bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron injection characteristics of MNOS nonvolatile semiconductor memory structure using the reverse breakdown of the PN junction
Authors: Ohnishi Kazunori , Miura Katsuhiro
Published: July 2007

In this paper, we describe an improved carrier injection method for the metal nitride‐oxide semiconductor (MNOS) structure, which is a prospective nonvolatile semiconductor memory device. The investigation is based on the prediction that carrier injection should be improved by increasing the carrier density at the Si surface and by lowering the tunneling barrier height of the SiO2 and that these conditions should be realizable by using the current flow due to reverse breakdown of the pn junction near the channel region of the Si surface under the gate electrode.

Experiments indicate that the flatband voltage shift in the presence of electron injection is large as a result of the reverse breakdown current of the pn junction. Electron injection was further improved by an additional lowering of the tunneling barrier height associated with the voltage drop across the resistance connected to the bias circuit of the pn junction. This voltage drop was produced by the current flow due to reverse breakdown of the pn junction.

Faster, stronger carrier injection from the Si surface to the traps in the insulator of MNOS structure can be realized by optimizing the doping densities in p and n regions and optimizing the resistance connected to the pn biasing circuit. This method is useful for electrical erasable nonvolatile semiconductor memory (EEPROM) devices without voltage up‐converter circuits.
64 K × 1 BiCMOS ECL RAM with cross‐coupled level conversion circuit
Authors: Shiomi Toru , Takano Satoshi , Honda Hiroki , Hatanaka Masahiro , Anami Kenji
Published: July 2007

This paper considers the high‐speed, low‐power consumption BiCMOS ECL RAM and discusses the input buffer circuit, including the level conversion circuit which transforms the ECL level to MOS level. It is seen that the following circuit is the optimal from the viewpoints of the delay time and the power consumption. The address buffer circuit is composed of the ECL circuit and the emitter follower, the level conversion circuit is a CMOS cross‐coupled circuit, and the driver circuit is composed of the Bi‐nMOS driver. The high speed and low current dissipation performances are obtained with the delay time of 1.6 ns, current dissipation of 2.32 mA.

The sense amplifier is constructed using ECL circuit with the constant‐current source with small dependencies on the temperature and the source voltage. A high speed is realized by producing the output from the wired‐OR of the emitter‐follower transistors of the blocks, with the time from the common data line to the output being 1.6 ns. Based on the obtained circuit structure, a 64 KX 1 bit BiCMOS ECL RAM is realized using the 1‐μm BiCMOS, with the access time of 7 ns and the power consumption of 800 mW [1].
Optical beam scanner with phase‐variable waveguides‐improvement on deflection characteristics
Authors: Moriki Kazunori , Aizawa Kouji , Hattori Takeo , Iga Kenichi
Published: July 2007

An optical beam scanner with a variable phase waveguide can perform a high‐speed scanning into an arbitrary angle. Monolithic integration of the scanner with a light source can be realized by means of fabrication with semiconductor materials. However, in principle, the scanned beam has multiple peaks so that the maximum scanning angle and the power efficiency are limited.

To relax the limitations and to improve the characteristics, the following methods are investigated in this paper: (1) a method to suppress the subbeams; (2) a method to increase the angle between the main beam and the subbeams; and (3) a method in which the entire envelope is scanned. The following results were obtained.

(1) By chirping the waveguide spacing, the limitation of the scan angle due to the existence of the subbeams is removed.

(2) By reducing the waveguide spacing and varying the widths of the adjacent waveguides so that the mode coupling between the waveguides is eliminated, the scan angle is increased.

(3) Although the fabrication is difficult, the wavefront in the waveguide is tilted so that the envelope itself is scanned and the inherent limitation of the scan angle is eliminated.
Spot sizes of beam waves propagating along a two‐dimensional inhomogeneous medium
Authors: Hashimoto Masahiro
Published: July 2007

The Gaussian beam propagating in an inhomogeneous medium is analyzed based on the complex ray optics, and the analytical solution obtained is reported. It is assumed that the medium is inhomogeneous in the transverse direction and homogeneous in the longitudinal direction. A beam wave is assumed which propagates in such a medium with undulation. Its spot size is derived as a general solution. Further, by means of two examples, the spreading of the beam wave due to the dispersion is studied. The general solution obtained in this paper is the rigorous solution of the geometric optics.
Structure of the test program for vlsi memory devices and its application
Authors: Hamada Mitsuhiro , Nishimura Yasumasa , Tada Tetsuo
Published: July 2007

VLSI memories have been diversifying along with high density and high speed. With diversification, the evaluation test program also must handle each VLSI memory, and the efficiency of its generation is an important issue.

