bluuebunny/crossref_metadata_2025 huggingface dataset:
1.5 μm ingaasp fabry‐perot cavity‐type laser amplifiers
Authors: Mukai Takaaki , Saitoh Tadashi , Mikami Osantu
Published: July 2007

To understand the small‐signal gain, signal‐gain saturation and noise characteristics of 1.5 μm InGaAsP Fabry‐Perot cavity‐type laser amplifiers, two types of laser amplifiers having different thickness of the active layers were tested. It was found that the larger the gain coefficient (i.e., the larger the injected carrier density), the higher the gain and saturation output of the amplifiers, and the lower the noise level. Stern's gain calculation method was applied to materials for the 1.5‐μm region. It was found theoretically that these characteristics are due to the dependence of the carrier lifetime on the injected carrier density and the dependence of the saturation intensity and the population inversion parameter of the gain coefficient, by using the material parameters taking account of the Auger effect and the structure parameters of the device. The feature of the 1.5‐μm amplifiers is that the reduction of the carrier lifetime with the increase of the carrier density becomes more significant due to the Auger recombination process. It is important for improving the saturation output by positively utilizing this phenomenon to design the amplifier structure so that the amplifiers can be operated in a high‐gain region.
High‐linearity and high‐speed CMOS 1‐chip A/D, D/A converters. all‐digital linearity error correction (LECS)
Authors: Matsuya Yasuyuki , Akazawa Yukio , Iwata Atsushi
Published: July 2007

This paper describes an all‐digital linearity error correction (LECS) method for A/D and D/A converters, and presents the design and performance of single‐chip CMOS LSI converters utilizing this new technique.

In general, the deterioration of converter accuracy is caused by discontinuity changes (jumps) of the converter characteristics due to component tolerances in the weighting network. The proposed correction method is based on a design ensuring that only negative jumps occur which are then eliminated digitally by a shifting of digital output (input) codes. Since this method does not require analog circuits, the number of noise sources is minimum and high reliability is achieved by eliminating physical trimming.

Experimental CMOS converters have been realized utilizing the proposed method; the D/A converter provides an S/N of 92 dB at 150 ksps, and 87 dB is achieved by the A/D at 78 ksps. Thus, the possibility of realizing high‐quality audio converters by MOS process technology has been demonstrated.
Finite element analysis of the waveguide eigenmodes‐a novel method of employing transverse electromagnetic fields
Authors: Matsuhara Masanori , Angkaew Tuptim , Kumagai Nobuaki
Published: July 2007

There are numerous reports on the numerical analysis of variational expressions for a waveguide with an arbitrary cross section and structure by means of a finite element method. In conventional methods, cumbersome procedures or special programming techniques are required to discriminate the true solution of the guided mode from the spurious solutions. In this paper, a new variational expression for the β propagation constant is derived in which the transverse electromagnetic field components e.t and ht are used as the testing functions. A method is presented for numerical analysis of this new variational expression by means of the finite element method. It is pointed out that the guided mode and the spurious mode can easily and completely be discriminated by only the realistic condition that the propagation constant of the guided mode is real, without resorting to cumbersome procedures or special programming techniques. The new variational expression is well suited for a finite element analysis and resolves difficulties and ambiguities associated with the finite element methods based on the conventional variational expressions.
Studies of fabrication process for logic gate array using Pb‐alloy josephson junction
Authors: Hirano Mikio , Yano Shinichiro , Yamada Hiroji , Kawabe Ushio
Published: July 2007

Using a Pb‐alloy Josephson integration process with basic rules of junction dimension 3.5 μmϕ, minimum line width 2.5 μm, and junction current density Jc = 500 A/cm2, a Josephson logic gate array with integration of 576 gates/chip has been fabricated. For the device fabricated in the Pb‐In‐Au/oxide/Pb‐Bi system, hillocks have been observed in the base electrode film, and voids frequently occur in the counter‐electrode film, with the junction being short. This failure has been attributed to the electromigration of Bi in the counter electrode into the base electrode, thereby breaking the junction. Using a Pb‐In‐Au film formed at low temperature (∼0°C) for a base electrode and a Pb‐Au film for a counter electrode, junction shorts have been eliminated completely. A junction current variation of ±10% has been obtained which is one‐half that for conventional junctions. The yield for good chips by visual inspection is 10 30 percent. The delay time of signal propagation has been measured by the operation of various gate chain circuits using fabricated logic array chips. The gate delay time of 33 ps for the 2‐input OR gate and 54 ps for the 2‐input AND gate has been obtained.
A pulse‐driven PNPN switch circuit
Authors: Inabe Yasunobu , Hayashi Toshio , Kimura Tadakatsu , Tanabe Masaaki
Published: July 2007

