bluuebunny/crossref_metadata_2025 huggingface dataset:
Double SOI Structures and Device Applications with Heteroepitaxial Al2O3 and Si
Authors: Ishida Makoto , Lee Young-Tae , Higashino Touru , Seo Heedon , Tetsuro Nakamura Tetsuro Nakamura
Published: October 2002

Growth and properties of a double SOI (Si-on-insulator) structure, which consists of epitaxial Al2O3 as an insulator layer and epitaxial Si layers, are discussed. LP-CVD (low-pressure chemical vapor deposition) for γ- Al2 O3(100) growth on Si(100) substrates was combined with Si CVD through a sample exchanging chamber with reflection high-energy electron diffraction (RHEED) and quadrupole mass spectrometer (QMS) to grow successively and analyzed without exposure to air. These epitaxial multilayers were characterized by RHEED, Auger electron spectroscopy (AES), cross-sectional transmissin electron microscopy (TEM) and etching method. Metal-oxide-semiconductor (MOS) field effect transistor (FET) mobility was also studied on each Si layer. Both Si layers showed similar defect density and mobility. This double SOI structure was applied to fabrication of a pressure sensor for use at elevated temperatures up to 300° C.
Extremely High Selective Etching of Porous Si for Single Etch-Stop Bond-and-Etch-Back Silicon-on-Insulator
Authors: Sakaguchi Kiyofumi , Sato Nobuhiko , Yamagata Kenji , Fujiyama Yasutomo , Takao Yonehara Takao Yonehara
Published: October 2002

The etching characteristics of porous Si in comparison with bulk Si have been investigated for the ultra thin film (UTF) single etch-stop bond-and-etch-back silicon-on-insulator (BESOI). It is found out that porous Si can be selectively etched exclusively by a mixture of HF, H2O2 and H2O due to the structure-sensitive mechanism, that is, inner reaction by capillary-induced penetration of the etchant into the pores followed by collapsing the Si columns. This extremely high etching selectivity reaches as large as 105, which results in excellent SOI layer thickness variation of less than 7% across 5-inch SOI wafers with sub-µ m and sub-100-nm thicknesses.
Void-Free Bonded SOI Substrates for High-Voltage, High-Current Vertical DMOS-Type Power ICs
Authors: Hamajima Tomohiro , Kobayashi Kenya , Kikuchi Hiroaki , Okonogi Kensuke , Arai Kenichi , Ninomiya Yasuhito , Takahashi Mitsuasa
Published: October 2002

New isolated structures for intelligent power ICs were developed using a wafer bonding technique. These structures have partial buried oxide films for dielectric isolation and buried poly-Si layers for wafer bonding. In this bonding technique, bonding surfaces are a poly-Si layer and a crystalline silicon surface; this combination of bonding surfaces leads to void-free bonding. The electrical perfection of the vertical output device in the new structure was obtained by diffusing antimony into the poly-Si layer. These results indicate that intelligent power ICs can be manufactured by using the new structure.
Measurements of the Breakdown Voltage of the Lateral Insulated Gate Bipolar Transistor on the Silicon-on-Insulator Film with Varying Implantation Doses for the N-Buffer Layer
Authors: Sumida Hitoshi , Atsuo Hirabayashi Atsuo Hirabayashi
Published: October 2002

The blocking capability of the lateral insulated gate bipolar transistor (LIGBT) fabricated on the silicon-on-insulator (SOI) film is investigated experimentally with varying implantation doses for the n-buffer layer. This note shows the experimental results on the breakdown voltage at room temperature and 125° C. The blocking capability of the LIGBT on the SOI film depends strongly on the implantation dose for the n-buffer layer.
A Trench-Gate Silicon-on-Insulator Lateral Insulated Gate Bipolar Transistor with the p+ Cathode Well
Authors: Lee Byeong-Hoon , Yun Chong-Man , Byeon Dae-Seok , Han Min-Koo , Choi Yearn-Ik
Published: October 2002

A trench-gate silicon-on-insulator (SOI) lateral insulated gate bipolar transistor (LIGBT) with the p+ cathode well is proposed to improve the latch-up characteristics, and the improved characteristics are verified numerically by MEDICI simulation. It is found that the trench-gate SOI LIGBT exhibits at least 6 times larger latch-up capability than the conventional devices. The enhanced latch-up capability of the trench-gate SOI LIGBT is obtained due to the fact that the hole current in the device bypasses the resistance of the p body region which is the source of the latch-up and reaches the cathode via the p+ cathode well.
Computer Simulation and Measurement of Capacitance-Voltage Characteristics in Quantum Wire Devices of Trench-Oxide MOS Structure
Authors: Tsukui Tetsuya , Shunri Oda Shunri Oda
Published: October 2002

We have proposed the trench-oxide metal-oxide-semiconductor (MOS) structure as a novel quantum wire device. In this paper we present results of computer simulation based on a self-consistent system and calculated quantized electron distribution and capacitance-voltage (C-V) characteristics. We have also fabricated the quantum wire MOS structure using electron beam lithography and electron cyclotron resonance reactive ion etching method and carried out measurements of C-V characteristics at 0.55 K.
Possible evidence of one-dimensional quantum effect is obtained for the first time from C-V measurements using the 28 nm-wide trench-oxide structure.
Suppression of Leakage Current in n-Channel Polysilicon Thin-Film Transistors Using NH3 Annealing
Authors: Choi Deuk-Sung , Hur Sung-Hoi , Yang Gi-Young , Han Chul-Hi , Choong-Ki Kim Choong-Ki Kim
Published: October 2002

