At low fluences, 300keV Eu implantation led to a strain increase followed by a saturation as observed by X-ray diffraction, while Rutherford back-scattering/channelling remained insensitive to the radiation damage. Based upon transmission electron microscopy, this saturation regime was attributed to a damaged region in the crystal bulk in which interaction between point defects and stacking faults occurred, leading to the densification of the network of planar defects by the trapping of point defects. At higher fluences, above 2 x 1014Eu/cm2, the evolutions of strain state in another region and of the microstructure as observed by TEM indicated a modification of the degradation mechanisms which now involved a migration of point defects out of the region of stacking faults. This resulted in the formation of a highly strained area below the region of stacking faults made up of large point defect clusters, and in the extension of the stacking fault network towards the surface that eventually led to its nanocrystallization.

Mechanisms of Damage Formation in Eu-Implanted GaN Probed by X-ray Diffraction. B.Lacroix, S.Leclerc, A.Declémy, K.Lorenz, E.Alves, P.Ruterana: EPL, 2011, 96[4], 46002