bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of GaAs regrowth interfaces grown by metal‐organic vapor phase epitaxy
Authors: Ikeda Eiji , Hasegawa Hideki , Ohno Hideo 
Published: July 2007

AbstractIf epitaxial growth is interrupted to incorporate processes followed by epitaxial regrowth, the degree of freedom in device designing increases. This paper characterizes the GaAs epitaxial regrowth interface grown by metal‐organic vapor phase epitaxy (MOVPE).Three basic regrowth processes were evaluated by C‐V carrier profiling, DLTS analysis and I‐V measurements, and the following results have been obtained:

(1) when regrowth is carried out after growth is interrupted in the furnace, carrier accumulation at the interface is observed. This is due to the transitional change of the V/III ratio and can be eliminated by proper control of the gas flow;
(2) when regrowth occurs after exposure to air for a long period of time, carrier depletion/accumulation or carrier accumulation alone is observed. This can be explained by a formation of interface energy levels which are energy‐wise continuous. The cause of the interface energy levels can be explained by our model DIGS (disorder induced gap state);
(3) when regrowth is carried out after the sample is soaked in acetone, a depletion profile due to carbon adsorption is observed.
InP LD with PD fabricated by Br2–reactive—ion–etching technique
Authors: Tsujii Hiraaki , Ohnaka Kiyoshi , Shibata Jun 
Published: July 2007

AbstractIt is important to monitor the optical output of a laser diode (LD) in an opto‐electric integrated circuit (OEIC). Therefore, in monolithic fabrication of an LD with a photodetector (PD), chlorine (Cl)‐based gas has been used to carry out dry etching for forming a laser facet in InP‐based materials. However, in this technique, selectivity of etching is not sufficient. In our study, Br2 was employed as the etching gas using Ti for the etching mask. Our technique can provide a selectivity of etching as high as 34 and has been found to be effective in forming a laser facet.Using reactive ion etching (RIE) with Br2 gas, a laser facet was formed in a buried heterostructure laser diode (BHLD) with a PD. The threshold current and optical output of the LD were 35 ‐ 50 mA and 5 ‐ 10 mW, respectively, while the sensitivity of the PD was 0.49 A/W. The isolation resistance between the LD and PD was 1 Mω.The result of this study indicates that our technique will be effective in high‐density integration of OEICs.
An integrated AlGaAs two—beam laser diode—photodiode array fabricated with reactive ion beam etching
Authors: Uchida Mamoru , Asakawa Kiyoshi , Matsumoto Shohei , Kawano Hideo 
Published: July 2007

AbstractAn integrated A1GaAs two‐beam laser diode‐photodiode array for optical disk applications was fabricated monolithically by the reactive ion beam etching technique. The laser cavity was formed by etched and cleaved facets. The threshold current and the external differential quantum efficiency are 18 mA and 28 percent, respectively. These parameters are as good as those of a laser with two cleaved facets. The detection efficiency of the photodetector (PD) was as high as 32.5 percent. The crosstalk due to the neighboring laser diode (LD) was minimized by forming an optical barrier between two PD and LD pairs. The cross‐talk was as low as −20 dB. In the dual cavity‐type laser using the light receiving surface of PD as the external mirror, the optical noise was lower than that in the laser without the external mirror.
Approach to high—speed operation of InGaAs/InP monolithic PIN/Amplifier
Authors: Matsuda Kenichi , Kubo Minoru , Ogura Mototsugu , Shibata Jun 
Published: July 2007

AbstractWe have been developing InGaAs/InP monolithic PIN/Amplifiers. This paper describes the consideration to use self‐aligned FETs with a view to improving the operating speed. To this end, the device structure and the fabrication process have first been discussed for integrating the self‐aligned JFETs and photodiodes. Next, photodiodes and FETs of this configuration have been fabricated and their characteristics evaluated. It was found that the dark current of the photodiode could be reduced to 2.7 nA at −3 V and that the cutoff frequency of the FET was improved to be 3.0 GHz. Finally, a monolithic PIN/Amplifier was fabricated. Presently, the frequency characteristics of fabricated PIN/Amplifiers are not so good. This is believed to be caused by the fact that the gate electrode of the FET is a Schottky electrode. If this problem is settled in the future, a PIN/Amplifier with a 3‐dB bandwidth of about 700 MHz can be realized.
Diffused ion concentration profiles of ion—exchanged glass optical—waveguides
Authors: Tsutsumi Kiyoshi , Mizushima Tetsuya , Hirai Hiroshi , Yuba Yoshiharu 
Published: July 2007

