bluuebunny/crossref_metadata_2025_split huggingface dataset:
Device analysis of two‐dimensional electron gas (2DEG)FET
Authors: Usagawa Toshiyuki , Araki Nobuko Mishima 
Published: July 2007

AbstractA one‐dimensional analytical model of 2DEG‐FETs has been developed in which the effect of the source‐gate resistance Rsq and velocity saturation are included. When the electron mobility μ, the electron drift peak velocity Ve, the source‐gate resistance Rsg and the AlGaAs film thickness d are varied, the corresponding transconductance gm and the conductance coefficient K are numerically studied in detail. With the present model, the device characteristics of the “MIS”‐like 2DEG‐FET with a thick n+‐GaAs cap layer and an undoped AlGaAs gate have been analyzed. From the point of application of 2DEG‐FETs to a high speed LSI, the design guideline of the device has been studied. For the device parameters of the gate length Lg = 0.2 μm, the transistor width W = 10 μm, Rsg = 15 Ω, d = 22 mm, μ = 8000 cm2/Vs and Ve = 2 × 107 cm/s, the expected device characteristics are K = 10.0 mA/V2, the sourcegate capacitance Cgs = 10.0 fF, gm = 700 mS/mm and fT = 110 GHz.
Systematic design approach for AlGaAs/GaAs HBT using two‐dimensional device simulator and circuit simulator
Authors: Honjo Kazuhiko , Madihian Mohammad , Kumashiro Shigetaka 
Published: July 2007

AbstractA systematic design method for HBT's is described which is based on a two‐dimensional device simulator and a circuit simulator. The validity of this method has been studied by applying it to an AlGaAs/GaAs HBT with a base electrode sandwiched by two emitter electrodes. This structure has a performance better than that of a conventional structure. It is found that the designed values agree well with the measured results for hFE, CBE, CBC and fT. It is shown that the design accuracy of fT and CBE can be improved if the hot electron effect is introduced in the device simulator. A large signal modeling method is proposed by the circuit simulator SPICE‐F' which is modified so that the collector‐emitter offset voltage characteristic to the HBT can be expressed. By way of this new method, the bias dependence of equivalent circuit parameters of the HBT, such as fmax, fT, CBE and CBC, can be computed with good correlation with the experimental data.
Coherent backscatter‐induced noise in optical fiber gyroscopes with serrodyne modulation
Authors: Suzuki Yoichi , Yamashita Eikichi 
Published: July 2007

AbstractCoherent backscattered light produces considerable noise in optical fiber gyroscopes. The noise in serrodyne‐modulated optical‐fiber gyroscopes with a low‐coherence source is studied theoretically for various forms of serrodyne‐modulation functions. The noise in output signals from the lock‐in amplifier is analyzed for the closed‐loop gyroscope. The coherent backscatter‐induced noise against the maximum phase of serrodyne‐modulation is estimated for finite flyback time or exponential ramp. It is found that the ideal serrodyne‐modulation function with the maximum phase of π and without flyback time cancels the noise in the signals of these gyroscopes.
A design theory of mode transducers utilizing coupling effects of multimode coupling system and its application
Authors: Sawa Shinnosuke 
Published: July 2007

AbstractThis paper considers the case where a mode transducer consisting of a multimode coupling system exists between the input and output waveguides. The former has no coupling and the latter consists of another multimode coupling system. A design theory is proposed for the mode transducer. That is, the condition is clarified for the complete power transfer from any one of the normal modes of the input waveguide to that of the outgoing waveguide, the so‐called “complete coupling condition.” As a typical example of optical circuits, we apply the present theory to the circular bend, the taper and the branch of optical waveguides, and derive the low‐loss comprising conditions, respectively. As a result, we prove that the present theory includes as a special case the low‐loss design methods proposed so far for the circular bend and taper. Further, we propose a new comprising method of the branching waveguide based on the new design theory. Numerical calculations of the mode conversion properties show that the new branching waveguide not only possesses a simpler structure, but can also achieve lower loss characteristics than the previous one.
Propagation of boundary acoustic waves along a ZnO layer between two materials
Authors: Irino Toshio , Shirosaki Yoshimasa , Shimizu Yasutaka 
Published: July 2007

