Low-loss amorphous silicon waveguides grown by PECVD on indium tin oxide

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Electro-optically induced absorption in α-Si:H/α-SiCN waveguiding multistacks

Electro optical absorption in hydrogenated amorphous silicon (α-Si:H) – amorphous silicon carbonitride (α-SiCxNy) multilayers have been studied in two different planar multistacks waveguides. The waveguides were realized by plasma enhanced chemical vapour deposition (PECVD), a technology compatible with the standard microelectronic processes. Light absorption is induced at λ = 1.55 μm through the application of an electric field which induces free carrier accumulation across the multiple insulator/semiconductor device structure. The experimental performances have been compared to those obtained through calculations using combined two-dimensional (2-D) optical and electrical simulations

Low-loss amorphous silicon waveguides grown by PECVD on indium tin oxide

Low-loss hydrogenated amorphous silicon (α-Si:H) waveguides were realized by plasma enhanced chemical vapour deposition (PECVD) on a transparent conductive oxide (TCO) layer which is intended to provide the buried contact for the application of an external bias in active devices, e.g. switches and modulators. In particular we propose a technological solution to overcome both the strong reduction in optical transmittance due to the very high extinction coefficient of metal contacts and, at the same time, the optical scattering induced by the texturization effect induced in α-Si:H films grown on TCO. The very high optical propagation losses were minimized by depositing a spin-on-glass (SOG) layer between the α-Si:H core-layer and the TCO bottom contact. In this case, propagation losses of 2.5 dB/cm at 1550 nm were measured. All the fabricated samples were optically characterized and the surface roughness was accurately measured using a mechanical profilometer. We observed that, for an α-Si:H core-layer directly deposited on the TCO contact, the surface roughness is of the order of 100 nm leading to totally opaque waveguides. The experimental performances have been compared to those obtained through calculations using an optical simulation package. The results are found to be in agreement with the experimental data

Optical bandgap of semiconductor nanostructures: Methods for experimental data analysis

Determination of the optical bandgap (Eg) in semiconductor nanostructures is a key issue in understanding the extent of quantum confinement effects (QCE) on electronic properties and it usually involves some analytical approximation in experimental data reduction and modeling of the light absorption processes. Here, we compare some of the analytical procedures frequently used to evaluate the optical bandgap from reflectance (R) and transmittance (T) spectra. Ge quantum wells and quantum dots embedded in SiO2 were produced by plasma enhanced chemical vapor deposition, and light absorption was characterized by UV-Vis/NIR spectrophotometry. R&T elaboration to extract the absorption spectra was conducted by two approximated methods (single or double pass approximation, single pass analysis, and double pass analysis, respectively) followed by Eg evaluation through linear fit of Tauc or Cody plots. Direct fitting of R&T spectra through a Tauc-Lorentz oscillator model is used as comparison. Methods and data are discussed also in terms of the light absorption process in the presence of QCE. The reported data show that, despite the approximation, the DPA approach joined with Tauc plot gives reliable results, with clear advantages in terms of computational efforts and understanding of QCE. © 2017 Author(s)

A NEW ELLIPSOMETRIC PROGRAMME APPLIED TO THE CHARACTERIZATION OF TRANSPARENT CONDUCTING TITANIUM NITRIDE FILMS

La caractérisation de couches de TiN sur Si monocristallin, obtenues par implantation ionique, a été effectuée en traitant les mesures ellipsométriques par un programme très souple qui s'adapte bien aux conditions expérimentales. Les résultats obtenus sur les couches implantées et recuites par faisceaux d'énergie (faisceau d'électrons, lumière incohérente) sont examinés en vue d'applications technologiques possibles.The optical characterization of TiN films produced on Si substrates by ion-implantation was performed by handling the ellipsometric measurements through a flexible program which well conforms to the various experimental situations. The results obtained on as-implanted and transient thermally annealed films are discussed in relation to different possible technological applications

Electrooptical modulating device based on a CMOS-compatible α-Si:H/α-SiCN multistack waveguide

In this paper, we report results on a field-effect-induced light modulation at λ = 1.55 μm in a high-index-contrast waveguide based on a multisilicon-on-insulator platform. The device is realized with the hydrogenated amorphous silicon (α -Si:H) technology, and it is suitable for monolithic integration in a CMOS IC. The device exploits the free-carrier optical absorption electrically induced in the semiconductor core waveguide. The amorphous silicon waveguiding layer contains several thin dielectric films of amorphous silicon carbonitride (α -SiCN) embedded along its thickness, thus highly enhancing the absorbing action of the modulator held in the on state. © 2006 IEEE

Experimental determination of the sensitivity of Bloch surface wave based sensors

Detection of glucose in water solution for several different concentrations has been performed with the purpose to determine the sensitivity of Near Infrared Bloch Surface Waves (λ =1.55μ m) upon refractive index variations of the outer medium. TE-polarized electromagnetic surface waves are excited by a prism on a silicon nitride multilayer, according to the Kretschmann configuration. The real-time reflectance changes induced by discrete variations in glucose concentration has been revealed and analyzed. Without using any particular averaging strategy during the measurements, we pushed the device detection limit down to a glucose concentration of 2.5mg/dL, corresponding to a minimum detectable refractive index variation of the water solution as low as 3.8•10 -6. © 2010 Optical Society of America