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 x 320 mu m(2) and thickness of 5 mu m, realized by molecular beam epitaxy, have been de signed and tested with X- and gamma rays, No significant charge trappi ng effects have been observed, and a charge collection efficiency of 1 00% 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 2 43 K, the electronic noise is reduced to 373 eV FWHM, and the K-alpha and K-beta lines of the Fe-55 spectrum can be resolved, The Fano facto r for GaAs has been measured at room temperature with 59.5 keV photons yielding F = 0.12 +/- 0.01.