Bridgman-grown crystals, doped with Ti, were investigated by using near-infrared optical spectroscopic and electron paramagnetic resonance techniques. In high-resistivity CdTe, Ti centers were detected, by means of electron paramagnetic resonance, in concentrations of about 1016/cm3. At temperatures below 0K, the isotropic spectrum of the Ti2+(3d2) ground state, 3A2(F), was observed. This exhibited high saturation at lower temperatures. At temperatures below 8K, a second spectrum appeared that was due to transitions, within the vibronic 2E ground state of Ti3+(3d1), which were caused by the simultaneous influences of a dynamic Jahn-Teller effect and random strains. Both of these centers exhibited an isotropic hyperfine structure, with 12 equivalent next-nearest Cd neighbors. This proved that the Ti impurity substituted for Cd at lattice sites with Td symmetry. The electron paramagnetic resonance signals were photosensitive in the visible and near-infrared regions. The luminescence spectra of Ti centers in Ti-doped Cd0.85Zn0.15Te reflected a 3T2(F)  3A2(F) transition of Ti2+, that was centered at 2600/cm, and a 2T2(D)  2E(D) emission of Ti3+ around 3200/cm. The excitation spectrum of the Ti2+ luminescence exhibited 3 excitation bands, and near-gap levels.

P.Peka, M.U.Lehr, J.Dziesiaty, S.Müller, J.Kreissl, P.Rudolph, H.J.Schulz: Materials Science Forum, 1994, 143-147, 435-40