bluuebunny/crossref_metadata_2025 huggingface dataset:
Superior Generalization Capability of Hardware-Learing Algorithm Developed for Self-Learning Neuron-MOS Neural Networks
Authors: Kondo Shuhei , Shibata Tadashi , Tadahiro Ohmi Tadahiro Ohmi
Published: October 2002

We have investigated the learning performance of the hardware backpropagation (HBP) algorithm, a hardware-oriented learning algorithm developed for the self-learning architecture of neural networks constructed using neuron MOS (metal-oxide-semiconductor) transistors. The solution to finding a mirror symmetry axis in a 4×4 binary pixel array was tested by computer simulation based on the HBP algorithm. Despite the inherent restrictions imposed on the hardware-learning algorithm, HBP exhibits equivalent learning performance to that of the original backpropagation (BP) algorithm when all the pertinent parameters are optimized. Very importantly, we have found that HBP has a superior generalization capability over BP; namely, HBP exhibits higher performance in solving problems that the network has not yet learnt.
Photoellipsometric Determination of Built-In Electric Field in δ-Doped GaAs
Authors: Xiong Yi-Ming , Wong Cheong Chee , Tadashi Saitoh Tadashi Saitoh
Published: October 2002

In this study, photoellipsometry, a contactless optical method sensitive to surface and interface built-in electric fields in semiconductor structures, was employed to study δ-doped GaAs. Three δ-doped samples, each containing an undoped GaAs cap layer of different thickness, were measured. The objective was to determine the built-in field strength in the cap layer of each chosen sample. Data analysis was performed using the Franz-Keldysh theory, in which the effect of broadening and the contributions from both heavy and light holes were included. Good agreement was found between the measured and calculated spectra for all the samples studied, indicating that the model calculations were adequate. In addition, the linear relationship observed between the build-in field and the reciprocal of the cap layer thickness suggests that the surface Fermi level was pinned at a fixed position for the samples measured.
Effects of Low Temprature Grown GaAs Layer on Compositional Disordering of AlGaAs/GaAs Superlattices
Authors: Tsang Jian-Shihn , Lee Chien-Ping , Fan Jenn-Chyuan , Lee Shing-Horng , Kuang-Lung Tsai Kuang-Lung Tsai
Published: October 2002

Effects of thickness and position of the low-temperature-grown GaAs (LT-GaAs) layer on the compositional disordering of AlGaAs/GaAs superlattice have been studied. Samples with a top LT-GaAs layer or a bottom LT-GaAs layer have been studied with various annealing conditions. It was found that the LT-GaAs layer grown on top of the superlattice is more effective in causing disordering than the LT-GaAs layer grown at the bottom. The amount of disordering increases with the thickness of the LT-GaAs layer. A selective disordering process has been developed using a patterned LT-GaAs cap layer. This disordering technique is very simple and can be easily applied to device fabrication.
Metalorganic Vapor Phase Epitaxy Growth of Be-Doped InP Using Bismethylcyclopentadienyl-Berylium
Authors: Kimura Tatsuya , Ishida Takao , Sonoda Takuji , Mihashi Yutaka , Takamiya Saburo , Sigeru Mitsui Sigeru Mitsui
Published: October 2002

We have applied Be as a p-type dopant for the InP layer grown by metalorganic vapor phase epitaxy. Very good control of Be doping has been obtained with bismethylcyclopentadienyl-beryllium. Carrier concentration as high as 2×1018 cm-3 has been achieved with excellent surface morphology. The photoluminescence peak intensity of the samples was comparable to that of Zn-doped InP.
It has been found that Be concentration drops abruptly at the InGaAsP/InP interface in an undoped InGaAsP/Be-doped InP structure, and there is no significant Be diffusion into undoped InGaAsP.
This indicates that Be is the most promising p-type dopant alternative to Zn, which has a large diffusion coefficient in the InP layer, for InGaAsP/InP laser diodes.
Cross-Sectional Observation in (103)-Oriented YBa2Cu3Ox/SrTiO3/(013)-Oriented YBa2Cu3Ox Tunnel Junction
Authors: Matsui Toshiyuki , Suzuki Takeshi , Kimura Hiroshi , Yamaguchi Dabide , Ueda Atushi , Hiroshi Kamijo Hiroshi Kamijo
Published: October 2002

Cross-sectional observation has been performed in a (103)-oriented YBa2Cu3O

x

(YBCO)/ SrTiO3 (STO)/(013)-oriented YBCO tunnel junction. Transmission electron microscope (TEM) image revealed that dominant structures of the top and bottom YBCO layers are formed by (100)-, (010)- and (001)-planes at the YBCO/STO interfaces and that amorphouslike layers exist at both the top YBCO/STO and STO/bottom YBCO interfaces.
Scanning Tunneling Microscopy Study of Ultrathin Fe Films Grown on GaAs(001) Surface
Authors: Takeshita Hiroto , Akinaga Hiroyuki , Ehinger Markus , Suzuki Yoshishige , Ando Koji , Tanaka Kazunobu
Published: October 2002

Scanning tunneling microscopy (STM) studies have been carried out to clarify the initial growth mechanisms of ultrathin Fe films on GaAs(001) substrates. For the submonolayer growth of Fe at room temperature (RT), the STM image showed many small clusters on the flat terraces of the c(4×4) reconstructed GaAs(001) surface. The typical size of the clusters seen in the STM image is about 15 Å which is nearly equal to the size of the basis structure of the c(4×4) reconstruction. It is also discussed that the formation of the clusters depends on the reconstruction of the GaAs(001) surface.
Surface Morphology of (NH4)2Sx-Treated GaAs(100) Investigated by Scanning Tunneling Microscopy
Authors: Ha Jeong Sook , Kim Sung-Bock , Park Seong-Ju , El-Hang Lee El-Hang Lee
Published: October 2002

