Deep donors in Cd1-xZnxTe:Cl

Measurements of the persistent photoconductivity (PPC) and Hall effect in Cl-doped Cd1-xZnxTe indicate that the Cl donors form several distinct deep DX states, consistent with recent calculations. For x = 0.20 only one DX state is evident, with a deep binding energy E(d) = 0.22 eV; the PPC has a single annealing transition at T-a = 130 K. For x = 0.18 the PPC has two distinct transitions, at T-b = 100 K and T-a = 190 K. We propose a model in which the presence of a second metastable state DX' boosts T-a significantly. For x = 0.28 the DX' lies 0.23 eV below the conduction band, whereas the deepest binding energy is E(d) = 0.40 eV. The rapid increase of E(d) with x explains the difficult of obtaining n-type ZnTe using Cl dopants. Nevertheless, these materials are interesting because DX centers with large E(d) and high T-a are potentially useful in optoelectronic application.