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Title: Two-Step Annealing to Remove Te Secondary-Phase Defects in CdZnTe While Preserving the High Electrical Resistivity

Journal Article · · IEEE Transactions on Nuclear Science
ORCiD logo [1];  [1];  [1];  [1]; ORCiD logo [2];  [3];  [4]
  1. Korea Univ., Seoul (Korea, Republic of)
  2. Kyushu Univ. (Japan)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
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We report the presence of Te secondary-phase defects (i.e., Te inclusions and Te precipitates) is a major factor limiting the performance of CdZnTe (CZT) X- and gamma-ray radiation detectors. We find that Te secondary-phase defects in CZT crystals can be removed through post-growth, two-step annealing without creating new trapping centers (i.e., prismatic punching defects). Two-step annealing (with the first in a Cd pressure and the second one in a Te pressure) was demonstrated to be effective in removing the Te secondary-phase defects, while preserving the electrical resistivity of the CZT detector. The first step involves annealing of semi-insulating CZT under a Cd overpressure at 700/600 °C (CZT/Cd) for 24 hours, which completely eliminated the Te-rich secondary-phase defects (Te inclusions). However, it resulted in a lower resistivity of the samples (down to 2 × 104-6 Ω·cm). A subsequent annealing step involves processing CZT under a Te ambient condition at 540/380 °C (CZT/Te) for 120 hours, which restored the crystal’s resistivity to 6.4 × 1010 Ω·cm without creating new Te secondary-phase defects. However, Te inclusions reappeared in the case of unnecessarily long Te ambient annealing. Finally, pulse height spectra taken with the two-step annealed CZT detectors showed improved detector performance due to a reduced concentration and size of Te secondary-phase defects.

Research Organization:
Savannah River Site (SRS), Aiken, SC (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Organization:
USDOE; USDOE National Nuclear Security Administration (NNSA), Office of Nonproliferation and Verification Research and Development (NA-22); US Department of Homeland Security (DHS)
Grant/Contract Number:
AC09-08SR22470; SC0012704
OSTI ID:
1476269
Alternate ID(s):
OSTI ID: 1424943
Report Number(s):
SRNL-STI-2018-00004; BNL-203301-2018-JAAM
Journal Information:
IEEE Transactions on Nuclear Science, Vol. 65, Issue 8; ISSN 0018-9499
Publisher:
IEEECopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 4 works
Citation information provided by
Web of Science

Figures / Tables (6)

Fig. 1(p. 12)figure Fig. 1
Fig. 2(p. 13)figure Fig. 2
Fig. 3(p. 13)figure Fig. 3
Fig. 4(p. 14)figure Fig. 4
Fig. 5(p. 14)figure Fig. 5
Fig. 6(p. 15)figure Fig. 6

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