Toshiyuki KAIZU
| Department of Engineering Science | Associate Professor |
| Cluster III (Fundamental Science and Engineering) | Associate Professor |
| Quantum Future Creative Device Development Center | Associate Professor |
Researcher Information
Field Of Study
Career
- Oct. 2024 - Present
The University of Electro-Communications, Quantum Future Creative Device Development Center, Associate Professor, Japan - May 2022 - Oct. 2024
Kyoto University, Nanotechnology Hub, Center for the Promotion of Interdisciplinary Education and Research, 特定研究員, Japan - Apr. 2021 - Mar. 2022
Kobe University, Graduate School of Engineering Department of Electrical and Electronic Engineering, Assistant Professor, Japan - Oct. 2012 - Mar. 2021
Kobe University, Center for Supports to Research and Education Activities, Assistant Professor, Japan - Apr. 2010 - Sep. 2012
The University of Tokyo, Research Center for Advanced Science and Technology, 特任助教 - Apr. 2007 - Mar. 2010
物質・材料研究機構 量子ドットセンター, ポスドク - Oct. 2005 - Mar. 2007
日本原子力研究開発機構 量子ビーム応用研究部門 放射光科学研究ユニット, 特定課題推進員 - Apr. 2004 - Sep. 2005
日本原子力研究所 放射光科学研究センター, 特定課題推進員
Educational Background
- Apr. 2001 - Mar. 2004
The University of Electro-Communications, 電気通信学研究科博士後期課程, 電子工学専攻 - Apr. 1999 - Mar. 2001
The University of Electro-Communications, 電気通信学研究科博士前期課程, 電子工学専攻, Japan - Apr. 1995 - Mar. 1999
The University of Electro-Communications, Faculty of Electro-Communications, Department of Electronic Engineering, Japan
Research Activity Information
Paper
- Photo-Hall Effect Characterization and Terahertz Wave Generation with 1550 nm Excitation in InAs/GaAs Quantum Dot Superlattice Based Photoconductive Antenna
Y. Minami; A. Simmen; T. Kitada; Y. Harada; T. Kaizu; O. Kojima; T. Kita; O. Wada
Journal of Applied Physics, May 2025, Peer-reviwed, The basic photoconductive properties of an InAs/GaAs quantum dot (QD) superlattice have been characterized to develop photoconductive antennas (PCAs) operating with a telecom wavelength excitation for practical terahertz (THz) systems. The multiple-stacked InAs/GaAs QD structure was grown by molecular beam epitaxy and photo-Hall effect measurements were performed under infrared illumination conditions using light-emitting diodes with different emission wavelengths. The results have shown that the sign reversal occurs in the Hall coefficient (RH) as the illumination wavelength changes: RH is negative at 940 nm, and positive at 1550 nm. The photocurrent at 940 nm illumination is ascribed to the electron hole pair generation in QDs, whereas the photocurrent at 1550 nm is dominated by the hole current generated through the midgap states in the structure. The hole dominant photocurrent has been interpreted by a model in which photogenerated electrons are trapped in QDs and the number of mobile electrons are reduced. High dark resistance of the present QD superlattice material provides an advantage for the application to PCA devices. THz wave generation has been demonstrated by the ultrafast 1550 nm pulse excitation of a PCA device fabricated from the QD superlattice.
Scientific journal, English - Lateral photoconductivity of InAs/GaAs quantum dots for 1.5 μm-wavelength excitation photoconductive terahertz antenna devices
Toshiyuki Kaizu; Osamu Kojima; Yasuo Minami; Takahiro Kitada; Yukihiro Harada; Takashi Kita; Osamu Wada
Lead, Japanese Journal of Applied Physics, IOP Publishing, 63, 8, 082002-1-5, 01 Aug. 2024, Peer-reviwed, We report lateral photoconductive properties of multilayer-stacked undoped InAs/GaAs quantum dots (QDs) for the application of photoconductive terahertz (THz) antenna devices that operate in a 1.5 μm-telecom-wavelength band. The excitation power-dependent photocurrent showed a high value without saturation under high excitation power for the excitation wavelength of 1460 nm. From the reflection pump-probe signal, a fast photocarrier lifetime was derived. These results, together with the low dark current characteristic, support the applicability of the multilayer-stacked undoped InAs/GaAs QDs to photoconductive THz antennas operating in a 1.5 μm-wavelength band.
Scientific journal - Yb-doped Y–Al–O thin films with a self-organized columnar structure and their anti-Stokes photoluminescence properties
Y. Nakayama; N. Nakagawa; Y. Matsuo; T. Kaizu; Y. Harada; T. Ishihara; T. Kita
AIP Advances, AIP Publishing, 12, 2, 025110-1-8, 01 Feb. 2022, Peer-reviwed
Scientific journal - Polarization-insensitive fiber-to-fiber gain of semiconductor optical amplifier using closely stacked InAs/GaAs quantum dots
Toshiyuki Kaizu; Tomoya Kakutani; Kouichi Akahane; Takashi Kita
Lead, Japanese Journal of Applied Physics, IOP Publishing, 59, 3, 032002-1-5, 17 Feb. 2020, Peer-reviwed
Scientific journal - Photoelectrochemical Reaction in an Electric Cell with a Porous Carbon Anode
Toshiyuki Kaizu; Yousuke Kawajiri; Masahito Enomoto; Takashi Uchino; Minoru Mizuhata; Yuichi Ichihashi; Keita Taniya; Satoru Nishiyama; Masakazu Sugiyama; Masami Ueno; Takashi Kita
The Journal of Physical Chemistry C, American Chemical Society (ACS), 123, 32, 19447-19452, 24 Jul. 2019
Scientific journal - Wide-wavelength-range control of photoluminescence polarization in closely stacked inas/gaas quantum dots
Toshiyuki Kaizu; Yusuke Tajiri; Takashi Kita
Lead, Journal of Applied Physics, American Institute of Physics Inc., 125, 23, 234304-1-8, 21 Jun. 2019, Peer-reviwed, True, We developed a method of growing closely stacked InAs/GaAs quantum dots (QDs) to control the photoluminescence (PL) polarization characteristics in a wide wavelength range. The emission wavelength of the closely stacked QDs redshifted with decreasing substrate temperature during stacking growth, while the PL polarization characteristic was controlled by the GaAs spacer layer thickness and the number of QD layers. A unified rule for the optimum GaAs spacer layer thickness that both enhances the transverse magnetic (TM)-polarized component and achieves a high PL intensity for all growth temperatures was revealed. 30-layer stacked QDs with the optimum spacer layer thickness grown at substrate temperatures from 430 to 480 °C exhibited TM-enhanced polarization characteristics in the 1.15-1.3 μm band. Moreover, we studied the one-dimensional electronic states in the closely stacked QDs with the optimized GaAs spacer layer thickness by time-resolved PL.
Scientific journal, English - Adiabatic two-step photoexcitation effects in intermediate-band solar cells with quantum dot-in-well structure
S. Asahi,T. Kaizu,T. Kita
Scientific Reports, Nature Publishing Group, 9, 7859-1-8, May 2019, Peer-reviwed, We studied the dynamics of electrons generated by two-step photoexcitation in an intermediate-band solar cell (IBSC) comprising InAs/GaAs/Al0.3Ga0.7As dot-in-well (DWELL) structure using time-resolved photocurrent (TRPC) measurement. The examined IBSC exhibited considerably slower photocurrent decay than a conventional InAs/GaAs quantum dot IBSC, which is due to the extraordina
Scientific journal, English - Carrier collection efficiency of intraband-excited carriers in two-step photon up-conversion solar cells
Shigeo Asahi; Kenta Nishimura; Toshiyuki Kaizu; Takashi Kita
2018 IEEE 7th World Conference on Photovoltaic Energy Conversion, WCPEC 2018 - A Joint Conference of 45th IEEE PVSC, 28th PVSEC and 34th EU PVSEC, Institute of Electrical and Electronics Engineers Inc., 3447-3450, 26 Nov. 2018, Recently, we have proposed a new type solar cells utilizing photon up-conversion phenomenon, called two-step photon up-conversion solar cells for realizing high conversion efficiency solar cells. Here, achieving efficient intraband photoexcitation is indispensable. This solar cell has a simple single- j unction structure containing a hetero-interface. In this study, we investigated the applying electric field dependence of two-step photon up-conversion occurring at the hetero-interface. We found that dense electron accumulation and an appropriate electric field enable to dramatically increase the intraband excitation strength and the carrier collection efficiency at the hetero-interface.
International conference proceedings, English - Two-step photocurrent generation enhanced by the fundamental-state miniband formation in intermediate-band solar cells using a highly homogeneous InAs/GaAs quantum-dot superlattice
Kazuki Hirao; Shigeo Asahi; Toshiyuki Kaizu; Takashi Kita
Applied Physics Express, IOP PUBLISHING LTD, 11, 1, 012301-1-4, Jan. 2018, Peer-reviwed, We studied intermediate-band solar cells (IBSCs) incorporating highly homogeneous InAs/GaAs quantum dot superlattices (QDSLs). The extra photocurrent generated by two-step photon absorption markedly increases at the fundamental state (FS) because the FS miniband has been successfully formed in the QDSL-IBSC by controlling the QD size homogeneity. Here, the carriers excited into the miniband spatially separate in the internal electric field, and the long-lived electrons in the intermediate states of the miniband increase the inter-subband absorption strength. The two-step photocurrent response, therefore, extends toward the longer-wavelength side corresponding to the QDSL-FS at approximately 1.2 mu m. (C) 2018 The Japan Society of Applied Physics
Scientific journal, English - Spatially resolved electronic structure of an isovalent nitrogen center in GaAs
R. C. Plantenga; V. R. Kortan; T. Kaizu; Y. Harada; T. Kita; M. E. Flatte; P. M. Koenraad
Physical Review B, AMER PHYSICAL SOC, 96, 15, 155210-1-8, Oct. 2017, Peer-reviwed, Small numbers of nitrogen dopants dramatically modify the electronic properties of GaAs, generating spatially localized resonant states within the conduction band, pair and cluster states in the band gap, and very large shifts in the conduction-band energies with nonlinear concentration dependence. Cross-sectional scanning tunneling microscopy provides the local electronic structure of single nitrogen dopants at the (110) GaAs surface, yielding highly anisotropic spatial shapes when the empty states are imaged. Measurements of the resonant states relative to the GaAs surface states and their spatial extent allow an unambiguous assignment of specific features to nitrogen atoms at different depths below the cleaved (110) surface. Multiband tight-binding calculations around the resonance energy of nitrogen in the conduction band match the imaged features, verifying that the Green's function method can accurately describe the isolated isovalent nitrogen impurity. The spatial anisotropy is attributed to the tetrahedral symmetry of the bulk lattice and will lead to a directional dependence for the interaction of nitrogen atoms. Additionally, the voltage dependence of the electronic contrast for two features in the filled state imaging suggests these features could be related to a locally modified surface state.
Scientific journal, English - Efficient two-step photocarrier generation in bias-controlled InAs/GaAs quantum dot superlattice intermediate-band solar cells
T. Kada; S. Asahi; T. Kaizu; Y. Harada; R. Tamaki; Y. Okada; T. Kita
Scientific Reports, NATURE PUBLISHING GROUP, 7, 5865-1-10, Jul. 2017, Peer-reviwed, We studied the effects of the internal electric field on two-step photocarrier generation in InAs/GaAs quantum dot superlattice (QDSL) intermediate-band solar cells (IBSCs). The external quantum efficiency of QDSL-IBSCs was measured as a function of the internal electric field intensity, and compared with theoretical calculations accounting for interband and intersubband photoexcitations. The extra photocurrent caused by the two-step photoexcitation was maximal for a reversely biased electric field, while the current generated by the interband photoexcitation increased monotonically with increasing electric field intensity. The internal electric field in solar cells separated photogenerated electrons and holes in the superlattice (SL) miniband that played the role of an intermediate band, and the electron lifetime was extended to the microsecond scale, which improved the intersubband transition strength, therefore increasing the two-step photocurrent. There was a trade-off relation between the carrier separation enhancing the two-step photoexcitation and the electric-field-induced carrier escape from QDSLs. These results validate that long-lifetime electrons are key to maximising the two-step photocarrier generation in QDSL-IBSCs.
Scientific journal, English - Two-step photocurrent generation enhanced by miniband formation in InAs/GaAs quantum dot superlattice intermediate-band solar cells
Sho Watanabe; Shigeo Asahi; Tomoyuki Kada; Kazuki Hirao; Toshiyuki Kaizu; Yukihiro Harada; Takashi Kita
Applied Physics Letters, AMER INST PHYSICS, 110, 19, 193104-1-5, May 2017, Peer-reviwed, We studied the effects of miniband formation on the photocurrent generated by two-step intersubband absorption in an intermediate-band solar cell incorporating an InAs/GaAs quantum dot superlattice (QDSL). The two-step photocarrier generation increases with the electronic state coupling of InAs QDSLs in the intrinsic layer. Because carriers that are excited into the superlattice minibands spatially separate in an internal electric field, the electron-hole recombination rate for the photoexcited carriers decreases, and therefore, the electron lifetime increases. The long-lived electrons in the intermediate states of the QDSL miniband increase the intersubband absorption strength. We confirmed a systematic sensitive change in the two-step photocurrent generation depending on the miniband formation controlled by the temperature. Published by AIP Publishing.
