Increased surface recombination in crystalline silicon under light soaking due to Cu contamination

Light-induced degradation (LID) can occur in crystalline silicon (Si) due to increased recombination in the bulk or at the surfaces. As an example, copper (Cu) is a contaminant that reportedly causes LID in the bulk of Si under illumination. In this article, we show that Cu contamination can also increase recombination at the surface under illumination using surface saturation current density (J0) analysis. More specifically, in the presence of Cu we observed that J0 increased from 14 fA/cm2 to 330 fA/cm2 in SiO2 passivated Float Zone (FZ) Si, and from 11 fA/cm2 to 200 fA/cm2 in corresponding Czochralski (Cz) Si after illumination under an LED lamp (0.6 Suns, 80 °C). In reference samples without Cu contamination, the J0 was unaffected. These results demonstrate that a significant increase in surface recombination is possible without the presence of hydrogen. Furthermore, hydrogen was not seen to affect the Cu-induced surface degradation as similar experiments made with hydrogenated silicon nitride (SiNx:H) did not show further increase in J0. However, the timescale of the observed degradation was relatively fast (hours) indicating that Cu-induced surface degradation is a separate phenomenon from the earlier reported surface-related degradation. •Cu contamination leads to increased surface recombination in Si under light soaking.•The phenomenon occurs in FZ and Cz Si with both SiO2 and SiNx:H passivation.•Surface saturation current density J0 remained at 10–15 fA/cm2 in uncontaminated Si.•J0 increased to 330 fA/cm2 in FZ Si and to 200 fA/cm2 in Cz Si during light soaking.•An increase in interfacial defect density was observed in Cu-contaminated samples.