Evaluation of freestanding GaN as an alpha and neutron detector

The wide bandgap (3.39) eV and large dislocation energy of the III–V semiconductor gallium nitride (GaN) make this a desirable material for charged particle spectroscopy in high temperature, high radiation environments. While other research groups have established that charged particle detectors can be fabricated from high quality, thin films of molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) grown GaN, this work demonstrates the feasibility of ionizing radiation detectors created from significantly thicker freestanding n-type GaN, grown via hydride vapor phase epitaxy (HVPE). Detectors were fabricated by depositing Ni/Au pads on n-type GaN, forming a Schottky barrier diode. Capacitance–voltage measurements on the detectors showed an intrinsic carrier concentration in the range of 10−16 cm−3–10–15 cm−3, and indicated an inhomogeneous distribution between diodes on the same wafer. The radiation sensitivity of the fabricated detectors was analyzed using alpha particles from an 241Am source. Charge collection efficiency (CCE) calculations from these experiments indicate an efficiency of 100 percent. The detectors were also successfully used to detect neutron induced charged particles using a Li2O foil in a neutron beam.