bluuebunny/crossref_metadata_2025 huggingface dataset:
GaN-Passivation of GaAs with Less Plasma Damages: Effects of Input Plasma Power, Substrate Heating and Post-Thermal Annealing
Authors: Hidetoshi Tanemura Hidetoshi Tanemura , Keisuke Kanazawa Keisuke Kanazawa , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

In order to achieve the plasma-damage-free GaN passivation of GaAs, GaAs (100) substrates were nitrided in helicon-wave-excited N2–Ar plasma with reduced input plasma power (260 W → 180 W) and substrate heating at 200°C together with the post-thermal annealing in N2 ambient. The current-density–voltage (J–V) characteristics of Schottky or tunnel metal-insulator-semiconductor (MIS) diodes were measured to evaluate the effects of the reduced plasma damage and the extent of the passivation. The reverse leakage current decreased substantially as the input plasma power was reduced from 260 W to 180 W. Substrate heating at 200°C and the post-thermal annealing in N2 ambient were also effective in diminishing the reverse leakage current. The extent of the decrease in the carrier density observed near the GaN/GaAs interface was also improved by the above treatment. The thermal stability was also greatly improved by GaN passivation. The ideality factor and Schottky barrier height did not show any degradation up to the annealing temperature (of the diode samples) of as high as 500°C. The J–V characteristics did not show any deterioration for the GaN-passivated GaAs samples even after long-time (3–16 months) exposure to air, while they showed remarkable degradation for the untreated GaAs sample after air exposure of only 3 weeks.
Electrical Characterization of SrTiO3 Thin Films Grown on Nb-Doped SrTiO3 Single Crystals
Authors: Morito Kentaro , Suzuki Toshimasa , Sekiguchi Shoichi , Okushi Hideyo , Fujimoto Masayuki
Published: October 2002

SrTiO3(100) films homoepitaxially grown on Nb-doped SrTiO3(100) substrates with
various Nb concentrations and SrTiO3(111) films epitaxialy grown on the [111]-oriented Pt
thin-film electrode formed on SiO2/Si substrates with Ta buffer layers were prepared by the
helicon sputtering method. After the top Pt electrode formation, the obtained Pt/SrTiO3/SrTiO3:Nb metal-insulator-semiconductor (MIS) capacitors and
Pt/SrTiO3/Pt/Ta/SiO2/Si metal-insulator-metal (MIM) capacitors were electrically
evaluated by current versus bias voltage characteristic (I–V) and capacitance versus bias
voltage characteristic (C–V) measurements to clarify the specific features of the
SrTiO3/SrTiO3:Nb interface compared with the SrTiO3/Pt interface. The existence of a
space charge layer at the SrTiO3/SrTiO3:Nb interface was
clearly characterized.
Improvement in Performances of ZnO:B/i-ZnO/Cu(InGa)Se2 Solar Cells by Surface Treatments for Cu(InGa)Se2
Authors: Saito Sutichai Chaisitsak
Published: October 2002

Solar cells based on Cu(InGa)Se2 (CIGS) thin films fabricated by selenization/sulfurization were investigated. We have concentrated on studying the heterojunction quality to improve the efficiency and stability of n-ZnO/i-(atomic layer deposition :ALD)ZnO buffer-layer/p-CIGS structure devices. The effect of heat treatment for CIGS absorbers was studied. It is found that the heat-treatment can remove entities, e.g., excess In
x
S
y
, from the surface of CIGSS, which causes interdiffusion in the (ALD)ZnO buffer layer and decreases V
oc and FF. We achieved 13.9% efficiency (V
oc: 510 mV, FF: 0.736, J
sc: 36.9 mA/cm2) without the use of Cd-related material. Reversible light-soaking and current-injection effects were observed clearly in i-(ALD)ZnO/CIGS-based solar cells. These phenomena can be controlled by changing the CIGS surface conditions. Devices treated with NH4OH as well as deionized water in an ultrasonic bath prior to the growth of buffer layers are not sensitive to light illumination or application of bias voltage in the dark. The origin of the light-soaking/current-injection effect is assumed to be at/near the CIGS surface or grain boundaries.
Atomic Layer Epitaxial Growth of ZnSxSe1-x on Si Substrate
Authors: Yokoyama Meiso , Chen Nyen-Ts , Ueng Herng-Yih
Published: October 2002

High-quality undoped ZnSSe epitaxial layers are successfully
grown on (100)-Si substrates by atomic layer epitaxy (ALE) in a
modified low-pressure horizontal metal organic chemical vapor
deposition (MOCVD) system using DMZn, H2S and H2Se as
reactants at a growth temperature of 175°C and a growth
pressure of 30 Torr. The vapor-solid relationship for the group VI
elements are obtained experimentally. The lattice of the
ZnS
x
Se1-x
layer with sulfur content estimated to be about
93% is found to have the best lattice match to the Si substrate, as
indicated by the good layer thickness uniformity, surface morphology
and narrow X-ray diffraction rocking curve linewidth with a minimal
FWHM of about 0.16° (570 arcsec). In addition, PL spectra
exhibited a strong near-band-edge emission and weak deep-level
emissions in the longer wavelength region for the epitaxial layer of
ZnS0.93Se0.07. Results indicate good lattice match because
of a low number of interfacial and epitaxial layer defects.
Performance of AlN/GaN Heterostructure Metal Insulator Semiconductor Field Effect Transistor Based on Two-dimensional Monte Carlo Simulation
Authors: Imanaga Syunji , Kawai Hiroji
Published: October 2002

