PL characterization of GaN nanolayer obtained by N ion implantation into Si3N4/GaAs

Photoluminescence measurements (PL) and Transmission Electron Microscopy (TEM) were employed to characterize the GaN nanolayer (similar to 70 nm) obtained by Ion Beam Synthesis (IBS). N+ ions at 50 keV were implanted up to a fluence of 3 x 10(17) cm(-2) into a GaAs (001) capped by 125 nm Si3N4 layer. N+ implantation was performed with samples held at 450 degrees C and subsequently annealed in a temperature range between 550 and 1000 degrees C for 5 min by Rapid Thermal Annealing (RTA) under N-2 flow. An amorphous GaAsN alloy is obtained at the as-implanted state, which is converted to a N-rich GaN-nanolayer only after annealing at 850 degrees C. However, the band-gap emission at 3.4 eV (FWHM = 0.63 eV) is present already in the spectrum from the as-implanted sample, and it does not significantly change in shape and intensity after any annealing temperature up to 850 degrees C. It was additionally observed three more emission bands: 2.34 eV (FWHM = 0.48 eV), 2.63 eV (FWHM = 0.34 eV) and 2.92 eV (FWHM = 0.31 eV) that might be due to V-Ga and V-Ga clusters in the N-rich GaN-nanolayer. The 850 degrees C annealing increases their intensities by factors of 1.34, 1.43, and 1.61, respectively, when compared to the as implanted sample. Therefore, the optical signature for the formation of an ion beam synthesized N-rich GaN nanolayer does not come from an increase in the band-gap emission but by an increase in the bands associated with defects. The emission from the sample annealed at 1000 degrees C is majority from the defect bands which were intensified by a factor of similar to 10.