bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of multiquantum barrier (MQB) and experimental verification of electron wave reflection by MQB
Authors: Takagi Takeshi , Koyama Fumio , Iga Kenichi 
Published: July 2007

AbstractWith a view to form a clad layer corresponding to the shorter wavelength of an AlGalnP visible laser, the trapping effect of the carrier by the introduction of the multiple quantum barrier (MQB) is discussed. It is found that the hypothetical barrier by the MQB can be made higher if both the well layers and barrier layers comprising the MQB are thinner. The effectiveness of the MQB also is confirmed at the actual barrier height experienced by the electrons in the active layer considering the Fermi level of the MQB region. Further, it is found that for a shorter wavelength, the modified MQB is useful where the potential difference between the well layer and the barrier layer of the MQB is large and the wavelength can be as short as 600 nm.Also, as an experimental verification of the effect by the MQB, the PL using a GaAs/AlGaAs system and theI‐Vcharacteristic of then‐i‐ntunnel diode are used for evaluations. As a result, the carrier‐trapping effect by the MQB is confirmed. Further, it is confirmed also that the height of the hypothetical barrier by the MQB almost coincides with the value obtained by the computation.
Scattering from strip gratings with surface resistance: In the case of general anisotropic substrates
Authors: Asai Masamitsu , Ozaki Akira , Yamakita Jiro , Sawa Shinnosuke 
Published: July 2007

AbstractThis paper analyzes the problem of scattering of a plane electromagnetic wave by a resistive strip grating placed on a multilayered anisotropic substrate. As the method for analysis, the procedures by Teitler and Berreman which can handle the electromagnetic fields in anisotropic medium are extended to which the space harmonic expansion is applied. The currents on the resistive strips are determined by applying Galerkin's method to the resistive boundary condition on the plane with a strip grating. Numerical examples are presented for the reflection coefficients and diffraction efficiencies. First, the results are given in comparison with the data from other publications in the case where the grating is in air or on a grounded dielectric substrate. Afterward, the examples with anisotropic media are presented.
Micron‐order structures in anodized nondegenerate p‐type silicon
Authors: Motohashi Akira , Kinoshita Akira , Aoyagi Hidekazu , Satou Akinobu 
Published: July 2007

AbstractIn addition to the previously reported angstrom‐order porous structure, the micron‐order porous structure was found in anodized silicon. The micron‐order structure can easily be observed by a scanning microscope if the anodized silicon is etched by using weak acid. The structure can be divided into the columnar structure perpendicular to the layer, the roof structure covering the layer surface, and the needle structure parallel to the columnar structure. Shallow depressions are present at the interface between the layer and substrate. The needle structure is strongly dependent on the temperature of the anodizing chemical (HF).
Fabrication and characterization of erbium‐doped silica single‐mode fibers
Authors: Shimizu Makoto , Yamada Makoto , Horiguchi Masaharu 
Published: July 2007

AbstractThis paper discusses erbium‐doped (Er‐doped) optical‐mode silica fibers for which vigorous research efforts have been carried out in recent years. The fabrication techniques and the amplification characteristics with semiconductor lasers used as the excitation source are investigated. As the fabrication of Er‐doped optical fibers, the vapor axial deposition (VAD) method, which is one of the fiber manufacturing techniques, is used. The rare earth doping into the porous material (in vapor phase) by using this method and the possibility of controlling the Er concentration (up to about 1000 ppm) are considered.As the evaluation of amplification characteristics, experimental results of the dependencies upon the pumping wavelength and Er concentration are presented. In particular, in regard to the dependency upon the Er concentration, which is quite important in highly efficient amplifiers, it is shown that there is a serious degradation in the amplification characteristics when the concentration is increased, even at the low doping level of 500 ppm. The deteriorative mechanisms also are discussed.
Reduction of crosstalk errors in a polarization interferometric optical heterodyne fiber sensor
Authors: Kurosawa Kiyoshi 
Published: July 2007

