The excitation mechanism of visible luminescence from Tb3+-doped silicon oxynitride is investigated. Tb-doped silicon oxynitride films were deposited by inductive-coupled plasma-enhanced chemical vapor deposition of SiH4, O-2, and N-2 with concurrent sputtering of Tb. Luminescences from both the host matrix and the Tb3+ intra-4f transition are observed, but no correlation is found between them as the composition and the annealing conditions were varied. Photoluminescence excitation spectroscopy shows a strong increase in the Tb3+ luminescence intensity as the pump energy is increased above 3.5 eV while the host matrix luminescence decreases. Taken together, the results that there is little energy transfer between band-tail states of silicon oxynitride and Tb3+, and that efficient excitation of Tb3+ by carriers requires excitation of carriers into the extended states of oxynitride. (c) 2006 American Institute of Physics.