bluuebunny/crossref_metadata_2025_split huggingface dataset:
AIGaAs/GaAs heterojunction hall device
Authors: Taguchi Takashi , Sugiyama Yoshinobu , Tacano Munecazu 
Published: July 2007

AbstractSince the two‐dimensinoal electron gas in the modulation‐doped A1GaAs/GaAs heterojunction is as thin as 10 nm and the electron mobility is over 7000 cm2/Vs, this structure is suitable for highly sensitive Hall devices. As the room temperature device the following conditions must be satisfied: the carriers should be supplied sufficiently to the two‐dimensional gas, but no excess carriers should exist in the highly doped A1GaAs layer. Thus the number of the two‐dimensional electron gas should have little dependence on the temperature. The fabrication conditions of the heterojunction and the magnetic property of the devices are discussed. The product sensitivity and the figure of merit of the heterojunction Hall device were 1000 V/AT and 27 (V/A)1/2/T, respectively. These values are comparable to those of InSb Hall devices. The temperature dependence of our device was three times less than that of the InSb Hall device.
Two‐dimensional numerical analysis of gaas MESFET with a p‐buffer layer
Authors: Araki‐Mishima Nobuko , Yamaguchi Ken 
Published: July 2007

AbstractTo suppress the threshold voltage shift of GaAs MESFET's in a shorter channel region, a two‐dimensional numerical analysis of the FET structure with a p‐buffer layer is carried out. As a result of the analysis, it is clarified that the insertion of the p‐buffer layer is effective in preventing the carrier penetration in the substrate. In analyzing the electrical properties as a function of the buffer layer thickness, it is found that the substrate current which flows beneath the p‐channel layer, decreases with an increase in the buffer layer thickness and that the threshold voltage shift is suppressed with the increase. As the buffer layer thickness increases, the transconductance increases. Moreover, as the buffer layer thickness increases, the gate‐substrate capacitance increases. Therefore, to obtain a high cutoff frequency, it is necessary to optimize the buffer layer thickness.
Method of materials design for I‐III‐VI2 chalcopyrite‐type mixed crystal semiconductors
Authors: Nomura Shigetaka , Endo Saburo , Irie Taizo 
Published: July 2007

AbstractBinary 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

AbstractIn 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

AbstractA 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

AbstractA 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

AbstractBy 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

AbstractA 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

AbstractWhen 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

AbstractA 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

AbstractIn 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

AbstractAn 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

AbstractCarrier 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

AbstractThis 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

AbstractThis 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

AbstractA 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

AbstractFor 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

AbstractAmorphous 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

AbstractOptimization 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

AbstractThis 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.