CdZnTe and CdTe detector arrays for hard X-ray and gamma-ray astronomy

Stahle, C. M.; Parker, Bradford H.; Parsons, A.; Barbier, L.; Barthelmy, S. D.; Gehrels, N.; Palmer, D. M.; Snodgrass, Steve; Tueller, J.

doi:10.1016/s0168-9002(99)00610-5

Cited by 26 publications

(12 citation statements)

References 8 publications

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“…Different explanations could account for this type of detector inhomogeneity, including the hypothesis that they originate from spherical (or filament) Te precipitations in the CdTe crystal growth. Tellurium inclusions in single CdTe detectors have been reported under infrared transmission imaging, with a "relatively uniform distribution" [14]. However, the hypothesis that the small scale structures visible in our images are related to some bump-bonding effect is not completely ruled out.…”

Section: Discussionmentioning

confidence: 66%

First experimental tests with a CdTe photon counting pixel detector hybridized with a Medipix2 readout chip

Chmeissani

Fröjdh

Gal

et al. 2004

IEEE Trans. Nucl. Sci.

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We present preliminary tests of hybrid pixel detectors consisting of the Medipix2 readout chip bump-bonded to a 1-mm-thick CdTe pixel detector. This room temperature imaging system for single photon counting has been developed within the Medipix2 European Collaboration for various imaging applications with X-rays and gamma rays, including dental radiography, mammography, synchrotron radiation, nuclear medicine, and radiation monitoring in nuclear facilities. The Medipix2 + CdTe hybrid detector features 256 256 square pixels, a pitch of 55 m, a sensitive area of 14 14 mm 2 . We analyzed the quality of the detector and bump-bonding and the response to nuclear radiation of the first CdTe hybrids. The CdTe pixel detectors, with Pt ohmic contacts, showed an ohmic response when negatively biased up to less than 60 V (electrons collection mode). Tests were also performed in holes collection mode, where a nonresistive behavior was observed above +15 V. We performed a series of imaging tests at low voltage bias with gamma radioactive sources and with an X-ray tube. Under uniform irradiation, we observed for all detectors the presence of numerous, stable structures in the form of small circles of about 200 m diameter, with the central pixels showing a reduced counting efficiency with respect to the periphery (in electrons counting regime). Also long filament structures have been observed. Further investigations will reveal whether they are due to an intrinsic detector response (e.g., due to Te inclusions) or to the bump-bonding process.

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Section: Discussionmentioning

confidence: 66%

First experimental tests with a CdTe photon counting pixel detector hybridized with a Medipix2 readout chip

Chmeissani

Fröjdh

Gal

et al. 2004

IEEE Trans. Nucl. Sci.

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“…Although the ingots are of very large volume, the present HPB technique yields only polycrystals with a nonuniform distribution of µτ products. The IR transmission image of the large wafer shows grain boundaries and a distribution of Te-decorated features [17]. Extensive studies indicate that the grain boundaries decorated with Te inclusions or twin boundaries have an adverse effect on carrier transport in CdZnTe and result in poor spectral response [14], [17], [15].…”

Section: A Hpb-grown Cdzntementioning

confidence: 99%

“…The IR transmission image of the large wafer shows grain boundaries and a distribution of Te-decorated features [17]. Extensive studies indicate that the grain boundaries decorated with Te inclusions or twin boundaries have an adverse effect on carrier transport in CdZnTe and result in poor spectral response [14], [17], [15]. At present, the yield of HPB CdZnTe dies suitable for the fabrication of largearea (> 10 × 10 mm 2 ) X-and γ-ray imaging devices is very low [14].…”

Section: A Hpb-grown Cdzntementioning

confidence: 99%

Recent progress in CdTe and CdZnTe detectors

Takahashi

Watanabe

2001

IEEE Trans. Nucl. Sci.

528

275

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Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) have been regarded as promising semiconductor materials for hard X-ray and γ-ray detection. The high atomic number of the materials (Z Cd =48, Z T e =52) gives a high quantum efficiency in comparison with Si. The large band-gap energy (Eg ∼ 1.5 eV) allows us to operate the detector at room temperature. However, a considerable amount of charge loss in these detectors produces a reduced energy resolution. This problem arises due to the low mobility and short lifetime of holes. Recently, significant improvements have been achieved to improve the spectral properties based on the advances in the production of crystals and in the design of electrodes. In this overview talk, we summarize (1) advantages and disadvantages of CdTe and CdZnTe semiconductor detectors and (2) technique for improving energy resolution and photopeak efficiencies. Applications of these imaging detectors in future hard X-ray and gamma-ray astronomy missions are briefly discussed.

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“…The CdZnTe (CZT) is a key detector technology for X-ray and gamma-ray due to its high absorption efficiency, excellent spatial resolution, good energy resolution, and room temperature operation [1]. Despite these advantages, the use of CZT material is still limited by some macroscopic defects such as the presence of large Te inclusions, twins, grain boundaries, dislocations which are formed during crystallization of the liquid and cooling down of the crystallized bulk ingots.…”

Section: Introductionmentioning

confidence: 99%