Printed with permission of The Institute of Pure and Applied Physics (IPAP)

JAPANESE JOURNAL OF APPLIED PHYSICS [Part2]

Abstracts of Express Letters

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L617-L619
Part 2, No. 20, 10 May 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L620-L622
Part 2, No. 20, 10 May 2005
©2005 The Japan Society of Applied Physics

The Interface between Single Crystalline (001)
LaAlO3 and (001) SiliconSingle-Photon Generation in the 1.55-µm
Optical-Fiber Band from an InAs/InP
Quantum Dot

Dmitri O. Klenov*, Darrell G. Schlom1, Hao Li2 and Susanne Stemmer**(Received April 14, 2005; accepted April 15, 2005; published May 2, 2005)

Atomic resolution high-angle annular dark-field imaging in scanningtransmission electron microscopy is used to determine atomic arrangements at LaAlO3/Si interfaces, which were obtained by growing Si films
epitaxially on (001) LaAlO3 single crystals. An unusual 3 × 1 interface
reconstruction, in which every third La column is removed from the interface plane, is observed. The interface atomic structure is discussed in thecontext of electrically favorable interfacial bonding between the ionicoxide and Si. [DOI : 10.1143/JJAP.44.L617]
Keywords: high-angle annular dark-field imaging, high-k gate
dielectrics, oxide/semiconductor interfaces, scanningtransmission electron microscopy
Materials Department, University of California, Santa Barbara, CA 93106-5050, U.S.A.
1 Department of Materials Science and Engineering, Pennsylvania State University, University
Park, PA 16802-5005, U.S.A.
2 Microelectronics and Physical Sciences Laboratory, Motorola, 2100 E. Elliot Rd., Tempe, AZ
85284, U.S.A.
* E-mail address: d.o.klenov@physics.org** E-mail address: stemmer@mrl.ucsb.edu

Toshiyuki Miyazawa1,*, Kazuya Takemoto2, Yoshiki Sakuma3, Shinichi
Hirose2, Tatsuya Usuki2, Naoki Yokoyama2, Motomu Takatsu1 andYasuhiko Arakawa1,4,5(Received March 25, 2005; accepted April 16, 2005; published May 2, 2005)

We first succeeded in generating single-photon pulses in the C-band(1.55-µm band: the highest transmittance in optical telecommunication bands) from a single InAs/InP quantum dot. The quantum dot with
1546.1-nm exciton emission was prepared by controlling the growth
conditions. A well-designed mesa structure presented efficient injection of
the emitted photons into a single-mode optical fiber. A Hanbury-Brown
and Twiss measurement has proved that the photons through the fiber
were single photons. We also performed to transmit single-photon pulses
through 30-km optical fiber. This preliminary trial is a milestone toward
quantum telecommunication using ideal single photons.
[DOI : 10.1143/JJAP.44.L620]
Keywords: InAs/InP, single quantum dots, single-photon pulses,
C-band1 Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo
153-8505, Japan
2 Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0197, Japan
3 National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
4 Nanoelectronics Collaborative Research Center, The University of Tokyo, 4-6-1 Komaba,
Meguro-ku, Tokyo 153-8505, Japan
5 Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1
Komaba, Meguro-ku, Tokyo 153-8505, Japan* E-mail address: miyatosi@iis.u-tokyo.ac.jp

20

JSAP International No.13 (January 2006)

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L646-L648
Part 2, No. 21, 10 May 2005
©2005 The Japan Society of Applied Physics

DC and RF Characteristics in Al2O3/Si3N4
Insulated-Gate AlGaN/GaN Heterostructure
Field-Effect Transistors
Narihiko Maeda*, Takashi Makimura, Takashi Maruyama1, Chengxin
Wang, Masanobu Hiroki, Haruki Yokoyama, Toshiki Makimoto2, Takashi
Kobayashi and Takatomo Enoki(Received April 19, 2005; accepted April 24, 2005; published May 11, 2005)

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L643-L645
Part 2, No. 21, 10 May 2005
©2005 The Japan Society of Applied Physics

Blue Light-Emitting Diode Based on ZnOAtsushi Tsukazaki1, Masashi Kubota2, Akira Ohtomo1,
Takeyoshi Onuma2,3, Keita Ohtani4, Hideo Ohno4,
Shigefusa F. Chichibu2,3 and Masashi Kawasaki1*,**(Received April 19, 2005; accepted April 21, 2005; published May 11, 2005)

A near-band-edge bluish electroluminescence (EL) band centered ataround 440 nm was observed from ZnO p −i −n homojunction diodes
through a semi-transparent electrode deposited on the p -type ZnO top
layer. The EL peak energy coincided with the photoluminescence peakenergy of an equivalent p -type ZnO layer, indicating that the electron
injection from the n -type layer to the p -type layer dominates the current,
giving rise to the radiative recombination in the p -type layer. The imbalance in charge injection is considered to originate from the lower majority
carrier concentration in the p -type layer, which is one or two orders ofmagnitude lower than that in the n -type one. The current-voltage characteristics showed the presence of series resistance of several hundreds
ohms, corresponding to the current spread resistance within the bottom
n -type ZnO. The employment of conducting ZnO substrates may solve thelatter problem. [DOI : 10.1143/JJAP.44.L643]
Keywords: ZnO, light-emitting diode, thin film, pulsed laser deposition, self-absorption
1 Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
2 Institute of Applied Physics and Graduate School of Pure and Applied Sciences, University ofTsukuba, Tsukuba, Ibaraki 305-8573, Japan
3 NICP, ERATO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
4 Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan* Also at Combinatorial Material Science and Technology (COMET), Tsukuba, Ibaraki 305-0044,
Japan.
** E-mail address: kawasaki@imr.tohoku.ac.jp

Al2O3/Si3N4 insulated-gate AlGaN/GaN heterostructure field-effecttransistors (HFETs) have been fabricated, where excellent RF characteristics have been obtained in addition to the low gate leakage current as theresult of employing the metal−insulator−semiconductor (MIS) structure.
In an HFET with a gate length (L g) of 0.1 µm, the cutoff frequency (f T)
and maximum oscillation frequency (f max) were estimated to be 70 and 90
GHz, respectively. The drain current density (I d) and transconductance (g m)were 1.30 A/mm and 293 mS/mm, respectively. The gate leakage current(I g) was as low as 4 × 10-5 A/mm even at a forward bias voltage of +3 V.
[DOI : 10.1143/JJAP.44.L646]
Keywords: AlGaN, GaN, HFET, Al2O3, Si3N4, insulated-gate, metalinsulator-semiconductor (MIS), gate leakage current,
cutoff frequency (fT), maximum oscillation frequency(fmax)NTT Photonics Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa
243-0198, Japan
1 NTT Advanced Technology Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa
243-0198, Japan
2 NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi,
Kanagawa 243-0198, Japan* E-mail address: narihiko@aecl.ntt.co.jp

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L649-L651
Part 2, No. 21, 10 May 2005
©2005 The Japan Society of Applied Physics

Strongly Enhanced Phosphor Efficiency in
GaInN White Light-Emitting Diodes Using
Remote Phosphor Configuration and Diffuse
Reflector Cup
Jong Kyu Kim1, Hong Luo2, Eric Fred Schubert1,2*, Jaehee Cho3,
Cheolsoo Sone3 and Yongjo Park3(Received April 1, 2005; accepted April 21, 2005; published May 11, 2005)

