Hui Hua

Cd1−xZnxTe: Growth and characterization of crystals for X-ray and gamma-ray detectors

Abstract The choice a suitable crystal growth method and a reasonable x value is of profound importance in the preparation of high quality Cd1−xZnxTe crystals for x-ray and gamma-ray detectors. The present paper reviews the evolution and development of Cd1−xZnxTe crystal growth for x-ray and gamma-ray detectors. At the same time, emphasis is put upon finding the relationship between the x value and the quality of the Cd1−xZnxTe. Three sets of Cd1−xZnxTe ingots with different x values, specifically 0.10, 0.15, and 0.20 were grown by the vertical Bridgman method (VBM) and characterized. Their x specification was then correlated with their dislocation densities, Te precipitates, inclusions, IR transmission, resistivities, and impurity concentrations, respectively. It was found that VBM Cd0.85Zn0.15Te as grown in this paper possessed the best choice of qualities with respect to defects and impurities.

Upgrading of CdZnTe by annealing with pure Cd and Zn metals

A method for the annealing of a CdZnTe crystal is described in this paper. Pure Cd and Zn metals are used as annealing sources, which simultaneously provide exact Cd and Zn equilibrium partial pressures for CdZnTe at a certain temperature. Characterizations reveal that homogeneity is highly improved and the defect densities are decreased by more than one order, and hereby the structural, optical and electrical properties of the CdZnTe crystal are evidently improved by this annealing. Investigation of the temperature dependence of the CdZnTe quality after annealing shows 1073 K to be the preferable annealing temperature for CdZnTe. This annealing process has already been demonstrated to be superior to approximate equilibrium partial pressure annealing by using Cd1?yZny alloy as the annealing source.

Effects of two-step annealing on properties of Cd1-xZnxTe single crystals

Abstract The Cd 1- x Zn x Te(CZT) single crystals were annealed by a two-step method including a vapor-environment step and a liquid-environment step in sequence. The effects of annealing on the properties of CZT were analyzed in detail. IR transmission measurement results show that IR transmission of CZT is improved dramatically after annealing. X-ray rocking curves indicate that the annealing treatment ameliorates crystal quality obviously, which is ascribed to the release of residual stress and the reduction of point defects. Photoluminescence(PL) spectra reveal that the full width at half maximum(FWHM) of the donor-bound exciton ( D 0 , X ) peak is reduced obviously, and the free exciton emission is weakened after annealing. Meanwhile, the intensity of the donor-acceptor pair(DAP) peak decreases to a great degree, which implies that the impurities are removed from CZT wafers. In addition, the deep defect-related emission band D complex disappears after annealing, which mean that Cd vacancies are well-compensated. The results confirm that the two-step annealing is an effective approach to improve the qualities of CZT single crystals.