observed on Ga-doped samples when the illumination intensity is increased at 75 °C and when samples are illuminated at 25 °C with intermediate intensity. During DA of B-doped samples, a bulk-related degradation and a subsequent surface-related degradation are observed. In contrast, degradation of Ga-doped samples during DA only occurs on long timescales, and its cause is not clear, yet. It is concluded that the specific dopant species plays an active role both during LeTID and for surface-related degradation-possibly as a result of differences in the acceptor–hydrogen pair properties.