Li-based semiconductor materials represent a promising alternative to 3-He and scintillation materials for thermal neutron detection and imaging instruments. Semiconductor crystals of LiInSe2, LiInP2Se6, and LiGaInSe2 (LiGa0.5In0.5Se2) were grown using natural and enriched lithium (6Li). The materials were characterized for electronic and optical properties including optical transmission, current-voltage (I-V) characteristic for resistivity, and bandgap. Thermal neutron detectors were fabricated and characterized for neutron and gamma-ray response. Pulse height spectra were collected from a moderated custom-designed 241AmBe neutron source and a 60Co gamma-ray source. The LiInSe2 samples exhibited a 2.8 eV cutoff in the optical spectrum and a resistivity of ~8×1011 Ω·cm. LiInSe2 devices exhibit a noise floor of <30 keV which operated at a field of 630 V/mm, for the 0.8-mm thick device. The Vertical Gradient Freeze (VGF) grown LiInP2Se6 samples exhibited a 2.2 eV cutoff in the optical spectrum and resistivity of ~4×1012 Ω·cm. The Chemical Vapor Transport (CVT) grown LiInP2Se6 devices exhibit a noise floor of <60 keV which operated at a field of 8,000 V/mm, for the 0.05- mm thick device. Furthermore, the long-term stability of LiInSe2 devices during multiple weeks under continuous bias was investigated.
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