AbstractThis paper describes the theoretical and experimental results on the propagation of boundary acoustic waves along a ZnO layer between two materials. It was proven theoretically that the boundary acoustic waves propagate in SiO2/ZnO/SiO2, SiO2/ZnO/PYREX and SiO2/ZnO/(Z – X)Si structures. The propagation velocity, electromechanical coupling coefficient K2, and the concentration of energy to the mid‐layer were calculated as a function of the ZnO film thickness. The thermal coefficient of delay time TCD was also calculated for the SiO2/ZnO/SiO2 and SiO2/ZnO/(Z – X)Si structures, showing that a certain ZnO film thickness provides zero TCD. Next, requirements of a glass substrate for propagation of boundary acoustic waves along the ZnO film sandwiched by SiO2 and glass substrate or glass film and glass substrate is discussed. As a result, as the thickness of the ZnO film and the second velocity increase, the boundary acoustic wave has a better chance to exist. Finally, the device with SiO2/ZnO/SiO2 structure was actually fabricated and it was confirmed that the boundary acoustic wave was excited and propagated in the device. If the Rayleigh wave characteristic is taken into account, the experimental and theoretical results agree.
Radiation effects in SiO2/Si structures
Authors: Watanabe Kikuo , Kato Masataka , Nagata Minoru , Okabe Takahiro 
Published: July 2007

AbstractRadiation effects in SiO2/Si structures are studied by capacitance‐voltage characteristics of MOS diodes. As a radiation, X‐ray is used mainly because it can be shielded easier than γ‐ray from Co 60. Although the two radiations have different photon energy, it is found that they cause the same effects in device characteristics. Therefore, X‐ray is thought to be suitable for irradiation tests of devices. Both the positive fixed charge in the SiO2 film and the SiO2/Si interface states caused by X‐ray irradiation are strongly dependent on the polarity of a bias voltage applied to a metal gate of an MOS diode during irradiation. When the polarity is positive, the radiation effects are several times stronger than those when the polarity is negative. These results are considered to indicate that both the positive fixed charges and the interface states are not generated directly by X‐ray photons, but generated by mobile positive charges created in the SiO2 film due to the irradiation. In addition, dependence of the radiation effects on device fabrication processes is studied. For example, it is found that when thermal oxidation is carried out in ambient‐containing impurities such as chlorine and nitrogen, the radiation effects in the SiO2/Si structures become more severe. These results indicate that the suitable selection of device fabrication processes will lead to a better radiation hardness of the device.
Simulation analysis of semiconductor laser operation
Authors: Kume Masahiro , Takeshima Masumi , Shimizu Hirokazu , Sugino Takashi , Itoh Kunio , Kano Gota 
Published: July 2007

AbstractUse of the best‐designed structure parameters obtained from a simulation analysis is an efficient means to develop semiconductor lasers. From this viewpoint we have developed a simulation program which is of practical use. The characteristic aspect of the program is to find physical parameters mainly from theoretical calculations without recourse to experimental data, and to take into account the Auger recombination and the intervalence‐band absorption. This makes the program useful for arbitrary materials. To attain high‐speed simulation, we have used some simplifying models for calculations which would otherwise be complicated inherently in the inner stripe geometry. It is found that despite various simplifications, calculated results offer a satisfactory quantitative description of experimental results on laser operations in GaAlAs lasers such as the threshold current and the differential quantum efficiency.
Technique for determining the refractive indices and oscillator strengths with the angle phase‐matching conditions in optical four‐wave sum‐mixing
Authors: Koyanagi Kojiro , Mishima Teruhito , Sakuraba Ichiro 
Published: July 2007

