Te inclusions in large size CdTe THM crystals

The homogeneity of compound semiconductors wafers of high resistivity affects the production yield, and, therefore, the cost for industry. In general, the production yield of good spectral quality large size detectors is rather low compared to those of small size. CdTe as well as CdZnTe compounds are the most promising semiconductor materials used in the field of room temperature X- and gamma ray detectors. They can be used for the detection of low energy X-ray with resolution in the 200 eV range as well as in high energy gamma-spectroscopy, for radiation monitoring in nuclear field, space and astronomy and many other like medical and industrial imaging systems. Among the various crystal growing methods (Bridgman, (LPB, HPB, Horizontal Bridgman), Physical Vapor Transport (PVT), Travelling Heater Method), THM is low temperature growth process where the crystals have relatively low number of defects and less impurity incorporation from the crucible. The main non-uniformity of the crystals comes essentially from Te excess growth conditions resulting from the retrograde slope of solidus line in the phase diagram. The influence of Te inclusions and precipitates on the electrical and spectroscopic properties of the detectors obtained from large size CdTe, crystals grown by THM method, are the subject of the present paper. The latest results will be presented of the distribution and size of Te inclusions in THM grown CdTe crystals. IR imaging, resistivity and charge carrier mobility as well as electric and spectroscopic measurements have been used for materials characterization. Data will be presented obtained by CoReMa, Contactless Mobility-Lifetime Mapping and IR Microscopy. The data will be correlated with the detector performance of selected samples.

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