Photoluminescence properties of GaN grown under ion flux reduced condition by plasma enhanced molecular beam epitaxy

Effects of nitrogen ion irradiation on photoluminescence (PL) properties at 77 K of undoped GaN grown by plasma enhanced molecular beam epitaxy were investigated. It was found that for epitaxial layers grown under ion irradiation conditions, the PL spectra were dominated by near band-edge emission at 357 nm (3.47 eV). However, deep-level emission at around 567 nm (2.2 eV) was also observed and the intensity of which was considerably strong. On the other hand, for GaN films grown with no ion irradiation, the intensity of the deep-level emission was two orders of magnitude less than that of the near band-edge emission. This result suggests that the nitrogen ions degrade the PL properties, i.e., create defect levels relating to emission at around 567 nm (2.2 eV).