Two-step annealing to remove Te secondary-phase defects in CdZnTe while preserving the high electrical resistivity
- Brookhaven National Lab. (BNL), Upton, NY (United States)
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:
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Sponsoring Organization:
- 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:
- SC0012704
- OSTI ID:
- 1424943
- Alternate ID(s):
- OSTI ID: 1476269
- Report Number(s):
- BNL--203301-2018-JAAM
- Journal Information:
- IEEE Transactions on Nuclear Science, Journal Name: IEEE Transactions on Nuclear Science Journal Issue: 8 Vol. 65; ISSN 0018-9499
- Publisher:
- IEEECopyright Statement
- Country of Publication:
- United States
- Language:
- English
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