Influence of top contact topology on detection properties of semi-insulating GaAs detectors

Results are presented of an experimental study of detectors based on LEC SI GaAs with various top Schottky contact arrangements. The study is concentrated on an improvement of relative detection efficiency, as an important detection property of detectors considered for application in digital radiography. The current-voltage and pulse height spectra measurements at 295 K using 241Am and 57Co gamma sources are demonstrated. Following the application of the detectors in digital radiology systems, the detector properties, such as leakage current, breakdown voltage, charge collection efficiency, relative energy resolution, peak to valley ratio, and relative detection efficiency are evaluated. Improvement of overall detector properties with decreasing top contact area ('small pixel effect') is presented, and consequently it is shown that the connecting of more pixels into the top contact led to an increase of the relative detection efficiency