Broad and nearly white photoluminescence induced by the nitrogen incorporation in Si/SiOxNy multilayers

Abstract

This work focuses on the study of the photoluminescent (PL) properties of Si/SiOxNy multilayer (ML) structures as a function of the thickness of silicon and silicon oxynitride layers. MLs were thermally annealed to induce the formation of silicon nanoparticles (Si-NPs). Infra-red spectroscopy (IR) vibration bands related to SiON bonds were observed and their intensity was stronger as the thickness of SiOxNy layers increased, indicating a larger N content. X-ray photoelectron spectroscopy (XPS) shows that the N content grows from 2 to 4% when the thickness of the SiOxNy layers increases from 2 to 6 nm, respectively; while it remains almost at the same value when the Si layer thickness changes. The analysis of the XPS-Si2p spectra reveals the formation of Si-NPs surrounded by a SiOxNy matrix by the existence of oxidation states such as Si4+, Si1+ and elemental silicon (Si0), as well as oxidation states attributed to the incorporation of nitrogen (N). MLs with the lowest N content (2%, thinnest oxynitride layer) emit a PL band centered in the red region, associated to the presence of Si-NPs and O-related defects. Nevertheless, an additional blue-green PL band is obtained when the nitrogen content increases (4%, thickest oxynitride layers). The N content induce radiative centers related to transitions of K or N centers which activates the blue-green PL. The diversity of these radiative centers within these Si/SiOxNy MLs produce a broad nearly white PL band, which is important for the development fo a white light source.