We performed a two-dimensional Monte Carlo simulation of an AlN/GaN
heterostructure metal insulator semiconductor field effect transistor
(hetero-MIS-FET). The vertical structure of the FET is AlN(6 nm)/GaN, and the gate
length, the gate-to-source length and the gate-to-drain length are 0.2 µm,
0.2 µm and 0.4 µm, respectively. We assume that GaN and AlN are wurtzite
structures and are grown along the c-axis. We took account of the total electric
polarization of AlN of 3×10-6 C cm-2 due to piezoelectric and
spontaneous polarization. Three valley models for the conduction band of GaN and AlN
are employed. The maximum value of the cutoff frequency f
T and the
transconductance G
m are about 100 GHz (I
d=2 A/mm) and
2 S/mm (V
g=0.5 V), respectively. The high f
T and
G
m values and high I
d value when f
T is at the
maximum strongly suggest that the AlN/GaN hetero-MIS-FET has high potential as a
high-frequency, high-power device.
Evidence of Mobile Ag and Growth Mechanism of YBa2Cu3O7-y Films Deposited on Cube Textured Ag Tape by Chemical Vapor Deposition
Authors: Hasegawa Masato , Yoshida Yutaka , Iwata Morihiro , Akata Hiroyuki , Higashiyama Kazutoshi , Takai Yoshiaki , Hirabayashi Izumi
Published: October 2002

YBa2Cu3O7-y
(YBCO) films were prepared on
{100}<001> cube textured Ag tape (CUTE-Ag tape) by metal organic
chemical vapor deposition (MOCVD) using a liquid state metal organic (MO) source.
Numerous spiral steps accompanied by screw dislocations were observed and many
particles were observed on the terrace surface of the spiral steps by atomic force
microscopy (AFM). We observed a change in surface morphology before and after heat
treatment in vacuum at 550°C. After heat treatment, these particles became
smaller and concentrated at the edge of the spiral steps. We confirmed by scanning
Auger microscopy that the main composition of these particles was Ag. We propose a
growth mechanism on a Ag substrate in which Ag segregates to the surface and acts as
surfactant for YBCO growth.
Low-resistance InGa(Al)As Tunnel Junctions for Long Wavelength Vertical-cavity Surface-emitting Lasers
Authors: Markus Ortsiefer Markus Ortsiefer , Robert Shau Robert Shau , Gerhard Böhm Gerhard Böhm , Fabian Köhler Fabian Köhler , Gerhard Abstreiter Gerhard Abstreiter , Markus-Christian Amann Markus-Christian Amann
Published: October 2002

A new method is proposed for a significant reduction of series resistance and device heating in long wavelength vertical-cavity surface-emitting lasers (VCSELs) based on InP. Our technique involves a twofold epitaxial growth with a buried low-resistance (3×10-6 Ωcm2) tunnel junction. The substitution of high-resistive p-type confining layers by low-resistive n-type material results in total resistances smaller 100 Ω even for the case of non-conducting dielectric mirrors. With the application of buried tunnel junctions in a VCSEL-structure, we could demonstrate small electrical series resistance (U < 1 V at 3 kAcm-2) and effective current confinement simultaneously. Furthermore, because of the laterally varying cavity length, an effective lateral waveguiding effect occurs.
Over 15-GB Capacity Domain Wall Displacement Detection Magneto Optical Recording Using a Digital Versatile Disc Dimensional Optical Head
Authors: Kai Shinichi , Fukumoto Atsushi , Aratani Katsuhisa , Yoshimura Shunji , Tsutsui Keiichi , Arai Masayuki , Takeshita Yasuyuki
Published: October 2002

High-density magneto-optical (MO) recording using a land/groove structured
domain wall displacement detection (DWDD) medium has been achieved with a digital
versatile disc (DVD) dimensional optical head including a 664-nm wavelength laser
diode and a 0.60-NA objective lens. Due to the deep groove depth, easy
domain wall displacement is obtained without the use of a track boundary postannealing
process. Sufficient readout performance is obtained in experiments at an areal
recording density of 11 Gbit/inch2, which is obtained using a 0.13-µm bit length
and a 0.45-µm track pitch. This areal density corresponds to a capacity of 15 GB
per one 120-mm-diameter disk.
Optical Properties of Sol–Gel Processed Amorphous and Crystalline SrTiO3 Thin Films
Authors: Thomas Reji , Dube D. C.
Published: October 2002

Transparent strontium titanate thin films were prepared on fused silica substrate by spin-on sol–gel process using strontium 2-ethyl hexanoate and titanium isopropoxide as precursors in ethanol medium. The lattice constants of crystalline films were a=b=c=3.91 Å. Optical constants of the films in amorphous and polycrystalline forms were measured in the wavelength range of 300 nm to 900 nm with the aid of transmission spectra. The observed band gaps for amorphous and crystalline films were 4.07 eV and 3.62 eV respectively. The refractive index (n) and extinction coefficient (k) at 610 nm for the amorphous films are 1.72 and 0.0022 and for the crystalline films the corresponding values are 1.88 and 0.0062. Packing density of the amorphous and crystalline films were 0.65 and 0.75 respectively. The polycrystalline films have a lower n and k in a 350–850 nm wavelength range and higher band gap as compared to single crystal data. The dispersion data of the refractive index is interpreted with the single oscillator model. Using this model, the values obtained for oscillator strength (S
0) and oscillator energy (ε0) were 0.64 ×1014 m-2 and 7.31 eV respectively for the amorphous film and 0.43 ×1014 m-2 and 5.69 eV for crystalline films.
A New Technique to Eliminate the 90° Domains in BaTiO3 Crystal Fibers
Authors: Jyh-Chen Chen Jyh-Chen Chen , Yeou-Chang Lee Yeou-Chang Lee , Sheuan-Ping Lin Sheuan-Ping Lin
Published: October 2002

A non-destructive method to eliminate the 90° domains
in BaTiO3 crystal fibers has been developed. We employ a
vibration system to apply a cyclic force on the a-faces of the
crystals. An accumulation of the vibrating force achieves a higher
force, which dissipates the internal stress of the crystal. The
results show that the 90° domains are easily diminished
with only a slight force pressed to the crystal surface.
Application of HfN/Hf Bilayered Film as a Diffusion Barrier for Cu Metallization System of Si Large-Scale Integration
Authors: Ken-ichi Yoshimoto Ken-ichi Yoshimoto , Satoko Shinkai Satoko Shinkai , Katsutaka Sasaki Katsutaka Sasaki
Published: October 2002

