Two-step annealing to remove te secondary-phase defects in CdZnTe while preserving the high electrical resistivity

Kihyun Kim, Seokjin Hwang, Hwangseung Yu, Yoonseok Choi, Yongsu Yoon, Aleksey E. Bolotnikov, Ralph B. James

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

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-ray and gamma-ray radiation detectors. We find that Te secondary-phase defects in CZT crystals can be removed through postgrowth two-step annealing without creating new trapping centers (i.e., prismatic punching defects). Two-step annealing (with the first under a Cd pressure and the second one under 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 °C/600 °C (CZT/Cd) for 24 h, 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 °C/380 °C (CZT/Te) for 120 h, 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. Pulse-height spectra taken with the two-step annealed CZT detectors showed an improved detector performance due to a reduced concentration and the size of Te secondary-phase defects.

Original languageEnglish
Article number8412222
Pages (from-to)2333-2337
Number of pages5
JournalIEEE Transactions on Nuclear Science
Volume65
Issue number8
DOIs
Publication statusPublished - 2018 Aug

Keywords

  • CdZnTe (CZT)
  • high resistivity
  • pulse-height spectra
  • real-time monitoring
  • two-step annealing

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering
  • Electrical and Electronic Engineering

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