T. Arai, D. Timmerman, R. Wakamatsu, D. Lee, A. Koizumi, and Y. Fujiwara: "Improvement of excitation efficiency of red luminescence in Eu-doped GaN/AlGaN multiple quantum well structures grown by organometallic vapor phase epitaxy"
Journal of Luminescence 158 (2015) pp. 70-74. http://dx.doi.org/10.1016/j.jlumin.2014.09.036
M. Nakayama, S. Nakamura, H. Takeuchi, A. Koizumi, and Y. Fujiwara: "Unique properties of photoluminescence excitation spectra in a Eu-doped GaN epitaxial film"
Applied Physics Letters 106 (2015) pp. 012102/1-4. http://dx.doi.org/10.1063/1.4905309
A. Koizumi, K. Kawabata, D. Lee, A. Nishikawa, Y. Terai, H. Ofuchi, T. Honma, and Y. Fujiwara: "In situ Eu doping into AlxGa1−xN grown by organometallic vapor phase epitaxy to improve luminescence properties"
Optical Materials 41 (2015) pp. 75-79. http://dx.doi.org/10.1016/j.optmat.2014.11.005
M. Ishii, A. Koizumi, and Y. Fujiwara: "Nanoscale determinant to brighten up GaN:Eu red light-emitting diode: Local potential of Eu-defect complexes"
Journal of Applied Physics 117 (2015) 155307/1-7. http://dx.doi.org/10.1063/1.4918662
M. Ishii, A. Koizumi, and Y. Fujiwara: "Three-dimensional spectrum mapping of bright emission centers: Investigating the brightness-limiting process in Eu-doped GaN red light emitting diodes"
Applied Physics Letters 107 (2015) 082106/1-4. http://dx.doi.org/10.1063/1.4929531
D. Timmerman, R. Wakamatsu, K. Tanaka, D. Lee, A. Koizumi, and Y. Fujiwara: "Resonant energy transfer between Eu luminescent sites and their local geometry in GaN"
Applied Physics Letters 107 (2015) 151107/1-4. http://dx.doi.org/10.1063/1.4933301
T. Shigemune, A. Koizumi, Y. Kashiwagi, H. Kakiuchi, Y. Takemura, M. Yamamoto, M. Saitoh, M. Takahashi, T. Ohno, M. Nakamoto, N. Aoyagi, Y. Yoshida, K. Murahashi, K. Ohtsuka, and Y. Fujiwara: "Formation of Electrode for GaN-Based Blue Light Emitting Diodes by Screen Printing Using Ag Nanoparticle Inks"
7th International Symposium on Advanced Plasma Science and Its Applications for Nitrides and Nanomaterials (ISPlasma2015), B1-O-03, Nagoya University, Nagoya, Japan, March 26-31 (2015).
K. Okada, R. Wakamatsu, D. Timmerman, T. Kojima, A. Koizumi, and Y. Fujiwara: "Investigation of Energy Transfer Process in Eu-Doped GaN by Two-Wavelength Excited Photoluminescence"
7th International Symposium on Advanced Plasma Science and Its Applications for Nitrides and Nanomaterials (ISPlasma2015), B1-O-06, Nagoya University, Nagoya, Japan, March 26-31 (2015).
M. Matsuda, A. Koizumi, T. Kojima, D. Timmerman, and Y. Fujiwara: "Formation of a New Eu Luminescent Center by Zn,O-Codoping in Eu-Doped GaN"
7th International Symposium on Advanced Plasma Science and Its Applications for Nitrides and Nanomaterials (ISPlasma2015), B1-O-07, Nagoya University, Nagoya, Japan, March 26-31 (2015).
Y. Fujiwara, R. Wakamatsu, D. Timmerman, and A. Koizumi: "Energy migration between Eu luminescent sites in Eu-doped GaN"
7th Asia-Pacific Workshop on Widegap Semiconductors (APWS 2015), TUA2-4, Seoul, Korea, May May 17-20 (2015).
Y. Fujiwara, R. Wakamatsu, A. Koizumi, and V. Dierolf: [Invited Talk]: "Present understanding of Eu luminescent centers in Eu-doped GaN"
Collaborative Conference on 3D and Materials Research 2015 (CC3DMR2015), BEXCO, Busan, Korea, June 15-19 (2015).
