bluuebunny/crossref_metadata_2025 huggingface dataset:
Method of materials design for I‐III‐VI2 chalcopyrite‐type mixed crystal semiconductors
Authors: Nomura Shigetaka , Endo Saburo , Irie Taizo
Published: July 2007

Binary compound semiconductors have become extremely, important in the study of semiconductor devices. On the other hand, it is difficult to obtain a large size, highquality single crystal for a semiconductor composed of more than three elements belonging to different groups which is a so‐called multinary compound semiconductor. Therefore, such a semiconductor has only been of interest in research for material properties. A chalcopyrite‐type compound has been a target of interest as a ternary compound semiconductor. This paper describes the relatins between several properties and mean atomic weight, and the relations between the crystal ionicity and material properties in chalcopyrite‐type semiconductors. These factors are used to obtain some guidelines for designing the materials with the desired characteristics in chalcopyrite‐type mixed crystal semiconductors. As a result, contour maps of gap energy and lattice constants as functions of mean atomic weight for these materials were obtained. This method of designing materials is confirmed experimentally for I‐III‐VI2‐type mixed crystal semiconductors.
Computer‐aided processing system (CAPS) for vlsi development
Authors: Kotani Norihiko , Yamano Tsuyoshi , Tateishi Junji , Akasaka Yoichi , Kawazu Satoru
Published: July 2007

In VLSI development, many experiments are required to determine the process flow and the process specifications for wafer treatment. Therefore, the kinds of experiments have become tremendous for the development. Since the process specifications are often different from wafer to wafer, the management of many sort and small quantity lots is essential.

In this paper, a distributed wafer tracking system for VLSI development is described. This distributed computer system is constituted of personal computers and a host computer. A new method was developed and adopted in which the process specifications are pre‐registered on 3.5 inch floppy discs as well as a new data management architecture. This system realizes higher reliability and flexibility using simple hard/software construction and flexibility than the conventional centralized system.
Analysis of electron wave reflectivity and leakage current of multi‐quantum barrier: MQB
Authors: Uenohara Hiroyuki , Iga Kenichi , Koyama Fumio
Published: July 2007

A multi‐quantum barrier (MQB) is proposed which is made of super lattices. The electron wave reflectivity and the leakage current of the MQB structure for an electron energy are calculated theoretically by means of a simplified model. The MQB structure studied here is a multiple heterostructure made of a combination of periodic structures with different well widths and barrier widths. The reflected waves from each interface are intensified by interference. The energy values at which the reflection is intensified are changed slightly by changing periodic structures. By combining these periodic structures the reflectivity is enhanced toward unity up to the energy higher than the classical barrier height. It is found from the calculations that the effective potential height of the MQB structure is higher by about 30 percent in the GaAs/AlAs and by about 50 percent in the Ga0.47In0.53As/InP than the classical barrier height. It is expected that the MQB structure can be used in high‐temperature operation light‐emitting devices and short‐wavelength light‐emitting devices.
Development of HOT‐CARRIER simulator H2‐CAST and its application to LDD
Authors: Hamada Akemi , Toyabe Toru , Takeda Eiji
Published: July 2007

A hot‐carrier simulator (H2‐CAST) is developed using the “effective electron temperature model;” and with this simulator, the LDD structure is analyzed. This simulator is based on a 3‐D device simulator, where the carrier motion in the oxide film is also considered. The model equation for the channel hot electron region and the avalanche hot electron region in the NMOS single‐drain structure is evaluated. It is found that the model is valid for an analysis of the hot‐carrier injection phenomena in both regions. From the analysis of the LDD structure, it is apparent that the injection of the avalanche hot‐holes is responsible for the degradation of the device characteristic. This simulator is considered to be an effective tool in designing a device with an effective channel length Leff less than 0.8 μm.
Finite‐element analysis of convective diffusion equation for semiconductor problems using conjugate gradient method
Authors: Ono Masashi , Hane Masami , Hane Kunio , Suzuki Tokio
Published: July 2007

By means of a finite‐element method, the nonsteady‐state convective diffusion equation describing the diffusion problem in a semiconductor is discretized. A conjugate gradient method is applied to the resultant matrix for analysis of the problem. A technique is applied to the equation before discretization so that a windward discretization is applied. As a result, suppression of the parasitic spatial oscillation and improvement of convergence have been attained. Both these points are problems in conventional finite‐element methods. However, by means of the improvement herein, both the accuracy and the computation time have been improved. The result has been applied to the semiconductor diffusion equation and the convective diffusion equation, and the effectiveness of the method has been confirmed.
Zero slope tempartures SiO2/LiTaO3 structure substrate for stoneley waves
Authors: Irino Toshio , Shimizu Yasutaka , Watanabe Takaya
Published: July 2007

