Damage accumulation and structural modification in a- and c-plane GaN implanted with 400-keV and 5-MeV Au+ ions

c-plane (0001) and a-plane (11-20) gallium nitride (GaN) epitaxial layers were grown by Metal organic Vapour Phase epitaxy (MOVPE) on sapphire and subsequently implanted with 400-keV and 5-MeV Au+ ions using fluences 5 × 1014 to 5 × 1015 cm-2. The shallow Au depth profiling was accomplished by Rutherford backscattering spectrometry. The structural changes during implantation and subsequent annealing were characterised by Rutherford backscattering spectrometry channelling and Raman spectroscopy. The interplay between nuclear and electronic stopping, influencing defect accumulation, was monitored and discussed depending on GaN orientation. Post-implantation annealing induced a structural reorganisation of the GaN structure depending on the ion-implantation fluence, ion energy, and on the crystallographic orientation.