AbstractA new method is proposed for measurement of the index of refraction of gas and oscillator strength. In four‐wave sum‐mixing in such nonlinear media as metal vapor or rare gas using the third‐order nonlinear optical effect, the refractive index of a nonlinear medium at the sum frequency in the vacuum ultraviolet range is found from the angle phase‐matching condition for the maximum conversion efficiency, and the oscillator strength is determined from the measurement of refractive index by the phase matching in terms of the sum frequency. The present method in which the refractive index and the oscillator strength are determined from the incident angle of each wave satisfying the angle phase‐matching has the advantage of fewer measurement parameters compared to the conventional methods in which a phase‐matching is accomplished with a mixture of gases with ordinary and extraordinary dispersions. This is because no buffer gas is mixed. In addition, the measurement accuracy is found theoretically to improve in the region with a higher atomic density.
Fabrication and characteristics of GalnAsP/InP surface‐emitting laser with circular buried heterostructure
Authors: Yamakawa Hideaki , Watanabe Isao , Uchiyama Seiji , Koyama Fumio , Iga Kenichi 
Published: July 2007

AbstractIn a GaInAsP/InP surface‐emitting laser, there is no current‐confining structure, resulting in the current spreading and a restriction in the electrode area causing a high ohmic resistance. These problems cause a high threshold current and obstruct a laser operation at room temperature. In this study, to effectively inject current into the active region, the buried‐heterostructure with a reverse biased p‐n junction layer is introduced. At the same time, the diameter of the active region is reduced to 15 μm. The threshold current of this laser at 77°K is as low as 19 mA.
Technology of cable transfer system for error‐free digital transmission
Authors: Komatsu Naohisa , Tsuchiya Yuzo 
Published: July 2007

AbstractAt present the transfer or exchange of subscriber cable in the telecommunication network is performed by temporarily cutting off the circuit with the customer's consent. For a communication circuit requiring 24‐hr real‐time service, such as data transmission, however, a cable transfer method must be developed which can handle a live circuit and prevent an error in the information during transmission. From such a viewpoint, this paper considers the cable transfer technique which improves the traditional cable transfer process, and presents the design condition in relation to the transmission quality of the communication circuit. First, a cable transfer method is proposed which can be applied to a live circuit without affecting the telecommunication, such as the interruption or the noise due to transfer. In this method, resistors are inserted into existing and new circuits at two working points for the cable transfer, and the resistances are varied in a pair. The method can be applied to the code transmission circuit in ISDN, in the cable transfer for the subscriber line. Second, an identification method is proposed, which can be applied to the unbalanced circuit, such as the security alarm circuit. The method utilizes the transmission signal at each working point, and compares the measured values. The idea can be applied to the general balanced lines to identify the line with a high speed.
Influence of low‐frequency‐spectrum elimination on reproduced waveforms in MFM and ZM coding methods
Authors: Tanaka Hideo 
Published: July 2007

AbstractOne method to improve the signal‐to‐noise ratio in a magnetic recording is to use a filter to narrow the frequency bandwidth. This paper presents a theoretical analysis of the influence of a low‐frequency spectrum on reproduced waveforms in the MFM and ZM coding methods, together with the evaluation of possible narrowing of the bandwidth. In this method, a reproduced waveform is constructed by superimposing solitary waveforms according to the code‐words of the MFM or ZM modulation methods. Then low‐frequency spectra were eliminated from the Fourier spectrum of the reproduced waveform, and another waveform is obtained by reconstructing the remaining spectra.The results show the waveform distortions, a change of the amplitude, and peak‐shifts. These are all due to the elimination of low‐frequency spectra. The influance on the design parameters of a disk‐head system (e.g., the length of a gap in its film) was found.
Switched‐capacitor sequential‐flash data converters
Authors: Watanabe Kenzo , Matsumoto Hiroki 
Published: July 2007

AbstractSequential‐flash data converters using switched‐capacitor circuits are developed for realizing a given conversion speed with a minimum number of components. Repeating n‐bit flash conversion m times, each converter accomplishes (m x n)‐bit digital‐to‐analog or analog‐to‐digital conversion in m cycles of a clock frequency. An accurate conversion is also possible because each converter is configured such that the offset voltages of op‐amps and parasitic capacitances have no effect on the conversion process. Error analysis shows that a conversion accuracy higher than 8 bits can be expected from each converter if integrated using present MOS technologies. Prototype converters built using discrete components are also given to confirm the principles of operation.
Design of microwave combiner with waveguide ports
Authors: Matsumura Hajime , Mizuno Haruhiko 
Published: July 2007

