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Effect of the thickness of CdTe crystals on electrical and detection properties of Cr/CdTe/Au Schottky-diode detectors
Author(s): Valery M. Sklyarchuk; Volodymyr A. Gnatyuk; Xiaodong Fang; Toru Aoki
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Paper Abstract

The electrical and detection properties of the X/gamma-ray detectors, fabricated using commercial detector-grade p-like CdTe single crystals grown by Acrorad Co., were studied. The detectors were developed as Cr/CdTe/Au Schottky diodes using CdTe wafers with an area of 5 × 5 mm2 and different thicknesses (0.25, 0.5, 0.75, 1.0 and 2.0 mm). Both the Schottky and Ohmic contacts were formed on the opposite sides of semi-insulating CdTe(111) crystals after preliminary chemical and Ar-ion etchings using different parameters. The Cr/CdTe/Au Schottky diodes demonstrated steep rectification that made it possible to apply high reverse bias voltage up to V = 1500-2000 V at moderately low dark currents. Having the rectifying contact area of 10 mm2, the diodes showed dark currents ~ 2-3 nA at V = 1000 V (T = 300 K). The dominant charge carrier transport mechanisms were analyzed using the I-V characteristics and determined as: generation-recombination in the space-charge region (SCR) at V = 1-100 V, the charge transport in the conditions when the SCR width exceeded the thickness of a semiconductor crystal at elevated voltages and, finally currents limited by space charge at even higher bias voltages. For radiation from a 137Cs radioisotope, the Cr/CdTe/Au detectors fabricated on thin (0.5 mm) semiconductor crystals showed the highest energy resolution (FWHM = 0.5%@662 keV). The detection efficiency increased in 4 times with increasing the crystal thickness (up to 2 mm), although the energy resolution deteriorated from 0.5 % to 3 % that, however, was still acceptable for spectroscopic operation of the detectors.

Paper Details

Date Published: 9 September 2019
PDF: 7 pages
Proc. SPIE 11114, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XXI, 111141S (9 September 2019); doi: 10.1117/12.2529965
Show Author Affiliations
Valery M. Sklyarchuk, Yuriy Fedkovych Chernivtsi National Univ. (Ukraine)
Volodymyr A. Gnatyuk, V.E. Lashkaryov Institute of Semiconductor Physics (Ukraine)
Shizuoka Univ. (Japan)
Xiaodong Fang, Anhui Institute of Optics and Fine Mechanics (China)
Toru Aoki, Shizuoka Univ. (Japan)


Published in SPIE Proceedings Vol. 11114:
Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XXI
Ralph B. James; Arnold Burger; Stephen A. Payne, Editor(s)

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