bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen Distribution and Chemical Bonding State Analyses in Oxynitride Film by Spatially Resolved Electron Energy Loss Spectroscopy (EELS)
Authors: Sekiguchi Tomoko , Kimoto Koji , Aoyama Takashi , Mitsui Yasuhiro
Published: October 2002

Nitrogen distribution and chemical bonding states in a multilayer
(SiO2/Si3N4/SiO
x
N
y
(oxynitride)/Si) are analyzed using spatially resolved
electron energy loss spectroscopy (EELS). Multiple spectra of different
points in a selected area are obtained simultaneously, and core-loss
intensity and chemical bonding states are analyzed at each point.
Nitrogen is accumulated both at the oxynitride and silicon interface and
in the vicinity of oxide surface, and the nitrogen peak full widths at half-maximum (FWHM) are about 2 nm and 3.2 nm, respectively. The
nitrogen-accumulated interface layer consists of two regions: the upper
region of the interface may have N–O bonds and the lower region consists
of mainly nitrides. The EELS has spatial and energy resolutions of
about 1 nm and 0.1 eV, respectively.
Ellipsometric Thickness Measurements of Ultrathin Silicon Oxides Formed in Aqueous Solution
Authors: Suni Ian Ivar
Published: October 2002

Spectroscopic ellipsometry was employed to measure the thickness of ultrathin silicon oxide
films prepared in several different aqueous processing solutions used during microelectronics
manufacture. Ellipsometric measurements were fit to several different models for the Si/SiO2
interface, with the best fit obtained for a model which assumes the silicon oxide film to be a mixture
of SiO2 and amorphous Si. The dielectric function of this mixture was obtained from the Bruggeman
effective medium approximation. The silicon oxide film thicknesses following treatment in HF
etchant and SC-1 and SC-2 solutions were 8.6(2) Å, 8.9(4) Å, and 8.6(9) Å, respectively.
Spiral Growth of YBa2Cu3O7- y Thin Films by Metalorganic Chemical Vapor Deposition Using Liquid-State Sources
Authors: Iwata Morihiro , Yoshida Yutaka , Hasegawa Masato , Ito Yoshiaki , Hirabayashi Izumi , Takai Yoshiaki
Published: October 2002

Superconducting YBa2Cu3O7-y
(YBCO) thin films were prepared on MgO (100) and LaAlO3 (100) substrates by metalorganic chemical vapor deposition (MOCVD) with liquid-state sources. We investigated the surface morphologies of the samples by atomic force microscopy (AFM). Numerous spiral steps accompanied by screw dislocations were observed in the AFM image. These spiral steps are about 12 Å in height, which agrees well with the one-unit cell length along the c-axis of YBCO. Terrace widths of the spiral growth increased significantly as the substrate temperature rose. Furthermore, the supersaturation ratio calculated from the terrace widths changed considerably at the substrate temperature of 750–800°C. This suggested the occurrence of environmental changes at this temperature region and a quasi-liquid layer was present on the growing surface of the films.
High-Temperature Synthesis of Amorphous Carbon Nitride Thin Films with Modified Microstructure
Authors: Yap Yoke Khin , Kida Shinjiro , Aoyama Toshihiro , Mori Yusuke , Sasaki Takatomo
Published: October 2002

Carbon nitride (CN) thin films were synthesized by RF plasma-pulsed laser deposition (PLD) technique at 600°C. Nitrogen incorporation of CN films was observed to increase significantly with the increase of negative d.c. self bias voltage. Fourier transform infrared (FTIR) spectra of these films were found to resolve into two distinguishable absorption bands centered at 1550 cm-1 and 1200 cm-1 in contrast to a single broad absorption band usually reported. With a coupled interpretation of X-ray photoelectron spectroscopy (XPS), FTIR and Raman spectroscopies, these films appeared to consist of tetrahedral N-s
p
3 C and trigonal N-s
p
2 C binding states with suppressed graphite-like CN microstructure.
Cross-Sectional Transmission Electron Microscope Observation of Isolated Diamond Particles Heteroepitaxially Grown on Pt(111) Substrate
Authors: Zhou Guofu , Takai Yoshizo , Shimizu Ryuichi
Published: October 2002

Isolated diamond particles grown on a Pt(111) substrate are studied by cross-sectional transmission electron microscopy (TEM). We found that almost all the heteroepitaxial diamond particles contain a Pt nucleus at the bottom center of each particle. The study suggests that a rough Pt substrate surface plays an important role for diamond growth. Our results revealed that some diamond particles directly nucleate from the Pt substrate, leading to the heteroepitaxial growth of diamond on the Pt(111) substrate. The difference in the interface structure between epitaxial and nonepitaxial diamond particles is also studied.
Parallel Simulation of Ion Implantation for Multi-Component Targets Using Boltzmann Transport Equation
Authors: Wang Shyh-Wei , Guo Shuang-Fa
Published: October 2002

A stepwise Boltzmann transport equation (BTE) simulation using non-uniform energy
grid momentum matrix and exact nuclear scattering cross-section is successfully
parallelized to simulate the ion implantation of multi-component targets. Assuming that
the interactions of ion with different target atoms are independent, the scattering of ions
with different components can be calculated concurrently by different processors. It is
developed on CONVEX SPP-1000 and the software environment of parallel virtual
machine (PVM) with a master-slave paradigm. A speedup of 3.3 has been obtained for
the simulation of As ions implanted into AZ1350 (C6.2H6O1N0.15S0.06) which is composed
of five components. In addition, our new scheme gives better agreement with the
experimental results for heavy ion implantation than the conventional method using a
uniform energy grid and approximated scattering function.
Time-Reversible Property of 1/f Fluctuation Using Higher-Order Correlation Function
Authors: Akabane Hideo , Agu Masahiro
Published: October 2002

