Photoluminescence and excitation energy transfer in non-stoichiometric silicon nitride

Photoluminescence of non-stoichiometric silicon nitride films has been studied at excitation range 3.35-5.16 eV. Several bands with energies 3.15, 3.4, 3.62, 3.8, and 3.95 eV have been observed in the PL spectra. The bands at 3.62, 3.8, 3.95 eV assigned to exciton annihilation. Emission at energies 3.15 and 3.4 eV shifts in red spectrum region with excitation energy decreasing. The shift is explained by photo-induced neutralization of charged defect states and the emission can be associated with radiative recombination of charge carriers localized on donor-acceptor pairs. Energy-resolved photoluminescence method reveals the excitation energy transfer channels. It has been found that excitons participate in process of energy transfer to donor-acceptor pairs, providing 3.4 eV band position invariant to the excitation energy.