Y. Fujiwara, T. Kojima, and A. Koizumi: [Invited Talk]: "Towards highly efficient wavelength-stable red light-emitting diodes using Eu-doped GaN as an active layer"
Workshop on Frontier Photonic and Electronic Materials and Devices - 2015 German-Japanese-Spanish Joint Workshop -, Shiran-Kaikan, Kyoto University, Kyoto, Japan, July 11-14 (2015).
T. Inaba, A. Koizumi, and Y. Fujiwara: "In-plane compressive strain dependence of photoluminescence properties in Eu-doped GaN"
28th International Conference on Defects in Semiconductors (ICDS-28), Helsinki, Finland, July 27-31 (2015).
Y. Fujiwara, M. Matsuda, W. Zhu, T. Kojima, and A. Koizumi: [Invited Talk]: "Valence control of Eu ions in Eu-doped GaN grown by organometallic vapor phase epitaxy"
SPIE Nanoscience + Engineering, 9551-85, San Diego, USA, August 9-13 (2015).
Y. Fujiwara: [Invited Talk]: "Towards highly efficient wavelength-stable red light-emitting diodes using Eu-doped GaN"
15th International Meeting on Information Display (IMID2015), 3-3, EXCO, Daegu, Korea, August 18-21 (2015).
Y. Fujiwara, T. Inaba, T. Kojima, and A. Koizumi: [Invited Talk]: "Drastic enhancement of Eu emission from red light-emitting Eu-doped GaN in a microcavity"
11th Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR 2015), 26H1-2, BEXCO, Busan, Korea, August 24-28 (2015).
W. Zhu, D. Timmerman, B. Mitchell, A. Koizumi, T. Gregorkiewicz, and Y. Fujiwara: "Characterization of GaN/Eu-doped GaN multiple-nanolayer structures grown by low-temperature organometallic vapor phase epitaxy"
11th International Conference on Nitride Semiconductors (ICNS-11), WeOP198, Beijing, China, August 30- September 4 (2015).
M. Ishii, A. Koizumi, and Y. Fujiwara: "Brightening GaN:Eu red LED by back-and-force motion of injection charges and its applied to site-selective analyses of emission centers"
4th International Conference on the Physics of Optical Materials and Devices, Budva, Montenegro, August 31- September 4 (2015).
Y. Fujiwara, T. Inaba, T. Kojima, and A. Koizumi: [Invited Talk]: "Towards highly efficient wavelength-stable red light-emitting diodes with Eu-doped GaN: effects of in-plane strain on Eu emission"
5th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures (SemiconNano2015), I-26, Lakeshore Hotel, Hsinchu, Taiwan, September 6-11 (2015).
S. Takano, D. Kishimoto, T. Kojima, and Y. Fujiwara: "Sputtering-assisted metalorganic chemical vapor deposition of Tm-doped ZnO for photonic down-conversion for Si solar cells"
International Conference on Advanced Materials (IUMRS-ICAM2015), III-1Tu3B2-5, Jeju, Korea, October 25-29 (2015).
Y. Fujiwara: [Invited Talk]: "Towards Photonic Applications of Rare-Earth-Doped ZnO"
International Conference on Advanced Materials (IUMRS-ICAM2015), II-4Th3A3-2, Jeju, Korea, October 25-29 (2015).
M. Ishii, A. Koizumi, and Y. Fujiwara: "Boost in intensity of GaN:Eu red LED by motion control of injection charges and its application to diagnosis of Eu emission centers"
6th International Symposium on Growth of III-Nitrides (ISGN-6), Tu-B21, Act City Hamamatsu, Hamamatsu, Japan, November 8-13 (2015).
M. Ishii, A. Koizumi, and Y. Fujiwara: "Gap between energetically and optically favorable emission centers in GaN:Eu red LED: Necessity of local distortion control"
6th International Symposium on Growth of III-Nitrides (ISGN-6), Tu-B22, Act City Hamamatsu, Hamamatsu, Japan, November 8-13 (2015).