The surface morphology of n-GaAs(100) after etching with sulfuric acid and sulfur passivation with ammonium sulfide ( (NH4)2S

x

) solution were systematically investigated using a scanning tunneling microscope (STM) under ambient conditions. Depending on the etching and passivation conditions, the surface roughness was observed to vary widely. The effects of water rinse, HCl treatment, and passivation time on the surface morphology were studied through etching and passivation reactions. In particular, a very flat surface with a sub-nanometer surface undulation was obtained after sulfur passivation for 20 min without postetch water rinse. These studies enabled a better understanding of the effects of the routinely used etching and passivation reactions on the surface morphology of GaAs(100) in nanometer scale and showed that GaAs can be used as a substrate for nanofabrication.
Characterization of P- and N-Type Impurity Diffusions in GaAs from Doped Silica Films
Authors: Okamoto Kazuya , Yamada Atsushi , Shimogaki Yukihiro , Nakano Yoshiaki , Tada Kunio
Published: October 2002

Characteristics of p- and n-type open-tube diffusion into GaAs using zinc (Zn)- and tin (Sn)-doped spin-on silica films are investigated. This paper first describes the difference of carrier concentration profiles between both types of diffusion, and then interstitial-substitutional diffusion mechanisms are proposed. Next, the surface condition after diffusion is observed by SEM and AFM. In the case of using highly doped films, abundant surface defects are detected. However, the surface condition is greatly improved by using low-doped ones. Also, the two micrographs are in good agreement. Finally, lateral diffusion length and electrical characteristics of diffused layers are discussed. It is concluded that this diffusion method is quite simple and useful for the fabrication of III-V compound semiconductor devices.
Depletion Characteristics of Direct Schottky Contacts to Quantum Wells Formed by In Situ Selective Electrochemical Process
Authors: Hashizume Tamotsu , Okada Hiroshi , Wu Nan-Jan , Hasegawa Hideki
Published: October 2002

Depletion properties of direct Schottky/quantum well (QW) contacts formed by the in situ selective electro-chemical process were systematically characterized by the C-V and electron-beam-induced current (EBIC) techniques. The EBIC images clearly showed that the barrier exists at the edge of the QW layer. It was found that the capacitance of the Schottky/QW contact depends linearly on ln
{1/(V
bi-V)}, where the V
bi is built-in voltage, and that the depletion width obtained from the EBIC signal is proportional to the applied voltage. These results demonstrate that well-behaved depletion characteristics of the Schottky/QW systems can be realized.
New Planar Two-Mode Channel Field-Effect Transistor Suitable for L-Band Microwave Monolithic Integrated Circuits with RF Transmission and Reception Blocks Operating at Vdd≤ 2 V
Authors: Sawada Minoru , Fujii Emi , Matsushita Shigeharu , Terada Satoshi , Inoue Daijiro , Nakamoto Hiroyuki , Yasoo Harada Yasoo Harada
Published: October 2002

A new planar-type two-mode channel field-effect transistor (P-TMT) for L-band microwave monolithic integrated circuits (MMICs) with RF transmission and reception blocks operating at a very low supplied voltage (V
dd≤2 V) for use in the 1.9-GHz-band personal handy phone system (PHS) has been developed. By simply changing the gate width (W
g), P-TMTs with W
g=400 µ m and W
g=2600 µ m were fabricated for low-noise and high-power applications, respectively. At the drain voltage (V
ds) of 2 V, a minimum noise figure (F
min) of 0.65 dB, an associated gain (G
a) of 17.6 dB at drain current (I
ds) of 3 mA, and a 1 dB gain compression (P
o(1 dB)) of 22.8 dBm at I
ds=300 mA were obtained. Moreover, at V
ds=1.5 V, F
min of 0.65 dB, G
a of 16.9 dB at I
ds=3 mA, and P
o(1 dB) of 20.9 dBm at I
ds=350 mA were obtained.
Effects of Sulfide Passivation on the Performance of GaAs MISFETs with Photo-CVD Grown P3N5 Gate Insulators
Authors: Jeong Yoon-Ha , Choi Ki-Hwan , Jo Seong-Kue , Bongkoo Kang Bongkoo Kang
Published: October 2002

Accumulation-mode and depletion-mode GaAs metal-insulator-semiconductor field-effect transistors (MISEETs), with sulfur-treatment and a photochemical vapor-deposited- P3N5 gate insulator, have been successfully fabricated. The devices have good linearity, low hysteresis in current-voltage characteristics, and the instability of the current less than 22 percent for the period of 1.0-1.0×104 s. The effective electron mobility and extrinsic transconductance of the FETs at room temperature are about 1300 cm2/V·s and 1.41 mS/mm for the accumulation-mode, and about 4500 cm2/V·s and 4 mS/mm for the depletion-mode, respectively. Capacitance-voltage (C-V) characteristics and Auger electron spectroscopy (AES) analysis for different sulfur-treatment conditions are discussed. The atomic concentration ratios of sulfur and oxygen to arsenide on GaAs surfaces and GaAs metal-insulator-semiconductor (MIS) interface properties are critically dependent on sulfur pretreatment conditions, and the optimum sulfur-treatment temperature is determined to be about 40° C. The minimum density of interface trap states for an Al/P3N5/GaAs MIS diode with the optimized surface treatment is about 4.3×1010 cm-2 eV-1.
Electroluminescence of Ballistic and Phonon Emitting Electrons in the p-Type Base of AlGaAs/GaAs HBT Structures
Authors: Fukai Yoshino K. , Furuta Tomofumi , Tadao Ishibashi Tadao Ishibashi
Published: October 2002

We investigate the transport behavior of high-energy ballistic electrons in the p-type region using Npn-Al

x

Ga1-
x

As/GaAs heterojunction bipolar transistors (HBT) with an abrupt emitter-base heterojunction. The observed electroluminescence spectra from the base region show several high-energy peaks that are associated with ballistic electrons and with LO-phonon emissions. By varying the emitter-collector voltage, the neutral base width can be modulated, leading to a change in spatial electron distributions and thus determining the mean free paths of ballistic electrons.
Open-Base Multi-Emitter HBTs with Increased Logic Functions
Authors: Imamura Kenichi , Takatsu Motomu , Mori Toshihiko , Muto Shunichi , Naoki Yokoyama Naoki Yokoyama
Published: October 2002

