Investigation of Light-Induced Degradation in Ga- and In-Doped Cz Silicon

Light-induced degradation (LID) in boron (B)- doped Czochralski (Cz)-grown wafers has been shown to be a critical problem in cells made from this material. Thus, gallium (Ga)-doped [and to a lesser extent, indium (In)-doped] Cz wafers have been considered as an alternative for photovoltaic applications. However, previous investigations regarding the impact of LID in these materials are not definitive. In this study, we investigate LID in both Ga- and In-doped Cz wafers where we observe significant degradation in both materials. It seems that the degradation in Ga-doped wafers has two stages, while only one stage is detected in In-doped wafers. We determine the activation energies of the defect formation to be 0.94±0.12 eV (B), 0.74±0.10 eV (Ga), and 0.91±0.15 eV (In), suggesting that the degradation rate is highly temperature-dependent in the In-doped wafers, while the defect formation in Ga-doped wafers is less affected by temperature compared to B-doped wafers. Finally, using temperature- and injection-dependent lifetime measurements, we determine the energy level and the symmetry factor of the defect causing LID in Ga-doped wafers and compare them to the reported values for well-known defects with similar energy levels or symmetry factors.