epitaxial lift-off

semiconductor device

dilute nitride semiconductor

optical property

compound semiconductor

solar cell

molecular beam epitaxy

crystal growth

Nanotechnology/Materials, Crystal engineering

Manufacturing technology (mechanical, electrical/electronic, chemical engineering), Electric/electronic material engineering

Apr. 2022 - Present
The University of Electro-Communications, Graduate School of Informatics and Engineering Department of Engineering Science, Associate Professor

May 2019 - Mar. 2022
The University of Tokyo, Research Center for Advanced Science and Technology (RCAST), Project Lecturer

Apr. 2013 - Apr. 2019
The University of Tokyo, Research Center for Advanced Science and Technology (RCAST), Project Assistant Professor

Apr. 2010 - Mar. 2013
The University of Tokyo, Research Center for Advanced Science and Technology (RCAST), Project Researcher

2025
プログラム委員, 第22回「次世代の太陽光発電システム」シンポジウム（第5回日本太陽光発電学会学術講演会）

May 2021 - Mar. 2023
PVSEC-33 program committee, PVSEC-33, Society

Nov. 2022
Guest Editor, JJAP特集号編集委員会, Society

Oct. 2012
第三回薄膜太陽電池セミナー
ポスター賞（筆頭）, 宮下 直也

Jun. 2006
IEEE 4th World Conference on Photovoltaic Energy Conversioin (WCPEC-4)
Outstanding Poster Award (筆頭), 宮下 直也

Complex index of refraction of MBE grown 1 eV GaInAsNSb dilute nitride layers as a function of thermal annealing
M. Gabás; E. Blanco; I. Lombardero; P.F. Palacios; I. García; N. Miyashita; Y. Okada; M. Domínguez; C. Algora
Optical Materials, Elsevier BV, 163, 116960-116960, Jun. 2025, Peer-reviwed
Scientific journal

Abnormal photoluminescence properties of InAs/InAsSb in-plane ultrahigh-density quantum dots
Sim Jui Oon; Takumi Ohyama; Naoya Miyashita; Koichi Yamaguchi
Japanese Journal of Applied Physics, IOP Publishing, 63, 8, 085501-085501, 01 Aug. 2024, Peer-reviwed, Abstract

InAs/InAsSb ultrahigh-density quantum dots (UHD QDs) with a density of were fabricated using MBE, and their photoluminescence (PL) properties were characterized. Through temperature dependences of PL energy, intensity and decay time of UHD QDs, it was found that in-plane strong coupling between adjacent QDs of excited and ground states due to homogeneous broadening of QD levels progressed above 60 K and above 100 K, respectively. The findings regarding the strong coupling at ground states were consistent with the temperature dependence of PL minimum energy outlined in appendix. In addition, abnormal phenomenon in PL full width at half maximum was attributed to the in-plane miniband formation resulting from strong coupling.
Scientific journal

Resonant tunneling injection of electrons through double stacked GaAs/InAs quantum dots with nanohole electrode
Yuji Nakazato; Naoya Miyashita; Koichi Yamaguchi
Japanese Journal of Applied Physics, IOP Publishing, 62, 112005, 24 Oct. 2023, Peer-reviwed, Abstract

Resonant tunneling diodes containing closely double-stacked InAs quantum dots (QDs) were grown on GaAs substrates by molecular beam epitaxy. After growing a thin GaAs capping layer on the double-stacked InAs QDs, nanoholes were selectively formed just above the larger second QDs by thermal annealing. The Au thin film was deposited directly on top surface of the larger second QDs through the nanoholes. The second QDs contacted with Au film served as conducting dots, which can locally inject electrons into the underlying first QDs. In current versus voltage (I-V) measurements, (dI/dV) peaks were clearly observed in the forward bias voltage region. It was due to the tunneling current through a non-doped GaAs thin layer between double-stacked QDs and n-GaAs conduction band. The (dI/dV) peaks shifted toward the lower forward voltage region with increasing temperature. It was explained by the temperature dependence of the electron energy distribution in the GaAs conduction band.
Scientific journal

High-density and high-uniformity InAs quantum nanowires on Si(111) substrates
Ryusuke Nakagawa; Rikuta Watanabe; Naoya Miyashita; Koichi Yamaguchi
Journal of Applied Physics, AIP Publishing, 134, 15, 154302, 18 Oct. 2023, Peer-reviwed, InAs nanowires (NWs) were grown on SiOx pinholes formed on Si(111) substrates by molecular beam epitaxy. Influences of electron-beam (EB) irradiation on the SiOx layer on the pinhole formation and the subsequent InAs NW growth were studied. As the EB irradiation dose increased, the pinhole density in the SiOx layer decreased. From atomic force microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy results, it was found that the pinhole etching of the SiOx layer by Ga droplets was suppressed by carbon adsorption due to the EB irradiation. By forming high-density pinholes on the SiOx layer without the EB irradiation, high-density InAs NWs with 1–2 × 1010 cm−2 were grown successfully, and the uniformity in the NW diameter improved. The standard deviation of the NW diameter was 1.8 nm (8.8%) for high-density NWs. In addition, the NW diameter decreased with decreasing EB dose, and the NW diameter was controlled by adjusting the diameter of Ga droplets forming the pinholes. As the NW diameter decreased, photoluminescence spectra of the NWs shifted to higher energies than the bandgap energy of the wurtzite InAs bulk. From these results, we successfully fabricated high-density and high-uniformity InAs NWs with quantum size effects on EB-unirradiated SiOx/Si(111).
Scientific journal

Inverse design of intermediate band solar cell via a joint drift-diffusion simulator and deep reinforcement learning scheme
Kodai Shiba; Naoya Miyashita; Yoshitaka Okada; Tomah Sogabe
Japanese Journal of Applied Physics, 62, SK1046, May 2023, Peer-reviwed
Scientific journal, English

High-efficiency InAs/GaAs quantum dot intermediate band solar cell achieved through current constraint engineering
Tomah Sogabe; Yasushi Shoji; Naoya Miyashita; Daniel J. Farrell; Kodai Shiba; Hwen-Fen Hong; Yoshitaka Okada
Next Materials, 1, 100013, Apr. 2023, Peer-reviwed
Scientific journal, English

Ultrafast inverse design of quantum dot optical spectra via a joint TD-DFT learning scheme and deep reinforcement learning
Hibiki Yoshida; Katsuyoshi Sakamoto; Naoya Miyashita; Koichi Yamaguchi; Qing Shen; Yoshitaka Okada; Tomah Sogabe
AIP Advances, 12, 11, 115316-115316, Nov. 2022, Peer-reviwed
Scientific journal, English

Improvement of III-V dilute nitride thin films for solar cell application: Effect of antimony doping
N. AHSAN; N. MIYASHITA; K. M. Yu; W. WALUKIEWICZ; Y. OKADA
International Journal of the Society of Materials Engineering for Resources, The Society of Materials Engineering for Resources of Japan, 25, 2, 157-167, 31 Oct. 2022, Peer-reviwed
Scientific journal

Dependence of the radiative lifetime on the type-II band offset in GaAs_xSb_1−x/GaAs quantum dots including effects of photoexcited carriers
Yusuke Oteki; Yasushi Shoji; Naoya Miyashita; Yoshitaka Okada
Journal of Applied Physics, AIP Publishing, 132, 13, 134402-134402, 07 Oct. 2022, Peer-reviwed, In quantum dot (QD) heterostructures that have a type-II band alignment, either the electron or the hole is confined inside the QD. Due to smaller electron–hole overlap in such structures, relatively long radiative lifetimes can be realized, which is beneficial for devices such as intermediate-band solar cells. The use of GaAs_xSb_{1− x}/GaAs QDs allows us to control the energy level of the confined state by changing the type-II conduction-band offset (CBO) without the need of changing the QD size. However, the dependence of the radiative lifetime τr on the CBO needs to be considered to achieve optimum device performance. In this work, GaAs_xSb_{1− x}/GaAs QDs were grown by molecular beam epitaxy. The amount of deposition was controlled to obtain QDs with approximately the same size even for different values of As composition x, and the carrier lifetime was determined by time-resolved photoluminescence measurements. Since the CBO becomes smaller for larger values of x, a simple model would predict a larger electron–hole overlap for larger x values, and thus, the lifetime should decrease monotonically. However, the experimentally obtained lifetime does not decrease monotonically, which has interesting implications for applications. We explain the observed trend by the effect of photoexcited carriers; a triangular potential well is formed around the QDs in the case of high excitation densities, and thus, electrons are localized near the QDs. We also calculated τr considering the effect of photoexcited carriers to confirm our model, and a similar tendency was obtained.
Scientific journal

