DX centers and persistent photoconductivity in CdTe–In films

In this work, we study the nature and behavior of the persistent photoconductivity (PPC) in CdTe–In films grown by co-sputtering of CdTe–In–Cd targets. It was found that only when In atoms are substantially incorporated into CdTe films, the persistent photoconductivity is observed with a quenching temperature of about 270 K. We have also investigated the trapping centers in the CdTe films by using the thermally stimulated conductivity technique. Two localized deep levels were determined. One of them, with an activation energy of 0.42 eV, has been ascribed as a direct evidence of DX centers that are formed by Cd vacancies and In donors complexes. By formulating the PPC build-up and decay kinetics, we have associated the PPC effect in our films to the photoionization of this deep level (DX like centers). Up to date, the existence of DX centers in CdTe–In polycrystalline films have not been previously reported.