This paper describes the design method of a pulse‐driven PNPN switch circuit which utilizes the N‐region carrier storage. Features of the circuit are: (1) there are no dc‐gate leakage current to the main current circuit, (2) the leakage of the pulse gate current to the main current circuit can be prevented by applying pulses to the P‐gate and the cathode (in a reverse phase), (3) both the driving circuit and the PNPN switch can easily be mounted on the same chip, (4) the P‐gate cathode stabilizing resistance and the dv/dt protection circuit can be applied as a conventional PNPN switch, and (5) the on‐state of the switch can be held even in a region where the anode current is smaller than the holding current by applying the gate pulse repeatedly. The relationship between the turn‐on characteristic of the fundamental PNPN switch and the circuit parameters were made clear by comparing the circuit equations with the experimental results. Based on these comparisons, the pulse‐driven PNPN switch was designed, and a good agreement between the design formulae and experimental results was confirmed. The condition which can avoid the false ignition of other PNPN switches on the same chip was analyzed. Consequently, the integration of multiple switches on a single chip became possible.
Room temperature pulse operation of GaAs surface‐emitting laser by using TiO2/SiO2 dielectric multilayer reflector
Authors: Kinoshita Susumu , Kobayashi Takahiro , Sakaguchi Takahiro , Odagawa Tetsufumi , Iga Kenichi
Published: July 2007

An Au‐evaporated film has conventionally been used as a reflecting mirror on the front side of GaAs surface emitting lasers to realize high reflectivity of the cavity ends. However, since Au‐evaporated films absorb light, the maximum reflectivity possible without drastically reducing the output efficiency has been around 85%. Therefore, in this work, a TiO2/SiO2 dielectric multilayer reflector has been used as a reflecting mirror on the front side. After the evaporation equipment is designed and fabricated, five pairs of TiO2/SiO2 dielectric films are formed on a GaAs substrate and its reflectivity characteristics evaluated. A peak reflectivity of 90% has been realized at 0.88 μm which is the resonant wave length of GaAs lasers. Next, five pairs of TiO2/ SiO2 dielectric multilayers are formed on an actual surface‐emitting laser and its laser characteristics are measured, with a resulting threshold current of 400 mA under a pulsed operation at room temperature.
Numerical analysis of radiation effects in MOS capacitors
Authors: Sano Eiichi , Kimura Tadakatsu
Published: July 2007

The Poisson equation, current‐continuity equations and rate equations for charged traps were solved numerically to analyze the flat‐band voltage shift due to irradiation for MOS capacitors. Good agreement was obtained between computed and previously reported flat‐band voltage shift dependence on gate voltage during irradiation, accumulated dose and oxide thickness. The physical meaning of the flat‐band voltage shift was clarified for the distributions of calculated charged traps and electrostatic potential. Moreover, the influence of electron hole mobilities, and trap density on the flat‐band voltage shift is discussed.
Design for SMF optical focusing‐beam system using GRIN rod lens
Authors: Kishimoto Ryozo
Published: July 2007

Optical communication systems using single mode fiber (SMF) with a low loss and a broad band are promising for a long distance large capacity transmission. In this paper, we found a design guideline for the actual accuracy required in the fabrication and for realizing a low insertion loss LD module essential for the system realization. A modal expansion method has been used for analysis of the coupling system with a GRIN rod lens created on one end of the fiber for an efficient coupling. Next, coupling experiments have been carried out to confirm the validity of the theoretical analysis. In addition, a low loss coupling system with a coupling loss of about 2.8 dB has been realized. Allowable displacements have been studied which determine the practical accuracy in the fabrication of the LD module. It is found that a coupling system with a large tolerance in displacement allowance can be realized with a focusing rod lens.
Characteristics of DC–to–DC converters operating in current programmed mode
Authors: Harada Koosuke , Sato Terukazu , Miyazaki Izumo
Published: July 2007

The switching regulator is a device which controls the output voltage by on‐off (duty‐) ratio of the switching. One of the methods to control the duty‐ratio is the current programmed control, where the switch is turned on by the clock of the specified frequency and off when the switching current or the reactor current reaches the specified value. This paper considers the step‐up (buck‐boost) circuit as an example of the current programmed dc‐to‐dc converter. Analyses are made for the steady‐state characteristics, dynamic characteristics and the stability, using the state‐space averaging. The result is compared with that of experiment. It is shown that the peak current control circuit is essentially of constant‐current characteristics and can easily be protected against overcurrent. It is also seen that not only can the capacity of the circuit be expanded easily by parallel connection, but also the circuit has better characteristics against input variation than the earlier power supplies employing the duty‐ratio control.
Stability of magnetic and magneto–optical properties of tbco sputtered films
Authors: Tokunaga Takashi , Haradas Mitsuaki , Honda Shigeo , Ohkoshi Masatoshi , Kusuda Tetsuzo
Published: July 2007

