Layers grown onto sapphire by metalorganic vapour-phase epitaxy were implanted with various ions (Si, S, Mg) and annealed at 1150C under a N atmosphere. The effect of annealing upon the resultant deep levels was analyzed by using transient and admittance spectroscopy. Several electron traps, with thermal activation energies of between 0.2 and 0.9eV, 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 type. After annealing, the deep level spectrum generally exhibited only minor changes, but an enhancement of the shallower electron traps and a new electron trap in Si-implanted layers was observed. The results were explained in terms of rearrangement of the defects induced, and this was supported by photoluminescence experiments. The ineffectiveness of the annealing procedure which was often used to reduce implantation damage was 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