bluuebunny/crossref_metadata_2025 huggingface dataset:
Single Domain Hexagonal GaN Films on GaAs (100) Vicinal Substrates Grown by Hydride Vapor Phase Epitaxy
Authors: Yamaguchi A. Atsushi , Manako Takashi , Sakai Akira , Sunakawa Haruo , Kimura Akitaka , Nido Masaaki , Akira Usui Akira Usui
Published: October 2002

Hexagonal GaN ( h-GaN) films are grown on GaAs (100) vicinal substrates by hydride vapor phase epitaxy. The substrate misorientation dependence of the crystal structure is investigated by X-ray diffraction measurements using a 4-circle diffractometer. It is found that misorientation toward the <111> B direction is essential for the growth of single domain h-GaN films and that the c-axis of the single domain h-GaN orients to the GaAs <111> B direction.
Magnetooptical Overcoating of MnSb Films by Surface Oxidation
Authors: Akinaga Hiroyuki , Miyanishi Shintaro , Suzuki Yoshishige
Published: October 2002

We demonstrate that surface oxidation has a pronounced effect on the magnetooptical properties of MnSb films when used as a magnetooptical overcoating technique. As a result of oxidation, the surface of the film was coated by an oxide layer and sharp divergent and dispersive structures appeared in the Kerr rotation and ellipticity spectra at around 3.7 eV, respectively. The structures were very large and the absolute value of the Kerr ellipticity at 3.8 eV was more than 3°, which is about 6 times larger than that of the MnSb film before oxidation. The change in these spectra due to surface oxidation was reproduced by numerical calculations.
Growth of Nitrogen-Doped ZnSe by Photoassisted Metalorganic Chemical Vapor Deposition
Authors: Fujita Yasuhisa , Toshiyuki Terada Toshiyuki Terada , Satoshi Fujii Satoshi Fujii
Published: October 2002

Growth of nitrogen-doped ZnSe using dimethylzinc and dimethylselenide in the growth temperature range of 330 to 390° C by photoassisted metalorganic chemical vapor deposition (MOCVD) employing an ultrahigh-pressure Hg lamp was investigated. t-Butylamine was used as a nitrogen dopant source. A nitrogen concentration of more than 1018 cm-3 was obtained. The samples showed p-type conduction, and a maximum hole concentration of 3.0×1018 cm-3 was achieved by MOCVD.
Low Temperature Growth of GaAs and InAs/GaAs Quantum Well on (111)B Substrate by Metalorganic Vapor Phase Epitaxy
Authors: Toshio Nishida Toshio Nishida , Naoki Kobayashi Naoki Kobayashi
Published: October 2002

Metalorganic vapor phase epitaxy of InAs quantum wells on GaAs (111)B substrate is investigated by simultaneous monitoring of surface photo-absorption. To lower the growth temperature of the GaAs barrier, we adopted the flow-rate-modulation method and obtained specular morphology of GaAs at 600° C. Indium segregation is confirmed by surface photo-absorption and suppressed by introducing a capping layer grown under an arsenic rich condition. We obtained a one-monolayer InAs/GaAs quantum well, and confirmed its abrupt interfaces by TEM and a photoluminescence narrower than 6 meV.
Damage to YBa2Cu3Oy Surface Caused by Ar Ion Beam Etching
Authors: Matsui Toshiyuki , Dabide Yamaguchi Dabide Yamaguchi , Hiroshi Kamijo Hiroshi Kamijo
Published: October 2002

We studied transport properties through a YBa2Cu3O
y
(YBCO) surface etched by exposure of the YBCO surface to an Ar ion beam. In layered junctions of Au/(100)-oriented YBCO with the etched surface, Poole-Frenkel emission was detected by analyzing current-voltage curves. This suggests that a relatively thick insulating layer was formed on the YBCO surface by damage resulting from the Ar ion beam etching.
Dependence of YBa2Cu3O7-x Ultrathin Film Surface Morphology on Substrate and Growth Temperature
Authors: Mukaida Takashi Tsurumaki
Published: October 2002

We have studied the influence of substrate matching and growth temperature on the morphology of YBa2Cu3O7-
x

ultrathin film. For films grown on SrTiO3 and NdGaO3 substrates, we observed a temperature-dependent surface morphology. The film changed from a smooth epitaxial layer at growth temperatures equal to or below 750° C, into one with several unit-cell-high islands at 800° C. It was also found that the density of these islands differs between films on SrTiO3 and NdGaO3 substrates. This substrate-dependent island density was interpreted in terms of the Stransky-Krastanov-type film structure model together with an assumed temperature dependence of the epitaxial layer thickness.
High-field Domain Formation Conditions in Semiconductor Multiple Quantum Well Sequential Resonant Tunneling Structures
Authors: Yozo Shimada Yozo Shimada , Kazuhiko Hirakawa Kazuhiko Hirakawa
Published: October 2002

We investigated the tunneling current-voltage ( I–V ) characteristics of Al0.3Ga0.7As/GaAs multiple quantum well (MQW) diodes with various electron densities, N
s, and scattering rates, Γ. Clear periodic negative differential resistances (NDRs) due to the formation of high-field domains were observed for the samples with low N
s and Γ, while such NDRs were completely absent in the first plateau region of the I–V characteristics of the samples with high N
s and Γ. It was found that such formation/destruction of the high-field domains in MQW diodes is controlled by the interplay of the tunneling rate and the electron supply functions between adjacent coupled quantum wells. The condition for the high-field domain formation is clarified as a function of N
s and Γ.
A Simple, Analytical and Complete Deep-Submicrometer Fully Depleted Silicon-on-Insulator Metal-Oxide-Semiconductor Field-Effect-Transistor Model Considering Velocity Overshoot
Authors: Jang Sheng-Lyang , Hu Man-Chun , Shau-Shen Liu Shau-Shen Liu , Young-Shying Chen Young-Shying Chen
Published: October 2002

