Characterization of high-resistivity CdTe and Cd0.9Zn0.1Te crystals grown by Bridgman method for radiation detector applications

Krishna C. Mandal; Ramesh M. Krishna; Rahmi O. Pak; Mohammad A. Mannan

doi:10.1117/12.2063054

17 September 2014 Characterization of high-resistivity CdTe and Cd_0.9Zn_0.1Te crystals grown by Bridgman method for radiation detector applications

Krishna C. Mandal, Ramesh M. Krishna, Rahmi O. Pak, Mohammad A. Mannan

Author Affiliations +

Proceedings Volume 9213, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVI; 92131L (2014) https://doi.org/10.1117/12.2063054
Event: SPIE Optical Engineering + Applications, 2014, San Diego, California, United States

Abstract

CdTe and Cd_0.9Zn_0.1Te (CZT) crystals have been studied extensively for various applications including x- and γ-ray imaging and high energy radiation detectors. The crystals were grown from zone refined ultra-pure precursor materials using a vertical Bridgman furnace. The growth process has been monitored, controlled, and optimized by a computer simulation and modeling program developed in our laboratory. The grown crystals were thoroughly characterized after cutting wafers from the ingots and processed by chemo-mechanical polishing (CMP). The infrared (IR) transmission images of the post-treated CdTe and CZT crystals showed average Te inclusion size of ~10 μm for CdTe and ~8 μm for CZT crystal. The etch pit density was ≤ 5×10⁴ cm^-2 for CdTe and ≤ 3×10⁴ cm^-2 for CZT. Various planar and Frisch collar detectors were fabricated and evaluated. From the current-voltage measurements, the electrical resistivity was estimated to be ~ 1.5×10¹⁰ Ω-cm for CdTe and 2-5×10¹¹ Ω-cm for CZT. The Hecht analysis of electron and hole mobility-lifetime products (μτ_e and μτ_h) showed μτ_e = 2×10^-3 cm²/V (μτ_h= 8×10^-5 cm2/V) and 3-6×10^-3 cm²/V (μτh = 4- 6×10-5 cm2/V) for CdTe and CZT, respectively. Detectors in single pixel, Frisch collar, and coplanar grid geometries were fabricated. Detectors in Frisch grid and guard-ring configuration were found to exhibit energy resolution of 1.4% and 2.6 %, respectively, for 662 keV gamma rays. Assessments of the detector performance have been carried out also using ²⁴¹Am (60 keV) showing energy resolution of 4.2% FWHM.

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Krishna C. Mandal, Ramesh M. Krishna, Rahmi O. Pak, and Mohammad A. Mannan "Characterization of high-resistivity CdTe and Cd_0.9Zn_0.1Te crystals grown by Bridgman method for radiation detector applications", Proc. SPIE 9213, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVI, 92131L (17 September 2014); https://doi.org/10.1117/12.2063054

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