Luminescence properties of nano-structured silicon

Abstract: This work investigates the luminescence properties of nanostructured silicon under the influence of electric fields, focusing on Si nanocrystals (NCs) embedded SiO2 matrices and Si NC/SiO2 superlattices. These devices are prepared by plasma enhanced chemical vapour deposition of oxide thin films of varying Si content and the following high temperature annealing resulting in the formation of Si NCs inside the oxide. Photoluminescence (PL) spectroscopy measurements are used to study the two main types of device architectures: single active Si NC layers sandwiched between thick blocking oxide barriers and Si NC/SiO2 superlattices with alternating active layers and thin inter-layer-barrier oxides.
With single layer devices the effect of the quantum confined Stark shift on the luminescence spectra is analysed. Findings show a trend of red shift in the spectra linked to the change in energy eigenvalues of the discretized energy levels which is more pronounced for smaller NCs due to higher field strength but compared at equal field magnitudes the confinement in smaller NCs leads to the shift being grater in larger NCs. Alongside this, a reduction in luminescence intensity caused by a spatial shift in the carrier wavefunctions is shown to agree with analytical models based on first principles, indicating potential for reversible field-driven wavelength modulation.
The superlattice devices are studied to examine the effects of external fields on exciton separation in Si NCs and the associated PL quenching due to carrier transport between NCs along the field. This phenomenon is linked to reduced Auger recombination lifetimes at higher carrier densities. Effects of inter-layer-barrier thickness, temperature, and surface defect density at the Si-SiO2 interfaces have been systematically analysed. The results highlight the significance of barrier thickness and trap assisted carrier transport in superlattice conductivity as well as the role of post-annealing treatments for defect passivation. Finally, the applicability of Si NC/SiO2 superlattice devices in tandem photovoltaics is explored based on these findings

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• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Universität Freiburg, Dissertation, 2024

Classification and Topics

• Keyword: Silicium ; Nanostrukturiertes Material ; Lumineszenz ; Dünne Schicht ; Nanotechnologie ; PECVD-Verfahren ; Photolumineszenz ; Quantenpunkt ; Stark-Effekt ; Atomlagenabscheidung ; Siliciumhalbleiter ; Tunnelierung

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2024
• Creator: Yazicioglu, Deniz
• Contributor: Zacharias, Margit ; Rapp, Bastian E. ; Albert-Ludwigs-Universität Freiburg. Institut für Mikrosystemtechnik ; Albert-Ludwigs-Universität Freiburg. Professur für Nanotechnologie ; Albert-Ludwigs-Universität Freiburg. Fakultät für Angewandte Wissenschaften

Further information

• DOI: 10.6094/UNIFR/255885
• URN: urn:nbn:de:bsz:25-freidok-2558851
• Rights: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.