In this paper, to evaluate diversifying VLSI memories, a program structure is described which can create evaluation test programs quickly for semiconductor test equipment, especially memory testers. The test program presented herein has a module structure consisting of utility groups for evaluation, a main program, and subroutine programs which describe the specific test conditions for each VLSI memory. Also, it can handle the evaluation of various VLSI memories with minimum programming.

As a result of using this program structure for the evaluation test programs for 16 kinds of VLSI memories, it has been confirmed that the program development time can be reduced to one‐fifth that of the conventional method and the evaluation time can also be reduced by one hour.
Design of ECL 1‐Mb BiCMOS DRAM
Authors: Kitsukawa Goro , Kawajiri Yoshiki , Itoh Kiyoo , Yanagisawa Kazumasa , Nakamura Masayuki , Miyazawa Kazuyuki , Akiba Takesada
Published: July 2007

This paper describes an experimental 1.3‐μm, 1‐Mb BiCMOS DRAM, the first DRAM to use an ECL interface. The results are as follows: (1) quantitative analysis shows that direct sensing of a small read‐signal voltage on the data lines before amplification by the CMOS rewrite amplifier gives an access time 8 ns (up to about 30 percent) faster than conventional common input/output (I/O) sensing; (2) the bipolar cascode amplifier is characterized by the pulsed emitter‐bias current. Computer simulation and experiments show that its delay time is not sensitive to changes inVccat the rate of about 50 mV/ns; (3) a new bipolar ECL I/O circuit with a power‐switching function is shown to reduce the standby current of a 1‐Mb ECL chip to about one‐fifth that of an ECL chip without a power‐switching function; and (4) the experimental chip has an access time of 24 ns, power dissipation of 730 mW, and a chip area of 62.2 mm2under typical conditions ofVEE= −5.2 V,Ta= 25°C, output capacitanceCL= 10 pF and a cycle time of 70 ns, andnMOS/pMOS transistors with gate lengths of 1.4/1.7 μm.
An evaluation of FFT circuits based on a three‐dimensional VLSI layout model
Authors: Kurokawa Takakazu , Ichijo Yasuhiko , Oowada Masakatsu
Published: July 2007

Performance evaluation of VLSI circuits has been studied widely following the progress of VLSI technology. In these studies, the amount of material as well as the wire routing lengths required for the VLSI layouts for sorting circuits, FFT circuits, interconnection circuits, and so on, have been discussed. These discussions are based on a fact that the wire routing controls the VLSI performance, but they all concentrate on conventional two‐dimensional (2‐D) VLSI circuits. By contrast, new integration technology, i.e., so‐called 3‐D VLSI technologies, have been developed to overcome the barriers to the progress of 2‐D integration technology.

This paper discusses the performance evaluation of FFT circuits based on 2‐D VLSI technology as well as 3‐D VLSI technology. As the evaluation results, the amount of material can be reduced about one O(N−1/2 log N)‐th to one O(N−1/2 log−2 N)‐th by using 3‐D construction rather than the conventional 2‐D VLSI circuit. Furthermore, the optimum FFT circuit based on the AT2 complexity for 2‐D integrated circuits cannot always be an optimum circuit based on the V2T3 complexity for 3‐D integrated circuits. Therefore, it will be necessary to reevaluate each circuit based on the V2T3 complexity to fabricate it as a 3‐D VLSI system.
Design of multiquantum barrier (MQB) and experimental verification of electron wave reflection by MQB
Authors: Takagi Takeshi , Koyama Fumio , Iga Kenichi
Published: July 2007

With a view to form a clad layer corresponding to the shorter wavelength of an AlGalnP visible laser, the trapping effect of the carrier by the introduction of the multiple quantum barrier (MQB) is discussed. It is found that the hypothetical barrier by the MQB can be made higher if both the well layers and barrier layers comprising the MQB are thinner. The effectiveness of the MQB also is confirmed at the actual barrier height experienced by the electrons in the active layer considering the Fermi level of the MQB region. Further, it is found that for a shorter wavelength, the modified MQB is useful where the potential difference between the well layer and the barrier layer of the MQB is large and the wavelength can be as short as 600 nm.

