Hard X-ray test and evaluation of a prototype 32×32 pixel gallium–arsenide array

We report X-ray measurements on a prototype 1.1 cm2, 32×32 GaAs pixel array with a pixel size of 350×350 μm2 produced to assess the technological feasibility of making large area, almost Fano-limited arrays, which operate near room temperature. Measurements were carried out on four widely separated pixels both in our laboratories and using monochromatic X-ray pencil beams at the HASYLAB synchrotron research facility in Hamburg, Germany. The pixels were found to be very uniform both in their energy and spatial responses. For example, typical energy resolutions of ∼280 eV at 10.5 keV, rising to ∼560 eV at 60 keV were achieved. The corresponding resolutions measured under full-pixel illumination were found to be the same within statistics, indicating uniform crystallinity and stoichiometry. Likewise, by scanning a 15 keV, 15×15 μm2 beam across the entire surface of each of the pixels, the gain uniformity across the pixels (and by implication the entire array) was determined to be statistically flat.