Demonstration of in-plane miniband formation in InAs/InAsSb ultrahigh-density quantum dots by analysis of temperature dependence of photoluminescence
Sho Tatsugi; Naoya Miyashita; Tomah Sogabe; Koichi Yamaguchi
Japanese Journal of Applied Physics, IOP Publishing, 61, 10, 102009-102009, Oct. 2022, Peer-reviwed, Abstract

Self-assembled InAs/InAsSb ultrahigh-density quantum dots (UHD QDs) were grown on GaAs(001) substrate by molecular beam epitaxy. The QD density was 1 × 10¹² cm⁻², and an average separation distance between adjacent QD edges was less than 3 nm. The temperature dependence of photoluminescence (PL) minimum energy of UHD QDs was measured and was divided clearly into three temperature regions: (1) fitting to upper Varshni shift at 15–80 K, (2) decreasing from upper Varshni shift from 80–180 K and (3) re-fitting to lower Varshni shift at 180–290 K. The energy difference between upper and lower Varshni curves increased with increasing QD density. This anomalous temperature dependence of PL minimum energy was demonstrated by a simulation model of miniband formation due to electronically strong coupling of adjacent QDs, including the temperature dependence of the homogeneous broadening in the QD.
Scientific journal

Enhanced current generation in quantum-dot intermediate band solar cells through optimizing the position of quantum dot layers
Yusuke Oteki; Naoya Miyashita; Maxime Giteau; Kodai Shiba; Tomah Sogabe; Yoshitaka Okada
Optical Materials: X, Elsevier BV, 16, 100207-100207, Oct. 2022, Peer-reviwed
Scientific journal

Co-deposition of MoS₂ films by reactive sputtering and formation of tree-like structures
Myeongok Kim; Maxime Giteau; Nazmul Ahsan; Naoya Miyashita; Logu Thirumalaisamy; Chen Chen; Joan M Redwing; Yoshitaka Okada
Nanotechnology, IOP Publishing, 33, 34, 345708-345708, 20 Aug. 2022, Peer-reviwed, Abstract

Transition metal dichalcogenides are versatile layered materials with potential applications ranging from optoelectronic devices to water splitting. Top-down fabrication methods such as exfoliation are not practical for a large-scale production of high-quality devices: a bottom-up approach such as sputtering, a low-temperature deposition method, is more suitable. However, due to its anisotropic nature, the growth mechanism of molybdenum disulfide (MoS₂) via sputtering is complex and remains to be investigated in detail. In this paper, we study the growth of MoS₂ films co-deposited by using a sulfur (S) hot-lip cell and a molybdenum (Mo) sputtering target via reactive sputtering. The impact of S partial pressure on the structure and morphology of MoS₂ films was systematically characterized, and it was observed that the growth is dominated by vertically-oriented sheets with horizontal branches, resulting in a tree-like structure. The growth front of the structures is ascribed to the anisotropic incorporation of adatoms with regards to the orientation of MoS₂.
Scientific journal

Self-formation of InAs/InGaAsSb type-II superlattice structures on InP substrates by MBE and their application to mid-infrared LEDs
Kou Uno; Naoto Iijima; Naoya Miyashita; Koichi Yamaguchi
AIP Advances, AIP Publishing, 12, 8, 085301-085301, 01 Aug. 2022, Peer-reviwed, InAs/InGaAsSb type-II superlattice structures (SLSs) were spontaneously formed by the molecular beam epitaxy of InAs/GaAs_0.86Sb_0.14 SLSs on InP substrates. The strain due to lattice mismatch between InAs and GaAs_0.86Sb_0.14 induced two exchange reactions of In–Ga and As–Sb at both InAs/GaAs_0.86Sb_0.14 heterointerfaces, resulting in the strain relaxation and the self-formation of InAs/InGaAsSb type-II SLS. By energy dispersive x-ray spectroscopy analysis, the mixed crystal composition of the InGaAsSb layer was determined to be approximately In_0.8Ga_0.2As_0.9Sb_0.1. Electroluminescence spectra of LEDs, including the self-formed InAs/In_0.8Ga_0.2As_0.9Sb_0.1 2.5-periodic SLS, showed double peaks of 2.6 and 3.2 µm at 15 K. The luminescence spectrum was based on two transition mechanisms of type-I transition in InAs and type-II transition between InAs and InGaAsSb. The experimental results of luminescence spectra were supported by theoretical calculations. The 3.3 µm emission was maintained above 220 K.
Scientific journal

Spectral Splitting Solar Cells Constructed with InGaP/GaAs Two-Junction Subcells and Infrared PbS Quantum Dot/ZnO Nanowire Subcells
Haibin Wang; Shoichiro Nakao; Naoya Miyashita; Yusuke Oteki; Maxime Giteau; Yoshitaka Okada; Tatsuya Takamoto; Hidenori Saito; Shinichi Magaino; Katsuhiko Takagi; Tetsuya Hasegawa; Takaya Kubo; Takumi Kinoshita; Jotaro Nakazaki; Hiroshi Segawa
ACS Energy Letters, American Chemical Society (ACS), 2477-2485, 08 Jul. 2022, Peer-reviwed
Scientific journal

Collection of photocarriers in intermediate band solar cells: experiments and equivalent circuit analysis
Nazmul Ahsan; Naoya Miyashita; Kin Man Yu; Wladek Walukiewicz; Yoshitaka Okada
Journal of Photonics for Energy, SPIE-Intl Soc Optical Eng, 12, 03, 032210, 01 Jul. 2022, Peer-reviwed
Scientific journal, English

Diffusion photocurrent influenced by intraband excitation in an intermediate band solar cell with type-I band alignment
Yaxing Zhu; Shigeo Asahi; Naoya Miyashita; Yoshitaka Okada; Takashi Kita
Japanese Journal of Applied Physics, IOP Publishing, 61, 7, 074002-074002, 01 Jul. 2022, Peer-reviwed, Abstract

We elucidate a photocarrier collection mechanism in intermediate band solar cells (IBSCs) with InAs-quantum dots (QDs)-in-an-Al_0.3Ga_0.7As/GaAs-quantum well structures. When the Al_0.3Ga_0.7As barrier is excited, the device electrical output can be varied by additional infrared light for the electron intraband optical transition in QDs. The photocurrent in IBSC with a single QDs-in-a-well structure shows a monotonic increase with the intraband-excitation density. Conversely, IBSC with a multilayered QDs-in-a-well structure exhibits a photocurrent reduction when electrons in QDs are optically pumped out. The simultaneously measured photoluminescence spectra proved that the polarity of QD states changes depending on the intraband-excitation density. We discuss the drift and diffusion current components and point out that the hole diffusion current is significantly influenced by carriers inside the confinement structure. Under strong intraband excitations, we consider an increased hole diffusion current occurs by blocking hole-capture in the quantum structures. This causes unexpected photocurrent reduction in the multilayered device.
Scientific journal

Resonant absorption for multilayer quantum well and quantum dot solar cells
Maxime Giteau; Yusuke Oteki; Kento Kitahara; Naoya Miyashita; Ryo Tamaki; Yoshitaka Okada
Journal of Photonics for Energy, 12, 2, 022203, Apr. 2022, Peer-reviwed
Scientific journal, English

Erratum: Two-photon photocurrent spectra of InAs quantum dot-in-well intermediated-band solar cells at room temperature (Journal of Applied Physics (2021) 130 (124505) DOI: 10.1063/5.0060569)
Yaxing Zhu; Shigeo Asahi; Naoya Miyashita; Yoshitaka Okada; Takashi Kita
Journal of Applied Physics, American Institute of Physics Inc., 130, 17, 07 Nov. 2021, Peer-reviwed
Scientific journal, English

Two-photon photocurrent spectra of InAs quantum dot-in-well intermediated-band solar cells at room temperature
Yaxing Zhu; Shigeo Asahi; Naoya Miyashita; Yoshitaka Okada; Takashi Kita
Journal of Applied Physics, AIP Publishing, 130, 12, 124505-124505, 28 Sep. 2021, Peer-reviwed
Scientific journal

