Investigating the suitability of GaAs:Cr material for high flux X-ray imaging

Abstract

Semi-insulating wafers of GaAs material with a thickness of 500 µm have been compensated with chromium by Tomsk State University. Initial measurements have shown the material to have high resistivity (3 × 10 9 Ω cm) and tests with pixel detectors on a 250 µm pitch produced uniform spectroscopic performance across an 80 × 80 pixel array. At present, there is a lack of detectors that are capable of operating at high X-ray fluxes (> 10 8 photons s −1 mm −2 ) in the energy range 5-50 keV. Under these conditions, the poor stopping power of silicon, as well as issues with radiation hardness, severely degrade the performance of traditional detectors. While high-Z materials such as CdTe and CdZnTe may have much greater stopping power, the formation of space charge within these detectors degrades detector performance. Initial measurements made with GaAs:Cr detectors suggest that many of its material properties make it suitable for these challenging conditions. In this paper the radiation hardness of the GaAs:Cr material has been measured on the B16 beam line at the Diamond Light Source synchrotron. Small pixel detectors were bonded to the STFC Hexitec ASIC and were irradiated with 3 × 10 8 photons s −1 mm −2 monochromatic 12 keV X-rays up to a maximum dose of 0.6 MGy. Measurements of the spectroscopic performance before and after irradiation have been used to assess the extent of the radiation damage.

Characterization of chromium compensated GaAs as an X-ray sensor material for charge-integrating pixel array detectors

“…We found this point was best to balance all the positive and negative effects of temperature and voltage. Please note than many results presented by others, especially those obtained with photon counters from the Medipix family are obtained at room temperature [6][7][8][9][10].…”

Digital fast pulse shape and height analysis on cadmium–zinc–telluride arrays for high-flux energy-resolved X-ray imaging

“…Recently, great efforts have been made in the development of imaging arrays, with single-photon counting and energyresolving capabilities, for colour/spectroscopic X-ray imaging (Norlin et al, 2008;Taguchi & Iwanczyk, 2013;Tomita et al, 2004), opening new perspectives for applications within the fields of diagnostic medicine, synchrotron applications, nondestructive testing (NDT) and security screening. Energyresolved photon-counting (ERPC) arrays are typically based on high-Z and wide-band-gap direct-conversion compound semiconductors [gallium arsenide, cadmium telluride, ISSN 1600-5775 # 2018 International Union of Crystallography cadmium-zinc-telluride (CZT)] Barber et al, 2015;Iwanczyk et al, 2009;Szeles et al, 2008;Veale et al, 2014a), able to ensure room-temperature operation and higher detection efficiency than the traditional semiconductor detectors (silicon, germanium) (Del Sordo et al, 2009;Owens & Peacock, 2004;Takahashi & Watanabe, 2001). Silicon drift detectors (SDD), invented in 1984 by , are also proposed for roomtemperature spectroscopic X-ray imaging, representing the best solution up to 20 keV (Bertuccio et al, 2015).…”

Overview of GaAs und CdTe Pixel Detectors Using Medipix Electronics

“…a) The growth methods are: CZ: Czochralski (liquid encapsulated for GaAs); CVD = chemical vapor deposition; THM = travelling heater method using tellurium solution; BM = Bridgman method. The data were collected from Del Sordo, [31] Veale, [32] Toyokawa, [33] Zappettini, [34] and Nogami. [35] Table 1 summarizes the different materials and the related properties.…”