A theoretical and experimental study has been conducted on Stoneley waves propagating along the interface between LiTaO3 and SiO2. First, it is shown that Stoneley waves can exist for specific cuts and propagation directions. The velocity, electromechanical coupling coefficient, energy concentration, delay time temperature coefficient, and delay time temperature characteristics are calculated. In an SiO2/X‐148°Y LiTaO3 structure, a zero temperature coefficient which is not available for a Rayleigh wave on an LiTaO3 substrate has been realized. In addition, the electromechanical coupling coefficient is larger. Next, a device of this structure has been fabricated. It is confirmed that Stoneley waves can be excited and received by interdigital electrodes. The characteristics observed have been found to agree well with the theoretical predictions. Also, a zero temperature coefficient is obtained with an SiO2/X‐148.5°Y LiTaO3 structure and the quadratic temperature coefficient is about the same as in an ST cut quartz Rayleigh wave substrate.
Radiation‐hardened silicon surface passivation film
Authors: Watanabe Kikuo , Kato Masataka , Nagata Minoru , Okabe Takahiro
Published: July 2007

When an Si bipolar transistor is exposed to γ‐ or X‐rays, degradation of the current gain is a serious problem. The degradation of the current gain is caused by an increase in the base current due to an increase in the surface recombination current. The increase in the surface recombination current is due to SiO2/Si interface states generated at the base surface by irradiation. Mobile positive charges created by irradiation in the SiO2 film are thought to cause the interface state generation. Therefore, a decrease in the mobile positive charges that can reach the interface is thought to reduce the interface state generation. The decrease is thought to be achieved by recombination annihilation and trapping of the mobile positive charges at regions far away from the interface. A double‐layered SiO2 film is proposed to realize this. The film is composed of a thin thermal SiO2 layer and a CVD SiO2 layer which is deposited on the thermal SiO2 because the CVD SiO2 is considered to have high density recombination centers and trap centers. It is found that in the double‐layered SiO2 film, the interface state generation due to irradiation is much smaller than that in a single thermal SiO2 film. This paper describes the effectiveness of the double‐layered SiO2 film for a radiation‐hardened Si surface passivation film.
A new numerical analysis for oversized planar waveguide circuits. iterative method by use of a boundary element source matrix
Authors: Wada Osami , Nakajima Masamitsu
Published: July 2007

A new analytical method is proposed for the electromagnetic field in oversized waveguide circuits. We obtain in sequence reflected waves from waveguide walls for the incident waves into the domain of analysis. By combining them with proper phases up to convergence, we obtain the transmitted electromagnetic field. It is necessary to integrate the source field distribution on the walls. As is done in the boundary element method (BEM), the boundary is subdivided into small elements. We precalculate the contributions received from each unit source and represent them in a matrix form. Then the higher‐order fields are obtained as the products of this matrix and the source field distribution. The iterative calculation to obtain the converged field is performed easily. We formulated a case of the incidence of the TEm0 mode into the H‐plane planar circuit of a rectangular waveguide. The problems of step discontinuities and waveguide corners are analyzed. The results were compared with those obtained by the mode matching and by the boundary element methods. It was found that analysis can be made with less than 1 percent errors in the case of the incidence of low‐order modes in an oversized waveguide of several wavelengths. The present method corresponds to the actual multiple reflections at waveguide walls and provides clear physical meanings. It can be applied to some problems for which the BEM faces a difficulty.
Analysis for reflection from coaxial end attached to lossy sheet and its application to nondestructive measurement
Authors: Nishikata Atsuhiro , Shimizu Yasutaka
Published: July 2007

In this paper we proposed a nondestructive local measurement method for lossy sheet materials which are widely used as radiowave absorbers. We used a coaxial waveguide to measure the reflection coefficient at its end with an attached flange which touches the lossy sheet backed by a metallic foil. We showed an analytical solution for it and several experimental results. For the analytic analysis, we considered isotropic lossy sheets of both dielectric and magnetic materials. We derived definite integrals for the mutual admittance among multiple modes and the reflection coefficient for the coaxial TEM mode. These formulas were evaluated by numerical integrations. Solutions of these integrations generate errors due to terminated matrix operation for a certain finite limit (naturally they are of infinite dimensions). We showed that the precision of the solution was improved by applying Aitken's acceleration method. In practice we used two magnetic lossy sample materials whose dielectric constants and permeabilities were known. Through experimental measurements for these samples we confirmed the validity of the present analysis. Next we applied the present measurement method for dielectric constants for lossy samples with unknown dielectric constants. We indicated that the measurements by the present method had a higher reliability than those by the existing destructive method by using waveguide standing waves.
Observation of elliptical motion in the torsion coupler of ultrasonic motor using optical heterodyne interferometer
Authors: Umeda Norihiro
Published: July 2007

An elliptical motion in the torsion coupler of an oscillator‐type ultrasonic motor has been observed noninvasively by means of an optical heterodyne interferometer. Studies of the elliptical motion in the torsion coupler are important for the research on improvement of the efficiency and optimum design of an ultrasonic motor. However, to date, only microscope observation has been carried out and hence accuracy is not as high as desired. In this paper, an optical heterodyne interferometer based on a frequency‐stabilized transverse Zeeman laser is used for detection of the Doppler shift frequency by an ultrasonic vibration so that the vibration waveform of the torsion coupler has been regenerated. The oscillations of the rotor contact plane and side plane of the end of the beam have been measured individually by an identical optical system. From their amplitudes and the phases, the elliptical loci have been computed. In another method, the oscillations of the two surfaces have been measured simultaneously with two interferometer systems and their elliptical relations have been displayed in real time on an XY oscilloscope. Oscillations at each point on the beam and the variations of the elliptical shape versus the driving frequency of the ultrasonic motor have been observed successfully by the second method.
Detection of CH3OH and CO2 Lasers by Antenna‐Coupled Point‐Contact Schottky Diodes
Authors: Inou Narumi , Yasuoka Yoshizumi
Published: July 2007

Carrier density dependence of the detection abilities of an antenna‐coupled point‐contact Ge diode at 118 μm and 10.6 μm was studied. The optimum carrier densities obtained by experiments were 1016 cm−3 and 2 × 1017 cm−3 for CH3OH and CO2 lasers, respectively.