1/f fluctuation is usually generated in a complex system composed of many
dissipative or nondissipative partial systems. Based on a postulate that the 1/f
fluctuation is related to higher-order non-Gaussian processes, we investigate the
time-reversible property of the computer-generated 1/f fluctuation using a higher-order correlation function. It is shown that several types of 1/f fluctuations exist
although they have the same 1/f spectrum.
Protection of Field Oxide in Trench Isolation against Contact Hole Etching to Improve Alignment Tolerance
Authors: Oishi Toshiyuki , Shiozawa Katsuomi , Sugihara Kouhei , Abe Yuji , Tokuda Yasunori
Published: October 2002

We demonstrate that field oxide in trench isolation is successfully protected
against contact hole etching by inserting a thin etch-stopping Si3N4 film into the
SiO2 interlayer. Results suggest that alignment tolerance of the contact hole can
be drastically improved. The breakdown voltage (V
b) of trench isolation was
maintained at 15 V, even with overlap of the contact hole and trench isolation as
long as 0.26 µm, though the V
b value for a conventional structure was
considerably degraded by overlapping.
InGaN-Based Blue Light-Emitting Diodes Grown on Epitaxially Laterally Overgrown GaN Substrates
Authors: Mukai Takashi , Takekawa Kazunori , Nakamura Shuji
Published: October 2002

InGaN single-quantum-well-structure blue light-emitting diodes (LEDs) were
grown on epitaxially laterally overgrown GaN (ELOG) and sapphire substrates. The
emission spectra showed the similar blue shift with increasing forward currents for
both LEDs. The output power of both LEDs was almost the same, as high as 6 mW at a
current of 20 mA. The LED on sapphire had a considerable amount of leakage current
in comparison with that on ELOG. These results indicate that the In composition
fluctuation is not caused by dislocations, the dislocations do not act as nonradiative
recombination centers in the InGaN, and the dislocations forms the leakage current
pathway in InGaN.
Suppression of Geometric Component of Charge Pumping Current in Thin Film Silicon on Insulator Metal-Oxide-Semiconductor Field-Effect Transistors
Authors: Duyet Tran Ngoc , Ishikuro Hiroki , Takamiya Makoto , Saraya Takuya , Hiramoto Toshiro
Published: October 2002

A new reverse pulse method is proposed for precise measurement of
charge pumping current in silicon on insulator
metal-oxide-semiconductor
field-effect transistors (SOI MOSFETs),
where the reverse pulse voltage is applied
to the body only at the gate voltage rise time.
The majority carries of the high resistive body region can be
completely removed by applying the reverse pulse to the body.
Therefore, the undesirable, geometry-dependent component which causes imprecise
measurement of the interface trap density on SOI MOSFETs is suppressed.
This method also suppresses the reduction of effective channel length
which takes place when using a DC reverse bias.
It is demonstrated that
the accurate measurements
of the interface density on SOI MOSFETs are possible.
Optical Frequency Mixing due to Magnetoplasma in Semiconductors
Authors: Mizushima Yoshihiko
Published: October 2002

Magnetooptical dispersion in semiconductors in a Voigt
configuration has been studied in this paper. A space-charge
interaction occurs between two light waves due to the longitudinal
field component, implying the possibility of a new mode of optical
mixing in the infrared wavelength region. This effect can find
applications in wavelength converters, optical switches and logic
gates, where no power consumption is required.
High Efficiency-Carrier-Generation for the Oxygen Release Reaction in Indium Tin Oxide
Authors: Omata Takahisa , Fujiwara Hiroyuki , Otsuka-Yao-Matsuo Shinya , Ono Naoki , Ikawa Hiroyuki
Published: October 2002

Indium tin oxide (ITO) sinters were heated up to 1073 and 1273 K under the
condition that P(O2)/P
* = 4.9 ×10-4 (P
*: atmospheric pressure), when P(O2) was
approximately 50 Pa, in a closed-system oxygen-gas analyzer, and the number of
oxygen atoms released from ITO was quantitatively determined. The conduction
electron densities were determined by Hall measurements at room temperature. It
was shown that the release of one oxygen atom corresponded to the generation of
two conduction electrons, i.e., the efficiency-carrier-generation for the oxygen
release from the ITO was almost one. Based on the crystal structure of the
ITO, the oxygen atom released was originally at the 16c site in the space group of Ia3
as an interstitial excess oxygen, O
i

′′.
Model of Ion Solvation in Liquid Crystal Cells
Authors: Bremer Matthias , Naemura Shohei , Tarumi Kazuaki
Published: October 2002

The leading display technology, active matrix display requires very high reliability. Characteristic parameters for high reliability are, for instance, voltage holding ratio and residual DC values. Both parameters show a strong deterioration if some charge carrier or contamination is present in active matrix display cells, and this leads to an inacceptable contrast value of the display. The physicochemical understanding of such contamination causes, origin or solvation, still remain unclear. A model is presented in this paper, using a simple simulation method called `sparkle' whose results are in very good agreement with the experimental results.
Specific Effects of Oxygen Molecule and Plasma on Thin-Film Growth of Y-Ba-Cu-O and Bi-Sr-(Ca)-Cu-O Systems
Authors: Tamio Endo Tamio Endo , Munehiro Horie Munehiro Horie , Naoki Hirate Naoki Hirate , Katsutoshi Itoh Katsutoshi Itoh , Satoshi Yamada Satoshi Yamada , Masaki Tada Masaki Tada , Ken-ichi Itoh Ken-ichi Itoh , Morihiro Sugiyama Morihiro Sugiyama , Shinji Sano Shinji Sano , Kinji Watabe Kinji Watabe
Published: October 2002