As a preliminary examination for improving the reliability of the Cu metallization system of Si-LSI, we prepared Cu/Hf/Si, Cu/CuHf2/Hf/Si and Cu/HfN/Hf/Si contact systems, and compared their thermal stabilities. The change in crystal structure and the interdiffusion behavior were investigated by X-ray diffraction and Auger electron spectroscopy, respectively. In the case of Cu/CuHf2/Hf/Si, its thermal stability was slightly superior to that of Cu/Hf/Si without the CuHf2 layer. However, slight outdiffusion of Si to the Cu surface was also observed, similar to the case of Cu/Hf/Si. On the other hand, the Cu/HfN/Hf/Si system was satisfactorily stable up to 630°C. In addition, it was revealed that Hf silicide containing Hf3Si2 that has the lowest contact resistivity can be maintained at the Si interface up to 630°C.
Nonlinear Susceptibility of Second Harmonic Generation Corresponded to the Diamond (100) Surface Structures
Authors: Xiao Changyong , Zhang Mikka Nishitani-Gamo , Tamura Hiroyuki , Zhou Hui , Takami Seiichi , Kubo Momoji , Miyamoto Akira , Ando Toshihiro
Published: October 2002

In order to investigate the relation between the diamond (100) surface structures
and their nonlinear susceptibility of second harmonic generation (SHG), we optimized
the surface geometries and calculated their electronic structures by using a
semiempirical method of quantum chemistry with cluster models. The optimized
geometries agreed well with experimental results. The diamond
(100)-(1×1)-2H surface showed the minimum value of the surface SHG among
the optimized geometries of the diamond surface. Decrease of the chemisorbed hydrogen
on the surface resulted in increase of the surface SHG. The existence of surface
dimers can enhance the surface SHG.
Properties of Germanium-Doped Indium Oxide Thin Films Prepared by DC Magnetron Sputtering
Authors: Mizuno Masao , Miyamoto Takashi
Published: October 2002

Ge-doped indium oxide (In2O3) thin films were prepared by dc
magnetron sputtering. The electrical resistivity,
1.6×10-4 Ω·cm, of the film deposited at 200°C
was obtained at 5.5% Ge doping. This was comparable with that of ITO (tin-doped
In2O3) films. Furthermore, amorphous films with Ge content higher than
5.0% were obtained when the substrate temperature was 20°C, while they were
obtained with Ge content higher than 7.0% when the substrate temperature was
200°C. The electrical resistivity of 6.0% Ge-doped amorphous In2O3
film deposited at 20°C is 4.1×10-4 Ω·cm. The
etching rate of the film by 5% HCl is 1400 Å/min and is nine times as high as
that of ITO films.
Stranski-Krastanov Growth of Al on Ag Layers during Molecular Beam Epitaxy of (111) Al/Ag Superlattices
Authors: Toshiki Kingetsu Toshiki Kingetsu , Yasuhiro Kamada Yasuhiro Kamada , Masahiko Yamamoto Masahiko Yamamoto
Published: October 2002

We studied the growth behavior of (111) Al/Ag superlattices during molecular beam epitaxy, using in situ reflection high-energy electron and ex situ X-ray diffractions. Epitaxial growth proceeded with an orientational relationship of Al(111)[110] ∥Ag(111)[110]. Although the first Al layer with 3-monolayer (ML) thickness grown on a Ag buffer layer did not show island growth, the second and succeeding (111) Al layers with 3-ML thickness were found to grow on Ag underlayers in the Stranski-Krastanov mode, in contrast to the layer growth of (001) Al/Ag superlattices reported previously. The critical Stranski-Krastanov thickness was seemingly 2 ML, and three-dimensional islands emerged upon further growth. Thus, superlattices with 3-ML-thick Al layers showed rough Al/Ag interfaces due to the presence of Al islands, while superlattices with 2-ML-thick Al layers exhibited rather flat interfaces. The strain relief of Al upon the formation of islands was detected. We discussed the possible cause of the difference in growth behavior between the (111) and (001) superlattices.
In Situ Fourier-Transform Infrared Study of Electron-Irradiation-Induced Reaction in a C60 Film
Authors: Toshiki Hara Toshiki Hara , Jun Onoe Jun Onoe , Hideki Tanaka Hideki Tanaka , Yunzhi Li Yunzhi Li , Kazuo Takeuchi Kazuo Takeuchi
Published: October 2002

The reaction between C60 molecules in a 3-keV electron-irradiated C60 thin film has been studied using in situ Fourier-transform infrared (FTIR) spectroscopy and ex situ laser-desorption FT-mass spectrometry (LD-FTMS). The results of FTIR and LD-FTMS measurements indicate that coalesced C120 species were formed as a main product in the electron-beam (EB)-irradiated film. We studied the kinetics of the reaction by examining the decrease in the amount of C60 molecules as a function of irradiation time and found that the reaction rate exhibits a linear dependence on the reactant concentration and a third-power dependence on the electron dose rate.
Monte Carlo Simulation of Secondary Electron Emission from Tungsten Surfaces with Various Work Functions as Applied to Sc/W Surfaces
Authors: Takashi Kawano Takashi Kawano , Z.-J. Ding Z.-J. Ding , Ryuichi Shimizu Ryuichi Shimizu
Published: October 2002

To elucidate the secondary electron emission from tungsten surfaces of various work functions, as experimentally prepared by scandium deposition onto a W(100) surface, a Monte Carlo simulation of energy distribution of secondary electrons, N
S(E), emitted from tungsten surfaces with various work functions has been performed for comparison with the measured distribution from a Sc/W(100) surface. The Monte Carlo simulation described the shift of the onset of N
S(E) with considerable success and, furthermore, successfully predicted the appearance of a hump at around 20 eV in N
S(E), which has long been a question awaiting explaination.
In-line Optical Lever System for Ultrasmall Cantilever Displacement Detection
Authors: Kikukawa Atsushi , Koyanagi Hajime , Etoh Kimitoshi , Hosaka Sumio
Published: October 2002

