  It is the hybrid pixel detector technology which brought to the X-ray imaging
a low noise level at a high spatial resolution, thanks to the single photon
counting. However, silicon as the most widespread detector material is
marginally sensitive to photons with energy more than 30 keV. That's why the
high-Z alternatives to silicon such as gallium arsenide and cadmium telluride
are increasingly attracting attention of the community for the development of
X-ray imaging systems in recent years. We present in this work the results of
our investigations of the Timepix detectors bump-bonded with sensors made of
gallium arsenide compensated by chromium (GaAs:Cr). The properties which are
mostly important from the practical point of view: IV characteristics, charge
transport characteristics, operational stability, homogeneity, temperature
dependence as well as energy and spatial resolution are considered.
Applicability of these detectors for spectroscopic X-ray imaging is discussed.
