Ultra-thin silicon nitride barrier implementation for Si nano-crystals embedded in amorphous silicon carbide matrix with hybrid superlattice structure

A hybrid superlattice structure consisting of 30 periods of alternating amorphous Si_0.7C_0.3 (5 nm) layers and ultra-thin Si₃N₄ barrier layers (0.2–2.0 nm) has been synthesised by magnetron sputtering, with subsequent annealing by a rapid thermal annealing (RTA) process. Si nano-crystals behave well confined within individual layers when the Si₃N₄ layer thickness is over 0.8 nm, due to the Si very low diffusion coefficient in Si₃N₄ matrix. Hopping is regarded as the dominant carrier transportation mechanism in the film based on fitting the temperature-dependent I-V measurements results. In conclusion an optimum Si₃N₄ barrier layer thickness of approximately 0.8 nm may be appropriate as a candidate material for photovoltaic application.