Cantilevers as small as 10 µm in length are required in order to achieve a practical data transfer rate in a read-only memory system using cantilevers as head. Thus, a new optical lever design concept that can detect the motion of such small cantilevers is necessary. The new optical lever concept that we propose makes it possible to use an objective lens with a high numerical aperture and to reduce the expansion rate of the projected light source image on the cantilever surface. As a result, we were able to reduce the incident laser spot diameter to 5 µm. It was also possible to expand the operation bandwidth to 10 MHz while achieving a displacement sensitivity of 0.48 Å (when a 10-µm long cantilever was used) by using a small spot position sensor, because the laser spot diameter on the detector could to be reduced to an arbitrary size.
Dependence of the Nuclear Excitation by Electron Transition on the Decay Rate
Authors: Yasutaka Sumi Yasutaka Sumi , Satoru Tanaka Satoru Tanaka
Published: October 2002

Nuclear excitation by electron transition (NEET) is understood as a resonance phenomenon between the excited atomic state and the nucleus. In the situation where the strong external radiation field transfers energy to a nucleus through the excitation of the atomic shell, e.g., the laser-assisted inverse electron bridge process, the decay rate variation of the initial or final state in the NEET process plays an essential role in the NEET probability. The dependence of the NEET probability on this variation is analyzed in detail with the solution of the equation of motion in the NEET process, and the calculation using 197Au is shown as an example.
Development of Photochemical Analysis System for F2-Excimer Laser Lithography Processes
Authors: Sekiguchi Atsushi , Kadoi Mikio , Miyake Yasuhiro , Matsuzawa Toshiharu
Published: October 2002

A system for photochemical analysis of F2-excimer laser lithography
processes has been developed. The system, VUVES-4500, consists of 3 units: (1) an
exposure and bake unit that uses the F2-excimer laser to carry out a flood
exposure and then post-exposure bake (PEB), (2) a unit for measurement of the
development rate of photoresists, and (3) a simulation unit that utilizes PROLITH of
profile simulation software to calculate the resist profiles and process latitude using
the measured development rate data. With this system, preliminary evaluation of the
performance of F2-Excimer laser lithography can be performed without the use of
a lithography tool capable of imaging and alignment. Profiles for 150 nm lines are
simulated for the PAR-101 resist (manufactured by Sumitomo Chemical) and the
SAL-601 resist (manufactured by Shipley), a chemically amplified resist that has
sensitivity at the F2-excimer laser wavelength. The simulation successfully
predicts the resist behavior. Thus it is confirmed that the system enables efficient
evaluation of the performance of F2-excimer laser lithography processes.
New Standby Degradation Mode in n-Channel MOSFETs with Thin Gate Oxide
Authors: Tanaka Hiroyuki , Shinohara Hirofumi , Uchida Hidetsugu , Ida Jiro
Published: October 2002

As a new standby degradation mode in n-channel
metal-oxide-semiconductor field-effect transistors (MOSFETs) with
thin gate oxide, the drain voltage was found to cause degradation of
transconductance in the linear region (Gm) while the
gate, source, and substrate were connected to ground as a standby
off-state condition. Although the gate voltage is 0 V,
Gm degradation has a power correlation to the stress
time. The degradation increases with decreasing gate length and
gate-oxide thickness. The estimated drain voltage and gate length
which caused 10% degradation of Gm in 10 years were
2.0 V and 0.11 µm, respectively for the samples with 3.2 nm
gate-oxide thickness. The degradation was found to be attributed
mainly to band-to-band tunneling in the gate-drain overlap
region. This degradation mode may possibly limit device scaling when
using thin gate oxide from the point of view of reliability.
Dielectric Degradation Mechanism of SiO2 Examined by First-Principles Calculations: Electronic Conduction Associated with Electron Trap Levels in SiO2 and Stability of Oxygen Vacancies Under an Electric Field
Authors: Kitagawa Isao , Maruizumi Takuya , Ushio Jiro , Kubota Katsuhiko , Miyao Masanobu
Published: October 2002

We studied the degradation mechanism of silicon dioxide under an
electric field using first-principles calculations. First, we
determined that the distance between oxygen vacancies primarily
plays the role of electronic interaction of electron trap levels and
that a critical distance of 12 Å, exists. At this critical
distance, the leakage conduction mechanism is varied from insulator
(hopping) to metallic. Second, we examined the stability of oxygen
vacancies under an applied field. We determined that the oxygen
vacancy pair within 7 Å is more stable than the one which is
further apart when it becomes positively charged under a high
field.
Metal-Oxide-Semiconductor Characteristics of NH3-Nitrided N2O-Annealed Oxides Fabricated at Reduced Pressure
Authors: Yoon Giwan , Epstein Yefim
Published: October 2002

In this paper, a new technique, namely, the fabrication of
NH3-nitrided N2O-annealed oxides (NNO) under reduced pressure, is
presented to attain the desired nitrogen concentrations and profiles
that eventually improve the hot-carrier lifetime and high immunity
to boron penetration. The proposed NNO dielectrics fabricated at
reduced pressure (<550 Torr) showed excellent hot-carrier
lifetimes and barrier properties to boron penetration without any adverse
effects on the electrical properties and reliability.
Low-Temperature Preparation of FeNx and Fe/FeNx Multilayer by Electron Shower
Authors: Yumoto Hisami , Suzuki Masashi , Li Song Ji , Tsuchiya Toshio
Published: October 2002