Enhancement of phosphor efficiency is reported for GaInN-based
white light-emitting diodes (LEDs) employing a large separation between
the primary LED emitter and the wavelength converter, and a diffuse
reflector cup. Ray-tracing simulations show that extraction efficiencyof wavelength-converted light is enhanced by 75%. The experimental
improvement in phosphor efficiency of blue-pumped yellow phosphor
is 15.4% compared with conventional phosphor-based white LEDs. The
improvement is attributed to reduced re-absorption of wavelengthconverted light by the LED chip. [DOI : 10.1143/JJAP.44.L649]
Keywords: light-emitting diodes, GaN, diffuse reflector, encapsulant,
phosphor
1 Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, U.S.A.
2 Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy,
NY 12180, U.S.A.
3 Photonics Program Team, Samsung Advanced Institute of Technology, Suwon 440-600, Korea* E-mail address: EFSchubert@rpi.edu

JSAP International No.13 (January 2006)21

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L652-L654
Part 2, No. 21, 10 May 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L683-L686
Part 2, No. 22, 10 May 2005
©2005 The Japan Society of Applied Physics

Tunable Sub-Terahertz Wave Generation froman Organic DAST Crystal

Incubation-Free Growth of Polycrystalline Si
Films by Plasma-Enhanced Chemical Vapor
Deposition Using Pulsed Discharge under Near
Atmospheric Pressure

Tetsuo Taniuchi*, Satoshi Ikeda, Shuji Okada1 and Hachiro Nakanishi(Received March 29, 2005; accepted April 22, 2005; published May 11, 2005)

Tunable sub-terahertz (THz) waves ranging from 0.3 to 3 THz weregenerated in a 4’-N ,N -dimethylamino-N ’-methyl-4-stilbazolium tosylate(DAST) crystal using the difference frequency mixing technique. We developed a dual-wavelength optical parametric oscillator near 990 nm with
two KTiOPO4 crystals as the input light source. The maximum output
energy of 17 nJ/pulse (peak power: 1.4 W) was achieved at 0.7 THz using
a high-quality DAST crystal with a 2-mm thickness.
[DOI : 10.1143/JJAP.44.L652]
Keywords: nonlinear optics, terahertz generation, optical parametricoscillator, difference frequency generation, organic
crystalInstitute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira,Aoba-ku, Sendai 980-8577, Japan
1 Faculty of Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510,
Japan* E-mail address: taniuchi@tagen.tohoku.ac.jp

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L679-L682
Part 2, No. 22, 10 May 2005
©2005 The Japan Society of Applied Physics

Progress in the Efficiency of Wide-Gap
Cu(In1-xGax)Se2 Solar Cells Using CIGSe Layers
Grown in Water Vapor
Shogo Ishizuka*, Keiichiro Sakurai, Akimasa Yamada, Hajime Shibata,Koji Matsubara, Minoru Yonemura1, Satoshi Nakamura1,
Hisayuki Nakanishi1, Takeshi Kojima and Shigeru Niki
(Received April 25, 2005; accepted May 5, 2005; published May 23, 2005)

Progress in the performance of wide-gap Cu(In1-x Gax )Se2 (CIGSe) solar
cells for x values around 0.5 has been demonstrated using CIGSe layersgrown in the presence of water vapor. While CIGSe thin films depositedin the presence of water vapor showed variations in electrical properties
such as increases in hole carrier density and a consequent enhancement ofp -type conductivity, no significant changes in the morphology and growthorientation were observed. Both the open circuit voltages and current
densities of the CIGSe solar cells were improved using CIGSe layers grownin water vapor. An 18.1%-efficient cell with an open circuit voltage of
0.744 V, a current density of 32.4 mA/cm2 and a fill factor of 0.752 was
fabricated from a 1.3 eV-CIGSe (x ~ 0.48) layer.
[DOI : 10.1143/JJAP.44.L679]
Keywords: Cu(In,Ga)Se2, thin-film solar cells, MBE, wide-gap, water
vapor
National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono,
Tsukuba, Ibaraki 305-8568, Japan
1 Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan* Corresponding author. E-mail address: shogo-ishizuka@aist.go.jp

22

JSAP International No.13 (January 2006)

Hirotatsu Kitabatake1, Maki Suemitsu1, Hiroya Kitahata2,
Setsuo Nakajima2, Tsuyoshi Uehara2 and Yasutake Toyoshima1,3(Received April 26, 2005; accepted May 1, 2005; published May 23, 2005)

By using the plasma-enhanced chemical vapor deposition (PE-CVD)
under near-atmospheric pressures, we have achieved a high rate growth,
1 nm/s, of polycrystalline Si films on glass substrates without incubation
layers for the first time. We have employed a short-pulse based system fora stable operation of discharge at atmospheric pressures without inert gas
dilution. This feature enabled us to employ an extremely high dilution ofmonosilane by hydrogen, which should be the origin of the incubationfree growth of our films, in addition to the basic advantage for the highrate growth inherent in atmospheric reaction systems. The films are mainly
consisted of polycrystalline Si with grain size ranging from 5 nm to above
10 nm, as observed by Raman scattering, X-ray diffractions and crosssectional transmission electron microscopy. [DOI : 10.1143/JJAP.44.L683]
Keywords: plasma-enhanced chemical vapor deposition (PE-CVD),
atmospheric pressure, pulsed discharge, polycrystalline Si,
Raman scattering, X-ray diffraction (XRD), cross-sectionaltransmission electron microscopy (X-TEM), incubation layer
1 Center for Interdisciplinary Research, Tohoku University, Sendai 980-8578, Japan
2 Sekisui Chemicals Co., Ltd., Wadai, Tsukuba, Ibaraki 300-4292, Japan
3 Energy Technology Research Institute, National Institute of Advanced Industrial Science andTechnology, Tsukuba, Ibaraki 305-8568, Japan

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L687-L689
Part 2, No. 22, 10 May 2005
©2005 The Japan Society of Applied Physics

Welding of Transparent Materials Using
Femtosecond Laser Pulses
Takayuki Tamaki*, Wataru Watanabe, Junji Nishii1 and Kazuyoshi Itoh
(Received February 22, 2005; accepted April 14, 2005; published May 23, 2005)

We report on laser welding between transparent materials without
the insertion of intermediate layers such as glue by use of near-infrared
femtosecond laser pulses. When femtosecond laser pulses are focused at
the interface of transparent materials, the material around the focal pointis melted and resolidified because of the temperature increases due to the
localized nonlinear absorption of optical pulse energy. We experimentally
succeeded in laser welding between two pieces of silica glass without theinsertion of an intermediate layer by femtosecond laser pulses. This technique has a possible application to the joining of semiconductors such as
silicon crystals. [DOI : 10.1143/JJAP.44.L687]
Keywords: laser welding, femtosecond laser, filament, fluorescence,
silica glass, space selective
Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1
Yamadaoka, Suita, Osaka 565-0871, Japan
1 Photonics Research Institute, Kansai Center, National Institute of Advanced Industrial Scienceand Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan* E-mail address: tamaki@photonics.mls.eng.osaka-u.ac.jp

Abstracts of Express Letters

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L690-L692
Part 2, No. 22, 10 May 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L720-L722
Part 2, No. 23, 10 May 2005
©2005 The Japan Society of Applied Physics

Synthesis of Pt-Entrapped Titanate Nanotubes

Current-Induced Plastic Deformation of
Double-Walled Carbon Nanotubes

Atsushi Nakahira, Takashi Kubo, Yuki Yamasaki1, Toshiyuki Suzuki2 andYuichi Ikuhara3(Received April 21, 2005; accepted May 1, 2005; published May 23, 2005)