Thin films of a-oriented YBa2Cu3Ox (YBCO),
Ca-doped c-oriented Bi2(Sr,Ca)2CuOx and nondoped
c-oriented Bi2Sr2CuOx (Bi2201) were prepared at
low temperatures by ion beam sputtering with supply of oxygen molecules or plasma.
The plasma enhances crystal growth of the a-YBCO and Ca-doped Bi2201 phases.
This can be interpreted in terms of their higher surface energies.
The growth and quality of nondoped Bi2201 are improved with the
supply of oxygen molecules.
This particular result could be interpreted by the collision process
between the oxygen molecules and the sputtered particles.
Plasma Chemical Vaporization Machining (CVM) for Fabrication of Optics
Authors: Takino Hideo , Shibata Norio , Itoh Hiroshi , Kobayashi Teruki , Tanaka Hiroaki , Ebi Masami , Yamamura Kazuya , Sano Yasuhisa , Mori Yuzo
Published: October 2002

We have developed a device for the fabrication of optical surfaces on the
basis of plasma chemical vaporization machining (CVM). In this device,
radio-frequency plasma generated at the tip of a pipelike electrode under about
one atmosphere moves over a workpiece surface in a computer-controlled
environment to remove a target area. A workpiece of silica glass was shaped to
investigate the removal characteristics of the new device. The findings show that
the new device allows high-precision fabrication from the nm to the µm level.
The shaped surface is sufficiently smooth for optical use.
Determination of Flow Pattern Defect Area by µ-Photoconductivity Decay Lifetime Measurement
Authors: Lee Bo-Young , Hwang Don-Ha , Kwon Oh-Jong
Published: October 2002

Flow pattern defects (FPDs), the decrease in interstitial oxygen concentration during heat treatment and µ-photoconductivity decay (µ-PCD) lifetime were measured precisely in the radial direction using samples with different grown-in defect densities and defect generation areas. In the inner and/or outer region adjacent to the rim of the FPD area where FPD density was zero, a peak and/or a valley of µ-PCD lifetime distribution were observed. It was found that the µ-PCD lifetime distribution depended on the behavior of oxygen precipitation, especially on anomalous oxygen precipitation (AOP). In the case of FPD area larger than about 175 mm in diameter, the edge effect became dominant and it was difficult to observe a peak or a valley in the µ-PCD lifetime distribution due to AOP. The FPD area, however, could be monitored by theµ-PCD lifetime measurement. The relationship between µ-PCD lifetime and oxygen precipitation rate was also interpreted.
Fabrication and Characterization of AlGaN/GaN Double-Heterolaser Structures on Sapphire Substrates Using Single Crystalline AlN Buffer Layers
Authors: Ohba Yasuo , Yoshida Hiroaki
Published: October 2002

High-Al-composition AlGaN/GaN double-heterolaser structures were fabricated on sapphire substrates using single crystalline AlN buffer layers. Structures having
Al0.25Ga0.75N cladding layers with a 2-µm total thickness were grown without cracks. Device performance was mainly investigated for the structure with Al0.2Ga0.8N cladding layers and a
multiquantum-well-structure active layer. Optical emission was intense for devices with a multiquantum-well-structured active layer. However, no sign of stimulated emission was observed in this study.
NOx Removal in N2 by Pulse Intense Electron Beam Irradiation
Authors: Nakagawa Yoshiro , Kawauchi Hiroshi
Published: October 2002

As an application of pulse intense electron beam for pollution control, removal of nitrogen oxides (NO
x
) in atmospheric pressure N2 was demonstrated. The pulse electron beam (energy; ∼200 keV, current; ∼140 A, current density; ∼2.2 A/cm2 and pulse width; ∼500 ns) was injected into a gas cell filled by 1 atmospheric pressure N2 with an initial concentration of 200 ppm of NO and at a temperature of 26°C. The typical removal ratio was 17% for the first shot and reached to 93% after 8 successive shots. This removal ratio corresponds to 2740 nmol of removed NO
x
and to a 192 nmol/J removal efficiency. Many nitrogen radicals produced by the electron beam interaction with N2 play an important role in the reduction of NO. The removal ratio was increased to 33% for the first shot when the initial concentration of NO was decreased to 64 ppm. However, the amount of removed NO
x
was smaller at low initial concentrations. When the filling pressure was decreased to 260 Torr, the amount of removed NO
x
decreased almost proportional to the pressure.
Improved Extinction Ratio in Ultra Short Directional Couplers Using Asymmetric Structures
Authors: Boo-Gyoun Kim Boo-Gyoun Kim , Ali Shakouri Ali Shakouri , Bin Liu Bin Liu , John E. Bowers John E. Bowers
Published: October 2002

Various means of increasing the extinction ratio in ultra short
directional couplers using slight asymmetry in the coupled waveguide
structure are investigated. It is shown that couplers with 10–200 µm coupling length and with high extinction ratios larger than 30 dB can be achieved. Shorter asymmetric couplers have an extinction
ratio that is more fabrication tolerant.
Calculation of Optical and Dielectric Anisotropy of Nematic Liquid Crystals
Authors: Klasen Melanie , Bremer Matthias , Götz Achim , Manabe Atsutaka , Naemura Shohei , Tarumi Kazuaki
Published: October 2002

The optical birefringence (Δn) and dielectric anisotropy (Δε) of nematic liquid crystals
were calculated using the well-known theories of Vuks and Maier-Meier, respectively. The
molecular dipole moments and polarizabilities needed for the estimation were taken from
semiempirical AM1 calculations. The calculated values are in good agreement with the
experimental results for the investigated compounds having different core structures and polar
substituents.
Optical Characteristics of Ultrathin Oligosilane Films Prepared by Molecular Beam Deposition Method
Authors: Daigo Sasaki Daigo Sasaki , Hirokazu Tada Hirokazu Tada , Kenji Ishida Kenji Ishida , Toshihisa Horiuchi Toshihisa Horiuchi , Kazumi Matsushige Kazumi Matsushige , Takaki Endo Takaki Endo , Masahiro Kako Masahiro Kako , Yasuhiro Nakadaira Yasuhiro Nakadaira
Published: October 2002