Also, as an experimental verification of the effect by the MQB, the PL using a GaAs/AlGaAs system and theI‐Vcharacteristic of then‐i‐ntunnel diode are used for evaluations. As a result, the carrier‐trapping effect by the MQB is confirmed. Further, it is confirmed also that the height of the hypothetical barrier by the MQB almost coincides with the value obtained by the computation.
Scattering from strip gratings with surface resistance: In the case of general anisotropic substrates
Authors: Asai Masamitsu , Ozaki Akira , Yamakita Jiro , Sawa Shinnosuke
Published: July 2007

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

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

This paper discusses erbium‐doped (Er‐doped) optical‐mode silica fibers for which vigorous research efforts have been carried out in recent years. The fabrication techniques and the amplification characteristics with semiconductor lasers used as the excitation source are investigated. As the fabrication of Er‐doped optical fibers, the vapor axial deposition (VAD) method, which is one of the fiber manufacturing techniques, is used. The rare earth doping into the porous material (in vapor phase) by using this method and the possibility of controlling the Er concentration (up to about 1000 ppm) are considered.

As the evaluation of amplification characteristics, experimental results of the dependencies upon the pumping wavelength and Er concentration are presented. In particular, in regard to the dependency upon the Er concentration, which is quite important in highly efficient amplifiers, it is shown that there is a serious degradation in the amplification characteristics when the concentration is increased, even at the low doping level of 500 ppm. The deteriorative mechanisms also are discussed.
Reduction of crosstalk errors in a polarization interferometric optical heterodyne fiber sensor
Authors: Kurosawa Kiyoshi
Published: July 2007

It has been proposed that the dual‐frequency optical sources with mutually orthogonal linear polarizations be used and that the optical heterodyne method be applied in the measurement of the birefringence of optical sensors.

This paper presents the theoretical and experimental investigation results of a new and easy technique which reduces the measurement errors caused by the crosstalk between the polarization states. The technique is based on the adjustment of the contribution of the polarizations to the light signal by changing the azimuths of the signal and reference analyzers included in the measurement setup. In this way, the effect of the interference due to the crosstalk is reduced.

To evaluate the performance of the proposed technique, experiments are conducted which use the dual‐frequency light source comprised of a semiconductor laser, an acousto‐optic modulator, a polarization‐maintaining fiber, etc. As a result, the effectiveness of the technique and its validity are confirmed by the experimental data.
Analysis on impedance characteristics of a photo‐conductive film using distributed parameter circuit model
Authors: Kiwaki Hisatomo , Imada Hiroshi , Ito Masayasu
Published: July 2007

In the measurement of AC impedance of a photo‐conductive layer, the sample is sandwiched between a metal substrate and a transparent conductive surface film. A conductive ring is contacted at the outer edge of this transparent film, forming one electrode. Equivalent parallel resistance and equivalent parallel capacitance representing the bulk properties are calculated from the measured impedance assuming a lumped constant circuit.

However, in this method, an error due to the surface impedance of the transparent conductive layer increases with frequency and reaches nonnegligible value at high frequencies.

In this work, the impedance is theoretically calculated using a distributed constant circuit model and the error contained in the equivalent parallel resistance and parallel capacitance from assuming a lumped constant circuit is clarified.

On the other hand, this theory can also be used for the output calculation of photovoltaic device. The design of short output current, open output voltage, and optimized load is also discussed.
Characteristics of microwave planar transmission lines using superconducting oxide films
Authors: Konaka Tsuneo , Sato Makoto , Asano Hidefumi , Kubo Shugo , Nagai Yasuhiro
Published: July 2007

It is expected that the superior high‐frequency characteristics, such as low loss and low dispersion, of superconducting oxides are applied to microwave circuits. However, low‐loss superconducting oxide films can only be fabricated on limited types of substrate materials using present technologies. Therefore, the dielectric constant, dielectric loss, and thickness of substrate materials place severe limitations on the circuit design and the propagation characteristics.

This paper discusses the attenuation constants, characteristic impedances, and wiring density of three fundamental planar transmission lines, namely, stripline, microstrip line, and coplanar waveguide fabricated on substrate materials MgO and LaAlO3. This discussion is based on the TEM and quasi‐TEM analysis procedures. The thin films with low surface resistances have been fabricated on MgO and LaAlO3. It is concluded that the microstrip line is suitable for fabricating a low‐loss transmission line and the coplanar waveguide on a low dielectric constant substrate is suitable for high‐density wirings.

Also measured were the characteristics of the half‐wave transmission line resonators of these three transmission line configurations, which are made of EuBa2Cu3Ox thin films on an MgO substrate. The attenuation constant of 50 Ω, 50‐μm wide coplanar waveguide is 9.7 × 10−3 Np/m (8.4 × 10−2 dB/m) at 3.9 GHz and 28 K. This value is two orders of magnitude lower than that of the copper transmission line.
Properties of (CdZn)s alloy semiconductor films grown by sputtering
Authors: Yano Mitsuaki , Gyohten Shigekazu , Ochi Hi‐Izu , Kaku Shukichi
Published: July 2007

(CdZn)S alloy semiconductor thin films were deposited by sputtering for the application to solar cells and the deposition conditions were investigated to obtain n‐type low‐resistivity films with high visible light transmission. (CdZn)S thin films with a chemical composition close to stoichiometry were obtained by using a composite sintered target of sulphur‐rich CdS and ZnS.

