Unipolar charge sensing with coplanar electrodes-application to semiconductor detectors

Luke, P.N.

doi:10.1109/23.467848

Cited by 328 publications

(108 citation statements)

References 6 publications

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“…The potential of CdZnTe has been demonstrated through many material and detector technology developments over the last decade. [1][2][3][4][5][6][7][8][9][10][11][12][13] The material has the desirable intrinsic properties of a wide bandgap necessary for room-temperature operation and a high average atomic number for efficient gamma-ray stopping. Furthermore, the CdZnTe material that is commercially available today exhibits negligible polarization effects, has a high bulk resistivity, and has reasonably good electron collection properties.…”

Section: Introductionmentioning

confidence: 99%

“…One of these electron-only approaches is the coplanar-grid charge-sensing technique. 5 This technique and its variations offer the advantages of nearly eliminating the hole collection problem, providing accurate and adjustable correction for electron trapping, producing uniform charge induction, 15,16 realizing near full-volume detection efficiency, 17,18 and requiring only simple conventional pulse-processing electronics. Coplanar-grid detectors 1cm 3 in size have achieved energy resolutions down to about 2% FWHM at 662keV, and hand-held systems have been produced from such detectors.…”

Section: Introductionmentioning

confidence: 99%

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Electron trapping nonuniformity in high-pressure-Bridgman-grown CdZnTe

Amman

Lee

Luke

2002

Journal of Applied Physics

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Gamma-ray spectroscopy is a valuable tool of science and technology. Many applications for this tool are in need of a detector technology capable of achieving excellent energy resolution and efficient detection while operating at room temperature. Detectors based on the material cadmium zinc telluride (CdZnTe) could potentially meet this need if certain material deficiencies are addressed. The coplanar-grid as well as other electron-only detection techniques are effective in overcoming some of the material problems of CdZnTe and, consequently, have led to efficient gamma-ray detectors with good energy resolution while operating at room temperature. At the present time, the performance of these detectors is mainly limited by the degree of uniformity in electron generation and transport. Despite recent progress in the growth of CdZnTe material, small variations in these properties remain a barrier to the widespread success of such detectors. Alphaparticle response characterization of CdZnTe crystals fabricated into simple planar detectors provides an effective tool to accurately study such variations. We have used a finely collimated alpha source to produce two-dimensional maps of detector response. For a number of crystals, a clear correlation has been observed between their alpha response maps and the distribution of tellurium inclusions inside the crystals. An analysis of the induced charge signals indicates that regions of enhanced electron trapping are associated with the inclusions, and that these regions extend beyond the physical size of the inclusions. Such regions introduce non-uniform electron trapping in the material that then degrades the spectroscopic performance of the material as a gamma-ray detector.2

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electron trapping nonuniformity in high-pressure-Bridgman-grown CdZnTe

Amman

Lee

Luke

2002

Journal of Applied Physics

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“…An alternative to scintillator type detectors are cadmium zinc telluride (CZT) detectors. These are a variant of semi-conductor radiation detectors, which use the ionization of the semi-conductor by the incident gamma radiation and subsequent movement of the produced electron hole pairs to opposing electrodes in order to produce electrical pulses (similar to gas ionization methods [Luke 1995]). Such pulses are detected, and processed to produce a gamma spectrum.…”

Section: Detector Systems In Uav Radiometric Surveysmentioning

confidence: 99%

“…A further advantage of CZT is that the material can be manufactured into different shapes, for example co-planar grids and small pixel detectors to optimize for differing applications. This therefore improves detection characteristics (Table 2) (Luke et al 2001;Luke 1995;Wilson et al 2011), however the co-planar grid variation produces the best energy resolution of any of the detectors previously discussed (<2.5% at 662 keV) (Chen et al 2008;Martin et al 2015;Sellin 2003;Zhang et al 2013), allowing for the production of the most resolved energy spectrum and hence the most confident identification of individual radionuclides (although Table 2 indicates that this could still be improved upon). Despite this high resolution, problems with the uniformity of the crystal structure, such as random grain boundaries, have limited its effectiveness by causing charge trapping -reducing the counting efficiency in certain applications and limiting the volume of the detectors to small sizes, i.e.…”

Section: Detector Systems In Uav Radiometric Surveysmentioning

confidence: 99%

Airborne radiation mapping: overview and application of current and future aerial systems