AbstractA microwave power combiner with waveguide ports is proposed and its design method is described. It can combine a large number of inputs at the same time and its voltage tolerance is high. On the side wall of a circular TM0m0 (m = 2, 3, 4,…) mode resonator, rectangular waveguides are connected as the input terminal while a circular waveguide is connected at the bottom surface of the resonator as the output port. The output is transformed into a rectangular waveguide via a TM‐TE mode transformer.Slits on the side of the output circular waveguide prevent propagation of the modes that do not contribute to the power combining. In the design method, the Y parameters are computed from the equivalent circuit seen from the output side. Thus, the matching condition is obtained from the image parameters. Actual dimensions of the iris for adjustment of the coupling between the input and output waveguides and the resonator can be found from this procedure. The insertion loss of a 14‐GHz four‐way combiner with a TM020 mode resonator was 0.25 dB.
Influence of DC bias on nonlinear distortion of contacts
Authors: Minowa Isao 
Published: July 2007

AbstractWhen the nonlinear distortion generated at the metal contact is measured by the two‐frequency method, spectroscopic measured results ranging from the second‐ to sixth‐order distortions can be obtained. Depending on the type of contact and the contact condition, the characteristics of these distortion spectra are different. It was reported previously, together with the measurement technique, that this measurement can be used as a measure for finding the physical phenomena on the contact surface. In the present study, the second‐ and third‐order distortions are considered to be representatives of the even‐ and odd‐order distortions for the purpose of finding the cause of the distortion. A dc bias is applied to the contact and the bias dependence of the distortion voltage is studied. As a result, it is found in most contacts that the second‐order distortion voltage is affected strongly and becomes a minimum at a certain bias point. This indicates that at this bias point the diode characteristics which are the cause of the even‐order distortion vanish and the nonlinearity is almost perfectly symmetric for the currents in both directions. Especially, in this measurement, the bias dependence is observed even if glossy metals are contacted. Hence, this is a method for finding the surface phenomena for a thin‐film thickness from the electrical characteristics.
Photocoupler systems using laser diode
Authors: Matsushita Kenji , Shimizu Eiji , Kitamura Hiroaki 
Published: July 2007

AbstractDue to recent progress in semiconductor lasers, small‐sized optical sources with good coherency characteristics are easily obtainable. Using semiconductor lasers instead of previously employed light‐emitting diodes, it is believed that construction of new photocoupler systems is possible. In this paper, using the coherent light, the basic behavior of photocouplers is discussed and parallel and serial photocoupler systems with new functions are proposed.
Bidirectional characteristics and applications of temperature‐sensitive magnetic semiconductor
Authors: Seki Kyoshiro , Osada Hiroshi , Shida Jun‐Ichi , Murakami Koichi 
Published: July 2007

AbstractThe magnetic and conduction properties of certain ferrites (referred to as temperature‐sensitive magnetic semiconductors (TMS)) exhibit marked temperature dependence. The temperature dependence of the resistance of a TMS is similar to that of a semiconductor thermistor at low voltage. At higher voltages, three regions are observed in the symmetric, bidirectional characteristics. These are a cutoff state, a negative resistance state and an “on” state.Therefore, a TMS can act as a multifunction magnetic semiconductor device which can be used to satisfy thermistor and bidirectional diode characteristics. Application of TMS diodes for their ability to handle overvoltage and overheating is discussed.
Principles for modal waves in guided wave optics
Authors: Hashimoto Masahiro 
Published: July 2007

