Optimizing CdZnTeSe Frisch-Grid Nuclear Detector for Gamma-Ray Spectroscopy

• Main Authors: Stephen U. Egarievwe, Utpal N. Roy, Ezekiel O. Agbalagba, Benicia A. Harrison, Carmella A. Goree, Emmanuel K. Savage, Ralph B. James
• Format: Article
• Language: English
• Published: IEEE 2020-01-01
• Series: IEEE Access
• Subjects: CdZnTeSe detectors; detector resolution; Frisch-grid; gamma-ray detector; nuclear radiation detector; traveling heater method
• Online Access: https://ieeexplore.ieee.org/document/9149582/

Wide bandgap semiconductor materials capable of detecting X-rays and gamma-rays at room temperature without cryogenic cooling have great advantages that include portability and wide-area deployment in nuclear and radiological threat defense. Additional major applications include medical imaging, spectroscopy, and astrophysics. Most current room-temperature ionizing radiation detector devices are fabricated from cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe). Cadmium zinc telluride selenide (CdZnTeSe or CZTS) can be grown with high crystal yield compared to CdTe and CdZnTe. Thus, CZTS has the advantage of lowering the cost of room-temperature nuclear detectors. Thick CdTe-based detectors are prone to the trapping of charge carriers, thus limiting energy resolution and efficiency. A Frisch-Grid configuration helps to solve this problem. This research is focused on optimizing the Frisch-grid configuration for a CZTS detector. The CZTS was grown by traveling heater method. Infrared images of the CZTS matrix largely showed the absence of tellurium inclusions. The resistivity of the CZTS obtained from a current-voltage plot is of the order of 10¹⁰ Ω.cm. The charge-transport characterized by measuring the electron mobility-lifetime product is 4.7 × 10^-3 cm²/V. Detector resolution was measured for various Frisch-ring widths. For a 4.8 × 4.9 × 9.7 mm³ detector, the best Frisch-ring widths were found to be 3-4 mm. A detector resolution of 1.35% full-width-at-half-maximum was obtained for the 3-mm width at -2300 V bias voltage for the 662-keV gamma peak of ¹³⁷Cs. A resolution of 1.36% was obtained for the 4-mm width at -1800 V applied bias.