The effect of incremental gamma-ray doses and incremental neutron fluences upon the performance of self-biased 10B-coated high-purity epitaxial GaAs thermal neutron detectors

High-purity epitaxial GaAs 10B-coated thermal neutron detectors advantageously operate at room temperature without externally applied voltage. Sample detectors were systematically irradiated at fixed grid locations near the core of a 2 MW research reactor to determine their operational neutron dose threshold. Reactor pool locations were assigned so that fast and thermal neutron fluxes to the devices were similar. Neutron fluences ranged between 1011 and 1014 n/cm2. GaAs detectors were exposed to exponential fluences of base ten. Ten detector designs were irradiated and studied, differentiated between p-i-n diodes and Schottky barrier diodes. The irradiated 10B-coated detectors were tested for neutron detection sensitivity in a thermalized neutron beam. Little damage was observed for detectors irradiated at neutron fluences of 1012 n/cm2 and below, but signals noticeably degraded at fluences of 1013 n/cm2. Catastrophic damage was apparent for neutron fluences of 1014 n/cm2. Comparison studies also included semi-insulating bulk GaAs thermal neutron detectors. It was observed that the SI bulk GaAs Schottky barrier detectors sustained the highest fluences prior to device failure. The main cause of detector failure was determined to result from the 10B(n,α)7Li reaction product damage