In the presence of a substrate bias (>-100 V), FeN
x
films were prepared at a low
temperature by the electron shower method. The nitride content was increased with increasing
N2 gas pressure and the structure of the films was changed as: Fe →Fe4N →Fe3 →Fe2N.
Multilayer films of (Fe+Fe4N)/(Fe4N+Fe3N) and Fe/Fe3N were prepared on glass and poly
ethylene terephthalate (PET) substrates, respectively, in the presence of a pulse of the substrate
bias. By the pulse of the electron shower, the Fe/Fe4N and Fe/Fe3N multilayer films were
prepared on glass and PET, respectively. When the gas pressure was
increased from 7×10-3 Torr to 11×10-3 Torr, Fe/Fe2N films were prepared on both the substrates. The concentration
(1 at.%) of N in these Fe layers prepared by the pulse of the electron shower was lower than that
(7 at.%) prepared by the pulsed bias. Multilayer films were prepared
from a single vapor source by these methods.
Low Voltage Saturation of Pb(ZrxTi1-x)O3 Films on (100)Ir/(100)(ZrO2)1-x(Y2O3)x/(100)Si Substrate Structure Prepared by Reactive Sputtering
Authors: Sadayoshi Horii Sadayoshi Horii , Seiji Yokoyama Seiji Yokoyama , Takuji Kuniya Takuji Kuniya , Susumu Horita Susumu Horita
Published: October 2002

The 37- to 280-nm-thick epitaxial
(001)Pb(Zr
x
Ti1-x
)O3(PZT) films were deposited by reactive
sputtering on the
(100)Ir/(100)(ZrO2)1-x
(Y2O3)
x
(YSZ)/(100)Si
substrate structures.
We investigated the film thickness and crystalline quality
dependences of the ferroelectrical property of the PZT film
from a viewpoint of low voltage saturation.
The samples were dipped in 61% HNO3 solution
prior to forming the top IrO2 electrode in order to
remove the surface decomposed layer of the PZT film.
By this HNO3-treatment,
the remanent polarization was increased, and the squareness
and symmetry of the polarization–voltage (P–V) hysteresis loop
of the PZT film were improved.
The P–V hysteresis loop of
the 54-nm-thick HNO3-treated epitaxial PZT film
was saturated at about 1.5 V.
Although the coercive field E
c was
increased by the HNO3-treatment,
the coercive voltage was decreased by decreasing the film
thickness. It was also found that E
c can be lowered by improving
the crystalline quality of the PZT film.
Improvement of Memory Retention Characteristics in Ferroelectric Neuron Circuits Using a Pt/SrBi 2Ta 2O 9/Pt/Ti/SiO 2/Si Structure-Field Effect Transistor as a Synapse Device
Authors: Sung-Min Yoon Sung-Min Yoon , Eisuke Tokumitsu Eisuke Tokumitsu , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

A metal-ferroelectric-metal-oxide-semiconductor field effect transistor (MFMOS-FET) with
a Pt/SrBi2Ta2O9/Pt/Ti/SiO2/Si structure was fabricated on a silicon-on-insulator (SOI) structure
in order to improve the memory retention characteristics of ferroelectric neuron circuit.
The area ratio of MOS capacitor to MFM capacitor was changed from 3 to 15 so that
charge quantities induced in both capacitors were optimized.
It was found that the memory operations and retention characteristics were considerably improved in the
fabricated MFMOS-FET with an area ratio larger than 10, compared with those of the MFSFET previously fabricated
using a Pt/SrBi2Ta2O9/Si structure. Next, a pulse frequency modulation (PFM)-type neuron circuit was
fabricated using the MFMOS-FET and a CMOS Schmitt-trigger oscillator as a synapse and a neuron, respectively,
and it was found that the oscillation frequency of the circuit remained almost unchanged over a period of 1 h.
Oxide-Mediated Solid Phase Epitaxy (OMSPE) of Silicon: A New Low-Temperature Epitaxy Technique Using Intentionally Grown Native Oxide
Authors: Mizushima Ichiro , Mitani Yuichiro , Miyano Kiyotaka , Kambayashi Shigeru
Published: October 2002

A new low-temperature epitaxial technique is proposed, which utilizes the native
oxide on the Si surface. A good quality epitaxial Si layer can be obtained using solid
phase epitaxy (SPE), mediated by an intentionally grown native oxide layer on the Si
substrate. Oxygen coverage of 0.25 ML was determined to be most suitable for obtaining
defect-free epitaxy. The mechanism of this new epitaxial technique is presented, based
on a detailed investigation of defect formation due to the oxygen at the interface.
A Low Thermal Budget High Performance 0.25–0.18 µm Merged Logic Device and Dynamic Random Access Memory Application
Authors: Yeh Wen-Kuan , Lin Yung-Chang , Chen Tung-Po , Huang Cheng-Tung , Chang Sun-Jay , Lin Wen-Jeng , Jung Le-Tien , Chien Sun-Chieh , Sun Shin-Wei , Liou Fou-Tai
Published: October 2002

Merged dynamic random access memory (DRAM) with logic technology
has been widely investigated because of to its high on-chip memory
bandwidth, low power consumption, customized memory size, and small
footprint advantages. A low thermal budget 0.25–0.18 µm
embedded DRAM technology has been developed to merge a
high-performance logic device and high-density DRAM on the same
chip. In this newly developed technology, shallow trench isolation,
a triple well, TiSi
x
polycide, titanium salicide, a
self-aligned contact poly-via and a low thermal budget
oxide-nitride-oxide (ONO) as well as Ta2O5 capacitor
dielectrics used for 1 Gbit DRAM design, are being applied. A
32 Mbit synchronous DRAM macro was designed based on this
technology and is proposed offered as a drop-in module for embedded
DRAM applications.
Effect of Wet Etched Thickness and Reoxidation on Reliability of Dual Gate Oxide for Sub-Quarter Micron Complementary Metal-Oxide-Semiconductor Devices
Authors: Cho Ihl Hyun , Sung Nag Kyunn , Oh Jong Hyuk , Park Min Soo , Sohn Dong Kyun , Park Jin Won
Published: October 2002

