OPTICAL SPECTROSCOPY OF TITANIUM-DOPED CDZNTE

The energy level diagram of titanium in CdZnTe grown by the vertical B ridgman method has been investigated by using a variety of optical spe ctroscopy techniques: photoluminescence (PL), PL excitation (PLE) and deep level optical spectroscopy (DLOS). By PL spectroscopy, a broad em ission band around 0.8 eV, with a double-peaked shape, is reported for the first time. PL and PLE results, combined with the DLOS data of th e E-c --> 0.83 eV titanium-related electron trap lead us to (i) attrib ute the 0.8 eV emission band to the T-1(2)(D-1), (3)A(2)(F-3) internal transition of the Ti2+ single donor and (ii) demonstrate that the T-3 (1)(P-3) state is split by the combined action of spin-orbit coupling and a strong dynamic Jahn-Teller effect. The double-peaked shape of th e 0.8 eV emission band is interpreted as a combination of two recombin ation processes involving Ti2+. A configuration coordinate diagram of Ti2+ ions is proposed. Finally the F centre (V-Te) has been identified in CdZnTe:Ti by FL; the threshold ionization energy of this centre is determined by PLE at 1.441 eV.