A relation between yellow band and defect states of GaN epilayers during gamma-ray irradiation with different doses

Abstract

GaN epilayers grown on c-plane sapphire substrates were irradiated with different doses of gamma-rays ranging from 300 to 3000 krad. From the photoluminescence (PL) measurement, the yellow PL (YL) intensity decreased with increasing the gamma-ray irradiation dose. From the deep level transient spectroscopy (DLTS), three defect states of E1, E2, and E5 levels with activation energies of 0.17 +/- 0.02, 0.52 +/- 0.01, and 0.97 +/- 0.02 eV below the conduction band edge were found in the samples. The E1, E2, and E5 levels originated from the defects of nitrogen vacancy (VN), nitrogen antisite (NGa), and interstitial nitrogen (Ni), respectively. With increasing gamma-ray doses, the Nt value of NGa was increased, while the Nt values of VN, Ni, VGa-Ni complex decreased. Therefore, it was suggested that the yellow PL band originated from the VGa-Ni complex.

GaN epilayers grown on c-plane sapphire substrates were irradiated with diferent doses of γ-rays ranging from 300 to 3000 krad. From the photoluminescence (PL) measurement, the yellow PL (YL) intensity decreased with increasing the γ-ray irradiation dose. From the deep level transient spectroscopy (DLTS), three defect states of E1, E2, and E5 levels with activation energies of 0.17±0.02, 0.52±0.01, and 0.97±0.02 eV below the conduction band edge were found in the samples. The E1, E2, and E5 levels originated from the defects of nitrogen vacancy (VN), nitrogen antisite (NGa), and interstitial nitrogen (Ni), respectively. With increasing γ-ray doses, the Nt value of NGa was increased, while the Nt values of VN, Ni, VGa–Ni complex decreased. Therefore, it was suggested that the yellow PL band originated from the VGa–Ni complex.