These results were explained by calculation based on the assumption that the conductivity of the metal is in the relaxation region and that the spreading resistance of the semiconductor is affected by the skin effect, carrier inertia and displacement current.
Characteristics of dispersion‐shifted dual‐shaped core fibers
Authors: Ohashi Masaharu , Kuwaki Nobuo , Tanaka Chihaya , Uesugi Naoshi , Negishi Yukiyasu
Published: July 2007

This paper investigates the dispersion characteristics and bending loss of dispersion‐shifted fibers with dual‐shaped core and α index. It is seen that the bending loss of dual‐shaped core dispersion‐shifted fibers can be smaller than those of α‐index fibers at a fixed condition of splicing loss. The possibility that the bending characteristics of the fiber is as good as or even better than that of conventional single‐mode fibers is indicated. It is also understood that the dual‐shape core dispersion‐shifted fibers are superior to the conventional ones in dispersion sensitivity. Further, it is shown that there is an inverse relation between the dispersion slope and the dispersion sensitivity. The dispersion‐shifted dual‐shaped core fiber was fabricated and its propagation characteristics were measured to confirm its superior performance. The design parameters of dispersion‐shifted fibers for practical uses are given together with typical examples. It is shown that in the practical range, the fiber parameters are determined by the mode field diameter and the cut‐off wavelength.
A lamb wave device for quadrature‐PSK modulation and demodulation
Authors: Toda Kohji , Mizutani Koichi
Published: July 2007

This paper describes a Lamb wave device for quadrature phase shift keying (QPSK) systems. By way of numerical calculations, it is found that the zeroth‐order symmetric mode Lamb wave in a piezoelectric ceramic thin plate has a low dispersion and a large coupling constant. The signal processing device using this mode consists of four delay lines with different acoustic phase delays on a substrate and possesses three functions: phase shifter, phase comparator, and filter. Experimental results are presented for the Lamb wave device for QPSK modulation and demodulation, and they agree well with the operating principle. The data transmission speed of the basic system for modulation and demodulation is 0.8 Mbit/s at the carrier frequency of 5.6 MHz.
Vector finite‐element solution of anisotropic waveguides using novel triangular elements
Authors: Hano Mitsuo
Published: July 2007

A new triangular element is proposed in the vector finite‐element solution of a dielectric waveguide. In the conventional finite‐element expression based on the three magnetic field components, each component is treated independently by continuous elements. The elements used in this paper are subject to the condition that the longitudinal field components are continuous between adjacent elements and the transverse components have tangential components continuous at the element boundary. In this method, as many zero eigenvalues as the number of unknowns of the longitudinal components are generated. However, all the remaining nonzero eigenvalues correspond to the physical modes and no spurious solutions typical in the conventional vector finite‐element solutions are generated. The present elements are suited for representation of the forced boundary conditions, and the analysis region can easily be applied to an arbitrary waveguide. To investigate the validity and effectiveness of the present method, it was applied to a hollow cylindrical waveguide, a dielectric loaded rectangular waveguide, an anisotropic refractive index dielectric waveguide, and a ferrite loaded square waveguide.
Analysis and eliminating method for undesirable setting of magnetic amplifier on single‐ended DC‐to‐DC converter
Authors: Onda Kenichi , Abe Koojin , Matsuda Yasuo , Amano Hisao
Published: July 2007

For a single‐ended dc‐to‐dc converter using a magnetic amplifier, an undesirable setting of the magnetic amplifier during the off‐period is analyzed. It is found that the C and R snubbers are installed on the main switch and on the rectifying diode on the secondary wiring of the transformer discharge during the off‐period of the main switch, and then this discharge current undesirably sets the magnetic amplifier. The undesirable setting quantity increases if a transformer with a smaller magnetization inductance or a saturable reactor with a smaller coercivity is used. Hence, the effect is more pronounced in a converter operated at a higher frequency. The undesirable setting is larger in a converter with a lower output voltage. From these results, a new circuit is proposed in which the coercivity of the saturable reactor can be increased effectively by installation of a winding for flowing the reset current in a magnetic amplifier. It is confirmed that this system can reduce the undesirable setting.
Amorphous cobalt ferrite films with high perpendicular anisotropy
Authors: Hiratsuka Nobuyuki , Sugimoto Mitsuo
Published: July 2007