Noncrystalline TbCo films were formed by sputtering. Single‐layered films, 1000 Å in thickness without protective layer, were deposited, with the substrate biasing potential VB varied from 0 to −200 V. The room temperature stability of the magnetic and magneto‐optical properties of the films in atmosphere were investigated. The dependence of the magnetic property on the deposition conditions (VB and Ar pressure) was also investigated and it was found that the TbCo film became a film magnetized in a normal direction (normally magnetized film) under a certain condition. The saturated magnetization Ms changed to the Co‐rich side with time because of the selected oxidization of Tb atoms. The change of Ms was dependent on VB and became more rapid as the bias voltage increased. This was related to the film structure, and was considered to be due to the fact that the film became porous when the bias voltage was between −150 and −200 V and the oxygen diffusion to the film became easier. The reaction during this process is diffusion‐dominant. There was no time‐dependence in the Faraday rotational angle θf at the saturated magnetization but the Kerr rotational angle increased as the oxidation progressed. The normally magnetized film was formed when VB × 0 and the Ar pressure was 10 mtorr or when VB was between −100 and −150 V.
A josephson timed regulator
Authors: Ohhata Masanobu
Published: July 2007

A Josephson timed regulator has been designed and tested which supplies timed bias current to logic gates, such as EX‐OR and NOT gates. This regulator consists of four SQUIDs in series, where the output line is coupled twice to each SQUID. In addition, this output line functions as the SQUID control line. As a result, all SQUID junctions are able to simultaneously switch even if the junction critical current is scattered. This regulator is fabricated using Pb alloy technology, successfully tested, and then favorably compared with computer simulation results.
Forming process in Al‐Al2O3‐au sandwich structures
Authors: Hirano Mikio , Miyamoto Nobuo , Matsumoto Goro
Published: July 2007

This paper discusses the forming phenomena under a high‐electric field using an Al‐Al2O3‐Au sandwich structure with a 10 60 nm thick Al2O3 film. When an electric field of ∼106 V/cm is applied to the sandwich structure in a vacuum lower than 1 Pa, the transition of the high‐resistance state to the low‐resistance state, so‐called “forming,” is observed. During the forming process, the injection of Au to the Al2O3 film formed the electric leakage path and the local structural change in both the Al electrode (the negative electrode) and the Al2O3 film occurred. The appearance of the negative resistance seemed to be caused by the destruction and reconstruction of the electric path.

The sandwich structure with an A12O3 film implanted with A1+, B+, O+, He+, N+ or Ar+ shows the pre‐forming phenomenon observed in a sample treated in a vacuum for the forming process. The negative resistance was observed at the beginning in this sample. The sample also shows negative resistance in air. The sandwich structure with Au*‐doped A12O3 shows both the pre‐forming phenomenon and the negative resistance in both vacuum and air.
Flux control characteristics of ferrite orthogonal core using magnetic fluid
Authors: Oka Hideo , Iwata Junzo
Published: July 2007

Because of its orthogonal flux control system, the ferrite orthogonal core holds promise as a vector sensor. The combination of such a core and a magnetic fluid is of interest for control of flux with a simple system.

The results of experimental studies comparing vertical and tilted ferrite orthogonal cores in magnetic fluid indicate that the system can be used as a two‐dimensional inclinosensor.
Simultaneous stabilization of spectral linewidth and oscillation frequency of an external‐cavity laser diode by fiber‐optic ring‐resonators
Authors: Tai Shuichi , Kyuma Kazuo , Hamanaka Kohichi
Published: July 2007

The oscillation spectral linewidth and the oscillation frequency of a laser diode with an external cavity have been stabilized simultaneously with an optical fiber ring resonator used as a spectrum discriminator. Stabilization of the oscillation spectrum linewidth has been carried out with control of the phase of the fed‐back light and the oscillation frequency by control of the injected current. The oscillation spectral linewidth is 2 MHz and its fluctuation is less than 10 kHz p‐p and the equivalent oscillation frequency fluctuation is 2 MHz p‐p From these results, it is confirmed that an external cavity laser diode can be used as a light source of a ring resonator‐type fiber gyroscope.
Surface deformation of thin‐film magnetic disks and their stress analysis
Authors: Ohta Satoshi , Yoshimura Fumikazu , Terada Akira
Published: July 2007

Deformation of a small area (≤ 40 μm) on a magnetic disk (anodized Al‐alloy substrate with γ Fe2O3. sputtered surface) due to an external force was investigated. The results are that: (1) the amount of deformation (elevation or depression) on the surface of the disk is proportional to the load applied in the test. The elevation ratio α (amount of elevation/amount of depression; about 1 for a noncompressive material) has a similar trend, although its increase rate depends on the thickness of the anodized layer δ; (2) in the range of experimental load (≤ 50 g), α is greater than 1 when 6 is small (< 10 μm), and α is smaller than 1 when δ is large. The former is caused by a plastic flow of the Al‐alloy onto the disk surface due to a crack on the anodized layer forming a porous scratch. In the latter, the anodized layer is hardly broken so that a plastic flow onto the disk surface is suppressed; and (3) the distribution of the stress in the substrate was analyzed by the finite‐element method. When δ is small (2 μm), the maximum tension‐stress and the maximum shear‐stress occur on the substrate surface; and when δ is large (11 μm), they occur near the boundary between the anodized layer and the Al‐alloy. These explain qualitatively the experimental results in (2).
Two‐dimensional analysis of thermal oxidation of silicon
Authors: Sakina Yasuharu , Ohno Tsuneo , Matsumoto Satoru
Published: July 2007