The effect of NH3 annealing on polysilicon thin-film transistors (poly-Si TFT's) is investigated. Substantial reduction of the off-state leakage current in self-aligned n-channel poly-Si TFT's is achieved upon NH3 annealing without degradation of on-state characteristics. NH3 annealing is believed to generate positive fixed charges in the gate oxide near the source and drain junction during NH3 annealing. These positive fixed oxide charges reduce the electric field in the drain junction, resulting in the reduction of the leakage current. NH3 annealing can be applied effectively to fabricate high-performance self-aligned poly-Si TFT's.
New P-MOSFET Hot-Carrier Degradation Model for Bi-Directional Operation
Authors: Shimizu Satoshi , Tanizawa Motoaki , Kusunoki Shigeru , Inuishi Masahide , Natsuro Tsubouchi Natsuro Tsubouchi
Published: October 2002

It has been recognized that the building in reliability for hot-carrier is important in submicrometer p-MOSFET's as well as n-MOSFET's for use in the design of ULSI's. Therefore in this paper, we introduce a new hot-carrier degradation model of p-MOSFET's for bi-directional operation, aiming at constructing a new reliability simulator to cope with various operation modes. This model is based on the trap-induced barrier lowering (TIBL), the channel length modulation (CLM) due to electron traps in the oxide, and the mobility modulation (MM) due to interface state generation. By extracting these physically related parameters from transistor characteristics after hot-carrier injection in addition to extracting transistor model parameters before the injection, the hot-carrier degradation can be predicted not only in the linear and saturation regions but also in the forward and reverse operation modes.
Ultra Low-Temperature Growth of High-Integrity Thin Gate Oxide Films by Low-Energy Ion-Assisted Oxidation
Authors: Watanabe Jinzo , Kawai Yasuaki , Konishi Nobuhiro , Tadahiro Ohmi Tadahiro Ohmi
Published: October 2002

High integrity thin gate oxide films have been grown at a temperature as low as 450° C by direct oxidation of silicon. The bombardment of the silicon surface by low energy ions of argon and oxygen mixed plasma is utilized to activate the oxidation process. Dielectric breakdown field intensity of the oxide film of 12 MV/cm is obtained by the MOS capacitor evaluation. The precise control of the bombarding energy is essential in achieving the high-integrity thin gate oxide films.
Low-Loss Schottky Rectifier Utilizing Trench Sidewall as Junction-Barrier-Controlled Schottky Contact
Authors: Kim Han-Soo , Kim Seong-Dong , Han Min-Koo , Choi Yearn-Ik
Published: October 2002

A novel junction barrier contolled Schottky (JBS) rectifier structure, which has increased the Schottky contact area by utilizing the trench sidewall, has been proposed. The proposed device consists of a JBS rectifier positioned vertically along the trench sidewall as well as laterally along the surface. The additional sidewall Schottky contact reduces the forward voltage drop by enlarging the Schottky active area. The new trench structure shifts the peak electric field from Schottky contact surface to the silicon bulk and the leakage current by the barrier height lowering effect is decreased. An intensive 2-dimensional numerical simulation by MEDICI shows that the leakage current of the trenched JBS rectifier is less than 60% of that of the conventional Schottky rectifier, while the forward voltage drop of the trenched JBS rectifier is almost the same as that of the conventional Schottky rectifier.
Analytical Calculation of Subthreshold Slope Increase in Short-Channel MOSFET's by Taking Drift Component into Account
Authors: Biesemans Serge , Kristin De Meyer Kristin De Meyer
Published: October 2002

Modeling of the subthreshold slope S and the threshold voltage V
T has been done based on the fundamental equations governing the metal-oxide-semiconductor field-effect transistor (MOSFET). Taking the drift as well as the diffusion component of the current into account resulted in a physically complete description of the short-channel effect. The method calculates the potential from the 2D Poisson equation, the minority carrier density from the continuity equation and the weak inversion current density from the drift-diffusion model. As an example, the detailed calculation of the S factor is given. The new closed-form formula for S includes the L dependence in an accurate way.
Very Low Temperature Deposition of Polycrystalline Si Films Fabricated by Hydrogen Dilution with Electron Cyclotron Resonance Chemical Vapor Deposition
Authors: Wang Kun-Chih , Cheng Kuan-Lun , Jiang Yeu-Long , Yew Tri-Rung , Huey-Liang Hwang Huey-Liang Hwang
Published: October 2002

Characteristics of polycrystalline silicon films deposited both on SiO2 and Corning 7059 glass substrates are presented in this paper. The silicon films were deposited by a hydrogen dilution method using electron cyclotron resonance chemical vapor deposition at 250° C without any thermal or laser annealing. The hydrogen dilution ratio was between 90% and 99%. The geometric configuration and surface morphology of polycrystalline silicon films were studied by atomic force microscopy. The largest grain size of the deposited silicon films, identified by plan-view transmission electron microscopy dark-field imaging, was about 1 µ m. From Raman spectrum, the crystalline fraction of polycrystalline silicon films was identified to be nearly 100%. The polycrystalline silicon was found to be preferentially <111>- and <110>-oriented, from the X-ray diffraction pattern.
Element Specific Diagnosis Using Microwave Reflection Photoconductive Decay
Authors: Köster Ludwig , Blöchl Peter , Laszlo Fabry Laszlo Fabry
Published: October 2002

Applying element specific drive-in treatments before the microwave reflection photo-conductive decay (µ-PCD) analysis recombination centers can be assigned to metallic contaminants, which have a degrading influence on the recombination lifetime (τ). Element specific information can further be obtained by variation of the injection level (injection level spectroscopy). Comparison of measured and calculated lifetimes using the Schockley-Read-Hall-recombination model allows the identification of Fe as lifetime Killer. Correlating the lifetime with sample thickness data provides the possibility of absolute lifetime calibration.
The Relationship between Photoconduction Effects and Luminescent Properties of Porous Silicon
Authors: Ozaki Tsuyoshi , Oguro Tsuyoshi , Koyama Hideki , Nobuyoshi Koshida Nobuyoshi Koshida
Published: October 2002