In this study, Pt-entrapped titanate nanotubes with approximately
10 to 15 nm in outer diameter and 5 nm in inner diameter and several
hundreds in length were synthesized by a hydrothermal treatment oftitanium oxide as a source material and a subsequent heat-treatment of
the mixture of these titanate nanotube and a Pt salt. According to TEM
observations, Pt nanocrystals with a few nm in diameter and 5 to 10 nm
in length were contained in titanate nanotubes. These Pt nanocrystalentrapped titanate nanotubes had the high photocatalytic properties,
which are also expected to be a useful material for nanotechnology applications. [DOI : 10.1143/JJAP.44.L690]
Keywords: nanotube, Pt, nanocrystal, titanate, HTiO
Department of Materials Science, Osaka Prefecture University, 1-1 Gakuencho, Sakai, Osaka
599-8531, Japan
1 Department of Industrial Chemistry, Osaka Prefectural College of Technology, Saiwai-cho,
Neyagawa, Osaka 572-8572, Japan
2 JFCC, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587, Japan
3 The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L693-L695
Part 2, No. 22, 10 May 2005
©2005 The Japan Society of Applied Physics

High-Rate Growth of Films of Dense, Aligned
Double-Walled Carbon Nanotubes Using
Microwave Plasma-Enhanced Chemical Vapor
Deposition
Mineo Hiramatsu, Hidetoshi Nagao1, Masaki Taniguchi1, Hiroshi Amano1,
Yoshinori Ando1 and Masaru Hori2(Received April 18, 2005; accepted April 27, 2005; published May 23, 2005)

Carbon nanotube (CNT) films were grown using microwave plasmaenhanced chemical vapor deposition. Catalytic cobalt (Co) nanoparticles
were deposited on a silicon substrate using pulsed arc deposition. A titanium nitride (TiN) thin film was used as a buffer layer on the substrate inorder to prevent the formation of Co silicide. A dense, vertically aligned,
double-walled CNT (DWNT) film was grown rapidly on the Co-catalyzed
Si substrate. The CNTs grew at an extremely high rate of 600 nm/s during
the first 10 min of growth. Dense DWNT films with thicknesses of over
500 µm were obtained in 20 min. [DOI : 10.1143/JJAP.44.L693]
Keywords: carbon naotube, double-walled CNT, plasma enhanced
CVD, Co catalyst, aligned, high growth rate
Nano Factory, Department of Electrical and Electronic Engineering, Meijo University, Tempaku,
Nagoya 468-8502, Japan
1 Nano Factory, Department of Materials Science and Engineering, Meijo University, Tempaku,
Nagoya 468-8502, Japan
2 Department of Electrical Engineering and Computer Science, Nagoya University, Chikusa,
Nagoya 464-8603, Japan

Yoshikazu Nakayama1,2*, Atsuko Nagataki2, Osamu Suekane2,
Xiaoyu Cai1 and Seiji Akita1(Received April 26, 2005; accepted May 13, 2005; published May 27, 2005)

We induced a permanent plastic deformation in an originally straightdouble-walled nanotube by applying current to an individual nanotube
that had been bent elastically under mechanical duress. This method iscontrollable and allows nanotubes’ application as building blocks in nanostructures. Inserting pentagon−heptagon pairs into a nanotube createdbending angles of 20−30º. The onset of plastic deformation, as measured
using the current circumference-density, is less than 1/20 that of the sublimation. The onset decreases with increasing nanotube diameter. This
process is performed using a transmission electron microscope: electron
beam energy is not essential for the process but decreases the onset.
[DOI : 10.1143/JJAP.44.L720]
Keywords: carbon nanotubes, double-walled carbon nanotubes,
plastic deformation, permanent bend, transmission
electron microscope, nanomanipulation
1 Department of Physics and Electronics, Graduate School of Engineering, Osaka Prefecture
University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan
2 Handai Frontier Research Center, Graduate School of Engineering, Osaka University, 2-1
Yamadaoka, Suita, Osaka 565-0871, Japan* E-mail address: nakayama@pe.osakafu-u.ac.jp

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L793-L796
Part 2, No. 25, 10 June 2005
©2005 The Japan Society of Applied Physics

Photon Antibunching Observed from an
InAlAs Single Quantum Dot
Satoshi Kimura1, Hidekazu Kumano1, Michiaki Endo1, Ikuo Suemune1,3,
Tomonori Yokoi2, Hirotaka Sasakura3, Satoru Adachi2,3, Shunichi Muto2,3,
Hai Zhi Song3,4, Shinichi Hirose5 and Tatsuya Usuki3,4(Received May 12, 2005; accepted May 22, 2005; published June 10, 2005)

Single-photon emitters and detectors are key devices to realize securecommunications with single-photon-based quantum cryptography andsingle-photon-based quantum computing. InAlAs quantum dots (QDs)
cover the wavelength range with high quantum efficiencies of Si-based
single-photon detectors. Clear photon antibunching was observed froman InAlAs single QD under weak excitations. To realize single-photon emitters on demand, complete population of the QD energy states before
the photon emission events is necessary, but the measured antibunchingproperties were dependent substantially on the photo-excitation powers.
The physical origin of this problem is discussed. The criterion to distinguishthe real deviation from the photon antibunching condition and the artifactof the measurements is clarified. The capability of single-photon emissions
on demand will be demonstrated with photon antibunching under pulsed
operations. [DOI : 10.1143/JJAP.44.L793]
Keywords: photon antibunching, quantum dot, photon correlation
measurement, single photon emission, InAlAs
1 RIES, Hokkaido University, Sapporo 001-0021, Japan
2 Department of Applied Physics, Hokkaido Univercity, Sapporo 060-8628, Japan
3 CREST JST, Kawaguchi, Saitama 332-0012, Japan
4 Fujitsu Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0197, Japan
5 Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0197, Japan

JSAP International No.13 (January 2006)

23

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L797-L799
Part 2, No. 25, 10 June 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L803-L805
Part 2, No. 25, 10 June 2005
©2005 The Japan Society of Applied Physics

Structural Characterization of Thick GaN
Films Grown on Free-Standing GaN Seeds
by the Ammonothermal Method Using Basic
Ammonia

Nucleation Stages of Carbon Nanotubes on
SiC(0001) by Surface Decomposition

Tadao Hashimoto*, Kenji Fujito, Feng Wu, Benjamin A. Haskell,
Paul T. Fini, James S. Speck and Shuji Nakamura(Received April 30, 2005; accepted May 24, 2005; published June 10, 2005)

Single crystalline GaN was grown on c -plane free-standing GaN seeds
via fluid transport by the ammonothermal method. Ammonothermal
growth was carried out in an ammonobasic solution with a metallic Ga
nutrient placed in a lower-temperature zone. The thickest film obtained so
far is ~45 µm, which was grown on the N-face of the seed. The growthinterface contained numerous voids and defects, whereas the microstructure close to the surface was greatly improved. The major defects close to
the surface were mixed-character threading dislocations. The estimatedthreading dislocation density was low-109 cm-2 level at the free surface of
the N-face. [DOI : 10.1143/JJAP.44.L797]
Keywords: bulk GaN, ammonothermal growth, dislocations, seeded
growth, supercritical ammonia

Kenjiro Hayashi, Seigi Mizuno, Satoru Tanaka1, Hiroki Toyoda1,
Hiroshi Tochihara and Ikuo Suemune1(Received April 20, 2005; accepted May 22, 2005; published June 10, 2005)

Nucleation stages of carbon nanotubes (CNTs) on a SiC(0001) Si-face(4º off toward [11\bar20]) by surface decomposition are investigated bymeans of in-situ scanning tunneling microscopy (STM). After a relatively
short heating time at 1600ºC, moiré patterns and small nuclei appear
on the surface due to the evaporation of Si atoms and, as a result of
this, surface graphitization. Modelling of the moiré pattern indicates theformation of a single graphene sheet on top of the SiC surface. Local
swelling (~1 nm in diameter) of such a graphene sheet, possibly resulting
from the compressive stress at the graphene/SiC interface, gives rise toa CNT nucleus. In the stages that follow, the nucleus is continuously andunidirectionally prolonged and rolled-up, which may result in a final form
such as a CNT. [DOI : 10.1143/JJAP.44.L803]
Keywords: carbon nanotube, silicon carbide, scanning tunnelingmicroscopy, moiré pattern, surface decomposition

