Three-step amorphisation process in ion-implanted GaN at 15 K

GaN layers were implanted at 15 K with 150 keV O, 300 keV Ar or 800 keV Xe ions. The subsequent damage analysis was performed by Rutherford backscattering of He ions in channelling configuration at the same temperature. At this low temperature thermal effects can be widely excluded. However, the dependence of the damage concentration on the ion fluence suggests that the damage evolution in GaN is dominated by a pronounced recombination of the primarily produced defects within the collision cascades. Furthermore, a strong influence of the ions themselves has to be assumed in order to understand the experimental results. Such effects occur already at rather low ion fluences. Our results indicate an amorphisation of GaN proceeding in three steps