The luminescent properties of porous silicon (PS) have been studied in terms of its electrical properties and photo-conduction effects. It is shown that the electrical conduction mode of the PS layers at low temperatures below about 100 K is dominated by tunneling either in the dark or under illumination, and that the photoconduction spectra of efficiently luminescent PS almost coincide with the photoluminescence (PL) excitation spectra. The implication is that the electronic excitation for both photoconduction (PC) and PL occurs in the same place. Effects of electric field on the PL characteristics of PS are also studied in relation to PC effects. The experimental data demonstrate that the degree of electric-field PL quenching corresponds to the net PC current induced during PL excitation. These observations are discussed in relation to the visible luminescence mechanism.
Interface States for Si-Based MOS Devices with an Ultrathin Oxide Layer: X-Ray Photoelectron Spectroscopic Measurements under Biases
Authors: Kobayashi Hikaru , Yamashita Yoshiyuki , Mori Toshio , Nakato Yoshihiro , Komeda Tadahiro , Nishioka Yasushiro
Published: October 2002

Energy distributions of interface states for <30-Å-thick Pt/ 25∼35-Å-thick silicon oxide/ n-Si(100)> metal-oxide-semiconductor (MOS) devices have been obtained from measurements of X-ray photoelectron (XPS) spectra under biases. Upon applying bias voltages, the substrate Si(2p) peak is shifted because of a change in the occupancy of interface states by electrons, inducing a change in the potential drop across the silicon oxide layer. Devices with a native oxide layer have high interface state density near the midgap, which is attributed to isolated dangling-bond states. For MOS devices with a thermal oxide layer grown at 550° C in a wet-oxygen atmosphere, the interface states have two density maxima, one below and the other above the midgap. For devices with a thermal oxide layer formed at 700° C in wet oxygen, two density maxima of the interface states are also observed with reduced density.
A Novel Al/TiN/CVD-W Structure to Eliminate Resistance Anomaly in Deep Submicron Al/CVD-W Interconnects
Authors: Sekiguchi Mitsuru , Fujii Toyokazu , Yamanaka Michinari , Masanori Fukumoto Masanori Fukumoto
Published: October 2002

The sheet resistance increase of Al/chemical vapor deposition (CVD)-W interconnects after low-temperature annealing has been investigated. Anomalous sheet resistance increase depending on the linewidth in sub-half-micron Al-Si-Cu/CVD-W lines after 450° C annealing is found for the first time. The sheet resistance increase of the Al/CVD-W lines becomes larger for narrower linewidth after annealing. It is considered that this anomalous sheet resistance increase is due to more nonuniform high-resistivity WAl12 formation in the narrower lines. Using a TiN interlayer to eliminate WAl12 formation, sub-half-micron lines of a new Al-Si-Cu/TiN/CVD-W structure have demonstrated sufficiently low line resistance even after 450° C annealing for 300 min and exhibited 6 times longer electromigration (EM) lifetime compared with the previous Al-Si-Cu/CVD-W structure. This longer EM lifetime is also attributed to the suppression of WAl12 formation. This structure is one of the most promising interconnect structures for realizing sub-half-micron interconnects in future ULSIs.
TiN/TiSi2 Formation Using TiNx Layer and Its Feasibilities in ULSI
Authors: Byun Jeong Soo , Kim Chang Reol , Rha Kwan Goo , Kim Jae Jeong , Woo Shik Kim Woo Shik Kim
Published: October 2002

A new technique for the formation of the TiN/TiSi2 bilayer using a TiN
x
layer was described. The TiN
x
layer was deposited by sputtering in a mixed gas atmosphere of argon and nitrogen, wherein the concentration of nitrogen was controlled to be lower than that required in the formation of stoichiometric TiN.
The nitrogen atoms in the Ti matrix relaxed the mechanical stress of the deposited film and also limited the number of Ti atoms available for the interaction with the Si substrate (i.e., silicidation reaction). Upon thermal annealing, TiN
x
changed to the bilayer structure of TiN/TiSi2, in which the thickness of the overlying TiN was so great that only a rather thin TiSi2 was formed between TiN and the Si substrate. Moreover, TiN had the (111) texture, and TiSi2 formed on the (100)Si substrate was found to show well-aligned epitaxial properties with an extremely uniform thickness.
Effects of Insulator Surface Roughness on Al-Alloy Film Crystallographic Orientation in Al-Alloy/Ti/Insulator Structure
Authors: Onoda Hiroshi , Touchi Kenshin , Keiichi Hashimoto Keiichi Hashimoto
Published: October 2002

Effects of insulator surface roughness on the overlying aluminum-alloy film crystallographic orientation in Al-alloy/Ti/insulator layered structures have been studied. Tetra-ethyl-ortho-silicate- O3 ( TEOS-O3) based SiO2 and its chemical-mechanical-polished (CMP) films have been used in order to change the surface roughness of underlying insulators. Ti(002) and (011) peak intensities in X-ray diffraction (XRD) spectra increase when the underlying insulator has a smooth surface, and this orientation change in Ti causes Al (111) peak intensity more than two orders higher on a very smooth surface of CMP TEOS-O3 SiO2 film, particularly in Al high-temperature sputtering, compared to that on non-CMP TEOS-O3 SiO2 film. This crystallographic orientation change results in a large difference in the electromigration performance in high-temperature-sputtered Al alloy/Ti layered metal line.
Band Offset Dependance on Impact Ionization Rates in InAlGaAs Staircase Avalanche Photodiodes
Authors: Tsuji Masayoshi , Makita Kikuo , Watanabe Isao , Kenko Taguchi Kenko Taguchi
Published: October 2002