AbstractIt has been proposed that the dual‐frequency optical sources with mutually orthogonal linear polarizations be used and that the optical heterodyne method be applied in the measurement of the birefringence of optical sensors.This paper presents the theoretical and experimental investigation results of a new and easy technique which reduces the measurement errors caused by the crosstalk between the polarization states. The technique is based on the adjustment of the contribution of the polarizations to the light signal by changing the azimuths of the signal and reference analyzers included in the measurement setup. In this way, the effect of the interference due to the crosstalk is reduced.To evaluate the performance of the proposed technique, experiments are conducted which use the dual‐frequency light source comprised of a semiconductor laser, an acousto‐optic modulator, a polarization‐maintaining fiber, etc. As a result, the effectiveness of the technique and its validity are confirmed by the experimental data.
Analysis on impedance characteristics of a photo‐conductive film using distributed parameter circuit model
Authors: Kiwaki Hisatomo , Imada Hiroshi , Ito Masayasu 
Published: July 2007

AbstractIn the measurement of AC impedance of a photo‐conductive layer, the sample is sandwiched between a metal substrate and a transparent conductive surface film. A conductive ring is contacted at the outer edge of this transparent film, forming one electrode. Equivalent parallel resistance and equivalent parallel capacitance representing the bulk properties are calculated from the measured impedance assuming a lumped constant circuit.However, in this method, an error due to the surface impedance of the transparent conductive layer increases with frequency and reaches nonnegligible value at high frequencies.In this work, the impedance is theoretically calculated using a distributed constant circuit model and the error contained in the equivalent parallel resistance and parallel capacitance from assuming a lumped constant circuit is clarified.On the other hand, this theory can also be used for the output calculation of photovoltaic device. The design of short output current, open output voltage, and optimized load is also discussed.
Characteristics of microwave planar transmission lines using superconducting oxide films
Authors: Konaka Tsuneo , Sato Makoto , Asano Hidefumi , Kubo Shugo , Nagai Yasuhiro 
Published: July 2007

AbstractIt is expected that the superior high‐frequency characteristics, such as low loss and low dispersion, of superconducting oxides are applied to microwave circuits. However, low‐loss superconducting oxide films can only be fabricated on limited types of substrate materials using present technologies. Therefore, the dielectric constant, dielectric loss, and thickness of substrate materials place severe limitations on the circuit design and the propagation characteristics.This paper discusses the attenuation constants, characteristic impedances, and wiring density of three fundamental planar transmission lines, namely, stripline, microstrip line, and coplanar waveguide fabricated on substrate materials MgO and LaAlO3. This discussion is based on the TEM and quasi‐TEM analysis procedures. The thin films with low surface resistances have been fabricated on MgO and LaAlO3. It is concluded that the microstrip line is suitable for fabricating a low‐loss transmission line and the coplanar waveguide on a low dielectric constant substrate is suitable for high‐density wirings.Also measured were the characteristics of the half‐wave transmission line resonators of these three transmission line configurations, which are made of EuBa2Cu3Ox thin films on an MgO substrate. The attenuation constant of 50 Ω, 50‐μm wide coplanar waveguide is 9.7 × 10−3 Np/m (8.4 × 10−2 dB/m) at 3.9 GHz and 28 K. This value is two orders of magnitude lower than that of the copper transmission line.
Properties of (CdZn)s alloy semiconductor films grown by sputtering
Authors: Yano Mitsuaki , Gyohten Shigekazu , Ochi Hi‐Izu , Kaku Shukichi 
Published: July 2007

