An annealing study of luminescent amorphous silicon-rich silicon oxynitride thin films

We report the effect of the rapid thermal annealing (RTA) of amorphous silicon oxynitride (a-SiOxNy:H) thin films on the room-temperature photoluminescence (PL). Samples were prepared by plasma enhanced chemical vapor deposition. The PL intensity increased by one order-of-magnitude after annealing for 20 min at 800 degrees C compared to that of the as-deposited sample. We have followed the changes in the chemical microstructure of the materials by in situ real-time ellipsometry, and suggest that the annealing is characterized by two distinct mechanisms. The first is that hydrogen effusion from clustered hydrogen and/or =N-H bond breaking occurs in the first 5 min resulting in increasing dangling bond density and no increase in the PL intensity. The second occurs after longer annealing times due to local reconstruction of Si-O and Si-N bonds, rather than diffusional rearrangement of the atomic species. This results in a more dense material with a higher refractive index, fewer nonradiative recombination centers, and more efficient PL, A model is presented to describe both the radiative and nonradiative recombination processes. (C) 1995 American Institute of Physics.