The dependence of the two‐dimensional oxidation of silicon on the temperature and the oxidation period was investigated. A (110) silicon wafer whose surface was step‐shaped by anisotropic etching was oxidized between 900 and 1150°C and the cross sections of the oxide layers at the upper and lower edges were observed by SEM. The numerical simulation of the oxide film growth was carried out by considering both the diffusion and the surface reaction at the Si/SiO2 interface of the oxidants. The result was compared with the experimental result, and no orientation dependence in the growth rate was observed at high oxidation temperature. However, at the lower temperature, the growth rate in the (110) surface was higher than that in the (100) surface. This is believed to be due to the fact that the thermal oxidation at high temperature is diffusion‐dominated, while at the lower temperature, it is dominated by the surface reaction. In the low‐temperature oxidation at the upper edge, there was considerable decrease in the growth rate at the corners and the shape of the film was deformed. However, no such observation was made in the high‐temperature oxidation. The reason for this is believed to be the stress caused by the low‐temperature oxidation and the stress relaxation during high‐temperature oxidation. On the other hand, regardless of the oxidation temperature, the oxide film was deformed at the corners of the lower edge. This is believed to be caused by the deficiency of the oxidant.
dv/dt drive circuit method for pnpn switch with dv/dt protection
Authors: Suzuki Masayoshi
Published: July 2007

This paper describes a dv/dt drive method in complex pnpn switch circuits with both large critical slew rate (200 V/0.2 μs) and high gate sensibility (0.1 mA). The circuit consists of a thyristor and the protective circuit composed of an npn transistor switch and a driver.

However, a false dv/dt turn‐on phenomenon of the thyristor is found in this structure under the condition that the storage time of the transistor is shorter than the gate recovery time of the thyristor.

To avoid this phenomenon, a new dv/dt drive method is proposed by using a pnp transistor instead of a diode in the protective circuit.
Dynamic characteristics of phase and series cascade voltage regulator and effects of ambient temperature
Authors: Matsuda Masanobu , Kanata Yakichi
Published: July 2007

The authors have developed a phase and series cascade voltage regulator which has comparable efficiency to a switching voltage regulator and a degree of ripple suppression and an accuracy as good as that of a series voltage regulator. In this device, the input voltage is adjusted by the thyristor phase control so that the collector‐to‐base voltage of the series control transistor is always zero. The static characteristics of the device have been reported. This paper presents the dynamic characteristics of the circuit and discusses the operating limit of the temperature characteristics. It is found that the frequency response is determined mainly by the operational amplifier and the series control transistor, and by the trigger period of the thyristor gate. The effect of the operational amplifier and the series control transistor in the series regulator is especially significant, but the phase control rectifier exerts less influence on the frequency characteristics. On the other hand, the operating limit of the temperature characteristics is determined by the minimum firing phase angle. Except for cases of circuits operated near the lower limit of the input‐output characteristics and near the full load current, the operating range is found to be extremely wide. A practical circuit is used for confirmation of the stability of the circuit and the frequency response for the fundamental characteristics. In addition, the operating limit of the temperature characteristics and the effect of the ambient temperature on the operating limits of the input‐output characteristics and the load characteristics are studied theoretically and experimentally.
Third‐order digital phase‐locked loop with improved stability
Authors: Yamasaki Shoichiro , Nakagawa Masao
Published: July 2007

When a signal from a moving source is received by a phase‐locked loop (PLL), the input‐signal frequency of the PLL often changes in a ramp‐function state with a constant‐frequency offset. In such a case, a perfect third‐order PLL is needed to track the signal without steady‐state phase error. The conventional perfect‐integration third‐order PLL has a serious problem of being unstable for small‐amplitude inputs, and thus it cannot be used in practice in a low SNR environment.

This paper proposes three types of stable perfect third‐order digital PLL's (M‐DPLL) which are independent of the input‐signal amplitude. This M‐DPLL realizes the perfect third‐order behavior by combining three first‐order DPLLs using a digital signal processing technique. The excellent characteristics of this M‐DPLL are confirmed by theoretical analysis and computer simulation.
Study on the design of ultraminiature reed switches
Authors: Yokokawa Toshiki , Hinohara Kunio , Nagai Akira
Published: July 2007

Since the miniature and high‐density electronic apparatus was developed, the miniaturization of electronic components has been in high demand. The reed switch is not an exception. The reed switches for the P.C.B. mounted miniature relays and the surface mounted miniature relays have also been in high demand. The reed switch which has been used for communication is rather large (46 mm in its entire length and composed of a 28‐mm‐long glass tube). However, the design of the switch itself is almost ideal.