We have designed and tested a new functional device, an open-base multi-emitter heterojunction bipolar transistor (ME-HBT) which operates at room temperature. In this paper, we discuss the dependence of emitter doping concentration on the DC characteristcs of the ME-HBTs. The collector current turn-on volatge decreases to 0.7 V with an emitter doping of 1×1019 cm-3.
  Using a ME-HBT, we constructed a 3-input AND/NOR gate, and confirmed that operation at room temperature was normal using an operating voltage of 2 V.
We also discuss a problem with this ME-HBT circuit and offer a possible solution. We believe our approoach will prove useful for various ICs due to its simplicity and functionality.
Effects of a Compositionally-Graded InxGa1-xAs Base in Abrupt-Emitter InP/InGaAs Heterojunction Bipolar Transistors
Authors: Kurishima Kenji , Nakajima Hiroki , Yamahata Shoji , Kobayashi Takashi , Yutaka Matsuoka Yutaka Matsuoka
Published: October 2002

A compositionally-graded In

x

Ga1-
x

As base is experimentally shown to improve electron transport properties in abrupt-emitter InP/InGaAs heterojunction bipolar transistors (HBTs). The built-in field in the base of 6 kV/cm enables a more than 50% improvement in current gains, compared to a uniform-base structure. The peak current-gain cutoff frequency f
T for the graded-base HBT is 143 GHz versus 121 GHz for the uniform-base HBT. It is also shown that the graded-base structure is effective in suppressing the space charge in the vicinity of the base-collector junction. The built-in field in the base accelerates low-speed energy-relaxed electrons and thereby increases the velocity of electrons injected into the collector. The minimized base widening effect, combined with low base resistance, yields a maximum oscillation frequency f
max over 200 GHz even at a collector bias voltage V
CE as low as 1 V.
Numerical Simulation on the Device Structure of GaAs Floated Electron Channel Field-Effect Transistor
Authors: Lee Yoon-Jong , Kim Chang-Tae , Hong Song-Cheol , Kwon Young-Se , Yoon Hee-Koo , Kye-Whan Oh Kye-Whan Oh
Published: October 2002

In order to characterize the performance and design the optimal structure of the GaAs floated electron channel field-effect transistor (FECFET), we have carried out two-dimensional numerical simulation with varying the values of the key structure parameters of the FECFET.
In the simulation, the uniform distribution of surface state charges on triangular void wall and the electron saturation velocity as a function of gate length are taken into account. It is shown from the simulation that the GaAs FECFET has an effective channel length of about 0.5 µ m and the vertical distance between the top vertex of void and the Ohmic layer front affects the channel length. When the gate-length-dependent saturation velocity is considered, the simulated current-gain cut-off frequency of the FECFET is linearly proportional to the reciprocal of the metallized gate length. When the gate is misaligned toward the drain direction, the transconductance values of the FECFET more abruptly decrease than in the case of misalignment toward the source direction.
Buried-Channel WNx/W Self-Aligned GaAs MESFET Process with Selectively Implanted Channel and Undoped Epitaxial Surface Layers for MMIC Applications
Authors: Nishihori Kazuya , Kitaura Yoshiaki , Nagaoka Masami , Tanabe Yoshikazu , Mihara Masakatsu , Yoshimura Misao , Hirose Mayumi , Naotaka Uchitomi Naotaka Uchitomi
Published: October 2002

The combined process of epitaxy and ion implantation has been developed in the fabrication of a buried-channel WN

x

/W self-aligned GaAs metal-semiconductor field-effect transistor (MESFET). This MESFET comprises an ion-implanted channel and an undoped GaAs epitaxial surface layer. The ion-implantation technique leads to an IC-oriented process and the epitaxial technique to a buried channel structure. Both ease of isolation and enhanced breakdown voltage were attained, promising monolithic microwave integrated circuits (MMICs) for L-band digital mobile communication systems.
Fabrication and Evaluation of Three-Dimensional Optically Coupled Common Memory
Authors: Miyake Kouji , Namba Tohru , Hashimoto Kenji , Sakaue Hiroyuki , Miyazaki Seiichi , Horiike Yasuhiro , Yokoyama Shin , Koyanagi Mitsumasa , Masataka Hirose Masataka Hirose
Published: October 2002

A three-dimensional optically coupled common memory (3D-OCC memory) test chip, on which GaAs LEDs are integrated using the microbonding technique, has been fabricated using a 2 µ m complementary metal-oxide-semiconductor (CMOS) technology. Static memory cell circuits with photodiodes were formed on the chip. Optical writing and electrical reading operations of the 3D-OCC memory test chip have been demonstrated.
Wavelength Filtering Operation in Absorptive-Grating Gain-Coupled Distributed-Feedback MQW Lasers
Authors: Otani Tomohiro , Sudoh Tsurugi K. , Nakano Yoshiaki , Kunio Tada Kunio Tada
Published: October 2002

We have investigated transmission-type wavelength filtering operation in semiconductor distributed feedback (DFB) lasers incorporating gain coupling (GC). This GC DFB laser filter has an inherent single pass band which is not much affected by the facet reflection or phases. Our analysis has predicted larger parasitic-band suppression and narrower pass bandwidth than conventional DFB laser filters. Next, we have demonstrated optical wavelength filtering operation in an actual GC DFB multiple quantum well (MQW) laser for the first time. We have confirmed the single transmission pass band in this type of DFB laser filter, and obtained useful characteristics such as 0.02 nm transmission bandwidth, 14 dB discrimination, zero insertion loss, and -12 dBm saturation power.
GaInAs/GaAs Micro-Arc Ring Semiconductor Laser
Authors: Mitsugi Satoshi , Koyama Fumio , Kato Junnichi , Matsutani Akihiro , Mukaihara Toshikazu , Kenichi Iga Kenichi Iga
Published: October 2002