We investigated the effect of wet etched thickness and
reoxidation on the reliability of dual gate oxide. The dual gate
oxide was formed by a two-step thermal oxidation and wet etching
process, where a photoresist was used to mask the thick gate
oxide. The metal contamination caused by the photoresist was
completely removed after the wet etching process. It was found that
the wet etching significantly affected the gate oxide reliability
and that the reoxidation was useful for forming a reliable
oxide. The degradation of the thick gate oxide was due to an
increase in oxide surface microroughness and thinning at the edges
induced by a long wet etching time. The oxide reliability was
significantly enhanced by improving the surface roughness when the
oxide films were slightly etched during the wet etching process, and
resulted in a deep subquarter-micron complementary
metal-oxide-semiconductor (CMOS) transistor without thinning at the
edges.
Control of the Step Coverage Behavior of Gate a-SiNx:H
Authors: Chae Gee-Sung , Kim Kwang-Nam , Kitagawa Hitoshi , Oba Tomofumi
Published: October 2002

To overcome the trade-off in the properties of a-SiN
x
:H, which is a trade-off between the flat region of gate
metal and the step at its side, we have studied the key control factor for determining the step coverage behavior of
a-SiN
x
:H. To that end, a double rf-biased plasma-enhanced chemical vapor deposition (DRB-PECVD) system
which was developed with the aid of Professor Ohmi of Tohoku University, was very helpful. With the DRB-PECVD system, it is possible to control the flux of ions, which plays a major role in determining the film qualities
of a-SiN
x
:H. With vertical control of the homogeneity of a-SiN
x
:H, it was demonstrated that the step coverage
behavior of a-SiN
x
:H is determined by the intrinsic film stress which became more compressive (-) with increasing
effect of bombardment by ions extracted and accelerated by the substrate bias rf2 of the DRB-PECVD system.
a-SiN
x
:H film can be easily damaged by thermal quenching during the cooling process after the end of deposition
as the intrinsic film stress of a-SiN
x
:H becomes increasingly compressive (-). Although the damage can be
removed by increasing the thickness of a-SiN
x
:H film to greater than 200nm as a gate insulator for a thin film
transistor-liquid crystal display (TFT-LCD) panel, it is possible for
us to remove the thermal quenching damage on a-SiN
x
:H film even
when thickness is less than 200 nm.
Improvement in Antimony-Doped Ultrashallow Junction Sheet Resistance by Dopant Pileup Reduction at the SiO2/Si Interface
Authors: Shibahara Kentaro , Egusa Kazuhiko , Kamesaki Koji , Furumoto Hiroaki
Published: October 2002

Ultrashallow low-resistive junction formation has been investigated for
sub-100-nm metal oxide semiconductor field effect transistors (MOSFETs) using
low-energy Sb implantation and the rapid thermal annealing (RTA) technique. The Sb
pileup at the Si/SiO2 interface and the resulting dopant loss observed in the
furnace annealing cases was reduced by the RTA technique. As a result, the sheet
resistance of 19-nm-deep junctions was decreased to 0.84 kΩ/sq. By
increasing the implantation dose to 1×1014 cm-2, a junction depth of
24 nm and sheet resistance of 0.45 kΩ/sq. were obtained. In the case of As,
the pileup was not suppressed even with RTA. These results indicate that Sb is
superior to As as a dopant for ultrashallow extension formations.
A Novel High-Density and High-Speed NAND-Type Electrical Erasable Programmable Read Only Memory
Authors: Lin Frank Ruei-Ling , Lee Mao-Lin , Lin Shih-Yun , Boe Chen-Hao , Yeh Ching-Pen , Wu Po-Hao , Wang Wen-Sen , Ni James , Hsu Charles Ching-Hsiang
Published: October 2002

A new NAND-type electrical erasable programmable read only
memory (EEPROM), which employs (1) the novel in-cell temporary
storage (ICTS) technique and (2) the novel multiple-wordline
parallel programming (MWPP) method, is proposed to reduce the unit
cell size and decrease the overall programming time. The ICTS
approach latches input data directly to the selected EEPROM cells by
an inverted channel with different input bitline voltages. After all
the selected cells are latched to individual data, the MWPP method
simultaneously raises all selected wordlines to high voltage to
perform FN tunneling for parallel programming. The equivalent byte
programming time is considerably reduced by employing parallel
programming. The high-speed and high-density features further reduce
the EEPROM testing cost for manufacturers and save programming time
and cost for system providers.
Heavy-Metal (Fe/Ni/Cu) Behavior in Ultrathin Bonded Silicon-On-Insulator (SOI) Wafers Evaluated Using Radioactive Isotope Tracers
Authors: Furihata Jun-Ichiro , Nakano Masatake , Mitani Kiyoshi
Published: October 2002

The behavior of Fe, Ni and Cu in bonded silicon-on-insulator (SOI) wafers thinned
down to 0.5 µm by plasma-assisted chemical etching (PACE) was investigated for
the first time by the radioactive isotope tracer method, which can avoid the evaluation
errors due to contamination during sample preparation or analysis. When ultrathin
bonded SOI wafers without an intentional gettering site were contaminated with Fe or
Ni from the surface, Fe and Ni did not diffuse into the substrate through the buried
oxide (BOX) layer after annealing in N2(2%O2) ambient at 900°C and
700°C, respectively. Cu easily diffused into the substrate through the BOX layer
after annealing at 700°C for 60 min, and was captured at the bonding interface. It
was found that the behavior of Ni, which exhibits the same diffusivity in Si as does Cu,
was quite different in ultrathin bonded SOI wafers from that in bulk Si wafers due to
the BOX layer of the SOI structure.
Kink-Related Excess Noise in Deep Submicron Partially and Moderately Fully Depleted Unibond N-Metal Oxide Semiconductor Field Effect Transistor (MOSFET)
Authors: Haendler Sébastien , Jomaah Jalal , Balestra Francis , Pelloie Jean Luc. , Raynaud Christine
Published: October 2002

