The present extensive systematic study of defect introduction rates as a function of B, Ga, O and C concentrations by means of deep level transient spectroscopy has drawn a quite complete picture towards the identification of the dominant radiation-induced defects in Si. The radiation-induced defect EV + 0.36eV was identified as Ci–Oi complexes. The absence of an EC - 0.18eV complex center in Ga-doped samples and the linear dependence of its introduction rates on both the B and O content fixed its identification as the Bi–Oi complex in B-doped Si. One of the technologically important results of present study was that the Ga appeared to strongly suppress the radiation-induced defects, especially hole level EV + 0.36eV (Ci–Oi), which was thought to act as a recombination center as well as the dominant compensating center at EC – 0.18eV (Bi–Oi). As a result, the effects of lifetime degradation and carrier removal could be partially offset to higher radiation fluences by using Ga as a dopant instead of B in Si space solar cells. The anneal out of the new hole level EV + 0.18eV in Ga-doped samples at around 350C, together with recovery of free carrier concentration, suggested that this level may act as a donor-like center which compensates free carrier concentration in Ga-doped Si.

Role of the Impurities in Production Rates of Radiation-Induced Defects in Silicon Materials and Solar Cells. A.Khan, M.Yamaguchi, Y.Ohshita, N.Dharmarasu, K.Araki, T.Abe, H.Itoh, T.Ohshima, M.Imaizumi, S.Matsuda: Journal of Applied Physics, 2001, 90[3], 1170-8