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

Abstract

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 ( J 0 ) analysis. More specifically, in the presence of Cu we observed that J 0 increased from 14 fA/cm 2 to 330 fA/cm 2 in SiO 2 passivated Float Zone (FZ) Si, and from 11 fA/cm 2 to 200 fA/cm 2 in corresponding Czochralski (Cz) Si after illumination under an LED lamp (0.6 Suns, 80 °C). In reference samples without Cu contamination, the J 0 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 (SiN x :H) did not show further increase in J 0 . 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 SiO 2 and SiN x :H passivation. • Surface saturation current density J 0 remained at 10–15 fA/cm 2 in uncontaminated Si. • J 0 increased to 330 fA/cm 2 in FZ Si and to 200 fA/cm 2 in Cz Si during light soaking. • An increase in interfacial defect density was observed in Cu-contaminated samples.