Electron (α) and hole (β) impact ionization rates in InAlGaAs staircase avalanche photodiodes with different sawtooth conduction band offset (ΔE
c) values were determined using photomultiplication measurements. The α/β ratio was found to be enhanced from 3.6 to 5.1 by increasing ΔE
c from 0.3 eV to 0.5 eV, the largest value in this system, under a 470 kV/cm electric field. Internal electric field and hole cooling effects in the distinct sawtooth band structure were studied in relation to the obtained data.
Sudden Drop of Dissipation in Field-Coupled Quantum Dot Resistors
Authors: Yamaguchi Fumiko , Kiyoshi Kawamura Kiyoshi Kawamura , Alfred Hü Alfred Hü
Published: October 2002

We propose a novel device where energy loss accompanied by current flow through a resistor is recovered, and therefore Joule heat production is exclusively low. This “energy-recovery effect" is caused by dynamical transition due to electronic coherent interference, namely Coulomb interaction within specially designed coupled quantum dots. We study the characteristics of this device as a resistor. We find a sudden drop of energy dissipation due to current flow as a function of electrochemical potential of the reservoir which is coupled to the quantum dots. In addition, we show that resistance of the device depends on the strength of the Coulomb interaction.
Mercury Ion Density in Low-Pressure Ar-Hg Discharge Plasma Used for Liquid Crystal Display Backlighting
Authors: Goto Miki , Toshihiko Arai Toshihiko Arai
Published: October 2002

The mercury ion density in the tube axis of a narrow low-pressure Ar-Hg discharge lamp was measured with a modified absorption method. The electron density was measured with a probe method. The positive column of a discharge system is studied under the following conditions: Ar pressure 400 Pa (3 Torr); tube radius 2 mm; cold-spot temperature 0-80° C and discharge current 20 mA.
It is shown that mercury molecular ion density is determined by combining the modified absorption method with the probe method.
Influence of Sr Content on Tl-Ba-Sr-Ca-Cu-O Superconducting Thin Films Prepared by the Mist Microwave-Plasma Chemical Vapor Deposition Method
Authors: Takahashi Naoyuki , Koukitu Akinori , Hisashi Seki Hisashi Seki
Published: October 2002

Superconducting thin films of a Tl-Ba-Ca-Cu-O (TBCCO) system were prepared on single-crystal MgO(100) substrates by the mist microwave-plasma chemical vapor deposition method, and the influence of the substitution of Sr for Ba for the formation of the superconducting phases in TBCCO systems was investigated. The crystallographic transformation was caused by changing the ratio of Sr to Ba ( x=Sr/(Ba+Sr)). In the case of the Tl(Ba, Sr)-Ca-Cu-O system, the high-T

c
phase (2223 phase) more easily was obtained as a single phase compared to the Tl-Ba-Ca-Cu-O and Tl-Sr-Ca-Cu-O systems.
Silicon Delta Doping of GaInP Grown by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Wang Chien-Jen , Wu Janne-Wha , Chan Shih-Hsiung , Chang Chun-Yen , Sze Simon Min , Feng Ming-Shiann
Published: October 2002

Silicon delta doping in GaInP material has been demonstrated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) and characterized by Hall-effect and capacitance-voltage (C-V) measurements. The mobility enhancement of delta-doped samples over their corresponding uniformly doped samples was observed. High sheet carrier density of N
S=1.21×1013 cm-2 could be obtained. A sharp carrier distribution profile with the full width at half maximum of 25 Å has been achieved.
Photoluminescence of Homoepitaxial 3C-SiC on Sublimation-Grown 3C-SiC Substrates
Authors: Katsushi Nishino Katsushi Nishino , Tsunenobu Kimoto Tsunenobu Kimoto , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

Bulk 3C-SiC growth by a sublimation method was carried out. The grown layer was used as a substrate for chemical vapor deposition, that is, homoepitaxial growth of 3C-SiC was carried out for the first time. The substrate exhibited some impurity-related photoluminescence peaks and no exciton-related peak was observed. The epilayer had some sharp exciton-related peaks near the band edge, which showed high crystallinity of the epilayer. Au Schottky barrier diodes were fabricated on the epilayer, and the diode showed good characteristics. The quality of 3C-SiC was improved by homoepitaxial growth.
Dissociation of H2 Molecule by Picosecond Laser Irradiation at 532 nm in the 1-4×1013W·cm-2 Range
Authors: Shigeyuki Sekine Shigeyuki Sekine
Published: October 2002

Dissociation probability of H2 molecule by laser irradiation was measured in the 1-4×1013 W· cm-2 range using second harmonic of a picosecond Nd:YAG laser. The dissociation probability [H+/(H++H+
2)] increased with the light intensity and reached ∼80% at 2×1013 W· cm-2. The present result can be used as a correction factor in the measurement of gas pressure in ultrahigh vacuum by the atom counting method using the laser ionization technique.
A Novel Technique for Measuring Group Velocity Dispersion of an Installed Ultralong Fiber by Using Erbium-Doped Fiber Amplifiers
Authors: Nakazawa Masataka , Sahara Akio , Imai Takeshi , Yamamoto Takashi , Yamada Eiichi , Yasuo Kimura Yasuo Kimura
Published: October 2002

A new technique is presented for measuring the group velocity dispersion (GVD) of optical fibers. It makes it possible to measure the GVD of an already installed ultralong dispersion-shifted fiber. The method is based on phase rotation measurement, but it includes erbium amplifiers and an optical circulator or a 100% reflector. This allows round-trip propagation of the modulated signal and the GVD was successfully measured at one terminal. The maximum measurable length is as long as 125 km.
Cesium Atomic Fountain with Two-Dimensional Moving Molasses
Authors: Ohshima Shin-ichi , Kurosu Takayuki , Ikegami Takeshi , Yasuhiro Nakadan Yasuhiro Nakadan
Published: October 2002