AbstractBased on diffusion theory and results obtained by using an X‐ray microanalyzer (EPMA), the concentration profile of diffused ions in an ion‐exchanged optical waveguide was investigated. To clarify the features of the concentration profile, the concentration dependence of the diffusion coefficient was discussed. In the EPMA measurement, angle‐lapped samples were used to achieve a high resolution. First, the dependences of the diffused‐ion concentration profile on the exchange time and temperature was investigated by using diffusion theory. Then the concentration dependence of the diffusion coefficient was presented by using the calculated diffusion coefficients for some concentration profiles. Next, potassium concentration profiles were measured with an EPMA, using angle‐lapped K+ ion‐exchanged soda‐lime glass waveguides. By expressing measured concentration profiles using the normalized depth of η = x/2√τ (x: depth, τ: exchange time), it was found that the concentration profiles were much the same, regardless of the exchange time. Furthermore, by comparing the concentration dependence of the diffusion coefficient evaluated from the concentration profile, it was found that, in general, the profile was close to the Gaussian and that near the surface or in the case of zero concentration, the profile was close to a quadratic function. The concentration profile was similar to the refractive index profile obtained by the inverse WKB method.
Preparation and magnetic properties of anodic oxide magnetic films
Authors: Arai Ken Ichi , Ohoka Yohsuke , Wakui Yukio 
Published: July 2007

AbstractThe M‐H curve, coercive force and magnetic anisotropy of magnetic anodic oxide films containing electro‐deposited iron particles in pores were measured for the various pore diameters between 150 and 1200 Å, packing densities between 0.13 ‐ 0.48 and film thicknesses between 0.08 and 1.3 μm. As a result, it was found that the coercive force perpendicular to the film surface depends only on the pore diameter when the length of the iron particle is 15 times larger than its diameter, and that it decreases in inverse proportion to the square of the pore diameter when the pore diameter is larger than 350 Å. This indicates that the mechanism of magnetization reversal in these films follows the curling mode. The coercive force parallel to the film surface is affected by the shape of the initially deposited iron particles. The magnetic anisotropy depends strongly on the packing density of the iron particles. When the packing density is less than 0.32, the direction perpendicular to the film surface is the direction of easy magnetization. When the packing density is higher than 0.32, the direction parallel to the film surface is the direction of easy magnetization.
Analysis of reflective SAW gratings for SH‐type modes using finite‐element method
Authors: Hasegawa Koji , Koshiba Masanori 
Published: July 2007

AbstractA solution based on the finite‐element method (FEM) is presented for the analysis of SH‐type surface acoustic wave gratings. Although the FEM has already been applied to the discontinuities in elastic waveguides for SH‐type modes, only the isotropic substrate has been treated. Also, it is difficult to apply the FEM directly to many discontinuities such as grating reflectors due to excessive computation time and computer memory requirements.This paper presents a numerical approach to the analysis of SH‐type surface acoustic wave gratings on anisotropic substrates. To apply the FEM directly to many discontinuities, the substructure method is introduced. As a result, mutual interaction between surface waves and bulk waves is automatically taken into account over the entire discontinuity region. To show the validity and usefulness of this approach, examples are computed for various gratings on PZT‐4, 41° Y‐X LiNbO3, and 36° Y‐X LiTaO3 substrates.
Estimation of acoustic wave radiation from an IDT by use of effective permittivity
Authors: Hashimoto Ken‐Ya , Yamaguchi Masatsune 
Published: July 2007