Materials Department and ERATO/JST UCSB Group, University of California, Santa Barbara, CA
93106-5050, U.S.A.
* E-mail address: tadao@engineering.ucsb.edu

Department of Molecular and Material Sciences, Kyushu University, Fukuoka 816-8580, Japan
1 Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0021, Japan

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L800-L802
Part 2, No. 25, 10 June 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L860-L862
Part 2, No. 27, 10 June 2005
©2005 The Japan Society of Applied Physics

Self-Aligned-Gate Metal/Ferroelectric/
Insulator/Semiconductor Field-EffectTransistors with Long Memory Retention

Fabrication of DNA Nanofibers on a Planar
Surface by Electrospinning

Mitsue Takahashi* and Shigeki Sakai**(Received May 25, 2005; accepted May 27, 2005; published June 10, 2005)

Self-aligned-gate Pt/SrBi2Ta2O9/HfAlO/Si metal/ferroelectric/insulator/
semiconductor (MFIS) field-effect transistors (FETs) were fabricated.
Drain current (I d) versus gate voltage curves of the MFIS FETs showedalmost the same steepness as that of a non-self-aligned-gate Pt/HfAlO/Si
metal/insulator/semiconductor FET. Long retention times with large onand off-state I d ratios were obtained for the MFIS FETs. The retention
times more than 33 days with an on- and off-state I d ratio over 105 were
demonstrated for the self-aligned-gate MFIS FET with a 2-µm-long and80-µm-wide gate. This device showed the longest memory retention
among all of the ferroelectric-gate FETs reported ever before.
[DOI : 10.1143/JJAP.44.L800]
Keywords: metal/ferroelectric/insulator/semiconductor (MFIS),
nonvolatile memory, retention, ferroelectric, SBT, HfAlO,
1T FeRAM
National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1 Umezono,
Tsukuba, Ibaraki 305-8568, Japan* E-mail address: mitsue-takahashi@aist.go.jp** E-mail address: shigeki.sakai@aist.go.jp

24

JSAP International No.13 (January 2006)

Takuya Takahashi, Masateru Taniguchi* and Tomoji Kawai(Received April 20, 2005; accepted June 10, 2005; published June 24, 2005)

The electrospinning method was employed for preparing DNA nanofibers on a mica substrate using a high electrostatic field. The DNA nanofibers were examined using atomic force microscopy. It was found thatthe amount, shape, average height and average length of the nanofibers depended on the experimental conditions. By controlling the applied
voltage and the concentration of DNA, we obtained stretched DNA nanofibers at 20 kV and 1.5 wt % with an average height and length of 1.8
nm and 1 µm, respectively. [DOI : 10.1143/JJAP.44.L860]
Keywords: DNA nanofibers, electrospinning
Nanoscience and Nanotechnology Center, The Institute of Scientific and Industrial Research,
Osaka University, Osaka 567-0047, Japan* Corresponding author.

Abstracts of Express Letters

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L893-L895
Part 2, No. 28, 10 July 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L920-L922
Part 2, No. 29, 10 July 2005
©2005 The Japan Society of Applied Physics

Strongly Enhanced Sensitivity of Piezoresistive
Cantilevers by Utilizing the Superconducting
Proximity EffectCharacterization of Planar Semipolar Gallium
Nitride Films on Spinel Substrates

1

Hajime Okamoto*, Tatsushi Akazaki, Mineo Ueki andHiroshi Yamaguchi(Received May 18, 2005; accepted June 17, 2005; published July 1, 2005)

We fabricated a novel piezoresistive cantilever that integrates a superconductor−semiconductor−superconductor (S−Sm−S) junction. The cantilever was processed from an InAs/AlGaSb heterostructure and a submicron-size niobium gap was patterned to form a Nb−InAs−Nb junction,
at which the deflection of the cantilever can be detected as resistancechange, i.e., piezoresistance. The resulting piezoresistance at ~2 K strongly
depends on the bias current, and we confirmed that the piezoresistance isenhanced by two orders of magnitude at the critical current, where transition between superconducting state and normal state occurs in the S−Sm
−S junction. This indicates that S−Sm−S junctions can be applied for highly
sensitive displacement and force sensors. [DOI : 10.1143/JJAP.44.L893]
Keywords: cantilever, MEMS, semiconductor, heterostructure,
piezoresistance, superconductor

Troy J. Baker1,3*, Benjamin A. Haskell1,3, Feng Wu1,3, Paul T. Fini1,3,
James S. Speck1,3 and Shuji Nakamura1,2,3(Received June 17, 2005; accepted June 23, 2005; published July 8, 2005)

Specular, planar semipolar gallium nitride films were grown by hydride
vapor phase epitaxy. This is the first report of high quality semipolar GaN
films that could be used for device growth. Planar films of (10-1-1)GaN
have been grown on (100)MgAl2O4 spinel, and planar films of (10-1-3)GaN
have been grown on (110)MgAl2O4 spinel. The in-plane epitaxial relationship for (10-1-1)GaN on (100) spinel was [10-1-2]GaN // [011]spinel and[1-210]GaN // [0-11]spinel. The in-plane epitaxial relationship for (10-1-3)GaN
on (110) spinel was [30-3-2]GaN // [001]spinel and [1-210]GaN // [-110]spinel.
[DOI : 10.1143/JJAP.44.L920]
Keywords: semipolar, GaN, (10-11), (10-1-1), (10-13), (10-1-3)
1 Materials Department, University of California, Santa Barbara, CA 93106, U.S.A.
2 Electrical Engineering Department, University of California, Santa Barbara, CA 93106, U.S.A.
3 NICP/ERATO JST, UCSB Group, University of California, Santa Barbara, CA 93106, U.S.A.
* E-mail address: tjb@engr.ucsb.edu

NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198, Japan
1 NTT Electronics Techno Corporation, Atsugi, Kanagawa 221-0052, Japan* E-mail address: hajime@nttbrl.jp

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L896-L898
Part 2, No. 28, 10 July 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L945-L947
Part 2, No. 30, 10 July 2005
©2005 The Japan Society of Applied Physics

A Ferromagnetic Oxide Semiconductor as
Spin Injection Electrode in Magnetic Tunnel
Junction

Milliwatt Power Blue InGaN/GaN
Light-Emitting Diodes on Semipolar GaN
Templates

Hidemi Toyosaki, Tomoteru Fukumura*, Kazunori Ueno, Masaki Nakano
and Masashi Kawasaki**Arpan Chakraborty, Troy J. Baker*, Benjamin A. Haskell*, Feng Wu*,
James S. Speck*, Steven P. Denbaars*, Shuji Nakamura* andUmesh K. Mishra**(Received June 6, 2005; accepted June 17, 2005; published July 1, 2005)(Received June 16, 2005; accepted June 27, 2005; published July 15, 2005)

A magnetic tunnel junctions composed of room temperature ferromagnetic semiconductor rutile Ti1-x Cox O2-δ and ferromagnetic metal
Fe0.1Co0.9 separated by AlOx barrier showed positive tunneling magnetoresistance (TMR) with a ratio of ~11% at 15 K, indicating that Ti1-x Cox O2-δcan be used as a spin injection electrode. The TMR decreased withincreasing temperature and vanished above 180 K. TMR action at hightemperature is likely prohibited by the inelastic tunneling conduction due
to the low quality of the amorphous barrier layer and/or the junction
interface. [DOI : 10.1143/JJAP.44.L896]
Keywords: tunneling magnetoresistance, ferromagnetic semiconductor, Co-doped TiO2, magnetic tunnel junction, wide
gap semiconductor, oxide semiconductor
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan* E-mail address: fukumura@imr.tohoku.ac.jp** Also at Combinatorial Materials Exploration and Technology (COMET), National Institute forMaterials Science, Tsukuba, Ibaraki 305-0044 Japan.