Amorphous cobalt ferrite (CoFe2O4) films were formed by a two‐source vacuum evaporation technique, using CoFe2 alloy and P2O5 as the source materials. It was found that the crystalline phase and perpendicular anisotropy constant (Ku) were dependent on the pressure of P2O5 during film deposition. When the pressure of P2O5 was higher than 5 × 10−3 torr, the film was amorphous. When the pressure of P2O5 was higher than 8 × 10−3 torr, the film had perpendicular anisotropy. The maximum perpendicular anisotropy constant was obtained (1.8 × 105 erg/cm3) when the film was formed under a P2O5 pressure of 10−2 torr. This value is one order of magnitude higher than that of amorphous nickel ferrite films. The cause of the perpendicular anisotropy is thought to be due to the columnar structure formation of Co2+ and Fe2+ perpendicular to the film surface. When the amorphous CoFe2O5 film with perpendicular magnetization is heat‐treated under the P2O5 pressure (Pp2O5) of 10−2 torr, Ku also increases with the increase of the treatment temperature; Ku of the amorphous CoFe2O5 film with perpendicular magnetization is comparable with those of barium ferrite and single crystalline CoFe2O4 films. Therefore, this film can be used for the magnetic recording media.
Optimization of mask layout for high–speed IIL device
Authors: Sawada Shigeki , Shimizu Keiichiro , Manabe Kenji
Published: July 2007

Optimization of mask layout for an IIL device with a P‐well base was carried out by investigating the influence of the mask pattern on the gate delay time, using the experimental and simulated results. The simulation of the gate delay time was designed to obtain the electrical properties based on the IIL gate structure and the impurity distribution. Using the stored charge model, the high injection effect and the distributed base resistance of an NPN transistor were taken into account. The experimental and simulated results were in good agreement. The high‐speed operation of an IIL device is dependent on the decrease of the collector and emitter junction capacitance of an NPN transistor by the decrease of the collector and base areas, the decrease of the stored charges in the emitter, and the emitter junction capacitance by optimization of the separation between the base and N+ collar and of epi‐thickness, and the suppression of the influence from the distributed base resistance by eliminating the excessive base current using optimized base width in an injector PNP transistor.
Optical integration of a fiber laser doppler velocimeter
Authors: Toda Hiroyuki , Haruna Masamitsu , Nishihara Hiroshi
Published: July 2007

This paper describes an optical integrated circuit (optical IC) for a laser Doppler velocimeter (LDV) in which a polarization‐maintaining optical fiber is used to pick up a signal light. To realize more compact and stable heterodyne optics for velocity measurement, a waveguide interferometer including a frequency shifter, a TE/TM mode converter, and a TE/TM mode splitter is integrated on a Z‐propagating LiNbO3 substrate 32 × 7 mm2 in size. In the fabrication of the optical IC, a 3‐μm wide waveguide pattern was made by a laser‐beam direct writing method. The polarizationmaintaining optical fiber was butt‐coupled to the output waveguide of the optical IC. Using the fabricated optical IC, the Dopplershifted signal light was detected with the signal‐to‐noise ratio of 25 dB in the velocity measurement of a moving mirror. The configuration of the optical IC, properties of key waveguide components, fabrication and velocity measurement characteristics of the optical IC, are described in this paper.
Measurement of three‐dimensional shape and section of object on turntable by position‐sensitive device
Authors: Nakashima Wataru , Nagamura Eiji , Aida Teizo
Published: July 2007

This paper considers an object moving on a belt‐conveyor or on a turntable, and describes a system which measures with a high speed its shape and the cross section in horizontal and vertical directions. In the measurement, the object is scanned with a high speed by He‐Ne spotlight through a high‐speed rotating mirror with 10 mirror‐faces. The object is placed on a turntable and rotated 360 deg by a stepping motor. The two‐dimensional information of the scanned point is acquired by PSD. The operation is performed in synchronization to the scanning by a personal computer, and the cylindrical coordinates (r, z, θ) of 4800 points on the object are determined with as high a speed as 980 ms (200 μs per coordinate). A feature of this study is that the speed is improved by combining a high‐speed rotating mirror and a high‐speed PSD. Another feature is that the reference table for coordinate determination is stored so that the speed of the computation can be improved. At present, approximately 3 min is required by BASIC to display the coordinates, but the cross section can be displayed in 0.4 s using the machine language.
Design and fabrication of GaAs hall IC with SCFL Schmitt Trigger
Authors: Itakura Keijiro , Asada Hiroaki , Ueda Daisuke , Takagi Hiromitsu
Published: July 2007

A GaAs monolithic Hall IC with superior temperature characteristics has been designed and fabricated by taking advantage of such GaAs material properties as large bandgap and high electron mobility. This IC is designed with SCFL circuits, operates with only a 5‐V power supply, and switches ON and OFF depending on the magnetic field intensity. In addition, it contains a Schmitt trigger circuit to prevent a malfunction by magnetic noise. As a result of designing for low power consumption, the power/current of the IC is approximately 17 mW/3 mA. According to the measurement, the magnetoelectric conversion characteristics and the power consumption of the IC do not show a noticeable change even at the ambient temperature of 150°C.
Theoretical analysis of resonant tunneling through finite superlattices
Authors: Kato Fumio
Published: July 2007

