TY - JOUR
T1 - Two-step annealing to remove te secondary-phase defects in CdZnTe while preserving the high electrical resistivity
AU - Kim, Kihyun
AU - Hwang, Seokjin
AU - Yu, Hwangseung
AU - Choi, Yoonseok
AU - Yoon, Yongsu
AU - Bolotnikov, Aleksey E.
AU - James, Ralph B.
N1 - Funding Information:
Manuscript received March 23, 2018; accepted July 10, 2018. Date of publication July 17, 2018; date of current version August 15, 2018. This work was supported by the National Research Foundation of Korea through the Ministry of Science, ICT, and Future Planning, South Korea under Grant NRF-2015M2B2A9032788 and in part by Korea University under Grant K1605381.
Publisher Copyright:
© 1963-2012 IEEE.
PY - 2018/8
Y1 - 2018/8
N2 - 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.
AB - 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.
KW - CdZnTe (CZT)
KW - high resistivity
KW - pulse-height spectra
KW - real-time monitoring
KW - two-step annealing
UR - http://www.scopus.com/inward/record.url?scp=85050185620&partnerID=8YFLogxK
U2 - 10.1109/TNS.2018.2856805
DO - 10.1109/TNS.2018.2856805
M3 - Article
AN - SCOPUS:85050185620
SN - 0018-9499
VL - 65
SP - 2333
EP - 2337
JO - IEEE Transactions on Nuclear Science
JF - IEEE Transactions on Nuclear Science
IS - 8
M1 - 8412222
ER -