A study of crystal defects in radiation detector grade semi-insulating GaAs

Crystal defects in semiconducting materials can play a crucial role in electrical parameters and performance of devices. In this work, detector grade bulk SI GaAs wafers of various producers have been examined by several characterisation techniques with the aim to compare their crystal perfection and to correlate the observed structural properties with the detecting properties of fabricated detectors. Three types of dislocation distribution by X-ray topography and etching have been identified in bulk SI GaAs materials: (i) dislocation-free, (ii) slip-like, and (iii) cellular structure. [004] rocking curves half-width have been measured to compare the overall crystal perfection of wafers, too. Microprecipitates were studied by infrared light scattering tomography. Collection efficiency and energy resolution of radiation detectors manufactured from the bulk SI GaAs wafers showed strong dependence on substrate quality. Homogeneity of the detector charge collection was investigated by the scanning EBIC.