AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base, Ohio APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED ELECTRON PARAMAGNETIC RESONANCE SPECTROSCOPY AND HALL EFFECT STUDIES OF THE EFFECTS OF LOW ENERGY ELECTRON IRRADIATION ON GALLIUM NITRIDE (GAN)

Irradiation effects on the wide-bandgap semiconductor material GaN are of interest to the USAF due to this material’s applicability for a wide range of on-orbit uses. Irradiation is also a valuable tool in analyzing the damage and defect formation dynamics of the material which is of great use in determining and correcting deficiencies in material growth processes. GaN samples representing several different growth methods and doping profiles were irradiated by 1.0 – 1.5 MeV electron beams to induce defects such as vacancies and interstitial atoms in the material. Following irradiation, the samples were analyzed using Electron Paramagnetic Spin Resonance (EPR) spectroscopy to determine effects of the irradiation, with particular attention to the effects of irradiation on the shallow donors in the material. EPR allows the direct inspection of paramagnetic impurity or defect sites, providing information on site density as well as, in some cases, identity. Samples subjected to EPR analysis prior to irradiation show a strong signal attributed to the shallow donor in GaN that is without resolved hyperfine structure. Following lowtemperature irradiation with 1.0 MeV electrons to a total dose of approximately 40 MRad (GaN), the same samples showed a marked decrease in the shallow donor signal and the introduction of a broad EPR signal with resolved hyperfine structure. The decrease in the shallow donor signals is attributed to the formation of a deep band-gap complex of the nitrogen interstitial with the shallow donor sites, perhaps in