X-ray response of epitaxial GaAs

We summarize the results of a number of x-ray experiments on an epitaxial GaAs device carried out in both our laboratory and the Physikalisch-Technishe Bundesanstalt radiometry Laboratory at the Berliner Elektronenspeicherring-Gesellschaft fur Synchrotronstrahlung Synchrotron Radiation Source. The detector has a diameter of 1.5 mm and is fully depleted to a depth of 40 mu m. It has been characterized as a function of energy, bias, and temperature. At -35 degrees C we determine the charge collection efficiency to be 97% and find that energy resolutions ranging from 730 to 930 eV full width at half maximum (FWHM) can be readily achieved using conventional pre-amplifiers over the energy range 6-60 keV. By considering the various contributions to the FWHM, we show that leakage current and charge trapping noise dominate the resolution function. From detector modeling we determine the effective electron and hole density/cross section products to be 7 and 3 cm(-1), respectively. (C) 1999 American Institute of Physics. [S0021-8979(99)06211-8].