AbstractThe geometrical optics theory of modal waves propagating along optical waveguides is described. The theory is general and thus applicable to the general classes of inhomogeneous waveguides including aniso‐tropic media. This paper points out that the light ray, which is the fundamental concept in geometrical optics, is to be definable as the energy ray and the wave‐normal ray. The variational principles valid for these two definitions are explained. The energy ray is the well‐known ray that shows the path of energy transport. The wave‐normal ray is defined to be the locus of the wave‐normal vectors perpendicular to the wavefronts. The variational principles that describe these two rays are different, and therefore the ray equations for both rays are different in anisotropic media. The former is known as Hamiltonian optics, but the latter is not yet established as geometrical optics. It is pointed out that the latter should be used to describe the geometrical behaviors of guided modes and the propagation of modal waves without any logical contradiction. Optics describing guided modes in terms of the wave‐normal rays is called guided wave optics, and some differences from Hamiltonian optics are discussed using several examples.
Fabrication of polycrystalline silicon thin‐film transistors by ion shower doping technique
Authors: Hirano Ryuuma , Setsune Kentaro , Yoshida Akihisa , Hirao Takashi 
Published: July 2007

AbstractIn the fabrications of polycrystalline silicon thin‐film transistors (TFTs), doping of impurities is often carried out by ion implantation. In this study, dopings of phosphorus and boron were carried out by an ion shower doping technique, where the rf plasma of H2‐diluted PH3 or H2‐diluted B2H6 gas with a magnetic field was used for the ion source. To form the source‐drain regions using this technique, the doping characteristics such as sheet resistivity and impurity profiles in polycrystalline Si were investigated. Using the conditions obtained experimentally, n and p channel Si gate polycrystalline Si TFTs were fabricated on a fused silica substrate by using a CMOS process. It was also confirmed that the conventional photoresist can be used for this process. For the n‐channel transistor, field‐effect mobility μ = 3 cm2/V·s, threshold voltage Vth = 5 V, and on‐off current ratio ION (VD = 6 V, VG = 10 V)/IOFF (VD = 6 V, VG = 0 V) ≌ 106 were obtained for W/L = 12 μm/6 μm. In the p‐channel transistor, the characteristics were similar to those obtained by ion implantation. The ion shower doping technique made it possible to fabricate polycrystalline Si TFTs with a CMOS structure, using a simple apparatus. By using this technique, a large area process will be possible.
Finite‐element analysis of plane wave diffraction from metallic gratings with arbitrary complex permittivity
Authors: Nakata Yasunori , Koshiba Masanori 
Published: July 2007

AbstractA method of analysis based on the finite‐element method is presented for the problem of plane wave diffraction from metallic gratings with arbitrary complex permittivity. First, the problem of diffraction of a plane wave from the metallic reflected‐type grating is analyzed rigorously as a two‐media boundary value problem by the finite‐element method. Next, a new method is proposed in which an approximate boundary condition using the surface impedance is incorporated into the discretized equations by the finite‐element method. Especially, in the method of using the surface impedance approximation, the region to be analyzed is reduced substantially from the one for the two‐media boundary value problem, and the computational effort is expected to be reduced significantly. The diffraction characteristics of grooved gratings with sinusoidal, triangular and rectangular profiles are actually calculated and the results are compared with those by other methods and experiments. In the case of the TE wave incidence, it is found that the results by the two‐media boundary value problem and those by the surface impedance approximation agree well. On the other hand, in the case of the TM wave incidence, the results are substantially different depending on the grating profile. By comparison of the results with those based on the assumption of a perfect conductor, it is found that the loss in the metal must be considered at a longer wavelength in the case of the TM wave incidence than in the case of the TE wave incidence.
Document image compressing and expanding LSI processor
Authors: Nakamura Koozoo , Kojima Yasuyuki , Hamada Nagaharu , Suemori Noboru 
Published: July 2007

AbstractA single‐chip LSI processor (FCP: Facsimile Codec Processor) is developed which executes the encoding and decoding of binary images using the MH and MR codes. The developed FCP has the following special features: (1) high‐speed changing pixels detection and decoded pixels generation by means of processing 16‐bit pixels in parallel using a 16‐bit video bus operated independently of the MPU bus; (2) use of 2‐μm CMOS technology with about 64,000 transistors; (3) encoding or decoding an A4 size document (standard letter size) in approximately one second.