A study of the structural properties of GaN implanted by various rare-earth ions

Abstract

GaN layers with 〈0001〉 crystallographic orientation, grown by low-pressure metal-organic vapour-phase epitaxy (MOVPE) on c-plane sapphire substrates, were implanted with 200 and 400keV Sm+, Tm+, Eu+, Tb+ and Ho+ ions at fluencies of 1×1015–1×1016cm−2. The composition of the ion-implanted layers and concentration profiles of the implanted atoms were studied by Rutherford Back-Scattering spectrometry (RBS). The profiles were compared to SRIM 2008 simulations. The structural properties of the ion-implanted layers were characterised by RBS-channelling and Raman spectroscopy. Changes in the surface morphology caused by the ion implantation were examined by Atomic Force Microscopy (AFM). A structural analysis showed a high disorder of the atoms close to the amorphised structure at the surface layer above an implantation fluence of 5×1015cm−2 while lower disorder density was observed in the bulk according to the projected range of 400keV ions. The post-implantation annealing induced significant changes only in the Sm and Eu depth profiles; a diffusion of rare-earths implanted at a fluence of 5×1015cm−2 to the surface was observed. The annealing caused the reconstruction of the surface layer accompanied by surface-roughness enhancement.