Scientific journal, English - Two-step photon up-conversion solar cells
Shigeo Asahi; Haruyuki Teranishi; Kazuki Kusaki; Toshiyuki Kaizu; Takashi Kita
Nature Communications, NATURE PUBLISHING GROUP, 8, 14962-1-9, Apr. 2017, Peer-reviwed, Reducing the transmission loss for below-gap photons is a straightforward way to break the limit of the energy-conversion efficiency of solar cells (SCs). The up-conversion of below-gap photons is very promising for generating additional photocurrent. Here we propose a two-step photon up-conversion SC with a hetero-interface comprising different bandgaps of Al0.3Ga0.7As and GaAs. The below- gap photons for Al0.3Ga0.7As excite GaAs and generate electrons at the hetero-interface. The accumulated electrons at the hetero-interface are pumped upwards into the Al0.3Ga0.7As barrier by below- gap photons for GaAs. Efficient two-step photon up-conversion is achieved by introducing InAs quantum dots at the hetero-interface. We observe not only a dramatic increase in the additional photocurrent, which exceeds the reported values by approximately two orders of magnitude, but also an increase in the photovoltage. These results suggest that the two-step photon up-conversion SC has a high potential for implementation in the next-generation high-efficiency SCs.
Scientific journal, English - Transverse-magnetic laser oscillation from highly stacked InAs/GaAs quantum dots
Toshiyuki Kaizu; Masaya Suwa; Takaya Andachi; Yukihiro Harada; Takashi Kita
Conference Digest - IEEE International Semiconductor Laser Conference, Institute of Electrical and Electronics Engineers Inc., 02 Dec. 2016, We studied electroluminescence and net-modal gain in 40-stacked InAs/GaAs quantum dot (QD) laser devices. Since the electronic coupling between the QDs enhanced the transverse-magnetic (TM) component, the [110] waveguide devices exhibited a laser oscillation in the TM component as well as the transverse-electric (TE) component.
International conference proceedings, English - Photocarrier transport dynamics in InAs/GaAs quantum dot superlattice solar cells using time-of-flight spectroscopy
T. Tanibuchi; T. Kada; S. Asahi; D. Watanabe; T. Kaizu; Y. Harada; T. Kita
Physical Review B, AMER PHYSICAL SOC, 94, 19, 1-9, Nov. 2016, Peer-reviwed, We studied time-resolved photocarrier transport through InAs/GaAs quantum dot superlattice (QDSL) solar cells (SCs) using time-of-flight spectroscopy with an optical probe QD structure beneath the QDSL. Carriers optically pumped in the top p-GaAs layer were transported through the intrinsic layer, including the QDSLs, before arriving at the probe QDs. The photoexcited carrier density significantly influenced the time-resolved photoluminescence (PL) of the QDSLs and probe QDs. The time-resolved PL profile of the probe QDs indicated that excitation densities in excess of 25nJ/cm(2) drastically decreased the rise time, suggesting rapid carrier transport through the QDSLs. This was also confirmed by QDSL carrier transport dynamics, for which the PL intensity of the excited states decayed rapidly above this excitation power density, 25nJ/cm(2), while the ground state remained constant. These results demonstrate that filling the ground states of QDSLs and starting to populate the excited state miniband accelerates carrier transport in QDSL SCs. Furthermore, according to two-step photon absorption measurements taken with a 1.3-mu m infrared laser light source, electrons play a key role in the generation of extra photocurrent by sub-band-gap photon irradiation.
Scientific journal, English - Polarization characteristics of electroluminescence and net modal gain in highly stacked InAs/GaAs quantum-dot laser devices
Masaya Suwa; Takaya Andachi; Toshiyuki Kaizu; Yukihiro Harada; Takashi Kita
Journal of Applied Physics, AMER INST PHYSICS, 120, 13, 1-6, Oct. 2016, Peer-reviwed, We studied the polarization anisotropy of electroluminescence (EL) and net modal gain characteristics of laser device structures containing 40 stacked InAs/GaAs quantum dot (QD) layers. The electronic coupling between the closely stacked QDs enhanced the transverse-magnetic (TM) polarization component owing to the heavy-and light-hole mixing. Thereby, the [110]-waveguide devices exhibited a laser oscillation of not only the transverse-electric (TE) but also the TM component. Laser oscillation occurred at 1137nm from the first excited state for the 300-mu m-long cavity, while it occurred at 1167 nm from the ground state for the 1000-mu m-long cavity. The polarization anisotropy of the EL intensity strongly depended on the injection current density. The polarized EL intensity was almost isotropic at low injection current density. As the injection current density was increased, the TE component was gradually enhanced, which resulted in a markedly TE-dominant anisotropy above the threshold current density for laser oscillation. The net modal gains evaluated using the Hakki-Paoli method also exhibited a TE-enhanced characteristic with increasing injection current density. As the EL spectra of the TE component have an inhomogeneous broadening narrower than that of the TM component, the TE-mode intensity is likely to be enhanced by the concentration of the injected carriers. Published by AIP Publishing.
Scientific journal, English - Emission-wavelength tuning of InAs quantum dots grown on nitrogen-delta-doped GaAs(001)
Toshiyuki Kaizu; Kohei Taguchi; Takashi Kita
Lead, Journal of Applied Physics, AMER INST PHYSICS, 119, 19, 194306-1-8, May 2016, Peer-reviwed, We studied the structural and photoluminescence (PL) characteristics of InAs quantum dots (QDs) grown on nitrogen (N) (5-doped GaAs(001). The emission wavelength for low-density N-delta doping exhibited a blueshift with respect to that for undoped GaAs and was redshifted with increasing N-sheet density. This behavior corresponded to the variation in the In composition of the QDs. N-delta doping has two opposite and competing effects on the incorporation of Ga atoms from the underlying layer into the QDs during the QD growth. One is the enhancement of Ga incorporation induced by the lattice strain, Which is due to the smaller radius of N atoms. The other is an effect blocking for Ga incorporation, which is due to the large bonding energy of Ga-N or In-N. At a low N-sheet density, the lattice-strain effect was dominant, while the blocking effect became larger with increasing N-sheet density, Therefore, the incorporation of Ga from the underlying layer depended on the N-sheet density. Since the In-Ga intermixing between the QDs and the GaAs cap layer during capping also depended on the size of the as-grown QDs, which was affected by the N-sheet density, the superposition of these three factors determined the composition of the QDs. in addition, the piezoelectric effect, which was induced with increased accumulation of lattice strain and the associated high In composition, also affected the PL properties of the QDs. As a result, tuning of the emission wavelength from 1. to 1.26 mu m was achieved at room temperature. Published by AIP Publishing.
Scientific journal, English - Saturable Two-Step Photocurrent Generation in Intermediate-Band Solar Cells Including InAs Quantum Dots Embedded in Al0.3Ga0.7As/GaAs Quantum Wells
Shigeo Asahi; Haruyuki Teranishi; Naofumi Kasamatsu; Tomoyuki Kada; Toshiyuki Kaizu; Takashi Kita
IEEE Journal of Photovoltaics, IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 6, 2, 465-472, Mar. 2016, Peer-reviwed, We studied in detail the photocurrent generation process in two-step photon absorption in intermediate-band solar cells, including InAs quantum dots embedded in Al0.3Ga0.7As/GaAs quantum wells at room temperature. The photocurrent generated by the two-step photon absorption exhibited saturation as the interband excitation intensity increased in strength. On the other hand, as the intersubband excitation intensity increased, the two-step photoexcitation current deviated from a power law. Furthermore, the two-step photoexcitation current exhibiting saturation and deviation strongly depended on both the interband and intersubband excitation intensities. To interpret these phenomena, we performed a theoretical simulation of the two-step photoexcitation current. The results suggest that the photocurrent saturation and deviation were caused by filling of the intermediate states with electrons. Furthermore, our calculated results indicate that the electron-recombination lifetime in the intermediate states is extremely long. The results of the temperature dependence of the two-step photoexcitation current and the excitation intensity dependence of photoluminescence suggest that efficient electron-hole separation extends electron lifetime.
Scientific journal, English - Effects of rapid thermal annealing on two-dimensional delocalized electronic states of the epitaxial N delta-doped layer in GaAs
Yasuhiro Ogawa; Yukihiro Harada; Takeshi Baba; Toshiyuki Kaizu; Takashi Kita
Applied Physics Letters, AMER INST PHYSICS, 108, 11, 1~4, Mar. 2016, Peer-reviwed, We have conducted rapid thermal annealing (RTA) for improving the two-dimensional (2D) arrangement of electronic states in the epitaxial nitrogen (N) delta-doped layer in GaAs. RTA rearranged the N-pair configurations in the GaAs (001) plane and reduced the number of non-radiative recombination centers. Furthermore, a Landau shift, representing the 2D delocalized electronic states in the (001) plane, was observed at around zero magnetic field intensity in the Faraday configuration. (C) 2016 AIP Publishing LLC.
Scientific journal, English - Polarization anisotropy of electroluminescence and net-modal gain in highly stacked InAs/GaAs quantum-dot laser devices
Toshiyuki Kaizu; Masaya Suwa; Takaya Andachi; Yukihiro Harada; Takashi Kita
2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS), IEEE, 2016, Peer-reviwed
International conference proceedings, English - Transverse-magnetic laser oscillation from highly stacked InAs/GaAs quantum dots
Toshiyuki Kaizu; Masaya Suwa; Takaya Andachi; Yukihiro Harada; Takashi Kita
2016 INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE (ISLC), IEEE, 2016, Peer-reviwed, We studied electroluminescence and net-modal gain in 40-stacked InAs/GaAs quantum dot (QD) laser devices. Since the electronic coupling between the QDs enhanced the transverse-magnetic (TM) component, the [110] waveguide devices exhibited a laser oscillation in the TM component as well as the transverse-electric (TE) component.
International conference proceedings, English - Two-Dimensional Energy Dispersion in Thermally Annealed Epitaxial Nitrogen Atomic Sheet in GaAs
Yasuhiro Ogawa; Yukihiro Harada; Kaizu Toshiyuki; Takashi Kita
2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS), IEEE, 2016, Peer-reviwed
International conference proceedings, English - GaAs first-spacer-layer thickness dependence of polarized photoluminescence properties of closely-stacked InAs/GaAs quantum dots with long-wavelength emission
Yusuke Tajiri; Toshiyuki Kaizu; Takashi Kita
2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS), IEEE, 2016, Peer-reviwed
International conference proceedings, English - Broadband control of emission wavelength of InAs/GaAs quantum dots by GaAs capping temperature
Toshiyuki Kaizu; Takuya Matsumura; Takashi Kita
Lead, Journal of Applied Physics, AMER INST PHYSICS, 118, 15, 154301-1-6, Oct. 2015, Peer-reviwed, We investigated the effects of the GaAs capping temperature on the morphological and photoluminescence (PL) properties of InAs quantum dots (QDs) on GaAs(001). The broadband tuning of the emission wavelength from 1.1 to 1.3 mu m was achieved at room temperature by only adjusting the GaAs capping temperature. As the capping temperature was decreased, the QD shrinkage due to In desorption and In-Ga intermixing during the capping process was suppressed. This led to QDs with a high aspect ratio, and resultantly, the emission wavelength shifted toward the longer-wavelength side. In addition, the linearly polarized PL intensity elucidated anisotropic characteristics reflecting the shape anisotropy of the embedded QDs, in which a marked change in polarization anisotropy occurred at capping temperatures lower than 460 degrees C. (C) 2015 AIP Publishing LLC.
Scientific journal, English - Analyses of saturable behavior of two-step photoexcitation in InAs/GaAs/Al0.3Ga0.7As intermediate-band solar cells
Shigeo Asahi; Haruyuki Teranishi; Naofumi Kasamatsu; Tomoyuki Kada; Toshiyuki Kaizu; Takashi Kita
Zairyo/Journal of the Society of Materials Science, Japan, Society of Materials Science Japan, 64, 9, 690-695, 01 Sep. 2015, Peer-reviwed, We systematically studied two-step photocurrent generation as functions of the excitation intensities for the interband and inter-subband transitions in an InAs/GaAs/Al0.3Ga0.7As dot-in-well (DWELL) intermediate-band solar cell. The two-step photoexcitation current shows saturation as the inter-band excitation intensity becomes strong, and we found that the inter-band excitation intensity showing the current saturation strongly depends on the inter-subband excitation intensity. To interpret the current-saturation behavior, we proposed a model and carried out theoretical simulation. Simulated results excellently reproduce the experimental observations. It has been clarified that the photocurrent saturation is caused by filling the intermediate states with electrons. Furthermore, the recombination lifetime in DWELL was pointed out to be extremely long. Our results suggest that this carrier lifetime is an important key to realize strong enhancement of two-step photoexcitation.
