A detailed study of as-grown Zn-doped GaN employing optically detected magnetic resonance (ODMR) spectroscopy is presented. Besides the well-known ODMR spectra of an effective-mass-like donor and Zn acceptor, a positive ODMR signal of an $S=\frac{1}{2}$ paramagnetic center was observed when monitoring the dominating blue luminescence band peaking at 2.8 eV. The involvement of a single Ga nucleus in the defect center is revealed from the rather well-resolved hyperfine interactions involving the isotopes ${}^{71}\mathrm{Ga}\hspace{0.5em}\mathrm{}(39.9\%)\mathrm{}$ and ${}^{69}\mathrm{Ga}\hspace{0.5em}\mathrm{}(60.1\%),$ both with nuclear spin $I=\frac{3}{2}.$ The $C_{3v}$ symmetry, the hyperfine interaction and the defect formation suggest a Ga-related complex nature of this center.

• Received 27 July 2000

DOI:https://doi.org/10.1103/PhysRevB.62.R10607