High resolution X-ray spectroscopy using a GaAs pixel detector

X-ray measurements have been carried out on a single pixel of a small prototype 3×3 GaAs array. The device was fabricated from 40 μm thick hyper pure epitaxial material and has a pixel size of 100×100 μm2 with a pitch of 150 μm. Measurements from 2.3 to 27 keV were carried out at the BESSY II and ESRF synchrotron radiation facilities. A room temperature energy resolution of 380 eV FWHM at 5.9 keV was achieved and 289 eV FWHM with only modest cooling (−20°C) These are the best figures yet reported for similar devices.