材料期刊网

Electron paramagnetic resonance (EPR) zero-field splittings D for Mn2+ and Fe3+ in wurtzite GaN crystals are studied from high-order perturbation formulas based on the spin-orbit mechanism in both weak- and strong-field schemes. From these studies it can be seen that the Mn2+ or Fe3+ impurity does not occupy the exact Ga3+ position, but is displaced by DeltaR on the C-3 axis. The displacements are confirmed from a study of the superposition model, based on which a normal value of (b(2)) over bar (R-0) (approximate to -0.34 (15) cm(-1)) for the Fe3+-N3- combination is suggested. The EPR parameters D, g(parallel to) and g(perpendicular to) for Ni3+ in GaN crystals are also studied. It is found that Ni3+ is almost not displaced. The impurity displacements in GaN are discussed by considering the valences and radii of these impurity ions and the replaced Ga3+ ion.