Abstract(CdZn)S alloy semiconductor thin films were deposited by sputtering for the application to solar cells and the deposition conditions were investigated to obtain n‐type low‐resistivity films with high visible light transmission. (CdZn)S thin films with a chemical composition close to stoichiometry were obtained by using a composite sintered target of sulphur‐rich CdS and ZnS.When a CdS film was deposited on a glass substrate under the optimum condition, the film was a polycrystalline film with highly oriented grains whose diameter was 200 nm. The composition ratio of (CdZn)S could easily be controlled and was close to the molar ratio of Cd to Zn in the target. In2S3 and CdCl2 were used as the n‐dopant. CdCl2 provided an excellent doping property without degradation of the film quality although In2S3 tended to segregate in the form of CdIn2S4. When a CdCl2‐doped Cd0.8Zn0.2S film was deposited under the condition optimum for CdS deposition, the bandgap was 2.65 eV and the resistivity was 10 Ωcm. Therefore, this film can be promising as the window material for a heterojunction solar cell.
Optimization method for black and white representation in phase‐plate mode STN‐LCDs using measurements of polarized lights
Authors: Komura Shin‐Ichi , Nagae Yoshiharu 
Published: July 2007

AbstractA method of measurement for an elliptic polarization was developed; and, based on the measured results, an optimization was carried out for the black and white representation of the phase plate mode STN‐LCD. It was confirmed that a good black and white representation is possible with real devices. To realize good black and white representation under the operating condition, it is necessary to determine the film characteristics so that black representation is possible for the liquid crystal cells in the off mode with a bias voltage applied. Hence, the following method is used for optimization.(1) Before the color compensation films are optimized, the applied voltages for the ON and OFF states are determined such that the transmission at the ON state is maximum for optimized films based on the measured results of the elliptic polarization after the transmission through the polarizer/liquid crystal.(2) For the liquid‐crystal cell for which the determined OFF voltage is applied, the film characteristics are optimized so that black representation is realized. In the usual optimization method, the results of the numerical calculations are used as the characteristics of the liquid crystal cell. The film was optimized for such results.In the present method, the measured results of the elliptic polarization are used as the characteristics of the liquid crystal cell. Hence, the optimization corresponding to the real device can be carried out. A device was fabricated by the present optimization method. It was confirmed that good black and white optimization corresponding to real devices can be realized with a high transmission and a good color characteristic at the operating condition.
Finite element analysis of electromagnetic field via three‐dimensional hexagonal edge elements
Authors: Yamabuchi Tatsuo , Fujii Shigeo , Murai Tadakuni , Hirose Sadaki , Futagami Tooru , Kagawa Yukio 
Published: July 2007

AbstractFor analyses of problems of three‐dimensional electromagnetic fields by methods of finite elements, formulation based on hexagonal edge elements was used which also was applicable to bodies of arbitrary shape. In previous formulation, a combination of tetrahedral elements was used to construct hexagonal edge elements.This paper proposes the use of vectorial shape functions in constructing hexagonal edge elements. Their shape functions agreed with the Nedelec‐type elements when a hexagonal body was reduced to a rectangular solid. However, spurious solutions were generated when the body shape deviated from the rectangular solid. Therefore, it is necessary to incorporate Lagrange multipliers as new unknowns in applying elements obtained by the authors to a general three‐dimensional body model. The final discretized equation becomes a simultaneous equation and is not solved by an eigenvalue problem.As a general model, a circular cylindrical cavity was treated and the resonant frequencies and excitation responses were obtained. For the resonant frequencies, the results obtained herein are compared with those by using the Nedelec‐type tetrahedral elements.
Scattering of electromagnetic plane waves by a chiral slab
Authors: Tanaka Mitsuru , Sueyoshi Hidetomo 
Published: July 2007

AbstractThe scattering characteristics are studied for the plane wave incidence with an arbitrary polarization onto a chiral slab placed on a conducting medium. The analysis is carried out with recognition that the electromagnetic field inside the chiral medium is expressed as a superposition of the right and left circularly polarized waves with different phase velocities.By using the electric field components of the incident wave, the equations for the reflected field and the transmitted field are derived. The polarization ratio and the Stokes parameters characterizing the polarization states of these fields are provided. For the cases of the incident wave with the horizontal and vertical polarizations, the cross‐ and co‐polarized components of the reflected power and the Stokes parameters of the reflected wave are computed numerically.The effects of the chirality admittance, the thickness of the slab and the complex permittivity of the conducting medium on the polarization conversion characteristics of the reflected wave are presented. It is considered that the terrestrial vegetation layers exhibit characteristics similar to those of the chiral materials. The results obtained in this paper are believed useful for the analysis of the remote sensing data for vegetation layers.
Equivalent network approach for electron wave propagation and its applications
Authors: Kaji Ryosaku , Hayata Kazuya , Koshiba Masanori 
Published: July 2007

