Transition metal defects in group-III nitrides: An ab initio calculation of hyperfine interactions and optical transitions - art. no. 075204

We present ab initio calculations for 3d transition metal point defects and for defect pairs in group-III nitrides with a special emphasis on charge t ransfer energies, hyperfine interactions, and internal optical transition e nergies. Our LMTO-ASA Green's function total energy calculations show Vac(N )-TM pairs to he tightly bound in semiconducting and in n-type GaN and AlN with pair formation energies in excess of 1 eV. We show that in the framewo rk of density functional theory reliable total energies are obtained for ex cited states, if the levels involved are represented by a single determinan tal state within a 3d(N) basis. Our optical transition energies agree fairl y well with the experiments.