Structural and optical properties of high density Si-ncs synthesized in SiNx : H by remote PECVD and annealing
Résumé
Silicon nanocrystals (Si-ncs) embedded in silicon nitride are of great interest for micro and optoelectronic devices such as non-volatile memories and solar cells. Indeed, Si3N4 is a “high-k” dielectric and can replace SiO2 in Si-ncs memories, increasing their performances. On the other hand, Si-ncs embedded in Si3N4 antireflection layer of solar cells can be used as luminescent converters to enhance photovoltaic conversion in the blue region of the spectrum. Controlling Si-ncs characteristics (density, size, surface passivation, etc.) is necessary to the optimisation of both electrical and optical properties of the layers. In this work, we synthesized SiNx:H 50 nm thick layers by ECR-PECVD using NH3 and SiH4 gases. Si-ncs are obtained thanks to a Si atom excess in the matrix, controlled by the gas flow ratio. The samples were annealed under Ar flow, first in a RTA furnace at 1000 °C during 1 min for particles nucleation, and then in a classic furnace, from 700 °C to 1100 °C, in order to investigate the Si nanostructure evolution. We studied the structural characteristics of Si-ncs population by energy-filtered transmission electron microscopy (EF-TEM). The layers composition was determined by Rutherford back scattering spectroscopy (RBS) and elastic recoil detection analysis (ERDA). Their optical properties were studied by photoluminescence spectroscopy (PL). Results clearly show that structural and optical characteristics of these systems can be controlled by deposition parameters and annealing.