Theoretical study of rare earth point defects in GaN

The behavior of rare earth dopants in GaN was investigated by means of theoretical techniques. The Density Functional based Tight-Binding method (DFTB) has been extended to include orbital dependent potentials (LDA+U and SIC-like) in attempt to model. the 4f states of lanthanide impurities within a realistic crystal model. We present results of an investigation into the structural and and energetic Properties of rare earth (Eu, Er and Tm) point defects in GaN. Lanthanide ions (either isolated or complexed with GaN native defects) prefer the Ga-site. Among the investigated defects the REGa V-N pairs are the most promising candidates as luminescent centers, while, interstitial lauthanides are found not to be compatible with the observed luminescence. Differences in the behavior of the single lanthanide ions are explained in term of different 4f-shell occupation and ion size.