SEMIINSULATING BULK GAAS AS A SEMICONDUCTOR THERMAL-NEUTRON IMAGING DEVICE

Thermal-neutron Schottky barrier detector arrays fabricated from semi- insulating bulk GaAs are presently being tested. The devices use a fil m of B-10 to convert the incident thermal-neutron field into cr, parti cles and lithium ions, either of which interact in the detector. Bulk GaAs Schottky barrier detectors are relatively radiation hard to therm al neutrons and gamma rays and have shown reasonably good energy resol ution for alpha particles. Additionally, reverse biased radiation dete ctors fabricated from semi-insulating bulk GaAs have been shown to hav e truncated electric field distributions, resulting in the formation o f a high field active region and a considerably lower field dead regio n. The device is sensitive only to electron-hole pairs excited in the high field region, thus the truncated field effect is advantageous as an inherent gamma-ray discrimination feature for neutron detectors. Pr eliminary results show no indication of device degradation after over 2400 hr in a thermal-neutron beam from a reactor. Images have been for med of 1, 1.5, and 2 mm holes and crosses from 2 mm thick Cd templates .