Fast Neutron & Gamma-Ray Scintillation and Broadband Photoluminescence from Gallium Nitride & Gallium Oxide: Developing Radiation-Hard Diagnostic Platforms

Integrated scintillation and electronics processing materials are of critical importance in environments exposed to high levels of radiation, such as nuclear fusion diagnostics and space missions. This dissertation focuses on the radiation detection capabilities of gallium oxide (Ga2O3) and gallium nitride (GaN), exploring their responses to fast neutrons and gamma rays. Using high-energy neutron beam facilities at Los Alamos Neutron Science Center (LANSCE) Flight Path 4FP60R, we exposed both Ga2O3 and GaN crystals to neutron irradiation spanning an energy spectrum ranging from 1 to 400 MeV. A Pi-Max 4 fast-gated Intensified CCD (ICCD) camera captured the transient scintillation responses for both materials, revealing fast rise and energy-dependent scintillation intensities. By quantifying neutron spectral flux using a fission chamber with U-238 fission foil, we analyzed the temporal and energy-dependent characteristics of the scintillation events. Ga2O3 exhibited a scintillation by gamma flash, with a ~5 ns full width at half maximum (FWHM) decay following neutron beam pulses, demonstrating its rapid response to high-energy gamma photons. GaN similarly showed strong scintillation responses, with both materials displaying energy-dependent patterns that correlated with neutron energy through time-of-flight (TOF) measurements. Sealed source calibration tests using Californium-252 and Yttrium-90 provided further insights into the temporal responses of Ga2O3 under mixed neutron and gamma radiation environments. Our findings indicate that both Ga2O3 and GaN exhibit high scintillation efficiencies and fast temporal responses, showing promise in optical and electrical dual-mode detection for gamma and neutron radiation. These results position Ga2O3 and GaN as highly suitable candidates for advanced radiation detection systems, underscoring their potential for future applications in nuclear and aerospace fields.