Compensation effect in undoped polycrystalline CdTe synthesized under nonequilibrium conditions

The compensation effect has been revealed in undoped polycrystalline CdTe synthesized during rapid crystallization. The revealed effect leads to an increase in the electrical resistivity to 10 8 –10 10 Ω cm at a background impurity concentration of ∼1015 cm −3 (Ga Cd and Cl Te donors, unidentified acceptors). For some samples, this effect is accompanied by the appearance of persistent photoconductivity, which disappears at a temperature of ∼200 K. It has been shown that all the polycrystals studied are characterized by a three-level compensation mechanism in which the fundamental properties of the material are determined by deep donors and/or acceptors with a concentration of 10 12 cm −3 . Depending on the specific growth conditions, the electrical resistivity at room temperature is determined by deep centers with activation energies of 0.59 ± 0.10 and 0.71 ± 0.10 eV, which are supposedly related to intrinsic point defects, and deep centers with activation energies of 0.4 ± 0.1 eV, which belong to the DX center formed by the Ga Cd donor.