A comparison between GaAs and CdTe for X-ray imaging

Sun, G.C.; Samic, H.; Bourgoin, J. C.; Chambellan, D.; Gal, O.; Pillot, P.

doi:10.1109/tns.2004.834719

Cited by 21 publications

(12 citation statements)

References 29 publications

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“…Some new developments point in the direction of large area, either by four-side buttable CdTemodules [7] or growth of epitaxial material [8], [9]. GaAs has been fabricated in thick 4"-wafers [10], but it remains still difficult to deplete thick layers while keeping the dark current low [11].…”

Section: A Materials Properties Requirementsmentioning

confidence: 99%

Status of Direct Conversion Detectors for Medical Imaging With X-Rays

Overdick

Bäumer

Engel

et al. 2009

IEEE Trans. Nucl. Sci.

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Imaging detectors for medical X-ray and computed tomography (CT) applications have undergone many improvements and technology changes over time. But most (dynamic) detectors sold in this field still rely on indirect conversion, using scintillators and photodiodes to convert the X-ray quanta ultimately into electrical signals. Direct conversion detectors promise very high spatial resolution and high signal-to-noise ratios. Some direct conversion materials may allow for counting or even energy resolving detection of the X-ray quanta. Based on this, for example spectrally resolving CT systems are becoming an interesting option for the next decade. This contribution highlights the requirements of advanced medical X-ray and CT imaging and reviews examples of status and progress in the field. The emphasis is on the direct conversion sensors for pixelated detectors, but considerations on read-out concepts and on associated challenges such as interconnects will also be presented. Finally, the most burning issues, such as count rate limitations and polarization effects, will be discussed from an application point of view.

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Section: A Materials Properties Requirementsmentioning

confidence: 99%

Status of Direct Conversion Detectors for Medical Imaging With X-Rays

Overdick

Bäumer

Engel

et al. 2009

IEEE Trans. Nucl. Sci.

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“…For X-ray and gamma ray detection at photon energies above a few keV the stopping power of Silicon is too low and high-z materials have to be used [13]. GaAs has sometimes been proposed as a medium-Z material [14], [15], [16] but Cadmium Telluride (CdTe) and Cadmium Zinc Telluride (CZT) are the two main candidates that have been investigated since the early 1970s. However, despite recent progress [17], [18], these materials suffer from defects such as twins, subgrain boundaries, dislocations and inclusions that cause non-ideal charge transport [19], [20], [21].…”

Section: Introductionmentioning

confidence: 99%

Spectral resolution in pixel detectors with single photon processing

et al. 2013

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Pixel detectors based on photon counting or single photon processing readout are becoming popular for spectral X-ray imaging. The detector is based on deep submicron electronics with functions to determine the energy of each individual photon in every pixel. The system is virtually noiseless when it comes to the number of the detected photons. However noise and variations in system parameters affect the determination of the photon energy.Several factors affect the energy resolution in the system. In the readout electronics the most important factors are the threshold dispersion, the gain variation and the electronic noise. In the sensor contributions come from charge sharing, variations in the charge collection efficiency, leakage current and the statistical nature of the charge generation, as described by the Fano factor.The MEDIPIX technology offers a powerful tool for investigating these effects since energy spectra can be captured in each pixel. In addition the TIMEPIX chip, when operated in Time over Threshold mode, offers an opportunity to analyze individual photon interactions, thus addressing charge sharing and fluorescence. Effects of charge sharing and the properties of charge summing can be investigated using MEDIPIX3RX. Experiments are performed using both Si and CdTe detectors.In this paper we discuss the various contributions to the spectral noise and how they affect detector response. The statements are supported with experimental data from MEDIPIX-type detectors.

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“…It has a direct bandgap of 1.42 eV and shows a good X-ray absorption coefficient compared to Cadmium Telluride (CdTe) [5,6]. Both GaAs and CdTe have equivalent mobility life times (mt).…”

Section: Introductionmentioning

confidence: 99%

Orientation-dependent epitaxial growth of GaAs by current-controlled liquid phase epitaxy

Mouleeswaran

Koyama

Hayakawa

2011

Journal of Crystal Growth

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a b s t r a c tThe orientation dependence of the selective epitaxial growth of Gallium Arsenide (GaAs) has been investigated to achieve a thick epitaxial layer for application to X-ray detectors. Selective epitaxial growth was carried out on patterned GaAs with [0 1 1], [0 1 2], [0 1 0], [0 1 À 2], [0 1 À 1] and their equivalent seed orientations by current-controlled liquid phase epitaxy (CCLPE). SiO 2 was used as a mask layer to fabricate the various seed orientations on the Si-doped GaAs (1 0 0) substrate and various growth periods and current densities were considered. Solute transport in the solution was enhanced by the electromigration of solute by an applied DC electric current, which caused an incremental growth in vertical and lateral directions in all orientations. The highest vertical thickness of 268 mm in the [0 1 À 1] orientation and the largest lateral growth of 318 mm in the [0 1 2] orientation were achieved at 7.5 A cm À 2 current density for 6 h. The seed aligned in the [0 1 2] orientation was favorable for high lateral growth of GaAs. The [0 1 1], [0 1 0] and [0 1 À 2] seed orientations were suitable for application in a GaAs X-ray detector.

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A comparison between GaAs and CdTe for X-ray imaging

Cited by 21 publications

References 29 publications

Status of Direct Conversion Detectors for Medical Imaging With X-Rays

Status of Direct Conversion Detectors for Medical Imaging With X-Rays

Spectral resolution in pixel detectors with single photon processing

Orientation-dependent epitaxial growth of GaAs by current-controlled liquid phase epitaxy

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