Optical Dispersion Model Research Articles

Universal method to determine the thermo-optic coefficient of optical waveguide layer materials using a dual slab waveguide

A dual slab waveguide device method for determining the thermo-optic coefficient of waveguide layer materials is demonstrated. Temperature change-induced optical path length imbalance between two single slab waveguide modes provides the primary mechanism for detection. The waveguide mode output field phase change differences are encoded in shifts in the far field interference pattern. To illustrate the method, the thermo-optic coefficients of two In1−xGaxAsyP1−y quaternary alloys, 1.3Q and 1.15Q, are measured at a wavelength of 1.55μm and at a center temperature of 25.2°C. Their ratio is in excellent agreement with previous work, in accordance with optical dispersion models.

Characterization and production metrology of gate dielectric films

We report efforts to develop optical dispersion models for new high k materials and silicon oxynitrides. We find the Tauc–Lorentz model provides superior fits to Ta2O5 and ZrO2 dielectric films in the spectral range 1.5–6.0eV. However, for typical oxynitrides which do not absorb below ∼6.0eV, we find the Tauc–Lorentz model confers no advantage over models which do not account for absorption. For the oxynitrides, we also find a monotonic relationship between film refractive index and nitrogen concentration, potentially useful for gate dielectric process control.

Calculation and analysis of the complex refractive index of uniform films of the As–S–Se glassy alloy deposited by thermal evaporation

Abstract Optical reflection spectra, at normal incidence, of amorphous semiconductor thin films of chemical composition, As 40 S 40 Se 20 , deposited by thermal evaporation, have been obtained in the 0.56–3.10 eV spectral region. The optical constants of this glassy alloy have been determined by use of an optical characterization method, which is based only on the upper and lower envelopes of the reflection spectra. Such a procedure allows accurate determination of the real and imaginary parts of the complex refractive index and the thickness of the films. Thickness measurements using a surface-profiling stylus have been carried out to cross-check the results obtained by the envelope method. The dispersion of the refractive index has been analyzed according to a new model recently proposed by Solomon. This optical dispersion model takes into consideration the width of the valence and the conduction bands, introducing a correction to the model that is based on the single oscillator. Finally, the optical-absorption edge of the a -As 40 S 40 Se 20 thin films is described in terms of the non-direct transition model proposed by Tauc, in the strong-absorption region, and in the medium-absorption region, according to Urbach's rule.