Heavy ion implantation in GaN epilayers

GaN epilayers grown on sapphire were implanted with several fluences of In, Er and Hf ions to study the damage behavior and lattice site location of the implanted species. The damage in the Ga sublattice develops a double peak structure with one peak at the surface and the other near the end of the range of the implanted ions. For fluences above 5 x 10(15) Er+/cm(2) the peaks overlap and the implanted region becomes amorphous. Rapid thermal annealing at 600degreesC recovers completely the damage produced by the implantation of 5 x 10(14) In+ /cm(2) while only a small recovery was observed for samples implanted with similar Er and Hf fluences. Defect recovery studies with hyperfine interaction techniques using In-111 and Hf-181 as probes show that below 600degreesC only defects in the N sublattice anneal out whereas temperatures up to 1000degreesC are necessary to restore the short range order to the Ga sublattice. Similarly the RBS measurements showed that rapid thermal annealing up to 1000degreesC was not enough to recover completely the crystallinity of the samples.