In this paper, we present a simple, complete and analytical deep-submicrometer silicon-on-insulator metal-oxide-semiconductor field-effect-transistor (SOI MOSFET) model for accurate simulation of digital/analog circuits. The model was developed using the drift-diffusion equation with a modified mobility formula to account for velocity overshoot, and was based on the quasi-two-dimensional Poisson's equation. It is a charge control model, expressed as a function of inversion charge per unit area. The drain-induced barrier lowering and the channel-length modulation were solved using the quasi 2-D approach and were incorporated into the drain current equation. The mobility reduction due to the transverse field was also taken into consideration. The resulting single-piece drain current equation is smoothly continuous; it has been successfully applied to model both submicrometer and deep-submicrometer n-type SOI MOSFETs with various channel lengths, and a good agreement between the modeled and experimental data has been obtained. This model uses few fitting parameters and can be employed in a circuit simulator to improve the convergence of simulation and computational efficiency.
A New Ultra Low Voltage Silicon-Rich-Oxide (SRO) NAND Cell
Authors: Lin Chrong-Jung , Hsu Charles Ching-Hsiang , Chen Hwi-Huang , Hong Gary
Published: October 2002

Thin silicon-rich-oxide (SRO) film can be an efficient and reliable tunneling injector for the low voltage application in Flash memory cell. To date, no work has been done on the quantitative and microscopical tunneling model for the SRO enhancement behavior. Moreover, no complete investigation on array-level SRO Flash cell have been presented. In this paper, a new low voltage SNAND (SRO NAND) cell is proposed and investigated, especially in term of performance characteristics and reliability issues. Furthermore, a two-dimensional microscopical model for SRO tunneling characteristics is developed to quantitatively explain the tunneling enhancement characteristics for SRO Flash memory cell. Results show that the tunneling model agrees well with the tunneling characteristics of SNAND cell and also provided the insight into tunnel oxide scaling in SNAND cell operation. The erase and program voltage can be reduced from 22 V to 7 V and 12 V with improved erase speed up to 2 orders, respectively. More than 105 endurance cycles are achieved. The feasibility of the SNAND cell is demonstrated.
Study of BixY 3-xFe 5O12 Thin Films Grown by Pulsed Laser Deposition
Authors: Ming-Yau Chern Ming-Yau Chern , Juin-Sen Liaw Juin-Sen Liaw
Published: October 2002

Epitaxial films of Bi\sitx
Y3-\sitx
Fe5O12 (Bi:YIG) have been grown on [111]-oriented gadolinium-gallium-garnet substrates, Gd3Ga5O12 (GGG), by pulsed laser deposition (PLD). Complete epitaxial substitution of the bismuth, Bi3Fe5O12 (BIG), was achieved at a growth temperature of 500 °C and an O2 atmosphere of 200 mTorr. The epitaxial nature of the films was indicated by the diffraction patterns from reflection high-energy electron diffraction (RHEED). X-ray diffraction (XRD) also showed that there were no peaks other than multiples of the (444) reflection. The Faraday rotation angle, θ F, of these films increases linearly with the Bi content x yielding θ F/x = -1.9 deg/µm at λ= 633 nm and T = 300 K. From magnetooptical Kerr measurements (MOKE) we conclude that the uniaxial anisotropy constant, K
u, of the BIG film is positive, which could be due to the expansive stress caused by the difference in thermal expansion of the film and the substrate.
2AgExciton State below 1BuExciton State in Trans-Polyacetylene Observed by Second-Harmonic-Generation Spectroscopy
Authors: Nishioka Takahiro , Yamada Toshiki , Shibahara Seiji , Ishikawa Ken , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: October 2002

We measured second-harmonic-generation spectra of centrosymmetric trans-polyacetylene films. A resonance peak was observed and assigned to the electric-quadrupole transition to the 2Agexciton state at about 0.96 eV, which is located below the 1Buexciton state at about 1.5 eV. We have also discussed the relative magnitude of the transition dipole between the excited states by comparing the various nonlinear optical spectra.
Effects of a Metal Film and Prism Dielectric on Properties of Surface Plasmon Resonance in a Multilayer System
Authors: Liao Chin-Hsiung , Lee Cheng-Min , Liann-Be Chang Liann-Be Chang , Jen-Hwan Tsai Jen-Hwan Tsai
Published: October 2002

The properties of surface plasmon (SP) resonance in a multilayer system have been investigated. We derived an approximation of the reflectivity formula from the Fresnel formulas. Furthermore, a series of approximate expressions for the damping rate of SP, the resonant angle, the optimum metallic thickness of the system, and the halfwidth of resonance have been proposed. Theoretical calculations are in good agreement with the numerical simulations. This study leads to the conclusion that the damping rate of SP and the halfwidth of resonance for a silver film used in the multilayer system are much smaller than those of other metal films used in the system In addition, the damping rate of SP can also be decreased and the sensitivity of resonant angle can be increased by using a prism with a small dielectric constant.
Broad-Band Conductive Spectra of Polypropylene Oxide Complexed with LiClO4
Authors: Furukawa Takeo , Mariko Imura Mariko Imura , Hiroshi Yuruzume Hiroshi Yuruzume
Published: October 2002