A theoretical study has been carried out with a view to understanding the resonant tunneling phenomena in superlattice structures. For a general potential distribution, the resonance condition is derived and the relationship is found between the resonance levels and the subbands in an infinite superlattice. Especially, the relationship is studied between the resonance characteristics of a unit superlattice section with an arbitrary potential distribution and those of an n‐period superlattice made of n stages of unit superlattices. It is found that the discriminating function of the n‐period superlattice is given by a Chebyshev polynomial of that of the unit section. Hence, if any potential distribution (including an asymmetric one) is repeated at least twice, a resonance level can always be generated in each subband (with a zero bias voltage). A method based on this fact is presented for generating a resonance at an arbitrary energy level in an n‐period superlattice. Further, by way of these discussions, it is pointed out that there exist higher‐order resonances. An example for this phenomenon is presented.
Polymer thin film waveguide polarizer with a‐Si: H clad
Authors: Kato Isamu , Sugiyama Yasuyuki , Sugita Kotaro
Published: July 2007

A device has been fabricated by loading an a‐Si:H film on a polymer thin‐film optical waveguide via a low index buffer layer. As an application to an optical functional device, this structure has been investigated as to its characteristics as a TE‐TM mode waveguide polarizer. In the present waveguide polarizer, the transmission mode can be selected by varying the thickness of the a‐Si:H film. In addition to the TE mode pass polarizer, a TM mode pass polarizer has been fabricated and studied which is not easily realized with a metal loaded structure. Both a slab waveguide and a practically important three‐dimensional waveguide (width 100 μm, 50 μm, 10 μm and 5 μm) have been used. In the case of a slab waveguide, both the TE mode and TM mode pass polarizers have exhibited an extinction ratio of 30 dB. In the case of a three‐dimensional waveguide, the extinction ratio is somewhat lower because the electric field distribution of the guided mode is a hybrid of the TE and TM modes. Nevertheless, the polarizer has a good extinction ratio.
An analysis of semiconductor waveguides with strip‐shaped plasma and their applications
Authors: Shimasaki Hitoshi , Tsutsumi Makoto , Kumagai Nobuaki
Published: July 2007

When a high‐resistivity semiconductor is used as a waveguide medium which is illuminated optically so that the electron‐hole plasma is excited, its permittivity changes and the control of the propagation characteristics of the millimeter‐wave becomes possible. This paper studies the effect of the plasma layer width on the propagation characteristics in a waveguide with plasma induced on the grounded semiconductor slab. The hybrid guided mode was analyzed by means of the mode matching method. It is found that the attenuation of the wave increases as the plasma layer width is decreased if the plasma density per unit area is more than 1017.5 m−2. Further, the obtained results were extended and the characteristics of an optically controlled coupler made of dielectric waveguides were analyzed.
Analysis of high‐power short millimeter wave generation by reflection at the front of a relativistic electron beam
Authors: Ishido Yoshinari , Shiozawa Toshiyuki
Published: July 2007

The mechanism of generating high‐power short millimeter waves by means of reflection from the front of a relativistic electron beam is clarified quantitatively by using a two‐dimensional model made of two parallel conducting plates and a relativistic electron beam with arbitrary thickness sandwiched between them. First, in the laboratory frame, an incident wave of the lowest‐order odd symmetric TE mode is assumed. By way of the Lorentz transformation, the incident wave is transformed to the beam frame. Next, in the beam frame, higher‐order modes are considered for both the reflected and transmitted waves. By applying the mode matching method to the boundary conditions at the beam front, the electromagnetic field components of the reflected modes are derived. Then, when the Lorentz transformation is applied to these reflected waves, the electromagnetic field components of the reflected wave in the laboratory frame are obtained. Finally, the reflection characteristics are investigated numerically. It is found that the reflection coefficient becomes large in the total reflection region of the second‐order mode as well as in the total reflection region of the dominant mode and that the former has a broader bandwidth with more uniform characteristics than the latter. Also, there exists an optimum value of the beam thickness for which the power reflection coefficient is maximum.
Compression of picosecond optical pulses from a strongly RF modulated InGaAsP DBR diode laser using a gires‐tournois interferometer
Authors: Zhang Nai , Terukina Asao , Ito Hiromasa , Inaba Humio
Published: July 2007

In ultrashort optical pulse generation by gain switching of semiconductor lasers, the chirping phenomenon that is the shift in the oscillation wavelength based on refractive‐index changes due to carrier fluctuations, is well known. Using this chirping phenomenon, it is possible to have direct pulse compression in conjunction with a dispersive device. However, since the output power of semiconductor lasers is usually smaller than that of other types of lasers, efficient optical compression systems are indispensable. In this paper, use of the dispersion of Gires‐Tournois (GT) interferometer is proposed and its dispersion characteristics are investigated. Then, using the GT interferometer, 6.5 ps optical pulses are obtained by the compression of the chirped 30 ps optical pulsed from a distributed Bragg reflector (DBR) InGaAsP laser at 1.3 μm band by application of a strong RF modulation. The corresponding compression ratio is 4.6 with the peak power of 200 mW. Therefore, the usefulness of GT interferometer as the compressing device is confirmed.
Equivalent circuit model for positive/negative reflection—type SAW reflectors
Authors: Mitobe Seiichi , Koshiba Masanori
Published: July 2007