Growth of semipolar Group-III nitrides based devices offers a meansof reducing the deleterious effects of the polarization-induced electricfields present in the polar quantum wells. We report on the fabricationof blue InGaN/GaN multiple-quantum well light-emitting diodes (LEDs)
on semipolar (10-1-1) and (10-1-3) oriented GaN templates. A maximum
on-wafer continuous wave output power of 190 µW was measured at 20
mA for 300 × 300 µm2 devices, and output power as high as 1.53 mW
was measured at 250 mA. Drive-current independent electroluminescencepeak at 439 nm was observed for the LEDs grown on both the planes. The
current−voltage characteristics of these LEDs showed rectifying behavior
with a forward voltage of 3−4 V at 20 mA. [DOI : 10.1143/JJAP.44.L945]
Keywords: semipolar, InGaN, multiple-quantum well (MQW), lightemitting diode (LED), electroluminescence (EL)Electrical and Computer Engineering and Materials Departments, University of California, Santa
Barbara, CA 93106, U.S.A.
* Also at ERATO JST, UCSB Group, University of California, Santa Barbara, CA 93106, U.S.A.
** E-mail address: mishra@ece.ucsb.edu

JSAP International No.13 (January 2006)25

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L948-L951
Part 2, No. 30, 10 July 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L976-L978
Part 2, No. 31, 10 July 2005
©2005 The Japan Society of Applied Physics

High Curie Temperature and Nano-Scale
Spinodal Decomposition Phase in Dilute
Magnetic Semiconductors

Highly Tunable Emission from Strain-Induced
InGaAsP/InP Quantum Dots

Kazunori Sato*, Hiroshi Katayama-Yoshida and Peter H. Dederichs1(Received June 6, 2005; accepted June 25, 2005; published July 15, 2005)

We show that spinoadal decomposition phase in dilute magnetic
semiconductors (DMS) offers the possibility to have high Curie temperatures (T C) even if the magnetic exchange interaction is short ranged. The
spinodal decomposition is simulated by applying the Monte Carlo method
to the Ising model with realistic (ab initio ) chemical pair interactions
between magnetic impurities in DMS. Curie temperatures are estimatedby the random phase approximation with taking disorder into account.
It is found that the spinodal decomposition phase inherently occurs in
DMS due to strong attractive interactions between impurities. This phasedecomposition supports magnetic network over the dimension of thecrystal resulting in a high-T C phase. [DOI : 10.1143/JJAP.44.L948]
Keywords: dilute magnetic semiconductor, spinodal decomposition
phase, concentration fluctuation, chemical pair interaction, percolation, Curie temperature
The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki,
Osaka 567-0047, Japan
1 Institut für Ferskoerperforschung, Forschungszentrum Juelich, D-52425 Juelich, Germany* E-mail address: ksato@cmp.sanken.osaka-u.ac.jp

Juha Riikonen*, Jaakko Sormunen, Hannu Koskenvaara, Marco Mattila,
Markku Sopanen and Harri Lipsanen(Received June 23, 2005; accepted July 6, 2005; published July 22, 2005)

Low-temperature photoluminescence (PL), tunable between 1.3
and 1.7 µm, is obtained from strain-induced quantum dots (SIQDs). The
quantum dots are fabricated by growing self-assembled InAs stressor
islands on top of a near-surface InGaAs(P)/InP quantum well (QW). The
structure is tuned by varying the composition of the QW and its distancefrom the surface. Time-resolved PL measurements reveal that QD relaxation and recombination time constants (0.55 and 0.50 ns) are virtuallyindependent of the composition of the nearly lattice-matched InGaAsP
layer. Also, decreasing the QW distance from the surface is shown to shift
the energy states and significantly diminish the PL intensity of the SIQD.
[DOI : 10.1143/JJAP.44.L976]
Keywords: stressors, InAs islands, self-assembled growth, quantum
dot, photoluminescence
Optoelectronics Laboratory, Helsinki University of Technology, P. O. Box 3500, FIN-02015 TKK,
Finland* E-mail address: juha.riikonen@tkk.fi

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L952-L954
Part 2, No. 30, 10 July 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L979-L981
Part 2, No. 31, 10 July 2005
©2005 The Japan Society of Applied Physics

Critical Current Density Enhancement arounda Matching Field in ErBa2Cu3O7-δ Films with
BaZrO3 Nano-Rods

Magnetic Behavior of Fe Doped In2O3

Masashi Mukaida1,8*, Tomoya Horide2,8, Ryusuke Kita3,8, Shigeru Horii4,8,Ataru Ichinose5,8, Yutaka Yoshida6,8, Osuke Miura7,8,
Kaname Matsumoto2,8, Kazuhiro Yamada1 and Nobuyuki Mori1(Received June 3, 2005; accepted June 25, 2005; published July 15, 2005)

Field angular dependences of critical current density are measured
for as-grown high crystalline quality ErBa2Cu3O7-δ films with BaZrO3nano-rods. Large critical current density enhancement is observed. The
magnetic field where the enhancement is observed coincides with thematching field calculated from the density of BaZrO3 nano-rods. The
largest enhancement is observed in B // c -axis of ErBa2Cu3O7-δ films. Thisanisotropic critical current density enhancement is thought to be causedby the direction of BaZrO3 nano-rods which grow along the c -axis of thefilms. BaZrO3 nano-rods in the films will promise the application of coatedconductors in a magnetic field. [DOI : 10.1143/JJAP.44.L952]
Keywords: ErBa2Cu3O7-δ , BaZrO3 nano-rods, Field angular dependence, pinning center
1 Kyushu University, Hakozaki, Fukuoka, Fukuoka 812-8581, Japan
2 Kyoto University, Yoshidahonmachi, Sakyo-ku, Kyoto 606-8501, Japan
3 Shizuoka University, Johoku, Hamamatsu, Shizuoka 430-8501, Japan
4 University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
5 Central Research Institute of Electric Power Industry, Yokosuka, Kanagawa 240-0196, Japan
6 Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
7 Tokyo Metropolitan University, Minamiosawa, Hachioji, Tokyo 192-0397, Japan
8 Japan Science and Technology Agency, Honmachi, Kawaguchi, Saitama 332-0012, Japan* E-mail address: mukaida@zaiko.kyushu-u.ac.jp

26

JSAP International No.13 (January 2006)

Shigemi Kohiki, Yusuke Murakawa, Kyoko Hori, Hirokazu Shimooka,
Takayuki Tajiri1, Hiroyuki Deguchi1, Masaoki Oku2, Masao Arai3,
Masanori Mitome3 and Yoshio Bando3(Received June 12, 2005; accepted July 4, 2005; published July 22, 2005)

We report spin-glass transition at room temperature (RT) and clusterglass behavior below RT for Fe doped In2O3 powders with the atomic ratioof In : Fe = 1.85 : 0.15 grown in an oxygen atmosphere. In ac susceptibility, a large peak and a small cusp were observed at RT and \approx30
K, respectively. The peak at RT shifted to higher temperatures with anincrease of applied field frequency, while the cusp showed no frequency
dependence. Third harmonic nonlinear susceptibility exhibited a divergent
peak at RT. Field-cooled dc susceptibility increased almost linearly below
RT, whereas zero-field-cooled dc susceptibility deviated below the fieldcooled one with lowering temperature. [DOI : 10.1143/JJAP.44.L979]
Keywords: Fe doped In 2O 3, spin-glass transition, cluster-glass
behavior
Department of Materials Science, Kyushu Institute of Technology, 1-1 Sensui, Tobata, Kitakyushu
804-8550, Japan
1 Department of Electronic Engineering, Kyushu Institute of Technology, 1-1 Sensui, Tobata,
Kitakyushu 804-8550, Japan
2 Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577,
Japan
3 National Institute of Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, JapanAbstracts of Express Letters

