Porous silicon-based UV microcavities (Conference Presentation)

Abstract

The theoretical and experimental study of porous silicon-based UV microcavities is discussed in this work. The obtaining of CMs in the Ultraviolet range expands the field of research of porous silicon photonic structures. The porous silicon microcavities (PSM) consisted of two Bragg reflectors (BRs) with a defect between them. It was fabricated by electrochemical etching. Microcavities (MCs) were subjected to dry oxidation process (DOP). In this way we obtained an oxidized porous silicon (OPS) that induces a shift of the response to the ultraviolet (UV) region on both, the minimum peak of the reflectance spectrum and the maximum peak of the transmittance spectrum; two UV microcavities showed maximum transparency in the UV of 67 %. The shift is explained as due to the formation of silicon dioxide (SiO₂); this wavelength shift shows a logarithm-like function of oxidation times. It was used a theoretical model to predict the refractive index of the MCs that contains two components (Si and air) and tree component (Si, SiO₂, and air). Moreover, a photonic model was used to obtain the photonic band gap structure and the defect modes of different MCs in the UV-Visible range. The theoretical results showed that the experimental peaks within the UV photonic bandgap are indeed defect modes. Characterization of MCs was performed by SEM, FTIR and UV-Vis-NIR spectroscopy before and after the DOP. These results open the possibility to create silicon-based photonic structures within the UV range where usually silicon or porous silicon either strongly absorb or scatter light.