Damage accumulation and implanted Gd and Au position in a- and c-plane GaN

Highlights: • Defect depth profiles differ for c-plane and a-plane GaN as-implanted samples. • a-plane GaN shown lower accumulated disorder shifted into the deeper layer. • Annealing caused ion channelling recovery in a-plane compared to c-plane GaN. • Different defect complexes were created depending on GaN orientation. -- Abstract: (0001) c-plane and (11−20) a-plane GaN epitaxial layers were implanted with 400 keV Au⁺ and Gd⁺ ions using ion implantation fluences of 5 × 10¹⁴, 1 × 10¹⁵ and 5 × 10¹⁵ cm⁻². Rutherford Back-Scattering spectrometry in channelling mode (RBS/C) was used to follow the dopant depth profiles and the introduced disorder; the angular dependence of the backscattered ions (angular scans) in c- and a-plane GaN was measured to get insight into structural modification and dopant position in various crystallographic orientations. Defect-accumulation depth profiles exhibited differences for a- and c-plane GaN, with a-plane showing significantly lower accumulated disorder in the buried layer, accompanied by the shift of the maximum damage accumulation into the deeper layer with respect to the theoretical prediction, than c-plane GaN. Angular scans showed channelling preservation in as-implanted samples and better channelling recovery in the annealed a-plane GaN compared to c-plane GaN. The angular scan widths were simulated by FLUX code as well as the half-width modifications of angular scans were discussed in connection to the damage accumulation. Photoluminescence measurement followed in detail yellow band and band edge luminescence decline after the implantation and the recovery of luminescence spectra features after annealing.