Analysis of charge-transfer and charge-conserving optical transitions at vanadium ions in CdTe

In addition to the V3+ features earlier identified, photoluminescence (PL) excitation and sensitization spectra support the assignment of infrared PL bands to internal transitions of V+ and V2+ in vanadium-doped CdTe. The mea sured decay time constants of the PL bands conform to the electric-dipole s election rules. Crystal-field calculations applying a Tanabe-Sugano scheme support the assignment of excited stares. In addition to the charge-conserv ing transitions of vanadium ions in their various oxidation states, charge- transfer transitions are present in the spectra. A comparative analysis of intrinsic defect levels reveals that they are not involved in the experimen tal spectra. From the excitation and sensitization spectra, the positions o f the V2+/V3+ donor (E-CB - 7550 cm(-1)) acid V2+/V+ acceptor (E-CB - 4800 cm(-1)) levels in CdTe are determined.