A. Koizumi, Y. Maruyama, K. Okada, T. Shigemune, T. Kojima, and Y. Fujiwara: "Electrical properties of trapping level related to the excitation of Eu luminescent center in Eu-doped GaN investigated by thermally stimulated current"
6th International Symposium on Growth of III-Nitrides (ISGN-6), Tu-B23, Act City Hamamatsu, Hamamatsu, Japan, November 8-13 (2015).
B. Mitchell, D. Timmerman, J. Poplawsky, W. Zhu, A. Koizumi, V. Dierolf, and Y. Fujiwara: "A novel utilization of environmental O for developing device compatible Eu-doped GaN aimed at red LED applications"
6th International Symposium on Growth of III-Nitrides (ISGN-6), Tu-B26, Act City Hamamatsu, Hamamatsu, Japan, November 8-13 (2015).
J. Takatsu, A. Koizumi, S. Yamanaka, M. Matsuda, T. Kojima, and Y. Fujiwara: "Luminescence properties of Eu-doped InxGa1-xN and their application to the detection of In segregation"
19th SANKEN International, The 14th SANKEN Nanotechnology Symposium, 3rd KANSAI Nanoscience and Nanotechnology, 11th Handai Nanoscience and Nanotechnology International Symposium, PS-43, Icho Kaikan, Osaka University, Suita, Japan, December 7-9 (2015).
T. Shigemune, A. Koizumi, and Y. Fujiwara: "Separation of Eu-related trap levels in Eu-doped GaN by Laplace deep level transient spectroscopy"
19th SANKEN International, The 14th SANKEN Nanotechnology Symposium, 3rd KANSAI Nanoscience and Nanotechnology, 11th Handai Nanoscience and Nanotechnology International Symposium, PS-45, Icho Kaikan, Osaka University, Suita, Japan, December 7-9 (2015).
M. Ogawa, N. Fujioka, K. Sakuragi, T. Kojima, A. Koizumi, and Y. Fujiwara: "High-Q photonic crystal double-heterostrcture nanocavity with Er,O-codoped GaAs for low-threshold lasers"
19th SANKEN International, The 14th SANKEN Nanotechnology Symposium, 3rd KANSAI Nanoscience and Nanotechnology, 11th Handai Nanoscience and Nanotechnology International Symposium, PS-49, Icho Kaikan, Osaka University, Suita, Japan, December 7-9 (2015).
T. Inaba, A. Koizumi, and Y. Fujiwara: "Enhancing Eu emission intensity by strain engineering in GaN heteroepitaxial layers"
19th SANKEN International, The 14th SANKEN Nanotechnology Symposium, 3rd KANSAI Nanoscience and Nanotechnology, 11th Handai Nanoscience and Nanotechnology International Symposium, PS-71, Icho Kaikan, Osaka University, Suita, Japan, December 7-9 (2015).
T. Inaba, A. Koizumi, and Y. Fujiwara: "Controlling the fraction of luminescent sites in Eu-doped GaN by compressive strain"
Nanophotonics in Asia 2015, Nakanoshima Center, Osaka, Japan, December 10-11 (2015).
Y. Fujiwara, T. Inaba, B. Mitchell, T. Kojima, and A. Koizumi: [Invited Talk]: "Towards highly efficient wavelength-stable red light-emitting diodes using Eu-doped GaN"
2nd International Workshop on Luminescent Materials 2015 (LumiMat¡Ç15), I-21, Kyoto University, Kyoto, Japan, December 12-13 (2015).
M. Ishii and Y. Fujiwara: [Invited Talk]: "Optoelectronic communications with GaN:Eu red LED: Messages from atomic scale emission centers"
2nd International Workshop on Luminescent Materials 2015 (LumiMat¡Ç15), I-22, Kyoto University, Kyoto, Japan, December 12-13 (2015).
19th SANKEN International, The 14th SANKEN Nanotechnology Symposium, 3rd KANSAI Nanoscience and Nanotechnology, 11th Handai Nanoscience and Nanotechnology International Symposium (Suita, Japan) Best Poster Award
"Enhancing Eu emission intensity by strain engineering in GaN heteroepitaxial layers"