Spin-dependent changes in photoconductivity were observed for the first time during the magnetic field-induced crossing of ground singlet (S = 0) and excited triplet (S = 1) state levels of structural defects in irradiated Si. These defects included 2 electrons which were localized on points of trigonal symmetry in the lattice. The results showed that radiation defects with a low exchange energy, comparable to the Zeeman energy, existed between the 2 electrons that were responsible for the S = 1 state. New electron paramagnetic resonance spectra, which corresponded to transitions between Zeeman levels of the excited triplet state of these defects, were detected by means of spin-dependent microwave photoconductivity measurements.

R.Laiho, M.M.Afanasjev, M.P.Vlasenko, L.S.Vlasenko: Physical Review Letters, 1998, 80[7], 1489-92