Two-step excitation induced photovoltaic properties in an InAs quantum dot-in-well intermediate-band solar cell
Yaxing Zhu; Shigeo Asahi; Kohei Watanabe; Naoya Miyashita; Yoshitaka Okada; Takashi Kita
Journal of Applied Physics, AIP Publishing, 129, 7, 074503-074503, 21 Feb. 2021, Peer-reviwed
Scientific journal

Theoretical and experimental assessment of thinned germanium substrates for III–V multijunction solar cells
Iván Lombardero; Mario Ochoa; Naoya Miyashita; Yoshitaka Okada; Carlos Algora
Progress in Photovoltaics: Research and Applications, Wiley, 28, 11, 1097-1106, Nov. 2020, Peer-reviwed
Scientific journal

Effect of concentrated sunlight illumination on mobility and concentrator solar cell efficiency
Tomoki Harada; Naoya Miyashita; Tetsuo Ikari; Atsuhiko Fukuyama
Japanese Journal of Applied Physics, IOP Publishing, 59, 7, 071002-071002, 01 Jul. 2020, Peer-reviwed
Scientific journal

Fabrication and optical characterization of ultrathin III-V transferred heterostructures for hot-carrier absorbers
Maxime Giteau; Kentaroh Watanabe; Naoya Miyashita; Hassanet Sodabanlu; Fabien Atlan; Daniel Suchet; Stéphane Collin; Jean-François Guillemoles; Yoshitaka Okada
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IX, SPIE, 03 Mar. 2020, Peer-reviwed
International conference proceedings

Anneal mediated deep-level dynamics in GaInNAsSb dilute nitrides lattice-matched to GaAs
Naoya Miyashita; Yilun He; Nazmul Ahsan; Yoshitaka Okada
Lead, Journal of Applied Physics, 126, 14, 143104, 14 Oct. 2019, Peer-reviwed
Scientific journal, English

Effect of Annealing on The Bottom Cell in GaInP/GaAs/GaInNAsSb Triple Junction Solar Cells by MBE/MOCVD Hybrid Growth
Naoya Miyashita; Yilun He; Nazmul Ahsan; Yoshitaka Okada
2019 Compound Semiconductor Week (CSW), IEEE, May 2019
English

Inverted Lattice-Matched Triple Junction Solar Cells with 1.0 eV GaInNAsSb Subcell by MOCVD/MBE Hybrid Growth
Naoya Miyashita; Yilun He; Takaaki Agui; Hiroyuki Juso; Tatsuya Takamoto; Yoshitaka Okada
Lead, IEEE Journal of Photovoltaics, 9, 3, 666-672, May 2019, Peer-reviwed
Scientific journal, English

Epitaxial Lift-Off of Ultrathin Heterostructures for Hot-Carrier Solar Cell Applications
Maxime Giteau; Kentaroh Watanabe; Hassanet Sodabanlu; Naoya Miyashita; Masakazu Sugiyama; Andrea Cattoni; Stephane Collin; Jean-Francois Guillemoles; Yoshitaka Okada
2019 COMPOUND SEMICONDUCTOR WEEK (CSW), 2019
International conference proceedings, English

GaSb/GaAs quantum nanostructures for intermediate band solar cell under high sunlight concentration
Yusuke Oteki; Yasushi Shoji; Naoya Miyashita; Yilun He; Yoshitaka Okada
2019 COMPOUND SEMICONDUCTOR WEEK (CSW), 2019, Peer-reviwed
Scientific journal, English

Light absorption enhancement in ultra-thin layers for hot-carrier solar cells: first developments towards the experimental demonstration of an enhanced hot-carrier effect with light trapping
Maxime Giteau; Kentaroh Watanabe; Naoya Miyashita; Hassanet Sodabanlu; Julie Goffard; Amaury Delamarre; Daniel Suchet; Ryo Tamaki; Zacharie Jehl; Laurent Lombez; Masakazu Sugiyama; Andrea Cattoni; St?phane Collin; Jean-Fran?ois Guillemoles; Yoshitaka Okada
Proc. SPIE, 10913, 10913D, 2019, Peer-reviwed
International conference proceedings, English

Material challenges for solar cells in the twenty-first century: directions in emerging technologies
Samy Almosni; Amaury Delamarre; Zacharie Jehl; Daniel Suchet; Ludmila Cojocaru; Maxime Giteau; Benoit Behaghel; Anatole Julian; Camille Ibrahim; Léa Tatry; Haibin Wang; Takaya Kubo; Satoshi Uchida; Hiroshi Segawa; Naoya Miyashita; Ryo Tamaki; Yasushi Shoji; Katsuhisa Yoshida; Nazmul Ahsan; Kentaro Watanabe; Tomoyuki Inoue; Masakazu Sugiyama; Yoshiaki Nakano; Tomofumi Hamamura; Thierry Toupance; Céline Olivier; Sylvain Chambon; Laurence Vignau; Camille Geffroy; Eric Cloutet; Georges Hadziioannou; Nicolas Cavassilas; Pierre Rale; Andrea Cattoni; Stéphane Collin; François Gibelli; Myriam Paire; Laurent Lombez; Damien Aureau; Muriel Bouttemy; Arnaud Etcheberry; Yoshitaka Okada; Jean-François Guillemoles
Science and Technology of Advanced Materials, Taylor and Francis Ltd., 19, 1, 336-369, 31 Dec. 2018, Peer-reviwed
Scientific journal, English

Incorporation of hydrogen into MBE-grown dilute nitride GaInNAsSb layers in a MOCVD growth ambient
Naoya Miyashita; Yilun He; Nazmul Ahsan; Takaaki Agui; Hiroyuki Juso; Tatsuya Takamoto; Yoshitaka Okada
Lead, Solar Energy Materials and Solar Cells, Elsevier B.V., 185, 359-363, 01 Oct. 2018, Peer-reviwed
Scientific journal, English

Enhancement of photocurrent in epitaxial lift-off thin-film GaInNAsSb solar cells due to light-confinement structure
Naoya Miyashita; Benoît Behaghel; Jean-François Guillemoles; Yoshitaka Okada
Lead, Applied Physics Express, Japan Society of Applied Physics, 11, 7, 72301, 01 Jul. 2018, Peer-reviwed
Scientific journal, English

Characterization of InGaAs/GaAsN multiple quantum well with flat conduction band for improving carrier transport in multijuction solar cell
W. Yanwachirakul; N. Miyashita; H. Sodabanlu; K. Watanabe; Y. Okada; M. Sugiyama; Y. Nakano
Proceedings of SPIE - The International Society for Optical Engineering, SPIE, 10527, 10527E, 2018, Peer-reviwed
International conference proceedings, English

Thin-film multiple-quantum-well solar cells fabricated by epitaxial lift-off process
Tatsuya Nakata; Kentaroh Watanabe; Naoya Miyashita; Hassanet Sodabanlu; Maxime Giteau; Yoshiaki Nakano; Yoshitaka Okada; Masakazu Sugiyama
Japanese Journal of Applied Physics, 57, 8, 08RF03, 2018, Peer-reviwed
Scientific journal, English

N-H-related deep-level defects in dilute nitride semiconductor GaInNAs for four-junction solar cells
Yilun He; Naoya Miyashita; Yoshitaka Okada
Japanese Journal of Applied Physics, 57, 08RD11, 2018, Peer-reviwed
Scientific journal, English

Design of free-barrier InGaAs/GaNAs multiple quantum well solar cells with 1.2 eV energy gap
Warakorn Yanwachirakul; Naoya Miyashita; Hassanet Sodabanlu; Kentaroh Watanabe; Masakazu Sugiyama; Yoshitaka Okada; Yoshiaki Nakano
JAPANESE JOURNAL OF APPLIED PHYSICS, 56, 8, 08MA04, Aug. 2017, Peer-reviwed
Scientific journal, English

Effect of Si doping and sunlight concentration on the performance of InAs/GaAs quantum dot solar cells
Shunya Naito; Katsuhisa Yoshida; Naoya Miyashita; Ryo Tamaki; Takuya Hoshii; Yoshitaka Okada
JOURNAL OF PHOTONICS FOR ENERGY, 7, 2, 25505, Apr. 2017, Peer-reviwed
Scientific journal, English

Improvement of 1.0eV GaInNAsSb solar cell performance upon optimal annealing
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Lead, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 214, 3, 1600586, Mar. 2017, Peer-reviwed
Scientific journal, English

