Large Area ${rm Cd}_{0.9}{rm Zn}_{0.1}{rm Te}$ Pixelated Detector: Fabrication and Characterization

摘要

${rm Cd}_{0.9}{rm Zn}_{0.1}{rm Te}$ (CZT) based pixelated radiation detectors have been fabricated and characterized for gamma ray detection. Large area CZT single crystals has been grown using a tellurium solvent method. A $10 times 10$ guarded pixelated detector has been fabricated on a $sim 19.5 times 19.5 times 5~hbox{mm}^{3}$ crystal cut out from the grown ingot. The pixel dimensions were $1.3 times 1.3~hbox{mm}^{2}$ and were pitched at 1.8 mm. A guard grid was used to reduce interpixel/inter-electrode leakage. The crystal was characterized in planar configuration using electrical, optical and optoelectronic methods prior to the fabrication of pixelated geometry. Current-voltage (I-V) measurements revealed a leakage current of 27 nA at an operating bias voltage of 1000 V and a resistivity of $sim 3.1 times {10^{10}}~Omegahbox{-cm}$ . Infrared transmission imaging revealed an average tellurium inclusion/precipitate size less than $8~muhbox{m}$. Pockels measurement has revealed a near-uniform depth-wise distribution of the internal electric field. The mobility-lifetime product in this crystal was calculated to be $6.2 times {10^{ - 3}}~hbox{cm}^{2}/{rm V}$ using alpha ray spectroscopic method. Gamma spectroscopy using a $^{137}{rm Cs}$ source on the pixelated structure showed fully resolved 662 keV gamma peaks for all the pixels, with percentage resolution (FWHM) as high as 1.8%.