Pixel X-ray detectors in epitaxial gallium arsenide with high-energy resolution capabilities (Fano factor experimental determination)

Gallium Arsenide pixel detectors with an area of 170/spl times/320 /spl mu/m/sup 2/ and thickness of 5 /spl mu/m, realized by molecular beam epitaxy, have been designed and tested with X- and /spl gamma/ rays. No significant charge trapping effects have been observed, and a charge collection efficiency of 100% has been measured. At room temperature an energy resolution of 671 eV full width at half maximum (FWHM) at 59.54 keV has been obtained, with an electronic noise of 532 eV FWHM. With the detector cooled to 243 K, the electronic noise is reduced to 373 eV FWHM, and the K/sub /spl alpha// and K/sub /spl beta// lines of the /sup 55/Fe spectrum can be resolved. The Fano factor for GaAs has been measured at room temperature with 59.5 keV photons yielding F=0.12/spl plusmn/0.01.