In situ ion channeling study of gallium disorder and gold profiles in Au-implanted GaN

Disorder accumulation and annealing behavior on the Ga sublattice in gallium nitride (GaN) implanted with 1.0 MeV Au2+ (60° off surface normal) at 180 or 300 K have been studied using in situ Rutherford backscattering spectrometry in a 〈0001〉-channeling geometry. Complete amorphization in GaN is attained at 6.0 and 20 Au2+/nm2 for irradiation at 180 and 300 K, respectively. A saturation in the Ga disorder at and behind the damage peak was observed at intermediate ion fluences at both 180 and 300 K. No measurable thermal recovery was found at 300 K for the full range of damage produced at 180 K. However, distinct epitaxial regrowth in the bulk and Ga reordering at surface occurred after annealing at 870 K. The implanted Au readily diffuses into the highly damaged regions at elevated temperatures, and the redistribution of the Au atoms in the implanted GaN varies with the damage profiles. A double-peak Au profile developed with the maxima located in the amorphous surface region and near the Au mean projected range. The result is interpreted as Au atom diffusion into the amorphous regime near the surface and Au trapping at irradiation-induced defects in the crystal structure. This trapping effect is also evidenced in this study by the suppressed recovery of the Au-decorated disorder in GaN.