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

A method of measurement for an elliptic polarization was developed; and, based on the measured results, an optimization was carried out for the black and white representation of the phase plate mode STN‐LCD. It was confirmed that a good black and white representation is possible with real devices. To realize good black and white representation under the operating condition, it is necessary to determine the film characteristics so that black representation is possible for the liquid crystal cells in the off mode with a bias voltage applied. Hence, the following method is used for optimization.

(1) Before the color compensation films are optimized, the applied voltages for the ON and OFF states are determined such that the transmission at the ON state is maximum for optimized films based on the measured results of the elliptic polarization after the transmission through the polarizer/liquid crystal.

(2) For the liquid‐crystal cell for which the determined OFF voltage is applied, the film characteristics are optimized so that black representation is realized. In the usual optimization method, the results of the numerical calculations are used as the characteristics of the liquid crystal cell. The film was optimized for such results.

In the present method, the measured results of the elliptic polarization are used as the characteristics of the liquid crystal cell. Hence, the optimization corresponding to the real device can be carried out. A device was fabricated by the present optimization method. It was confirmed that good black and white optimization corresponding to real devices can be realized with a high transmission and a good color characteristic at the operating condition.
Finite element analysis of electromagnetic field via three‐dimensional hexagonal edge elements
Authors: Yamabuchi Tatsuo , Fujii Shigeo , Murai Tadakuni , Hirose Sadaki , Futagami Tooru , Kagawa Yukio
Published: July 2007

For analyses of problems of three‐dimensional electromagnetic fields by methods of finite elements, formulation based on hexagonal edge elements was used which also was applicable to bodies of arbitrary shape. In previous formulation, a combination of tetrahedral elements was used to construct hexagonal edge elements.

This paper proposes the use of vectorial shape functions in constructing hexagonal edge elements. Their shape functions agreed with the Nedelec‐type elements when a hexagonal body was reduced to a rectangular solid. However, spurious solutions were generated when the body shape deviated from the rectangular solid. Therefore, it is necessary to incorporate Lagrange multipliers as new unknowns in applying elements obtained by the authors to a general three‐dimensional body model. The final discretized equation becomes a simultaneous equation and is not solved by an eigenvalue problem.

As a general model, a circular cylindrical cavity was treated and the resonant frequencies and excitation responses were obtained. For the resonant frequencies, the results obtained herein are compared with those by using the Nedelec‐type tetrahedral elements.
Scattering of electromagnetic plane waves by a chiral slab
Authors: Tanaka Mitsuru , Sueyoshi Hidetomo
Published: July 2007

The scattering characteristics are studied for the plane wave incidence with an arbitrary polarization onto a chiral slab placed on a conducting medium. The analysis is carried out with recognition that the electromagnetic field inside the chiral medium is expressed as a superposition of the right and left circularly polarized waves with different phase velocities.

By using the electric field components of the incident wave, the equations for the reflected field and the transmitted field are derived. The polarization ratio and the Stokes parameters characterizing the polarization states of these fields are provided. For the cases of the incident wave with the horizontal and vertical polarizations, the cross‐ and co‐polarized components of the reflected power and the Stokes parameters of the reflected wave are computed numerically.

The effects of the chirality admittance, the thickness of the slab and the complex permittivity of the conducting medium on the polarization conversion characteristics of the reflected wave are presented. It is considered that the terrestrial vegetation layers exhibit characteristics similar to those of the chiral materials. The results obtained in this paper are believed useful for the analysis of the remote sensing data for vegetation layers.
Equivalent network approach for electron wave propagation and its applications
Authors: Kaji Ryosaku , Hayata Kazuya , Koshiba Masanori
Published: July 2007

With a view to exploring the analysis and design method which provides a good engineering perspective for electron wave devices using the quantum effect phenomena, the electron wave propagation is formulated from a circuit theory viewpoint. In this paper, the electron wave obliquely incident on the heterointerface is treated. First, the quantum mechanical quantities are transformed to the electromagnetic quantities. Then the transmission line equation and the equivalent circuit for the electron wave propagation are derived.