In order to investigate the correlation between the molecular
orientation and the optical characteristics of ultrathin
films of permethyl-dodecasilane,
CH3{Si(CH3)2}12CH3 (DM12), we grew the films
on quartz, KBr and KCl by molecular beam deposition, and characterized
them by optical absorption, photoluminescence (PL), and photoexcitation spectroscopy and atomic force microscopy.
We found that DM12 molecules formed a monolayer on quartz
with their molecular chains perpendicular to the surface, while DM12
films grew on KBr and KCl with their molecular axis oriented parallel to the
surfaces. These films exhibited quite different absorption spectra
as a result of their molecular orientation and the interaction between
molecules. The PL spectra obtained for the films
on quartz and KBr were, however, almost the same, indicating that the
origin of the luminescence was the localized states such as defects on
the chains.
Liquid-Phase Deposition of Silicon-Dioxide Films using Tetra-Ethyl Orthosilicate
Authors: Koh-ichi Usami Koh-ichi Usami , Shin Hayashi Shin Hayashi , Yasutaka Uchida Yasutaka Uchida , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Silicon-dioxide films have been liquid-phase deposited from a halogen-free silicon source. Tetra-ethyl orthosilicate was introduced, for deposition, into water with NH3 and HCOOH. The deposition rate was as high as 150 nm/h. The deposited film was stoichiometric SiO2 with no C and N. The film properties are also discussed.
Improved LiNbO 3 Technology for Reducing Sidelobe Asymmetry in Mode Converter-Based Wavelength Filters
Authors: Franck Chollet Franck Chollet , Jean-Pierre Goedgebuer Jean-Pierre Goedgebuer
Published: October 2002

We present an experimental explanation of the sidelobe amplitude increase
generally observed in LiNbO3 polarization converter-based wavelength filters.
We propose a simple improved LiNbO3 process to avoid this problem and show experimental
results that confirm our hypothesis.
Humidity Dependence of Photoluminescence in Coumarin-4-Doped Sol-Gel Coating Film
Authors: Takahashi Yoshihiro , Suzuki Kazuyuki , Takeda Takayuki , Maeda Akinori , Kojima Kenzo , Ohta Hiroshi , Inoue Shinichi
Published: October 2002

Coumarin 4 dye was doped in a silica matrix coated as a
thin film by means of the sol-gel technique. The fluorescence
intensity of the immobilized dye was quenched by moisture.
The humidity dependence of the fluorescence intensity was
examined in the relative humidity range between about 3 and
90% as a function of the concentration of coumarin 4 and
catalytic aqueous HCl. The obtained results reveal that the
fluorescences emitted from both the coumarin 4 monomer and
the aggregates of dye molecules are quenched by moisture and
their quenching is explained by the Stern-Volmer equation.
Metalorganic Vapor Phase Epitaxial Growth of GaNAs Using Tertiarybutylarsine (TBA) and Dimethylhydrazine (DMHy)
Authors: Moto Akihiro , Tanaka So , Ikoma Nobuyuki , Tanabe Tatsuya , Takagishi Shigenori , Takahashi Mitsuo , Katsuyama Tsukuru
Published: October 2002

GaNAs alloys were successfully grown on GaAs substrates by low-pressure metalorganic vapor phase epitaxy (MOVPE) with all organometallic sources of
triethylgallium (TEG), tertiarybutylarsine (TBA), and dimethylhydrazine (DMHy). For
nitrogen, the desorption coefficient of 30 kcal/mol was derived from the nitrogen
incorporation dependence on growth temperature. Since the nitrogen concentration above
3% was easily achieved by our growth technique, the combination of TBA-DMHy as V
precursors is a candidate for the growth of other III-V alloys containing nitrogen. We
observed a decrease in PL intensity with enhancing nitrogen incorporation into solids. In
order to recover from degradation of optical properties, rapid thermal annealing (RTA)
was demonstrated and found to be effective. Therefore MOVPE using TBA-DMHy
combined with postgrowth annealing is expected to obtain GaNAs alloys with high
nitrogen concentration as well as excellent optical properties.
High-Quality InGaAsN Growth by Metalorganic Vapor-Phase Epitaxy Using Nitrogen Carrier Gas and Dimethylhydrazine, Tertiarybutylarsine as Group V Precursors
Authors: Ougazzaden Abdallah , Rao Elchuri , Sermage Bernard , Leprince Laurent , Gauneau Marcel
Published: October 2002

We have successfully grown GaAsN and InGaAsN layers on GaAs substrate using
atmospheric-pressure metalorganic vapor-phase epitaxy (MOVPE). Dimethylhydrazine and
tertiarybutylarsine have been employed as sources of nitrogen and arsenic, respectively. To
investigate the incorporation behavior of nitrogen [N] in GaAsN and InGaAsN layers as a function
of ambient gas in the reactor, growth was performed in the presence of hydrogen H2 and nitrogen N2
gases. Good structural quality and surface morphology have been obtained with both gases.
Furthermore, with N2 ambient gas, an enhancement of nitrogen incorporation has been observed.
The nonradiative carrier lifetime is about 25 ns and is independent of the ambient gas used. This
value is acceptable for laser applications.
Properties of In0.52Al0.48As and In0.53Ga0.47As/In0.52Al0.48As Quantum Well Structures Grown on (111)B InP Substrates by Molecular Beam Epitaxy
Authors: Kawamura Yuichi , Kamada Akihiko , Yoshimatsu Kiyotune , Nakao Masashi , Inoue andNaohisa
Published: October 2002

In0.52Al0.48As and In0.53Ga0.47As/In0.52Al0.48As quantum well (QW) structures were grown
on (111)B InP substrates by molecular beam epitaxy, and their optical and electrical properties
were studied. The photoluminescence (PL) spectrum and electron mobility of the InAlAs layers
grown on the (111)B InP substrates were found to have a remarkable dependence on the V/III
ratio and the growth temperature. It was found that the PL peak energy of the InGaAs/InAlAs
QWs grown under optimized conditions on the (111)B InP substrates shows a remarkable red
shift compared to that grown on the (100) InP substrates. An atomic force microscopy
observation revealed that the observed red shift for the (111)B QW is induced by a large surface
step-bunching.
InAs-Dot/GaAs Structures Site-Controlled by in situ Electron-Beam Lithography and Self-Organizing Molecular Beam Epitaxy Growth
Authors: Kohmoto Shigeru , Ishikawa Tomonori , Asakawa Kiyoshi
Published: October 2002