AbstractBy means of approximate charge distribution on an interdigital transducer (IDT), it is shown that not only the electromechanical coupling coefficient k2 and the radiation conductance for the surface acoustic wave (SAW), but also the radiation conductance due to the radiation of a bulk wave from an IDT can be obtained from the effective permittivity in an analytic, though approximate, form. Next, a simple method is proposed in estimating the spurious level of the bulk wave in an SAW device by using the radiation conductances for the SAW and the bulk wave. In general, the spurious level due to the bulk wave often depends on the geometric shape. The maximum value can readily be computed by the present evaluation method. The analysis results agreed well with the experimental data on Li2B4O7 and LiTaO3 used as SAW device substrates. It is also shown that a program for deriving the effective permittivity can be developed by making use of the computer program for the SAW velocity calculations.
Multinozzle drop generator for continuous ink jet printing
Authors: Morita Naoki 
Published: July 2007

AbstractUniform, stable drop generation is the key technology for continuous ink jet printing. Previously, the method to produce the standing wave driven by the high polymer piezoelectric transducer had been utilized for acoustic excitation. However, the characteristics varied from assembly to assembly and were unstable to the environmental changes. As a new alternative approach, the Traveling‐Wave Drop Generator (TWDG) was developed in which the acoustic wave is generated in one end, and then travels to the other end of the jet array. The characteristic results showed that this generator could fully solve the forementioned problems, and it has a simplified structure.
Growth of oxide films on the surface of Cu contact and its effect on the contact resistance property
Authors: Tamai Terutaka 
Published: July 2007

AbstractFrom the viewpoints of contact reliability for small‐sized contact components, growth processes of the oxide film on the Cu contact surface were analyzed by studying the film thickness and formation of films. This analysis of the film was conducted in detail by ellipsometry which scarcely applied to the contact phenomena, in combination with an electrochemical reduction method. Moreover, the effect of the growth of the film on the contact resistance property was studied. As a result, in the oxidation by heating in air, Cu2O film grows mainly at the initial stage of the film growth. As the film grows around 1000 Å, CuO appears on the surface of Cu2O.In this stage, the contact resistance increases sharply and contact failure occurs. Furthermore, it was found that the velocity of growth of the film is slowed which corresponds Co each stage of the oxidation: the initial, the middle, and the latter stage. By application of ellipsometry to the analysis of the contact surface, the measurement of the film thickness together with the possibility of discrimination for the formation of the film by using changes of the optical constants of the film were clarified.
Frequency stabilization of a semiconductor laser under modulation
Authors: Sato Takashi , Koizumi Shungo , Saito Toshinori , Shimba Minoru 
Published: July 2007

AbstractThe laser oscillation frequency of a semiconductor laser becomes unstable under modulation. The stability of the frequency stabilization method using the atomic absorption line is degraded by the oscillation spectrum broadening caused by the sidebands under modulation. Therefore, we designed two methods, the synchronous detection method and the peak‐hold method, to improve the frequency stability under modulation.From the experiment using the Rb absorption line, the synchronous detection method improved the stability by 3 times compared with the old method. The peak‐hold method improved the stability by 10 times compared with the old method under modulation and by 2 times compared with the old method without modulation.
A synthesis of reduced ripple switched‐capacitor current sources and their applications
Authors: Hyogo Akira , Sekine Keitaro 
Published: July 2007

AbstractAlthough the circuit in the conventional switched capacitor (SC) current source (SCCS) is extremely simple, the output current ripple incresaes if the input frequency is reduced. This paper proposes a new reduced ripple SC current source (RRSCCS) in which an integrator circuit is added to the conventional circuit to reduce the ripple. The output current from the proposed circuit can be determined by the voltage, frequency and capacitance as in the conventional circuit. In addition, no current ripple occurs theoretically in the new circuit. As examples of applications, a frequency‐controlled voltage source (FCVS) and a current source proportional to the square of the frequency (F2CCS) are constructed. In the present FCVS, the output voltage can be made proportional to or inversely proportional to the frequency depending on the input frequency and the control frequency. Since the output voltage is determined by the capacitance ratio, frequency ratio and voltage, it is of high precision. Next, it is shown that the present F2CCS is useful for linear control of gm of the MOS‐type OTA. Good results have been obtained by experiments using individual components.
Effects of the cell structure on ZnS:Mn El characteristics
Authors: Abe Yoshio , Fuyama Moriaki , Onisawa Ken'ichi , Ono Yoshimasa A. 
Published: July 2007