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1002-L1004
Part 2, No. 32, 10 July 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1066-L1068
Part 2, No. 34, 10 August 2005
©2005 The Japan Society of Applied Physics

Current Injection Laser Oscillation in
TlInGaAs/GaAs Double Quantum Well Diodes
with InGaP Cladding Layers

Second-Harmonic-Generation Microscopy
Using Excitation Beam with Controlled
Polarization Pattern to Determine
Three-Dimensional Molecular Orientation

Atsushi Fujiwara, Toshikazu Mukai, Takeshi Matsumoto,
Shigehiko Hasegawa and Hajime Asahi*(Received July 7, 2005; accepted July 6, 2005; published July 29, 2005)

TlInGaAsN/AlGaAs heterostructures were proposed for use in the
fabrication of temperature-stable lasing wavelength and threshold current
laser diodes. As a first step, we grew TlInGaAs/GaAs quantum well (QW)
structures on GaAs(100) substrates and demonstrated an electroluminescence (EL) emission of up to 300 K. Compared with InGaAs/GaAs QWs,
we confirmed that the temperature variation of the EL peak energy wasdecreased by the addition of Tl into InGaAs. We also demonstrated thepulsed current injection laser oscillation in the TlInGaAs/GaAs double QW
laser diodes with InGaP cladding layers up to 176 K.
[DOI : 10.1143/JJAP.44.L1002]
Keywords: TlInGaAs, GaAs, semiconductor laser diodes, temperature-insensitive wavelength, molecular beam epitaxy,
WDM optical fiber communication
The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki,
Osaka 567-0047, Japan* Corresponding author. E-mail address: asahi@sanken.osaka-u.ac.jp

Keisuke Yoshiki, Mamoru Hashimoto* and Tsutomu Araki(Received July 15, 2005; accepted July 25, 2005; published August 12, 2005)

We have developed a second-harmonic-generation (SHG) microscopeusing an excitation beam with a controlled polarization pattern in orderto detect three-dimensional molecular orientation. The electric field at thefocus is controlled three-dimensionally by modifying the polarization distribution with a parallel-aligned nematic-liquid-crystal spatial-light-modulator
without any mechanical moving parts. We demonstrated that the SHG
signal from an Achilles tendon, sliced so that collagen fibers were aligned
parallel to the optical axis, excited by a radially polarized beam was higher
than those excited by linearly polarized beams. The possibility of determinating three-dimensional molecular orientation was thus shown.
[DOI : 10.1143/JJAP.44.L1066]
Keywords: three-dimensional molecular orientation, optical
microscopy, SHG microscopy, liquid-crystal spatial-lightmodulator
Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science,
Osaka University, Machikaneyama 1-3, Toyonaka, Osaka 560-8531, Japan* Corresponding author. E-mail address: mamoru@me.es.osaka-u.ac.jp}

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1063-L1065
Part 2, No. 34, 10 August 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1069-L1071
Part 2, No. 34, 10 August 2005
©2005 The Japan Society of Applied Physics

Ta-doped Anatase TiO2 Epitaxial Film as
Transparent Conducting Oxide

Achievement of High Density InAs Quantum
Dots on InP (311)B Substrate Emitting at
1.55 µm

Taro Hitosugi1,2*, Yutaka Furubayashi2, Atsuki Ueda1,
Kinnosuke Itabashi3, Kazuhisa Inaba2,4, Yasushi Hirose2, Go Kinoda2,
Yukio Yamamoto2, Toshihiro Shimada1,2 and Tetsuya Hasegawa1,2(Received July 20, 2005; accepted July 27, 2005; published August 12, 2005)

We present electrical transport and optical properties of Ta-doped
TiO2 epitaxial thin films with varying Ta concentration grown by the pulsed
laser deposition method. The Ti0.95Ta0.05O2 film exhibited a resistivity of
2.5 × 10-4 Ω cm at room temperature, and an internal transmittance of
95% in the visible light region. These values are comparable to thoseof a widely used transparent conducting oxide (TCO), indium tin oxide.
Furthermore, this new material falls into a new category of TCOs thatutilizes d electrons. [DOI : 10.1143/JJAP.44.L1063]
Keywords: pulsed laser deposition, TiO2, transparent conducting
oxide, epitaxial, thin film
1 Department of Chemistry, University of Tokyo, Tokyo 113-0033, Japan
2 Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012, Japan
3 Department of Environmental Chemical Engineering, Kogakuin University, Tokyo 163-8677,
Japan
4 Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503,
Japan* E-mail address: hitosugi@chem.s.u-tokyo.ac.jp

P. Caroff, N. Bertru*, A. Le Corre, O. Dehaese, T. Rohel, I. Alghoraibi,
H. Folliot and S. Loualiche(Received July 11, 2005; accepted July 15, 2005; published August 12, 2005)

The As flux effect on InAs quantum dots formed by gas source molecular beam epitaxy on InP substrates, oriented following the (311)B crystallographic direction has been studied. Atomic force microscopy images
show that the quantum dot (QD) density dramatically increases andquantum dot sizes decrease, when decreasing the As pressure. Moreover,the size dispersion is narrowed. Photoluminescence measurements on thehigh QD density samples is shifted to higher energy, toward the telecommunication important 1.55 µm emission. [DOI : 10.1143/JJAP.44.L1069]
Keywords: InP, InAs, quantum dots, (311)B surface, molecular beam
epitaxy, nanostructures

Laboratoire d’Etude des Nanostructures à Semiconducteurs (LENS), UMR C6082; INSA,
20 Avenue des Buttes de Coësmes, F-35043 Rennes Cedex, France* E-mail address: Nicolas.bertru@insa-rennes.fr

JSAP International No.13 (January 2006)27

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1100-L1102
Part 2, No. 35, 10 August 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1105-L1108
Part 2, No. 35, 10 August 2005
©2005 The Japan Society of Applied Physics

Huge Spin-Polarization of L21-Ordered
Co2MnSi Epitaxial Heusler Alloy Film

Time-Resolved Measurement of Charging
on Hole Bottoms of SiO2 Wafer Exposed to
Plasma Etching in a Pulsed Two-Frequency
Capacitively Coupled Plasma

Yuya Sakuraba, Jun Nakata, Mikihiko Oogane, Hitoshi Kubota1,
Yasuo Ando, Akimasa Sakuma and Terunobu Miyazaki(Received July 19, 2005; accepted July 31, 2005; published August 19, 2005)

Magnetic tunnel junctions (MTJs) with a stacking structure of epitaxial
Co2MnSi/Al−O barrier/poly-crystalline Co75Fe25 were fabricated using an
ultrahigh vacuum sputtering system. The epitaxial Co2MnSi bottom electrode exhibited highly ordered L21 structure and very smooth surface
morphology. Observed magnetoresistance (MR) ratios of 70% at room
temperature (RT) and 159% at 2 K are the highest values to date for MTJs
using a Heusler alloy electrode. A high spin-polarization of 0.89 at 2 K for
Co2MnSi obtained from Julliere’s model coincided with the half-metallic
band structure that was predicted by theoretical calculations.
[DOI : 10.1143/JJAP.44.L1100]
Keywords: Heusler alloy, spin-polarization, half-metal, magnetic
tunnel junction, tunnel magnetoresistance
Department of Applied Physics, Graduate School of engineering, Tohoku University, Aoba-yama
05, Aramaki, Aoba-ku, Sendai 980-8579, Japan
1 Nanoelectronics Research Institute, National Institute of Advanced Industrial Science andTechnology (AIST), 1-1-1 Umezono, Tsukuba 305-8568, Japan

