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

Abstract

Photoluminescence measurements (PL) and Transmission Electron Microscopy (TEM) were employed to characterize the GaN nanolayer (~70 nm) obtained by Ion Beam Synthesis (IBS). N+ ions at 50 keV were implanted up to a fluence of 3 × 1017 cm−2 into a GaAs (001) capped by 125 nm Si3N4 layer. N+ implantation was performed with samples held at 450 °C and subsequently annealed in a temperature range between 550 and 1000 °C for 5 min by Rapid Thermal Annealing (RTA) under N2 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 °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 °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 VGa and VGa clusters in the N-rich GaN-nanolayer. The 850 °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 °C is majority from the defect bands which were intensified by a factor of ~10.