This paper discusses the miniaturization limit of the reed switch with respect to the mechanical and magnetic properties. Assuming that the breakdown voltage, the contact rating and the carry current decrease, it was found that the ultraminiature reed switch with glass inner length of 3.6 mm and glass inner diameter of 0.8 mm can be mass‐produced by the existing processing technology.
Characteristics of thin‐film energy‐transfer dye laser with DFB oscillator‐amplifier system
Authors: Muto Shinzo , Uchida Haruki , Nakamura Keiji
Published: July 2007

The operation of many thin‐film ETDL's covering a wide wavelength range from near UV to near infrared has been reported. However, the spectral narrowing and tuning of these solid dye lasers are required inevitably for several applications. Therefore, to obtain this operation, the oscillator with a dynamic distributed feedback (DFB) and the optical amplifier were constructed simply on the thin‐film ETDL waveguide. As a result, the tunable laser emission with narrow spectrum and its amplification were obtained easily over both gain bands of donor and acceptor dye. Thus, this system is available as a compact solid dye laser with wide tuning range.
A high–quality color printing technology by electrophotography
Authors: Tanaka Tomoaki , Hoshino Yasushi
Published: July 2007

Although color printing technology has actively been developed, the technology to satisfy the tone levels and resolution (the main factors in an image quality), printing speed and stability has not been established.

This paper attempts to obtain a high‐quality color printing with high speed and high stability. First, the effects of the tone levels and resolution on the image quality were examined. To find their best combination, evaluation experiments were carried out by using various values of the tone levels and resolutions. The results show that a high‐quality image requires a resolution greater than 6 dots/mm and a tone level greater than 32.

Second, it was confirmed that electrophotography with an elliptical laser beam scanning is superior to that with a conventional circular laser beam scanning in the tone level and stability. Experiments were done on the former with the conditions which satisfy the forementioned values, by employing the submatrix‐type dither. As a result, a high‐quality image with a resolution of 6 dots/mm and a tone level of 49 was obtained. Samples processed in this technology show that an image has no false contour and no roughness, that the forede‐scribed conditions for a high‐quality image are justified, and that this technology can be realized.
Fiber excess length in a cable containing optical fiber ribbons
Authors: Hatano Satomi , Kokubun Toshinao , Hogari Kazuo , Katsuyama Yutaka
Published: July 2007

A cable containing optical fiber ribbons in a loose tube is promising for high‐density, multifiber and economical communication. This paper discusses the influence of excess fiber length.

Assuming that the optical fiber excess length (the difference between the lengths of the optical fiber and its container) causes the optical fiber to bend, the relationship between the excess length and sinusoidal bending radius has been obtained. It was found that the optical losses due to the sinusoidal bend of a graded‐index multinode fiber with core and outer diameter of 50 and 125 μm respectively, were inversely proportional to the square of the minimum radius of curvature. Also, the loss characteristic is the same as that in case of the uniform spiral bend. Based on these results, the method of estimating the optical losses due to the excess length was obtained. It was confirmed that the measured optical loss agreed with the estimated loss.

It was found that the excess length ratio β should be restricted between −0.05 and 0.2 percent to minimize the optical losses and fiber failure probability.
Two–dimensional photosensor using a–Si pin diodes
Authors: Senda Kohji , Susas Masahiro , Hiroshima Yoshimitsu , Takamura Tohru
Published: July 2007

This paper proposes a two‐dimensional photosensor composed of an a‐Si pin junction. The photosensor is constructed on the glass substrate. The pixel of the sensor is of a simple structure composed of two photodiodes connected in opposite directions between the vertical and the horizontal signal lines. The photodiode constructed by a‐Si pin junction has the function of the blocking diode, preventing the crosstalk in reading out the signal, in addition to the photoelectric conversion. The sensor is of the sandwich type composed of an a‐Si pin junction, and achieves the store‐and‐read operation with a high speed. A large reset noise is superposed on the input signal in the proposed sensor, but is eliminated by the differential amplifier with the double reading drive, leaving only the light signal. A two‐dimensional 5 × 5 photosensor was constructed experimentally, and the basic operation was verified. The photoelectric conversion characteristics are that the output signal is proportional to the input light with the sensitivity of 50 mV/lux·S and S/N of 12 dB.
An optical tactile sensor using the CT reconstruction method
Authors: Kawashima Toshio , Aoki Yoshinao
Published: July 2007

