Photoluminescence due to boron-related defect in solar cell silicon irradiated with 1 MeV electrons

We investigated a new photoluminescence line at 0.87 eV in B-doped Si irradiated with 1 MeV electrons. We identified its origin as a complex of an interstitial B and an interstitial O (B_i-O_i), one of the major defects responsible for the degradation of space solar cells. The relative intensity of the line increases with the electron fluence and with the B-concentration. The activation energy of the electronic level responsible for the line is estimated to be 0.30 and 0.26 eV from the spectral shape analysis and the temperature dependence, respectively. These values agree with the energy level of the Bi-Oi defect. The agreement of the thermal stability between the line and the Bi-Oi defect also proves the validity of the idea that the 0.87 eV line is due to the B_i-O_i defect