Micro-Raman and photoluminescence studies of neutron-irradiated gallium nitride epilayers

GaN epilayers grown on sapphire substrate were irradiated with various dosages of neutrons and were characterized using Micro-Raman and photoluminescence. It was found that the A(1)(LO) peak in the Raman spectra clearly shifted with neutron irradiation dosage. Careful curve fitting of the Raman data was carried out to obtain the carrier concentration which was found to vary with the neutron irradiation dosage. The variation of the full width at half maximum height of the photoluminescence was consistent with the Raman results. The neutron irradiation-induced structural defects (likely to be Ge-Ga) give rise to carrier trap centers which are responsible for the observed reduction in carrier concentration of the irradiated GaN. (c) 2005 American Institute of Physics.