Electrical characterization and detection performances of various semi-insulating GaAs crystals for low energy gamma-rays

In order to investigate the correlation between the electrical characteristics of the semi-insulating GaAs and its properties as a possible detector for low energy gamma-rays, the authors have measured, for various materials, the forward and the reverse I-V characteristic, the capacitance as a function of the frequency at various bias voltages and the capacitance as a function of the bias voltage at various frequencies. To measure the charge collection efficiency, the energy resolution and the detection efficiency as a function of the bias voltage the crystals have been irradiated with 22, 60, 88 and 122 keV photons. The results are discussed and a comparison between materials from various factories of different thickness and equipped with different contacts is also presented