Multiband modification of III-V dilute nitrides for IBSC application
Nazmul Ahsan; Naoya Miyashita; Kin Man Yu; Wladek Walukiewicz; Yoshitaka Okada
PHYSICS, SIMULATION, AND PHOTONIC ENGINEERING OF PHOTOVOLTAIC DEVICES VI, 10099, 100990I, 2017, Peer-reviwed
International conference proceedings, English

Modeling and characterization of double resonant tunneling diodes for application as energy selective contacts in hot carrier solar cells
Zacharie Jehl; Daniel Suchet; Anatole Julian; Cyril Bernard; Naoya Miyashita; Francois Gibelli; Yoshitaka Okada; Jean-Francois Guillemoles
PHYSICS, SIMULATION, AND PHOTONIC ENGINEERING OF PHOTOVOLTAIC DEVICES VI, 10099, 100990N, 2017, Peer-reviwed
International conference proceedings, English

Characterization of Cr Doped CuGaS2 Thin Films Synthesized By Chemical Spray Pyrolysis
Nazmul Ahsan; Sivaperuman Kalainathan; Naoya Miyashita; Takuya Hoshii; Yoshitaka Okada
Mechanics, Materials Science and Engineering, 9, 380-387, 2017, Peer-reviwed
Scientific journal, English

Insights on energy selective contacts for thermal energy harvesting using double resonant tunneling contacts and numerical modeling
A. Julian; Z. Jehl; N. Miyashita; Y. Okada; J. -F. Guillemoles
SUPERLATTICES AND MICROSTRUCTURES, 100, 749-756, Dec. 2016, Peer-reviwed
Scientific journal, English

Growth of ErAs nanodots by molecular beam epitaxy for application to tunneling junctions in multijunction solar cells
Chao-Yu Hung; Tomah Sogabe; Naoya Miyashita; Yoshitaka Okada
JAPANESE JOURNAL OF APPLIED PHYSICS, 55, 2, 21201, Feb. 2016, Peer-reviwed
Scientific journal, English

Improvement of 1.0 eV GaInNAsSb solar cell performance upon annealing
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Lead, 2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS), 2016, Peer-reviwed
International conference proceedings, English

Generation and collection of photocarriers in dilute nitride GaInNAsSb solar cells
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Lead, PROGRESS IN PHOTOVOLTAICS, 24, 1, 28-37, Jan. 2016, Peer-reviwed
Scientific journal, English

Evaluation of concentrator photovoltaic properties of GaInNAsSb solar cells for multijunction solar cell applications
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Lead, JAPANESE JOURNAL OF APPLIED PHYSICS, 54, 8, 08KE06, Aug. 2015, Peer-reviwed
Scientific journal, English

Electron Barrier Engineering in a Thin-Film Intermediate-Band Solar Cell
Nazmul Ahsan; Naoya Miyashita; Kin Man Yu; Wladek Walukiewicz; Yoshitaka Okada
IEEE JOURNAL OF PHOTOVOLTAICS, 5, 3, 878-884, May 2015, Peer-reviwed
Scientific journal, English

Effect of antimony on the deep-level traps in GaInNAsSb thin films
Muhammad Monirul Islam; Naoya Miyashita; Nazmul Ahsan; Takeaki Sakurai; Katsuhiro Akimoto; Yoshitaka Okada
APPLIED PHYSICS LETTERS, 105, 11, 112103, Sep. 2014, Peer-reviwed
Scientific journal, English

Fabrication and characterization of GaAs tunnel diode and ErAs nanoparticles enhanced GaAs tunnel diode for multijunction solar cell
Tomah Sogabe; Yasushi Shoji; Mitsuyoshi Ohba; Naito Shunya; Naoya Miyashita; Chao-Yu Hung; Akio Ogura; Yoshitaka Okada
Journal of Management and Organization, Cambridge University Press, 1602, 3, 09 May 2014, Peer-reviwed
Scientific journal, English

Fabrication and characterization of GaAs tunnel diode and ErAs nanoparticles enhanced GaAs tunnel diode for multijunction solar cell
Tomah Sogabe; Yasushi Shoji; Mitsuyoshi Ohba; Naito Shunya; Naoya Miyashita; Chao-Yu Hung; Akio Ogura; Yoshitaka Okada
Materials Research Society Symposium Proceedings, Materials Research Society, 1602, January, 1-7, 2014, Peer-reviwed
International conference proceedings, English

Photocapacitance study of MBE grown GaInNAsSb thin film solar cells
Muhammad Monirul Islam; Naoya Miyashita; Nazmul Ahsan; Takeaki Sakurai; Katsuhiro Akimoto; Yoshitaka Okada
JOURNAL OF CRYSTAL GROWTH, 378, 57-60, Sep. 2013, Peer-reviwed
Scientific journal, English

Antimony mediated growth of high-density InAs quantum dots for photovoltaic cells
F. K. Tutu; J. Wu; P. Lam; M. Tang; N. Miyashita; Y. Okada; J. Wilson; R. Allison; H. Liu
APPLIED PHYSICS LETTERS, 103, 4, 43901, Jul. 2013, Peer-reviwed
Scientific journal, English

Effect of Sb on GaNAs Intermediate Band Solar Cells
Nazmul Ahsan; Naoya Miyashita; Muhammad Monirul Islam; Kin Man Yu; Wladek Walukiewicz; Yoshitaka Okada
IEEE JOURNAL OF PHOTOVOLTAICS, 3, 2, 730-736, Apr. 2013, Peer-reviwed
Scientific journal, English

Effect of antimony on uniform incorporation of nitrogen atoms in GaInNAs films for solar cell application
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Lead, SOLAR ENERGY MATERIALS AND SOLAR CELLS, 111, 127-132, Apr. 2013, Peer-reviwed
Scientific journal, English

InAs/GaAs quantum dot solar cell with an AlAs cap layer
F. K. Tutu; P. Lam; J. Wu; N. Miyashita; Y. Okada; K. -H. Lee; N. J. Ekins-Daukes; J. Wilson; H. Liu
APPLIED PHYSICS LETTERS, 102, 16, 163907, Apr. 2013, Peer-reviwed
Scientific journal, English

Defect study of molecular beam epitaxy grown undoped GaInNAsSb thin film using junction-capacitance spectroscopy
Muhammad Monirul Islam; Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Applied Physics Letters, 102, 7, 74104, 18 Feb. 2013, Peer-reviwed
Scientific journal, English

Composition control of quinary GaInNAsSb alloy grown by molecular beam epitaxy
Naoya Miyashita; Nazmul Ahsan; Muhammad Monirul Islam; Yoshitaka Okada
Lead, PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 10, NO 11, 10, 11, 1369-1372, 2013, Peer-reviwed
International conference proceedings, English

Effect of Sb on GaNAs Intermediate Band Solar Cells
Nazmul Ahsan; Naoya Miyashita; Muhammad M. Islam; Kin Man Yu; Wladek Walukiewicz; Yoshitaka Okada
2012 IEEE 38TH PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), VOL 2, 3, 730, 2013, Peer-reviwed
International conference proceedings, English

Identification of defect types in moderately Si-doped GaInNAsSb layer in p-GaAs/n- GaInNAsSb/n-GaAs solar cell structure using admittance spectroscopy
Muhammad Monirul Islam; Naoya Miyashita; Nazmul Ahsan; Takeaki Sakurai; Katsuhiro Akimoto; Yoshitaka Okada
JOURNAL OF APPLIED PHYSICS, 112, 11, 114910, Dec. 2012, Peer-reviwed
Scientific journal, English

High electron mobility in Ga(In)NAs films grown by molecular beam epitaxy
Naoya Miyashita; Nazmul Ahsan; Makoto Inagaki; Muhammad Monirul Islam; Masafumi Yamaguchi; Yoshitaka Okada
Lead, APPLIED PHYSICS LETTERS, 101, 22, 222112, Nov. 2012, Peer-reviwed
Scientific journal, English

Extremely long carrier lifetime at intermediate states in wall-inserted type II quantum dot absorbers
Daisuke Sato; Junya Ota; Kazutaka Nishikawa; Yasuhiko Takeda; Naoya Miyashita; Yoshitaka Okada
JOURNAL OF APPLIED PHYSICS, 112, 9, 94305, Nov. 2012, Peer-reviwed
Scientific journal, English