Broad-band conductive spectroscopy covering a 10 mHz–1 GHz frequency range has been employed to examine the ionic motions in polypropylene oxide (PPO) complexed with 0–1% LiClO4 at temperatures from -60 °C to 100 °C. The dc conduction appears as a plateau of the conductive spectra in their medium frequency range. As the frequency is lowered, the dc conduction is suppressed by the electrode polarization and results in a Cole-Cole conductive relaxation. At high frequencies, the conductive spectra are overtaken by the dielectric relaxations due to dipolar motions associated with the segmental- and normal-mode processes of PPO molecules. In addition, a new relaxation process was found, which is attributable to the ionic motion because the relaxation strength increases with LiClO4 concentration in parallel with an increase of dc conductivity. This finding suggests that the dissociated ions undergo local fluctuational motion (ionic relaxation) prior to starting long-range diffusion (dc conduction). Analysis based on a dynamic bond percolation theory shows that this ionic relaxation occurs in harmony with segmental-mode motion while the dc conduction is associated with the normal-mode process through a renewal of local hopping probabilities.
The Effect of Growth Conditions on the Dielectric Properties of Pb(Zn1/3Nb2/3)O3 Single Crystals
Authors: Park Seung-Eek , Mulvihill Maureen L. , George Risch George Risch , Thomas R. Shrout Thomas R. Shrout
Published: October 2002

The effect of growth conditions on the dielectric properties and ferroelectric transition of perovskite Pb(Zn1/3Nb2/3)O3 single crystals was examined. Crystals were grown by the flux technique using PbO as a self flux. Increased cooling rate and soaking temperature resulted in a decreased Zn/Nb ratio, and corresponding increased temperature of the maximum dielectric constant (T
max
), and decreased room temperature values of the dielectric constant and loss. Different crystal colors and quality were also associated with the various growing conditions. Although dielectric properties, domain stability after poling, and associated piezoelectric properties are a function of T
max
, it was shown that crystal quality was critical for the observed variation in these properties.
Three-Dimensional Analysis of Spurious Vibrations of Rectangular AT-cut Quartz Plates
Authors: Akio Ishizaki Akio Ishizaki , Hitoshi Sekimoto Hitoshi Sekimoto , Yasuaki Watanabe Yasuaki Watanabe
Published: October 2002

We have developed a technique for the three-dimensional (3-D) analysis of all the spurious vibrations of rectangular AT-cut quartz plates. The 3-D displacements are described with a linear combination of modes guided along the X crystal axis of an AT-cut quartz strip. We accurately calculate each guided mode by applying the one-dimensional finite element method to the two-dimensional strip waveguide problem. To uniquely determine the amplitudes of guided modes in the 3-D solutions we employ the variational expression for the stress-free conditions on the X-length edges. The present technique makes it possible to perform 3-D analysis of spurious vibrations within a reasonable computational time. Frequency spectra for rectangular AT-cut quartz plates are computed as a numerical example and are compared with the numerical results obtained using an extended version of the previous method and with Koga's experimental data. Vibrational patterns of spurious modes are shown, and a convergence study is carried out.
Pd/Ni–Al 2O 3–Al Tunnel Diode as High-Concentration-Hydrogen Gas Sensor
Authors: Sumio Okuyama Sumio Okuyama , Kazuaki Umemoto Kazuaki Umemoto , Katsuro Okuyama Katsuro Okuyama , Shigetoshi Ohshima Shigetoshi Ohshima , Koichi Matsushita Koichi Matsushita
Published: October 2002

Pd/Ni–Al2O3–Al tunnel diodes were fabricated on a glass substrate for detection of high-concentration hydrogen gas. For Pd–Al2O3–Al diodes, the output signals were saturated at hydrogen partial pressures higher than approximately 0.1 Torr, whereas a Pd/Ni(22%)–Al2O3–Al diode showed output signals even at 50 Torr hydrogen partial pressure at room temperature. The concentration of hydrogen detectable with the Pd/Ni alloy metal–insulator–metal (MIM) diodes increased with an increase in the Ni content. The change in the barrier height at the Pd/Ni–Al2O3 interface upon introduction of hydrogen gas was also measured for various Ni contents in Pd/Ni alloys by means of the logarithmic derivative of the tunnel current and was found to be associated with the hydrogen sensitivity of the Pd/Ni alloy MIM junctions.
X-Ray Diffraction Study of ZnSe(111) Films Grown on GaAs(111)A Substrates by Molecular Beam Epitaxy
Authors: Matsumura Nobuo , Shimakawa Hiroyuki , Mori Tatsushi , Koichiro Maemura Koichiro Maemura , Junji Saraie Junji Saraie
Published: October 2002

ZnSe(111) films grown on GaAs(111)A substrates were studied by X-ray diffraction measurement. The [111] axis of ZnSe epilayers was tilted toward the [100] direction when the films were grown on 5°- and 10°-misoriented substrates toward the [100] direction. However, such tilting was not observed in the epilayers grown on just-oriented substrates. The lattice spacing d
111 of the epilayers was measured and the lattice deformation and relaxation were studied.
The Stability of the Rotation of Steklov Gyro
Authors: Ge Zheng-Ming , Tzung-Shing Hu Tzung-Shing Hu , Sann-Chie Lee Sann-Chie Lee
Published: October 2002

In both uniform gravitational field and Newtonian central gravitational field, the conditions of stability and instability of the permanent rotation of the Steklov gyro with linear damping or nonlinear damping torques are studied by the Liapunov direct method and the first approximation method. Additionally, some new theorems are used in finding the stability and asymptotic stability of the gyro motion. In the Newtonian central gravitational field for the sake of high accuracy, the second order term of 1/R in the expression of potential energy has been considered, where R is the distance between the mass center of the gyro and the center of the earth. Numerical results are presented to show the domains of attraction in two cases by using a cell-to-cell mapping, the effects of types of damping torque and the system parameters on the gyro motion are also discussed in these cases.
Selective Nucleation-based Epitaxy (SENTAXY): A Novel Approach for Thin Film Formation
Authors: Hideya Kumomi Hideya Kumomi , Takao Yonehara Takao Yonehara
Published: October 2002

