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

Erbium has been implanted into (0001) epitaxial GaN grown on sapphire with an energy of 80 keV and a dose of 2.5 x 10(14) Er/cm(2). 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. 10degrees off the c-axis). A rather large critical angle of -6.5degrees 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 degreesC 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. (C) 2003 Elsevier Science B.V. All rights reserved.