Impact of 700keV Ni++ ion irradiation on structural and optical properties of GaN

In this paper, we present the effects of high-energy Ni++ ion irradiation on the structural and optical properties of GaN films. Three different irradiation doses of 1013, 1014, and 1015 ions/cm2 were used while keeping the ion energy at 700keV. The irradiation induced structural and optical changes in GaN films were measured using X-ray diffraction (XRD) and UV-Vis spectroscopy. The XRD measurements on irradiated films discovered several extra peaks in the XRD spectrum compared with the as-grown GaN film indicating the formation of new phases or defects in the GaN film due to the ion irradiation. The intensity of these extra peaks increases with increasing ion dose, suggesting that the density of defects in the GaN film also increases with increasing ion dosage. The UV-Vis measurements revealed a decrease in the bandgap of the irradiated GaN films from 3.40 eV for the pristine GaN film to 3.26 eV for the film irradiated with highest dose of 1015 ions/cm2. The decrease in bandgap can be attributed to the creation of defects and/or the formation of new phases in the GaN film due to the ion irradiation.