In this paper we describe a cesium atomic fountain with two-dimensional moving molasses. This method is applicable for multipulse operation of the cesium atomic fountain frequency standard, which will improve the frequency stability and reduce the frequency shift due to spin exchange collisions of atomic fountain frequency standards. Multipulse launching is demonstrated experimentally, and the frequency shift due to the fluorescent light from the loaded atoms is estimated.
Determination of the Conduction Band Electron Effective Mass in Hexagonal GaN
Authors: M. Drechsler M. Drechsler , D. M. Hofmann D. M. Hofmann , B. K. Meyer B. K. Meyer , T. Detchprohm T. Detchprohm , H. Amano H. Amano , I. Akasaki I. Akasaki
Published: October 2002

The electron effective mass in hexagonal GaN films grown by metal organic vapor phase epitaxy on sapphire substrates is determined by cyclotron resonance experiments. Its value is m
p
* = 0.22±0.005 m
o. Taking polaron effects into account the band edge mass is m
b
* = 0.20±0.005 m
o. From the resonance linewidth a mobility of 3500 cm2/V·s at 6 K is obtained.
Fabrication of GaN Hexagonal Pyramids on Dot-Patterned GaN/Sapphire Substrates via Selective Metalorganic Vapor Phase Epitaxy
Authors: Kitamura Shota , Hiramatsu Kazumasa , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

Three-dimensional facet structure of GaN has been fabricated on dot-patterned GaN (0001)/sapphire substrates using SiO2 masks via selective epitaxial growth by metalorganic vapor phase epitaxy. The dot patterns are hexagons with width of 5 µ m and spacing of 10 µ m. The facet structure comprises a hexagonal pyramid covered with six {11̄01} facets. A stable and self-limited (0001) facet appears on the top, depending on growth conditions. The area of the (0001) facet increases with increasing growth temperature or with decreasing flow rate of trimethylgallium. The (0001) facet formation is determined by the diffusion length of a Ga atom on the (0001) surface.
Combined Effects of High-Energy Si, Zn and Ga Ion Implantation and Annealing on the Reduction of Threading Dislocations in GaAs on Si
Authors: Tamura Masao , Tohru Saitoh Tohru Saitoh
Published: October 2002

Implantation of 2 MeV Si, and 3 MeV Zn and Ga ions and annealing have been adapted in order to eliminate threading dislocations in 3-µ m-thick GaAs on Si. Si ion implantation is most effective for reducing threading dislocations over an annealing temperature range from 600 to 1000° C in the near-surface region where excess vacancies are created by implantation, suggesting that dislocations disappear by absorbing vacancies. However, no appreciable reduction of dislocations is observed in the case of Zn and Ga implantation, especially for annealing temperatures higher than 800° C, although at temperatures lower than 700° C, the dislocations in the surface region are clearly reduced, compared with those in a no-implantation sample. Such different effects on dislocation behavior are attributed to a different movement of these impurities toward the surface during annealing. Also, in Si implantation, the bending of dislocations parallel to the interface between a film and substrate is observed due to increased lattice friction in a highly Si-doped region.
Measurement of High-Frequency Dielectric Characteristics in the mm-Wave Band for Dielectric Thin Films on Semiconductor Substrates
Authors: Ikuta Kenji , Umeda Yohtaro , Yasunobu Ishii Yasunobu Ishii
Published: October 2002

Using dielectric thin film capacitors and devices specially designed for correcting stray effect around the capacitors, the dielectric constant and dielectric loss up to 50 GHz can be successfully measured by the reflection coefficient measured with a network analyzer. The high-frequency characteristics are consistent with low-frequency characteristics measured with an LCR bridge. The relative error between the high-frequency and the low-frequency is estimated to be within 10%. The method is a practical way to obtain the characteristics of dielectric thin films accurately and quickly in final form.
Deposition of Diamondlike Carbon Films Using Electron Cyclotron Resonance Plasma Chemical Vapor Deposition from Ethylene Gas
Authors: Suzuki Jun-ichi , Okada Shigenobu
Published: October 2002

Diamondlike carbon films have been prepared by RF bias electron cyclotron resonance (ECR) microwave plasma deposition from ethylene gas. The relationship between the properties of diamondlike carbon films and process parameters has been investigated. These films were evaluated in terms of Knoop hardness, Raman spectroscopy and hydrogen content measured by an elastic recoil detection analysis (ERDA) method. As the microwave power becomes higher, the hardness of the films tends to increase. This trend is different from that observed in the deposition of methane gas.
Fabrication of Pd Nanostructures with Scanning Tunneling Microscope
Authors: Hideaki Fukuzawa Hideaki Fukuzawa , Hideki Kimijima Hideki Kimijima , Nobuyuki Yoshikawa Nobuyuki Yoshikawa , Masanori Sugahara Masanori Sugahara
Published: October 2002

Nanometer-scale mounds were fabricated on Pd thin films with a scanning tunneling microscope (STM) by applying a voltage pulse to a Pd tip. Regardless of the pulse polarity, Pd mounds were formed on the sample surface when the pulse amplitude was larger than 6 V. The value of the threshold voltage was larger than that of Au observed previously, whereas the threshold voltage of Pd is predicted, on the basis of a field evaporation model, to be smaller than that of Au.
Characterization of Deep Levels in N-Type Si Epitaxial Layer
Authors: Takano Yukio , Fuma Naoki , Nakamura Noriko , Koichiro Tashiro Koichiro Tashiro
Published: October 2002

A deep level of E
c-0.46 eV (E1) was observed in commercially available Si epitaxial layers. The deep level decreased gradually at room temperature and eventually vanished completely 8 months after growth, and new levels, E
c-0.08 eV, E
c-0.10 eV, E
c-0.14 eV and E
c-0.21 eV, were observed. After annealing at 750° C, E1 level appeared again and all of the new levels disappeared. All levels, including E1, disappeared upon high-temperature annealing (>1000° C) in a O2 ambient. It was confirmed that these deep levels were due to contamination by Fe in epitaxial layer.
Temperature Dependence of Dielectric Absorption Current of SrTiO3 Thin-Film Capacitor
Authors: Fukuda Yukio , Aoki Katsuhiro , Numata Ken , Akitoshi Nishimura Akitoshi Nishimura
Published: October 2002

