Solid-state neutron detectors based on thickness scalable hexagonal boron nitride

This paper reports on the device processing and characterization of hexagonal boron nitride (hBN) based solid-state thermal neutron detectors, where hBN thickness varied from 2.5 to 15 microns. These natural hBN epilayers (with 19.9% B-10) were grown by a low pressure chemical vapor deposition process. Complete dry processing was adopted for the fabrication of these metal-semiconductor-metal (MSM) configuration detectors. These detectors showed intrinsic thermal neutron detection efficiency values of 0.86%, 2.4%, 3.15%, and 4.71% for natural hBN thickness values of 2.5, 7.5, 10, and 15 microns, respectively. Measured efficiencies are very close (more than 92%) to the theoretical maximum efficiencies for corresponding hBN thickness values for these detectors. This clearly shows the hBN thickness scalability of these detectors. A 15-micron thick hBN based MSM detector is expected to yield an efficiency of 21.4%, if enriched hBN (with ~100% B-10) is used instead of natural hBN. These results demonstrate that the fabrication of hBN thickness scalable highly efficient thermal neutron detectors is possible.