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1103-L1104
Part 2, No. 35, 10 August 2005
©2005 The Japan Society of Applied Physics

InAs Quantum Dot Lasers with Extremely Low
Threshold Current Density (7 A/cm2/Layer)
Hitoshi Shimizu*, Shanmugam Saravanan, Junji Yoshida, Sayoko Ibe1
and Noriyuki Yokouchi1(Received July 22, 2005; accepted August 4, 2005; published August 19, 2005)

This paper describes the successful stacking of multilayered InAs
quantum dots (QD) on a GaAs substrate up to 12 layers. The laser oscillated from the ground state under the condition of mirror loss at less than
7−8 cm-1. The extremely low threshold current density per QD-layer of 7
A/cm2/layer was obtained with a lasing wavelength of 1.21 µm at room
temperature, which is the lowest value for any known semiconductor
laser. [DOI : 10.1143/JJAP.44.L1103]
Keywords: laser, quantum dot, InAs, molecular beam epitaxy,
threshold current density, multilayer

Department of Nonlinear Science, ATR Wave Engineering Laboratories, 2-2-2 Hikaridai,``Keihanna Science City’’, Kyoto 619-0288, Japan
1 Yokohama R&D Laboratories, Furukawa Electric Co., Ltd., 2-4-3 Okano, Nishi-ku, Yokohama
220-0073, Japan* E-mail address: hshimizu@atr.jp

Takeshi Ohmori1*, Takeshi Kamata Goto1, Takeshi Kitajima1,2 andToshiaki Makabe1*(Received July 13, 2005; accepted July 30, 2005; published August 19, 2005)

We experimentally demonstrate a time chart of the shading eitherof electrons or positive ions on a topologically patterned wafer exposed
to plasma etching by synchronized measurements of bottom-charging
potential in a SiO2 hole, current components incident on the wafer, andoptical emission CT in the interface in a pulsed two frequency capacitively
coupled plasma. The present paper gives a history of charging affected
dynamically by an instantaneous electrical response on the bottom.
[DOI : 10.1143/JJAP.44.L1105]
Keywords: pulsed 2f-CCP, charging free process, charging in dielectric etching, emission CT, negative charge injection
1 Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi,
Kohoku-ku, Yokohama 223-8522, Japan
2 Department of Electrical Eng., National Defense Academy, 1-10-20 Hashirimizu, Yokosuka,
Kanagawa 239-8686, Japan* E-mail address: ohmori@mkbe.elec.keio.ac.jp** E-mail address: makabe@mkbe.elec.keio.ac.jp

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1109-L1111
Part 2, No. 35, 10 August 2005
©2005 The Japan Society of Applied Physics

Low-Leakage Polymeric Thin-Film Transistors
Fabricated by Laser Assisted Lift-Off TechniqueSung-Jin Kim1,2, Taek Ahn2, Min Chul Suh2, Chang-Jae Yu1,
Dong-Woo Kim1 and Sin-Doo Lee1*(Received July 20, 2005; accepted July 30, 2005; published August 19, 2005)

Organic thin-film transistors (OTFTs) based on a semiconducting
polymer have been fabricated using a patterning method of the selective
wettability. Laser assisted lift-off (LALO) technique, ablating selectively thehydrophobic layer by an excimer laser, was used for producing a semiconducting polymer channel in the OTFT with high resolution. The selective wettability of a semiconducting polymer, poly(9-9-dioctylfluoreneco -bithiophene) (F8T2), dissolved in a polar solvent was found to define
precisely the pattering resolution of the active channel. It is demonstrated
that in the F8T2 TFTs fabricated using the LALO technique, the leakage ofthe gate current is drastically reduced. [DOI : 10.1143/JJAP.44.L1109]
Keywords: laser assisted lift-off technique, organic TFT, low leakage
current
1 School of Electrical Engineering #32, Seoul National University, Kwanak P.O. Box 34, Seoul
151-742, Korea
2 Corporate R&D Center, Samsung SDI Co., Ltd., 428-5, Gongse-Ri, Kiheung-Eup, Yongin-City,
Gyeonggi-Do, 449-902, Korea* E-mail address: sidlee@plaza.snu.ac.kr

28

JSAP International No.13 (January 2006)

Abstracts of Express Letters

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1138-L1140
Part 2, No. 36, 10 August 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1187-L1189
Part 2, No. 38, 10 September 2005
©2005 The Japan Society of Applied Physics

High-Critical-Temperature Sm- and Nd-Based
Superconductors Produced by Metal Organic
Deposition Using Trifluoroacetates andPentafluoropropionates

First-Principles Materials Design of CuAlO2
Based Dilute Magnetic Semiconducting Oxide

Takeshi Araki* and Izumi Hirabayashi(Received July 27, 2005; accepted August 6, 2005; published August 26, 2005)

Superconducting films for wire, tape, and microwave filter applications require a high critical temperature (T c) and current density (J c). Therefore, superconducting systems based on La, Nd, and Sm produced by
low-cost non-vacuum metal organic deposition using trifluoroacetates(TFA-MOD) are eagerly awaited. These systems are reported to haveexcellent T c values of over 94 K, but esterification between trifluoroacetates and methanol leads to low T c values in the TFA-MOD process. Tworecent studies on carbon expulsion during calcining and on a quasi-liquid
network model during firing suggest new effective chemicals and we
successfully prepared Nd- and Sm-based superconductors using pentafluoropropionic acid. The best Nd- and Sm-based films exhibited T c of 93.4
and 93.9 K and J c of 3.4 and 5.1 MA/cm2 (77 K, 0 T), as measured by the
inductive method, respectively. The film thicknesses were 133 and 181
nm, respectively. [DOI : 10.1143/JJAP.44.L1138]
Keywords: trifluoroacetates, Nd-based superconductor, Sm-based
superconductor, metal organic deposition, non-vacuum
process, carbon expulsion scheme, quasi-liquid networkmodel, pentafluoropropionic acid
Superconductivity Research Laboratory, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062, Japan* Present address: Corporate Research and Development Center, Toshiba Corp., 1 KomukaiToshiba-cho, Saiwai-ku, Kasawaki 212-8582, Japan.
E-mail address: takeshi2.araki@toshiba.co.jp

Hidetoshi Kizaki*, Kazunori Sato, Akira Yanase andHiroshi Katayama-Yoshida(Received August 9, 2005; accepted August 23, 2005; published September 9, 2005)

The electronic structures and the magnetic properties of dilute
magnetic semiconductors (DMSs) based on transparent semiconducting
oxide CuAlO 2 are calculated by using the Korringa−Kohn−Rostoker
method combined with the coherent potential approximation within thelocal density approximation. We see from the results that we can expect
to obtain the half-metallic and high-spin ferromagnetic state is expected
to be stable in Mn-, Fe-, Co- and Ni-doped CuAlO2.
[DOI : 10.1143/JJAP.44.L1187]
Keywords: materials design, CuAlO2, delafossite structure, dilute
magnetic semiconductor, spintronics, half-metallic densityof states
The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki,
Osaka 567-0047, Japan* E-mail address: hide@cmp.sanken.osaka-u.ac.jp

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1190-L1192
Part 2, No. 38, 10 September 2005
©2005 The Japan Society of Applied Physics

Strong Excitonic Emission from(001)-Oriented Diamond P−N Junction
Toshiharu Makino1,2*, Hiromitsu Kato1,2, Masahiko Ogura1,2,
Hideyuki Watanabe1,2, Sung-Gi Ri1,2, Satoshi Yamasaki1,2,3 andHideyo Okushi1,2(Received August 16, 2005; accepted August 28, 2005; published September 9, 2005)

