Electronically activated boron-oxygen-related recombination centers in crystalline silicon

Two different boron- and oxygen-related recombination centers are found to be activated in crystalline silicon under illumination or electron injection in the dark, both leading to a severe degradation in the carrier lifetime. While one center forms on a time scale of seconds to minutes, the formation of the second center typically proceeds within hours. In order to reveal the electronic and microscopic properties of both defect centers as well as their formation and annihilation kinetics, we perform time-resolved lifetime measurements on silicon wafers and open-circuit voltage measurements on silicon solar cells at various temperatures. Despite the fact that the two centers are found to form independently of each other, their concentrations exhibit the same linear dependence on the substitutional boron (B-s) and quadratic dependence on the interstitial oxygen (O-i) content. Our results suggest that the fast- and the slowly forming recombination centers correspond to two different configurations of a BsO2i complex.