We have proposed a micro-arc-ring-cavity (MARC) laser, which consists of an etched concave reflector and two plane reflectors. The resonant optical wave can be tightly confined by total internal reflection in the lateral microcavity. We present the theoretical basis of a MARC laser, focusing on the design issue for low threshold operation, transverse mode control and light output coupling. We also present some experimental lasing characteristics of 0.98 µ m GaInAs/GaAs strained quantum well MARC lasers fabricated by direct electron beam lithography and reactive ion beam etching.
Formation of High-Contrast Periodic Corrugations by Optimizing Optical Parameters of Photoresists in 325 nm Laser Holographic Exposure
Authors: Okamoto Kazuya , Nakano Yoshiaki , Tada Kunio
Published: October 2002

Formation of high-contrast periodic corrugations by means of laser holographic exposure is investigated. This paper first describes optical parameters of several positive-acting photoresists extracted from UV transmission spectra analysis. Conventional g-line photoresists have high values of these parameters and might not be suitable for this purpose. Next, shapes of periodic corrugations are simulated in three typical g-line photoresists using other optical parameters as well as developing process properties. Both s- and p-polarized plane-wave differences and substrate dependence are also considered. As a result, the shapes are found to depend mainly on γ values of the photoresists. High-contrast corrugations and a highly reproducible process are expected if an optimum photoresist is selected. Finally, we fabricate high-contrast periodic corrugations with a period of 255 nm, and the result is in good agreement with the theoretical estimation.
Thermally Enhanced Co-Tunneling of Single Electrons in a Si Quantum Dot at 4.2 K
Authors: Matsuoka Hideyuki , Shin'ichiro Kimura Shin'ichiro Kimura
Published: October 2002

Transport properties of a Si quantum dot at 4.2 K have been studied. A quantum dot is realized in the inversion layer of a Si metal-oxide-semiconductor field-effect-transistor (Si-MOSFET) with a dual-gate structure by introducing controllable tunnel barriers in the narrow channel. Periodic current oscillations due to the single-electron charging effect have been observed. With increasing tunnel barrier heights, Coulomb gaps appear in the I-V characteristics. Furthermore, leakage current in the Coulomb blockade regime varies linearly with bias voltage, which is quantitatively described in terms of the inelastic co-tunneling theory at finite temperatures.
Hot Electron Ballistic Transport in Small Four-Terminal n-AlGaAs/InGaAs/GaAs Structures
Authors: Satoshi Sasaki Satoshi Sasaki , Yoshiro Hirayama Yoshiro Hirayama , Seigo Tarucha Seigo Tarucha
Published: October 2002

We have studied hot electron ballistic transport in small four-terminal structures fabricated by Ga focused-ion-beam implantation from AlGaAs/InGaAs/GaAs modulation doped material. We have determined the characteristics of negative bend resistance as a function of hot electron energy by analyzing the magneto-resistance data. We have found that the ballistic nature of hot electrons is progressively lost when the excess energy of hot electrons exceeds LO-phonon energy, although the effect is smaller than in structures fabricated from conventional AlGaAs/GaAs modulation doped material due to the difference in the electron-phonon coupling strength. We have also found that the collimation effect, which is related to the geometry of the electron emitter, is preserved for hot ballistic electrons.
Photoinduced Hole Tunneling in Resonant Tunneling Diodes
Authors: Chu Hye Yong , Park Pyong Woon , Han Seon Gyu , El-Hang Lee El-Hang Lee
Published: October 2002

The resonant tunneling of photoinduced holes in GaAs/AlAs n+-i-n+ double barrier quantum well structures has been successfully observed in photocurrent measurements. We have found that the accumulation of photogenerated holes in the electron depletion region severely modify the electrostatic potential over the double barrier structure. As a result, the current-voltage curves are shifted to lower voltages. With the depletion approximation, the observed hole tunneling is identified as the resonant tunneling through the first light hole state in the quantum well of valence band.
Quantum-Confined Stark Shift Due to Piezoelectric Effect in InGaAs/GaAs Quantum Wells Grown on (111)A GaAs
Authors: Vaccaro Pablo O. , Tominaga Kouji , Hosoda Makoto , Fujita Kazuhisa , Toshihide Watanabe Toshihide Watanabe
Published: October 2002

In0.2Ga0.8As/GaAs strained quantum wells (SQWs) were grown on GaAs (111)A just-oriented, 1° off and 5° off toward [110]- and [001]-oriented substrates. Dependence of strain relaxation on substrate orientation was studied by photoluminescence (PL) spectroscopy. Samples grown on GaAs (111)A 5° off toward [001]-oriented substrates showed the best optical characteristics and this substrate orientation was chosen for making p-i-n diodes. The PL spectrum shows the influence of a built-in electric field due to the piezoelectric effect. The blueshift of PL peaks with applied bias was demonstrated in a p-i-n structure. The PL peak corresponding to a 10 nm SQW blueshifted as much as 24 meV with only 1.2 V applied reverse bias.
Application of STM Nanometer-Size Oxidation Process to Planar-Type MIM Diode
Authors: Matsumoto Kazuhiko , Takahashi Shu , Ishii Masami , Hoshi Masakatsu , Kurokawa Akira , Ichimura Shingo , Atsushi Ando Atsushi Ando
Published: October 2002

