The objective of this project is to develop and understanding of the fundamental material electronics response from a gadolinium-based GaN semiconductor device exposed to neutron radiation. The GaN Schottky diode radiation sensor has been successfully fabricated and shown alpha and beta response. Neutron spectrum using 6Li as a converter was successfully obtained. To understand devices electronic properties, the detector has been characterized by current-voltage, capacitance-voltage, charge collection efficiency, alpha spectroscopy, etc. In addition, numerical simulations using TCAD software have been performed to reveal the charge migration and to understand the fundamental material and device properties at picosecond scale. The proposed twin-detector design for gamma-ray discrimination was validated both theoretically and experimentally.