Influence of the implantation angle on the generation of defects for Er implanted GaN

Erbium has been implanted into (0 0 0 1) epitaxial GaN grown on sapphire with an energy of 80 keV and a dose of 2.5 x 1014 Er/cm2. Rutherford backscattering and channelling spectrometry were used to investigate the effect of the implantation geometry on the defect generation. The defect density is significantly reduced when implanting along the GaN c-axis and gradually increases when changing the implantation angle towards random implantation (i.e. 10 deg. off the c-axis). A rather large critical angle of ∼6.5 deg. is found, indicating that channelling of the Er ions occurs easily. The generated defects expand the GaN lattice in the implanted region, which results in a satellite peak in the high-resolution X-ray diffraction spectra. After annealing the samples at 950 deg. C for 30 min in nitrogen ambient, a reduction in defect density as well as a relaxation of the GaN lattice towards the bulk value is observed for all implantation angles