Ultra fine oxidized titanium (Ti) lines 18 nm wide and 3 nm high have been formed on the surface of a 4 nm Ti layer on a SiO2/Si substrate using the scanning tunneling microscope [STM] tip as a selective anodization electrode. The dependence of the size of the oxidized titanium line on the various parameters is investigated. The formed oxidized titanium line has resistivity of 2×104 ohm cm, which is a value seven orders of magnitude higher than that of the deposited Ti layer. The oxidized Ti line is used in the planar type metal-insulator-metal [MIM] diode, and works as an energy barrier for the electron. The energy barrier height of the oxidized Ti line is found to be δE
g=0.25 eV.
Thermal Stability of Second-Order Nonlinearity in Poled Polymeric Films
Authors: Huang Jung Y. , Liao Chueng L. , Whang Wha T. , Chang Chi J.
Published: October 2002

The thermal stability of the poled polar order of nonlinear optical (NLO) chromophores covalently appended to the main chain of polymeric films was studied by measuring the generated optical second-harmonic signal over a wide range of temperatures. Our results provide insight into the relationship of the thermal stability of the poled order with chemical bonding and elastic interaction of the NLO chromophores in polymeric matrices.
Quasiparticle Characteristics and Noise Properties of Superconductor-Normal Metal-Superconductor Quantum Well Devices
Authors: Takada Akio , Ikuta Toshiaki , Tachibana Akihiko , Fukumoto Takeshi , Hatle Michal , Hamasaki Katsuyoshi
Published: October 2002

All-thin film superconducting Nb-Nb nanoconstriction-NbN quantum well devices with improved low-frequency noise properties have been successfully fabricated. The quasiparticle current characteristics of this device are well explained by the Andreev reflection current. The low-frequency noise parameter η in Hooge's empirical theory decreases quickly with increasing device quality factor Q
eff=R
D(1 mV)/R
N(10 mV), i.e., with decreasing effective strength of the barrier potential at the superconductor (Nb, or NbM-nanoconstriction interface.
Heterostructure Fe:InP/InGaAs Metal-Semiconductor Field-Effect Transistors Grown by Metalorganic Chemical Vapor Deposition
Authors: Shei Shih-Chang , Su Yan-Kuin , Meiso Yokoyama Meiso Yokoyama
Published: October 2002

Novel lattice-matched Fe:InP/InGaAs heterostructure metal-semiconductor field-effect transistors (MESFETs) have been grown by metalorganic chemical vapour deposition (MOCVD). The resistivity of the epitaxially grown Fe:InP layer typically exceeds 1×108 Ω cm. The 3d6 one electron trap state of the Fe acceptor in InP is detected from the photoluminescence (PL). A high transconductance of 140 mS/mm is obtained for a 1-µ m-gate-length MESFET fabricated by depositing the gate metal directly on the semi-insulating Fe:InP layer. S-parameter measurements of high frequency and microwave characteristics indicate a projected maximum frequency of oscillation of f
max=21 GHz, and a current gain cutoff occurs at approximately 7.3 GHz.
Epitaxial Growth and Electrical Characteristics of β-SiC on Si by Low-Pressure Rapid Thermal Chemical Vapor Deposition
Authors: Hwang Jun-Dar , Fang Yean-Kuen , Song You-Joung , Dun-Nian Yaung Dun-Nian Yaung
Published: October 2002

The structural and electrical properties of β-SiC thin films grown on a (100) Si substrate by low pressure rapid thermal chemical vapor deposition (LP-RTCVD) at as low as 2.5 Torr are reported. SiC growth was achieved by the reaction of SiH4 (5% in H2) and C3H8 (5% in H2) from 1100 to 1250° C. The structural properties of SiC thin films were investigated by X-ray diffraction and scanning electron microscope (SEM) analysis. The X-ray diffraction shows that the full width at half-maximum (FWHM) is 0.34-0.35° for Si/C ratio of 0.4-0.7. An epitaxial SiC thickness up to 8 µ m was also observed by SEM.
The unintentionally doped SiC film is n-type with electron mobility of 132-254 cm2/V·s for carrier concentration around 1017 cm-3 and resistivity 0.08-0.3 Ω· cm, based on both four-point probe and Hall measurements. To our knowledge, the measured mobility is the highest of those reported for low-pressure CVD-grown β-SiC epilayers. The optimum growth temperature and Si/C ratio were 1150° C and 0.6, respectively.
Light Scattering Properties in Ternary Germanate Glasses
Authors: Sakaguchi Shigeki , Shinichi Todoroki Shinichi Todoroki
Published: October 2002

Ternary germanate glass systems of GeO2-P2O5-MF

x

( MF

x

: CaF2, ZnF2, PbF2, AlF3, and GaF3) are developed to investigate their light scattering properties. Glass-forming regions for these ternary systems are determined, and the systems containing the divalent fluorides, such as CaF2 and ZnF2, are found to exhibit wide glass-forming regions. Light scattering (Rayleigh scattering) and related properties for the systems are examined by comparison with those of pure GeO2 glass which is prepared by flame hydrolysis techniques. It is clarified that some glasses containing fluorides such as CaF2, ZnF2 and GaF3 at specified compositions exhibit scattering intensities less than that of GeO2 glass. The scattering intensity as low as 0.43 that of GeO2 is obtained for the GeO2-P2O5-CaF2 system.
Novel Selective Growth Using a Native Oxide on a (110) Cleaved Plane of AlGaAs/GaAs Superlattice
Authors: Notomi Masaya , Kadota Yoshiaki , Toshiaki Tamamura Toshiaki Tamamura
Published: October 2002

This paper reports a novel selective growth on a cleaved facet of AlGaAs/GaAs superlattice by low-pressure metal-organic vapor phase epitaxy. We reveal that the native oxide on the AlGaAs region of the cleaved facet of superlattice can be used as a selective growth mask by following a simple procedure. This mask pattern is very fine and uniform and can be used to fabricate laterally patterned structures whose period is determined by the period of the semiconductor superlattice. The growth proceeding on the grating-like structure formed on the (110)-cleaved plane by this selective growth is in highly slanted because of the asymmetric crystal planes that make up the grating, and the corrugated shape can be preserved during the growth of a thick AlGaAs layer, which is in marked contrast to the usual growth on (001)-oriented grating. Using these characteristics, we can fabricate stacked wire-like structures on the cleaved facet of a superlattice completely without undergoing a lithographic process. This fabrication method is promising for forming the dense-and-stacked quantum wires that are strongly required for device applications of multidimensional quantum structures.
Threading Dislocation Reduction in GaAs on Si with a Single InGaAs Intermediate Layer
Authors: Shiba Yasunari , Asai Koyu , Kamei Kazuhito , Hisashi Katahama Hisashi Katahama
Published: October 2002

