Investigation of the defect structure in Cd1−xZnxTe by positron lifetime spectroscopy

Positron lifetime spectroscopy has been employed to explore grown-in defects in Cd1−xZnxTe (CZT) as a function of increasing Zn content. We find that with the increase of Zn content, both the average positron lifetime τAvg, and the lifetime in the bulk τBulk, change smoothly from values typical for CdTe to those for ZnTe. In all samples, a defect-related lifetime component, τD could be resolved with values decreasing from 347ps in CdTe to 333ps in ZnTe. This lifetime component is attributed to neutral Na(Cd,Zn)-VTe complexes in concentrations of around 1016cm−3, with a transition energy level below 0.19eV above the valence band. It is established that these complexes are not connected to the p-type conductivity and their general characteristics are independent of the Zn content. This picture holds for stoichiometrically grown CZT and is independent of the growth method, whereas growth under Cd-rich conditions introduces a neutral impurity-VTe complex with higher concentrations as compared to growth from stoichiometric conditions.