Radiation Response of a Semi-insulating GaAs Semiconductor Detector for Charged Particle at Variable Operating Temperature

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GaAs is a wide band gap semiconductor (1.42 eV) with potential use as a room temperature radiation detector. We have studied the radiation response of a prototype semiconductor detector by using a undoped semi-insulating (SI) GaAs wafer. The properties of the GaAs wafer are a resistivity of 10 ohm-cm, an orientation of (100) and a diameter of 50.8mm. The dimensions of the GaAs SI detectors were about 5x5 mm with a 350 um thickness. Prior to a metallization process, the surfaces of the GaAs wafer were cleaned by a solvent and rinsed with de-ionized (DI) water, and the removal of an oxidation layer by a diluted acid solution was performed. Metal/semiconductor contacts on the surface were fabricated by using a thermal evaporator in a high vacuum condition. The prototype GaAs detector had circular metal contacts of Ni/Au at each side and the diameter of a circular contact was 3 mm. The current-voltage characteristics of GaAs semiconductor detector were measured by using HP parameter analyzer with voltage sources. We measured the leakage currents at different temperature conditions. Also, the radiation response was evaluated by Am-241 source at variable operating temperature.