A novel site-control technique for InAs dot fabrication on GaAs has been
demonstrated by a combination of in situ electron-beam (EB) lithography and self-organizing molecular beam epitaxy (MBE) using an ultrahigh-vacuum multichamber
system. On an MBE-grown GaAs (001) surface, shallow holes of submicron size were
patterned by in situ EB writing and Cl2 gas etching. By supplying more than 1.4
monolayer of InAs onto the patterned surface, In(Ga)As dots were preferentially self-organized in the holes, while dot formation around the holes was sufficiently suppressed,
due to the selectivity of In atom incorporation in the (111)B-like slope in the hole. This
indicates the usefulness of such a technique in fabricating
arbitrarily arranged quantum-dot structures.
The Procedure to Realize Two-Dimensional Quantum Dot Superlattices: From Incoherently Coupled to Coherently Coupled Quantum Dot Arrays
Authors: Lan Sheng , Akahane Kouichi , Jang Kee-Youn , Kawamura Takahiro , Okada Yoshitaka , Kawabe Mitsuo
Published: October 2002

We will describe, from both the theoretical and experimental points of view, a procedure leading to the realization of two-dimensional quantum dot superlattices (2D QDSLs). Two kinds of laterally coupled quantum dot arrays in which the exciton motions are coherent and incoherent are studied by photoluminescence (PL) measurements. The formation of minibands with coherent exciton motion is demonstrated in the large red shift of the PL peak energy as well as the dramatic narrowing of the PL linewidth. Moreover, we indicate, using excitation-dependent PL spectra as an example, that the exciton coherence can be reduced by various scattering mechanisms.
Fermi Level Pinning and Schottky Barrier Height Control at Metal-Semiconductor Interfaces of InP and Related Materials
Authors: Hasegawa Hideki
Published: October 2002

The present status of the various approaches to understand and control Schottky barrier heights (SBHs) on InP and related materials is reviewed. First, a brief survey on the models of Fermi level pinning is given. Then, approaches of SBH control by (1) formation of insulator interlayers, (2) formation of semiconductor interlayers, (3) sulphur and selenium surface treatments, (4) low-temperature metal deposition, (5) plasma surface treatments, and (6) electrochemical deposition are discussed from the viewpoints of the mechanism of SBH increase, the SBH values achieved, the controllability and reproducibility of the process, and the barrier reliability. A particular emphasis is placed on the in-situ electrochemical process recently developed by the author's group where Fermi level pinning seems to be removed.
Differential Absorption Lidar at 1.67 µm for Remote Sensing of Methane Leakage
Authors: Kouki Ikuta Kouki Ikuta , Noboru Yoshikane Noboru Yoshikane , Nilesh Vasa Nilesh Vasa , Yuji Oki Yuji Oki , Mitsuo Maeda Mitsuo Maeda , Michihiro Uchiumi Michihiro Uchiumi , Youichirou Tsumura Youichirou Tsumura , Jun Nakagawa Jun Nakagawa , Noriyuki Kawada Noriyuki Kawada
Published: October 2002

A differential absorption lidar (DIAL) for field monitoring of methane (CH4) leakage at a wavelength of 1.67 µm was developed. Compared with traditional DIAL systems for environmental monitoring, this system has a higher distance resolution (∼15 m) for determining the leak position and a shorter detection range up to 500 m. First, considering appropriate design parameters, a theoretical simulation was performed to evaluate the sensitivity and the detectable range of the system. Based on the analytical simulation, a prototype DIAL system was constructed and the detection of CH4 which had leaked into the atmosphere was demonstrated. The CH4 leakage of 6000 ppm·m at a distance of 130 m was successfully detected. The detection limit was 1000 ppm·m. With the improvements in the light source and the detector system, the detectable boundary can be increased in the range from 90 to 540 m for a concentration of 1500 ppm·m.
Systematics of Electrical Conductivity across InP to GaAs Wafer-Fused Interfaces
Authors: Hammar Mattias , Wennekes Frank , Salomonsson Fredrik , Bentell Jonas , Streubel Klaus , Rapp Stefan , Keiper Dietmar , RalfWestphalen RalfWestphalen
Published: October 2002

We report on the electrical and compositional characterization of wafer-fused isotype
heterojunctions between Zn-, C- or Si-doped GaAs and Zn- or Si-doped InP. The junctions
were characterized by current-voltage and secondary ion mass spectrometry (SIMS)
measurements. It is demonstrated that very low-resistive junctions can be obtained in each
case, but also that there is a strong influence from the detailed sample structure and processing
conditions. SIMS was used to monitor the doping concentration across the interface as well as
the impurity concentrations of oxygen, carbon and iron.
Interfacial Reaction and Electrical Properties in the Sputter-Deposited Al/Ti Ohmic Contact to n-InP
Authors: Takeyama Mayumi B. , Noya Atsushi , Hasegawa TamotsuHashizume
Published: October 2002

The reaction and/or diffusion in the Ti metallizing Al/Ti/n-InP
contacts and their correlation with electrical properties have been
studied. In the as-deposited Al/Ti/InP contact, interaction between
Ti and P and outdiffusion of In into the Ti layer were observed in
the initial stage of the reaction process. The reaction between Ti
and P resulting in Ti-P compounds and the segregation of decomposed
In proceeded during rapid thermal annealing (RTA) treatment, and a
stable contact configuration of Al/Ti/In/Ti-P/InP was obtained after
RTA treatment at 600°C for 20 s. An extremely low Schottky
barrier height of 0.14 eV was obtained for the as-deposited
contact. An ohmic I–V characteristic of the contact
without Schottky barrier is demonstrated after RTA treatment. The
formation of stable Ti-P compounds seems to be related to the ohmic
behavior of the contacts.
InAlAs/InGaAs Metamorphic High Electron Mobility Transistors on GaAs Substrate: Influence of Indium Content on Material Properties and Device Performance
Authors: Cordier Yvon , Bollaert Sylvain , Zaknoune Mohammed , Dipersio Jean , Ferre Denise
Published: October 2002