Scientific journal, Japanese - Analysis of optical waveguide mode in closely-stacked InAs/GaAs quantum dot semiconductor optical amplifiers
Masaya Suwa; Tomoyuki Ohashi; Takaya Andachi; Toshiyuki Kaizu; Yukihiro Harada; Takashi Kita
Journal of the Society of Materials Science, Japan, Society of Materials Science Japan, 64, 9, 685-689, 01 Sep. 2015, Peer-reviwed, We performed modal analysis for 40-stacked InAs/GaAs quantum dot semiconductor optical amplifiers (QDSOAs) as a function of the waveguide width using an equivalent refractive index technique. QDSOAs with 5- and 11-μm-waveguide widths show multi-mode operations. The theoretical simulation reproduced well the experimental electroluminescence spectrum and unveiled that the output signals comprise several transverse modes. Besides, we confirmed a waveguide width less than 1.28 μm is essential to realize single-mode QDSOAs. The modal gain spectra were analyzed by using the Hakki-Paoli method. Multi peaks arisen from the multi-mode operation were also observed in the gain spectrum, suggesting precise control of the transverse mode is important for a practical realization of the single-mode device.
Scientific journal, Japanese - Two-step photon absorption in InAs/GaAs quantum-dot superlattice solar cells
T. Kada; S. Asahi; T. Kaizu; Y. Harada; T. Kita; R. Tamaki; Y. Okada; K. Miyano
Physical Review B, AMER PHYSICAL SOC, 91, 20, 201303-1-6, May 2015, Peer-reviwed, We studied the two-step photon absorption (TSPA) process in InAs/GaAs quantum-dot superlattice (QDSL) solar cells. TSPA of subband-gap photons efficiently occurs when electrons are pumped from the valence band to the states above the inhomogeneously distributed fundamental states of QDSLs. The photoluminescence (PL)-excitation spectrum demonstrates an absorption edge attributed to the higher excited states of the QDSLs in between the InAs wetting layer states and the fundamental states of QDSLs. When the absorption edge of the excited state was resonantly excited, the superlinear excitation power dependence of the PL intensity demonstrated that the electron and hole created by the interband transition separately relax into QDSLs. Furthermore, time-resolved PL measurements demonstrated that the electron lifetime is extended by thereby inhibiting recombination with holes, enhancing the second subband-gap absorption.
Scientific journal, English - Saturable Two-step Photo current Generation in Intermediate-band Solar Cells Including InAs Quantum Dots Embedded in Al0.3Ga0.7As/GaAs Quantum Wells
Shigeo Asahi; Haruyuki Teranishi; Naofumi Kasamatsu; Tomoyuki Kada; Toshiyuki Kaizu; Takashi Kita
2015 IEEE 42ND PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC), IEEE, 2015, Peer-reviwed, We have studied detailed photocurrent generation process in the two-step photon absorption in intermediate-band solar cells including InAs quantum dots embedded in Al0.3Ga0.7As/GaAs quantum wells and influence of thermal carrier escape at room temperature. The photocurrent generated by the two-step photon absorption shows saturation as the inter-band excitation intensity becomes strong. and the inter-band excitation intensity showing the saturation behavior strongly depends on the inter-subband excitation intensity. To interpret this phenomenon. we carried out a theoretical simulation based on carrier dynamics considering carrier generation. energy relaxation and thermal carrier escape. The results indicate that the photocurrent saturation is caused by filling the intermediate states with electrons. The shift of the saturation point depending on the inter-subband excitation intensity is caused by the shift of the quasi-Fermi level for the intermediate states.
International conference proceedings, English - Two-Step Photocarrier Generation in InAs/GaAs Quantum Dot Superlattice Intermediate Band Solar Cell
Tomoyuki Kada; Taizo Tanibuchi; Shigeo Asahi; Toshiyuki Kaizu; Yukihiro Harada; Takashi Kita; Ryo Tamaki; Yoshitaka Okada; Kenjiro Miyano
2015 IEEE 42ND PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC), 2015, Peer-reviwed
International conference proceedings, English - Suppression of thermal carrier escape and enhanced two-step photon absorption in quantum-dot intermediate-band solar cells with a high-potential barrier
S. Asahi; H. Teranishi; N. Kasamatsu; T. Kada; T. Kaizu; T. Kita
PHYSICS SIMULATION AND PHOTONIC ENGINEERING OF PHOTOVOLTAIC DEVICES IV, SPIE-INT SOC OPTICAL ENGINEERING, 9358, 2015, We have studied detailed carrier generation process in the two-step photon absorption and influence of thermal carrier escape in quantum-dot intermediate-band solar cells (QD-IBSC). The photocurrent created by the two-step photon absorption shows saturation as the inter-band excitation intensity becomes strong, and the inter-band excitation intensity showing the saturation behavior strongly depends on the inter-subband excitation intensity. To interpret this phenomenon, we carried out a theoretical simulation based on carrier dynamics considering carrier generation, energy relaxation and thermal carrier escape. The results indicate that the photocurrent saturation is caused by filling the intermediate states. The shift of the saturation point depending on the inter-subband excitation intensity is caused by the shift of the quasi-Fermi level for the intermediate states.
International conference proceedings, English - Photoluminescence Properties of InAs Quantum Dots on Nitrogen δ-Doped GaAs
KAIZU TOSHIYUKI; KITA TAKASHI
14th International Symposium on Advanced Fluid Information, 148-149, Nov. 2014
International conference proceedings, English - Suppression of exciton-spin relaxation induced by artificial lateral quantum confinement in GaAs
Takayuki Kiba; T. Tanaka; Yosuke Tamura; Cedric Thomas; Toshiyuki Kaizu; Yoshitaka Okada; Seiji Samukawa; Akihiro Murayama
18th International Conference on Molecular Beam Epitaxy, Sep. 2014, Peer-reviwed
International conference proceedings, English - Suppression of thermal carrier escape and efficient photo-carrier generation by two-step photon absorption in InAs quantum dot intermediate-band solar cells using a dot-in-well structure
S. Asahi; H. Teranishi; N. Kasamatsu; T. Kada; T. Kaizu; T. Kita
Journal of Applied Physics, AMER INST PHYSICS, 116, 6, 063510-1-5, Aug. 2014, Peer-reviwed, We investigated the effects of an increase in the barrier height on the enhancement of the efficiency of two-step photo-excitation in InAs quantum dot (QD) solar cells with a dot-in-well structure. Thermal carrier escape of electrons pumped in QD states was drastically reduced by sandwiching InAs/GaAs QDs with a high potential barrier of Al0.3Ga0.7As. The thermal activation energy increased with the introduction of the barrier. The high potential barrier caused suppression of thermal carrier escape and helped realize a high electron density in the QD states. We observed efficient two-step photon absorption as a result of the high occupancy of the QD states at room temperature. (C) 2014 AIP Publishing LLC.
Scientific journal, English - Polarization-insensitive optical gain characteristics of highly stacked InAs/GaAs quantum dots
Takashi Kita; Masaya Suwa; Toshiyuki Kaizu; Yukihiro Harada
Journal of Applied Physics, AMER INST PHYSICS, 115, 23, 233512-1-5, Jun. 2014, Peer-reviwed, The polarized optical gain characteristics of highly stacked InAs/GaAs quantum dots (QDs) with a thin spacer layer fabricated on an n(+)-GaAs (001) substrate were studied in the sub-threshold gain region. Using a 4.0-nm-thick spacer layer, we realized an electronically coupled QD superlattice structure along the stacking direction, which enabled the enhancement of the optical gain of the [001] transverse-magnetic (TM) polarization component. We systematically studied the polarized electroluminescence properties of laser devices containing 30 and 40 stacked InAs/GaAs QDs. The net modal gain was analyzed using the Hakki-Paoli method. Owing to the in-plane shape anisotropy of QDs, the polarization sensitivity of the gain depends on the waveguide direction. The gain showing polarization isotropy between the TM and transverse-electric polarization components is high for the [110] waveguide structure, which occurs for higher amounts of stacked QDs. Conversely, the isotropy of the [similar to 110] waveguide is easily achieved even if the stacking is relatively low, although the gain is small. (C) 2014 AIP Publishing LLC.
Scientific journal, English - Theoretical analysis of GaAs/AlGaAs quantum dots in quantum wire array for intermediate band solar cell
T. Sogabe; T. Kaizu; Y. Okada; S. Tomić
Journal of Renewable Sustainable Energy, 6, 1, 011206-1-11, Jan. 2014, Peer-reviwed
Scientific journal, English - Fabrication of InAs Qantum Dots on Nitrided GaAs (001) Surface
KAIZU TOSHIYUKI; KITA TAKASHI
13th International Symposium on Advanced Fluid Information, 102-103, Nov. 2013
International conference proceedings, English - Quantum size effects in GaAs nanodisks fabricated using a combination of the bio-template technique and neutral beam etching
Yosuke Tamura; Toshiyuki Kaizu; Takayuki Kiba; Makoto Igarashi; Rikako Tsukamoto; Akio Higo; Weiguo Hu; Cedric Thomas; Mohd Erman Fauzi; Takuya Hoshii; Ichiro Yamashita; Yoshitaka Okada; Akihiro Murayama; Seiji Samukawa
Nanotechnology, 24, 28, 285301-1-6, 19 Jul. 2013, Peer-reviwed, We successfully fabricated defect-free, distributed and sub-20-nm GaAs quantum dots (named GaAs nanodisks (NDs)) by using a novel top-down technique that combines a new bio-template (PEGylated ferritin) and defect-free neutral beam etching (NBE). Greater flexibility was achieved when engineering the quantum levels of ND structures resulted in greater flexibility than that for a conventional quantum dot structure because structures enabled independent control of thickness and diameter parameters. The ND height was controlled by adjusting the deposition thickness, while the ND diameter was controlled by adjusting the hydrogen-radical treatment conditions prior to NBE. Photoluminescence emission due to carrier recombination between the ground states of GaAs NDs was observed, which showed that the emission energy shift depended on the ND diameters. Quantum level engineering due to both diameter and thickness was verified from the good agreement between the PL emission energy and the calculated quantum confinement energy. © 2013 IOP Publishing Ltd.
Scientific journal, English - Application of photoreflectance to advanced multilayer structures for photovoltaics
D. F. Marron; E. Canovas; I. Artacho; C. R. Stanley; M. Steer; KAIZU TOSHIYUKI; Y. Shoji; N. Ahsan; Y. Okada; E. Barrigon; I. Rey-Stolle; C. Algora; A. Marti; A. Luque
Materials Science and Engineering B, 178, 9, 599-608, May 2013, Peer-reviwed
Scientific journal, English - Photoluminescence from GaAs nanodisks fabricated by using combination of neutral beam etching and atomic hydrogen-assisted molecular beam epitaxy regrowth
Toshiyuki Kaizu; Yosuke Tamura; Makoto Igarashi; Weiguo Hu; Rikako Tsukamoto; Ichiro Yamashita; Seiji Samukawa; Yoshitaka Okada
Lead, Applied Physics Letters, AMER INST PHYSICS, 101, 11, 113108-1-4, Sep. 2012, Peer-reviwed, We have fabricated GaAs nanodisk (ND) structures by using a combination of neutral beam etching process and atomic hydrogen-assisted molecular beam epitaxy regrowth. We have observed clear photoluminescence (PL) emissions from GaAs NDs. The peak energy showed a blueshift due to the quantum confinement in three spatial dimensions, and it agreed with the theoretically estimated transition energy. The PL results also showed that the cap-layer disks act as radiative recombination centers. We have confirmed that the PL emission originates from the GaAs NDs, and our approach is effective for the fabrication of high quality ND structures. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752233]
Scientific journal, English - High-density and Sub-20-nm GaAs Nanodisk Array Fabricated Using Neutral Beam Etching Process for High Performance QDs Devices
Yosuke Tamura; Makoto Igarashi; Mohd Erman Fauzi; Rikako Tsukamoto; Toshiyuki Kaizu; Takayuki Kiba; Ichiro Yamashita; Yoshitaka Okada; Akihiro Murayama; Seiji Samukawa
2012 12TH IEEE CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO), IEEE, 2012, III-V compound quantum dots are extremely attractive in researching the quantum effect and developing future quantum photovoltaic devices. We developed a defect-free fabrication process for sub-20-nm gallium arsenide (GaAs) nanodisk using bio-template and neutral beam etching. We successfully fabricated defect-free and high-aspect ratio GaAs/aluminium gallium arsenide (AIGaAs) stack-layered sub-20-nm nanodisk structures. The diameter of the GaAs nanodisk could be precisely controlled from 12 to 18 nm by a combination of Hydrogen-radical treatment and neutral beam etching. We then detected a strong photoluminescence peak originating from the GaAs nanodisk for the first time even when using top-down processes. We found that our fabricated nanodisk array structures have great potential for high performance III-V compound optical quantum dots devices.