The threading dislocation reduction behavior upon insertion of a single thick InGaAs intermediate layer into the GaAs heteroepitaxial layers on Si has been investigated. In the X-ray diffraction, with increasing InGaAs thickness below 0.5 µ m, the full width at half-maximum (FWHM) of the GaAs overlayer decreases even if the InGaAs thickness is beyond the critical layer thickness. In the cross-sectional transmission electron microscopy (TEM) observations, it has been found that sufficient misfit dislocations are introduced and that the threading dislocation density decreases at the GaAs/InGaAs interfaces in samples with InGaAs thicker than 0.1 µ m. The analysis based on the mechanical equilibrium theory shows that misfit dislocation formation at the interfaces plays an important role in reducing the threading dislocation density. The InGaAs intermediate layer is required to be thick enough to form misfit dislocations at the interfaces with relaxation of strain in the intermediate layer.
New Fabrication Method and Electrical Characteristics of Conical Silicon Field Emitters
Authors: Hashiguchi Gen , Hidenori Mimura Hidenori Mimura
Published: October 2002

A new fabrication method for a silicon field emitter has been proposed, which combines the techniques of Si KOH anisotropic etching and local oxidation of silicon (LOCOS) to form the emitter tip. The fabricated conical silicon emitter had an extremely well-defined structure indicative of good reproducibility and uniformity of the fabrication process. The emission characteristics were examined under DC and AC conditions, and indicated high performance of the emitter. Successful application to a digit display has been demonstrated.
Characterization of EuBa2Cu3Oy Synthesized in Shock Processes
Authors: Hikosaka Hideaki , Atou Toshiyuki , Kusaba Keiji , Suzuki Takashi , Fukuoka Kiyoto , Kikuchi Masae , Yasuhiko Syono Yasuhiko Syono
Published: October 2002

We synthesized a homogeneous, tetragonal EuBa2Cu3O

y

with c/a=3.00 by the shock compression method. The phase is considered to be similar to the tetragonal YBa2Cu3O

y

metastably formed at relatively low temperature with the c/a ratio=3.00. Electron diffraction patterns indicate ordering of Eu and Ba atoms to some extent, but ordering is presumably not perfect. High resolution trasmission electron microscory images show that shock-synthesized EuBa2Cu3O

y

consists of 60-80-Å-size domains, whose principal axes are perpendicular to each other. Perfect ordering of Eu and Ba atoms was achieved by annealing the shock-synthesized specimen above 900° C, resulting in the increase of the c/a ratio from 3.00 to 3.05 as well as superconduction upon O2 annealing. This result is explained by the shortness of the reaction time in shock processes.
Modulation Voltage and Flux Noise in High-Tc Grain Boundary Junction Superconducting Quantum Interference Devices
Authors: Suzuki Daisuke , Kuriki Shinya , Matsuda Mizushi
Published: October 2002

We have fabricated YBa2 Cu3 O7-δ bicrystal grain-boundary-junction superconducting quantum interference devices (SQUIDs) having various inductance values, and studied the characteristics of the flux-modulated voltage. Generally, the modulation voltage of high-T
c SQUIDs is lower than the value expected from the I
c
R
n product and the inductance. From the comparison of experimental and theoretical values, it has been found that thermal noise rounding of the I-V characteristic plays a major role in reducing the modulation voltage in the range of the noise parameter of γ=I
cΦ0/πk
B
T<20. On the other hand, noise flux in the SQUID loop generated by thermal noise currents contributes to reducing the modulation voltage in the range of γ>20. We have also studied the relationship between the normal resistance and the modulation voltage of the grain-boundary-junction SQUIDs.
Anisotropic Etching Process for Submicron Patterning of Nb Using CF 4
Authors: Hiroyuki Akaike Hiroyuki Akaike , Takeaki Watanabe Takeaki Watanabe , Akira Fujimaki Akira Fujimaki , Hisao Hayakawa Hisao Hayakawa
Published: October 2002

We have developed an anisotropic etching process for submicron patterning of Nb using CF4 reactive ion etching (RIE). This process is based on the sidewall protection effect of a fluorocarbon film. The fluorocarbon film is generated as the result of excessive consumption of fluorine by the additional load on the cathode electrode of an RIE reactor. We have improved the edge profile by adjusting the area of Si as an additional load and have succeeded in obtaining the vertical edge profile.
Magnetic Flux Focusing in DyBaCuO Step-Edge Josephson Junctions
Authors: Umezawa Toshimasa , Yasushi Higashino Yasushi Higashino
Published: October 2002

We have investigated magnetic flux focusing in DyBaCuO step-edge Josephson junctions. It was clear that the relationship between junction size W and the interval of the minima (ΔB) showed that ΔB was proportional to W
-2, not W
-1. It was inferred that film thickness t was much shorter than penetration depth λ. Also a clear Fraunhofer-like magnetic diffraction was observed in a junction with a steeper step angle (θ=60°) rather than θ=45°.
Magnetic Susceptibility of Some Mixed-Metal Compounds: NBu4Zn(II)xFe(II)1-x[Fe(III)(ox)3]
Authors: Bhattacharjee Ashis , Iijima Seiichiro , Mizutani Fumio , Katsura Tatsuo , Matsumoto Naohide , Ōkawa Hisashi
Published: October 2002