AbstractWith a view to exploring the analysis and design method which provides a good engineering perspective for electron wave devices using the quantum effect phenomena, the electron wave propagation is formulated from a circuit theory viewpoint. In this paper, the electron wave obliquely incident on the heterointerface is treated. First, the quantum mechanical quantities are transformed to the electromagnetic quantities. Then the transmission line equation and the equivalent circuit for the electron wave propagation are derived.Next, the problem of propagation of the electron wave obliquely incident on the heterointerface is studied in detail by means of its equivalent circuit. The reflection and transmission coefficients and the reflection and transmission probabilities are then calculated. At the same time, the conditions for existence of the Brewster angle and the critical angle for the total reflection are described. Evaluation of the Goos‐Hänchen shift is also carried out. Further, it is shown that the eigenvalue equation for the guided mode in the electron waveguide can easily be derived by the application of the transverse resonance condition well known in circuit theory. The problem of propagation of the electron waves normally incident on the heterointerface such as in the quantum well and the potential barrier are contained in the present formulation as a special case.
A shielded gate static induction transistor: Its characteristics and design
Authors: Yano Koji , Kimura Masakazu , Tanaka Akira , Sukegawa Tokuzo , Kim Chang‐Woo , Motoyama Shin‐Ichi 
Published: July 2007

AbstractA static induction transistor (SIT) in which the p+ gate region is shielded by a thin n layer, called a “shielded gate SIT,” is proposed. The results of a two‐dimensional simulation revealed that introduction of the shielded gate structure into SITs with a sufficiently high‐purity channel comparable with intrinsic material can successfully improve on‐resistance as well as supporting relatively large blocking gain when this structure is appropriately designed by the complete space charge approximation. In particular, the effect of this structure increases with increased gate spacing. A design method for high‐frequency improvement is also discussed.
Electron beam direct lithography system using the SEM
Authors: Hasegawa Akihiro , Kang Ryo‐Il , Shono Katsufusa 
Published: July 2007

AbstractA scanning electron microscope (SEM) was utilized for electron beam direct lithography. The scanning electron microscope was modified by installing a blanking unit, thus modifying the deflection coil and condenser coil and adding an external signal line for secondary electron beam detection.Without modifying the microscope tube and the internal circuit of the SEM, lithography of a layout pattern was made possible. By implementing a lithography system on a Bitmap‐IV CAD system designed for layout pattern designing, both circuit design and lithography were carried out.The designed layout pattern data were translated to the lithography data described by electron beam direct lithography language (EBDL). Using the algorithm taking into account the characteristic of electron beams in SEM, the minimum pattern dimension of 4 μm with an alignment tolerance of ±2 μm on a chip area of 3.2 mm × 3.2 mm was achieved in patterning circuits in CMOS. LSIs and micromachine layouts. The system was totally automated in operations including positioning.
Static‐noise margin analysis for a scaled‐down CMOS memory cell
Authors: Douseki Takakuni , Mutoh Shin‐Ichiro 
Published: July 2007

AbstractThe noise margins for CMOS SRAM cells composed of scaled‐down MOSFETs are described.First, an analytical method estimating the noise margins for the CMOS memory cells is proposed. Then scaled‐down MOSFET effects, i.e., the mobility degradation and the parasitic resistances will be considered. How each of these effects changes the noise margins will be studied using analytical equations. As a result, it will be determined that the mobility degradation worsens the read margin by considerably reducing the CMOS inverter logic threshold voltage. It will also be determined that the parasitic resistances associated with the drive transistors degrade the read margin.Finally, equations are derived for the threshold voltage and cell ratio for a given noise margin. Its effectiveness will be demonstrated for 0.2 μm CMOS memory cells.
Downscaling of floating‐gate EEPROM modules for ASIC applications
Authors: Shiba Kazuyoshi , Kubota Katsuhiko 
Published: July 2007