An analysis method is proposed herein which uses an equivalent circuit model as a means to evaluate positive/negative reflection‐type (PNR) SAW reflectors. The PNR reflector consists of reflecting elements which have 180° phase difference (positive and negative reflection coefficients). Each element is spaced with a period of one‐quarter wavelength. Compared with the conventional reflectors, these new reflectors have larger reflection‐efficiencies. In this paper, an equivalent circuit model for the PNR reflectors is presented. Circuit parameters can be determined theoretically by applying the finite‐element method to an infinite array. Examples are computed for two kinds of PNR reflectors on 128° Y‐X LiNbO3 or ST‐X quartz substrate. For each of them, we determined the circuit parameters and analyzed the reflection characteristics. We obtained good agreement between theoretical and experimental results.
A programmable optical demultiplexer using a 32–element photodiode array
Authors: Kinoshita Takeshi , Sano Ko‐Ichi
Published: July 2007

This paper describes the design and performance of a programmable optical demultiplexer which can compensate the influence of: (1) scattering in the wavelength of an optical source; and (2) wavelength fluctuation of the optical source caused by temperature change, by controlling the branching characteristics in accordance with the wavelength of the optical source. In this multiplexer, a 32‐element Si photodiode array was used to carry out programmable control of the branching characteristics. This optical demultiplexer has the following merits: (1) a wide channel passband is not needed; and (2) since the passband‐center wavelength of this multiplexer is adjusted to the wavelength of the optical sources, fine tuning of the branching characteristic in fabrication is not needed. The fabricated programmable optical demultiplexer has a channel wavelength spacing of 4.0 nm, an insertion loss of 8.0 dB which includes a loss of 3.9 dB due to the detection loss caused by the gap between two photodiodes composing the PD array, and a passband width of 2.8 nm. It was confirmed also by a digital transmission experiment (32 mB/s, RZ signal) that this demultiplexer can maintain its optimum branching characteristics for any wavelength deviation in the optical sources.
High speed, zero—bias modulation of low threshold MQW laser diodes
Authors: Nakamura Masaru , Furuyama Hideto , Kurobe Atsushi
Published: July 2007

In realizing high‐speed and very dense opto‐electronic integrated circuits with optical connecting inside and between the LSI chips, investigations are made on how to avoid the need for output power stabilizing and biasing circuitry of present semiconductor lasers. If it becomes possible to reduce sufficiently the threshold current of semiconductor lasers, in comparison to the driving current, its output stability against temperature variations improves and the delay time to switch it on can be reduced even at zero bias pulse driving. Using a GaAs/GaAlAs multiquantum well laser with threshold current of 4 mA, high—speed, zero‐bias and output control—free modulation experiments were performed. The requirement in optical communication systems for the output power variations to be less than ±0.5 dB was satisfied because for the temperature range of 0 – 50°C and at 20 mA driving current, the variations were limited to +0.45 –0.45 dB. At zero biasing the switch on delay of 150 ps was realized at pulse current of 34 mA with sufficiently good response to a 1 Gbps NRZ signal. The spectrum showed stable longitudinal multimode oscillation, and from its poor coherency, it was expected that stability against the returning light would be good. It is believed that obstacles in development of opto‐electronic circuits can be removed using semiconductor lasers with threshold current of a few milliamps.
Selective embedding epitaxial technique of highly resistive InP for OEIC's device isolation
Authors: Sugou Shigeo , Kasahara Kenichi , Murata Shigeru , Koizumi Yoshihiro , Kuroda Naotaka , Yanase Tomoo , Kato Yoshitake
Published: July 2007

A device isolation layer for an opto‐electronics integrated circuit (OEIC) is desired to have not only an electrically isolating function but also an optical confinement function and low‐defect interface formation function. This paper describes a selective embedding epitaxial technique of highly resistive Fe‐doped InP by grown halide vapor phase epitaxy (VPE) for device isolation layer which has these functions. First, growth technique and growth conditions are examined for highly resistive Fe‐doped InP by grown hydride VPE, and it is shown that electrical characteristics sufficient for device isolation can be obtained. Also, characteristics of selective embedding growth are examined, and it is shown that a planar selective embedding growth is possible over a wide range of growth conditions. Furthermore, good results are obtained by applying this highly resistive layer to semiconductor lasers and OEIC devices.
Efficient finite—element formulation for analyzing the propagation characteristics of waveguides
Authors: Hano Mitsuo
Published: July 2007

This paper considers the finite‐element vector analysis of the dielectric waveguide, and derives a new finite‐element representation through a modification of the finite‐element representation by three components of electric on magnetic field. In the traditional finite‐element representation of this kind, the wavenumber k02 in free space is obtained as an eigenvalue for given propagation constant β. Consequently, a large amount of computation is required to determine the cutoff frequency of the waveguide or to analyze the waveguide with a medium with frequency dispersion. In this paper, a finite‐element representation for k0 is derived with β/k0 as the parameter, as well as the representation for β with k0 as the parameter. In those finite‐element representations, the matrix size is twice that of the traditional representation, but the approach is useful in terms of the computation time compared with the iterative method, since the solutions are obtained by one step. The finite‐element representation has essentially a feature that the physical and the spurious solutions can easily be discriminated by imposing the condition that the eigenvalue of the physical solution is real. Thus it is indicated that the finite‐element analysis based on the variational expression for the three components of electric or magnetic field is very versatile, where the solutions can be obtained for various parameters as required.
Coupling characteristics of crossover arranged rectangular dielectric waveguides
Authors: Matsumura Kazuhito , Tomabechi Yoshiro , Tsuchiya Noriaki
Published: July 2007