The development of lattice mismatched InAlAs/InGaAs high electron mobility transistors on high-quality GaAs substrates (metamorphic HEMT) is of primary interest for millimeter-wave devices. These heterostructures grown on lattice mismatched substrates allow an extension of the composition range in the structures and to exploit enhanced properties, provided that the crystalline perfection of the layers as well as electrical quality are preserved. The aim of this work is to study the influence of indium mole fraction on material properties as well as its consequences on device performance.
Hole Trapping in Molecularly Doped Polymers: The Hoesterey-Letson Formalism
Authors: Borsenberger P. M. , Gruenbaum W. T. , Magin E. H. , Schildkraut D. E. , Visser S. A.
Published: October 2002

Hole trapping has been investigated in
di-p-anisyl-p-tolylamine (DAT), tri-p-tolylamine (TTA),
di-p-tolylphenylamine (DTP), and diphenyl-p-tolylamine (DPT) doped
poly(styrene) containing different concentrations of
tri-p-anislyamine (TAA). From oxidation potential measurements, TAA
is a trap for DAT, TTA, DTP, and DPT with depths 0.07, 0.22, 0.27, and
0.34 eV, respectively. In such a way, it is possible to investigate
the effect of trap depth using the same trap molecule. The mobilities
decrease with increasing trap depth and concentration. For a TAA molar
concentration of 10-2, the room temperature mobilities are
suppressed by as much as four orders of magnitude. The results are
compared to predictions of the Hoesterey-Letson formalism and
discussed within the framework of the recent simulations of Wolf et al.. [Chem. Phys. 222 (1997) 259] and Borsenberger
et al.. (submitted to Chem. Phys.)
Highly Stable Device Characteristics of InP-Based Enhancement-Mode High Electron Mobility Transistors with Two-Step-Recessed Gates
Authors: Tetsuya Suemitsu Tetsuya Suemitsu , Haruki Yokoyama Haruki Yokoyama , Yohtaro Umeda Yohtaro Umeda , Takatomo Enoki Takatomo Enoki , Yasunobu Ishii Yasunobu Ishii
Published: October 2002

High-performance 0.1-µm-gate InP-based enhancement-mode high
electron mobility transistors (E-HEMTs) were fabricated using
two-step-recessed-gate technology, where the gate recess etching is first
carried out by wet-chemical etching to removed n+-cap layers and then
by Ar plasma etching to remove the InP etch stopper layer.
Etching selectivies for both steps are sufficient not to degrade the
uniformity of the device characteristics.
The main advantage over the conventional approach for E-HEMTs,
Pt-based-gate technology, is the fact that the stability of the threshold
voltage is improved by means of a refractory gate metal, WSiN.
The change in the threshold voltage is only 50 mV after 160-h bias and
thermal stress at 195°C.
Passivation of InP-Based Heterostructure Bipolar Transistors in Relation to Surface Fermi Level
Authors: Kikawa Takeshi , Takatani Shinichiro , Tanoue HiroshiMasuda
Published: October 2002

The effect of surface Fermi level position on dc-characteristics of InP-based heterostructure
bipolar transistors (HBT) is reported. The Fermi level of an InP surface covered with silicon oxide
was located at an energy position close to the conduction band minimum of InP. This implies that an
electron accumulation layer forms at the interface, which acts as a surface leakage path. The HBT
passivated with silicon oxide films showed large excess base current and poor current gain. In contrast,
the Fermi level position at the silicon nitride/InP interface was found to be near the midgap, and no
electron accumulation layer was formed at the interface. The HBT passivated with silicon nitride film
showed excellent dc characteristics with very small, excess base
current.
GaInAsP/InP Attenuator Integrated Waveguide Photodetector (AIPD) Based on the Franz-Keldysh Effect
Authors: Yokouchi Noriyuki , Yoshida Junji , Yamanaka Nobumitsu , Yamaguchi Takeharu , Nishikata Kazuaki
Published: October 2002

A waveguide photodetector monolithically integrated with an optical attenuator
based on the Franz-Keldysh effect at the input section is proposed. The effective
sensitivity of the device can be controlled by applying the reverse bias at the attenuator
section. Using this device, the realization of a receiver module with low power
consumption and small signal distortion under high input power can be expected. In our
first demonstration, the intrinsic sensitivity of the device without attenuation is 0.25 A/W. The largest variable sensitivity range of 11 dB is realized at the reverse bias of 32 V.
An Optoelectronic Logic Gate Monolithically Integrating Resonant Tunneling Diodes and a Uni-Traveling-Carrier Photodiode
Authors: Akeyoshi Tomoyuki , Shimizu Naofumi , Osaka Jiro , Yamamoto Masafumi , Ishibashi Tadao , Sano Kimikazu , Murata Koichi , Sano Eiichi
Published: October 2002

InP-based InGaAs/AlAs/InAs resonant tunneling diodes (RTDs) and a uni-traveling-carrier photodiode (UTC-PD) are monolithically integrated to construct an optoelectronic logic gate. RTD structures are regrown by molecular beam epitaxy on the top of UTC-PD structures grown by metalorganic chemical vapor deposition. The characteristics of the regrown RTDs are almost the same as those of conventional RTDs directly grown on semi-insulating InP substrates. The UTC-PD provides a sufficient current drivability along with a high-speed operation demonstrated by the 3-dB bandwidth of 80 GHz, even at the low bias voltage corresponding to the peak voltage of the RTD. An optoelectronic logic gate using two RTDs and one UTC-PD was fabricated. This simple optoelectronic logic gate exhibited high-speed delayed flip-flop operation of 40 Gbit/s at a small power consumption of 7.75 mW. These results suggest that an optoelectronic logic gate using RTDs and a UTC-PD is suitable for the construction of ultrahigh-speed and low-power optoelectronic circuits.
All-Epitaxial Single-Fused 1.55 µm Vertical Cavity Laser Based on an InP Bragg Reflector
Authors: Rapp Stefan , Salomonsson Fredrik , Streubel Klaus , Mogg Sebastian , Wennekes Frank , Bentell Jonas , Hammar Mattias
Published: October 2002

