Study of calcium implanted GaN

Single crystalline GaN samples were implanted with several fluences of Ca ions at room temperature (RT) and 550 deg. C. The implantation at high temperature reduces significantly the damage. The measured minimum yield along the <0 0 0 1> axis in the implanted region increases from 15% to 40% when the substrate temperature during the implantation was changed from 550 deg. C and RT. The lattice site location was analysed simultaneously by measuring channeling effect on the backscattering particles and the particle-induced X-ray emission. Despite the different damage level, the regular fraction of Ca atoms in GaN lattice in both implantation conditions was roughly the same directly after the implantation (fs∼50%), as indicated by the angular scans. Annealing at 1050 deg. C for 15 min in flowing N2 results in a significant recovery of the damage, but no changes were found for the Ca profile. The angular scans along the <0 0 0 1> and <1 0 1-bar 1> axial directions indicate that Ca is occupying mainly interstitial sites