Layers grown by metal-organic vapour phase epitaxy onto sapphire were implanted with Si, S and Mg, and annealed at 1150C under a N atmosphere. The effect of the annealing procedure upon the resultant deep levels was analyzed by using transient and admittance spectroscopy. Several electron traps with thermal activation energies between 0.200 and 0.900eV, as well as very deep states at photon energies ranging from 1.8 to 2.5eV, were introduced by the implantation; regardless of the ion species. After annealing, the deep-level spectrum generally showed only minor changes but an enhancement of the shallower electron traps and a new electron trap for Si-implanted layers was observed. The results were explained by a rearrangement of the induced defects and this was supported by photoluminescence data. The ineffectiveness of the annealing procedure which was often used to reduce implantation damage was also demonstrated.

Implantation Induced Defect States in Gallium Nitride and Their Annealing Behaviour. A.Krtschil, A.Kielburg, H.Witte, A.Krost, J.Christen, A.Wenzel, B.Rauschenbach: Physica Status Solidi B, 2001, 228[1], 325-9