We have proposed a novel approach to form polycrystalline thin films called SENTAXY (Selective Nucleation-based Epitaxy). The location of the crystallites and boundaries with neighbors are generally random in polycrystalline films over amorphous substrates, because the formation of the films is initiated by the spontaneous nucleation of crystallites. The proposed method introduces artificial nucleation sites at which the crystallites nucleate selectively and grow epitaxially. As a result, it becomes possible to predetermine the location of crystallites and their boundaries. The principle of the method has been demonstrated in the chemical-vapor deposition of Si and the solid-state crystallization of amorphous Si films and has also been applied to other systems.
Evaluation of Hot-Hole-Induced Interface Traps at the Tunnel-SiO2(3.5 nm)/Si Interface by the Conductance Technique
Authors: Shigeo Ogawa Shigeo Ogawa , Toshio Kobayashi Toshio Kobayashi , Satoshi Nakayama Satoshi Nakayama , Yutaka Sakakibara Yutaka Sakakibara
Published: October 2002

Hot-hole-induced interface degradation in ultrathin (3.5 nm) oxides has been evaluated by the small-signal AC conductance technique. To degrade the tunnel-SiO2/Si interface, holes are injected by the avalanche technique. The conductance technique makes it possible to estimate the number of interface traps even when there are a large intrinsic tunneling leakage before injection and a large stress-induced leakage current after injection. Experimental results show that holes can create acceptor-like interface traps at the tunnel-SiO2/Si interface and that the conventional reliability test comprising carrier injection and interface-trap estimation is still applicable to oxides as thin as 3.5 nm.
Scanning Tunneling Microscopy Observation on the Atomic Structures of Step Edges and Etch Pits on a NH 4F-Treated Si(111) Surface
Authors: Hiroyuki Sakaue Hiroyuki Sakaue , Eiki Takahashi Eiki Takahashi , Tomoaki Tanaka Tomoaki Tanaka , Shoso Shingubara Shoso Shingubara , Takayuki Takahagi Takayuki Takahagi
Published: October 2002

The atomic structures of the step edge and the etch pit on a NH4F-treated Si(111) surface were studied by ultra high vacuum (UHV) scanning tunneling microscopy (STM) observation, by Fourier transform infrared (FT-IR) absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. An atomic image of the area near the step edge on the surface of hydrogen terminated 1×1 Si(111) prepared by NH4F treatment was obtained using STM taking care to avoid organic contamination on the observed sample surface. Hydrogen atoms terminating the topmost Si atoms on the terrace were observed to be closely packed with a threefold symmetry. Various size pits with triangular shape were observed on the terrace aligned with one vertex pointing to the [112] direction. The existence of one-atom size etch pits was also confirmed. The step edge was confirmed to contain some kinks. We observed a hydrogen atom of the Si-H bond projecting in an oblique direction from the endmost Si atom at the step edge.
Gap-filling of Cu Employing Sustained Self-Sputtering with Inductively Coupled Plasma Ionization
Authors: Ichiki Takanori , Kikuchi Toshiaki , Sano Atsushi , Shingubara Shoso , Yasuhiro Horiike Yasuhiro Horiike
Published: October 2002

Copper filling of high aspect-ratio gaps has been investigated systematically using sustained self-sputtering with ICP ionization. In order to understand gap-filling characteristics, deposition and/or resputtering rates have been measured as a function of the substrate bias, inductively coupled plasma (ICP) power, and the incident angle of ions to the substrate. Since Ar ions are excluded from the plasma, considerable improvement of the bottom coverage has been achieved with proper substrate biasing. This paper also illustrates both the limiting problems and the possibility of the high aspect-ratio hole filling by this method.
High Responsivity in an Optically Controlled Field-Effect Transistor Using the Direct Wafer Bonding Technique
Authors: Takayuki Sakai Takayuki Sakai , Kazuhiko Shimomura Kazuhiko Shimomura
Published: October 2002

An optically controlled field-effect transistor (FET) in which the GaAs FET region and the GaInAs/InP light absorption region were directly bonded is demonstrated. This device offers high optical- to-electrical conversion efficiency. In this work, we report the electrical and optical characteristics of this device based on the direct wafer bonding technique. The bonding temperature dependence on the device characteristics and responsivity characteristics were also measured. As a result, we achieved a high responsivity of more than 150 A/W.
Thinning of SOI Bonded Wafers by Applying Voltage during KOH Etching: Improvement of Thickness Variation by Reducing Leakage Current
Authors: Atsushi Ogura Atsushi Ogura
Published: October 2002

A thinning technique for controlling thickness variation in Si-on-insulator (SOI) bonded wafers is presented. During KOH etching, voltage is applied between the supporting substrate and the etchant. The SOI thickness variation after the etch stop depends on the leakage current during etching. Reducing the current to the order of nanoamperes results in a thickness range of 50 nm. An average thickness of the superficial Si ranging from 0.3 to 2 µ m is obtained by etching 3±0.5-µ m-thick SOI bonded wafers, and depends on the applied voltage. Atomic force microscopy observation reveals a surface roughness of 1.4 nm (root-mean-square).
Surface Plasmon-Enhanced Photocurrent in Organic Photoelectric Cells
Authors: Saito Takashi Wakamatsu , Youichi Sakakibara Youichi Sakakibara , Hiroshi Yokoyama Hiroshi Yokoyama
Published: October 2002

Enhanced photocurrent due to the excitation of surface plasmons (SPs) in organic photoelectric cells of MgF2/Al/copper phthalocyanine (CuPc)/Ag structure has been investigated. SPs were excited both at Ag/air and at Al/MgF2 interfaces, using the attenuated total reflection (ATR) method. The enhancement of the photocurrent due to SP excitation depended considerably upon the wavelengths of incident light. The origin of the enhancement is discussed, comparing the experimental results with the calculations of the light absorption in the cells. The results suggested that excitation of SPs induced an increase in the light absorption at the CuPc layer, which led to the enhanced photocurrent. It was found that the light absorption by SP excitation was substantially effected by the anomalous dispersion of the CuPc dye.
Orientation Control of Sr0.7Bi2.3Ta2O9+α Thin Films by Chemical Liquid Deposition
Authors: Koiwa Ichiro , Kanehara Takao , Mita Juro , Iwabuchi Toshiyuki , Osaka Tetsuya , Ono Sachiko
Published: October 2002

