From Event: SPIE Optical Engineering + Applications, 2016
The traditional method for electron lifetime measurements of CdZnTe (CZT) detectors relies on using the Hecht equation. The procedure involves measuring the dependence of the detector response on the applied bias and applying the Hecht equation to evaluate the mu-tau product, which in turn can be converted into the carrier lifetime if the mobility is known. Despite general acceptance of this technique, which is very convenient for comparative testing of different CZT materials, the assumption of a constant electric field inside a detector is unjustified. In the Hecht equation, this assumption means that the drift time would be a linear function of the drift distance. This condition is rarely fulfilled in practice at low applied biases where the Hecht equation is most sensitive to the mu-tau product. As a result, researchers usually take measurements at relatively high biases, which work well in the case of the low mu-tau material, <10-3 cm2/V, but give significantly underestimated values for the case of high mu-tau crystals. In this work, we applied the time-of-flight (TOF) technique to measure the electron lifetimes in long-drift-length (3 cm) standard-grade CZT detectors produced by Redlen Technologies. The TOF-based techniques are traditionally used for monitoring the electronegative impurity concentrations in noble gas detectors by measuring the electron lifetimes. We found the electron mu-tau product of tested crystals is in the range 0.1-0.2 cm2/V, which is an order of the magnitude higher than any value previously reported for CZT material. In this work, we reported the measurement procedure and the results. We will also discuss the applicability criteria of the Hecht equation for measuring the electron lifetime in high mu-tau product CZT.
Aleksey E. Bolotnikov, Giuseppe S. Camarda, Eric Chen, Yonggang Cui, Rubi Gul, Václav Dedic, Gianluigi De Geronimo, Jack Fried, Anwar Hossain, Jason M. MacKenzie, Paul Sellin, Saeid Taherion, Emerson Vernon, Ge Yang, Uri El-hanany, and Ralph B. James, "Using the TOF method to measure the electron lifetime in long-drift CdZnTe detectors
(Conference Presentation)," Proc. SPIE 9968, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVIII, 996812 (Presented at SPIE Optical Engineering + Applications: August 31, 2016; Published: 2 November 2016); https://doi.org/10.1117/12.2240091.5178382286001.
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