Electron paramagnetic resonance experiments on Ti-doped n-type and p-type material were reported. In n-type samples which were co-doped with S, an angular dependent spectrum with trigonal symmetry was observed in addition to the known isolated defects. Analysis suggested that the spectrum was caused by a donor-acceptor nearest-neighbor pair defect [TiGa2+-SP]. The parameters of the spin-Hamiltonian were determined to be: S = 1, g|| = g = 1.95, |D| = 0.0670/cm. The concentration of pair defects confirmed that Coulomb attraction was responsible for its preferential formation. However, no electron paramagnetic resonance pair spectrum could be demonstrated for p-type Ti-doped material which was co-doped with Zn. On the other hand, the existence of such a pair was probable. The absence of an electron paramagnetic resonance spectrum was attributed to spectroscopic causes.

J.Kreissl, W.Ulrici, W.Gehlhoff: Physica Status Solidi B, 1994, 182[2], 471-6