Present Status of the Dual-Sided Microstructured Semiconductor Neutron Detector (DS-MSND) and Instrumentation

Dual-Sided Microstructured Semiconductor Neutron Detectors (DS-MSNDs) are continually being developed as a compact, low-power, high-efficiency alternative to ³He for thermal-neutron detection. DS-MSNDs are fabricated from 1.5-mm thick, 5 kOhm-cm resistivity, silicon wafers. Deep trenches are etched into both sides of the silicon substrate with the back-side trenches offset from the front-side trenches to eliminate neutron free streaming paths through the silicon fins. A pvp-type vertical diode is formed within the trench microstructures on both sides of the substrate. The trenches are then backfilled with ⁶LiF powder with powder-packing fractions as high as 55%. Incident neutrons are absorbed by ⁶Li atoms, which then fission and emit charged-particle reaction products that can deposit energy in the adjacent silicon fins. Electron-hole pairs created by the charged particle interactions are then drifted, and the current induced in the electrodes is integrated to form a voltage pulse that can be counted. So far, DS-MSNDs have achieved detection efficiencies as high as 69.3%. The present work describes efforts to improve the signal-to-noise ratio of the DS-MSNDs to increase the gamma-ray rejection ratio of the detectors. Silvaco TCAD simulations indicate alternative doping profiles can improve the charge-collection efficiency and produce single polarity pulses regardless of interaction location, whereas the polarity of the previously reported DS-MSND pulse was dependent on the location of the neutron interaction. Newly fabricated DS-MSNDs will be used to populate Modular Radiation Detectors (MRD) which will be integrated into a high-sensitivity Reconfigurable Wearable Detector (RWD). In addition to neutron detection, the MRDs will incorporate a high energy-resolution gamma-ray spectrometer for gamma-ray source detection and identification. The RWD will be a highly versatile, low cost, low power, tool for the search, localization, and identification of radioactive material.