Implantation induced defect states in gallium nitride and their annealing behaviour

Gallium nitride layers grown by metal organic vapour phase epitaxy on sapph ire were implanted with different ion species, i.e. silicon, sulfur, and ma gnesium, and thermally annealed at 1150 degreesC under nitrogen atmosphere. The impact of this annealing procedure on the resulting deep levels was an alyzed by transient and admittance spectroscopy. Several electron traps wit h thermal activation energies between 200 and 900 meV as well as very deep states at photon energies ranging from 1.8 to 2.5 eV were induced by the im plantation process independent of the ion species. After annealing, in gene ral the deep level spectrum shows only minor changes, but an enhancement of the shallower electron traps and a new electron trap for the Si-implanted layers can be observed. These results are explained by a re-arrangement of the induced defects and supported by photoluminescence experiments. Finally , the ineffectiveness of this annealing procedure which is often used by th e community to reduce the implantation damage is demonstrated.