The coupling characteristics of two rectangular crossed‐over dielectric waveguides located on different parallel layers which presented a constant angle of intersection on a projection plane are analyzed. When two open waveguides were situated in proximity, each waveguide is mutually affected by the presence of other waveguide. Distributions of propagating modes in each waveguide were perturbed. This paper considers such perturbations using the authors' analysis method for a coupled system in a parallel arrangement. The coupled part is approximated by a step‐like approximation, and the dependence of the coupled electric power along each waveguide on the angle of intersection and the separation distance between upper and lower guides were clarified. Good agreement was obtained between calculated values and experimental measurements, in particular, the case of a tight coupling for a small separation distance between upper and lower waveguides and for the case of a large separation distance with a small angle of intersection with a long coupling part along the axial direction of the waveguides. This paper has improved greatly the authors' previous calculation results in which variational calculus was used on the assumption of a weak coupling. These results are considered to contribute to designing coupled circuits between upper and lower layers of integrated circuits for optical integrated circuits.
Preparation of superconducting thin films of a new oxide system by rf magnetron sputtering
Authors: Setsune Kentaro , Kamada Takeshi , Hirochi Kumiko , Adachi Hideaki , Wasa Kiyotaka
Published: July 2007

La‐Sr‐Cu‐O, Y‐Ba‐Cu‐O, and Er‐Ba‐Cu‐O ceramic thin films are formed by rf magnetron sputtering and subsequent annealing. The sputtering condition, the crystallinity of the films and the superconductive characteristics of the films were evaluated. The composition of the films depended strongly on the partial pressure of oxygen in the sputtering gas, and the resistivity of the films depended on the total sputtering gas pressure. The crystallinity of the films depends on the substrate temperature during deposition and is not affected by post‐annealing. The preferential growth of films occurred on sapphire substrates heated up to the temperature of higher than 650°C in a [001] direction which is normal to the substrate. Even when Er is substituted for the Y element in the Y‐Ba‐Cu‐O system, the film can be prepared under conditions similar to that of depositing a Y‐Ba‐Cu‐O film.
Equivalent circuit analysis of performance of acousto—optic deflector using liquid—loaded interdigital transducer
Authors: Toda Kohji , Urabe Heijiro
Published: July 2007

An acoustic wave can be generated in a liquid by operating an interdigital transducer (IDT) at a solid‐liquid interface. This paper describes the operation characteristics of an optical deflector in which the acoustic wave thus generated is used as a grating. By representing the admittance characteristics of the IDT as a function of the relative acoustic impedance of the liquid used as a load, the evaluation of the electroacoustic conversion efficiency and the characteristics as an AO device is simplified. By means of a broadband IDT with chirped electrodes, an acoustic diffraction grating is formed in water. Investigations of the characteristics as an acousto‐optic deflector reveal excellent results in diffraction efficiency, deflection bandwidth and resolution number.
Fiber‐optic gyroscope by interference fringes of bifocal lens optical system
Authors: Okada Sadayuki , Sonobe Hisao , Miyazaki Rokuroo
Published: July 2007

The interference‐type fiber‐optic gyroscope detects rotating angular velocity by means of interference between two optical signals traversing a fiber‐optic loop in opposite directions. In one method, the optical paths of two signals are completely equalized. In another method, the interference fringes obtained by adjustment of the lens location are used. This paper describes the second method. By means of a microoptic system using a bifocal lens, linear interference fringes are formed. After these fringes are read by a line scanner, the waveform is Fourier transformed so that the rotating angular velocity is derived from the obtained phase‐shift quantity. The results of the experiment indicate that the relationship between the input angular velocity and the output is linear over a broad range. A rotation of 0.02 to 182 deg/s was detected and the minimum output ripple at the time of detection was ±0.015 deg/s. The drift of temperature change was 0.03 deg/s per 0.01°C, and hence this method is sensitive to temperature variation.
Pulse operation of GaAs/ALGaAs surface‐emitting laser‐type optical threshold device
Authors: Nitta Jun , Koyama Fumio , Iga Kenichi
Published: July 2007

This paper describes the fabrication and basic properties and optical property of a GaAs/AlGaAs surface‐emitting laser‐type optical threshold device. Initially, a GaAs/AlGa‐As surface‐emitting optical threshold device with a mesa cap ring electrode structure (active layer of 3 μm and absorption layer of 0.5 μm) was fabricated and it was found that the device had a threshold current of 430 mA under room temperature pulse operation. To confirm whether the absorption layer was effective, the slow pulse response was calculated theoretically. Then, it was confirmed that an asymmetrical optical pulse can be obtained experimentally. Then a nonlinear optical input‐output was obtained at the input optical density of about 100 W/cm2.
Matrix solver with three‐dimensional VLSI technology
Authors: Kurokawa Takakazu , Ajioka Yoshiaki , Aiso Hideo
Published: July 2007

A “Matrix Solver” is proposed for solving any type of linear equation over GF(2), with applications in cryptography and Error Correcting Codes.

