Characterization of Cd0.9Zn0.1Te based virtual Frisch grid detectors for high energy gamma ray detection

Abstract

Detector grade CZT single crystals have been grown from zone refined Cd, Zn, and Te (∼7N) precursor materials using a tellurium solvent method. Infrared transmission imaging has shown an average tellurium inclusion size of ∼8μm in the as-grown crystal. Radiation detectors were fabricated in planar and virtual Frisch grid geometry and characterized for their spectroscopic performance. Charge transport properties revealed a high drift mobility of∼1200cm2/Vs and a mobility–lifetime product of ∼2.8×10−3cm2/V. A detector with planar configuration (dimensions 6.9×6.9×4.8mm3) showed an energy resolution of 4.7% for 59.5keV gamma rays. The detector in a Frisch grid configuration (dimensions 4.2×6.2×6.5mm3) exhibited an energy resolution of 1.4% for 662keV gamma rays. Digital spectroscopic measurements were carried out using a high-resolution digitizer card. A biparametric correlation scheme was employed to study the effect of charge loss on energy resolution of the planar detector. Based on this correlation scheme, a digital correction method was applied and improved pulse-height spectrum was obtained for 662keV gamma rays using the planar detector with spectral features comparable to those of the virtual Frisch grid detector.