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Saanichton, Canada

Beikahmadi M.,University of British Columbia | Mirabbasi S.,University of British Columbia | Iniewski K.K.,Redlen Technologies
IEEE Sensors Journal | Year: 2016

In this paper, the design of a low-power low-noise readout circuit for cadmium zinc telluride (CdZnTe or CZT) detectors is presented. Such sensors are used in a variety of applications, including medical imaging, security, and astrophysics. The readout circuit includes a charge-sensitive amplifier (CSA), a reset network to accommodate the leakage current of the detector, and a first-order pulse shaper with a pole-zero cancellation circuit. The CSA has two gain settings for 0-5-and 5-45-fC injected charge, and the pulse shaper is designed to provide four different shaping times. The discharge time constant of the CSA can also be adjusted to accommodate various event rates. Furthermore, a comprehensive noise analysis of the readout system is presented. To facilitate the noise analysis, the equivalent noise charge (ENC) equations are derived analytically. The optimization of the noise performance of the front-end circuit is also discussed. The application-specific integrated circuit is fabricated in a 0.13-μm CMOS process. For a detector capacitance of 250 fF, the measured ENC varies from 66 to 101 e-rms depending on the peaking time. The measured power consumption of the readout circuit is just under 1 mW from a 1.2 V supply. © 2015 IEEE.

Veale M.C.,Rutherford Appleton Laboratory | Bell S.J.,Rutherford Appleton Laboratory | Bell S.J.,University of Surrey | Duarte D.D.,Rutherford Appleton Laboratory | And 5 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2014

CdTe detectors with a thickness of 1 mm and a pixel pitch of 250 μm have been flip-chip-bonded to the HEXITEC read-out ASIC. The detectors record both the position and energy of X-ray interactions producing an X-ray spectrum for each of the 6400 pixels in the energy range 2-200 keV. In this arrangement, detectors have been shown to produce excellent spectroscopy with FWHM better than 1.2 keV at an interaction energy of 59.5 keV. Due to the use of small pixels, a significant number of events experience charge sharing where the total energy of the event is distributed between multiple pixels. Under normal operating conditions, the proportion of events that experience charge sharing was measured to be 36.4%. Without correction these events lead to a reduction in the spectroscopic performance of the detector, the production of pronounced fluorescence and X-ray escape peaks, and the detection sensitivity. In this paper, the effect of different correction algorithms and operating conditions on the detector performance is presented. © 2014 Published by Elsevier B.V.

Iniewski K.,Redlen Technologies
Journal of Instrumentation | Year: 2014

Over the last two decades, the II-VI semiconductors CdTe and CdZnTe (CZT) has emerged as the material of choice for room temperature detection of hard X-rays and soft γ-rays. The techniques of growing the crystals, the design of the detectors, and the electronics used for reading out the detectors have been considerably improved over the last few years. CdTe/CZT materials find now applications in astrophysics, medical imaging and security applications. The paper discusses recent progress in CZT detector technology and outlines possible new application opportunities. © 2014 IOP Publishing Ltd and Sissa Medialab srl.

A radiation detector includes a semiconductor substrate having opposing front and rear surfaces, a cathode electrode located on the front surface of the semiconductor substrate configured so as to receive radiation, and a plurality of anode electrodes formed on the rear surface of said semiconductor substrate. A work function of the cathode electrode material contacting the front surface of the semiconductor substrate is lower than a work function of the anode electrode material contacting the rear surface of the semiconductor substrate.

A radiation detector includes a semiconductor substrate which contains front and rear major surfaces and at least one side surface, a guard ring and a plurality of anode electrode pixels located over the rear surface of the semiconductor substrate, where each anode electrode pixel is formed between adjacent pixel separation regions, a side insulating layer formed on the at least one side surface of the semiconductor substrate, a cathode electrode located over the front major surface of the semiconductor substrate, and an electrically conductive cathode extension formed over at least a portion of side insulating layer, where the cathode extension contacts an edge of the cathode electrode. Further embodiments include various methods of making such semiconductor radiation detector.

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