A design of the Matrix Solver is discussed as one of the appropriate applications of 3‐D VLSI systems. First, an algorithm based on the Cramer method combined with the Chio method is constructed following six new criteria for 3‐D VLSI algorithms. Second, a 3‐D layout and an implementation of a 3‐D structured breadboard model of the Matrix Solver are discussed.
Alpha‐particle induced source‐drain penetration (Alpen) effects
Authors: Hisamoto Digh , Toyabe Tohru , Takeda Eiji
Published: July 2007

The source‐drain penetration (ALPEN) effect, which is a new α‐particle induced soft error mechanism, was found and investigated by using a 3‐dimensional simulation. When an α‐particle penetrates the source‐drain region of a short channel MOSFET, the funneling field extends from both electrodes and the channel potential becomes distorted, thereby causing a funneling current. Since this current causes a charge leakage, it causes “0” → “1” reverse mode soft error in the DRAM in addition to the conventional α‐particle soft error. This error mechanism was also confirmed experimentally. The influence of this effect on future devices is predicted, and it has been shown that a device with a channel length shorter than 0.5 μm is influenced strongly by this effect. Therefore, it was concluded that this effect is an important factor in the scaling limit of a device.
Influence of the Ta migration on dielectric properties of anodized Al‐Ta(N)‐Al trilayered oxide films
Authors: Dobashi Tsuyoshi , Umezawa Toshiji , Sasaki Katsutaka , Noya Atsushi
Published: July 2007

A trilayered dielectric thin‐film capacitor with an A1‐A12O3‐Ta2O5 (N)‐A12O3‐A1 structure was formed by anodizing a trilayered thin‐film, A1‐Ta(N)‐A1, deposited by RF diode sputtering. During the anodization procedure, Ta migrates into the aluminum oxide layer. The effect of Ta migration on the stoichiometry of the aluminum oxide was investigated by AES/XPS analysis before and after heat treatment. The results of the analysis showed that the migrated Ta's were in metallic and oxide states. However, the majority of the migrated Ta was in the metallic state, while the majority of A1 was in an oxide state. When the sample was heat treated in air at 300°C, oxidization of A1 progressed, but Ta tended to be reduced. Therefore, when a capacitor with a thick Ta film is heat treated, tanδ increases. If the thickness of the Ta layer is chosen properly, the stoichiometry of the A1‐oxide improves, resulting in a low tanδ (tanδ = 0.0018).
Direct butt coupling type of LED module with multiple output fibers
Authors: Sunada Tadasu
Published: July 2007

With regard to domed LEDs, this paper describes an LED module with multiple output fibers arranged radially around a source using a direct butt coupling system. It is found that the optical coupling efficiency is improved by tilting the fiber so that it is oblique to the source. This is done also for the direct butt coupling LED module without lens, and an optimum module structure is established using this coupling method. A detailed analysis is carried out on the fiber coupling efficiency for domed LEDs with various active layer depths d, and the optimum active layer depth to realize multiple and high outputs is estimated to be dO = ∼ 45 μm considering the SiO2 insulating layer. A fabricated LED module with ten output fibers using a domed LED (dome radius of 200 μm) with the depth of d = 45 μm, gives a high optical power of about 120 m in each fiber.
Tunnel‐oxide breakdown characteristics of floating‐gate‐type EEPROM
Authors: Sato Kazuo , Fukuzaki Yoshiki , Hatakeyama Shinichi , Ikeda Nobuyuki
Published: July 2007

This paper aims at the analysis of the breakdown characteristics and the mechanism of the tunnel oxide breakdown by the iterative rewriting of floating‐gate‐type EEPROM. The relation of number of rewritings until the tunnel oxide breakdown to the rewriting condition and the process condition is investigated. As a result, an approximate relation logNαQfgis derived, whereNis the number of rewritings until the tunnel oxide breakdown andQfgis the tunnel charge in rewriting. It was seen also thatNis nearly proportional to the life of the tunnel oxide determined from TDDB characteristic. It is estimated that the major cause of the tunnel oxide breakdown is the trap of the electron in the tunnel oxide. The trapped electron can easily be released by the thermal treatment of some 5 hours, improving the life of the number of rewritings until breakdown.
Transient temperature response of avalanche diodes against lightning surges
Authors: Satoh Hidetaka
Published: July 2007

Avalanche diodes are used frequently as lightning surge protectors because of their high‐speed response and constant voltage suppression characteristics. In this paper, a transient temperature response analysis is carried out with a view to determining the relationship between the temperature and the failure under the application of lightning surge. In the analysis, the nonsteady‐state thermal conduction equation is solved by the finite difference method. The nonlinear elements included in the analysis are the temperature dependences of the thermal conductivity thermal capacity and breakdown voltage of the avalanche diode. It is confirmed that the theoretical results of the temperature and the voltage drop of the avalanche diode agree well with the measured data. It is found that the peak temperature in the avalanche diode under the application of a standard lightning surge (waveform: (10/200) us and (10/1000) us) appears near the half‐value decay time and that the failure of the avalanche diode depends on the peak temperature, and the critical failure temperature is estimated to be about 490 degrees.