Effect of Design and Rare-Earth Doping of the Structural, Optical, Electrical and Light Emitting Properties of Si-Based Superlattices Developed for Photonic Application
Undoped and rare-earth (RE) doped Si-rich-SiO2 (SiOx) composite films and multilayers were recently investigated [1-3]. An efficient RE emission was achieved in Er- and, later, Nd-doped SRSO films due to an interaction of RE ions with Si-nanoclusters (Si-ncs). Although, a multilayer (ML) approach offers a precise control of Si-ncs distribution via a tuning of SRSO thickness, RE-doped SRSO-based MLs are not well addressed. This work presents the benefits of ML approach to achieve high efficiency and to control RE emission from Nd-doped SiOx/SiNx-based MLs grown by RF magnetron sputtering. Their properties were studied by means of XRD, TEM, PL and PL excitation methods versus deposition conditions, annealing treatment and ML design (doping, thickness of alternated sublayers (silicon oxide, nitride)). In each type of ML structures, either one or both sublayers were doped with Nd ions to investigate the effect of selective or full doping on PL emission. The results will be summarized and compared with those of Nd-doped SiOx/SiO2 MLs. It will be showed that comparable Nd PL emission can be obtained for both types of ML structures. Besides, fabrication approach allowed the PL emission to be achieved from as-grown samples. However, the highest Nd PL intensity was obtained after an annealing at about 700°C in nitrogen flow, whereas the formation of crystallized Si-ncs occurs at 1000-1100°C. The mechanism of Nd ions' excitation (i.e. an interaction with Si-ncs as well as with matrix defects, if any) will be discussed in details based on PL excitation spectra and PL life-time data. These results reveal potential photonic applications of Nd-doped MLs.
This work was supported by French National Agency (ANR) through DAPHNES project.