International conference proceedings, English - Optical absorption, photo-luminescence and miniband formation of a highly ordered and dense 2-dimensional array of Si nanodisks for quantum dot solar cells
Makoto Igarashi; Chi-Hsien Huang; Xuan-Yu Wang; Mohd Fairuz Budiman; Yosuke Tamura; Takayuki Kiba; Akihiro Murayama; Toshiyuki Kaizu; Yoshitaka Okada; Seiji Samukawa
Conference Record of the IEEE Photovoltaic Specialists Conference, 003511-003515, 2011, We fabricated a highly ordered and dense 2-dimensional array of Si nanodisks (NDs) with our new processes using a bio-template and damage-free neutral beam. Direct-bandgap-like photon emissions were observed from the Si-NDs due to quantum confinement by using time resolved PL measurements. The PL time-profiles were identified in three components (nanosecond region or less) originated in lateral coupling of wave-function i.e. miniband state and localized state in silicon nanodisks. Furthermore, The I-V characteristics of the 2D array of Si-NDs using conductive atomic force microscopy (AFM) indicated that the electronic states of the neighboring NDs were coupled and formed minibands in the 2D array. We also fabricated Si-NDs with an inter-layer of SiC, and found that the SiC matrix could yield a high absorption coefficient without any shift in the bandgap energy (Eg) of the Si-ND structure. © 2011 IEEE.
International conference proceedings, English - Damage-free top-down processes for fabricating two-dimensional array of sub-10-nanometer GaAs nanodiscs using bio-template and neutral beam etching for intermediate band solar cell applications
Mohd Fairuz Budiman; Xuan-Yu Wang; Chi-Hsien Huang; Rikako Tsukamoto; Toshiyuki Kaizu; Makoto Igarashi; Pierre-Andre Mortemousque; Yoshitaka Okada; Akihiro Murayama; Kohei M. Itoh; Yuzo Ohno; Seiji Samukawa
Conference Record of the IEEE Photovoltaic Specialists Conference, 002675-002678, 2011, A series of damage-free fabrication processes for a two-dimensional array of sub-10-nm GaAs nanodiscs was developed by using bio-templates and neutral beam etching. The photoluminescence of GaAs etched with a neutral beam clearly revealed that the processes could accomplish defect-free etching for GaAs. In the bio-template process, a hydrogen-radical treatment was used to remove the native oxide on the GaAs surface, and then neutral beam oxidation (NBO) was used to form a hydrophilic 1-nm-thick GaAs oxide (GaAs-NBO) film. The two-dimensional array of ferritins (protein including a 7-nm-diameter iron core) can be arranged well on hydrophilic GaAs-NBO film. The ferritin protein shell was removed using an oxygen-radical treatment at a low temperature of 280°C without thermal damage to the GaAs. Then, the neutral beam etched the the GaAs to form defect-free nanodisc structure of using the iron core as an etching mask. Finally, the iron oxide core was removed by wet etching with diluted hydrogen chloride and the fabrication process was completed without inflicting any damage to the GaAs. As a result, a two-dimensional array of GaAs quantum dots with a diameter of ∼7 nm, a height of ∼10 nm, a high taper angle of 88°, and a quantum dot density of more than 7×10 11 cm -2 was successfully fabricated without causing any damage to the GaAs. © 2011 IEEE.
International conference proceedings, English - Magnetotransport properties of Yb-doped AlxGa1-xAs/GaAs two-dimensional electron systems
Toshiyuki Kaizu; Yasutaka Imanaka; Kanji Takehana; Tadashi Takamasu
Lead, Physica E: Low-dimensional Systems and Nanostructures, ELSEVIER SCIENCE BV, 42, 4, 1126-1129, Feb. 2010, Peer-reviwed, The magnetotransport properties of three different structured Yb-doped AlxGa1-xAs/GaAs twodimensional electron systems (2DES) were investigated. The Al0.3Ga0.7As:Yb sample showed a clear integer quantum Hall effect (IQHF) irrespective of photoexcitation, whereas the AlAs:Yb samples showed a clear IQHE only under photoexcitation above 1.89 eV. Under a dark condition and photoexcitation below 1.89 eV, the resistance of the AlAs:Yb samples significantly increased in the high-magnetic-field region, suggesting that 2D electrons were scattered by the Yb-related electron trap. From the analysis of a band diagram, the Yb-related states in the AlAs:Yb and Al0.3Ga0.7As:Yb samples were estimated to be located below and above the GaAs conduction band edge, respectively, and the level of the Yb-related state was found to shift with the change in the energy band structure of the host material. (C) 2009 Elsevier B.V. All rights reserved.
Scientific journal, English - Time-Resolved X-ray Diffraction Measurements of High-Density InAs Quantum Dots on Sb/GaAs Layers and the Suppression of Coalescence by Sb-Irradiated Growth Interruption
Naoki Kakuda; Toshiyuki Kaizu; Masamitu Takahasi; Seiji Fujikawa; Koichi Yamaguchi
Japanese Journal of Applied Physics, JAPAN SOC APPLIED PHYSICS, 49, 9, 095602-1-4, 2010, Peer-reviwed, Self-assembly of high-density InAs quantum dots (QDs) on Sb-irradiated GaAs buffer layers was observed in-situ by a time-resolved X-ray diffraction (XRD) technique using a combination of XRD and molecular beam epitaxy. Evolution of dot height and lattice constant was analyzed during InAs QD growth and subsequent growth interruption (GI), and as a result, dislocated giant dots due to coalescence and coherent dots were separately evaluated. An Sb-irradiated GI (Sb-GI) method to be applied after InAs growth was attempted for the suppression of coalescence. Using this method, the XRD intensity of giant dots decreased, and the photoluminescence intensity of InAs QDs was enhanced. High-density InAs QDs without giant dots were produced by using the combination of the QD growth on the Sb-irradiated GaAs buffer layers and the Sb-GI. (C) 2010 The Japan Society of Applied Physics
Scientific journal, English - In situ X-ray diffraction during stacking of InAs/GaAs(001) quantum dot layers and photoluminescence spectroscopy
M. Takahasi; T. Kaizu
Journal of Crystal Growth, ELSEVIER SCIENCE BV, 311, 7, 1761-1763, Mar. 2009, Peer-reviwed, The growth of five layers of InAs quantum dots embedded in GaAs matrices was investigated by in situ synchrotron X-ray diffraction. Time-resolved X-ray diffraction revealed the evolution of the strains and height of quantum dots during the entire growth process including the nucleation of islands and encapsulation with GaAs at various substrate temperatures. Comparisons of in situ X-ray results with postgrowth photoluminescence spectra showed a clear correlation between the structural and optical properties. (C) 2008 Elsevier B.V. All rights reserved.
Scientific journal, English - GaSb(001) Surface Reconstructions Measured at the Growth Front by Surface X-ray Diffraction
B. P. Tinkham; O. Romanyuk; W. Braun; K. H. Ploog; F. Grosse; M. Takahasi; T. Kaizu; J. Mizuki
Journal of Electronic Materials, SPRINGER, 37, 12, 1793-1798, Dec. 2008, Peer-reviwed, Surface x-ray diffraction was employed, in situ, to measure the GaSb(001)-(1 x 5) and (1 x 3) surface phases under technologically relevant growth conditions. We measured a large set of fractional-order in-plane diffraction peaks arising from the superstructure of the surface reconstruction. From the data we calculated two-dimensional (2D) Patterson functions, the peaks of which represent inter-atomic distances weighted by the number of electrons in the individual atoms. For the (1 x 3) phase we obtained good agreement between our data and the beta(4 x 3) model proposed in recent experimental and theoretical work. Our measurements on the Sb-rich (1 x 5) phase provide evidence that the structure under growth conditions is, in fact, different from that of the models previously suggested on the basis of scanning tunneling microscopy (STM). We discuss reasons for this discrepancy as well as the identified structural elements for these reconstructions, which include surface relaxations and subsurface rearrangement.
Scientific journal, English - In situ determination of Sb distribution in Sb/GaAs(001) layer for high-density InAs quantum dot growth
Toshiyuki Kaizu; Masamitu Takahasi; Koichi Yamaguchi; Jun'ichiro Mizuki
Lead, Journal of Crystal Growth, ELSEVIER SCIENCE BV, 310, 15, 3436-3439, Jul. 2008, Peer-reviwed, An Sb-adsorbed GaAs(0 0 1) substrate that serves as a template for high-density InAs quantum dot (QD) growth was investigated using in situ X-ray diffraction. The Sb distribution in the top eight layers from the surface was determined by crystal truncation rod scattering analysis. It was found that Sb atoms penetrated to the eighth layer when GaAs(0 0 1) came in contact with an Sb environment. The amounts of Sb in the first and second layers were, however, saturated at 1/3 atomic layer (AL) and 2/3 AL, respectively. A comparison between the X-ray results and atomic force microscopy observations of the QD density showed that the formation of high-density QDs is correlated with the total amount of Sb in the surface and subsurface layers. (c) 2008 Elsevier B.V. All rights reserved.
Scientific journal, English - Modification of InAs quantum dot structure during annealing
Toshiyuki Kaizu; Masamitu Takahasi; Koichi Yamaguchi; Jun'ichiro Mizuki
Lead, Journal of Crystal Growth, ELSEVIER SCIENCE BV, 301-302, 248-251, Apr. 2007, Peer-reviwed, The structural modification of InAs/GaAs(0 0 1) quantum dots (QDs) grown with 2.0 or 2.7 monolayers (ML) of InAs during annealing was investigated by a combination of in situ X-ray diffraction (XRD), reflection high-energy electron-beam diffraction (RHEED) and ex situ atomic force microscopy (AFM). For 2.0 ML in coverage, QD size increased due to the incorporation of Ga atoms into the QDs, after which QD ripening occurred. For 2.7 ML in coverage, on the other hand, the change in the strain energy due to enhanced intermixing of In and Ga atoms induced a morphological transition from three dimension (3D) to two dimension (2D). These results yielded some useful information about control of the SK QD structure during growth interruption. (c) 2006 Elsevier B.V. All rights reserved.
Scientific journal, English - Study of InAs/GaAs(001) nanoisland growth process by in-situ and real-time X-ray diffraction
Masamitu Takahasi; Toshiyuki Kaizu; Jun'ichiro Mizuki
e-Journal of Surface Science and Nanotechnology, 4, 426-430, 22 Apr. 2006, Peer-reviwed, A monitoring technique for molecular beam epitaxial growth of InAs/GaAs(001) nanoislands is presented. With the help of a combination of synchrotron radiation and a two-dimensional X-ray detector, X-ray diffraction intensity mappings in the reciprocal space have been measured during growth at a rate of 9.6 s per frame. This method provides information on strain distribution and height of Stranski-Krastanov islands under the in situ condition. Because the use of X-rays is not hindered by ambient pressure, this technique is suitable for industry-oriented applications such as organometallic vapor-phase epitaxy as well. © 2006 The Surface Science Society of Japan.
Scientific journal, English - In situ monitoring of internal strain and height of InAs nanoislands grown on GaAs(001)
M Takahasi; T Kaizu; J Mizuki
Applied Physics Letters, AMER INST PHYSICS, 88, 10, 101917-1-3, Mar. 2006, Peer-reviwed, A monitoring technique for molecular beam epitaxial growth of InAs/GaAs(001) nanoislands is presented. With the help of synchrotron radiation, x-ray diffraction intensity mapping in reciprocal space has been measured during growth. The internal strain distribution and height of the Stranski-Krastanov islands were monitored at a temporal resolution of 9.6 s. The relaxation process of internal strain inside the Stranski-Krastanov islands displayed significant dependence on the growth temperature. (c) 2006 American Institute of Physics.
Scientific journal, English - Controlled stacking growth of uniform InAs quantum dots by molecular beam epitaxy
Y Suzuki; T Kaizu; K Yamaguchi
Physica E: Low-dimensional Systems and Nanostructures, ELSEVIER SCIENCE BV, 21, 2-4, 555-559, Mar. 2004, Peer-reviwed, Double-stacked InAs quantum dots (QDs) were grown by molecular beam epitaxy via Stranski-Krastanov growth mode. Transition of the facet formation from {136} plane to {110} plane was observed during the stacking growth of InAs QDs by reflection high-energy electron-beam diffraction. The enhanced growth rate and the different facet formation in the stacking growth were caused by tensile strain of the GaAs underlying layer. Low arsenic pressure and low growth rate conditions played an important role for a perfect coupling and uniformity in the size of the stacked QDs. The narrow photoluminescence line width of 17.6 meV was successfully obtained from the stacked InAs QDs. (C) 2003 Elsevier B.V. All rights reserved.