Temperature dependence of dielectric absorption current of the Pt/SrTiO3/Au capacitor was investigated. The time dependence of the dielectric absorption currents obtained from I-t measurements for the time window between 1 and 50 s can be fitted by a superposition of three Debye-type relaxations. Relaxation time constant and capacitance which characterize each relaxation species show different temperature dependences. Relaxation time constants are independent of temperature. On the other hand, relaxation capacitances obey Arrhenius' equation with the same activation energy of 0.18 eV.
This low activation energy suggests that the observed dielectric absorption current is electronic. Possible mechanisms for the observed dielectric relaxation are discussed based on these results.
Ultra High Repetition Rate Optical Pulse Generation by Continuous Light Injection into a Continuous Wave Operated Distributed Feedback Laser
Authors: Schöll H. , H. Burkhard H. Burkhard
Published: October 2002

We present a new method to generate short optical pulses with repetition rates from 20 to beyond 100 GHz based on the injection technique. No electrical modulation current is required. The light injection from one continuous wave (CW) operated multi quantum well (MQW)-DFB-laser into another generates stable sinusoidal laser pulses. Transmission of the pulses over a dispersion shifted fibre (DSF) generates solitons with the desired pulse width and a time bandwidth product of 0.315.
Preparation of p-Type CdS Thin Film by Laser Ablation
Authors: Keitoku Susumu , Ezumi Hiromichi , Osono Hiroto , Ohta Mitsuo
Published: October 2002

A new method to prepare p-type CdS thin film was investigated, in which the laser ablation was applied to a mixed target of CdS and Cu. The p-type CdS film was obtained from a target containing more than 5 at% Cu. Composition analysis showed that Cu content in the film was about one-fifth of that in target. The formation of p-type CdS film was also confirmed by the photovoltaic effect of the p-n junction which was constructed by laminating n-type CdS film and p-type CdS film.
Measurement of the Neutral Particle Density in an Electron Cyclotron Resonance Plasma by Rayleigh Scattering
Authors: Cronrath Wolfgang , Tanaka Hiroyuki , Bowden Mark D. , Uchino Kiichiro , Katsunori Muraoka Katsunori Muraoka
Published: October 2002

The neutral atom density in an electron cyclotron resonance plasma has been directly measured for the first time using a combination of Rayleigh and Thomson scattering. The measurements were made in the source region of a 3 mTorr argon discharge, and indicated that the neutral atom density was at least 50% less than would be expected at a gas pressure of 3 mTorr. The decrease in the neutral atom density is attributed to the effect of ion-neutral charge exchange collisions in the plasma. The accuracy of the measurement was found to depend on the contribution of metastable atoms to the measured scattered signal.
Photoluminescence Quenching in Polysilanes by Fullerene Doping and Effective Photoinduced Charge Transfer Depending on Aromatic Side Group
Authors: Yoshino Katsumi , Yoshimoto Kenji , Hamaguchi Maki , Kawai Tsuyoshi , Zakhidov Anvar A. , Ueno Hideki , Kakimoto Masaya , Kojima Hiroyuki
Published: October 2002

Photoluminescence of polysilanes with aromatic side groups has been found to be strongly quenched upon C60 doping, in contrast to the case of polysilanes with saturated hydrocarbon side groups in which a clear quenching effect has not been observed. These results have been interpreted by considering the role of the aromatic side group as a mediator for photoinduced electron transfer from electronic states of the main chain polysilanes to the C60 molecule.
In Situ Fabrication of Buried GaAs/AlGaAs Quantum-Well Mesa-Stripe Structures with Improved Regrown Interfaces
Authors: Ishikawa Tomonori , Matsuyama Isamu , Tanaka Nobuyuki , López Máximo , Tamura Masao , Nanbu Yoshihiro
Published: October 2002

The mesa-stripe structures of GaAs/AlGaAs multi-quantum-wells (MQWs) were buried by AlGaAs overgrown layers using an in situ fabrication technique, including Cl2 gas etching and molecular-beam epitaxial regrowth without air exposure. In these structures, having stripe widths of less than several microns, the photoluminescence intensities from the MQWs were considerably improved, compared to conventionally fabricated buried structures as well as to as-etched open-sidewall structures. Correspondingly, it was observed by transmission-electron-microscope that the densities of the crystal defects at the in situ regrown interfaces were greatly reduced, indicating great usefulness of in situ techniques in fabricating high-quality microstructures.
New Optical Memory Structure Using Self-Assembled InAs Quantum Dots
Authors: Imamura Kenichi , Sugiyama Yoshihiro , Nakata Yoshiaki , Muto Shunichi , Naoki Yokoyama Naoki Yokoyama
Published: October 2002

We propose a new optical memory structure using self-assembled InAs quantum dots (QDs) for possible applications to wavelength-domain-multiplication memory, which should lead to increase memory density. Data stored in this memory structure can be read using photocurrent and then erased electrically. In a preliminary study, we confirmed the memory effect of photocurrent caused by the InAs QDs for the first time. A retention time of 0.48 ms for the memory was obtained at 300 K.
Observation of 7×7 Reconstructed Structure on the Silicon (111) Surface using Ultrahigh Vacuum Noncontact Atomic Force Microscopy
Authors: Kitamura Shin-ichi , Masashi Iwatsuki Masashi Iwatsuki
Published: October 2002