We have realised an all-epitaxial 1.55 µm vertical cavity laser by employing a single wafer-fusion step. The laser structure is fabricated by fusing a 32-period p-doped (C) AlGaAs/GaAs top mirror onto a half-cavity structure consisting of a 50-period n-doped (Si) GaInAsP/InP bottom mirror and a 9 quantum well GaInAsP-active material. Laser mesas are fabricated using a wet etching procedure for the top mirror. The top mirror also contains an AlAs layer for oxidation for current confinement. The lasers operate pulsed at temperatures up to 40°C and at pulse lengths of 10 µs up to 5°C. The minimum threshold current density at room temperature is 1.8 kA/cm2 for a device diameter of 55 µm. Compared to nonoxidised laser diodes, the threshold current is markedly decreased in oxidised laser diodes.
Efficient All-Optical Interband Light Modulation by Ultrafast Manipulation of Intersubband Transitions in an Asymmetric Quantum Well*
Authors: Neogi Arup , Yoshida Haruhiko , Mozume Teruo , Wada Osamu
Published: October 2002

An efficient modulation scheme at relatively lower control light
intensities is proposed using ultrashort interband and
intersubband-resonant coupling light pulses
in a novel asymmetric In
x
Ga1-x
As/AlAs semiconductor quantum
well structure. The shape
of the intersubband-control light pulses can
manipulate the interband-signal light pulse absorption. The carrier
relaxation rate of the
quantum well system
can be estimated from the interband nonlinear optical parameters
induced by the intersubband control light field. The modulation
efficiency in the proposed structure is twice than in a conventional
symmetric quantum well
structure. This reduces the
threshold optical energy below 1 pJ in a 100-µm2 waveguide
structure on using 500 fs control light pulses owing to the enhanced
optical nonlinearities in the
proposed structure.
Observation of Negative Differential Resistance in µc-Si:H/a-Si1-xCx:H Double Barrier Devices
Authors: Yu Zhenrui , Pereyra Ines , Carreño M. N. P.
Published: October 2002

This article presents the experimental results on the preparation and
characterization of µc-Si:H/a-Si1-x
C
x
:H single barrier (SBD) and double barrier devices (DBD).
For DBDs, very clear negative differential resistance (NDR) regimes accompanied by oscillations
were observed. The observed NDR and oscillations can be explained by the quantum size effect.
Pulse-mode Selective Metal-organic Vapor Phase Epitaxy Method for Migration Enhancement and High-quality Strained InGaAsP Multi-quantum Well Structure
Authors: Sakata Yasutaka , Komatsu Keiro
Published: October 2002

A pulse-mode selective metal-organic vapor phase epitaxy (MOVPE) method for
achieving excellent crystal quality of an InGaAsP strained multi-quantum well (MQW)
structure on a narrow stripe region was investigated. The migration enhancement mechanism
for pulse-mode epitaxy was studied from the view point of the decomposition state of group-III sources. By using the proposed method, the flatness of the selectively grown layers was
drastically improved, and a very narrow photoluminescence spectrum linewidth of 28 meV at
25°C was realized for the strained MQW structure. The 1.3 µm-wavelength buried
heterostructure (BH) laser diode (LD) with a strained MQW active layer grown by the pulse-mode selective MOVPE showed a very low-threshold current of 12 mA (18 mA) and high-slope efficiency of 0.37 (0.33) W/A at the high temperature of 85°C (100°C).
Multidimensional Director Modeling Using the Q Tensor Representation in a Liquid Crystal Cell and Its Application to the π Cell with Patterned Electrodes
Authors: Mori Hiroyuki , Jr. Eugene C. Gartland, , Kelly Jack R. , Bos Philip J.
Published: October 2002

To estimate numerically multidimensional director
configurations in a liquid crystal cell, it is important to
use the Q tensor representation of the strain free energy because
it solves the problem of the difference between the directors, n
and -n, in the Frank-Oseen free energy representation. In this
paper, we discuss the numerical methods for calculating the
multidimensional director configurations, using Berreman's Q tensor
representation. Numerical issues discussed include the relaxation
method for the director calculation, the liquid crystal (LC)/glass
interface problem, the boundary conditions for the electric potential,
and the possible ways to obtain faster convergence. We compare the
calculated results obtained from the Frank-Oseen and Q tensor
representations. By considering a π cell with patterned
electrodes,
we show the consistency of the model used with experimental
observations. The calculated data explain well the position
shift of the defects that appear in the test π cell.
Calculation of Subband States in a Metal-Oxide-Semiconductor Inversion Layer with a Realistic Potential Profile
Authors: Miyazaki Khairurrijal , Hirose Masataka
Published: October 2002

The ground and higher subband states in a metal-oxide-Si(100) inversion layer are calculated for a logarithmic potential model, in which the wave functions
are represented by generalized Airy functions. It is found that the calculated subband
energy levels for the Padmanabhan-Rothwarf logarithmic potential model are much lower
than those self-consistently calculated. A modified Padmanabhan-Rothwarf
logarithmic potential model gives the subband energy levels and the spatial extent
of the electron density that agree well with those obtained from the self-consistent
calculations.
Structural and Ferroelectric Properties of Sol–Gel Deposited Nb-doped Pb[(Sc1/2Nb1/2)0.57Ti0.43]O3 Thin Films
Authors: Cho Chae-Ryong , Lee Won-Jae , Yu Byoung-Gon , Kim Bo-Woo , Park Kyung Bong
Published: October 2002

