Study of bulk semi-insulating radiation detectors: Role of ohmic contact metallization in electrical charge transport and detection performance

Current-voltage characteristics of radiation detectors structures based on semi-insulating GaAs obtained with new types of metallizations used to form quasi-ohmic contacts are dscribed. three different metals (In, Gd and Mg), having lower work function in comparison with the standard AuGeNi alloy,were used.Such contacts, which could replace standard alloyed N+ ohmic contact, show an unusual electrical chargetransport asdeduced from the measured I-V characteristics. Pulse-height spectra of Am241and Co57 radionuclide sources detected by the structures are also reported.