Fabrication and characterization of solid-state thermal neutron detectors based on hexagonal boron nitride epilayers

Abstract

Solid-state thermal neutron detectors with improved detection efficiencies are highly sought after for many applications. Hexagonal boron nitride (hBN) epilayers have been synthesized by metal organic chemical vapor deposition on sapphire substrates. Important material parameters including the mobility-lifetime (μτ) product and the thermal neutron absorption length (λ) have been measured. For hBN epilayers with a room temperature resistivity of 5.3×1010Ωcm, the measured μτ product of electrons is 4.46×10−8cm2/V and of holes is 7.07×10−9cm2/V. The measured λ values are 277μm and 77μm for natural and 10B enriched hBN epilayers, respectively. Metal–semiconductor–metal detectors incorporating 0.3µm thick hBN epilayers were fabricated. The reaction product pulse-height spectra were measured under thermal neutron irradiation produced by a 252Cf source moderated by high density polyethylene block. The measured pulse-height spectra revealed distinguishable peaks corresponding to the product energies of 10B and neutron reaction with the 0.84MeV 7Li peak being the most prominent. The detectors exhibited negligible responses to gamma rays produced by 137Cs decay. Our results indicate that hBN epilayers are highly promising for realizing highly sensitive solid-state thermal neutron detectors with expected advantages resulting from semiconductor technologies, including compact size, light weight, ability to integrate with other functional devices, and low cost.