Extracting defect profiles in ion-implanted GaN from ion channeling

Ion implantation offers many advantages for material doping, namely a meticulous control over various parameters such as implantation area, fluence, energy, etc. However, ion-induced damage is a major disadvantage of this technique. Defect creation and evolution upon ion bombardment is a complex process and requires sophisticated methods to unravel the resulting defect profiles. In this work, Rutherford Backscattering Spectrometry in Channeling mode using 1.4-2.2 MeV He+ ions, is performed in GaN samples implanted with different fluences of 300 keV Europium ions. Several data analyzing methods, commonly used to find the defect profiles, are compared. The difference in the minimum yield dependence on the He+ beam energy allowed for a qualitative analysis regarding the dominant defect type. In agreement with previous transmission electron microscopy studies, results suggest the co-existence of randomly displaced atoms and extended defects. Both Monte Carlo simulations, using the McChasy-1 code, and the Two-Beam Approximation permitted quantitative results, which show a good agreement with each other, although further improvements on the models are necessary for high fluence regimes. Particularly, the addition of basal-plane dislocation loops and stacking faults in the McChasy code is expected to be relevant in such regimes. The results show that damage increases with fluence in a complex way, evidenced by the abrupt damage increase for the highest fluence and the broadening of the profiles, which suggest defect diffusion and elaborate defect evolution mechanisms.