The photoluminescence spectra of Mg-doped samples were studied. Two sets of samples (reference and plastically deformed) were doped with Mg under identical conditions. The luminescence spectra of the reference samples revealed a set of lines, in the region of 1 to 1.07eV, but no radiation that was to be expected from the recombination of an exciton bound to a Mg donor was found. On the basis of the energy position and temperature behaviors, some of these lines were attributed to the recombination of free and bound excitons, with simultaneous excitation of the Mg0 donor. Unlike the reference samples, no such lines were found in deformed samples; with the exception of a weak line at the energy position which was close to the expected position of an exciton which was bound to the Mg0 center, and an additional emission which overlapped the dislocation related lines, D1 and D2. The latter were assumed to originate from recombination at Mg-dislocation complexes.

E.A.Steinman, H.S.Leipner, H.G.Grimmeiss: Solid State Phenomena, 1997, 57-58, 313-8