Two-photon excitation in an intermediate band solar cell structure
Nazmul Ahsan; Naoya Miyashita; Muhammad Monirul Islam; Kin Man Yu; Wladek Walukiewicz; Yoshitaka Okada
APPLIED PHYSICS LETTERS, 100, 17, 172111, Apr. 2012, Peer-reviwed
Scientific journal, English

Extremely long carrier lifetime over 200 ns in GaAs wall-inserted type II InAs quantum dots
Kazutaka Nishikawa; Yasuhiko Takeda; Tomoyoshi Motohiro; Daisuke Sato; Junya Ota; Naoya Miyashita; Yoshitaka Okada
APPLIED PHYSICS LETTERS, 100, 11, 113105, Mar. 2012, Peer-reviwed
Scientific journal, English

Over 100 ns intrinsic radiative recombination lifetime in type II InAs/GaAs1-xSbx quantum dots
Kazutaka Nishikawa; Yasuhiko Takeda; Ken-ichi Yamanaka; Tomoyoshi Motohiro; Daisuke Sato; Junya Ota; Naoya Miyashita; Yoshitaka Okada
JOURNAL OF APPLIED PHYSICS, 111, 4, 44325, Feb. 2012, Peer-reviwed
Scientific journal, English

Transmission electron microscopy study of GaInNAs(Sb) thin films grown by atomic hydrogen-assisted molecular beam epitaxy
R. Oshima; J. Y. Huang; N. Miyashita; K. Matsubara; Y. Okada; F. A. Ponce
APPLIED PHYSICS LETTERS, 99, 19, 191907, Nov. 2011, Peer-reviwed
Scientific journal, English

Improvement of GaInNAsSb films fabricated by atomic hydrogen-assisted molecular beam epitaxy
Naoya Miyashita; Shuhei Ichikawa; Yoshitaka Okada
Lead, JOURNAL OF CRYSTAL GROWTH, 311, 12, 3249-3251, Jun. 2009, Peer-reviwed
Scientific journal, English

Carrier mobility characteristics in GaInNAs dilute nitride films grown by atomic hydrogen-assisted molecular beam epitaxy
Naoya Miyashita; Yukiko Shimizu; Yoshitaka Okada
Lead, JOURNAL OF APPLIED PHYSICS, 102, 4, 44904, Aug. 2007, Peer-reviwed
Scientific journal, English

Effect of growth temperature on the properties of Ga(In)NAs thin films by atomic hydrogen-assisted RF-MBE
Yukiko Shimizu; Naoya Miyashita; Yusuke Mura; Akira Uedono; Yoshitaka Okada
JOURNAL OF CRYSTAL GROWTH, 301, 579-582, Apr. 2007, Peer-reviwed
Scientific journal, English

Optimization of Ga(In)NAs thin film growth by atomic hydrogen-assisted molecular beam epitaxy
Shimizu Yukiko; Miyashita Naoya; Okada Yoshitaka
PROGRESS IN SEMICONDUCTOR MATERIALS V-NOVEL MATERIALS AND ELECTRONIC AND OPTOELECTRONIC APPLICATIONS, 891, 509-+, 2006, Peer-reviwed
Scientific journal, English

Light trapping and absorption enhancement in thin-film quantum dot solar cells
Kitahara Kento; Oteki Yusuke; Miyashita Naoya; Okada Yoshitaka
The Japan Photovoltaic Society, 24 Jun. 2022, Proceedings of the Annual Meeting of the Japan Photovoltaic Society, 2, 29-29, Japanese, 2436-6498

Optimizing the positions of quantum dot layers to increase the light absorption in quantum dot solar cells with light trapping structure
Yusuke Oteki; Maxime Giteau; Kei Fukushima; Kento Kitahara; Naoya Miyashita; Ryo Tamaki; Yoshitaka Okada
2022, 6TH IEEE ELECTRON DEVICES TECHNOLOGY AND MANUFACTURING CONFERENCE (EDTM 2022), 44-46, English, WOS:000852566800013

Optimizing the quantum dot layer position for increasing absorption of intermediate band solar cells
Oteki Y.; Giteau M.; Fukushima K.; Kitahara K.; Miyashita N.; Tamaki R.; Okada Y.
The Japan Photovoltaic Society, 12 Oct. 2021, Proceedings of the Annual Meeting of the Japan Photovoltaic Society, 1, 116-116, Japanese, 2436-6498

Enhancement of the light absorption rate of quantum dot solar cells by Fabry-Pérot resonance
Oteki Yusuke; Giteau Maxime; Fukushima Kei; Kei Kitahara; Naoya Miyashita; Ryo Tamaki; Yoshitaka Okada
The Japan Society of Applied Physics, 26 Feb. 2021, JSAP Annual Meetings Extended Abstracts, 2021.1, 2382-2382, Japanese, 2436-7613

Extending carrier lifetime by controlling the composition of GaAs_xSb_1-x/GaAs quantum dots
Oteki Yusuke; Shoji Yasushi; Miyashita Naoya; Okada Yoshitaka
The Japan Society of Applied Physics, 28 Feb. 2020, JSAP Annual Meetings Extended Abstracts, 2020.1, 2926-2926, Japanese, 2436-7613

Growth rate dependency of GaAsSb / GaAs Quantum Dots
Oteki Yusuke; Shoji Yasushi; Miyashita Naoya; Okada Yoshitaka
The Japan Society of Applied Physics, 04 Sep. 2019, JSAP Annual Meetings Extended Abstracts, 2019.2, 3430-3430, Japanese, 2436-7613

Epitaxial Lifted-Off Thin Film GaInP/GaAs/GaInNAsSb Lattice-Matched Triple Junction Solar Cells
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada; Rao Tatavarti; Andree Wibowo; Noren Pan
2019, Proc. The 46th IEEE Photovoltaic Specialists Conference, English, Introduction international proceedings

High-Effciency InAs-InGaAs Quantum Dash Solar Cells Developed Through Current Constraint Engineering
Yoshitaka Okada; Naoya Miyashita; Yusuke Oteki; Yasushi Shoji
2019, Proc. The 46th IEEE Photovoltaic Specialists Conference, 765-767, English, Introduction international proceedings, 0160-8371, WOS:000542034900157

Thinned Germanium Substrates for III-V Multijunction Solar Cells
Iv?n Lombardero; Naoya Miyashita; Mario Ochoa; Yoshitaka Okada; Carlos Alogra
2019, Proc. The 46th IEEE Photovoltaic Specialists Conference, English, Introduction international proceedings

Growth of InGaAs: N delta-doped superlattices for multi-junction solar cells
Umeda, Shumpei; Yagi, Shuhei; Miyashita, Naoya; Okada, Yoshitaka; Yaguchi, Hiroyuki
2018, 2018 IEEE 7TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION (WCPEC) (A JOINT CONFERENCE OF 45TH IEEE PVSC, 28TH PVSEC & 34TH EU PVSEC), 1861-1864, English, Introduction international proceedings, 2159-2330, 2159-2349, WOS:000469200401194

Hot Carrier Extraction Using Energy Selective Contacts and Feedback on the Remaining Distribution
Zacharie Jehl; Daniel Suchet; Naoya Miyashita; Benoit Behagel; Maxime Giteau; Amaury Delamarre; Bernice Mae; F. Yu Jeco; Jean-Francois Guillemoles; Yoshitaka Okada
2018, Proc. The 7th World Conference on Photovoltaic Energy Conversion, pp.1814-1816, English, Introduction international proceedings

Carrier Collection Improvement In InGaAs/GaAsN Multiple Quantum Well Solar Cell With Flat Conduction Band
Warakorn Yanwachirakul; Naoya Miyashita; Hassanet Sodabanlu; Kentaroh Watanabe; Masakazu Sugiyama; Yoshitaka Okada; Yoshiaki Nakano
2018, Proc. The 7th World Conference on Photovoltaic Energy Conversion, pp.1874-1877, English, Introduction international proceedings, 85059906214

Analysis And Control Of Deep-Level Defects In Dilute Nitride Semiconductor GaInNAsSb
Yilun He; Naoya Miyashita; Yoshitaka Okada
2018, Proc. The 7th World Conference on Photovoltaic Energy Conversion, pp.896-900, English, Introduction international proceedings

基板再利用に向けたELO後基板の清浄化工程と再成長の検討
宮下直也; 八木修平; 渡辺健太郎; 木村大希; SODABANLU Hassanet; 中田達也; 杉山正和; 杉山正和; 岡田至崇
Aug. 2017, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 78th, ROMBUNNO.6p‐PA5‐23, Japanese, 201702288830548138