In this paper, the low-frequency excess noise due to the kink
effect in deep submicron unibond N-metal oxide semiconductor field
effect transistor (N-MOSFETs) is investigated. Drain current power
spectral density measurements are performed for partially and
moderately fully depleted and body-tied devices. The behavior of this
effect with the frequency is thoroughly analysed and the control of
such a noise overshoot by applying a back-gate voltage is also
demonstrated and discussed. A comparison between unibond and SIMOX
technologies, in terms of noise behavior, is presented. Finally, the
impact of the body contact on the noise is also shown.
Suppression of Stand-by Tunnel Current in Ultra-Thin Gate Oxide MOSFETs by Dual Oxide Thickness-Multiple Threshold Voltage CMOS (DOT-MTCMOS)
Authors: Inukai Takashi , Hiramoto Toshiro
Published: October 2002

A new circuit scheme, dual oxide thickness–multiple threshold voltage complementary metal oxide semiconductor (CMOS) (DOT-MTCMOS) which can suppress the stand-by tunnel leakage in
ultra-thin gate oxide metal semiconductor field effect transistors (MOSFETs) is proposed.
In this circuit, a power switch is inserted in series with CMOS circuits.
The power switch consists of a high V
th MOSFET
with relatively thick gate oxide, in order to suppress
not only subthreshold leakage but also tunneling leakage in the stand-by mode,
while the CMOS circuit consists of low V
th MOSFETs
with ultra-thin gate oxide for the high speed and low voltage
operation.
Using this circuit scheme, we can utilize the high drive current
of ultra-thin gate oxide MOSFETs in the future
where the scaling limit of the gate oxide thickness will not
be determined by the stand-by power.
An application of this scheme to a low voltage operation, hence
low power circuit, is also demonstrated.
Single-Electron Transistor and Current-Switching Device Fabricated by Vertical Pattern-Dependent Oxidation
Authors: Ono Yukinori , Takahashi Yasuo , Yamazaki Kenji , Nagase Masao , Namatsu Hideo , Kurihara Kenji , Murase Katsumi
Published: October 2002

Vertical pattern-dependent oxidation, a method of fabricating
single-electron transistors, has been advanced so that it can be
applied to make various types of single-electron logic circuits. The
improved method changes the pattern of Si to be oxidized from the
original. Using the improved method, we have demonstrated a
single-electron transistor with a new structure and a
current-switching device composed of the new single-electron
transistors.
Transmission Type RF Single Electron Transistor Operation of a Semiconductor Quantum Dot
Authors: Fujisawa Toshimasa , Hirayama Yoshiro
Published: October 2002

A single electron transistor is a highly sensitive electrometer, and can be
operated at a high speed using the radio-frequency single electron transistor
(RF-SET) technique. In this paper, we propose a modified RF-SET
technique, which measures the transmission of the RF signal. It has some
advantages, such as simpler circuits and clear frequency resonance as
compared with the reflection measurement by RF-SET. We have tested the
transmission-type RF-SET operation for a quantum dot in an AlGaAs/GaAs
heterostructure.
Progress in Quantum Dot Lasers: 1100 nm, 1300 nm, and High Power Applications
Authors: Grundmann Marius , Heinrichsdorff Frank , Ledentsov Nikolai N. , Ribbat Christian , Bimberg Dieter , Zhukov Alexei E. , Kovsh Alexei R. , Maximov Mikhail V. , Shernyakov Yuri M. , Lifshits Daniel A. , Ustinov Victor M. , Alferov Zhores I.
Published: October 2002

Quantum dot (QD) lasers have decisive advantages compared to
quantum well lasers. Zero-dimensional charge carrier localization
and reduction of charge carrier diffusion result in reduced
non-radiative surface recombination and thus possibly reduced facet
overheating and larger catastrophic optical damage (COD) threshold,
crucial for high power operation. The emission wavelengths of
1100 nm–1300 nm are easily realized using QDs on GaAs substrate,
not available with traditional quantum wells of the same material
system. We present results on metal-organic chemical vapor phase
deposition (MOCVD) and molecular beam epitaxy (MBE) grown high power
QD lasers (up to 4 W front facet cw) based on InGaAs QDs on GaAs
substrate
Ultrafast Coherent Control of Excitons Using Pulse-Shaping Technique
Authors: Komori Kazuhiro , Sugaya Takeyoshi , Watanabe Masanobu , Hidaka Takehiko
Published: October 2002

In this paper, we report on the ultrafast coherent control of excitons in quantum
wells using a phase-locked pulse sequence generated by pulse-shaping techniques. The
pulse-shaping system with a double liquid-crystal spatial light modulator (SLM), and a
Ti3+-sapphire laser is used to generate phase-locked pulses. The ultrafast
coherent control of the exciton population and polarization is demonstrated by the
observation of the reflectivity change in the pump-probe and the diffracted power in
the degenerate-four-wave-mixing (DFWM) measurements. In single quantum wells,
good coherent control characteristics with 87% coherent carrier destruction are
demonstrated at the low excitation power of 0.15 mW
(∼1.1×1010 photons/cm2). In addition, the preliminary
manipulation of the exciton population is demonstrated by the phase-locked triple
pulses. In the case of coupled quantum wells, the modulation of the SLM is carefully
controlled and the coherent control of both the exciton population and the polarization
is demonstrated in the two different coupled quantum-well samples.
Design for Waveguides in Three-Dimensional Photonic Crystals
Authors: Alongkarn Chutinan Alongkarn Chutinan , Susumu Noda Susumu Noda
Published: October 2002

We present a design for waveguides in three-dimensional photonic crystals. A single-mode three-dimensional photonic crystal waveguide can be created in the stacked-stripe structure by removing one stripe. A method for creating a waveguide bend is described. Numerical simulations show that a transmittance of more than 95% can be obtained over a wide range of frequencies. The results suggest that various types of optical circuits, such as a T-branch waveguide, can be created by removing or adding stripes in the stacked-stripe structure.
Band-Gap Energy and Effective Mass of BGaN
Authors: Honda Tohru , Shibata Masao , Kurimoto Makoto , Tsubamoto Mieko , Yamamoto Jun , Kawanishi Hideo
Published: October 2002