The tactile sensors used for robotics and electrical artificial hands are designed to provide force information. They are required to have the capability of not only detecting pressure distribution with high sensitivity, but also to carry strength and provide flexibility in grasping objects. This paper proposes a two‐dimensional tactile sensor based on the pressure‐optical transmission conversion system and the principle of computer tomography. The sensor consists of a three‐layered silicon rubber sheet and an array of opto‐electrical elements embedded in the edge of the sheet. The pressure distribution is detected as an optical transmission pattern. The transmission pattern is reconstructed to a two‐dimensional distribution using the algorithm of the computer tomography (CT) pattern reconstruction. The merits of this method are: 1) the sensor is flexible and suitable for grasping objects; 2) the number of components and signal lines is small; 3) the sensor can withstand excessive force; and 4) the sensor can be attached to a curved surface. In this experiment, using thirty‐two pairs of circular sensor arrays, the pressure distribution of 200 sites with 2.5 mm resolution was obtained. This paper describes the design, the mechanism of transduction, and the performance of the tactile sensor.
4–kbit bipolar RAM with on–chip address latch function
Authors: Nambu Hiroaki , Kanetani Kazuo , Yamaguchi Kunihiko , Homma Noriyuki , Todokoro Hideo , Akimoto Kazuhiro , Ogiue Katsumi
Published: July 2007

For speed‐up technologies for bipolar RAMs, an on‐chip address latch function, a new sense circuit using a dummy cell, a Darlington wordline driver, etc., have been reported. However, their effects still have not been clarified. According to the quantitative evaluation of the forementioned circuit technologies, with respect to the speed‐improvement and stable operation of memory cells in this paper, the speed can be improved by 30 percent and no instability of data retention occurs in memory cells even using the Darlington wordline driver. The 4‐Kbit RAM has been fabricated with the forementioned circuit technologies and the 1.5‐μm U‐groove isolation process. The high speed of the mentioned circuits and the stable operation of memory cells have been confirmed by evaluation using the EB tester. The performances obtained are access time of 3.5 ns (by using an on‐chip address latch function, it can be improved to 2.5 ns from the viewpoint of the system) chip area of 12.7 mm2, and power dissipation of 1 W.
Finite–element analysis of plane wave diffraction from dielectric gratings
Authors: Nakata Yasunori , Koshiba Masanori , Suzuki Michio
Published: July 2007

An analysis method based on the finite element method is proposed for solving the problem of diffraction of a plane wave by a dielectric grating. For both the TE and TM wave incidences, a systematic formulation is presented. Although numerous analysis methods have been reported on dielectric gratings, it is necessary in general to divide a grating into several layered planar dielectric gratings when a dielectric grating with an arbitrary profile is analyzed. On the other hand, the finite element method used in this paper enables direct treatment of a dielectric grating with an arbitrary profile without multilayered division. In practice, gratings made of grooves with rectangular, sinusoidal and trapezoidal profiles created on the surface of a semi‐infinite dielectric medium are analyzed. The results of analysis on the diffraction characteristics are presented. Next, as an example for groove gratings with complex geometry, the analysis results of the diffraction efficiency are presented for a holographic grating fabricated at IBM. The analysis results agree well with those by other methods and with experimental values so that the validity and usefulness of the present method are confirmed.
Fabrication of a–Si:H films by coaxial line type microwave hydrogen plasma CVD
Authors: Kato Isamu , Ueda Tetsuya , Hatanaka Kazuhisa
Published: July 2007

A double tubed coaxial line type microwave plasma CVD system has been developed for a‐Si:H film deposition using hydrogen and argon gases with pure SiH4 gas as the material gas. The film quality was evaluated as a function of the plasma condition.

Since the spreads of hydrogen and argon plasmas were in the range of 2‐3 cm and 8‐9 cm, respectively, the substrate was placed 10 cm from the end of the discharge tube to avoid bombardment of the substrate by high‐energy particles. The film fabricated under hydrogen plasma showed superior characteristics. The film deposited at the substrate temperature between 150 and 200°C were of high quality; predominantly SiH bond rather than SiH2 bond, a large value for the photo‐dark conductivity ratio (σp/σd − 105) and a small density of dangling bonds.

A high‐quality film can be fabricated under hydrogen plasma because a large amount of hydrogen radicals covers the film surface, thereby causing a thermal structural relaxation of silane radicals. This relaxation results when the silane radicals increase their surface mobility after the soft landing on the film surface.
Design and performance of high‐power 1.5 μm DFB lasers
Authors: Matsuoka Takashi , Yoshikuni Yuzo , Motosugi George , Enya Mitsuhiro
Published: July 2007

A comprehensive design for high‐power DFB lasers is discussed. An anti‐reflection/high‐reflection facet structure and optimized coupling between forward and backward propagation waves in continuous corrugation‐type devices are shown in to be essential for this purpose. By applying the forementioned optimization to 1.5 μm DFB laser parameters, a maximum output power of 45 mW and a quantum efficiency of 37 percent are obtained at 20°C. The devices oscillate in a single‐longitudinal‐mode with a side‐mode suppression ratio of more than 30 dB under 1 GHz sinusoidal modulation.
Composition control of some oxide films by means of a tri–pole magnetron sputtering system
Authors: Fukami Tatsuo , Teshima Osamu
Published: July 2007

