Development of compound semi-conductor arrays for X- and Gamma ray spectroscopy

We present preliminary results of X-ray measurements on three small format compound semiconductor arrays. The devices, a 4 x 4 pixel GaAs array fabricated on 325 mum epitaxial material, a. 4 x 4 pixel CdZnTe array fabricated on a 4 x 4 x 1 mm(3) mono crystal and a 3 x 3 TlBr array fabricated on a 2.7 x 2.7 x 1.0 mm(3) mono crystal. The pixel size for all arrays is 350 x 350 mum(2). Results are presented of Fe-55 and Am-241 measurements at 5.9 keV and 59.54 keV. For detector temperatures < +5degreesC typical FWHM energy resolutions of 410 eV, and 600 eV at 5.9 keV and 640 eV and 1.4 keV at 59.54 keV were recorded for the GaAs, and CdZnTe arrays, respectively. Unlike the GaAs and CdZnTe arrays, the TlBr array showed a much wider variation in pixel performance and was difficult to operate with all pixels at a common bias. For example, biasing the detector so that all pixels worked within the operating envelope of the preamplifiers resulted in average energy resolutions of 20 keV at 59.54 keV. However, optimizing the operating conditions of individual pixels resulted in a marked improvement to - 2 keV.