Origin of yellow luminescence in n-GaN induced by high-energy 7 MeV electron irradiation

The yellow luminescence band in high-energy 7 MeV electron-irradiated n-GaN is investigated as a function of electron irradiation dose. Both the yello w-band intensity and the near-bandedge photoluminescence (PL) intensity dec rease continually with increasing electron irradiation dose. The decrease r ate for the yellow-band intensity is less compared to the near-bandedge int ensity; however, it is found that the ratio of the yellow-band intensity to the near-bandedge PL intensity increases with increasing electron irradiat ion dose. To interpret this phenomenon. a theoretical model is developed fo r the yellow-to-near-bandedge intensity ratio based on rate equations. The proposed model is in good agreement with the experimental observation. The electron spin resonance (ESR) and light-induced ESR (LESR) spectra are meas ured to investigate deep defects induced by electron irradiation. The ESR s ignal intensity at g = 1.9451 decreases with increasing electron irradiatio n dose and increases with the light-induced time. (C) 2001 Elsevier Science B.V. All rights reserved.