Opto-structural properties of Si-rich SiNx with different stoichiometry

This study deals with the fabrication and characterization of silicon nanoparticles in a SiNx dielectric matrix to have thin films of different gap energies, films essentially based on silicon. Hydrogenated silicon-rich nitride films SiNx:H with different stoichiometry X = N/Si were grown on Si substrate using industrial low-frequency plasma-enhanced chemical vapor deposition (LF-PECVD). Optical, electrical, and structural properties of the obtained films have been studied after rapid thermal annealing at 950 °C. The GIXRD and Raman analysis demonstrate that the films contain simultaneously the hexagonal β-Si3N4 phase and crystalline silicon nanoparticles and the average size of silicon nanocrystallites is within the range of 2.5–11 nm according to the stoichiometry. A strong visible photoluminescence (PL) can be observed in silicon nitride and the evolution of PL with the NH3/SiH4 ratio is correlated with the evolution of the structure. The layers having a luminescence in the visible region present a photocurrent (PC) in the high-energy region. PC spectroscopy has clearly demonstrated the existence of increased absorption on the high-energy side associated with Si-Ncs and confirms the potential of Si-Ncs for photovoltaic applications.