Next, the problem of propagation of the electron wave obliquely incident on the heterointerface is studied in detail by means of its equivalent circuit. The reflection and transmission coefficients and the reflection and transmission probabilities are then calculated. At the same time, the conditions for existence of the Brewster angle and the critical angle for the total reflection are described. Evaluation of the Goos‐Hänchen shift is also carried out. Further, it is shown that the eigenvalue equation for the guided mode in the electron waveguide can easily be derived by the application of the transverse resonance condition well known in circuit theory. The problem of propagation of the electron waves normally incident on the heterointerface such as in the quantum well and the potential barrier are contained in the present formulation as a special case.
A shielded gate static induction transistor: Its characteristics and design
Authors: Yano Koji , Kimura Masakazu , Tanaka Akira , Sukegawa Tokuzo , Kim Chang‐Woo , Motoyama Shin‐Ichi
Published: July 2007

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

A scanning electron microscope (SEM) was utilized for electron beam direct lithography. The scanning electron microscope was modified by installing a blanking unit, thus modifying the deflection coil and condenser coil and adding an external signal line for secondary electron beam detection.

Without modifying the microscope tube and the internal circuit of the SEM, lithography of a layout pattern was made possible. By implementing a lithography system on a Bitmap‐IV CAD system designed for layout pattern designing, both circuit design and lithography were carried out.

The designed layout pattern data were translated to the lithography data described by electron beam direct lithography language (EBDL). Using the algorithm taking into account the characteristic of electron beams in SEM, the minimum pattern dimension of 4 μm with an alignment tolerance of ±2 μm on a chip area of 3.2 mm × 3.2 mm was achieved in patterning circuits in CMOS. LSIs and micromachine layouts. The system was totally automated in operations including positioning.
Static‐noise margin analysis for a scaled‐down CMOS memory cell
Authors: Douseki Takakuni , Mutoh Shin‐Ichiro
Published: July 2007

The noise margins for CMOS SRAM cells composed of scaled‐down MOSFETs are described.

First, an analytical method estimating the noise margins for the CMOS memory cells is proposed. Then scaled‐down MOSFET effects, i.e., the mobility degradation and the parasitic resistances will be considered. How each of these effects changes the noise margins will be studied using analytical equations. As a result, it will be determined that the mobility degradation worsens the read margin by considerably reducing the CMOS inverter logic threshold voltage. It will also be determined that the parasitic resistances associated with the drive transistors degrade the read margin.

Finally, equations are derived for the threshold voltage and cell ratio for a given noise margin. Its effectiveness will be demonstrated for 0.2 μm CMOS memory cells.
Downscaling of floating‐gate EEPROM modules for ASIC applications
Authors: Shiba Kazuyoshi , Kubota Katsuhiko
Published: July 2007

Downscaling methods of electrically erasable programmable ROM (EEPROM) for application‐specific integrated circuit (ASIC) applications based on the double‐poly floating‐gate process were studied. Simple scaling of ASIC and EEPROM modules with the same scaling factor can significantly reduce the time for design and development.

Horizontal scaling of the memory cell with unchanged vertical dimensions does not alter the cell performance because the capacitance coupling ratios are kept constant. Vertical scaling, which further reduces the cell size due to less short channel effects, requires the improvement in the tunnel oxide quality. For this purpose, an improved process also was studied in terms of process temperature and phosphorus concentration in polysilicon gate.
A 256‐K Bi‐CMOS ECL self‐timed RAM using merged Bi‐nMOS gates
Authors: Ohbayashi Shigeki , Shiomi Toru , Sumi Tadashi , Suzuki Kimio , Ohba Atsushi , Honda Hiroki , Ishigaki Yoshiyuki , Hine Shiro , Anami Kenji
Published: July 2007

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

The fundamental research on process technologies for three‐dimensional optoelectronic integrated circuits (OEIC) conducted at Optoelectronics Technology Research Laboratory (OTL) is reviewed. These process technologies consist of atomically controlled epitaxy and the in situ pattern formation of III—V semiconductors.

For atomically controlled epitaxy, various surface analysis techniques are utilized in combination with molecular beam epitaxy (MBE). The in situ pattern formation is performed using a thin oxidized layer of GaAs in an ultrahigh vacuum (UHV) multichamber system. This patterning is based on the in situ electron‐beam (EB) induced C12 etching of the photooxidized GaAs layer.

On the basis of the foregoing result, the process technologies for the future three‐dimensional OEIC are discussed.
Optimized design of stepped impedance dielectric coaxial resonators via tm mode analysis
Authors: Toki Masahiro , Arai Hiroyuki , Makimoto Mitsuo
Published: July 2007

The analysis of resonant electrical length and unloaded Q for the miniaturized dielectric coaxial stepped impedance resonator (SIR), used often in diplexers of portable radio telephones, is performed usually with the assumption of only fundamental TEM mode.

In this paper, finite element TM mode analysis is performed and optimum structure design of SIR is shown which makes the ratio of unloaded Q to the resonant electrical length kL (Q/kL) maximum. As a result of analysis, it is found that the location of the step to minimize resonant electrical length is about 40 percent of the axial length from the open end of SIR.

