The electron paramagnetic resonance spectra of Fe-related defects in high-quality thick freestanding hydride vapour phase epitaxially grown GaN were studied in the X- and Q-band. The dominating part of the complex resonance pattern was due to isolated Fe3+ (3d5, S = 5/2) on the 2 equivalent Ga sites A and B with C3V point symmetry in the hexagonal GaN unit cell. These two physically equivalent sites, caused by the ABAB stacking sequence of the wurtzite structure, could be distinguished by electron paramagnetic resonance for electron spin systems S ≥ 2. Preferential incorporation of Fe into one of the two types of Ga site was found. In spite of the strong overlap with the ntensive Fe3+ transitions, the most of the observed additional very weak lines could be identified as being pairs.

Site Selectivity of FeGa3+ and the Formation of FeGa3+-Gai Pairs in GaN. W.Gehlhoff, D.Azamat, A.Hoffmann: Physica Status Solidi B, 2006, 243[7], 1687-91