Unlike ultrahigh vacuum (UHV) scanning tunneling microscopy (STM), the effectiveness of UHV in UHV atomic force microscopy (AFM) has not been verified. Intensive interaction between tip and sample in UHV often damages the sample surface in the contact mode. Although noncontact (NC) AFM is effective in protecting the sample surface, it has failed to provide atomic-level resolution. We used a stiff silicon cantilever ( ∼40 N/m) capable of STM imaging, and succeeded in obtaining the first atomic-resolution images of Si(111)7×7 reconstruction in NC AFM at a tip-sample distance almost equal to that for STM imaging.
Transmittance Bistability of CdS at 632.8 nm Induced by the 514.5 nm Line
Authors: Ullrich Bruno , Ezumi Hiromichi , Misawa Kazuhiko , Keitoku Susumu , Kobayashi Takayoshi
Published: October 2002

For the first time, we demonstrate that irradiation of CdS with a 514.5 nm argon line causes the formation of an all-optical bistable loop in the transmitted power of the 632.8 nm He-Ne line at 300 K.
The effect is due to a nonlinearity in the transmittance created by the known trap level of pure CdS situated 0.52 eV below the conduction band.
Large Electro-Optical Modulation of a Field-Effect Transistor-Type Waveguide Modulator Using α-Sexithienyl
Authors: Tetsuyuki Kurata Tetsuyuki Kurata , Chie Fukada Chie Fukada , Hiroyuki Fuchigami Hiroyuki Fuchigami , Kouji Hamano Kouji Hamano , Sei Tsunoda Sei Tsunoda
Published: October 2002

An optical waveguide modulator having a field-effect transistor-type electrode using a thiophene oligomer, α-sexithienyl, has been fabricated and has functioned as an electro-absorption modulator with the modulation ratio of 20%. The device also functions as a field-effect transistor (FET). The optical modulation is directly related with the FET device operation, and has shown a maximum at 830 nm for propagating light wavelength. Therefore, the mechanism of the optical modulation has been clarified to be the increasing absorption due to polarons induced or injected by negative bias.
Role of Vacancy-Type Defects during Structural Relaxation of Amorphous Si
Authors: Motooka Teruaki , Hiroyama Yuichi , Suzuki Ryouichi , Ohdaira Toshiuki , Hirano Yosiuki , Sato Fumio
Published: October 2002

Structural relaxation processes in amorphous Si (a-Si) have been investigated using Raman spectroscopy and positron lifetime measurements. Bond angle deviation Δθ and sizes of vacancy-type defects were estimated for ion-beam-induced a-Si (IBa-Si) and ECR plasma CVD a-Si (ECRa-Si). During 450° C annealing, Δθ decreased appreciably and only small vacancies with a size less than that of the divacancy were observed in IBa-Si, while in ECRa-Si large vacancy clusters were formed and Δθ was approximately constant indicating that relaxation processes are suppressed in ECRa-Si. These results suggest that large vacancy-type defects can stabilize amorphous structures.
On the Frequency Dependence of Si2F6 Isotope-Selective Multiphoton Dissociation
Authors: Okamura Hideki , Tosa Valer , Kazuo Takeuchi Kazuo Takeuchi
Published: October 2002

The laser frequency dependence of the enrichment factors in the separation of silicon isotopes by infrared multiphoton dissociation (MPD) were calculated. Based on the knowledge of the isotopic shifts, a simple model was developed to estimate the dependence of the MPD yield on the laser frequency. The results agree well with the experimental results reported elsewhere. This new method allows us to determine the relative contribution to the MPD yield of the 6 Si2F6 isotopic species and to explain the behavior of the enrichment factors.
Effect of SC1 Process on Silicon Surface Microroughness and Oxide Breakdown Characteristics
Authors: Akiyama Kazuhiro , Naito Nobumasa , Nagamori Motoaki , Koya Hiroshi , Morita Etsuro , Sassa Kouichi , Suga Hisaaki
Published: October 2002

Surface microroughness and its effects on dielectric breakdown characteristics have been investigated for silicon wafers treated in SC1-based solutions. Surface microroughness was quantified using atomic force microscopy (AFM) and phase shift interferometry (PSI). In contrast to previous reports that SC1 treatment caused undulation of the surface, our observation showed a nominal amount of deterioration. Even prolonged dipping in a solution with high etching rate did not roughen the surface, and the dielectric breakdown characteristics were not affected.
Observation of Boundary Josephson Junction with d-Wave Pairing Characteristics
Authors: Ishimaru Yoshihiro , Wen Jianguo , Hayashi Kunihiko , Youichi Enomoto Youichi Enomoto , Naoki Koshizuka Naoki Koshizuka
Published: October 2002

Josephson junctions have been fabricated along boundaries between (001) of a-axis oriented YBCO grains and (110) of c-axis oriented YBCO grains. These grain boundaries are formed along an a-axis oriented grain surrounding by the YBCO c-axis oriented film deposited on a MgO (001) substrate. TEM observation shows clear lattice image of the grain boundary. A typical RSJ type I-V curve with J
c of 1.4×104 A/cm2 at 4.2 K, and Shapiro steps under microwave irradiation are observed, indicating that the boundary works as a Josephson junction. The diffraction pattern of I
c under magnetic field has the minimum value at zero magnetic field. This property is analogous to one expected for a s-wave- d-wave junction.
New Compound Sr3Ca3Cu6O12±δ with Modulated Superstructure
Authors: Ramirez-Castellanos Julio , Matsui Yoshio , Kawashima Tetsuya , Takayama-Muromachi Eiji , Kirkland Angus I.
Published: October 2002

A new ordered phase with a composition close to Sr3Ca3Cu6O12±δ has been found in a specimen, prepared by a high-pressure technique, which showed superconductivity. It was found from selected-area diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) studies that this phase has a wavy modulated superstructure, with lattice parameters a\conga
c, b≈6a
c and c≈6a
c, where a
c is the cubic perovskite parameter. A tentative structural model based on the two-dimensional ordering of Sr and Ca atoms in the SrCuO2 infinite-layer (IL) basic structure is proposed.
Observation of Saturation Spectrum of the 2ν3 Band of Methane
Authors: Kotaro Suzumura Kotaro Suzumura , Hiroyuki Sasada Hiroyuki Sasada
Published: October 2002

