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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.

In this paper, the effects of Te inclusions on the optical and electrical properties of CdMnTe and CdMgTe crystals grown by the modified vertical Bridgman method were investigated. For CdMnTe ingot, the average size and density distribution of Te inclusions along axial direction were in the range of 12 ~ 29 μm and 1.53 × 104 cm−2 ~ 2.81 × 105 cm−2, respectively. For CdMgTe ingot, the average size and density distribution of Te inclusions were in the range of 6 ~ 20 μm and 8.17 × 103 cm−2 ~ 2.42 × 104 cm−2, respectively. The density and size of Te inclusions increased gradually from the first-to-freeze part to the last-to-freeze part for CdMnTe ingot, while that of CdMgTe ingot first decreased and then increased. For both CdMnTe and CdMgTe ingots, the resistivity, IR transmittance and FWHM of (D0, X) peak first increased and then decreased from the first-to-freeze part to the last-to-freeze part. The middle-to-freeze parts of both ingots had the best crystal quality. For both CdMnTe and CdMgTe detectors, the energy resolution and (μτ)e value were first increased and then decreased from the first-to-freeze part to the last-to-freeze part. The detectors fabricated by the middle-to-freeze parts of both crystals had the best performance and can could meet the requirements of room temperature radiation detection. PACS: 78.30.Fs; 78.55.Et; 81.40.Ef.

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 241Am γ-ray could be observed in the detector fabricated with as-grown crystal. Remarkably, for the detector fabricated with annealed crystals, the peak of 241Am 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 cm2/V μτ value has the best detector performance.

Recently, researchers were interesting in exploring alternative materials for well-studied CdZnTe which was the key material of radiation detection. Cadmium Magnesium Telluride (Cd1-xMgxTe) crystal was regarded as promising one for room temperature X-ray and gamma-ray detectors due to some potential advantages. In this paper, two large-size Cd0.95Mg0.05Te ingots with 30 mm diameter and over 100 mm length were successfully grown by a modified vertical Bridgman method. Two modifications, including Cd excess or Te-rich condition and the accelerated crucible rotation technique (ACRT), were applied in growing process to decrease defects, enhance resistivity and homogenize component distribution. The results indicated that both ingots had a cubic zinc-blende structure. The distribution of Mg element in the ingots along axial direction was very homogeneous. The energy band gap of Cd0.95Mg0.05Te was close to Cd0.9Zn0.1Te. Low density of Te inclusions (103 cm−3 order of magnitudes) and high IR transmittance (over 60%) showed the good crystal quality. Raman scattering spectroscopy also showed a good crystal quality for Cd0.95Mg0.05Te crystals. Thus, Cd0.95Mg0.05Te crystals could be a promising radiation detector material.

In this paper, detector-grade CdMnTe:In (CMT:In) single crystals were annealed under Te atmosphere with various annealing times. The results indicated that the density of Te inclusions had not changed as the annealing time increased, whereas the resistivity exhibited an initial increase followed by a decrease. The conduction type was changed from weak n-type conduction in as-grown crystal to p-type conduction in 60 h annealed crystal. The lR transmittance decreased obviously as the annealing time increased. In the PL spectra, the obvious reduction of the intensity of (D degrees,X) peak and the increase of the intensity of the D-complex peak in the annealed CMT:In crystals indicated a degradation of the crystal quality. The energy resolution of the detector fabricated with 15 h annealed crystal was improved, whereas the mu tau values of the detectors fabricated with all annealed crystals were reduced. Specially, the characteristic peak of Am-241 gamma-ray could not be observed in the detectors fabricated by 60 h annealed crystals. Therefore, optimal annealing temperature and the duration are 773 K and 15 h, respectively. (C) 2015 Elsevier B.V. All rights reserved