1eV帯InGaAs:Nδドープ超格子の作製
梅田峻平; 八木修平; 宮下直也; 岡田至崇; 矢口裕之
01 Mar. 2017, 応用物理学会春季学術講演会講演予稿集(CD-ROM), 64th, ROMBUNNO.14p‐B6‐9, Japanese, 201702242750399704

エピタキシャルリフトオフにより分離したGaAs基板上の堆積物分析
中田達也; 渡辺健太郎; SODABANLU H; 木村大希; 宮下直也; 杉山正和; 岡田至崇; 岡田至崇; 中野義昭; 中野義昭
01 Mar. 2017, 応用物理学会春季学術講演会講演予稿集(CD-ROM), 64th, ROMBUNNO.14p‐B6‐13, Japanese, 201702230203994233

Multiband Formation in Cr doped CuGaS2 Thin Films Synthesized by Chemical Spray Pyrolysis
Nazmul Ahsan; Sivaperuman Kalainathan; Naoya Miyashita; Takuya Hoshii; Yoshitaka Okada
2017, Proc. 44th IEEE Photovoltaics Specialists Conference, pp.2334-2337, English, Introduction international proceedings

Analysis of Deposited Residues and Its Cleaning Process on GaAs Substrate after Epitaxial Lift-Off
Tatsuya Nakata; Kentaroh Watanabe; Hassanet Sodabanlu; Daiki Kimura; Naoya Miyashita; Yoshitaka Okada; Yoshiaki Nakano; Masakazu Sugiyama
2017, Proc. 44th IEEE Photovoltaics Specialists Conference, pp.854-857, English, Introduction international proceedings, 0160-8371, WOS:000455636000208

Laser Beam Induced Current (LBIC) Mapping of InGaP/GaAs/Ge Triple Junction Solar Cells with Luminescence Coupling
Bernice Mae Yu Jeco; Tomah Sogabe; Akio Ogura; Naoya Miyashita; Ryo Tamaki; Yoshitaka Okada
2016, 2016 IEEE 43RD PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), 1229-1234, English, Introduction international proceedings, 0160-8371, WOS:000399818701051

Designing III-V dilute nitride alloys for IBSC application
Nazmul Ahsan; Naoya Miyashita; Kin Man Yu; Wladek Walukiewicz; Yoshitaka Okada
2016, 2016 IEEE 43RD PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), 2761-2764, English, Introduction international proceedings, 0160-8371, WOS:000399818702180

Siドープ量子ドット太陽電池の集光特性評価
内藤駿弥; 宮下直也; 下村北斗; 下村北斗; 玉置亮; 星井拓也; 岡田至崇
26 Feb. 2015, 応用物理学会春季学術講演会講演予稿集(CD-ROM), 62nd, ROMBUNNO.13A-A26-5, Japanese, 201502288802603447

Characterization of 1.0 eV GaInNAsSb solar cells for multi-junction applications and the effect of annealing
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
2015, Proc. 25nd European Photovoltaic Solar Energy Conference, pp.1461-1465, English, Introduction international proceedings

Effect of light concentration on Si doped quantum dot solar cells
Shunya Naitoh; Naoya Miyashita; Kasidit Toprasertpong; Ryo Tamaki; Takuya Hoshii; Masakazu Sugiyama; Yoshitaka Okada
2015, Proc. 25nd European Photovoltaic Solar Energy Conference, pp.245-248, English, Introduction international proceedings

Concentrating Photovoltaic Properties of GaInNAsSb/Ge Dual Junction Tandem Solar Cell
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
2014, 2014 IEEE 40TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC), 520-523, English, Introduction international proceedings, WOS:000366638900119

Local conductivity characteristics of individual ErAs island for solar cell tunnel junction application
Chao-Yu Hung; Tomah Sogabe; Naoya Miyashita; Yasushi Shoji; Shunya Naitoh; Yoshitaka Okada
2014, 2014 IEEE 40TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC), 228-232, English, Introduction international proceedings, WOS:000366638900052

Device Structure Engineering of GaInNAsSb/GaAs Heterojunction Solar Cells
Naoya Miyashita; Muhammad Monirul Islam; Nazmul Ahsan; Yoshitaka Okada
2013, 2013 IEEE 39TH PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), 2109-2112, English, Introduction international proceedings, 0160-8371, WOS:000340054100474

Study on The Device Structure of GaInNAs(Sb) Based Solar Cells for Use in 4-junction Tandem Solar Cells
Naoya Miyashita; Nazmul Ahsan; Muhammad Monirul Islam; Yoshitaka Okada
2012, 2012 38TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), 954-956, English, Introduction international proceedings, WOS:000309917801054

Bias dependent admittance measurement of GaInNAsSb-based solar cell structure
Muhammad Monirul Islam; Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
2012, 2012 38TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), 2543-2547, English, Introduction international proceedings, WOS:000309917802188

Evaluation of GaInNAs(Sb) solar cells for use in next generation III-V tandem solar cells
Naoya Miyashita; Nazmul Ahsan; M. Monirul Islam; Yoshitaka Okada
2011, Conference Record of the IEEE Photovoltaic Specialists Conference, 000526-000529, English, Introduction international proceedings, 0160-8371, 84861045652

Effect of antimony on electron trap density in GaInNAsSb solar cell grown by atomic hydrogen-assisted molecular beam epitaxy
Naoya Miyashita; Haruhiro Oigawa; Yoshitaka Okada
2010, Proc. 25th European Photovoltaic Solar Energy Conference / 5th IEEE World Conference on Photovoltaic Energy Conversion, pp.946-949, English, Introduction international proceedings

ANTIMONY ENHANCED HOMOGENEOUS NITROGEN INCORPORATION INTO GaInNAs FILMS GROWN BY ATOMIC HYDROGEN-ASSISTED MOLECULAR BEAM EPITAXY
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
2010, 35TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE, 2084-2088, English, Introduction international proceedings, 0160-8371, WOS:000287579502073

Effect of indium composition on GaInNAsSb solar cells grown by atomic hydrogen-assisted molecular beam epitaxy
Naoya Miyashita; Shuhei Ichikawa; Yoshitaka Okada
2009, 2009 34TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE, VOLS 1-3, 1126-+, English, Introduction international proceedings, 0160-8371, WOS:000280345900245

Effect of Increasing Nitrogen Composition on the Performance of GaAs/GaInNAs Heterojunction Solar Cells
Naoya Miyashita; Yukiko Shimizu; Yoshitaka Okada
2007, Proc. 22nd European Photovoltaic Solar Energy Conference and Exhibition, pp.414-417, English, Introduction international proceedings

Fabrication of GaInNAs-based solar cells for application to multi-junction tandem solar cells
Naoya Miyashita; Yukiko Shimizu; Naoto Kobayashi; Yoshitaka Okada; Masafumi Yamaguchi
2006, CONFERENCE RECORD OF THE 2006 IEEE 4TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS 1 AND 2, 869-872, English, Introduction international proceedings, WOS:000241251600222

Optimization of growth of GaInNAs dilute nitrides for multi-junction solar cell applications
Yukiko Shimizu; Naoya Miyashita; Yusuke Mura; Akira Uedono; Yoshitaka Okada
2006, CONFERENCE RECORD OF THE 2006 IEEE 4TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS 1 AND 2, 811-814, English, Introduction international proceedings, WOS:000241251600207

Fabrication of GaAs/GaInNAs Heterojunction Solar Cells Applicable To High-Efficiency Multi-junction Tandem Structures
KOBAYASHI Naoto; MIYASHITA Naoya; SHIMIZU Yukiko; OKADA Yoshitaka; YAMAGUCHI Masafumi
13 Sep. 2005, Extended abstracts of the ... Conference on Solid State Devices and Materials, 2005, 352-353, English, 10022541889, AA10777858

Photovoltaics for Space
Naoya Miyashita; Yoshitaka Okada
Contributor, Chapter 10. Inverted lattice-matched GaInP/GaAs/GaInNAsSb triple-junction solar cells: epitaxial lift-off thin-film devices and potential space applications, ELSEVIER, Oct. 2022

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, 第72回応用物理学会春季学術講演会
16 Mar. 2025
14 Mar. 2025- 17 Mar. 2025