Connor

Martin

Scott

2016

International Journal of Remote Sensing

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Nuclear power and associated activities are never far from scrutiny, the apparent advantages of the technology are juxtaposed by the risk of incidents perceived as being catastrophic. If a major nuclear incident was to occur, an important aspect of the response management to any radionuclide release would be the need to rapidly establish the spatial distributions and quantities of these released radionuclides, their type in addition to their corresponding activity. The data received from surveys would directly inform evacuation plans, on-site incident management strategies as well as protecting both workforce and public from harm. The disaster at the Fukushima Daiichi Nuclear Power Plant in 2011 is perhaps the best example of the requirement for real time data collection to inform crucial decisions. Previous reviews of the event have observed that because the static on-site radiation detector network was destroyed by the 15 m high tsunami (following the magnitude 9.0 Great Tōhoku earthquake), it was not possible to immediately determine the radionuclide activity in the area and the danger presented to the responding workforce. Such preceding works have retrospectively highlighted the usefulness of unmanned aerial systems in providing real-time data within nuclear and non-nuclear settings. The establishment of an arbitrary 20 km exclusion zone surrounding the Fukushima Daiichi plant, with the displacement of over 150,000 people, has been viewed by many as an over-reaction -with many not having been required to be evacuated. This review examines and evaluates the previous as well as current work on aerial radiation monitoring and the future improvement that might be delivered by a combined three-dimensional (3D) radiation mapping platform. Combining detailed 3D topographical mapping with radiation surveying has powerful implications for the way that radiological contamination across a site might be measured and displayed in the future, both following radiological release events and in routine site monitoring. • Comprehensive review of airborne radiation mapping.• Exploration of potential future systems.• Comparison of the multiple flight, mapping, and detection systems.• Application of devices to a range of scenarios.

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“…Coplanar and P-I-N advanced designs are currently under investigation to improve energy resolution [8,9,10]. In the coplanar design, grids are formed on one side of the detector which collect carriers of one polarity efficiently, improving the energy resolution.…”

Section: Introductionmentioning

confidence: 99%

Performance of P-I-N CdZnTe Radiation Detectors and Their Unique Advantages

et al. 1997

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We present the performance characteristics of CdZnTe radiation detectors with a new P-I-N design and their unique advantages over metal-semiconductor-metal (M-S-M) devices. In M-S-M CdZnTe detectors the bulk resistivity of the substrate largely determines the leakage current. High leakage current is a dominant noise factor for CdZnTe detector arrays, coplanar detectors, and detectors used for low X-ray energy applications. P-I-N devices provide low leakage currents. Early CdZnTe detectors exhibited polarization, were limited to small detection volumes, and some required high deposition temperatures. We have developed a new heterojunction design which can be deposited at low temperatures so that even high-pressure Bridgman CdZnTe can be used. Using the P-I-N design, CdZnTe detectors with high detection volumes (>200 mm 3 ) were fabricated and exhibited low leakage current, good energy resolution, and no polarization. These detectors have significant advantages over M-S-M detectors in three specific areas. First, X-ray fluorescence studies require detectors with low leakage currents to provide less spectral broadening due to electronic noise. Second, less expensive vertical Bridgman CdZnTe material can be used for imaging applications since it normally possesses too low of a bulk resistivity to be useful as a M-S-M detector. Third, leakage currents across the anode grid in large volume coplanar detectors can be significantly reduced. INTRODUCTIONCompound semiconductors such as CdTe and HgI 2 have been investigated for room temperature gamma-ray detection since they have a high average atomic number (resulting in large attenuation coefficient) and a wide bandgap (which enables room temperature operation). However, major issues such as poor charge collection efficiency and non-ideal ohmic contacts have limited their potential. In CdTe, deep traps reduce the mobility-lifetime product (jIt') of holes causing long low-energy tails, leading to poor energy resolution. Poor charge collection also limits the detection volume. Increasing bias will improve the energy resolution; however, CdTe's low resistivity (10' ohm-cm) and M-S-M design prevent operation at high bias due to high leakage current [1,2].A significant advancement in radiation detector technology has been the development of CdZnTe alloys by the high pressure Bridgman (HPB) technique [3,4,5]. CdTe with Zn (in the range of 4 to 20% Zn) increases the resistivity to mid 10'0 ohm-cm. This improves the overall performance of the device, but there are still problems with low energy tailing and poor peak-tovalley ratios in large volume detectors. The electron gt product does not improve, and the hole ýiv product decreases when adding Zn; deep traps still limit the energy resolution and detection volume.Several approaches such as thermoelectric cooling, improved pulse processing methods, and new device designs are being researched to improve detector energy resolution [6,7,8].

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Unipolar charge sensing with coplanar electrodes-application to semiconductor detectors

Cited by 328 publications

References 6 publications

Electron trapping nonuniformity in high-pressure-Bridgman-grown CdZnTe

Electron trapping nonuniformity in high-pressure-Bridgman-grown CdZnTe

Airborne radiation mapping: overview and application of current and future aerial systems

Performance of P-I-N CdZnTe Radiation Detectors and Their Unique Advantages

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