This paper describes the newly developed Tri‐Pole Magnetron Sputtering System, which has the third magnetic pole of an electric magnet, or the control pole, in addition to the conventional N and S poles between them. The system can switch the polarity of the control pole through the direction of the coil current so that it can shift the target‐eroded region by the magnetic field configuration. Therefore, film composition can easily be controlled by an appropriate composite target of coaxial disks corresponding to magnetic field configuration, at the same time changing the duty ratio of the current flowing through the control‐pole coil to adjust the sputtering time of each target‐component. The system is superior in both controllability and stability because of its static operation without mechanical moving elements. The switching behavior of the sputtered region is clarified via the target erosion pattern. Then the applicability of the system to the composition control of lead titanate films, etc., is discussed.
A three‐dimensional resist shape simulator and its application to submicron VLSI process
Authors: Member Tetsuo Itoh, , Nonmember Toshiharu Matsuzawa, , Kadota Kazuya , Nonmembers Shuichi Hanashima,
Published: July 2007

A three‐dimensional photoresist shape simulator has been developed for the submicron process. Using this simulator, it is possible to analyze and optimize the photoresist process using an arbitrary projector, photoresist, and developer. In this technique, considering the man‐machine interface, the three‐dimensional shape of the photoresist can be shown in a colorgraphic VDT and plotter. Comparing the result of the threedimensional simulation using the contact hole pattern with that of the two‐dimensional simulation, a discrepancy occurs in the dimension less than 1 μm between the two techniques, and it has been found that threedimensional simulation is necessary when the width and depth of the pattern are in the same order. Using the three‐dimensional simulation, a resolution of 0.5 μm cannot be achieved when the wavelength of the light source is 435.8 μm, the numerical aperture of the projection lens N.A. is 0.28, and the coherency s̀ is 0.7. However, such a resolution can be achieved by using the wavelength of the light source of 435.8 nm, N.A. of 0.42, and s̀ of 0.5.
Analysis of reflection and transmission characteristics of step discontinuity in rectangular dielectric waveguides
Authors: Tomabechi Yoshiro , Matsumura J. P. Kazuhito
Published: July 2007

This paper calculates the reflection and transmission coefficient at a discontinuity in rectangular dielectric waveguides. At the discontinuity, waveguides of two different sizes are connected concentrically. Generally speaking, radiation modes generated at the discontinuity in open waveguides make analysis difficult.

Here, double Fourier transformation is applied to field distributions at the discontinuity so that a guided and radiation mode can be treated identically. Since the reflection and transmission coefficient can not be obtained immediately by solving the boundary condition equations at the discontinuity, a ratio of electric and magnetic field intensities of the radiation mode is introduced and converged to constant by an iterative approximation. This approximation formula is derived from an orthogonal relation between the guided and radiation mode. If this ratio is converged to a steady value, the reflection and transmission coefficients are converged simultaneously. In addition, the reflection, transmission and radiation power at the discontinuity are calculated numerically. These results are compared with those obtained from the mode matching method which is useful when the discontinuity is so small.

The theory in this paper is advantageous in analyzing the discontinuity at a waveguide junction. The analytical method is applicable to an off‐axial junction of the waveguide and the analysis of a rectangular dielectric rod antenna.
NMR fast line‐scan imaging using a line‐shaped focusing field
Authors: Yamada Yoshifumi , Goto Takao , Tanaka Kunio
Published: July 2007

A new NMR imaging technique is described. A selective excitation is given in a line‐shaped focusing field. The spin distribution in the one‐dimension line‐shaped excitation region is detected with a linear magnetic field gradient. The methods of generating the line‐shaped magnetic focusing field and its scanning are described together with the selective excitation characteristic. Experiments of imaging with an 819‐kHz pulsed NMR system and their results are shown. The data collection time of the method was examined, showing much shorter time than conventional line‐scanning methods. This is because the spin excitation is carried out only for a necessary region. When a single slice is required, the imaging time can be about the same period as in a conventional NMR‐CT.
Improved integral equation method for electromagnetic scattering problems
Authors: Matsuhara Masanori
Published: July 2007

The integral equation method for electromagnetic‐wave scattering problems has difficulty in that we can not obtain a unique solution when the wave numbers of electromagnetic waves agree with the eigenwave numbers of the system under consideration. In this paper, we derive an integral equation satisfied at arbitrary observation points inside a scattering body and propose a method to place all finite numbers of the observation points (this number agrees with the number of the expansion coefficients for approximating the unknown field function) on an appropriately arbitrary closed curve located inside the scattering body. Through the newly proposed method described in this paper, we can easily avoid an inherent difficulty of an integral equation, compared with the existing methods, specifically, by adding internal conditions and by using integral equations of mixed types. As a numerical example, we solved a case of a plane wave incidence on a perfectly conducting elliptic cylinder. Using the boundary elements method, we carried out numerical calculation and showed that the solution of a high degree of precision can be obtained easily.
A method to measure position and attitude of a tunneling machine
Authors: Nakano Yusuke , Sugimoto Sadao , Arai Hitoshi
Published: July 2007