AbstractDownscaling methods of electrically erasable programmable ROM (EEPROM) for application‐specific integrated circuit (ASIC) applications based on the double‐poly floating‐gate process were studied. Simple scaling of ASIC and EEPROM modules with the same scaling factor can significantly reduce the time for design and development.Horizontal scaling of the memory cell with unchanged vertical dimensions does not alter the cell performance because the capacitance coupling ratios are kept constant. Vertical scaling, which further reduces the cell size due to less short channel effects, requires the improvement in the tunnel oxide quality. For this purpose, an improved process also was studied in terms of process temperature and phosphorus concentration in polysilicon gate.
A 256‐K Bi‐CMOS ECL self‐timed RAM using merged Bi‐nMOS gates
Authors: Ohbayashi Shigeki , Shiomi Toru , Sumi Tadashi , Suzuki Kimio , Ohba Atsushi , Honda Hiroki , Ishigaki Yoshiyuki , Hine Shiro , Anami Kenji 
Published: July 2007

AbstractA 64 K × 4 Bi‐CMOS ECL self‐timed RAM was developed. It is a register‐register type memory and incorporates register circuitry for input and output buffers. It employs an ECL interface for accommodating high‐speed systems. The input and output ECL registers minimize the set‐up and hold times and the clock access time. Reduction in the cycle time was achieved by adopting a fast, small Bi‐nMOS word driver including a merged bipolar‐pMOS device and by dividing the read data bus into two halves with a main sense amp, which operates as a current‐to‐voltage converter. A hierarchical reference voltage generator was introduced to realize a reliable operation by suppressing a variation in threshold voltages of the ECL input buffers due to wire resistances through the reference voltage wire inside the chip. The cycle time of 5 ns and the clock access time of 2 ns were obtained by the circuit techniques described in the foregoing, implemented on a 0.8‐μm Bi‐CMOS process with three layers of polysilicon and two layers of metal.
Process technologies for three‐dimensional optoelectronic integrated circuits
Authors: Katayama Yoshifumi 
Published: July 2007

AbstractThe fundamental research on process technologies for three‐dimensional optoelectronic integrated circuits (OEIC) conducted at Optoelectronics Technology Research Laboratory (OTL) is reviewed. These process technologies consist of atomically controlled epitaxy and the in situ pattern formation of III—V semiconductors.For atomically controlled epitaxy, various surface analysis techniques are utilized in combination with molecular beam epitaxy (MBE). The in situ pattern formation is performed using a thin oxidized layer of GaAs in an ultrahigh vacuum (UHV) multichamber system. This patterning is based on the in situ electron‐beam (EB) induced C12 etching of the photooxidized GaAs layer.On the basis of the foregoing result, the process technologies for the future three‐dimensional OEIC are discussed.
Optimized design of stepped impedance dielectric coaxial resonators via tm mode analysis
Authors: Toki Masahiro , Arai Hiroyuki , Makimoto Mitsuo 
Published: July 2007

AbstractThe analysis of resonant electrical length and unloaded Q for the miniaturized dielectric coaxial stepped impedance resonator (SIR), used often in diplexers of portable radio telephones, is performed usually with the assumption of only fundamental TEM mode.In this paper, finite element TM mode analysis is performed and optimum structure design of SIR is shown which makes the ratio of unloaded Q to the resonant electrical length kL (Q/kL) maximum. As a result of analysis, it is found that the location of the step to minimize resonant electrical length is about 40 percent of the axial length from the open end of SIR.The ratio of unloaded Q and resonant electrical length varies rather slowly when any of the structure parameters are varied around the optimum value. This fact shows that no high precision in the design of structure parameters is required. Moreover, providing taper at the step position in SIR, the resonant electrical length can be increased by a few percent.It is shown also that the present analysis is useful for the design of square‐shaped SIR which is a simple and practically used structure for diplexers.