Hisayoshi Yanai

Characteristics of optical guided modes in multilayer metal-clad planar optical guide with low-index dielectric buffer layer

The attenuation characteristics of a multilayer metal-clad optical guide, which is suitable for a mode filter or electrooptic devices, is investigated by the exact theory and the analytical approximation based on a perturbation technique. By using this approximation the dependences of the ohmic loss on the various waveguide parameters and the condition for the absorption peak of the TM mode are derived in closed form. Some remarks concerning the waveguide material and dimension for the design of the mode filter are also presented. The insertion loss at the abrupt junction between a normal (dielectric-clad) optical guide region and a metal-clad optical guide region is treated. Also the transformation of optical guided modes in the two kinds of tapered structures between the above two regions is examined.

Effect of Photon Recycling on Diffusion Length and Internal Quantum Efficiency in AlxGa1-xAs–GaAs Heterostructures

The photon recycling process, i.e., the excitation of electron-hole pairs by the reabsorption of luminescent light, has large effects on the determination of the minority carrier diffusion length L and the internal quantum efficiency ηin GaAs with a high quantum efficiency. In this report, we show that the separate treatments of L and ηin cause the erroneous results for materials with high quantum efficiency. We developed a consistent method of evaluating the photon recycling effects on both ηin and L, based on the simultaneous measurements of the external quantum efficiency ηex and the photo-excited current under the short circuit condition Isc. This method was applied to the specimens with single heterestructure (p-AlxGa1-xAs-p-GaAs-n-GaAs) prepared by the liquid phase epitaxial (LPE) process.

Improved coupled mode analysis of corrugated waveguides and lasers

In the previous paper [1] we proposed an accurate formalism for analyzing corrugated waveguide devices. This formalism, developed for the TE modes, is extended here to TM modes. Characteristics of TM modes in distributed feedback (DFB) lasers, DBR reflectors, and grating beam couplers are investigated with emphasis on the effect of the radiation loss and they are compared with the TE case.

Propagation Characteristics of a Partially Metal-Clad Optical Guide: Metal-Clad Optical Strip Line

Experimental investigations of the partially metal-clad optical guide were performed. The optical guide consisted of a silicon substrate, an SiO(2) low index dielectric layer, an Al(2)O(3) high index dielectric layer, and a partial cladding layer of Al. The far-field patterns of the output beam from the second prism coupler were consistent with the calculated transverse field distributions using the effective index-of-refraction method. The experimental results on the coupling angles, confinement at the curved section, and attenuation constants are also reported.

Transport processes of electrons in MNOS structures

The transport processes of electrons in MNOS structures, especially in the SiO2 layer and the surface region of the Si substrate, have been investigated using p‐channel MNOS transistors with a relatively thick SiO2 layer to avoid the complexity of two‐carrier transport in the system. An induced junction technique utilizing the electron and hole separation properties of the transistor structure was used as a means of analysis. Theoretical derivation of the carrier multiplication factor, i.e., the number of electron‐hole pairs produced by an electron entering the Si from the SiO2, is calculated. It is experimentally shown that an electron entering the Si from the SiO2 produces approximately one electron‐hole pair in the low negative gate bias voltage range up to a critical voltage, and above this critical voltage the multiplication factor increases with increasing gate bias voltage. The former observation is in good agreement with the prediction of the theory, considering cascaded impact ionization of an el...

Epitaxial Growth of SiC Film on Silicon Substrate and Its Crystal Structure

SiC film is epitaxially grown by reacting methane to silicon. The growth rate of the film is measured as a function of the temperature and the partial pressure of methane. The results show that the film thickness is proportional to t1/2(ln p+A)1/2×exp (-4q/2kT) where t is the reaction time, p is the partial pressure of methane, T is the reaction temperature and A is constant. Because of the parabolic rate law, the high activation energy of 4 eV, and the dependence of partial pressure of methane, the rate determining process will be due to the diffusion of carbon atoms through the SiC film. By electron diffraction analysis, the crystal structure of the film is studied. The film is composed of two layers, a single crystal layer and a polycrystalline layer. The single crystal layer is at the surface of the film, and the polycrystalline layer is at the interface of SiC and Si. An epitaxy relationship between SiC and Si is observed.

Improved coupled mode analysis of corrugated waveguides and lasers - II: TM mode

In the previous paper [1] we proposed an accurate formalism for analyzing corrugated waveguide devices. This formalism, developed for the TE modes, is extended here to TM modes. Characteristics of TM modes in distributed feedback (DFB) lasers, DBR reflectors, and grating beam couplers are investigated with emphasis on the effect of the radiation loss and they are compared with the TE case.

Direct modulation of a double-heterostructure laser using a Schottky-barrier-gate Gunn-effect digital device

By using a Schottky-barrier-gate Gunn-effect digital device the direct modulation of a GaAs-Al x Ga 1-x As double-heterostructure laser was achieved with a rise time of 250 ps. The dependence of the optical waveforms on the bias-current levels was investigated in detail. The results are compared with a rate-equation analysis. A discrepancy between the present theory and the experiment indicates the existence of an additional relaxation mechanism.

Degradation properties in metal‐nitride‐oxide‐semiconductor structures

Degradation properties in metal‐nitride‐oxide‐semiconductor (MNOS) structures are investigated using mainly p‐channel MNOS transistors. A model is proposed on the basis of various experimental results, attributing the degradation to the passage of hole current through the SiO2 layer, followed by creation of hole traps in the SiO2 layer, and creation of interface states at the Si‐SiO2 interface. A theoretical treatment of the enhancement of hole conduction in the degraded SiO2 layer of the p‐channel thick‐oxide MNOS transistor is performed, and the hole traps created in the SiO2 layer appear to be E′ centers when the experimental results are fitted to the theoretical calculations. The nature of the interface states created by write‐erase (W/E) cycling is also discussed, comparing the experimental results using a p‐ and an n‐channel MNOS transistor.

Electron Transport Properties of GaxIn1-xSb Calculated by the Monte Carlo Method

Electron transport properties of GaxIn1-xSb were investigated by the Monte Carlo methods. An emphasis was placed on the electron transfer effect in the material for various compositions. The threshould field was shown to increase from 600V/cm to 700V/cm with increase in the Ga composition despite a decrease in the energy separation between Γ and L valleys, while the peak-to-valley ratio of the drift velocity decreases. The upper frequency limit of negative differentical mobility, effects of temperature rise and impurity scattering, and the low field mobility were also calculated by using almost the same program. It was revealed that materials with the Ga composition between 60 and 80% (atomic) are most suitable for low-dissipation power transferred-electron devices, in particular digital devices.