Electrical defect study in thin-film SiGe/Si solar cells

We have investigated the presence of defects and their role on the efficien cy of thin-him SiGe/Si solar cells. Temperature-dependent I-V, and DLTS mea surements revealed the presence of a main defect that introduces a deep acc eptor level (0/-) near the mid-gap of SiGe, at E-v+0.45 eV. We show that th is level is responsible for the generation-recombination current observed i n our solar cells. We demonstrate that this defect is sensitive to passivat ion and that its concentration reduces with hydrogenation. Finally, we show that this level plays an important role in the determination of the minori ty carrier lifetime in our devices. (C) 2001 Elsevier Science Ltd. All righ ts reserved.