Realization of highly efficient hexagonal boron nitride neutron detectors

We report the achievement of highly efficient B-10 enriched hexagonal boron nitride (h-(BN)-B-10) direct conversion neutron detectors. These detectors were realized from freestanding 4-in. diameter h-(BN)-B-10 wafers 43 mu m in thickness obtained from epitaxy growth and subsequent mechanical separation from sapphire substrates. Both sides of the film were subjected to ohmic contact deposition to form a simple vertical photoconductor-type detector. Transport measurements revealed excellent vertical transport properties including high electrical resistivity (> 10(13) Omega cm) and mobility-lifetime (mu tau) products. A much larger mu tau product for holes compared to that of electrons along the c-axis of h-BN was observed, implying that holes (electrons) behave like majority (minority) carriers in undoped h-BN. Exposure to thermal neutrons from a californium-252 (Cf-252) source moderated by a high density polyethylene moderator reveals that 43 mu m h-(BN)-B-10 detectors possess 51.4% detection efficiency at a bias voltage of 400 V, which is the highest reported efficiency for any semiconductor-based neutron detector. The results point to the possibility of obtaining highly efficient, compact solid-state neutron detectors with high gamma rejection and low manufacturing and maintenance costs. Published by AIP Publishing.