Performance of semi-insulating GaAs-based radiation detectors: Role of key physical parameters of base materials

In this work, the requirements of detector-grade semiconductor materials for radiation detectors, applicable in X-ray digital radiology, are identified. The study includes 12 various bulk semi-insulating (SI) GaAs single crystals grown by LEC and VGF methods, undoped and Cr-doped, obtained from 8 different suppliers. Conductivity, Hall, GDMS (glow discharge mass spectrometry), EPD (etch pit density), S-EBIC (scanning electron beam induced current), X-ray and LST (laser scattering tomography) techniques are used for the bulk SI GaAs material evaluation. The radiation detectors fabricated on these SI GaAs single crystals have been characterized by capacitance methods and their performances have been evaluated from detected pulse height spectra of 57Co. The correlation between the physical characteristics of the base materials and the performance of the detectors is demonstrated and discussed. Key detector-grade SI GaAs parameters, useful formaterial evaluation, are identified.