Study of the resistivity mapping in CdTe:Cl-correlation with annealing and Te-precipitates

The presence of defects in Cl-doped CdTe crystals influences the electrical properties and the homogeneity of the material. The aim of this paper is to study the effects of thermal treatment on the precipitates present in the volume of the material and thus on the uniformity of the material in regards to both resistivity and precipitate concentrations. The samples are annealed under argon pressure. The number of precipitates, generally of Te, is measured using infrared microscopy. In addition, a low-cost contactless measurement technique for resistivity mapping has been developed. This technique presents a good spatial resolution of approximately 1 mm and a resistivity range measurement of 10⁶-10¹⁰ Ω-cm. The relation between the number of Te-precipitates and the resistivity maps is investigated. A decrease in the number of Te-precipitates after sample annealing is observed. Furthermore, the resistivity decreases with an increase in the number of precipitates in the material. The uniformity of the annealed samples is discussed. The correlation of the resistivity maps and the Te-precipitates is also given, illustrated by comparison topography with resistivity and Te-precipitate concentrations. The contactless resistivity measurement technique is also described.