Analyses of Luminescence Coupling in ELO thin-film tandem solar cells
Sota Itsubo; Dairoku Inaba; Naoya Miyashita; Koichi Yamaguchi
Poster presentation, English, 35th International Photovoltaic Science and Engineering Conference
14 Nov. 2024

Characterization of Spalling-released thin-film tandem solar cells
Naoya Miyashita; Yasushi Shoji; Takeyoshi Sugaya; Tomah Sogabe; Koichi Yamaguchi; Yoshitaka Okada
Oral presentation, English, 35th International Photovoltaic Science and Engineering Conference
13 Nov. 2024

ELO薄膜タンデム太陽電池の発光結合特性評価
伊坪壮太; 稲葉大陸; 宮下直也; 山口浩一
Poster presentation, 第85回応⽤物理学会秋季学術講演会
19 Sep. 2024
16 Sep. 2024- 20 Sep. 2024

Spalling工程による薄膜タンデム太陽電池の作製と評価
宮下直也; 庄司靖; 菅谷武芳; 曽我部東馬; 山口浩一; 岡田至崇
Oral presentation, 第85回応用物理学会秋季学術講演会
17 Sep. 2024
16 Sep. 2024- 20 Sep. 2024

2端子型ELO薄膜タンデム太陽電池のサブセルI-V解析
宮下直也; 稲葉大陸; 伊坪壮太; 曽我部東馬; 岡田至崇; 山口浩一
Poster presentation, 第21回「次世代の太陽光発電システム」シンポジウム（第4回⽇本太陽光発電学会学術講演会）
11 Jul. 2024
11 Jul. 2024- 12 Jul. 2024

バイアス光照射による薄膜タンデム太陽電池の各サブセルのI-V測定
稲葉 大陸; 伊坪 壮太; 宮下 直也; 曽我部 東馬; 岡田 至崇; 山口 浩一
Poster presentation, 第71回応用物理学会春季学術講演会
24 Mar. 2024

InAs/InAsSb面内超高密度量子ドット層の光伝導特性
大山 琢未; 荒尾 光哉; 宮下 直也; 山口 浩一
Poster presentation, 第71回応用物理学会春季学術講演会
24 Mar. 2024

Si(111)基板上への高密度InAsSb/InAsコアシェルナノワイヤーの成長
渡部 陸太; 中川 竜輔; 宮下 直也; 山口 浩一
Poster presentation, 第71回応用物理学会春季学術講演会
24 Mar. 2024

Dilute nitride based MQWs with strain compensation for 1.0 eV subcells
Naoya Miyashita; Yusuke Oteki; Nazmul Ahsan; Tomah Sogabe; Koichi Yamaguchi; Yoshitaka Okada
Oral presentation, English, The 33rd International Photovoltaic Science and Engineering Conference (PVSEC-33)
Nov. 2022

Optimizing the positions of quantum dot layers to increase the light absorption in quantum dot solar cells with light trapping structure
Yusuke Oteki; Maxime Giteau; Kei Fukushima; Kento Kitahara; Naoya Miyashita; Ryo Tamaki; Yoshitaka Okada
6th IEEE Electron Devices Technology and Manufacturing Conference, EDTM 2022
2022
2022 2022

Enhancement of the light absorption rate of quantum dot solar cells by Fabry-Pérot resonance
Oteki Yusuke; Giteau Maxime; Fukushima Kei; Kei Kitahara; Naoya Miyashita; Ryo Tamaki; Yoshitaka Okada
Japanese, JSAP Annual Meetings Extended Abstracts, The Japan Society of Applied Physics
26 Feb. 2021
26 Feb. 2021- 26 Feb. 2021

エピタキシャルリフトオフ法を用いた薄膜太陽電池の作製
宮下 直也; 岡田 至崇
Invited oral presentation, 第81回応用物理学会秋季学術講演会, Invited
Sep. 2020

エピタキシャルリフトオフ法を用いたエピ薄膜分離と基板再生技術開発
宮下 直也; 岡田 至崇
Invited oral presentation, 第67回応用物理学会春季学術講演会, Invited
Mar. 2020

Extending carrier lifetime by controlling the composition of GaAs_xSb_1-x/GaAs quantum dots
Oteki Yusuke; Shoji Yasushi; Miyashita Naoya; Okada Yoshitaka
Japanese, JSAP Annual Meetings Extended Abstracts, The Japan Society of Applied Physics
28 Feb. 2020
28 Feb. 2020- 28 Feb. 2020

Growth rate dependency of GaAsSb / GaAs Quantum Dots
Oteki Yusuke; Shoji Yasushi; Miyashita Naoya; Okada Yoshitaka
Japanese, JSAP Annual Meetings Extended Abstracts, The Japan Society of Applied Physics
04 Sep. 2019
04 Sep. 2019- 04 Sep. 2019

Strain Compensated Dilute Nitride MQWs As New 1 eV Solar Cell Absorber
Naoya Miyashita; Yoshitaka Okada
Oral presentation, English, SemiconNano 2019, Kobe, International conference
Sep. 2019

Study of GaInP/GaAs/GaInNAsSb 3J solar cells: Effect of hydrogen incorporation to GaInNAsSb in MOCVD/MBE hybrid growth
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Oral presentation, English, Asia Pacific Society for Materials Research (APSMR) Annual Meeting 2019, Invited, Sapporo, International conference
Jul. 2019

Epitaxial Lifted-Off Thin Film GaInP/GaAs/GaInNAsSb Lattice-Matched Triple Junction Solar Cells
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada; Rao Tatavarti; Andree Wibowo; Noren Pan
Oral presentation, English, The 46th IEEE Photovoltaic Specialists Conference (PVSC-46), Chicago, International conference
Jun. 2019

Effect of Annealing on The Bottom Cell in GaInP/GaAs/GaInNAsSb Triple Junction Solar Cells by MBE/MOCVD Hybrid Growth
Naoya Miyashita; Yilun He; Nazmul Ahsan; Yoshitaka Okada
2019 Compound Semiconductor Week (CSW), IEEE, http://orcid.org/0000-0003-1311-1589
May 2019
May 2019 May 2019

GaSb/GaAs quantum nanostructure solar cells under high sunlight concentration
Oteki Yusuke; Shoji Yasushi; Miyashita Naoya; He Yilun; Okada Yoshitaka
Japanese, JSAP Annual Meetings Extended Abstracts, The Japan Society of Applied Physics
25 Feb. 2019
25 Feb. 2019- 25 Feb. 2019

GaSb/GaAs quantum nanostructures for intermediate band solar cell under high sunlight concentration
Yusuke Oteki; Yasushi Shoji; Naoya Miyashita; Yilun He; Yoshitaka Okada
English, 2019 COMPOUND SEMICONDUCTOR WEEK (CSW)
2019
2019 2019

Epitaxial Lift-Off of Ultrathin Heterostructures for Hot-Carrier Solar Cell Applications
Maxime Giteau; Kentaroh Watanabe; Hassanet Sodabanlu; Naoya Miyashita; Masakazu Sugiyama; Andrea Cattoni; Stephane Collin; Jean-Francois Guillemoles; Yoshitaka Okada
English, 2019 COMPOUND SEMICONDUCTOR WEEK (CSW)
2019
2019 2019

ELO-released thin film solar cells and application to multi-junction devices
Naoya Miyashita; Yilun He; Nazmul Ahsan; Beno?t Behaghel; Jean-Fran?ois Guillemoles; Yoshitaka Okada
Oral presentation, English, 7th LIA NextPV International Workshop, Bordeaux, International conference
Dec. 2018

Inverted growth of lattice-matched multijunction solar cells with 1.0 eV GaInNAsSb subcell
Naoya Miayshita; Yilun He; Takaaki Agui; Hiroyuki Juso; Tatsuya Takamoto; Yoshitaka Okada
Oral presentation, English, The 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, International conference
Jun. 2018

Inverted and non-inverted grown lattice-matched multijunction solar cells with 1.0eV GaInNAsSb subcell
Naoya Miyashita; Yoshitaka Okada
Oral presentation, English, 6th LIA NextPV International Workshop, Tokyo, International conference
Dec. 2017

Characterization of Inverted Grown Lattice-matching Multijunction Solar Cells with 1.0eV Dilute Nitride Subcell
Naoya Miyashita; Takaaki Agui; Hiroyuki Juso; Tatsuya Takamoto; Yoshitaka Okada
Oral presentation, English, Photovoltaic Science and Engineering Conference (PVSEC-27), Shiga, International conference
Nov. 2017

