First principle study of Ce doping and related complexes in GaN

Using LDA+U method, we investigate the formation energy, electronic structure, and optical properties of rare earth Ce isolated substitutional and related complexes with neighboring N or Ga vacancies in wurtzite GaN. Our results reveal that CeGa introduces a localized defect level contributed by Ce-4f states in the band gap. The defect complexes CeGaVN and CeGaVGa introduce the shallow donor levels and acceptor levels, respectively. The doping of Ce in GaN gives rise to spin polarization. Both the substitutional Ce dopants and defect complexes can lead to new peaks from defect levels electronic transitions in the low energy regions of imaginary dielectric function and absorption spectrum.