Scientific journal, English - Self-Formation of Uniform InAs Quantum Dots and Quantum-Dot Chains
K.Yamaguchi; T.Kaizu; T.Kanto; Y.Suzuki
Transactions of the Materials Research Society of Japan, 29, 1, 117-121, Jan. 2004, Peer-reviwed - Facet formation of uniform InAs quantum dots by molecular beam epitaxy
T Kaizu; K Yamaguchi
Lead, Japanese Journal of Applied Physics, INST PURE APPLIED PHYSICS, 42, 6S, 4166-4168, Jun. 2003, Peer-reviwed, Uniform InAs quantum dots were grown by molecular beam epitaxy via the Stranski-Krastanov (SK) growth mode, and the self-size-limiting effects due to facet formation were investigated. The facet formation of the 3D dots depends on the growth conditions. As the growth rate and the arsenic pressure decrease, the crystal orientation of the facet changes from the {136} plane to the {101} plane. After the self-size-limiting effects due to the facet formation, the surface concentration of indium adatoms increases, and the density of the coalescent dots also increases. The low arsenic pressure and the low growth rate are effective conditions for suppressing the coalescence and reducing the size fluctuation of the coherent 3D dots. As a result, it was found that the uniform formation of the InAs quantum dots can be achieved by conventional SK-mode growth under low growth rate and low arsenic pressure conditions.
Scientific journal, English - Uniform formation of two-dimensional and three-dimensional InAs islands on GaAs by molecular beam epitaxy
T Kaizu; K Yamaguchi
Lead, Japanese Journal of Applied Physics, INST PURE APPLIED PHYSICS, 42, 4R, 1705-1708, Apr. 2003, Peer-reviwed, In order to fabricate uniform InAs quantum dots on a GaAs(001) substrate, the shape transition from two-dimensional (2D) to 3D islands was investigated in the case of molecular beam epitaxy via the Stranski-Krastanov growth mode. A critical lateral size of the 2D islands, just before the 3D formation, depended on the growth conditions.. In case of high growth rate and high arsenic pressure conditions, the critical size became small because of the multi nucleation mode. The stacked 2D islands induced a large fluctuation in the critical lateral size and caused large inhomogeneous broadening in the pyramidal 3D dots, which were covered by the stable facets. Therefore, the low growth rate and the low arsenic; pressure were effective conditions to achieve uniform 2D and 3D islands.
Scientific journal, English - Uniform formation process of self-organized InAs quantum dots
K Yamaguchi; T Kaizu; K Yujobo; Y Saito
Journal of Crystal Growth, ELSEVIER SCIENCE BV, 237-239, Part2, 1301-1306, Apr. 2002, Peer-reviwed, Uniform InAs quantum dots (QDs) were successfully grown by molecular beam epitaxy using the conventional Stranski-Krastanov growth mode. Two self-size-limiting (SSL) behaviors of the island size played an important role in achieving the uniform formation of the InAs QDs. In the initial growth stage of the 2-dimensional (2D) InAs platelets, the compressive strain at the stop edge of the 2D islands induced the first SSL behavior of their lateral size. The growth mode transition from 2D to 3D rapidly occurred around 20 nm in the lateral size. The 3D dots were surrounded by four {1 3 6} facets, which provided the second SSL feature. The uniform InAs QDs, grown through two SSL mechanisms, revealed a narrow photoluminescence linewidth of <20 meV. (C) 2002 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Self size-limiting process of InAs quantum dots grown by molecular beam epitaxy
T Kaizu; K Yamaguchi
Lead, Japanese Journal of Applied Physics, INST PURE APPLIED PHYSICS, 40, 3S, 1885-1887, Mar. 2001, Peer-reviwed, In the molecular beam epitaxy (MBE) growth of InAs quantum dots (QDs), we investigated the dot formation via the self size-limiting process. Accumulation of size-limited InAs QDs resulted in narrow inhomogeneous broadening of photoluminescence (PL) linewidth and low energy shift of PL peak position. Atomic force microscopy (AFM) and reflection high-energy electron-beam diffraction (RHEED) observations revealed the appearance of {136} facets on the side wall of size-limited InAs dots. It was proposed that the facet formation played an important role in the self size-limiting behavior.
Scientific journal, English - Stranski-Krastanov growth of InAs quantum dots with narrow size distribution
K Yamaguchi; K Yujobo; T Kaizu
Japanese Journal of Applied Physics, INST PURE APPLIED PHYSICS, 39, 12A, L1245-L1248, Dec. 2000, Peer-reviwed, Coherently strained InAs quantum dots (QDs) with narrow inhomogeneous broadening were grown by molecular beam epitaxy (MBE) using the Stranski-Krastanov (SK) growth mode. The increase in the InAs dot size and decrease in the dot density were induced by surface migration enhancement due to the low arsenic pressure below 6 x 10(-7) Torr. In addition, the low arsenic pressure and the low growth rate produced the self size-limiting effect, which was attributed to the inhibition of indium incorporation. As a result, the narrowest photoluminescence (PL) linewidth of 18.6 meV (14 K) was successfully obtained from the single InAs/GaAs QD layer.
Scientific journal, English
MISC
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田村洋典; 五十嵐誠; THOMAS C; FAUZI M. Erman; HU W; 肥後昭男; 塚本里加子; 海津利行; 星井拓也; 木場隆之; 山下一郎; 岡田至崇; 村山明宏; 寒川誠二
11 Mar. 2013, 応用物理学会春季学術講演会講演予稿集(CD-ROM), 60th, ROMBUNNO.30A-G20-7, Japanese, 201302202457316263 - トップダウン加工GaAsナノディスクにおけるキャリアスピン緩和
木場隆之; 木場隆之; 須崎健太; 田村洋典; 田村洋典; 五十嵐誠; 五十嵐誠; THOMAS C.; THOMAS C.; HU W.; HU W.; 海津利行; 海津利行; 岡田至崇; 岡田至崇; 寒川誠二; 寒川誠二; 寒川誠二; 村山明宏; 村山明宏
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中野廣一; 中野廣一; 海津利行; 星井拓也; 星井拓也; 岡田至崇; 岡田至崇
27 Aug. 2012, 応用物理学会学術講演会講演予稿集(CD-ROM), 73rd, ROMBUNNO.11P-J-14, Japanese, 201202216192999626 - 原子状水素援用MBEによる2次元GaAsナノディスクアレイのGaAs/AlGaAsキャップ層再成長
海津利行; 海津利行; 田村洋典; 田村洋典; 五十嵐誠; 五十嵐誠; HU W; HU W; 寒川誠二; 寒川誠二; 寒川誠二; 岡田至崇; 岡田至崇
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田村洋典; 田村洋典; 五十嵐誠; 五十嵐誠; THOMAS C; THOMAS C; FAUZI M. Erman; FAUZI M. Erman; HU W; HU W; 塚本里加子; 塚本里加子; 海津利行; 海津利行; 星井拓也; 星井拓也; 木場隆之; 木場隆之; 山下一郎; 山下一郎; 岡田至崇; 岡田至崇; 村山明宏; 村山明宏; 寒川誠二; 寒川誠二; 寒川誠二
27 Aug. 2012, 応用物理学会学術講演会講演予稿集(CD-ROM), 73rd, ROMBUNNO.11A-F1-6, Japanese, 201202200797118946 - 2次元Siナノディスクアレイにおけるミニバンド形成と電気伝導性の向上
FAUZI Mohd Erman; FAUZI Mohd Erman; 五十嵐誠; 五十嵐誠; HU Weiguo; HU Weiguo; 海津利行; 海津利行; 岡田至崇; 岡田至崇; 寒川誠二; 寒川誠二; 寒川誠二
27 Aug. 2012, 応用物理学会学術講演会講演予稿集(CD-ROM), 73rd, ROMBUNNO.11A-F1-1, Japanese, 201202245729517798 - 障壁材料としてSiCを用いたSi量子ナノディスクアレイ構造の電気・光学特性
五十嵐誠; 五十嵐誠; 海津利行; 海津利行; 岡田至崇; 岡田至崇; 木場隆之; 木場隆之; 村山明宏; 村山明宏; 寒川誠二; 寒川誠二
16 Aug. 2011, 応用物理学会学術講演会講演予稿集(CD-ROM), 72nd, ROMBUNNO.1A-K-5, Japanese, 201102240790914512 - 高密度InAs量子ドットのSb照射成長中断における時間分解X線回折測定(3)
山本和輝; 角田直輝; 海津利行; 海津利行; 高橋正光; 藤川誠司; 山口浩一
30 Aug. 2010, 応用物理学会学術講演会講演予稿集(CD-ROM), 71st, ROMBUNNO.14A-ZQ-11, Japanese, 201002227006765642 - シリコン(Si)ナノディスク2次元アレイによる高効率光吸収とバンドギャップエネルギー制御の実現
BIN BUDIMAN Mohd Fairuz; HUANG Chi‐Hsien; HUANG Chi‐Hsien; WANG Uan‐Yu; WANG Uan‐Yu; 海津利行; 海津利行; 五十嵐誠; 五十嵐誠; 大島隆治; 大島隆治; 岡田至崇; 岡田至崇; 山下一郎; 山下一郎; 寒川誠二; 寒川誠二
30 Aug. 2010, 応用物理学会学術講演会講演予稿集(CD-ROM), 71st, ROMBUNNO.14P-NC-8, Japanese, 201002257175971754 - 高密度InAs量子ドットのSb照射成長中断における時間分解X線回折測定(2)
角田直輝; 海津利行; 高橋正光; 藤川誠司; 山口浩一
08 Sep. 2009, 応用物理学会学術講演会講演予稿集, 70th, 1, 398, Japanese, 200902238104180998 - Ybドープ2次元電子系におけるYbトラップ準位の考察
海津利行; 高増正; 竹端寛治; 今中康貴
The Physical Society of Japan (JPS), 18 Aug. 2009, 日本物理学会講演概要集, 64, 2, 591-591, Japanese, 1342-8349, 200902228368832122, 110007498159, AA11439205 - 高密度InAs量子ドットのSb照射成長中断における時間分解X線回折測定
角田直輝; 海津利行; 高橋正光; 藤川誠司; 山口浩一
30 Mar. 2009, 応用物理学関係連合講演会講演予稿集, 56th, 1, 450, Japanese, 200902259682874983 - YbドープAlGaAs/GaAs2次元電子系の電気伝導特性の励起エネルギー依存性
海津利行; 高増正; 竹端寛治; 今中康貴
The Physical Society of Japan (JPS), 03 Mar. 2009, 日本物理学会講演概要集, 64, 1, 687-687, Japanese, 1342-8349, 200902229140539740, 110007372289, AA11439205 - YbドープAlGaAs/GaAsヘテロ構造の電気伝導特性の磁場依存性
海津利行; 高増正; 竹端寛治; 今中康貴
The Physical Society of Japan (JPS), 25 Aug. 2008, 日本物理学会講演概要集, 63, 2, 587-587, Japanese, 1342-8349, 200902212701651501, 110006984672, AA11439205 - Ybドープ2次元電子系の強磁場電気伝導特性
高増正; 海津利行; 今中康貴; 竹端寛治
The Physical Society of Japan (JPS), 29 Feb. 2008, 日本物理学会講演概要集, 63, 1, 682-682, Japanese, 1342-8349, 200902211867472900, 110007195080, AA11439205 - In-situ X-ray diffraction study on structural evolution of InAs islands on GaAs(001) during annealing
Masamitu Takahasi; Toshiyuki Kaizu; Jun'ichiro Mizuki
The evolution of strain inside InAs/GaAs(001) quantum dots during annealing after deposition was studied by in situ grazing-incidence X-ray diffraction. The use of synchrotron radiation and two-dimensional detector enabled measurements at a temporal resolution of 9.6 s. The temperature dependence of the structural change during annealing can be interpreted in terms of the miscibility of InAs and GaAs. © 2007 American Institute of Physics., 01 Dec. 2007, AIP Conference Proceedings, 893, 75-76, 0094-243X, 77958515348 - YbドープGaAs/AlGaAsヘテロ構造の発光,輸送特性
高増正; 海津利行; 今中康貴; 竹端寛治
The Physical Society of Japan (JPS), 21 Aug. 2007, 日本物理学会講演概要集, 62, 2, 682-682, Japanese, 1342-8349, 200902219051471729, 110007142780, AA11439205 - 分子線エピタキシャル法による半導体ナノ構造成長のその場X線回折
高橋正光; 海津利行; 水木純一郎
27 Mar. 2007, 応用物理学関係連合講演会講演予稿集, 54th, 0, 109, Japanese, 200902264153217199 - Sb照射GaAs(001)表面のその場X線回折測定
海津利行; 高橋正光; 菅藤徹; 築地伸和; 外村慎一; 山口浩一; 水木純一郎
27 Mar. 2007, 応用物理学関係連合講演会講演予稿集, 54th, 1, 448, Japanese, 200902283227089745 - リアルタイム計測:半導体ナノドット成長過程における構造変化
高橋正光; 海津利行
29 Aug. 2006, 応用物理学会学術講演会講演予稿集, 67th, 0, 10, Japanese, 200902287441777115 - InAs/GaAs(001)成長のリアルタイムX線回折測定
高橋正光; 海津利行; 水木純一郎
22 Mar. 2006, 応用物理学関係連合講演会講演予稿集, 53rd, 1, 323, Japanese, 200902209194865919 - その場X線回折による成長中継中のInAs量子ドットの構造変化の解析
海津利行; 高橋正光; 佐藤峻之; 堀田正憲; 山口浩一; 水木純一郎
29 Mar. 2005, 応用物理学関係連合講演会講演予稿集, 52nd, 1, 348, Japanese, 200902232994993216 - InAs/GaAs(001)量子ドット成長のリアルタイムX線測定
高橋正光; 海津利行
29 Mar. 2005, 応用物理学関係連合講演会講演予稿集, 52nd, 0, 109, Japanese, 200902239386436015 - 自己制限InAs量子ドットの構造安定性
岩崎誠樹; 海津利行; 山口浩一
28 Mar. 2004, 応用物理学関係連合講演会講演予稿集, 51st, 1, 357, Japanese, 200902224047187998 - 高密度・高均一InAs量子ドットの積層成長
海津利行; 山口浩一
30 Aug. 2003, 応用物理学会学術講演会講演予稿集, 64th, 1, 268, Japanese, 200902297846357941 - GaAs埋め込みInAs量子ドットの1.3μm発光
海津利行; 武田宙; 山口浩一
30 Aug. 2003, 応用物理学会学術講演会講演予稿集, 64th, 3, 1269, Japanese, 200902219115129850 - 自己制限InAs量子ドット形成過程のInAs成長条件依存性 (2)
海津利行; 山口浩一
27 Mar. 2003, 応用物理学関係連合講演会講演予稿集, 50th, 3, 1460, Japanese, 200902262766094690 - 自己制限InAs量子ドット形成過程のInAs成長条件依存性
海津利行; 山口浩一
24 Sep. 2002, 応用物理学会学術講演会講演予稿集, 63rd, 1, 281, Japanese, 200902147688912507 - InAs量子ドットのサイズ自己制限過程
海津利行; 山口浩一
27 Mar. 2002, 応用物理学関係連合講演会講演予稿集, 49th, 1, 336, Japanese, 200902151761920847 - InAs2次元成長層のアニールによる3次元ドット形成
岩崎誠樹; 海津利行; 山口浩一
27 Mar. 2002, 応用物理学関係連合講演会講演予稿集, 49th, 1, 335, Japanese, 200902107441845481 - InAsアイランドサイズの形成位置依存性
海津利行; 山口浩一
11 Sep. 2001, 応用物理学会学術講演会講演予稿集, 62nd, 1, 230, Japanese, 201202105086897494 - 自己組織化InAsドットの初期形成過程
市原純; 海津利行; 山口浩一
28 Mar. 2001, 応用物理学関係連合講演会講演予稿集, 48th, 3, 1345, Japanese, 201202191468317386 - 自己制限InAs量子ドットのファセット形成過程
海津利行; 山口浩一
28 Mar. 2001, 応用物理学関係連合講演会講演予稿集, 48th, 3, 1345, Japanese, 201202155098573217 - Narrow Size Distribution of Facet-Formed InAs Quantum Dots
2001, Proceedings of the 6th International Symposium on Advanced Physical Fields 2001, 330-334 - 自己組織化InAs量子ドットの低成長速度形成
祐乗坊邦彦; 海津利行; 山口浩一
03 Sep. 2000, 応用物理学会学術講演会講演予稿集, 61st, 1, 252, Japanese, 201202184180522159 - 自己制限InAs量子ドットの形成過程
海津利行; 山口浩一
03 Sep. 2000, 応用物理学会学術講演会講演予稿集, 61st, 3, 1150, Japanese, 201202164240085470 - High uniform growth of self-organized InAs quantum dots - Self-limiting effect of dot size.
