Influence of carbon atoms in single crystal Si on electron trap generation due to UV light irradiation during RPD process

The recombination-active defects in crystalline silicon are generated during the solar cell fabrication by the ultraviolet light in the reactive plasma deposition (RPD) process, which degrades carrier lifetime and limits the performance of high-efficiency solar cells. Although previous studies have linked these defects to oxygen-related complexes, the possible influence of carbon impurities remains unclear. In this study, the correlation between the bulk carbon (C) concentration and the RPD-induced defect formation in Czochralski-grown single-crystal silicon was systematically investigated using deep-level transient spectroscopy (DLTS). Silicon wafers with C concentrations ranging from 1.3 × 1014 to 6.0 × 1016 cm−3 and with nearly constant oxygen content (∼1.8 × 1018–2.0 × 1018 cm−3) were processed under identical RPD conditions. DLTS revealed three distinct electron traps (E1, E2, and E3) located within ∼200 nm from the SiO2/Si interface. Their energy levels, capture cross sections, and concentrations were nearly invariant across the C range. The results indicated that the recombination centers created by the RPD process are very likely related to oxygen-related species, i.e., O–Si divacancies, based on the parameter values determined. This work refines the understanding of plasma-induced defect mechanisms and supports optimized RPD processing for reliable, high-efficiency carrier-selective contact (CSC) solar cells.