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Radiation detectors with different thickness are needed to detect gamma rays with various energies. In this paper, a post-growth annealing method was used to improve the properties of CdMnTe:In (CMT:In) crystals with different thickness for gamma-ray detectors. The results indicated that Te inclusions in CMT:In crystals with different thickness were reduced remarkably after annealing. Both the resistivity and IR transmittance of annealed CMT:In crystals with different thickness increased obviously, which suggested that the crystal quality was improved. For the detectors fabricated by annealed CMT:In slices with 1 mm, 2 mm and 5 mm thickness, the energy resolutions were enhanced about 252%, 193% and 141%, respectively. And ( μτ ) e values were enhanced about 80%, 80% and 76%, respectively. The performance of the detectors was greatly improved after annealing. [ABSTRACT FROM AUTHOR]

The migration of dislocations in substrate-grade CdZnTe (CZT) single crystals during temperature gradient annealing under Cd/Zn vapor has been investigated. The etch pit density (EPD) and configuration of dislocations have been evaluated before and after annealing in CZT crystals with and without Cd-rich second phase (Cd-SP) particles, respectively. After Cd/Zn overpressure annealing, dislocation reduction in CZT crystals was observed. However, dislocation walls with 120° intervals along <211> crystalline direction were observed in the both types of CZT crystals. The formation of these dislocation walls can be attributed to the reaction of <110> dislocations. Moreover, it is considered that the release of the restored stress during annealing act as the domain driving force for dislocation migration, by comparing the variation of dislocation configuration in CZT crystals with and without Cd-SP particles. [ABSTRACT FROM AUTHOR]

In this paper, an effective annealing method in which CdMnTe:In (CMT:In) single crystals were coated with CMT powders of the same composition was used to improve the crystal quality of CMT:In crystals. The results indicated that the density of Te inclusions decreased as the annealing time increased. The resistivity and IR transmittance of annealed CMT:In crystals were enhanced obviously. The resistivity of 120 h annealed crystal increased even two orders of magnitude. The reduction of full-width at-half-maximum (FWHM) and the increase of the intensity of X-ray rocking curve indicated an improvement of the crystal quality. PL measurements also showed the crystal quality improved after annealing. No characteristic peak of 241 Am γ-ray could be observed in the detector fabricated with as-grown crystal. Remarkably, for the detector fabricated with annealed crystals, the peak of 241 Am γ-ray appeared. And the energy resolution and μτ value were improved as the annealing time increased. Specially, 120 h annealed CMT:In crystal with 10.11% energy resolution and 1.20×10 −3 cm 2 /V μτ value has the best detector performance. [ABSTRACT FROM AUTHOR]

Electron backscattered diffraction (EBSD) is used to study the effect of huge-density structural vacancies (SVs) on the twins in defect zinc-blende (DZB) crystal Hg 3 In 2 Te 6 (MIT) grown by the Bridgman method. Comparing with typical perfect zinc-blende (PZB) crystals, three types of twins with several differences are observed in MIT. EBSD and high-resolution transmission electron microscopy (HRTEM) analysis suggest that the twins are deformation twins. The differences between them are attributed to the suppression of high-density structural vacancy clusters on the glide of twinning dislocations. Besides, the residual strain of most twins is found to be higher than that of the corresponding matrices. [ABSTRACT FROM AUTHOR]

The effects of infrared (IR) irradiation on the transport properties in CdZnTe crystals were investigated by using thermally stimulated current (TSC) measurements. The temperature increasing process in TSC measurements could be described by the standard Shockley-Read-Hall (SRH) model. When applying IR irradiation to this process, the relative balance from the mixing effect of the six thermal and optical transitions could be described by the modified SRH model. Under steady-state condition at room temperature, the increase of the ionization probability of the deep donor (T4) from ~0.71 in the dark to ~0.93 with IR irradiation, theoretically predicted by the SRH model was identified, which is consistent with the increase of the effective density of T4 from (5.28±0.26)×10 13 cm −3 in the dark to (7.25±0.36)×10 13 cm −3 with IR irradiation, experimentally measured from TSC results. Therefore, the effects of IR irradiation on the transport properties, by suppressing trapping and encouraging de-trapping through the defect traps, would further contribute to improving the charge collection processes and the consequent spectroscopic characteristics of CZT detectors. [ABSTRACT FROM AUTHOR]

We investigated the distribution of deep-level defects in CdZnTe:In ingots along the growth direction using thermally stimulated current (TSC) spectra. Higher concentration of Te antisite-related deep donors were found in the tail region due to Te enrichment in the melt as solidification proceeded. The compensation between In Cd + defects and Cd vacancies results in low concentration of net free electrons. High resistivity with n-type conduction was demonstrated from the I – V analysis. Hall mobility is lower in the tail due to higher concentration of Te antisite-related deep donors. [ABSTRACT FROM AUTHOR]

Abstract: Electron backscatter diffraction (EBSD) and Raman scattering were used to characterize twins and Te particles in CdMnTe crystals grown by the vertical Bridgman method. The size, concentration and phase structure of Te particles, as well as the orientation of twins were studied. {111} twins decorated with Te particles were identified by low and high magnitude EBSD mapping. Three type crystal phases of Te particles were observed, including hexagonal, monoclinic and high-pressure rhombohedral phase. Most of Te particles were preferentially oriented with the {110}CdMnTe//{}Te. The A1 (Te) and E (Te) modes in CdMnTe Raman scattering spectroscopy were found with red-shift than single Te phase due to the tensile stress effect. [Copyright &y& Elsevier]

Abstract: CdMnTe (CMT) has been recently considered to be a good candidate as a promising material for the manufacture of room-temperature nuclear radiation detectors due to its better lattice strengthening, wider band gap energy and low segregation potential. This paper reports the recent progress of detector-grade CMT crystals in Northwestern Polytechnical University. CdMnTe:In ingots with diameter of 30mm were grown using a Modified Vertical Bridgman (MVB) method. Current–voltage measurements were performed on single element planar configuration structure with Au electrode and the obtained resistivity of CMT samples was up to 6.19×1010 Ωcm. PL spectra and IR transmittance measurement on the samples were revealed that the as-grown CMT crystal possess of high quality. IR microscope showed that the Te inclusions in CMT are 10–20μm in diameter and within the range 1×104–3×104 cm−3 in concentration. The 241Am gamma-ray spectral was obtained for the CMT single planar detector with the energy resolution of 12.38% of the 59.5keV peak. The mobility-lifetime products for the electron and hole of the as-grown CMT crystals were evaluated to be 1.22×10−3 cm2 V−1 and 3.0×10−5 cm2 V−1, respectively. [Copyright &y& Elsevier]

Abstract: Impurities in three cadmium zinc telluride (Cd1− x Zn x Te or CZT) ingots grown by the modified vertical Bridgman (MVB) method were examined by using inductively coupled plasma mass spectrometry (ICP-MS). The distribution and segregation of impurities along the CZT ingots were found to vary with the concentration and the growth conditions. Photoluminescence (PL) and voltage–current measurements were performed to evaluate the effects of the impurities on the optical and electrical properties. The red shift of the (D 0, X) and DAP positions and the broadening of the DAP band in PL spectrum were observed in the high-impurity CZT ingot. The voltage–current measurement shows a higher resistivity when the impurity concentration was increased. The above results imply that the high-impurity CZT ingot was highly compensated. [Copyright &y& Elsevier]