Characterization of 600-μm-thick SI-GaAs detectors for medical imaging

We present results of an experimental study concerning different semi-insulating GaAs (SI-GaAs) detectors of thickness 600 μm, aimed at testing their performance in terms of leakage current, breakdown voltage, charge collection efficiency (CCE) and energy resolution (ΔE/E), in view of their possible application to digital imaging in radiology and nuclear medicine. We have investigated the detection performance of detectors with different sizes of the Schottky contact pad (0.2–1.0 mm), using different gamma radioactive sources (241Am, 131Ba and 152Eu with peak energy 60, 81 and 122 keV, respectively) and a laser source (λ=813 nm, pulse width=43 ps, pulse energy 4 pJ). CCE values up to 80% and minimum ΔE/E of 6% at 60 keV were observed. For SI-GaAs Schottky diodes, evidence of the dependence of electrical and spectroscopic performance on the side of the pixel (“small pixel effect”) is presented.