The temperature dependence of the molar magnetic susceptibility of NBu4Zn(II)

x

Fe(II)1-
x

[Fe(III)(ox)3] compounds, where NBu4
+=tetra-n-butylammonium ion and ox2-=oxalate ion with 0≤x<1 were studied in the temperature range of 5-290 K.
The compounds with x≤0.1 showed two susceptibility maxima on temperature scale in 40.5-43.5 K and 10-24 K temperature ranges. These compounds undergo ferrimagnetic transition in the 40.5-43.5 K range. The difference in their magnetic susceptibility variations with temperature in the field-cooled and zero field-cooled modes indicated that these compounds exist in a “spin-glass” like state below 35 K range. The molar magnetic susceptibility variation with temperature obeys the Curie-Weiss law at higher temperatures ( >90±10 K). Several x dependent Curie-Weiss constant were evaluated.
Ferrite Plating of Ba-Containing Iron Oxide Films Using Chelated Highly Alkaline (pH=11-13) Aqueous Solutions
Authors: Itoh Tomoyuki , Miki Takeshi , Zhang Qun , Abe Masanori , Tamaura Yutaka
Published: October 2002

Films of Fe2 O3-δ and Ba-containing iron oxide were successfully synthesized from chelated highly-alkaline aqueous solution by ferrite plating on substrates heated by Xe-lamp beams. The solubility limit of Ba in Ba-containing iron oxide films was Ba/Fe=∼0.16. The intensity of the X-ray scattering peaks due to the spinel structure decreased as the content of Ba in the films increased, and when Ba/Fe>∼0.06, the films did not exhibit the X-ray scattering peaks of crystalline structure. After annealing the Ba-containing iron oxide films ( Ba/Fe=∼0.1), the X-ray scattering peaks of the BaFe12O19 crystalline phase appeared.
Dependence of Magnetization on Short-Range Order for Ni3Mn Alloys
Authors: Teiko Okazaki Teiko Okazaki
Published: October 2002

The magnetization-vs-temperature curves have been investigated for Ni3Mn alloys whose degrees of long-range order spread from 0 to 0.95 and for the 80 at.% Ni-Mn alloy. These relative spontaneous magnetization vs reduced temperature curves satisfy the law of corresponding states and fit the theoretical curves derived from the Brillouin function, whose total angular momentum quantum numbers are the integral multiples of 1/2. Based on these results, the strengths of the Weiss molecular field at 0 K were calculated. They depend strongly on the parameters of short-range order, τ's, and have the same tendencies as the local moments of Mn atom vs τ calculated using a new theory of the finite-temperature magnetism of the Ni-Mn alloy, which takes account of the local environment effect.
Reviewing the Forces of Electret Motors by Applying Maxwell Stress Tensor and Delta Function
Authors: Yasufusa Tada Yasufusa Tada
Published: October 2002

The forces exerted on the electret rotors of the conventional Gubkin- and Jefimenko-type electret motors and the intermediate-type motor have been derived systematically using the Maxwell stress tensor and delta function. The delta function is effective in deriving the force due to the edges of a pair of stator electrodes of the Gubkin-type motor. The force based on the so-called slot effect appearing in the Jefimenko-type motor can be derived as the sum of the forces due to the edges of the pairs of stator electrodes constituting the slots. The equation derived for total force of a Jefimenko-type motor has the form of the sum of two total forces appearing in two simple slot effect transducers in which each electret has a different charge density. The equations obtained here for the forces have the same forms as those previously obtained using the energy principle.
Effects of Saponification Rate on Electrooptical Properties and Morphology of Poly(vinyl alcohol)/Liquid Crystal Composite Films
Authors: Ono Hiroshi , Nobuhiro Kawatsuki Nobuhiro Kawatsuki
Published: October 2002

The relationship between the saponification rate of poly(vinyl alcohol) (PVA), and the electrooptical properties and morphology of the PVA/liquid crystal (LC) composite films was investigated. Light transmission clazing and the LC droplet size were varied by changing the saponification rate or the blend ratio of two kinds of PVA with different saponification rates because the refractive index and surface tension could be controlled by the saponification rate of PVA.
The threshold voltage decreased with increasing saponification rate though the extrapolation length was decreased. It was suggested that the electrooptical properties were strongly dependent on the droplet size.
Production of High-Quality Thin-Film Samples of Al-Cu-Fe Icosahedral Quasicrystal
Authors: Akinori Yoshioka Akinori Yoshioka , Keiichi Edagawa Keiichi Edagawa , Kaoru Kimura Kaoru Kimura , Shin Takeuchi Shin Takeuchi
Published: October 2002

Thin-film samples of Al-Cu-Fe icosahedral quasicrystal have been successfully produced by vacuum deposition with an electron beam evaporation apparatus followed by annealing. Coating the film surfaces with alumina has been found to be essential in avoiding compositional change during annealing. X-ray diffractometry and electrical resistivity measurements have shown that the annealed sample having the icosahedral phase is of high quality.
Carbon Nanocapsules Grown on Carbon Fibers
Authors: Kusunoki Michiko , Ikuhara Yuichi , Jun-ichi Kon Jun-ichi Kon
Published: October 2002

Carbon nanocapsules grown on pitch-based carbon fibers were investigated by high-resolution electron microscopy. It was found that they were formed during heating up to 2000° C in 1 atm N2 gas. Two types of nanocapsules were found: one was a capsule enclosing a CaS single crystal and the other was a cubic hollow capsule. The growth mechanism of these carbon nanocapsules was discussed by comparing the structures of particles formed at several temperatures.
Crystallization of V5+- and Zr4+-Substituted KTiOPO4 Crystals from Flux
Authors: Chani Valery I. , Shimamura Kiyoshi , Tsuguo Fukuda Tsuguo Fukuda
Published: October 2002