AbstractThis paper discusses electroluminescent (EL) characteristics of ZnS : Mn orange‐yellow EL cells. By measuring charage density within the EL cell by means of the Sawyer‐Tower circuit, the dependence of EL characteristics on insulating layer thickness and active layer thickness was determined. Clamp voltage of EL cells estimated from the bend point in the charge density‐voltage characteristic curve was in good agreement with the threshold voltage. It was found that below the clamp voltage, it was possible to treat active layer as an insulator. By decreasing the insulating layer thickness and thus increasing the insulating layer capacitance, we found the following: (1) the voltage of the insulating layer decreased and the clamp voltage decreased; (2) at the same time, the drive voltage margin defined by the difference between the breakdown voltage and the clamp voltage decreased. When the active layer thickness was decreased, the active layer voltage decreased and the insulating layer voltage increased. Furthermore, in the EL cell where the insulating layer capacitance per unit area was 10 nF/cm2, the clamp voltage became smallest when the active layer thickness was taken to be approximately equal to 0.3 μm. Based on these results, an experimental formula was obtained which describes the relation among the clamp voltage, the insulating layer capacitance, and the active layer thickness.
Analysis of soliton pulse propagation in an optical fiber using the finite‐element method
Authors: Eguchi Masashi , Hayata Kazuya , Koshiba Masanori 
Published: July 2007

AbstractSoliton is one of the key concepts that will support future optical communications with a capability for large‐capacity, longdistance transmission systems. In general, the propagation of soliton pulses in an optical fiber is described by the perturbed nonlinear Schrödinger equation (PNLSE). Without any perturbation, this equation is reduced to the canonical nonlinear Schrödinger equation (NLSE) and can be solved analytically. However, in an attempt to take into account a variety of perturbations such as higher‐order dispersion, nonlinear dispersion, shock effect, induced Raman scattering, dissipation, etc., it is no longer solvable in an analytical fashion.This paper proposes a useful method based on the finite‐element method to carry out systematically the evolutional analysis that includes these perturbations. This method can easily deal with cases with realistic perturbations. To confirm the validity of this approach, it is applied to solving unperturbed cases, and it is shown that the same results as those using other solution methods are obtained.
Electrical control of laser beam in viscoelastic polymer thin‐film waveguide
Authors: Muto Shinzo , Takauchi Toshimasa , Murakami Michimasa , Ito Hiroshi 
Published: July 2007

AbstractA thin‐film optical waveguide made of a viscoelastic polymer to which an electric voltage can be applied has been fabricated. Also fabricated is an active thin‐film waveguide device doped with laser dye. Laser light propagation in these devices and the possibilities of electrical control have been studied. It is found that the transmission coefficient of the waveguide and the oscillation wavelength of the thin‐film DFB dye laser can be controlled electrically to a certain extent, although the response is slow.
Uniform asymptotic analysis of guided modes in diffused slab waveguides with polynomial refractive‐index profiles
Authors: Yata Akira , Ikuno Hiroyoshi 
Published: July 2007

AbstractThe propagation constant and the field distribution of the guided modes in a diffused slab waveguide with an inhomogeneous refractive index profile are analyzed by means of the uniform asymptotic series. We used the Airy differential equation as the reference equation to which the Langer transform and the Liouville transform are used repeatedly to construct a uniform asymptotic series solution. If this recursive algorithm is used, an asymptotic solution of an arbitrary approximate degree can be obtained. This uniform asymptotic series solution can be represented analytically by the expansion coefficients of the polynomial approximating the refractive index profile.The propagation characteristics of the guided modes in a diffused waveguide with an index of refraction expressed in terms of an exponential function or an error function are studied and convergence and accuracy of the uniform asymptotic series solution are investigated. The numerical results confirm that the uniform asymptotic series solution agrees well with the rigorous solution or the numerical solution. The propagation characteristics of the guided modes in a diffused waveguide with an exponential refractive index profile have been found with high accuracy. The determination of the propagating modal index is discussed.
An examination of the lateral mode control of the laser diode
Authors: Shirae Hisazumi , Matsuhara Masanori 
Published: July 2007