The orientation of Sr0.7Bi2.3Ta2O9+α (SBT) films, which are layer-type bismuth compounds, was controlled by varying the Sr-source. In this paper, the effect of crystal orientation on film characteristics is described. The crystal orientation of the SBT ferroelectric films did not affect the surface morphology, leakage current or fatigue characteristics, but it did affect the shape of the hysteresis loop (polarization) and the window value of the C-V characteristics when the films were connected to a metal-oxide-semiconductor (MOS) diode. Although a complete c-axis orientation film with a stoichiometry of SrBi2Ta2O9 shows no spontaneous polarization in general, the highly c-axis orientated Sr0.7Bi2.3Ta2O9+α film in this study showed some spontaneous polarization. The polarization values are larger than expected by considering orientation alone. A deviation from stoichiometry resulted in an increase made in the polarization along the c-axis. Therefore, control of the crystal orientation and composition of SBT films is quite an important factor in actual applications.
A Novel Technique for Ultrathin CoSi2 Layers: Oxide Mediated Epitaxy
Authors: Raymond T. Tung Raymond T. Tung
Published: October 2002

A novel technique, oxide mediated epitaxy (OME), was recently described for the growth of single crystal CoSi2 layers on the (100), (110), and (111) surfaces of silicon. Deposition of a thin layer of cobalt (1–3 nm) onto Si surfaces covered with a thin peroxide-grown SiO
x
layer and annealing at 500–700° C led to the growth of essentially uniform, epitaxial CoSi2 layers. The thin SiO
x
layer remained largely on the surface of the OME grown CoSi2 layers as a cap. Deposition of cobalt at elevated temperature onto OME grown CoSi2 layers led to a significant re-evaporation of cobalt from the SiO
x
surface. Presently, the OME effect was demonstrated on heavily doped p+ and n+-Si and on narrow (0.22 µ m) Si lines. On all surfaces, thin (10–30nm), excellent quality, CoSi2 single crystal thin films were grown by repeated growth sequences involving depositions of cobalt at room temperature and anneals at 600–700° C. It was also shown that faceting at CoSi2/Si(100) interfaces could be significantly reduced by a high temperature anneal.
Proposal of a Single-Transistor-Cell-Type Ferroelectric Memory Using an SOI Structure and Experimental Study on the Interference Problem in the Write Operation
Authors: Ishiwara Hiroshi , Toshishige Shimamura Toshishige Shimamura , Eisuke Tokumitsu Eisuke Tokumitsu
Published: October 2002

A single-transistor-cell-type ferroelectric random access memory (FRAM) which consists of an array of metal-ferroelectric-semiconductor field effect transistors (MFSFETs) is proposed. In order to minimize the interference problem in the “write/read” operation, use of a silicon-on-insulator (SOI) structure is proposed, as well as optimizing the write and read methods partly using experimental results for ferroelectric capacitors. A key method for avoiding the interference problem is to generate a compensation pulse with a 1/3 amplitude and opposite polarity in the next timing to each write pulse. It is concluded from these considerations that the proposed structure is promising for use as a single-transistor-cell-type FRAM, if the electrical properties of a ferroelectric film on a Si substrate is as good as that on a Pt electrode.
GaAs/AlGaAs/InGaAs Vertical Triple Barrier Single Electron Transistors
Authors: Austing David Guy , Takashi Honda Takashi Honda , Seigo Tarucha Seigo Tarucha
Published: October 2002

A gated vertical sub-micron triple barrier structure with undoped Al0.22Ga0.78As barriers and I
n
0.05
G
a
0.95
A
s wells is used to study the properties of two weakly coupled quantum dots containing just a few electrons. We find that the conductance peaks become sparse as the ac excitation voltage is decreased when there is considerable mismatch between the ladders of energy levels in the two dot. Concurrently, the diamond shaped regions of Coulomb blockade are strongly disrupted. On the other hand, when the mismatch between energy levels is “small”–comparable to or less than the level width–the evolution of conductance peaks in pairs in the presence of a magnetic field applied parallel to the tunneling current is clearly seen and this can be related to spin-degeneracy.
Investigation of Polyimide Thin Films Deposited by Ionized Cluster Beam
Authors: Hong Chang Eui , Kim Nam Young , Yoon Sang Yeol Kim Hyoung Seek , Kim Ki Won , Chung Nam Whang Chung Nam Whang
Published: October 2002

Ionized cluster beam deposition (ICBD) has been employed to fabricate high-purity crystalline polyimide (PI) thin films. X-ray photoemission spectroscopy, transmission electron microscopy, glancing-incidence X-ray diffraction, and atomic force microscopy studies show that the structure and properties of PI films are very sensitive to the deposition conditions such as the cluster acceleration voltage (V
a) and the ionization voltage (V
e). At optimum conditions of V
a = 800 V and V
e = 200 V, the PI films have a maximum imidization, negligible amount of impurity (∼1% of isoimide), and a good crystalline structure probably due to the high surface migration energy, and the surface cleaning effect. It was also found that the surface morphology and the adhesion properties could be improved by ICBD.
Preparation and Characterization of Iridium Oxide Thin Films Grown by DC Reactive Sputtering
Authors: Cho Hag-Ju , Horii Hideki , Hwang Cheol Seong , Kim Jin-Won , Kang Chang Seok , Lee Byoung Taek , Lee Sang In , Young Bum Koh Young Bum Koh , Moon Yong Lee Moon Yong Lee
Published: October 2002

