Abstract
Obtaining silicon-based photonic-structures in the ultraviolet range would expand the wavelength bandwidth of silicon technology, where it is normally forbidden. Herein, we fabricated porous silicon microcavities by electrochemical etching of alternating high and low refraction index layers; and were carefully subjected to two stages of dry oxidation at 350 °C for 30 minutes and 900 °C, with different oxidation times. In this way, we obtained oxidized porous silicon that induces a shift of a localized mode in the ultraviolet region. The presence of Si-O-Si bonds was made clear by FTIR absorbance spectra. High-quality oxidized microcavities were shown by SEM, where their mechanical stability was clearly visible. We used an effective medium model to predict the refractive index and optical properties of the microcavities. The model can use either two or three components (Si, SiO2, and air). The latter predicts that the microcavities are made almost completely of SiO2, implying less photon losses in the structure. The theoretical photonic-bandgap structure and localized photonic mode location showed that the experimental spectral peaks within the UV photonic bandgap are indeed localized modes. These results support that our oxidation process is very advantageous to obtain complex photonic structures in the UV region.
Highlights
Obtaining silicon-based photonic-structures in the ultraviolet range would expand the wavelength bandwidth of silicon technology, where it is normally forbidden
Gelloz used High-Pressure Water Vapor Annealing (HWA) for the stabilization of Bragg Reflectors (BRs) obtained at low anodization temperatures (−20 °C) using p-type Si; HWA was conducted at pressures from 1.3 to 2.6 MPa, at 260 °C and for three hours; this method improves the transparency of Porous Silicon (PS) layers with an efficient response in the UV region due to a high oxidation of the PS structures[21]
A modified Breit-Wigner equation was used to get the dispersion in the localized mode due to absorption and scattering losses[25,30]; from this equation we estimated photon loss rates, which includes both types of losses, Rayleigh scattering and light absorption, whereby the lifetime of photons and photon loss can be defined at the localized mode wavelength
Summary
Obtaining silicon-based photonic-structures in the ultraviolet range would expand the wavelength bandwidth of silicon technology, where it is normally forbidden. The second stage was performed at high oxidation temperature of 900 °C This oxidation process transforms almost completely the PS MCs into porous SiO2 MCs, as it was indicated by our three-component effective medium approximation, the high visible light transparency of the oxidized MCs and the presence of prominent Fourier-Transform Infrared Spectroscopy (FTIR) Si-O-Si peaks. This oxidation transformation induces an UV shift of the MCs localized mode, and a decrease of the optical losses within the MCs. In order to assure that the porous multilayers structure after oxidation was preserved, we used Scanning Electron Microscopy (SEM). This result opens up the possibility of novel PS based photonic devices
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
