Dominant radiation-induced defects in space solar cell silicon manifested by photoluminescence spectroscopy

We have investigated radiation-induced defects in B-doped Si crystals used for space solar cells by photoluminescence (PL) spectroscopy. Two deep-level PL lines dominate the emission spectra in the crystals irradiated with 1 MeV electrons: One is the 0.79 eV line known as the C-line associated with the interstitial defects consisting of C and O (C i -O i ), and the other is a new line at 0.87 eV. The origin of the 0.87 eV line is identified as the B i -O i defect from the analyses of the spectral shape, the temperature dependence, and the thermal stability. The C i -O i defect decreases with the B concentration while that of the B i -O i defect increases. We believe that the dominant radiation-induced defects are B i -O i in low resistivity samples (p 0.1 Ω.cm), B i -O i and C i -O i in medium resistivity samples (0. 1 p 2 Ω.cm), and C i -O i in high resistivity samples (p 2 Ω.cm).