Effect of As doping on the photoluminescence of nanocrystalline 74Ge embedded in SiO2 matrix

Samples of nanocrystalline 74Ge embedded in amorphous SiO2 film were prepared by 74Ge ion implantation and subsequent primary thermal annealing. These samples were irradiated by neutron flux in a nuclear reactor then the second annealing followed. Irradiation with thermal neutrons leads to doping of nanocrystalline 74Ge with As impurities due to nuclear transmutation of isotope 74Ge into 75As. Transmission electron microscope, X-ray fluorescence, X-ray photoelectron spectroscopy, laser Raman scattering and photoluminescence of the obtained samples were measured. It was observed that with the increase in As-donors concentration, photoluminescence intensity first increased but then significantly decreased. An explanatory model of this non-monotonic behavior was discussed.