Development of a method to measure the position and attitude of a tunneling machine is required for constructing a curved and long tunnel with a small diameter for communication cables. This paper presents a method to satisfy this requirement. Two coils (“send coils”) are set on the ground to generate an ac magnetic field. Another coil (“search coil”) to detect this magnetic field is set on the tunneling machine under use. This search coil rotates on orthogonal planes, one of which is parallel to the direction of the tunneling‐machine progression. The position and attitude of the machine are calculated from the voltage induced in the search coil. The direction of a component of the magnetic field at an arbitrary position (with reference to the send coils) is essential in this method; this was obtained from theoretical (the finite‐element method) and experimental values. Appropriate dimensions of the search coil were found by introducing “the height/width ratio” and “the winding ratio.” The detection accuracy of this method is about 20 cm on a horizontal plane, and about 2° in attitude, thereby confirming its effectiveness.
A method for analyzing coupled inhomogeneous waveguides supporting two modes and its application
Authors: Ono Kazuo , Sawa Shinnosuke
Published: July 2007

In this paper, the successive approximate method is used to treat the two‐mode loose coupled inhomogeneous systems where the propagation constants and coupling coefficients are functions of the propagation distance. That is, the successive approximate method is used to analyze in a general way the response of the system of coupled inhomogeneous equations. As a result, two or three comprising conditions are obtained for the devices to be used as mode transformers. To verify the correctness of the present method, the results are compared against those of the so‐called approximate integral method applied to the inhomogeneous systems in which only the coupling coefficients are varied with propagation distance. It is indicated that similar results are obtained. For example, in the case of the tapered lens medium, which has previously been treated from a wave point of view, no contradiction is observed. Finally, to demonstrate application of the present method, we use two‐mode directional couplers that are simple to construct and have only small losses.
Analysis of the operation of surface‐emitting‐type optical threshold device
Authors: Nitta Jun , Iga Kenichi
Published: July 2007

This paper proposes a surface‐emitting‐type optical threshold device and analyzes its characteristics. For a surface‐emitting laser resonator with a saturable absorber, its static characteristics and small signal analysis with a current or light injection are obtained from rate equations. As a result, the possibility of an optical threshold device which operates with a practical optical energy of approximately 30 kW/cm2 has been shown. Furthermore, it has been shown that the optical threshold varies by controlling an injection current, and that AND and OR logics are possible with one device. As a result of small signal analysis, the device is shown to have a bandwidth of approximately 1 GHz.
ISFET incorporated in a differential amplifier
Authors: Tsukada Keiji , Maruizumi Takuya , Miyagi Hiroyuki
Published: July 2007

The output of the ISFET (Ion Sensitive Field Effect Transistor) was obtained as a voltage signal. To achieve the temperature compensation, a differential amplifier composed of ISFET and MOSFET was fabricated. For integration, the process and circuit designs for the ISFET and MOSFET were done carefully by considering both the device fabrication process and the electrical properties of the device. Polycrystalline silicon was used for the connection between the devices and the MOSFET gate electrode. The entire device surface was covered with Si3N4/SiO2 to ensure the waterproof properties of the device. As a result, the MOSFET could be located near the ISFET and both FETs could be processed in the same manner. The fabricated ISFET could produce the voltage signal in accordance with the change in the gate membrane potential of the ISFET. The sensitivity of the device was 49 mV/pH. In addition, temperature compensation in the ISFET was achieved and the temperature coefficient was −0.8 mV/°C.
DC and switching characteristics of inverted structure AIGaAs/GaAs HBT's
Authors: Nozu Tetsuro , Akagi Junko
Published: July 2007

Inverted type, or collector‐top A1GaAs/GaAs HBT's and their ring oscillators have been fabricated and dc characteristics have been evaluated. In case of collector area SC/external base area S < 0.8, the external base current is large and hFE is reduced. In case of SC/S > 0.8, the upper limit of hFE is about 20. The ring oscillator characteristic in a DCTL ring oscillator is tpd = 63 ps and the one in an NTL ring oscillator is tpd = 77 ps. An emitter‐top HBT with impurity profile and structural shape identical to those for the proposed collector‐top HBT is used for a ring oscillator. The characteristic of the latter have been estimated by means of SPICE and compared with the measured results for the collector‐top type. It is found that the collector‐top HBT has a higher switching speed and is more suited as a high‐speed logic device than the emitter‐top HBT.
AIGaAs/GaAs heterojunction hall device
Authors: Taguchi Takashi , Sugiyama Yoshinobu , Tacano Munecazu
Published: July 2007

Since 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

To 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.