Development of dilute nitrides and multijunction solar cells
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Oral presentation, English, 2nd International Conference on Advances in Materials Science and Technology, Invited, Vellore, International conference
Oct. 2017

Effect of Hydrogen Annealing for Dilute Nitride GaInNAsSb Solar Cells
Naoya Miyashita; Yilun He; Yoshitaka Okada
Oral presentation, English, Compound Semiconductor Week (CSW) 2017, Berlin, International conference
May 2017

Enhancement of photocurrent in thin film dilute nitride cells separated by epitaxial lift-off technique
Naoya Miyashita; Yoshitaka Okada
Oral presentation, The 63rd JSAP spring meeting (English session symposium: "Photovoltaic 4.0"）, Yokohama, Domestic conference
Mar. 2017

Characterization of Dilute Nitride Based Photovoltaics for Multi-junction Solar Cell Applications
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Oral presentation, English, International Conference on Modern Materials Research (ICMMR2016), Invited, Uthangarai, International conference
Dec. 2016

Improvement of Dilute Nitride GaInNAsSb Thin Films and Photovoltaic Characteristics
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Oral presentation, English, International Conference on Materials Processing and Applications (ICMPA2016), Invited, Vellore, International conference
Dec. 2016

Enhancement of Photocurrent in Epitaxial Lift-Off Thin Film GaInNAsSb Solar Cells By The Light Confinement Structure
Naoya Miyashita; Beno?t Behaghel; Jean-Fran?ois Guillemoles; Yoshitaka Okada
Oral presentation, English, Photovoltaic Science and Engineering Conference (PVSEC-26), Singapore, International conference
Oct. 2016

Improvement of 1.0 eV GaInNAsSb solar cell performance upon annealing
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Oral presentation, English, Compound Semiconductor Week (CSW) 2016, Toyama, International conference
Jun. 2016

Enhancement of Carrier Collection in GaInNAs:Sb Solar Cells
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Oral presentation, English, EMN Prague Meeting, Invited, Prague, International conference
Jun. 2016

Improved Carrier Collection in Thick GaInNAsSb Solar Cells
N. Miyashita; N. Ahsan; Y. Okada
Oral presentation, English, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto, International conference
Nov. 2014

多接合太陽電池用GaInNAs(Sb)薄膜のMBE成長と高品質化
宮下直也; 岡田至崇
Oral presentation, Japanese, 第44回結晶成長国内会議, Invited, 東京, Domestic conference
Nov. 2014

Effect of Electric Field in GaInNAsSb based Solar Cells
Naoya Miyashita; Nazmul Ahsan; Muhammad Monirul Islam; Yoshitaka Okada
Oral presentation, English, 2013 JSAP-MRS Joint Symposia, Kyoto, International conference
Sep. 2013

Photovoltaic Characteristics of GaInNAsSb Solar Cells under Concentrated Light Source
N. Miyashita; K. Watanabe; Y. Okada
Oral presentation, English, 9th Conference on Concentrator Photovoltaics (CPV-9), Miyazaki, International conference
Apr. 2013

Fabrication of nip and pin structure GaInNAsSb solar cells
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Oral presentation, English, 2012 Collaborative Conference on Crystal Growth, Invited, Orland, International conference
Dec. 2012

High Electron Mobility in Ga(In)NAs Films Grown by MBE
Naoya Miyashita; Nazmul Ahsan; Makoto Inagaki; Muhammad Monirul Islam; Masafumi Yamaguchi; Yoshitaka Okada
Oral presentation, English, The 17th International Conference on Molecular Beam Epitaxy, Nara, International conference
Sep. 2012

Antimony Surfactant Mediated Improvement of the Properties of GaInNAsSb Films for Multi-junction Tandem Solar Cells
Naoya Miyashita; Nazmul Ahsan; Kin Man Yu; Wladek Walukiewicz; Yoshitaka Okada
Oral presentation, English, 2011 MRS spring meeting, San Francisco, International conference
Apr. 2011

Reduction of nitrogen-induced localized states in GaInNAs films grown by antimony-assisted MBE
Naoya Miyashita; Nazmul Ahsan; Yoshitaka Okada
Oral presentation, English, Renewable Energy 2010 International Conference and Exhibition, Yokohama, International conference
Jun. 2010

Characteristics of GaInNAsSb Solar Cells Grown by Atomic Hydrogen-Assisted Molecular Beam Epitaxy
Naoya Miyashita; Shuhei Ichikawa; Yoshitaka Okada
Oral presentation, English, 18th International Photovoltaic Science and Engineering Conference, Kolkata, International conference
Jan. 2009

Introduction to Info-Power and Energy
2024 - Present
Tokyo University of Foreign Studies

Fundamentals of VLSI Fabrication
2024 - Present
The University of Electro-Communications

Electronic Engineering Laboratory II ;XRD
2022 - Present
The University of Electro-Communications

Environmental Engineering
2022 - Present
The University of Electro-Communications

Fundamental of Engineering Science
2024
The University of Electro-Communications

Advanced Lectures on Optoelectronics
2020
Saitama University

The Japan Photovoltaic Society

THE JAPAN SOCIETY OF APPLIED PHYSICS

移動体用太陽電池の研究開発（超高効率モジュール技術開発）
高本達也; 杉山正和; 岡田至崇
NEDO 太陽光発電主力電源化推進技術開発／太陽光発電の新市場創造技術開発, Coinvestigator not use grants, 格子不整合系太陽電池の剥離技術開発
Jul. 2020 - Mar. 2025

N.A.
宮下 直也
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), The University of Tokyo, Grant-in-Aid for Scientific Research (C), Principal investigator, 本研究はマルチバンド材料であるGaInNAsに着目し中間バンドを介した2段階励起レート向上と再緩和抑制に向け検討を進めている。GaInNAsはInとNの添加量を制御することによってGaAs基板上への格子整合が可能な材料として知られているが、N組成の増加に伴い導入される結晶欠陥の抑制が課題となる。 本年度は、GaAs基板上に成長可能な歪み補償型GaInNAs/GaNAs系多重量子井戸構造を用いた太陽電池を作製し、成膜条件、構造の検討を実施した。 高分解X線回折測定により良好な周期構造とヘテロ界面の形成を確認した。また、GaAs基板に対して格子整合を維持されており、設計通りの歪み補償効果が実現できていることを確認した。また、多重量子井戸層の成長温度の最適化を行い、発電特性の改善を得た。さらにポストアニールを実施し、周期構造、光吸収端エネルギー、発電特性への変化を調べ、最適条件の検討を進めた。また、多重量子井戸構造の改善に向け、ヘテロ界面へのGaAsスペーサー層の挿入を検討した。成膜時、およびポストアニールに伴うIn等の構成元素の相互拡散の影響について調べ、構造の最適化を進めた。以上の最適化検討を行い、標準条件下において多重量子井戸層の量子効率の向上を得た。また、活性層における2段階励起特性評価のため、評価システムの設計および白色光源の導入を行った。, 20K05682
Apr. 2020 - Mar. 2024

希釈窒化物半導体による近赤外域多重量子井戸構造の歪み制御技術開発
宮下直也
池谷科学技術振興財団, 単年度研究助成, 東京大学, Principal investigator, 0311063-A
Apr. 2019 - Mar. 2020

超高効率・低コストIII-V化合物太陽電池モジュールの研究開発（超高効率セルおよび低コスト化技術開発）
岡田至崇; 杉山正和
NEDO 高性能・高信頼性太陽光発電の発電コスト低減技術開発／革新的新構造太陽電池の研究開発, Coinvestigator not use grants
Jul. 2015 - Mar. 2020

原子状水素を用いた希釈窒化物混晶への水素修飾とN-H結合の制御
宮下 直也
日本学術振興会, 科学研究費助成事業, Principal investigator
Apr. 2016 - Mar. 2018

高効率集光型太陽電池セル、モジュール及びシステムの開発（日EU共同開発）
山口真史; 岡田至崇
NEDO 革新的太陽光発電技術研究開発（革新型太陽電池国際研究拠点設備事業）, Coinvestigator not use grants
2010 - 2014

ポストシリコン超高効率太陽電池の研究開発
中野義昭; 宮野健次郎; 瀬川浩司; 岡田至崇
NEDO 革新的太陽光発電技術研究開発（革新型太陽電池国際研究拠点設備事業）, Coinvestigator not use grants
2008 - 2014