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We grew CdTe x Se 1− x crystals with nominal Se concentrations of 5%, 7%, and 10% by the vertical Bridgman technique, and evaluated their compositional homogeneity and structural quality at the NSLS’ X-ray fluorescence and white beam X-ray topography beam lines. Both X-ray fluorescence and photoluminescence mapping revealed very high compositional homogeneity of the CdTe x Se 1− x crystals. We noted that those crystals with higher concentrations of Se were more prone to twinning than those with a lower content. The crystals were fairly free from strains and contained low concentrations of sub-grain boundaries and their networks. [ABSTRACT FROM AUTHOR]

Abstract: We characterized the structural quality of CdTe x Se1−x crystals grown by the Traveling Heater Method (THM) from a Te-rich solution using Synchrotron White Beam X-ray Diffraction Topography in the reflection mode. Structural defects were also studied by chemical etching of the crystal surfaces. The crystals were found to be fairly free from strains, and they had very few sub-grain boundaries and dislocation/sub-grain boundary networks. [Copyright &y& Elsevier]

We grew CdTe x Se1−x (CTS) crystals from a Te-rich solution by using the traveling heater method (THM). The average size distribution and concentration of Te inclusions/precipitates in these as-grown samples were measured to be ~7×104 cm−3, which is much lower than values typical for the present state-of-the-art commercial CdZnTe (CZT) material. Their low-temperature photoluminescence measurement indicates high quality of the material; however the resistivity obtained via I–V curve measurements was ~5×108 Ω-cm, which is low in comparison to that required for gamma detectors. A well-resolved alpha response peak can be detected for both planar- and hemispherical detector geometry. The (μτ)e value for our as-grown sample at room temperature was found to be ~4×10−3 cm2/V. [ABSTRACT FROM AUTHOR]

Abstract: Cadmium zinc telluride (Cd1−x Zn x Te) crystals have many applications in optoelectronics and as room-temperature detectors. We grew bismuth-doped CZT crystals by the standard Bridgman Oscillation Method, and compared them with such crystals grown in the thermal environment of a furnace modified with a Pt coldfinger (metal rod). The coldfinger serves as a tool for stabilizing the solid–liquid interface by extracting heat from the as-grown crystal, and thereby improving the ingot''s crystalline quality. We detailed the crystal''s quality via high-resolution X-ray diffraction (HRXRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Synchrotron-based X-ray microfluorescence (μSXRF) images, as well as by etch-pit density (EPD) measurements. Our results demonstrated that the Pt coldfinger is an effective tool for improving the quality of CZT bulk material. [Copyright &y& Elsevier]

Cadmium Magnesium Telluride (Cd1−x Mg x Te/CMgT) offers several pronounced potential advantages over the well-studied CdZnTe and CdMnTe, possibly making it a good alternative for room-temperature X- and gamma-ray detectors. It possesses high crystallinity due to the near-similar lattice structure of CdTe (6.48Å) and MgTe (6.42Å). Its displays good homogeneity as the Mg segregation coefficient in CdTe is nearly 1. Furthermore, inhomogeneities in the crystal due to alloying effects can be minimized, because the optimal energy band-gap can be achieved using less Mg in CdMgTe compared to Zn and Mn needed in CdZnTe and CdMnTe. We recently grew an undoped- and a doped-ingot of CdMgTe, characterized its material properties, and tested its detection performance. We obtained some exciting results that demonstrated some of its potential advantages over the other materials. The band-gap was measured as 1.61eV at room temperature and 1.73eV at 4K. The yield was predominantly single crystals with about two orders-of-magnitude fewer Te inclusions and other growth defects compared to CdZnTe and CdMnTe crystals. The measured resistivity of the undoped annealed crystal was about ∼107 Ω-cm; after doping in a second growth trial, it increased by 2–3 orders-of-magnitude (109–1010 Ω-cm). We examined the doped as-grown crystal as a radiation detector and acquired reasonably good spectral response to an Am-241 source. The estimated mu-tau value was as high as 7×10−4 cm2/V, which is an extraordinarily high value for such an early-phase investigation. We also analyzed point and extended defects using various techniques that will be discussed in this manuscript. [ABSTRACT FROM AUTHOR]