The ratio of unloaded Q and resonant electrical length varies rather slowly when any of the structure parameters are varied around the optimum value. This fact shows that no high precision in the design of structure parameters is required. Moreover, providing taper at the step position in SIR, the resonant electrical length can be increased by a few percent.

It is shown also that the present analysis is useful for the design of square‐shaped SIR which is a simple and practically used structure for diplexers.
Boundary element analysis of electromagnetic fields in cylindrical structures
Authors: Matsuhara Masanori , Kamura Masahiro , Maruta Akihiro
Published: July 2007

A novel combined integral equation, which is adaptable to the analysis of a general electromagnetic field in a cylindrical structure, is proposed. The unknown quantities of the equation are the transverse electromagnetic field components and the equation is analyzed numerically by the boundary element method. The combined integral equation does not have the difficulty arising from the nonphysical solutions which have been troubled conventionally. In addition, the integral equation does not contain spatial derivatives of the unknown quantities. The coefficient matrix of the matrix equation obtained by the application of the boundary element method is square and is hence suitable for numerical analysis.

In this paper, first the combined integral equation for unknown transverse electromagnetic field components are derived. The uniqueness of the solution is proven. Further, the integral equation is analyzed numerically for actual examples by the boundary element method so that the validity and effectiveness of the method are verified.
A method for the design of dielectric multilayer bandpass filters
Authors: Miyauchi Kazuhiro , Wakabayashi Isamu
Published: July 2007

A design method of a dielectric multilayer bandpass filter for optical‐communication is proposed, and its feasibility is demonstrated for an example of the design.

The design procedure is to replace each resonator in a specified LC bandpass filter by a corresponding dielectric multilayer resonator. This LC bandpass filter is obtained from an LC lowpass prototype through a frequency transformation. New structures of a dielectric multilayer resonator are proposed, and the equations necessary for the design are derived. A method to correct a design error due to excess phase also is discussed.

With the present design method, an arbitrary polynomial characteristic (Butterworth, Chebyshev, and Bessel, etc.) can be realized as a dielectric multilayer bandpass filter. A good agreement is found between the designed and actual performance for a narrowband bandpass filter.
A liquid sensor based on a shear horizontal saw device
Authors: Kondoh Jun , Shiokawa Showko
Published: July 2007

The surface acoustic wave (SAW) changes its propagation characteristic if the region above the propagation surface is altered. This phenomenon can be used for realization of an SAW sensor. The Rayleigh mode known as a general SAW can be used as a gas phase sensor. If, however, the propagation surface is loaded with liquid, a longitudinal wave is radiated into the liquid and the Rayleigh wave decays. Hence, this wave cannot be used for a liquid sensor.

To realize a liquid sensor, the SH mode must be used in which the particle displacement is normal to the propagation direction and parallel to the propagation surface. It has been reported that the SAWs propagating on piezoelectric crystals such as 36° rotated Y‐cut X propagation LiTaO3and X‐cut 150° propagation LiTaO3are SH‐mode SAWs (SH‐SAW).

In this paper, it is found theoretically and experimentally that the shear horizontal‐ (SH‐) SAW devices using these piezoelectric crystal cannot only detect the mechanical effects such as the viscosity of the liquid and the mass loading in the liquid but also the electrical effects such as the permittivity and conductivity of the liquid. By way of comparison with other liquid sensors using high‐frequency ultrasonic devices, the characteristics of the SH‐SAW sensors are clarified.
Films of the intermetallic compound CuTi2 and their applications in Cu/CuTi2/Si contact structures
Authors: Yoshimoto Ken'ichi , Sasaki Takahiro , Sasaki Katsutaka , Noya Atsushi
Published: July 2007

To prepare constituent materials applicable to a Cu metallization technology of Si‐LSI, the preparation conditions of Cu‐Ti intermetallic compound films have been examined and the thermal stability of the Cu/CuTi2/Si contact structure has been studied using CuTi2 compound films as a diffusion barrier. As a result, a stoichiometric intermetallic compound film of CuTi2 was prepared successfully at a substrate temperature of 300°C by dc sputtering using a composite target with an area ratio of Cu : Ti = 51 : 49.

