Optically detected magnetic resonance of a self-activated emission at 1.94 eV in gallium-doped zinc sulphide

Optically detected magnetic resonance experiments on gallium-doped zinc sulphide have shown that a band at 1.94 eV is attributable to the radiative recombination of donor electrons with holes on A-centres. The donor are identified as gallium ions substituting at zinc sites to form deep levels which are estimated to lie 0.4 eV below the edge of the conduction band. The depth is consistent with the large gallium hyperfine interaction which indicates that the donor wavefunction is well localised. Donor-acceptor pair recombination also provides an explanation for the previously reported observation of emissive microwave transitions in the Ga 2+ photostimulated EPR spectrum.