GaAs Pixel Detectors
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GaAs Pixel Detectors A. Tyazhev1, D. Budnitsky1, D. Mokeev1, V. Novikov1, A. Zarubin1, O. Tolbanov1, G. Shelkov2, E. Hamann3,4, A Fauler3, M. Fiederle3,4, S. Procz3 1
Tomsk State University, 634050, Tomsk, Russia. Joint Institute for Nuclear Research, 141980, Dubna, Russia. 3 FMF, Albert-Ludwigs-University Freiburg, 79104, Freiburg, Germany. 4 IPS, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany. 2
ABSTRACT Results of investigation of X-ray sensors on the basis of GaAs compensated with chromium (HR GaAs) are presented in this work. HR GaAs material is shown to have the following physical parameters: the resistivity about 1GOhm*cm, the nonequilibrium charge carrier lifetime – hundreds of nanoseconds. Prototypes of microstrip and array HR GaAs sensors have been manufactured and tested. It is demonstrated that the sensors provide spatial resolution according to the pixel pitch and allow obtaining high quality X-ray images. INTRODUCTION The main development trends in modern X-ray imaging systems, in particular, X-ray microtomographs, XRF and XRD equipment, are the following: • decrease in dimensions towards desktop system manufacture; • application of large area array detectors operating in photon counting mode; • integration of functions of the X-ray tomograph and the X-ray fluorescent analyzer; • implementation of “pseudo-coloring” function in order to improve the object image sensing; • reduction of time expenditures need for 3D-image obtaining by means of the use of highspeed response X-ray detector arrays, high-performance computers and fast data processing algorithms; Use of a spectrometry detector operating in the single photon counting mode enables processing of only photons with the energies in the given range. This significantly improves signal-to-noise ratio as compared to electronics performing in the integrating mode, particularly to CCD array electronics. Due to the absence of the dark current accumulation by the multiplexer integrating capacitor, there is no need for the detector strong cooling what simplifies the device construction. Compliance with the main development trends of modern X-ray systems is achieved, first of all, by enhancement of radiation detecting systems through the use of semiconductor array detectors. The range of requirements to a semiconductor material is quite large: high atomic number, a high value of the product of the charge carrier mobility by their lifetime, high resistivity, the thick sensitive layer, low dark current at room temperature, a possibility of fabrication in the form of big diameter wafers etc. It has been shown previously [14] that gallium arsenide compensated with chromium is a promising material for the
semiconductor detector manufacture in the case of X-ray photon energy range 15-60keV. Results of studies of line and array gallium arsenide detectors with the sensitive layer thickness 250500µm performing in the integrating and counting mode are presented in the herein work. EXPERIMENT High Resistive GaAs:Cr wafers Unlike the well
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