From the study on the CuTi2/Si contact structure, it was revealed that the CuTi2 phase was stable up to 500°C and a thin interface layer of Ti silicide was formed at the interface of CuTi2/Si but the excess diffusion and/or reaction have not been observed. Ti silicide layer formed at the interface is believed to be effective for low contact resistance. To examine whether or not CuTi2 films are suitable for Cu metallization technology, the thermal stability of Cu/CuTi2/Si contact structure was examined. It was found that the structure is successfully stable up to 500°C and is useful for Cu metallization technology. The reason is believed to be as follows: the interface of Cu/CuTi2 is in the chemical equilibrium state and CuTi2 itself is a stable compound phase at high temperatures in the Cu‐Ti alloy system.
Preparation of sintered acicular ba‐ferrite particles and determination of their magnetic properties
Authors: Fujita Minoru , Ueda Tetsuya , Hiratsuka Nobuyuki
Published: July 2007

Acicular barium ferrite fine particles were successfully fabricated by sintering a mixture of Ba(OH)2 8H2O and acicular α‐FeOOH at a temperature of 500 to 1200°C for 1 hr in air and then rapidly cooled down. For sintering temperatures below 800°C, no magnetization was found. However, with increasing temperature beyond 900°C, the magnetization increased significantly in accordance with the formation of hexagonal barium ferrite. The coercivity increased for sintering at 900 to 1000°C and then decreased at 1100 to 1200°C where a significant grain growth was observed.

Acicular barium ferrite fine particles with an atomic ratio 1 : 10 between Ba and Fe ions sintered at 1000°C were found to consist of particles of about 0.7‐μm length and an aspect ratio of about 7, which exhibit the magnetization and coercivity of 61 emu/g (61 A.m2/kg) and 3990 Oe (317.5 kA/m), respectively. Coated‐films were fabricated by dispersing barium ferrite fine particles thus obtained in resin solution, which were then coated onto polyester films.

The squareness ratio of nonoriented films for the vertical field direction is larger than that for acicular barium ferrite fine particles, and the films were more easily magnetized along the film normal. When the magnetic field was applied along the film normal at the time of drying the film, the sample can easily be magnetized also. This result seems to indicate the possibility of barium ferrite‐coated films for vertical magnetic recording media. The major axis of acicular barium ferrite fine particles was found to be in the film plane and the easy axis for magnetization is along the film normal.
Complex eigenstates of an electron in quantum box structures in the presence of an external electric field
Authors: Tsuji Yasuhidé , Hayata Kazuya , Koshiba Masanori
Published: July 2007

As a useful approach to analyze the eigenstate of electrons inside a quantum box, the weighted potential method (WPM), already proven to be valid in a one‐dimensional system (wire structure), is applied to the zero‐dimensional one (box structure). The formulation and analysis were made for the quantum box structure of a finite potential barrier height in the presence of an applied electric field.

The analysis, which takes into account the tunneling effect of electrons through the barrier when the electric field becomes strong, was carried out for the eigenstates. The method allows us to estimate the electron lifetime. A discussion also was made for an actual structure in which the effective mass of electrons is changed from a quantum well to a barrier region. The change in the eigenenergy was found to become more significant when increasing the number of the quantized direction.
Performance improvement in digital magnetic recording by write and read equalization
Authors: Okamoto Yoshihiro , Osawa Hisashi , Takigawa Kiyoshi , Ono Kazuo
Published: July 2007

DC‐freeing of write waveform is an important technique in digital magnetic recording. In this paper, it is achieved by using write equalization, which is one of the dc‐freeing methods, and on the read side, read equalization, which not only can reduce high‐frequency noise but also has little degradation of eye opening. A new write and read equalization method developed by investigating it from a synthetic viewpoint is proposed along with a signal detection method which brings out the best in the equalization method.

First, it is shown that it is possible to dc‐free by the write equalization and then a read equalization and signal detection method is described which enables high signal‐to‐noise ratio (SNR) to be obtained by combining with the write equalization. Furthermore, it is clarified by computer simulation that our proposed system shows an excellent error rate performance compared with the combination of NRZ recording code and integrated detection, which is well known for its good performance so far.
A current‐mode multivalued logic circuit based on by Bi‐CMOS transistors
Authors: Ueno Fumio , Inoue Takahiro , Sasaki Mamoru , Taniguchi Kazutaka , Yamashita Toshitsugu
Published: July 2007

This paper proposes a Bi‐CMOS current‐mode multivalued logic circuit enabling high‐accuracy computation, high‐speed computation, and high integration. In conventional current‐mode multivalued logic circuits using I2L and CMOS configurations, the realization of high‐radix multivalued logic circuits was difficult due to the calculation errors in the basic circuits, such as a current mirror or subthreshold detector.