Iridium oxide ( IrO2) thin films were successfully grown by a DC magnetron reactive sputtering method. It was found that the crystalline nature and morphology of IrO2 films were strongly dependent on the oxygen partial pressure, total pressure and growth temperature. The growth of IrO2 is well explained by the generic curve for the total pressure as a function of O2 content. The films showed good barrier performance between Pt and poly-Si up to 750° C. A 40-nm-thick Ba0.5Sr0.5TiO3 film was grown by RF magnetron sputtering on the Pt/IrO2/poly-Si electrode. The leakage current density and dielectric constant of a Pt/Ba0.5Sr0.5TiO3/Pt capacitor on the IrO2/poly-Si electrode were comparable to those of the capacitor on a SiO2/Si substrate. However, an additional ohmic layer was required to prevent the formation of a SiO2 layer between the IrO2 and poly-Si.
Characteristics of AlGaAs/AlGaAs Interface Regrown Using In-Situ Low-Temperature H2 Annealing in Metalorganic Vapor Phase Epitaxy
Authors: Shu Gotoh Shu Gotoh , Hideaki Horikawa Hideaki Horikawa
Published: October 2002

Characteristics of an AlGaAs/AlGaAs interface regrown using a new thermal treatment method, in-situ low-temperature H2 annealing (LTHA), are studied by photoluminescence (PL) measurement, secondary ion mass spectroscopy (SIMS) and cross-sectional transmission electron microscopy (TEM). In LTHA, annealing in H2 ambient at temperatures below 400° C is carried out before metalorganic vapor phase epitaxial (MOVPE) regrowth. LTHA markedly restores the spectrum of PL from AlGaAs/GaAs quantum wells near the regrown interface, indicating that the initial air-exposed AlGaAs surface states are reduced. SIMS and TEM results reveal that the oxides are removed from an initial air-exposed AlGaAs surface during LTHA, and the atomically ordered and stoichiometric AlGaAs/AlGaAs regions with a width of 30–70 Å appear along the regrown interface, proving that LTHA possesses a surface cleaning effect even at such low temperatures.
Measurement of Semiconductor Heterojunction Band Discontinuities Using Free Electron Laser
Authors: Nishi Kazuhisa , Ohyama Hideaki , Suzuki Toshiji , Tsuneo Mitsuyu Tsuneo Mitsuyu , Takio Tomimasu Takio Tomimasu
Published: October 2002

Measurements of the band discontinuity of semiconductor heterojunctions was carried out using the free electron laser internal photoemission (FEL-IPE) technique. This technique is based on photocurrent spectroscopy utilizing the tunability and intense peak power of the FEL operative in the infrared range. We found that there is a photocurrent threshold in the IPE spectrum of the ZnSe/GaAs and GaAlAs/GaAs heterojunctions which can be identified as the band discontinuity.
InGaP/GaAs Sub-Square-Micron Emitter HBT with fmax > 100 GHz
Authors: Hirata Koji , Tanoue Tomonori , Masuda Hiroshi , Uchiyama Hiroyuki , Terano Akihisa
Published: October 2002

InGaP/GaAs heterojunction bipolar transistors (HBTs) with a sub-square-micron emitter have been fabricated using a novel self-aligned emitter etching process with low damage and good lateral and vertical controllability. HBTs with an emitter size of 0.4×1.7 µ m fabricated using this process exhibited a current gain of 44 which is comparable to that of AlGaAs/GaAs HBTs. Furthermore, the HBTs exhibited excellent microwave performance. For an HBT with an emitter size of 0.4×2.2 µ m, a cutoff frequency (f
T) of 55 GHz and a maximum oscillation frequency (f
max) of 100 GHz were reached at a collector current (I
C) as low as 1.0 mA, and a peak f
T of 62 GHz and a peak f
max of 105 GHz were obtained at I
C=2.3 mA. As far as we know, this f
max is the highest reported for GaAs-based HBTs with an emitter area of less than 1 µ m2. This process is thus promising for fabrication of high-speed HBT ICs with low power consumption.
Capacitance-Voltage Behavior of Insulated Gate InGaAs HEMT Capacitors Having Silicon Interface Control Layer
Authors: Dohmae Yasuhiro , Suzuki Satoshi , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

Basic insulated gate HEMT (IGHEMT) capacitors with and without a Si interface control layer (ICL) were fabricated, and their capacitance-voltage (C-V) characteristics were compared in detail (103–109 Hz, 50 K–300 K). The basic IGHEMT capacitors with Si-ICL were found to exhibit an unexpectedly large frequency dispersion of capacitance. By performing detailed low-temperature measurements, it was found that the observed frequency dispersion of capacitance was due not to the interface states but to the rate limitation of the carrier supply, and the nearly ideal nature of an IGHEMT capacitor with Si-ICL was confirmed.
Carrier Transport in Nanodevices
Authors: Ferry David K. , Akis Richard , Udipi Sujeeth , Vasileska Dragica , Pivin David P. , Connolly Jr. , Bird Jonathan P. , Ishibashi Koji , Aoyagi Yoshinobu , Sugano Takuo , Ochiai Yuichi
Published: October 2002

Future VLSI scaling realization of gate lengths is expected to 70 nm and below. While we do not know all the underlying physics, we are beginning to understand some limiting factors, which include quantum transport, in these structures. The discrete nature of impurities, the fact that devices have critical lengths comparable to their coherence lengths, and size quantization will all be important in these structures. These phenomena will lead to pockets of charge, which will appear as coupled quantum dots in the device transport. We review some of the physics of these dots.
Noise Parameter Extraction of a GaAs MESFET with Monte-Carlo Simulation
Authors: Jaemyoung Baek Jaemyoung Baek , Youngse Kwon Youngse Kwon , Songcheol Hong Songcheol Hong
Published: October 2002

