Thin-film-coated bulk GaAs detectors for thermal and fast neutron measurements

GaAs-based structures are presently under investigation as the substrate for 10B-coated and polyethylene-coated neutron detectors. The semi-insulating (SI) GaAs-based devices operate at low bias voltages by employing the truncated electric field effect, which allows for acceptable signals to be produced with bias voltages ranging between 10 and 50 V. At this time, the 10B-coated devices have demonstrated over 3.5% intrinsic thermal neutron detection efficiency with reactive films 1.8 μm thick. Relatively high neutron/γ-ray rejection ratios can be achieved with an appropriate choice of lower level discriminator setting. Polyethylene-coated GaAs devices are being studied as fast neutron detectors and have shown evidence of (n,p) reactions for 14 MeV neutrons. Theoretical neutron responses and experimental neutron detection data are presented and compared.