Properties of CdZnTe compounds grown by high-pressure Bridgman technique

Investigated in this work mixed Cd1-xZnxTe crystals were grown from the melt by Bridgman-Stockbarger method in the range of the composition 0<x<1. These materials are interesting for the materials science and were successively applied as X-ray and gamma-ray detectors.
The crystal structure and material phase were characterized by X-ray diffraction (XRD), also the actual composition of the grown crystals was measured with SEM/EDS method along the growth axis. The segregation coefficient of Zn in the CdTe matrix has been evaluated as close to unity. The energy gap as a function of the composition was determined from transmission spectroscopy.
A systematic study of the thermal properties of Cd1-xZnxTe alloys was undertaken. The thermal diffusivity and effusivity of investigated crystals were derived from the photopyroelectric calorimetry (PPE) and allowed calculating the thermal conductivity. Diagrams of the thermal conductivity versus composition were analyzed applying a model for mixed semiconducting crystals given by Sadao Adachi. The contribution of the thermal resistivity arising from the lattice disorder to the total resistivity of the crystal has been determined.
Positron annihilation lifetime spectroscopy (PALS) was used to examine grown-in defects in these crystals as a function of Zn content and the temperature. The positron lifetime spectra revealed both open volumes and shallow traps regardless of the sample composition. In particular, we found that both average and bulk lifetimes are much higher in ternary alloys (CdZnTe) than those in binary systems (CdTe and ZnTe). We showed also a clear correlation between defects and the lattice thermal conductivity of studied samples.

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