We have carried out intracavity saturated absorption spectroscopy of the 2ν3 band of methane using a 1.6-µm-grating feedback external-cavity semiconductor laser. Since the narrowest linewidth of observed saturation dips is only 0.9 MHz (half-width at half-maximum), a high potential exists for the use of this band as a precise frequency standard, especially when considering that the ν3 band of methane is currently a well-established frequency standard.
Reconstruction Dependent Indium Segregation
Authors: Ekenstedt Michael Jan , Yamaguchi Hiroshi , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

Fully strained In0.5Ga0.5As layers are grown on InAs substrates in order to measure the degree of In segregation, and its dependence on surface reconstruction and substrate temperature by reflection high energy electron diffraction. We find that segregation is reduced for an As-covered 2×4 reconstructed surface as compared to a group III stabilized surface. Results show that the segregation process occurs primarily between the surface and the first subsurface layer. We present evidence showing that the effect a 1 Ml In0.5Ga0.5As layer deposited on InAs has on the As-desorption is countered for by capping the layer with 6 to 10 monolayers of InAs.
Evaluation of Evaporated Species from Silicon Melt Surface during Sb-Doped Czochralski Silicon Crystal Growth
Authors: Huang Koji Izunome , Kazutaka Terashima Kazutaka Terashima , Shigeyuki Kimura Shigeyuki Kimura
Published: October 2002

The composition of oxygen-bearing species evaporated from the Sb-doped silicon melts in a mass-production Czochralski (CZ) crystal growth system was studied. Deposits in the growth chamber and in the exhaust vent were analyzed by X-ray diffraction (XRD) measurement. The results showed that the composition of the deposits depended on the collection region, but was independent of the ambient pressure. The analysis showed that deposits in the exhaust vent contained crystalline phases of Sb2O3 and metallic Sb, and those in the inner chamber wall consisted of the crystalline phase of only metallic Sb, while an amorphous phase of SiO was only detected in the exhaust vent. It can therefore be concluded that Sb oxide species evaporate from the melt to Ar ambient in a Sb-doped CZ silicon crystal growth system. The site difference of nucleation and growth of evaporated species may have affected the deposition composition in CZ crystal growth system.
Fabrication and Superconducting Properties of Bi2Sr2CaCu2Oy Multilayer Tape Prepared by Continuous Heat Treatment
Authors: Hasegawa Takayo , Hikichi Yasuo , Kumakura Hiroaki , Kitaguchi Hitoshi , Togano Kazumasa
Published: October 2002

Flexible Bi-2212 multilayer tapes of ∼80 m length were prepared by a combination of the oxide-painting method and the continuous heat-treatment technique. The tapes were heat-treated by passing them through a tube furnace having temperature gradient which induced partial melting and slow cooling. The tapes had critical current density (J
c) values higher than 1× 105 A/cm2 at 4.2 K and 12 T. The tapes showed excellent J
c vs strain properties. J
c was almost constant up to the bending strain of 0.7% (the bending diameter of 30 mm). Hence the “react & wind” technique could be applied to the fabrication of coils. A small pancake coil fabricated by the “react & wind” technique had J
c values almost equal to those of short straight tapes.
Synthesis and Characterization of Mutually Incommensurate (BiS)1.16VS2 with Layered Composite Crystal Structure
Authors: Gotoh Yoshito , Akimoto Junji , Onoda Yoshinao Oosawa
Published: October 2002

Single crystal of a new type of mutually incommensurate composite crystal with layered structure, (BiS)1.16VS2 has been synthesized by chemical vapor transport method. The X-ray precession photographs of (BiS)1.16VS2 have revealed the composite diffraction patterns of C-centered monoclinic VS2 subsystem with a=5.670(2) Å, b
1=3.261(2) Å, c=11.354(3) Å, β=94.97(3) Åand C-centered monoclinic BiS subsystem with a=5.670(2) Å, b
2=5.643(3) Å, c=11.354(3) Å, β=94.97(3)°. The lattice parameters obtained have led to the 2D-commensurate structure of (BiS)1.16VS2 along the mutually incommensurate axis. The morphology of single crystal (BiS)1.16VS2 has been found to be closely related to the orientation of the row of the superstructure reflections observed.
Digital Speckle Pattern Interferometry for Observing the Entire Process of Plastic Deformation of a Solid Object
Authors: Satoru Toyooka Satoru Toyooka , Xinglong Gong Xinglong Gong
Published: October 2002

A new scheme of digital speckle pattern interferometry (DSPI) for observing the entire process of dynamic deformation from the beginning of elastic deformation to the end of plastic deformation at fracture is proposed. Interesting deformation processes which consist of spatial mode division of fringes caused by plastic deformation and stress relaxation were clarified by simple experiments.
Oriented Nucleation of Diamond Particles on (001) β-SiC Surface at Low Pressure
Authors: Nadine Marechal Nadine Marechal , Satoshi Yamashita Satoshi Yamashita
Published: October 2002

Heteroepitaxial nucleation of diamond particles has been achieved on (001) β-SiC surfaces at pressures as low as 0.3 Torr using the bias-enhanced nucleation (BEN) method in an electron cyclotron resonance (ECR) microwave chemical vapor deposition (CVD) system. Oriented nucleation was possible over a length of 40 mm and under various pressures from 0.3 Torr to 2 Torr while increasing the negative bias voltage with the pressure. Moreover, it has been observed that, after pretreatment favorable for oriented nucleation, the substrate exhibited a noticeable stripe surface morphology.