RBS/C and TEM characterization of GaN nanolayer obtained by IBS on (001) GaAs

Abstract

Rutherford Backscattering Spectrometry in random (RBS) and aligned (RBS/C) to GaAs 001-channel, and Transmission Electron Microscopy (TEM) techniques were employed to characterize the GaN nanolayer obtained by Ion Beam Synthesis (IBS). N+ ions at 50 keV were implanted up to a fluence of 3 × 1017 cm−2 into a 001 GaAs substrate capped by 125 nm Si3N4 layer obtained by sputtering deposition. N+ implantation was performed with samples held at 450 °C, which were subsequently annealed in a temperature range between 550 and 1000 °C for 5 min by Rapid Thermal Annealing (RTA) under N2 flow. TEM demonstrated a layered structure on the as-implanted sample, with N bubbles formed at around Si3N4/GaAs interface. RBS/C analysis carried out on samples annealed at distinct temperatures revealed a threshold temperature of about 850 °C to fully convert the as-implanted layered structure into a GaN nanolayer. At this temperature and above, the GaAs implanted side of the former Si3N4/GaAs interface was converted into GaN. As a result, an underneath voids structure was also formed indicating an intense migration of Ga from deeper areas of the GaAs substrate. RBS showed results compatible with a GaN nanolayer rich in N for the 850 °C annealing, whose sample also offered canalization (χmin = 63%) along the GaAs 001-channel. However, a regression in the crystalline quality (χmin = 95%) was observed for the 1000 °C anneal.