YAMAGUCHI KOICHI; KAIZU TOSHIYUKI; YUJOBOU KUNIHIKO
In Stranski-Krastanov (SK) mode growth of the InAs, a self-limiting effect of quantum dot (QD) size was observed. As a result, size fluctuation was effectively suppressed, and, a narrow photoluminescence (PL) line width of 21.3 meV was achieved. The self-limiting behavior of pyramidal InAs dots was mainly attributed by the formation of the stable facet. The temperature dependence of PL intensity indicated thermal emission and incorporation of electrons between QDs with different size. Low arsenic pressure during the InAs growth allowed large self-limiting size of coherent dots and low density of coalescent dots., The Institute of Electronics, Information and Communication Engineers, 21 Jun. 2000, 電子情報通信学会技術研究報告, 100, 115(LQE2000 14-25), 13-20, Japanese, 0913-5685, 200902126606698149, 110003308075, AN10442705 - 自己組織化InAs量子ドットの低As圧成長
祐乗坊邦彦; 海津利行; 山口浩一
28 Mar. 2000, 応用物理学関係連合講演会講演予稿集, 47th, 1, 324, Japanese, 201202151984262880 - 自己組織化InAs量子ドットサイズの自己制限効果(2)
海津利行; 祐乗坊邦彦; 山口浩一
28 Mar. 2000, 応用物理学関係連合講演会講演予稿集, 47th, 1, 486, Japanese, 201202197495067446 - 自己組織化InAs量子ドットサイズの自己制限効果
海津利行; 山口浩一
01 Sep. 1999, 応用物理学会学術講演会講演予稿集, 60th, 1, 393, Japanese, 200902122007669224 - 高均一InAs自己形成量子ドットの発光特性
海津利行; 寺沢博雅; 山口浩一
28 Mar. 1999, 応用物理学関係連合講演会講演予稿集, 46th, 1, 540, Japanese, 200902111138872155
Lectures, oral presentations, etc.
- 半導体光共振器中での電気光学効果を利用したテラヘルツ電界センサ： 位相差信号の共振器Q値依存性
原田幸弘; 北田貴弘; 海津利行; 南康夫; 小島磨; 喜多隆; 和田修
Oral presentation, Japanese, 第72回応用物理学会春季学術講演会, Domestic conference
17 Mar. 2025
14 Mar. 2025- 17 Mar. 2025 - 半導体光共振器中での電気光学効果を利用したテラヘルツ電界センサ：結晶面方位の検討
北田貴弘; 原田幸弘; 海津利行; 南康夫; 小島磨; 喜多隆; 和田修
Oral presentation, Japanese, 第72回応用物理学会春季学術講演会, Domestic conference
17 Mar. 2025
14 Mar. 2025- 17 Mar. 2025 - 逆積み構造太陽電池のスマートスタックに向けたエピタキシャル薄膜の3回転写プロセス開発
切柳匠登; 宮下直也; 牧田紀久夫; 菅谷武芳; 海津利行; 山口浩一
Poster presentation, Japanese, 第72回応用物理学会春季学術講演会, Domestic conference
16 Mar. 2025
14 Mar. 2025- 17 Mar. 2025 - 面内超高密度量子ドットにおける強結合遷移モデル
甲斐涼雅; 海津利行; 宮下直也; 山口浩一
Poster presentation, Japanese, 第72回応用物理学会春季学術講演会, Domestic conference
16 Mar. 2025
14 Mar. 2025- 17 Mar. 2025 - Si基板上のInAsナノワイヤーからの横方向成長によるInAs薄膜成長
アチャリヤ淳一; 海津利行; 宮下 直也; 山口 浩一
Oral presentation, Japanese, 第72回応用物理学会春季学術講演会, Domestic conference
16 Mar. 2025
14 Mar. 2025- 17 Mar. 2025 - InAs量子ドット成長に起因する格子不整合歪みを利用した差周波混合によるテラヘルツ電磁波発生
鈴木崇斗; 小島磨; 海津利行; 和田修; 喜多隆
Oral presentation, Japanese, 第85回応用物理学会秋季学術講演会, Domestic conference
16 Sep. 2024
16 Sep. 2024- 20 Sep. 2024 - 多重積層InAs/ GaAs量子ドットを用いた光伝導アンテナの様々な励起光波長における光電流の励起光強度依存性
海津利行; 小島磨; 南康夫; 北田貴弘; 原田幸弘; 喜多隆; 和田修
Oral presentation, Japanese, 第85回応用物理学会秋季学術講演会, Domestic conference
16 Sep. 2024
16 Sep. 2024- 20 Sep. 2024 - Lateral Photoconductivity of Multiple-Stacked InAs/GaAs Quantum Dot Structure for Photoconductive Antenna Device
T. Kaizu; I. Kohama; Y. Minami; T. Kitada; Y. Harada; O. Kojima; T. Kita; O. Wada
Oral presentation, English, Compund Semiconductor Week 2021, International conference
12 May 2021
09 May 2021- 13 May 2021 - 光伝導アンテナ応用へ向けた多重積層InAs/GaAs量子ドットの電気特性評価
南康夫; 新免歩; 北田 貴弘; 原田幸弘; 海津利行; 小島磨; 喜多隆; 和田修
Poster presentation, Japanese, 第68回応用物理学会春季学術講演会, Domestic conference
19 Mar. 2021
16 Mar. 2021- 19 Mar. 2021 - 光伝導アンテナ応用へ向けた多重積層InAs/GaAs量子ドットの光学特性評価
海津利行; 小濱一晟; 南康夫; 北田貴弘; 原田幸弘; 小島磨; 喜多隆; 和田修
Japanese, 第68回応用物理学会春季学術講演会, Domestic conference
19 Mar. 2021
16 Mar. 2021- 19 Mar. 2021 - Polarization-Insensitive Optical Gain of Highly stacked InAs/GaAs Quantum Dot Semiconductor Optical Amplifier
T. Kaizu; T. Kakutani; T. Kita
Oral presentation, English, SmiconNano2019, Kobe, Japan, International conference
25 Sep. 2019
24 Sep. 2019- 27 Sep. 2019 - One-Dimensional Electronic States in Highly-Stacked InAs/GaAs Quantum Dot Superlattices
KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, Compound Semiconductor Week 2019, Nara, International conference
May 2019 - 近接積層InAs/GaAs量子ドット超格子の1次元電子状態の測定温度依存性
海津利行; 喜多隆
Oral presentation, Japanese, 第66回応用物理学会春季学術講演, Domestic conference
11 Mar. 2019
09 Mar. 2019- 12 Mar. 2019 - “Effects of GaAs-Capping Temperature on The Emission Wavelength of InAs Quantum Dots Grown on Nitrogen-Doped GaAs(001)Surfaces
NAOTO UENISHI; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 20th International Conference on Molecular Beam Epitaxy, China, International conference
Sep. 2018 - 多孔質炭素電極を用いた光化学電池の基礎特性
ENOMOTO MASAHITO; WAKAKI HIROTOMO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, Japanese, 平成30年度半導体エレクトロニクス部門委員会第1回研究会, 奈良先端科学技術大学院大学, Domestic conference
Jul. 2018 - Carrier Collection Efficiency of Intraband-Excited Carriers in Two-Step Photon Up-Conversion Solar Cells
ASAHI SHIGEO; K. Nishimura; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 7th edition of the World Conference on Photovoltaic Energy Conversion, Hawaii, International conference
Jun. 2018 - Multiple Stacking of Capping Temperature-Controlled InAs/GaAs Quantum Dots with AlGaAs Barrier Layers for Broadband Emission
KAIZU TOSHIYUKI; T. Koike; KITA TAKASHI
Oral presentation, English, Compound Semiconductor Week 2018, Cambridge, MA, USA, International conference
May 2018 - One-Dimensional Electronic States in Closely Stacked InAs/GaAs Quantum Dots with Different Growth Temperatures
KAIZU TOSHIYUKI; K. Hirao; KITA TAKASHI
Oral presentation, English, International Conference on Nanophotonics and Nano-optoelectronics 2018, Yokohama, International conference
Apr. 2018 - Extraction Efficiency of Up-Converted Electrons in Two-Step Photon Up-Conversion Solar Cells
ASAHI SHIGEO; K. Nishimura; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, International Conference on Nanophotonics and Nano-optoelectronics 2018, Yokohama, International conference
Apr. 2018 - Two-Step Photo-Excitated Electrons with Extremely-Long Lifetime in Intermedeate-band Solar Cells Using Dot-in Well Strucyure
ASAHI SHIGEO; H. Teranishi; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 27th Photovoltaic Science and Engineering Conference, Otsu, International conference
Nov. 2017 - Infrared Absorption Characteristics in Two-Step Photon Up-Conversion Solar Cells
K. Kusaki; ASAHI SHIGEO; KAIZU TOSHIYUKI; R. Tamaki; Y. Okada; KITA TAKASHI
Oral presentation, English, 27th Photovoltaic Science and Engineering Conference, Otsu, International conference
Nov. 2017 - Efficient Two-Step Photocurrent in Intermediate Band Solar Cells Using Highly Homogeneous InAs/GaAs Quantum-Dot Superlattice
K. Hirao; ASAHI SHIGEO; KAIZU TOSHIYUKI; HARADA YUKIHIRO; KITA TAKASHI
Oral presentation, English, 27th Photovoltaic Science and Engineering Conference, Otsu, International conference
Nov. 2017 - One-Dimensional Miniband Formation in InAs/GaAs Quantum Dot Superlattice
KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, International Symposium on Novel Energy Nanomaterials, Catalysts and Surfaces for Future Earth -Material Research, Characterization and Imaging by In situ/Operando XAFS and X-ray Techniques-, Tokyo, International conference
Oct. 2017 - Laser-induced Hydrogen Production Using Porous Carbon
M. Enomoto; Y. Kawajiri; KAIZU TOSHIYUKI; T. Uchino; Y. Ichihashi; K. Taniya; S. Nishiyama; M. Mizuhata; M. Sugiyama; M. Ueno; KITA TAKASHI
Oral presentation, English, International Symposium on Novel Energy Nanomaterials, Catalysts and Surfaces for Future Earth -Material Research, Characterization and Imaging by In situ/Operando XAFS and X-ray Techniques-, Tokyo, International conference
Oct. 2017 - 低温キャップInAs/GaAs量子ドット超格子中間バンド型太陽電池における熱脱出の抑制
平尾 和輝; ASAHI SHIGEO; KAIZU TOSHIYUKI; HARADA YUKIHIRO; KITA TAKASHI
Oral presentation, Japanese, 第78回応用物理学会秋季学術講演会, Domestic conference
Sep. 2017 - 低温キャップInAs/GaAs量子ドット超格子中間バンド型太陽電池における2段階光吸収の増強
平尾 和輝; ASAHI SHIGEO; KAIZU TOSHIYUKI; HARADA YUKIHIRO; KITA TAKASHI
Oral presentation, Japanese, 日本材料学会半導体エレクトロニクス部門委員会平成29年度第1回研究会, Domestic conference
Sep. 2017 - Photon Up-Converted Photocurrent in a Single Junction Solar Cell with a Hetero-Interface
K. Kusaki; ASAHI SHIGEO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 33rd European Photovoltaic Solar Energy Conference and Exhibition, Netherlands, International conference
Sep. 2017 - Increasing Photovoltage Boosted by Photon Up-Conversion in a Single-Junction Solar Cell with a Hetero-Interface
ASAHI SHIGEO; K. Kusaki; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 33rd European Photovoltaic Solar Energy Conference and Exhibition, Netherlands, International conference
Sep. 2017 - Extended Optical Response of Two-Step Photoexcitation in InAs/GaAs Quantum-Dot Superlattice Intermediate Band Solar Cells