The band-gap energies and effective masses of boron gallium
nitride (BGaN) ternaries were estimated. The band-gap energies of
B
x
Ga1-x
N ternaries increase proportionally with the boron
composition x. However, the effective masses of electrons and holes
in BGaN ternaries are almost equal to those of GaN. We have
fabricated BGaN layers on 6H–SiC substrates using metal-organic
vapor phase epitaxy (MOVPE). We examined the photoluminescence
spectra of these layers. The band-gap energies and effective masses
estimated using the photoluminescence results are consistent with
those estimated theoretically.
Comparison of Various Parameterization Models for Optical Functions of Amorphous Materials: Application for Sputtered Titanium Dioxide Thin Films
Authors: Lee Soonil , Hong Junegie
Published: October 2002

We simultaneously determined the thickness, surface roughness,
index of refraction, and extinction coefficient of amorphous TiO2
films through the analysis of ellipsometric spectra using
parameterized optical functions. Moreover, we made a detailed
comparison among various parameterized optical functions and found
that the parameterization presented by Jellison and Modine [Appl.
Phys. Lett. 69 (1996) 371] was superior to others in
fitting the ellipsometric spectra in the wide photon-energy range that
encompasses both the transparent and the interband-transition
region. The more popular parameterization proposed by Forouhi and
Bloomer [Phys. Rev. B 34 (1986) 7018] failed to produce a
satisfactory fit to the measured spectra. However, the modification in
which the Sellmeier dispersion function was substituted for the
original parameterization of Forouhi and Bloomer in the transparent
region resulted in significantly improved fits.
Enhanced Hole Generation in Mg-Doped AlGaN/GaN Superlattices Due to Piezoelectric Field
Authors: Kumakura Kazuhide , Makimoto Toshiki , Kobayashi Naoki
Published: October 2002

We investigated the electrical properties of uniformly Mg-doped
AlGaN/GaN superlattices (SLs) with various Al mole fractions and SL
period thicknesses. We found that their sheet hole concentration
depended strongly on the Al mole fraction and SL period
thickness. We found the maximum spatial averaged hole concentrations
for SLs with period thicknesses of 360 Å and 100 Å to be
3×1018 cm-3 at room temperature. The resistivities
of the SLs were less temperature dependent than those of GaN and
AlGaN, indicating that the enhanced hole generation in these SLs
could be ascribed to the large energy shift of the valence band edge
due to the piezoelectric field.
n+-GaAs Back-Gated Double-Quantum-Well Structures with Full Density Control
Authors: Koji Muraki Koji Muraki , Norio Kumada Norio Kumada , Tadashi Saku Tadashi Saku , Yoshiro Hirayama Yoshiro Hirayama
Published: October 2002

We present the fabrication of a novel double-quantum-well (DQW) structure, in which the upper electron layer is supplied via modulation doping while the lower one is fully induced through the field effect from an n
+-GaAs back gate.
Low-temperature transport measurements demonstrate that two-dimensional electron gases with equally high mobilities are successfully formed in the lower as well as in the upper QWs.
By this approach, the electron density in the lower layer can be controlled over a wide range with a small back-gate bias, and hence the electron-density distribution in the DQW can be tuned arbitrarily by using a front gate in conjunction with the back gate.
Determination of the Facet Index in Area Selective Epitaxy of GaAs
Authors: Hiroaki Kuriyama Hiroaki Kuriyama , Masahiro Ito Masahiro Ito , Keita Suzuki Keita Suzuki , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

Area selective epitaxy of GaAs on GaAs substrates masked by SiO2 has been investigated using migration-enhanced epitaxy (MEE) with 2 s annealing after Ga deposition.
By this method, successful area selective epitaxy of GaAs has been achieved at substrate temperatures around 590°C.
We have carried out area selective epitaxy of GaAs on GaAs substrates of various surface indices.
Side facets are found to be composed of vertical {110} facets when epitaxial growth is carried out on GaAs (n11)A substrates, and composed of inclined {n20} facets when GaAs (n11)B substrates are used.
It is determined that the growth rates of A- and B-surfaces are the most important factors in the facet index determination.
A Monolithic Microwave-Integrated Circuit Doubler Using a Resonant-Tunneling High-Electron-Mobility Transistor
Authors: Kawashima Munenari , Hayashi Hitoshi , Fukuyama Hiroyuki , Okazaki Hiroshi , Matsuzaki Hideaki , Muraguchi Masahiro
Published: October 2002

A resonant-tunneling high-electron-mobility transistor (RTHEMT) doubler with matching circuits is described. We obtained a large conversion gain even at low input power, which was due to the strong nonlinearity of the RTHEMT. The conversion gain was 1.5 dB for a -10 dBm input signal at 2.4 GHz. Power consumption was only 4 mW, which was one-fifth that of a doubler using a GaAs metal-semiconductor field effect transistor (MESFET). The maximum reflection loss was 6 dB at 2.4 GHz.
Optical Investigation of Critical Thickness and Interface Fluctuation in CdSe/ZnSe Strained Layer Superlattices Grown on InP
Authors: Yoichi Nabetani Yoichi Nabetani , Isao Ishibe Isao Ishibe , Kazuki Sugiyama Kazuki Sugiyama , Takamasa Kato Takamasa Kato , Takashi Matsumoto Takashi Matsumoto
Published: October 2002

Optical measurements are performed for CdSen/ZnSen strained layer superlattices with n=2 to 10 ML grown on InP substrates to investigate the structural property. The electron-heavy-hole transition is observed from all strained layer superlattices and the electron-light-hole transition is observed from strained layer superlattices with n larger than 6 ML by photoreflectance spectroscopy. The comparison of transition energy measured by photoreflectance and calculation results based on the transfer matrix reveals that the critical thickness for strain relaxation of the CdSe/ZnSe strained layer superlattice on InP is 8 to 10 ML. The photoluminescence peak energy exhibits blue shift with increasing temperature in the region of 12 to 40 K for n=4, 6, and 8 ML, while reflectance spectra reveal a monotonic red shift. The blue shift in the low-temperature region indicates the carrier localization originating due to interface fluctuation.