AbstractTo avoid the high light output power density which has become the problem of the high‐power laser diode, the light power is assumed to be distributed uniformly. However, the disadvantage is that the laser is apt to operate in higher‐order modes in this case. For optical communications use, the laser must operate in a single fundamental mode. This paper aims at obtaining the single fundamental lateral mode, controlling the modes of an index guided semiconductor laser diode together with the investigations of its theoretic results. The finite element method based on Galerkin's method is used for the analysis presented here. In numerical calulations, we take the broad area laser and the array laser as examples for discussions starting from the modal gain. As a result, it is shown that placing high gain in the middle part of the laser diode cross section is effective for the single fundamental lateral mode operation.
Analysis and operating characteristics of micro gas–flow sensor using magnetic fluid
Authors: Oka Hideo , Biringer Paul P. 
Published: July 2007

AbstractPresently, the thermal method and the area method are used in practice for measurement of a gas flow of infinitesimal quantity. However, in terms of output format and the response characteristics, several problems exist. To resolve these problems, we have conceived and fabricated a micro gas‐flow sensor that provides the output in an electrical signal format by means of a magnetic fluid with a fast response and has a simple configuration. This paper presents the analysis of operation and the basic characteristics of the sensor. It is found that the gas flow can be derived as a constant multiple of the product of the period and the maximum amplitude of the output signal of the micro gas‐flow sensor.
Planar‐type photosensor with SiN/a‐Si: H double layers
Authors: Kitagawa Masatoshi , Miyauchi Michihiro , Hirao Takashi 
Published: July 2007

AbstractIt is proposed that an a‐Si:H/SiN double‐layer device is promising which has a thin SiN layer between the planar electrode and a‐Si:H so that the deficiency of the slow optical response is improved while the advantage of a high‐optical sensitivity and the easy fabrication process of the planar photoconductor device are retained. A study was carried out for the amount of PH3 inclusion with respect to SiH4 in the a‐Si:H deposition and the SiN film thickness.By using a double layer of a‐Si:H and SiN, a planar photosensor was realized which has an extinction ratio of more than two orders of magnitude (about 50 dB) and a photocurrent of more than 100 nA with an optical illumination of 150 lx. The optical response speed was more than five times that in a conventional a‐Si:H planar sensor.By varying the SiN film thickness, the threshold voltage of the photocurrent can be changed. The threshold value increased as the SiN film thickness is increased. As the PH3 concentration was increased, both the photocurrent and the dark current increased while the optical response speed decreased. The spectral sensitivity was similar to that in a conventional a‐Si:H planar sensor. Hence, no advantage of the photosensor using a‐Si:H was lost.
Analysis of slot antennas on a rectangular conducting box by using the fourier series expansion and galerkin's method
Authors: Fujino Yoshiyuki , Sawaya Kunio , Adachi Saburo 
Published: July 2007

AbstractSolution of the problem of scattering from a rectangular conducting box is important in the cases where the scattering characteristics from buildings must be estimated and where an antenna attached to a portable telephone is designed. Especially, a magnetic source antenna that can be built in a portable telephone has recently been proposed so that the importance of the analysis of antennas placed near a conducting box has increased. However, to date, no analytical results sufficiently valid for these antennas have been available.In this paper, an analysis technique for the antenna system near a three‐dimensional conducting box is developed. It describes the procedure to derive the impedance matrix using the Fourier series expansion and Galerkin's method as well as the method to introduce the continuity condition of the surface current on each side of the rectangular body. As an example, the present method is applied to a slot antenna located on a surface of a rectangular box and the input admittance and the radiation pattern are analyzed. Through comparison with the experimental results, the validity of the present method is confirmed.