K. Hirao; ASAHI SHIGEO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 33rd European Photovoltaic Solar Energy Conference and Exhibition, Netherlands, International conference
Sep. 2017 - Stokes and Anti-Stokes Photoluminescence in Nitrogen ð-Doped Layer in GaAs
HARADA YUKIHIRO; Y. Ogawa; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 29th International Conference on Defects in Semiconductors, Matsue, International conference
Jul. 2017 - Increasing Current Generation by Photon Up-Conversion in a Single-Junction Solar Cell with a Hetero-Interface
ASAHI SHIGEO; K. Kusaki; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 2017 IEEE Photovoltaic Specialists Conference, Washington D.C., International conference
Jun. 2017 - Broadband Control of Polarization Characteristics in Closely-Stacked InAs/GaAs Quantum Dots
KAIZU TOSHIYUKI; Y. Tajiri; KITA TAKASHI
Oral presentation, English, Compound Semiconductor Week 2017, Berlin, International conference
May 2017 - GaAs中のエピタキシャル窒素膜における反ストークス発光
HARADA YUKIHIRO; 小川 泰弘; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, Japanese, 第64回応用物理学会春季学術講演会, Domestic conference
Mar. 2017 - GaAs中のデルタドーピング窒化層を利用した光によるフォノン制御
小川 泰弘; HARADA YUKIHIRO; KAIZU TOSHIYUKI; KITA TAKASHI
Poster presentation, Japanese, 第27回光物性研究会, Domestic conference
Dec. 2016 - Two-dimensional delocalized electronic states of epitaxial N d-doped layer in GaAs
Y. Harada; Y. Ogawa; T. Kaizu; T. Kita
Invited oral presentation, English, Energy, Materials, and Nanotechnology Meeting on Epitaxy, Invited, International conference
Sep. 2016 - InAs/GaAs量子ドット中間バンド型太陽電池における電子の熱脱出過程の解明
平尾 和輝; 渡辺 翔; ASAHI SHIGEO; KAIZU TOSHIYUKI; HARADA YUKIHIRO; KITA TAKASHI
Oral presentation, Japanese, 第77回応用物理学会秋季学術講演会, Domestic conference
Sep. 2016 - Control In-Ga Intermixing in InAs Quantum Dot on Nitrogen δ-Doped GaAs
KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 19th International Conference on Molecular-Beam Epitaxy, Montpellier, International conference
Sep. 2016 - Spatial Electronic Structure of an Isovalent Nitrogen Center in GaAs
R. Plantenga; V. Kortan; KAIZU TOSHIYUKI; HARADA YUKIHIRO; KITA TAKASHI; M. Flatte; P. Koenraad
Oral presentation, English, 33rd International Conference on the Physics of Semiconductors, Beijing, International conference
Aug. 2016 - Thermal carrier-escape process from the intermediate band in InAs/GaAs quantum dot solar cells
K. Hirao; S. Asahi; S. Watanabe; T. Kaizu; Y. Harada; T. Kita
Poster presentation, Japanese, 第35回電子材料シンポジウム, Domestic conference
Jul. 2016 - Two-Dimensional Energy Dispersion in Thermally Annealed Epitaxial Nitrogen Atomic Sheet in GaAs
Y. Ogawa; HARADA YUKIHIRO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 2016 Compound Semiconductor Week, Toyama, International conference
Jun. 2016 - Polarization Anisotropy of Electroluminescence and Net-Modal Gain in Highly Stacked InAs/GaAs Quantum-Dot Laser Devices
KAIZU TOSHIYUKI; M. Suwa; T. Andachi; HARADA YUKIHIRO; KITA TAKASHI
Oral presentation, English, 2016 Compound Semiconductor Week, Toyama, International conference
Jun. 2016 - GaAs First-Spacer-Layer Thickness Dependence of Polarized Photoluminescence Properties of Closely-Stacked InAs/GaAs Quantum Dots with Long-Wavelength Emission
Y. Tajiri; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 2016 Compound Semiconductor Week, Toyama, International conference
Jun. 2016 - Extended Electron Lifetime in Intermediate-Band Solar Cells Using Dot-in-Well Structure
S. Asahi; H. Teranishi; S. Watanabe; T. Kada; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 32nd European Photovoltaic Solar Energy Conference and Exhibition, Munich, International conference
Jun. 2016 - Enhancement of Two-Step Photon Absorption Due to Miniband Formation in InAs/GaAs Quantum Dot Superlattice Solar Cell
S. Watanabe; S. Asahi; T. Kada; KAIZU TOSHIYUKI; HARADA YUKIHIRO; KITA TAKASHI
Oral presentation, English, 32nd European Photovoltaic Solar Energy Conference and Exhibition, Munich, International conference
Jun. 2016 - 急速熱アニールしたGaAs中のエピタキシャル窒素膜の輻射再結合寿命
小川 泰弘; HARADA YUKIHIRO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, Japanese, 第63回応用物理学会春季学術講演会, Domestic conference
Mar. 2016 - Time-Resolved Photoluminescence of Thermally-Annealed Nitrogen Atomic Sheet in GaAs
Y. Ogawa; HARADA YUKIHIRO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 17th International Conference on Physics of Light-Matter Coupling in Nanostructures, Nara, International conference
Mar. 2016 - Polarized Photoluminescence Properties of Closely-Stacked InAs/GaAs Quantum Dots with Long-Wavelength Emission
KAIZU TOSHIYUKI; Y. Tajiri; KITA TAKASHI
Oral presentation, English, 17th International Conference on Physics of Light-Matter Coupling in Nanostructures, Nara, International conference
Mar. 2016 - InAs/GaAs量子ドット超格子太陽電池におけるミニバンド形成が2段階光吸収に与える影響
渡辺 翔; 朝日 重雄; 加田 智之; KAIZU TOSHIYUKI; HARADA YUKIHIRO; KITA TAKASHI
Oral presentation, Japanese, 第63回応用物理学会春季学術講演会, Domestic conference
Mar. 2016 - Extremely Long Carrier Lifetime Due to Electron-Hole Separation in Quantum-Dot Intermediate-Band Solar Cells
S. Asahi; H. Teranishi; T. Kada; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 17th International Conference on Physics of Light-Matter Coupling in Nanostructures, Nara, International conference
Mar. 2016 - InAs/GaAs量子ドット超格子を利用したホットキャリア型太陽電池
渡部 大樹; HARADA YUKIHIRO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, Japanese, 第76回応用物理学会秋季学術講演会, Domestic conference
Sep. 2015 - Epitaxial Nitrogen Atomic Sheet in GaAs Grown by Nitorogen δ-Doping Technique
HARADA YUKIHIRO; T. Baba; Y. Ogawa; KAIZU TOSHIYUKI; KITA TAKASHI
Invited oral presentation, English, 5th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures, Invited, Taiwan, International conference
Sep. 2015 - 急速熱アニールによるGaAs中のエピタキシャル窒素シートにおける2次元物性の制御
小川 泰弘; HARADA YUKIHIRO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, Japanese, 日本材料学会半導体エレクトロニクス部門委員会平成27年度第1回研究会, Domestic conference
Jul. 2015 - Enhancement of Two Dimensionality in Epitaxial Nitrogen Atomic Sheet in GaAs by Rapid Thermal Annealing
HARADA YUKIHIRO; Y. Ogawa; T. Baba; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 21st International Conference on Electronic Properties of Two-Dimensional Systems/17th International Conference on Modulated Semiconductor Structures, Sendai, International conference
Jul. 2015 - Broadband Control of Emission Wavelength of InAs/GaAs Quantum Dots by Growth Temperature GaAs Capping Layer
T. Kaizu; T. Matsumura; KITA TAKASHI
Oral presentation, English, 21st International Conference on Electronic Properties of Two-Dimensional Systems/17th International Conference on Modulated Semiconductor Structures, Sendai, International conference
Jul. 2015 - Annealing effects on the delocalized electronic states of epitaxial two-dimensional nitrogen atomic sheet in GaAs
Y. Ogawa; Y. Harada; T. Baba; T. Kaizu; T. Kita
Poster presentation, Japanese, 34th Electronic Materials Symposium, Domestic conference
Jul. 2015 - Two-Step Photocarrier Generation in InAs/GaAs Quantum Dot Superlattice Intermediate Band Solar Cell
T. Kada; T. Tanibuchi; S. Asahi; T. Kaizu; Y. Harada; KITA TAKASHI; R. Tamaki; Y. Okada; K. Miyano
Oral presentation, English, 42nd IEEE Photovoltaic Specialists Conference, New Orleans, International conference
Jun. 2015 - Saturable Two-Step Photocurrent Generation in Intermediate-Band Solar Cells Including InAs Quantum Dots Embedded in Al0.3Ga0.7As/GaAs Quantum Wells
S. Asahi; H. Teranishi; N. Kasamatsu; T. Kada; T. Kaizu; KITA TAKASHI
Oral presentation, English, 42nd IEEE Photovoltaic Specialists Conference, New Orleans, International conference
Jun. 2015 - GaAs中のエピタキシャル二次元窒素膜におけるアニール効果
HARADA YUKIHIRO; 小川 泰弘; 馬場 健; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, Japanese, 第62回応用物理学会春季学術講演会, Domestic conference
Mar. 2015 - GaAs中のエピタキシャル2次元窒素シート非局在電子状態の発光ダイナミクス
馬場 健; HARADA YUKIHIRO; KAIZU TOSHIYUKI; KITA TAKASHI
Poster presentation, Japanese, 第24回光物性研究会, Domestic conference
Dec. 2014 - Two-dimensional electronic states of epitaxial nitrogen atomic sheet in GaAs
Y. Harada; T. Baba; T. Kaizu; T. Kita
Invited oral presentation, English, International Symposium on Recent Progress of Photonic Devices and Materials, Invited, International conference
Nov. 2014 - Suppression of Thermal Carrier Escape and Efficient Photo-Carrier Generation by Two-Step Photon Absorption in Intermediate-Band Solar Cells Using a Dot-in-Well Structure
S. Asahi; H. Teranishi; N. Kasamatsu; T. Kada; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 6th World Conference on Photovoltaic Energy Conversion, Kyoto International Conference Center, International conference
