Defects and radiation damage in semi-insulating GaAs radiation detectors

Thermally stimulated current (TSC) and depolarisation (TSD), measurements and detailed analysis of current - voltage (I-V) characteristics have been made on semi-insulating GaAs (SI-GaAs) Schottky diode particle detectors, fabricated on substrates from several suppliers, before and after irradiation with high-energy protons and pions. The analysis of I-V characteristics allows the determination of the barrier height and bulk resistance in detectors. Changes observed in I-V characteristics and TSC spectra after irradiation are described and a dislocation-net model of radiation-damaged devices is proposed. The deep level and trap spectra were compared in initial and irradiated crystals from different suppliers. A comparison of recently published data of SI-GaAs before and after irradiation by different ionising radiation has been performed and radiation-induced defects and microinhomogeneities have been analysed. Electric field effects in the I-V characteristic quasi-saturation region have been investigated and a model of free carrier lifetime thermal quenching is proposed. The influence of an electric field on light absorption in EL2 centres has been investigated at different temperatures.