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1141-L1143
Part 2, No. 36, 10 August 2005
©2005 The Japan Society of Applied Physics

Non-equilibrium Phenomenon between
Electron and Lattice Systems Induced by the
Peltier Effect
Hideo Iwasaki, Hidenobu Hori and Shosuke Sasaki1(Received July 25, 2005; accepted August 10, 2005; published August 26, 2005)

Temperature distributions of the electron and lattice systems inducedby the Peltier effect have been precisely measured by improved Harman
method, where the temperature differences (Δ T el and Δ T la) have been
independently evaluated for several terminal lengths (L V) in thermoelectricmaterials (Bi,Sb)2Te3. Both temperature distributions have different behaviors in the stationary state, that is, the L V dependences of Δ T el and Δ T lashow positive and negative curvatures, respectively. It is also indicated thatthe temperature difference has a linear relation to L V in the whole systemand the observed non-equilibrium phenomenon is consistent with a lawof the conservation of heat quantity. [DOI : 10.1143/JJAP.44.L1141]
Keywords: non-equilibrium stationary state, electron and latticesystem, thermoelectricity, Peltier effect, Harman method

We have succeeded in fabricating (001)-oriented diamond p −n junctions with good diode characteristics and realized UV light emission by
current-injection at room temperature. As p −n junctions, a phosphorusdoped n -type layer was formed on (001)-oriented boron-doped p -type
one by applying an optimized homoepitaxial growth technique basedon micro-wave plasma-enhanced chemical vapor deposition. Current−
voltage characteristics showed a rectification ratio of 106 at ± 30 V atroom temperature. The existence of the space-charge layer through thep −n junction was confirmed from capacitance−voltage characteristics. A
strong UV light emission at 235 nm was observed at forward current over
20 mA and is attributed to free exciton recombination.
[DOI : 10.1143/JJAP.44.L1190]
Keywords: diamond, chemical vapor deposition, (001)-oriented p−njunction, light-emitting diode, exciton
1 Diamond Research Center, National Institute of Advanced Industrial Science and Technology(AIST), Tsukuba Center 2, Tsukuba, Ibaraki 305-8568, Japan
2 Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology
Corporation (JST), c/o AIST, Tsukuba, Ibaraki 305-8568, Japan
3 Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki
305-8577, Japan* E-mail address: toshiharu-makino@aist.go.jp

School of Materials Science, JAIST, Nomi, Ishikawa 923-1292, Japan
1 Shizuoka Institute of Science and Technology, Fukuroi, Shizuoka 437-8555, Japan

JSAP International No.13 (January 2006)

29

Abstracts of Express Letters

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1237-L1240
Part 2, No. 40, 10 September 2005
©2005 The Japan Society of Applied Physics

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1267-L1270
Part 2, No. 41, 10 September 2005
©2005 The Japan Society of Applied Physics

Evaluation of Spin-Transfer Switching in
CoFeB/MgO/CoFeB Magnetic Tunnel Junctions

Current-Driven Magnetization Switching in
CoFeB/MgO/CoFeB Magnetic Tunnel Junctions

Hitoshi Kubota1*, Akio Fukushima1, Yuichi Ootani1, Shinji Yuasa1,2,
Koji Ando1, Hiroki Maehara3, Koji Tsunekawa3, David D. Djayaprawira3,
Naoki Watanabe3 and Yoshishige Suzuki1,4Jun Hayakawa1,2*, Shoji Ikeda2, Young Min Lee2, Ryutaro Sasaki2,
Toshiyasu Meguro2, Fumihiro Matsukura2, Hiromasa Takahashi1,2 andHideo Ohno2

Current-induced magnetization switching was demonstrated on
Co−Fe−B/MgO/Co−Fe−B magnetic tunnel junctions (MTJs), which exhibited giant tunnel magnetoresistance ratios of about 100%. Switchingcurrent density at a pulse duration of 100 ms was about 6 × 106 A/cm2
at room temperature. The switching current density was reduced to
one-third of the smallest value for the MgO-based MTJs reported todate. Dependence of the switching current on pulse duration and on theexternal magnetic field was discussed based on a theoretical model incorporating thermally activated spin-transfer switching. The spin-transfer
switching in the MgO-based MTJs realizes low writing power consumption and a high read-out signal in high-density magnetoresistive random
access memory. [DOI : 10.1143/JJAP.44.L1237]
Keywords: spin-transfer switching, MgO, magnetic tunnel junction,
switching current density, tunnel magnetoresistance,magnetoresistive random access memory

Current-driven magnetization switching in low-resistance Co40Fe40B20/
MgO/Co40Fe40B20 magnetic tunnel junctions (MTJs) is reported. The critical-current densities J c required for current-driven switching in samples
annealed at 270 and 300ºC are found to be as low as 7.8 × 105 and 8.8
× 105 A/cm2 with accompanying tunnel magnetoresistance (TMR) ratiosof 49 and 73%, respectively. Further annealing of the samples at 350ºC
increases TMR ratio to 160%, while accompanying J c increases to 2.5 ×
106 A/cm2. We attribute the low J c to the high spin-polarization of tunnel
current and small M sV product of the CoFeB single free layer, where M s is
the saturation magnetization and V the volume of the free layer.
[DOI : 10.1143/JJAP.44.L1267]
Keywords: current-driven magnetization switching, magnetic tunnel
junction, MgO barrier, CoFeB(Received August 24, 2005; accepted September 7, 2005; published September 26, 2005)

1 Nanoelectronics Research Institute (NeRI), National Institute of Advanced Industrial Scienceand Technology (AIST), 1-1-1, Umezono, Tsukuba, Ibaraki 305-8568, Japan
2 PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
3 Electron Device Division, ANELVA Corp., 5-8-1 Yotsuya, Fuchu-shi, Tokyo 183-8508, Japan
4 Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka,
Osaka 560-8531, Japan* E-mail address: hit-kubota@aist.go.jp

Jpn. J. Appl. Phys. Vol. 44 (2005) pp. L1241-L1243
Part 2, No. 40, 10 September 2005
©2005 The Japan Society of Applied Physics

Colossal Electro-Resistance Memory Effect at
Metal/La2CuO4 Interfaces
Akihito Sawa1,2*, Takeshi Fujii1,2,3, Masashi Kawasaki1,3 andYoshinori Tokura1,4(Received August 31, 2005; accepted September 7, 2005; published September 26, 2005)

We have examined the colossal electro-resistance memory effect forthe metal/La2CuO4 (M /LCO) junctions with M = Au, Ti, and Al. Among thejunctions, the Ti and Al/LCO junctions exhibited hysteretic and nonlinear
Schottky-like current−voltage characteristics, whose resistance could also
be switched by pulsed voltage stresses. The resistance switching properties
are similar to those previously reported in a Ti/Pr0.7Ca0.3MnO3 junctions,and can be attributed to the charging effect at the Schottky-like interface.
[DOI : 10.1143/JJAP.44.L1241]
Keywords: Transition-Metal Oxides, Electro-Resistance, Non-volatilememory, Interface, Schottky
1 Correlated Electron Research Center (CERC), National Institute of Advanced Industrial Scienceand Technology (AIST), Tsukuba, Ibaraki 305-8562, Japan
2 CREST-JST, Kawaguchi, Saitama 322-0012, Japan
3 Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
4 Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan* E-mail address: a.sawa@aist.go.jp

30

JSAP International No.13 (January 2006)(Received September 2, 2005; accepted September 13, 2005; published September 30, 2005)

1 Advanced Research Laboratory, Hitachi, Ltd., 1-280 Higashi-Koigakubo, Kokubunji, Tokyo
185-8601, Japan
2 Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan* E-mail address: j-hayaka@rd.hitachi.co.jp