V5+- and Zr4+-containing KTiOPO4 (KTP) crystals were grown by spontaneous crystallization. In according to X-ray powder diffraction data the unit cell volumes for all crystals obtained were larger than those for non substituted KTP.
Thus, it was proven that V5+ substitutes P5+ in tetrahedral positions of the KTP structure. On the basis of the experimental data obtained, the occupation mechanism of each cation in the KTP structure and the trends of improvement of structural stability have been discussed.
Preparation of Various Oxide Films by an Electrophoretic Deposition Method: A Study of the Mechanism
Authors: Koura Nobuyuki , Tsukamoto Takeyo , Shoji Hiromasa , Touru Hotta Touru Hotta
Published: October 2002

The electrification mechanism of an oxide particle in a bath was analyzed. The zeta-potentials of various oxide particles in an acetone bath were found to be positive. The data suggested that H+ ions are generated in an acetone bath containing a small amount of added I2 and H2O by the keto-enol equilibrium reaction and then adsorbed on the oxide resulting in positively charged particles. The adsorption of H+ ions was assumed to be of the type of mono-molecular adsorption. Moreover, the electrodeposition flocculation mechanism for the particle was also investigated. On the basis of a relation of electrophoretic current with depositing time well described by the Cottrell equation, it was suggested that the electrochemical reaction proceeds on the cathode substrate surface and that the rate-determining step arises from the diffusion of H+ ions in the deposited film.
Highly Sensitive Detection of Oxygen from Si(111)7×7 Surface by Time-of-Flight-Type Electron Stimulated-Desorption Spectroscopy
Authors: Kazuyuki Ueda Kazuyuki Ueda
Published: October 2002

In this paper we describe the experimental observation of a small amount of oxygen on silicon surfaces flashed at 1250° C with time-of-flight-type electron-stimulated desorption (TOF-ESD) spectroscopy. The TOF-ESD enables us to detect about 10-4 of a monolayer of oxygen on a “cleaned” Si(111)7×7 surface. The amount of oxygen detected is less on the surface of silicon quenched after flashing at 1250° C than after annealing. This suggests that oxygen is accumulated on the silicon surface by thermal diffusion of SiO.
Formative Time Determination in Nitrogen-Filled Tube Using Statistical Methods
Authors: Pejović Momčilo , Živković Jasmina , Milosavljević Čedomir , Goran Ristić Goran Ristić
Published: October 2002

The formative time for different values of afterglow period with/without positive bias on the electrodes in nitrogen-filled tube has been investigated. The obtained values for average formative time delay which is determined as the difference between average total time delay of electrical breakdown and standard deviation are in accordance with those evaluated from the Laue distribution. The good agreement of formative time values which are determined by these methods is observed in the case when the electrical breakdown is mostly initiated by secondary electrons from the cathode induced by positive ions which remained from the previous discharge.
Resolution Enhancement by Oblique Illumination Optical Lithography Using a Transmittance-Adjusted Pupil Filter
Authors: Horiuchi Toshiyuki , Harada Katsuhiro , Matsuo Seitaro , Takeuchi Yoshinobu , Tamechika Emi , Yoshiaki Mimura Yoshiaki Mimura
Published: October 2002

This paper describes the resolution enhancement by oblique illumination optical lithography using a transmittance-adjusted pupil filter that has a conjugate shape to the secondary light source. The resolution enhancement depends on the amplitude transmittance distribution of the pupil filter in the lens aperture. Thus, the optimum transmittance distribution attaining the highest resolution at a practical depth of focus is investigated, and superior performance is verified experimentally using an actual i-line stepper, that is, the actual resolution improvement is comparable to the simulation results. Despite this improvement, two problems must be addressed. Pattern profiles degrade at the ends of periodical patterns, and the opaque pattern widths of middle-pitch patterns become a little narrow. These two problems are solved by optimizing the transmittance distribution of the filter such that there is no significant deterioration in the high-resolution performance.
Thermal Agglomeration of Thin Single Crystal Si on SiO2 in Vacuum
Authors: Ono Yukinori , Nagase Masao , Michiharu Tabe Michiharu Tabe , Yasuo Takahashi Yasuo Takahashi
Published: October 2002

Changes in the surface structure of the single-crystal Si/SiO2/Si system during vacuum heating (950-1200° C) have been investigated using atomic force microscopy and scanning Auger electron microscopy. When the top Si layer is sufficiently thin, e.g., below ∼30 nm for heating at 1100° C, holes are formed due to Si agglomeration. The buried SiO2 surface emerges at the bottom of the holes and Si atoms accumulate around them. These holes expand and coalesce with increasing temperature, and Si islands are finally formed at 1200° C. This Si agglomeration starts at the points where the Si layer is locally extremely thin due to SiO2 protrusions and proceeds anisotropically; the shape of the holes is hexagonal for the (111) surface and square for the (001) one. In both cases, their sides are in the <110> directions. The driving force of agglomeration in a single-crystal film is discussed.
Highly Efficient Optical Second Harmonic Generation in Poled Ti-Doped Silica Glasses
Authors: Tanaka Katsuhisa , Kashima Kenichi , Hirao Kazuyuki , Soga Naohiro , Yamagata Shigeru , Mito Akihiro , Nasu Hiroyuki
Published: October 2002

Optical second harmonic intensity of poled Ti-doped silica glasses prepared by the Verneuil method has been measured. The second-order nonlinear coefficient, d
33, of the glasses prepared from starting materials of TiO2 and SiO2 powders ranges from 0.2 to 0.5 pm/V. These values are one order of magnitude larger than that for silica glass without intentional dopants.
Anisotropic Refractive Index of Porous InP Fabricated by Anodization of (111)A Surface
Authors: Eijiro Kikuno Eijiro Kikuno , Marco Amiotti Marco Amiotti , Toshiyuki Takizawa Toshiyuki Takizawa , Shigehisa Arai Shigehisa Arai
Published: October 2002

We measured, for the first time, the anisotropic refractive index of porous InP obtained by photoassisted anodization of the (111)A surface in the direction parallel (n
o=2.82) and perpendicular (n
e=2.66) to the axis of the pores. The refractive index in the two directions was found to be 10–20% lower than the refractive index of bulk InP (n=3.17).