Compensation Mechanism in Vanadium and Gallium Doped CdTe and (Cd,Zn)Te

Vanadium and gallium doped CdTe crystals were grown from the vapour phase (modified Markov method) and (Cd_0.9Zn_0.1)Te: V from the melt (vertical Bridgman). The crystals were characterized by photoinduced current transient spectroscopy (PICTS), photoluminescence (PL) and time dependent charge measurements (TDCM). Transitions from different charge states (V²⁺/V³⁺) of the vanadium donor have been observed in the V-doped crystals by PICTS. A shallow donor level (dE = 0.068 eV) and the Ga A-center have been identified by PICTS and PL measurements in CdTe:Ga. In case of V-doping high resistivity is achieved all over the crystal while Ga-doping results in a high resistivity region only in the middle of the crystal. Calculation of the resistivity by means of a compensation model shows that for both dopants an additional not observed deep donor has to be assumed in order to describe the resistivity distributions.