ABSTRACT
This chapter presents the characterization and application of high-resistivity, chromium compensated gallium arsenide (GaAs:Cr), a semiconductor sensor material that recently has (re-)gained increasing attention. This material shows detector-grade properties and thus is well suitable to be used for x-ray detectors. The chapter is divided in three parts: First, a detailed characterization of the material properties of GaAs:Cr with respect to its use as a sensor material for photon-counting x-ray pixel detectors (homogeneity, resistivity, charge carrier properties) is performed. Then, it describes the fabrication steps of GaAs:Cr Medipix detector assemblies as well as the functionality of the Medipix3RX photon-counting readout electronics. Finally, it investigates the performance of these detectors with respect to (spectral) x-ray imaging. One of the advantages of photon-counting semiconductor pixel detectors is that the possibility of setting one/more energy threshold(s) allows making use of the energy information contained in the recorded x-ray spectrum for the so-called spectral x-ray imaging or spectral CT.