All of the noise parameters of a GaAs metal-semiconductor field-fffect transistor (MESFET) are extracted using 2-dimensional Monte-Carlo simulation for the first time. The general procedure for extracting the noise parameters is presented. The spectrums and correlations of the input-equivalent noise-voltage and noise-current sources are calculated. The y parameters of a GaAs MESFET are also extracted to obtain noise parameters and to analyze device characteristics for the first time.
Increased Electron Concentration in InAs/AlGaSb Heterostructures Using a Si Planar Doped Ultrathin InAs Quantum Well
Authors: Sasa Shigehiko , Yamamoto Yoshitaka , Izumiya Satoshi , Yano Mitsuaki , Yoshio Iwai Yoshio Iwai , Masataka Inoue Masataka Inoue
Published: October 2002

We demonstrate that the two-dimensional electron gas concentration in an InAs/AlGaSb heterostructure can be greatly increased by introducing a Si planar-doped ultrathin InAs quantum well (QW) sandwiched between AlSb barriers as an additional electron supplying layer in a well controlled fashion. With the Si planar-doped QW formed 8 nm below the channel layer, the sheet electron concentration increased up to 4.5×1012 cm-2 with an electron mobility of 4×104 cm2/ Vs at 77 K. Shubnikov-de Haas measurements revealed that only two subbands are occupied, even for heavily doped samples. The energy separation between the first and the second subbands is as large as 100 meV, indicating a strong electron confinement in the selectively doped InAs/AlGaSb heterostructures.
Reduction of Aspect Ratio in 650 nm-Band Self-Sustained-Pulsing Lasers with Saturable-Absorbing Layer
Authors: Adachi Hideto , Kidoguchi Isao , Fukuhisa Toshiya , Tanaka Kiyotake , Masaya Mannoh Masaya Mannoh , Akira Takamori Akira Takamori
Published: October 2002

650 nm-band self-pulsing lasers which exhibit an extremely low laser beam profile aspect ratio (2.6) and a small astigmatism (2 µm) were successfully demonstrated by optimizing the design of the layer structure. Low-noise self-pulsing lasers have been developed as a light source for optical disc systems. In the case of mounting the lasers on optical systems, a low aspect ratio and a small astigmatism are required in order to realize high optical coupling efficiency and good optical focusing characteristics. In this paper, we report a reduction of the aspect ratio while maintaining a small astigmatism in self-pulsing AlGaInP lasers with a saturable absorbing (SA) layer by optimizing the optical confinement and compressive strain in the SA layer. Simultaneously, a very low intensity noise characteristic up to 50° C was confirmed by stable self-sustained pulsation characteristics.
High-Power 650-nm-Band AlGaInP Visible Laser Diodes Fabricated by Reactive Ion Beam Etching Using Cl2/N2Mixture
Authors: Kidoguchi Isao , Adachi Hideto , Tanaka Kiyotake , Fukuhisa Toshiya , Masaya Mannoh Masaya Mannoh , Akira Takamori Akira Takamori
Published: October 2002

High-power 650-nm-band AlGaInP visible laser diodes having stable fundamental-transverse-mode at high temperatures were produced using electron cyclotron resonance reactive ion beam etching (ECR-RIBE). Epilayers were etched using a Cl2/N2mixture gas, resulting in very smooth surfaces and symmetric laser mesas. Lasers that are 700-µm-long and 6%/80% coated were fabricated. The typical threshold current of these devices was as low as 46 mA at room temperature, and a stable fundamental-mode operation over 30 mW is obtained up to 70°C. The lasers operated for over 1000 h at 60°C under an output power of 25 mW, and their degradation rate was as low as lasers fabricated by the ordinary wet etching process.
GaInAs/AlGaInAs Semiconductor Lasers with AlAs Oxide Current Confinement Structure
Authors: Ohnoki Noriyuki , Hatori Nobuaki , Mizutani Akimasa , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: October 2002

An AlAs oxide current confinement structure based on an InP substrate has been demonstrated for the first time to realize low threshold long wavelength surface emitting lasers. The oxidized width is confirmed to be well controllable by choosing suitable oxidation time and temperature. We fabricated an metalorganic chemical vapor deposition (MOCVD) grown 1.65-µ m wavelength GaInAs/AlGaInAs multiple quantum well (MQW) edge emitting laser with the AlAs-oxide confinement structure of 3 µ m-wide and 15 µ m-wide windows. A 3 µ m-wide window oxidized laser having uncoated facets exhibits a threshold of 51 mA for device with a 800-µ m-long cavity. We have obtained a threshold current density of 1.3 kA/cm2 for 3 µ m-wide window devices. The results show a potential application of the proposed structure for low threshold long-wavelength surface emitting lasers.
New Realization Method for Three-Dimensional Photonic Crystal in the Optical Wavelength Region: Experimental Consideration
Authors: Noritsugu Yamamoto Noritsugu Yamamoto , Susumu Noda Susumu Noda , Akio Sasaki Akio Sasaki
Published: October 2002

We experimentally investigate the feasibility of a realization method for the three-dimensional photonic crystal in the optical wavelength region. Micromachining techniques of dry-etching, wafer-bonding and laser beam diffraction pattern observation techniques are utilized. Each process is investigated using an AlGaAs/GaAs semiconductor system, and the feasibility of this method is successfully demonstrated for a structure having a photonic bandgap in the 10 µm wavelength region.
Blue-Green Stimulated Emission in Lattice-Matched ZnHgSSe/ZnSSe Double Heterostructures by Optical Pumping
Authors: Yumiko Eguchi Yumiko Eguchi , Kazuhiko Hara Kazuhiko Hara , Kazunari Yamamoto Kazunari Yamamoto , Shigeru Haneda Shigeru Haneda , Hiroshi Kukimoto Hiroshi Kukimoto , Hiro Munekata Hiro Munekata
Published: October 2002

