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Formation of size-controlled and luminescent Si nanocrystals from SiOxNy/Si3N4 hetero-superlattices

: Zelenina, A.; Sarikov, A.; Gutsch, S.; Zakharov, N.; Werner, P.; Reichert, A.; Weiss, C.; Zacharias, M.


Journal of applied physics 117 (2015), No.17, Art. 175303
ISSN: 0021-8979
ISSN: 1089-7550
Journal Article
Fraunhofer ISE ()

Silicon nanocrystals formed in the annealed SiNx/Si3N4 superlattices are attractive for research due to the smaller band offsets of Si3N4 matrix to Si in comparison with commonly used SiOx/SiO2 superlattices. However, the annealed SiNx/Si3N4 structures contain an increased number of nanocrystal interface defects, which completely suppress nanocrystal emission spectrum. In this work, we study a novel SiOxNy/Si3N4 hetero multilayer combination, which compromises the major issues of SiOx/SiO2 and SiNx/Si3N4 superlattices. The annealed SiOxNy/Si3N4 superlattices are investigated by TEM, demonstrating a precise sublayer thicknesses control. The PL spectra of the annealed SiOxNy/Si3N4 superlattices are centered at 845–950 nm with an expected PL peak shift for silicon nanocrystals of different sizes albeit the PL intensity is drastically reduced as compared to SiO2 separation barriers. The comparison of PL spectra of annealed SiOxNy/Si3N4 superlattice with those of SiOxNy/SiO2 superlattice enables the analysis of the interface quality of silicon nanocrystals. Using the literature data, the number of the interface defects and their distribution on the nanocrystal facets are estimated. Finally, it is shown that the increase of the Si3N4 barrier thickness leads to the increased energy transfer from the Si nanocrystals into the Si3N4 matrix, which explains an additional drop of the nanocrystal PL intensity.