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Record 25 of 321
Detailed Studies of Pixelated CZT Detectors Grown with the Modified Horizontal Bridgman Method
External Online Source: doi:10.1016/j.astropartphys.2007.08.004
Author and Affiliation:
Jung, I.(Washington Univ., Dept. of Physics, Saint Louis, MO, United States)
Krawczynski, H.(Washington Univ., Dept. of Physics, Saint Louis, MO, United States)
Burger, A.(Fisk Univ., Dept. of Physics, Nashville, TN, United States)
Guo, M.(Fisk Univ., Dept. of Physics, Nashville, TN, United States)
Groza, M.(Fisk Univ., Dept. of Physics, Nashville, TN, United States)
Abstract: The detector material Cadmium Zinc Telluride (CZT) achieves excellent spatial resolution and good energy resolution over a broad energy range, several keV up to some MeV. Presently, there are two main methods to grow CZT crystals, the Modified High-Pressure Bridgman (MHB) and the High-Pressure Bridgman (HPB) process. The study presented in this paper is based on MHB CZT substrates from the company Orbotech Medical Solutions Ltd. [Orbotech Medical Solutions Ltd., 10 Plaut St., Park Rabin, P.O. Box 2489, Rehovot, Israel, 76124]. Former studies have shown that high-work-function materials on the cathode side reduce the leakage current and, therefore, improve the energy resolution at lower energies. None of the studies have emphasized on the anode contact material. Therefore, we present in this paper the result of a detailed study in which for the first time the cathode material was kept constant and the anode material was varied. We used four different anode materials: Indium, Titanium, Chromium and Gold, metals with work-functions between 4.1 eV and 5.1 eV. The detector size was 2.0 x 2.0 x 0.5 cu cm with 8 x 8 pixels and a pitch of 2.46 mm. The best performance was achieved with the low-work-function materials Indium and Titanium with energy resolutions of 2.0 keV (at 59 keV) and 1.9 keV (at 122 keV) for Titanium and 2.1 keV (at 59 keV) and 2.9 keV (at 122 keV) for Indium. Taking into account the large pixel pitch of 2.46 mm, these resolutions are very competitive in comparison to those achieved with detectors made of material produced with the more expensive conventional HPB method. We present a detailed comparison of our detector response with 3D simulations. The latter comparisons allow us to determine the mobility-lifetime-products (mu tau-products) for electrons and holes. Finally, we evaluated the temperature dependency of the detector performance and ls-products. For many applications temperature dependence is important, therefore, we extended the scope of our study to temperatures as low as -30 C. There are two important results. The breakdown voltage increases with decreasing temperature, and electron mobility-lifetime-product decreases by about 30% over a range from 20 C to -30 C. The latter effect causes the energy resolution to deteriorate, but the concomitantly increasing breakdown voltage makes it possible to increase the applied bias voltage and restore the full performance
Publication Date: Aug 28, 2007
Document ID:
20100023307
(Acquired Jun 28, 2010)
Subject Category: ASTROPHYSICS
Document Type: Journal Article
Publication Information: Astroparticle Physics; p. 397?408; Volume 28; Iss. 4-5
Contract/Grant/Task Num: NNG04WC176; NNX07AH37G; NNG04GD70G; NSF/HRD-0420516; DE-FG52-05NA27035
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
National Science Foundation; Washington, DC, United States
National Nuclear Security Administration; Washington, DC, United States
Organization Source: Washington Univ.; Saint Louis, MO, United States
Description: 12p; In English; Original contains color and black and white illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: CADMIUM TELLURIDES; ZINC TELLURIDES; BRIDGMAN METHOD; PIXELS; TEMPERATURE DEPENDENCE; ELECTRIC POTENTIAL; ELECTRON MOBILITY; CRYSTALS; SIMULATION; WORK FUNCTIONS; HIGH PRESSURE; LEAKAGE; SUBSTRATES
Availability Source: Other Sources
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