Effect of features of the technology of polycrystalline CdTe growth on the conductivity and deep level spectrum after annealing

Abstract

The conductivity, morphology, and deep levels in polycrystalline CdTe are studied. Undoped p-CdTe is grown from the vapor phase by low-temperature methods of direct Cd and Te chemical reaction and CdTe vacuum sublimation at Pmin. Chlorine-doped CdTe is also grown. The resistivity of the grown samples is ∼105–109 Ω cm. After annealing in liquid cadmium or in cadmium vapor at ∼500°C, the conductivity type changes, the free-carrier concentration in the undoped and doped samples increases to 4 × 1015 and ∼2 × 1016 cm−3, respectively. For all samples, a defect ground level of ∼0.84 eV and continuous background are observed in DLTS spectra after annealing. A correlation between the primary-defect and free-carrier concentrations in undoped and doped CdTe is observed. Chlorine is a main residual impurity in the undoped samples. It is assumed that the defect is a complex including chlorine and observed structural defects in CdTe.