As a result of simulations of the basic circuits proposed in this paper using an electronic circuit analysis program SPICE2, a 16‐valued logic circuit has been shown to be possible with 0.8‐m̈m process even considering the variation in device parameters. As an application of these basic circuits, MIN, MAX circuits, and literal circuit are shown. These circuits have a simple configuration and high speed.
Selective movpe growth and its application to semiconductor photonic integrated circuits
Authors: Sasaki Tatsuya , Yamaguchi Masayuki , Kato Tomoaki , Sakata Yasutaka , Asano Hideki , Kitamura Mitsuhiro , Mito Ikuo
Published: July 2007

Considerable research and development have been done on semiconductor photonic integrated circuits in which various components such as a laser diode and other photonic devices were integrated.

In this paper, a 1.55‐μm band wavelength division multiplexing (WDM) integrated light source for optical communication is developed and the results of the evaluation are described. Four‐channel laser sources were fabricated by integrating tunable semiconductor lasers and semiconductor optical modulators plus multiplexers, and the possibility of using a 2.5‐Gbit/s high‐density WDM optical transmission system is discussed.

After analyzing the problems encountered in the fabrication of these photonic integrated components, the development of a bandgap energy‐controlling technique of quantum well structure using the selective metal oxide vapor‐phase epitaxial (MOVPE) growth, which is a better fabrication technique, is described. By using this technique, the difficult process of combining the waveguide with a different bandgap energy can be accomplished only by a one‐step crystal growing. This simplifies the components fabrication, and a high‐coupling efficiency of the waveguide between the integrated elements can be obtained.

As an application example, the integrated light source was fabricated by integrating a tunable laser, distributed feedback (DFB) laser, and semiconductor optical modulator. Then the tunable characteristic and the extinction characteristic were verified. This simplifies the fabrication method of the previously difficult method of semiconductor photonic integrated circuits and clarifies the possibility of developing a high‐density integrated element.
Oscillation wavelength shift of GaAlAs laser diodes in a magnetic field
Authors: Sato Takashi , Kawashima Hidetoshi , Nakamura Toshio , Ohkawa Masashi , Maruyama Takeo , Shimba Minoru
Published: July 2007

The wavelength shift of laser diodes in a magnetic field has been known for a long time. However, most of the studies have been performed at very low temperatures in a strong magnetic field. An experiment is carried out using laser diodes which oscillate at room temperature and found that the wavelength shift changed significantly, being sensitive to an inner structure. Further, the wavelength shift occurred depending on a magnetic field direction.

Previously, the wavelength shift was explained on the basis of the Landau level at very low temperatures in a strong magnetic field. However, such Landau levels are not formed in a relatively weak magnetic field at room temperature; and, thus, the present result cannot be accounted for by the existing theories.

This paper describes the experimental results of various types of GaAlAs laser diodes and discusses the mechanism of the wavelength shift and the wavelength control.
Locking Characteristics of Intermodal Injection locking for a Semiconductor Laser
Authors: Iida Yukio , Miyajima Takeshi , Morita Masanobu
Published: July 2007

A theoretical and experimental investigation is presented of injection locking on a semiconductor laser by coupling into nonlasing Fabry‐Perot modes.

The very interesting behavior of intermodal injection locking is shown by the investigation of detailed locking characteristics. The analysis adopts a formulation similar to that of Lang in the injected mode, and the free‐running mode is expressed by the rate equation for the photon density.

The theoretical analysis takes into account the dependence of the refractive index and of the peak gain wavelength on the carrier density and the spectral dependence of the gain function.

The experimental results can be explained well qualitatively by the theoretical results. The locking range is located approximately around the center of detuning for the injection locking to a nonlasing mode as far as 18 mode spacings away from the free‐running mode. At the same time, the locking range is shifted toward the lower‐frequency side of detuning and has a symmetric tuning characteristic for that of several mode spacings as in the ordinary injection locking. The former is very useful in application.
A Femtosecond Erbium‐Doped Fiber Laser with a Nonlinear Amplifying Loop Mirror Pumped by Laser Diodes and with Repetition Rate Control of Its Output Pulses
Authors: Yoshida Eiji , Kimura Yasuo , Nakazawa Masataka
Published: July 2007

An erbium‐doped fiber laser with a nonlinear amplifying loop mirror pumped by 1.48‐μm laser diodes was fabricated. A 290‐femtosecond (fs) short pulse was obtained successfully from this laser. The oscillation wavelength was 1.56 μm and the output peak power was as high as 16 W when the pump power was 20 mW. The oscillation threshold was about 50 mW.

However, once the laser started oscillation, it continued to oscillate even when the pump power was 10 mW. The repetition rate of the output pulses changed randomly from 5 MHz (fundamental repetition rate) to 2 GHz and could not be controlled. However, using a subring cavity with a length which is 1/n that of the main cavity (n is an integer), a constant pulse repetition rate of 125 MHz was obtained.