Performance of semi-insulating gallium arsenide X-ray pixel detectors with current-integrating readout

First images are presented from tests of a semi-insulating gallium arsenide X-ray imaging detector, flip-chip bonded to a current integrating CMOS readout chip. The detector is designed for applications in synchrotron X-ray imaging. The X-ray sensing part of the detector consists of a 150 μm thick GaAs photodiode containing an array of 92×100 pixels, each 150 μm by 150 μm in size. Operating the device at −20°C we have obtained a map of detector dark current, which is typically in the range 0.4 pA to 0.8 pA/pixel. We have also obtained images of the detector response to a collimated X-ray beam.