Nov. 2014 - Photoluminescence Decay Dynamics in Epitaxial Two-Dimensional Nitrogen Atomic Sheet in GaAs
T. Baba; HARADA YUKIHIRO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, International Symposium on Recent Progress of Photonic Devices and Materials, Kobe University, International conference
Nov. 2014 - Modulation of Photoluminescence Properties of InAs Quantum Dots on Nitrogen δ-Doped GaAs
KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, International Symposium on Recent Progress of Photonic Devices and Materials, Kobe University, International conference
Nov. 2014 - Photoluminescence Properties of InAs Quantum Dots on Nitrogen δ-Doped GaAs
KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, Eleventh International Conference on Flow Dynamics, Sendai, International conference
Oct. 2014 - GaAs中のエピタキシャル二次元窒素膜の電子状態 (II)
HARADA YUKIHIRO; 馬場 健; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, Japanese, 第75回応用物理学会学術講演会, Domestic conference
Sep. 2014 - GaAs中のエピタキシャル二次元窒素膜における発光ダイナミクス
馬場 健; HARADA YUKIHIRO; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, Japanese, 第75回応用物理学会学術講演会, Domestic conference
Sep. 2014 - Enhancement of interaction among nitrogen pair centers in epitaxial two-dimensional nitrogen atomic sheet in GaAs
T. Baba; Y. Harada; T. Kaizu; T. Kita
Poster presentation, Japanese, 33rd Electronic Materials Symposium, Domestic conference
Jul. 2014 - Structural Modification of InAs Quantum Dots Grown on Nitrided GaAs(001)Surface
KAIZU TOSHIYUKI; K. Taguchi; KITA TAKASHI
Poster presentation, English, 8th International Conference on Quantum Dots, Pisa, International conference
May 2014 - 窒素δドープGaAs(001)層上のInAs量子ドット自己形成
KAIZU TOSHIYUKI; 田口 航平; KITA TAKASHI
Oral presentation, Japanese, 第61回応用物理学会春季学術講演会, 応用物理学会, 神奈川, Domestic conference
Mar. 2014 - InAs/GaAs量子ドット太陽電池の量子準位を介した２段階光吸収
加田 智之; 朝日 重雄; KAIZU TOSHIYUKI; KITA TAKASHI; 玉置 亮; 宮野 健次郎; 岡田 至崇
Oral presentation, Japanese, 第61回応用物理学会春季学術講演会, 応用物理学会, 神奈川, Domestic conference
Mar. 2014 - InAs/AlxGa1-xAs量子ドットにおけるキャリアの熱活性特性
朝日 重雄; 寺西 陽之; 笠松 直史; 加田 智之; KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, Japanese, 第61回応用物理学会春季学術講演会, 応用物理学会, 神奈川, Domestic conference
Mar. 2014 - Fabrication of InAs Quantum Dots on Nitrided GaAs (001) Surface
KAIZU TOSHIYUKI; KITA TAKASHI
Oral presentation, English, 10th International Conference on Flow Dynamics, Sendai International Center, International conference
Nov. 2013 - Photoluminescence Properties of Height-controlled GaAs Nanodisks Fabricated by Neutral Beam Etching
KAIZU TOSHIYUKI; Y. Tamura; M. Igarashi; W. Hu; C. Thomas; S. Samukawa; Y. Okada
Poster presentation, English, 40th International Symposium on Compound Semiconductors, Kobe, International conference
May 2013 - 中性粒子ビームエッチングにより作製したGaAsナノディスクのPL特性のディスク高さ依存性
KAIZU TOSHIYUKI; 田村 洋典; 五十嵐 誠; トーマス セドリック; 胡 衛国; 寒川 誠二; 岡田 至崇
Poster presentation, Japanese, 第60回応用物理学会春季学術講演会, 応用物理学会, 神奈川, Domestic conference
Mar. 2013 - トップダウン加工GaAsナノディスクにおけるキャリアスピン緩和
木場 隆之; 須崎 健太; 田村 洋典; 五十嵐 誠; セドリック トーマス; 胡 衛国; KAIZU TOSHIYUKI; 岡田 至崇; 寒川 誠二; 村山 明宏
Oral presentation, Japanese, 第60回応用物理学会春季学術講演会, 応用物理学会, 神奈川, Domestic conference
Mar. 2013 - 単層InAs/GaAs量子ドット構造のDLTS評価
中野 廣一; KAIZU TOSHIYUKI; 星井 拓也; 岡田至崇
Oral presentation, Japanese, 秋季第73回応用物理学会学術講演会, 応用物理学会, 愛媛, Domestic conference
Sep. 2012 - 原子状水素援用MBEによる2次元GaAsナノディスクアレイのGaAs/AlGaAsキャップ層再成長
KAIZU TOSHIYUKI; 田村 洋典; 五十嵐 誠; 胡 衛国; 寒川 誠二; 岡田 至崇
Oral presentation, Japanese, 秋季第73回応用物理学会学術講演会, 応用物理学会, 愛媛, Domestic conference
Sep. 2012 - バイオテンプレート極限加工によるGaAsナノディスクの作製と発光特性
田村 洋典; 五十嵐 誠; トーマス セドリック; モハマド エルマン ファウジ; 胡 衛国; 塚本 里加子; KAIZU TOSHIYUKI; 星井 拓也; 木場 隆之; 山下 一郎; 岡田 至崇; 村山 明宏; 寒川 誠二
Oral presentation, Japanese, 秋季第73回応用物理学会学術講演会, 応用物理学会, 愛媛, Domestic conference
Sep. 2012 - Observation of photo- luminescence from 2-dimentional GaAs nanodisk array regrown by atomic hydrogen-assisted molecular beam epitaxy
KAIZU TOSHIYUKI; Y. Tamura; M. Igarashi; W. Hu; R. Tsukamoto; I. Yamashita; S. Samukawa; Y. Okada
Oral presentation, English, 17th International Conference on Molecular Beam Epitaxy, Nara, International conference
Sep. 2012 - 2次元Siナノディスクアレイにおけるミニバンド形成と電気伝導性の向上
モハマド エルマン ファウジ; 五十嵐 誠; 胡 衛国; KAIZU TOSHIYUKI; 岡田 至崇; 寒川 誠二
Oral presentation, Japanese, 秋季第73回応用物理学学術講演会, 応用物理学, 愛媛, Domestic conference
Sep. 2012 - High-density and Sub-20-nm GaAs Nanodisk Array Fabricated Using Neutral Beam Etching Process for High Performance QDs Devices
Y. Tamura; M. Igarashi; M. E. Fauzi; R. Tsukamoto; KAIZU TOSHIYUKI; T. Kiba; I. Yamashita; Y. Okada; A. Murayama; S. Samukawa
Oral presentation, English, 12th International Conference on Nanotechnology, United Kingdom, International conference
Aug. 2012 - バイオテンプレート極限加工によるGaAs 量子ナノディスク構造の制御
田村 洋典; 五十嵐 誠; モハマド エルマン ファウジ; 胡 衛国; KAIZU TOSHIYUKI; 岡田 至崇; 寒川 誠二
Oral presentation, Japanese, 春季第59回応用物理学会関係連合講演会, 応用物理学会, 東京, Domestic conference
Mar. 2012 - 障壁材料としてSiCを用いたSi量子ナノディスクアレイ構造の電気・光学特性
五十嵐 誠; KAIZU TOSHIYUKI; 岡田 至崇; 木場 隆之; 村山 明宏; 寒川 誠二
Oral presentation, Japanese, 秋季第72回応用物理学会学術講演会, 応用物理学会, 山形, Domestic conference
Sep. 2011 - Fabrication of Two-dimensional Array of Sub-10nm GaAs Nanodisk by Combination of Bio-template and Neutral Beam Etching
林 士弘; 王 宣又; 黄 啓賢; 塚本 里加子; KAIZU TOSHIYUKI; 五十嵐 誠; 岡田 至崇; 寒川誠二
Oral presentation, Japanese, 秋季第72回応用物理学会学術講演会, 応用物理学会, 山形, Domestic conference
Sep. 2011 - Optical Absorption, Photo-Luminescence and Miniband Formation of a Highly Ordered and Dense 2-Dimensional Array of Si Nanodisks for Quantum Dot Solar Cells
M. Igarashi; C.H. Huang; X. Y. Wang; M. F. Budiman; Y. Tamura; T. Kiba; A. Murayama; KAIZU Toshiyuki; Y. Okada; S. Samukawa
Oral presentation, English, 37th IEEE Photovoltaic Specialists Conference, Seattle, International conference
Jun. 2011 - Damage-free Top-down Processes of Fabricating Two-dimensional Array of Sub-10nm Nanometer GaAs Nanodisks using Bio-template and Neutral Beam Etching for Intermediate Band Solar Cell Applications
X. Y. Wang; C. H. Huang; R. Tsukamoto; KAIZU Toshiyuki; M. Igarashi; P. A. Mortemousque; H. Shinohara; Y. Okada; A. Murayama; K. Itoh; Y. Ohno; I. Yamashita; S. Samukawa
Oral presentation, English, 37th IEEE Photovoltaic Specialists Conference, Seattle, International conference
Jun. 2011 - 高密度InAs量子ドットのSb照射成長中断における時間分解X線回折測定(3)
山本 和輝; 角田 直輝; KAIZU TOSHIYUKI; 高橋 正光; 藤川 誠司; 山口 浩一
Oral presentation, Japanese, 秋季第71回応用物理学会学術講演会, 応用物理学会, 長崎, Domestic conference
Sep. 2010 - シリコン(Si)ナノディスク2次元アレイによる高効率光吸収とバンドギャップエネルギー制御の実現
ブディマン モハマド; ファイルズ; 黄 啓賢; 王 宣又; KAIZU TOSHIYUKI; 五十嵐 誠; 大島 隆治; 岡田 至崇; 山下 一郎; 寒川 誠二
Oral presentation, Japanese, 秋季第71回応用物理学会学術講演会, 応用物理学会, 長崎, Domestic conference
Sep. 2010 - 高密度InAs量子ドットのSb照射成長中断における時間分解X線回折測定(2)
角田 直輝; KAIZU TOSHIYUKI; 高橋 正光; 藤川 誠司; 山口 浩一
Oral presentation, Japanese, 秋季第70回応用物理学会学術講演会, 応用物理学会, 富山, Domestic conference
Sep. 2009 - Ybドープ2次元電子系におけるYbトラップ準位の考察
KAIZU TOSHIYUKI; 高増 正; 竹端 寛治; 今中 康貴
Oral presentation, Japanese, 日本物理学会第64回秋季大会, 日本物理学会, 東京, Domestic conference
Sep. 2009 - Real-time X-ray diffraction measurements during Sb-mediated SK growth and annealing of InAs quantum dots
KAIZU Toshiyuki; N. Kakuda; M. Takahasi; S.Fujikawa; K. Yamaguchi
Poster presentation, English, 14th International Conference on Modulated Semiconductor Structures, Kobe, International conference
Jul. 2009 - Magnetotransport properties of Ytterbium doped AlxGa1-xAs/GaAs two-dimensional electron system
KAIZU Toshiyuki; Y. Imanaka; K. Takehana; T. Takamasu
Poster presentation, English, 18th International Conference on Electronic Properties of Two-Dimensional Systems, Kobe, International conference
Jul. 2009
Research Themes
- Realization of integrated high sensitivity electric field sensor using quantum dot superlattice
和田 修; 小島 磨; 海津 利行; 原田 幸弘; 南 康夫
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Kobe University, Grant-in-Aid for Scientific Research (C), Coinvestigator, 本研究では外部の電界を量子ドット（QD）超格子構造に印加し、これを含む共振器構造を透過する光信号の変調成分をとらえることにより、電界を高感度に検出するセンサの実現を目指す。本年度は、量子効果の導入による電気光学係数自体の増大効果、および光共振器構造による光子の長寿命化による電気光学効果の増強効果、の二つの効果に焦点を合わせて研究を進めた。 QD超格子構造の電気光学係数の評価を行うための導波路素子の準備と電気光学係数評価光学系の検討を進めるとともに、光共振器構造の基本設計理論の構築に重点 をおいて研究を行い、以下のような成果を得た。
QD超格子構造を含む導波路素子については、暗電流や逆方向電圧印加特性など基本的特性を測定して光学測定への適用性を確かめた。また電気光学係数の計測光学系については、光信号偏光特性計測の精度を十分に高めるための光学系の新たな設計を行って部品選定を完了し、次年度の高精度測定系の構築の見通しを得た。
光共振器構造の設計においては、共振器のQ値増大による光子寿命の延長に起因する電気光学効果の増強と、Q値の増大に伴う透過光出力の減衰との間に生ずるトレードオフ関係を考慮しながら共振器構造の最適化を行うことが必要である。本年度は基本設計理論を構築することを目指して、多層膜構造の光学特性マトリクスを用いた計算アルゴリズムを考案し、外部電界の印加による透過光信号の位相変調信号の算定が可能であることを確認できたことにより、この計算方法が最適化探索に活用できることが分かった。, 22K04218
Apr. 2022 - Mar. 2025 - 窒素デルタドープによるGaAs基板上InAs量子ドット発光の1.5μm帯長波長化
海津 利行
学術研究助成基金助成金／基盤研究(C), Principal investigator
Apr. 2017 - Mar. 2020
