¹⁰B Conformal Doping for Highly Efficient Thermal Neutron Detectors

This paper reports a simple and novel conformal doping strategy for microstructured silicon diodes using enriched ¹⁰B for sidewall doping while enabling enhanced neutron sensitivity. Monte-Carlo nuclear particle (MCNP) code simulations were initially used to calculate the neutron detection efficiency in the microstructured diodes as a function of geometry and pitch. A high-temperature anneal in ¹⁰B-filled diodes results in a conformal silicon p⁺ layer along the side walls of the trenches in the diodes. This results in large neutron detection areas and enhanced neutron detection efficiency when compared with planar detectors. With the method discussed here, a thermal neutron detection of ∼21% efficiency is achieved, which is significantly higher than the efficiency achieved in planar detectors (∼3.5%). The higher efficiency is enabled by the ¹⁰B acting as a source for conformal doping in the trenches, resulting in lower leakage current while also enabling neutron sensitivity in the microstructured diodes.