The fabrication and characterization of ZnHgSSe/ZnSSe double heterostructure (DH) laser structures, lattice-matched on GaAs (100) substrates, are described. The structures were grown by molecular beam epitaxy with a ZnHgSSe active layer which includes a small amount of Hg (∼1.2%). The occurrence of stimulated emission was observed at 77 K in the blue-green wavelength region by optically pumping the DH structures.
New Resist Technologies for 0.25-µ m Wiring Pattern Fabrication with KrF Lithography
Authors: Kawai Yoshio , Otaka Akihiro , Tanaka Akinobu , Nakamura Jiro , Sakuma Kazuhito , Tadahito Matsuda Tadahito Matsuda , Yutaka Sakakibara Yutaka Sakakibara
Published: October 2002

A new resist system composed of a chemically amplified positive resist and an organic base designed to be compatible with an acid generator has been developed to improve resolution on TiN films. It was clarified that the non-uniformity of the organic base like the acid generator in the resist film significantly contributes to high resist performance. A new hardening method has also been developed to improve the thermal stability of resist patterns for metal etching. Using the new technologies, 0.25-µ m line and space (l&s) resolution on TiN films and highly accurate metal etching have been achieved.
Wave Propagation Characteristics of a 70 GHz Imageguide Consisting of a Transversely Magnetized p-InSb Slab with Light Irradiation
Authors: Shinichi Yodokawa Shinichi Yodokawa , Tetsuo Obunai Tetsuo Obunai
Published: October 2002

Wave propagation characteristics of a 70 GHz imageguide consisting of a transversely magnetized p-InSb slab have been studied experimentally at 77 K. The results indicate the possibility of using p-InSb as a component of dielectric waveguides. It is also shown that the propagation characteristics of this imageguide can be controlled by light irradiation.
Improvement of Photosensitivity in Fluorenone Bisazo Pigment/Poly(Methyl Phenyl Silane) Layered Device
Authors: Minoru Umeda Minoru Umeda
Published: October 2002

The low photocarrier generation efficiency of a layered device consisting of an azo-pigment-based carrier generation layer (CGL) and a poly(methyl phenyl silane) (PMPS) layer was investigated. We found that the electron transfer efficiency to generate geminate hole-electron pairs, which are the precursor of free carriers, was quite low, whereas electron transfer efficiently occurs in a layered system using a small carrier transport molecule instead of the large PMPS. These results were explained in terms of the number of electron transfer sites created by the molecular penetration during the overcoating operation. A high electron transfer efficiency was observed in a single layer of mixed PMPS and azo pigment. According to these results, a high carrier generation efficiency has been demonstrated for the layered device using the azo pigment with PMPS in the CGL and only PMPS in the overlayer.
Mechanical Properties of a Gd2SiO5 Single Crystal
Authors: Kurashige Kazuhisa , Kurata Yasushi , Hiroyuki Ishibashi Hiroyuki Ishibashi , Kenzo Susa Kenzo Susa
Published: October 2002

A Gd2SiO5 single crystal ingot tends to crack during Czochralski growth. In order to perform a stress analysis of the ingot, a complete set of elastic constants of the crystal was measured using ultrasonic pulse method. Critical values of tensile and shear stresses were also measured using the three-point loading test. The critical value of the shear stress in the (010) plane is less than 1/10 of that in other crystallographic planes, and an excess shear stress in the (010) plane is genetated the easiest. This excess stress induces dislocations concentrated in the (100) plane during growth and develops residual stress during the cooling process, giving rise to the occurrence of cracking during the growth as well as during the postprocessing.
Optical Absorption and Photoluminescence Properties of Pb(I, Br)-Based Two-Dimensional Layered Perovskite
Authors: Nobuaki Kitazawa Nobuaki Kitazawa
Published: October 2002

The influence of ( C6H5C2H4NH3)2Pb(Br

x

I4-
x

) concentration on the formation of mixed crystals and optical properties of these materials was investigated. Thin films of microcrystalline ( C6H5C2H4NH3)2Pb(Br

x

I4-
x

) were prepared by the spin-coating method using different concentrations of DMF solutions. Macroscopic inhomogeneity of the composition due to the precipitation of undesired phases could be suppressed by controlling the ( C6H5C2H4NH3)2Pb(Br

x

I4-
x

) concentration. These films showed strong exciton absorption with large (250–430 meV) binding energy due to both the quantum and dielectric confinement effect. Replacing I with Br made it possible to shift the exciton band to the blue region; however, photoluminescence from the mixed crystals gradually broadened with increasing the Br content.
Effect of Oxygen Ion Energy and Annealing in Formation of Tin Oxide Thin Films
Authors: Song Seok-Kyun , Choi Won-Kook , Cho Jun-Sik , Jung Hyung-Jin , Choi Dongsoo , Lee Jeong-Yong , Baik Hong-Koo , Seok-Keun Koh Seok-Keun Koh
Published: October 2002

Tin oxide ( SnO

x

) thin films were deposited by ion-assisted deposition (IAD) at various ion beam voltages (V
I) onto amorphous SiO2/Si substrate at room temperature. Tin oxide thin films with nonstoichiometric/stoichiometric composition were fabricated. The as-deposited SnO

x

films were mostly amorphous, but they exhibited various degrees of crystallinity and fine grain size after annealing at 500° C for 1 h in air. The annealed film deposited using an ion beam energy (E
I) of 300 eV showed a preferred orientation along the SnO2 (110) plane. The preferred orientation changed to SnO2 (002) for film 1000 (the annealed film deposited with E
I=1000 eV) through an amorphous intermediate structure of film 500 (the annealed film deposited with E
I=500 eV). X-ray photoelectron spectroscopy study showed that the main Sn3d peaks in all samples were similar to the binding energy of Sn4+ and the atomic ratios for all the films were higher than 1.51. For the film grown under an average energy of 123 eV/atom, the refractive index was 2.0 and the estimated porosity was 5.2% smaller than that of the other films.