2 MeV proton radiation damage studies of gallium nitride films through low temperature photoluminescence spectroscopy measurements

Abstract

Gallium nitride (GaN) thin film samples were grown by ammonia-molecular beam epitaxy. Through room temperature transport measurements, electron mobilities of 560 cm/sup 2//Vs were observed for layers with a carrier density of 1.5/spl times/10/sup 17/ cm/sup -3/. Room temperature photoluminescence (PL) spectroscopy revealed the bound exciton transition at 363.0 nm and a weak yellow emission whose intensity was sample dependent. At 22 K, the main photoluminescence signal sharpened, shifted to 356.9 nm (3.474 eV), and the maximum intensity increased by a factor of one hundred; the intensity of the yellow emission decreased. The samples were irradiated at room temperature with 2 MeV protons at fluences of 10/sup 9/, 10/sup 10/, 10/sup 11/, 10/sup 12/, 10/sup 13/, 10/sup 14/, 10/sup 15/, and 10/sup 16/ cm/sup -2/. The intensity changes were within experimental error up to 10/sup 13/ cm/sup -2/. The drop in intensity of the bound exciton transition was 16% at 10/sup 14/ cm/sup -2/ and 99% at 10/sup 15/ cm/sup -2/. The radiation damage constant associated with the main PL peak at 3.474 eV in GaN is (1.4/spl plusmn/0.3)/spl times/10/sup -13/ cm/sup 2/, compared with (4/spl plusmn/1)/spl times/10/sup -11/ cm/sup 2/ associated with the main PL, peak at 1.492 eV in GaAs. For photonic applications, GaN is more robust than GaAs with respect to displacement damage.