Ferroelectric 0.5 mol% Nb-doped Pb[(Sc1/2Nb1/2)0.57Ti0.43]O3 (PSNTN) thin films were successfully prepared by a sol-gel method. The optimal annealing temperature for the crystallization of the films was determined by differential thermal analysis (DTA). The degree of crystallinity for the films as a function of annealing temperature and thickness was characterized by the using X-ray diffraction technique. The Curie temperature of the film was 212°C, which is lower than 248°C for bulk PSNTN ceramics. Typical P–E hysteresis was observed in all films annealed above 600°C. The remanent polarization and the coercive field of the 0.4-µm-thick film annealed at 700°C were 21 µC/cm2 and 32 kV/cm, respectively. Both the effect of annealing temperature on the top electrode and the effect of polarity on the ferroelectric properties of the PSNTN were investigated. Better insulating properties of the films on Pt/Ti, compared to those of the films on Pt/TiO2, are observed.
The Electroclinic Response in a Network-Stabilized Cholesteric Phase
Authors: Karlsson Mona , Komitov Lachezar , Lagerwall Sven T.
Published: October 2002

The electroclinic effect is a very fast response of the optic axis in chiral orthogonal smectics (like
SmA*) on the application of an electric field. In smectic systems it represents a soft mode which takes on a high
amplitude near the A*→C* transition but otherwise is limited to a tilt of typically 2–5°. This response can also be
found in chiral nematics, although its origin here is still obscure and so small–typically 0.1° or less–that it has been of academic interest only. In two cases investigated of a cholesteric phase which has a direct transition to
SmC*, the electroclinic effect could be enhanced to the same level as in SmA* materials by photoreticulation
without slowing down the response speed. Remarkably, the temperatures at which this high amplitude/high
speed response is measured are actually lower than in the corresponding measurements on the basic mixtures.
Crystal Growth, Thermal and Laser Properties of Neodymium-doped Strontium Fluorapatite
Authors: Zhang Huaijin , Meng Xianlin , Zhu Li , Wang Changqing , Wang Pu , Yang Zhaohe , Chow Y. T. , Dawes Judith
Published: October 2002

In this paper, the neodymium-doped strontium fluorapatite crystal has been grown
by the Czochralski method. The data of thermal expansion and specific heat of the
crystal have been measured. The thermal expansion coefficients along X and Z direction
are α1=11.4×10-6/K and α3=12.3×10-6/K respectively. The specific heat is
110 cal/mol·K at 330 K. The measured absorption spectra from 400 nm to 850 nm show
that the crystal has absorption peaks around 805.5 nm, and the absorption coefficients
at 805.5 nm are 16.05 cm-1 and 5.59 cm-1 for π and σ polarization respectively. The
polarization fluorescence spectra at room temperature show that the strongest
fluorescence is centered at 1058.8 nm. The lifetime of 4F3/2 is 175 µs for 1 at.% Nd3+
doped in the crystal. The laser at 1058.8 nm is demonstrated pumped by a 3W cw laser
diode at 805.5 nm, and the slope efficiency is 31.7%.
Behaviors of Excitation Cross Sections in the Intermediate Velocity Regime on Ion-Atom Collisions
Authors: Rei Okasaka Rei Okasaka , Yoshiho Seo Yoshiho Seo , Satoshi Tojo Satoshi Tojo , Yasuo Matsumura Yasuo Matsumura
Published: October 2002

We studied the behaviors of excitation cross sections
and electron capture cross sections
as functions of collision velocity using previous data of various collision systems.
The structures peculiar to the intermediate velocity regime
were recognized on the excitation cross sections.
Close correlation of the excitation cross section
to the electron capture cross section and
a relaxation time longer than that for the electron capture process characterize
the excitation process in the intermediate velocity regime.
A model consisting of a two-step electron transfer process
well explains the characteristics of the excitation cross sections
in the intermediate velocity regime.
Characterization of Microbridges Generated on Negative Resist Patterns
Authors: Keisuke Nakazawa Keisuke Nakazawa , Eishi Shiobara Eishi Shiobara , Masafumi Asano Masafumi Asano , Yasuhiko Sato Yasuhiko Sato , Satoshi Tanaka Satoshi Tanaka , Yasunobu Oonishi Yasunobu Oonishi
Published: October 2002

We analyze the mechanism of microbridge formation on chemically amplified negative resist patterns through direct observation of progressive development in alkali-developers. The microbridge formation was attributed to contact occurring between adjacent resist patterns due to swelling of the resist. These swollen resist patterns contracted upon immersion in deionized water; however, bridge structures remained as microbridges between these patterns. The swelling of the resist films occurred more easily at defocus positions than at a focus center, and the microbridges localized near the top of the pattern at defocus positions and delocalized at a focus center. An optical simulation suggested that both the crosslinking density and its distribution determine the number and position of the microbridges. A scaling law governing microbridge formation is observed as a function of focus position and exposure dose.
Fundamental Principles of Crosstalk in Optical Data Storage
Authors: Milster Tom D. , Upton Robert S.
Published: October 2002

Cross talk in the read out signal resulting from narrow track pitches is analyzed with a
Babinet decomposition of the light reflected from the disk surface. Results indicate that the
commonly used technique of measuring cross talk does not adequately describe the temporal
behavior of cross talk effects because the intermodulation of the scan-track mark pattern and the
adjacent-track mark pattern is not considered. Our analysis takes this inter-modulation into
account and shows its significance. The analysis presents a fundamentally new way to
conceptualize cross talk in which effects due to different terms of the Babinet decomposition can
be studied separately or combined in meaningful signal groups that relate directly to
measurements. Example calculations are presented that illustrate the behavior of the readout
signal from optical disks that might be used for land-and-groove recording.
Quantification of cross talk effects are presented with respect to shifts of signal transitions.