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Park, J.-H.*; Wakahara, Akihiro*; Okada, Hiroshi*; Furukawa, Yuzo*; Kim, Y.-T.*; Chang, H.-J.*; Song, J.*; Shin, S.*; Lee, J.-H.*; Sato, Shinichiro; et al.
Japanese Journal of Applied Physics, 49(3), p.032401_1 - 032401_5, 2010/03
Times Cited Count:1 Percentile:5.52(Physics, Applied)Okada, Hiroshi*; Takemoto, Kazumasa*; Oikawa, Fumitake*; Furukawa, Yuzo*; Wakahara, Akihiro*; Sato, Shinichiro; Oshima, Takeshi
Physica Status Solidi (C), 6(Suppl.2), p.S631 - S634, 2009/05
Light emitting field effect transistor (FET) based-on AlGaN/GaN high electron mobility transistor (HEMT) structure with spatially selective doping of rare-earth ions (REIs) as a luminescence center in the channel is proposed and investigated. Fabricated device showed excellent I-V characteristics as a transistor with gate control. By applying a drain bias of 20 V, red emission suggesting a luminescence from Eu ion was clearly observed. Applying a negative bias to the Schottky gate decreased the luminescence intensity.
Okada, Hiroshi*; Nakanishi, Yasuo*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi
Nuclear Instruments and Methods in Physics Research B, 266(5), p.853 - 856, 2008/03
Times Cited Count:8 Percentile:50.37(Instruments & Instrumentation)To develop light emitting devices with radiation hardness, photoluminescence properties of non- and Eu-doped GaN after proton irradiation were investigated. The samples were irradiated with protons at 380 keV up to 110/cm at room temperature RT. The photoluminescence properties for the samples were measured at RT. As a results, the luminescence properties for non-doped GaN much decrease due to irradiation at 110/cm. On the other hand, for Eu-doped GaN, the luminescence properties that correspond to the transition did not show any degradation after irradiation at 110/cm.
Wakahara, Akihiro*; Okada, Hiroshi*; Oikawa, Fumitake*; Takemoto, Kazumasa*; Oshima, Takeshi; Ito, Hisayoshi
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 17, 2007/02
no abstracts in English
Okada, Hiroshi*; Lee, H.-S.*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi; Kamiya, Tomihiro
Solar Energy Materials and Solar Cells, 90(1), p.93 - 99, 2006/01
Times Cited Count:4 Percentile:20.61(Energy & Fuels)no abstracts in English
Okada, Hiroshi*; Natsume, Satoshi*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi; Kamiya, Tomihiro
Proceedings of the 6th International Workshop on Radiation Effects on Semiconductor Devices for Space Application (RASEDA-6), p.147 - 150, 2004/10
no abstracts in English
Nakanishi, Yasuo*; Wakahara, Akihiro*; Okada, Hiroshi*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi
Physica Status Solidi (B), 240(2), p.372 - 375, 2003/11
Times Cited Count:19 Percentile:65.58(Physics, Condensed Matter)Luminescence propeties of Tb-doped AlGaN were studied. The samples were grown on sapphire substrates using OMVPE. Tb implantation was cariied out to introduce Tb into samples. After implantation, samples were annealed at 1000 to 1150 C in 10% NH diluted with N. The luminescence intensity for AlGaN x=0.1 is 5 times stronger than that for x=0 at 14 K. The luminesecence intensity for GaN rapidly decreases with temperature and its activation enegy is 7.8 meV. With increasing Al content, the activation enegy increases, and the activation energy for AlGaN is 70 meV.
Lee, H.-S.*; Okada, Hiroshi*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi; Kawakita, Shiro*; Imaizumi, Mitsuru*; Matsuda, Sumio*
Physica Status Solidi (A), 199(3), p.471 - 474, 2003/10
Times Cited Count:3 Percentile:21.33(Materials Science, Multidisciplinary)no abstracts in English
Okada, Hiroshi*; Fujita, Naoki*; Lee, H.-S.*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi
Journal of Electronic Materials, 32(9), p.L5 - L8, 2003/09
Times Cited Count:1 Percentile:12.39(Engineering, Electrical & Electronic)no abstracts in English
Lee, H.-S.*; Okada, Hiroshi*; Wakahara, Akihiro*; Oshima, Takeshi; Ito, Hisayoshi; Kawakita, Shiro*; Imaizumi, Mitsuru*; Matsuda, Sumio*; Yoshida, Akira*
Journal of Physics and Chemistry of Solids, 64(9-10), p.1887 - 1890, 2003/09
Times Cited Count:12 Percentile:53.9(Chemistry, Multidisciplinary)no abstracts in English
Nakanishi, Yasuo*; Wakahara, Akihiro*; Okada, Hiroshi*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi; Shibata, Tomohiko*; Tanaka, Mitsuhiro*
Physica Status Solidi, 0(7), p.2623 - 2626, 2003/07
In our previous study, it was reported that Eu-doped Nitride semiconductors show luminescence propetires. In this study, we investigate the relationship between luminescence properties and Al composition using AlGaN(0x1). AlGaN were grown using OMVPE. Eu atoms were doped into the samples by ion implantation (200keV). After implantation, the samples were annealed to remove residual damege. Luminescence propreties of the samples were measured using photoluminescence and cathodeluminescence. As a result, luminescence at 621 nm which relates 4f-4f transition were observed for all samples (x=0 to 1). As for intensity, samples with x=0.5 show the strongest luminescence. This result can be interpreted in terms of the internal stress of crystals by the existence of Al atoms.
Nakanishi, Yasuo*; Wakahara, Akihiro*; Okada, Hiroshi*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi; Nakao, Setsuo*; Saito, Kazuo*; Kim, Y. T.*
Nuclear Instruments and Methods in Physics Research B, 206, p.1033 - 1036, 2003/05
Times Cited Count:18 Percentile:74.43(Instruments & Instrumentation)Photo luminescence properties of GaN implanted with Eu ions were studied. The GaN was epitaxialy grown on sapphire substrate. Multiple-implantation at RT was done to form box profile of Eu at a mean Eu concentration from 2.810 to 2.810/cm. Samples were annealed in NH, N at 900-1050C for 5-30 min after implantation. As the result, sharp emission peaks around 621nm which is assigned as 4f-4f transition were observed. The intensity of peaks increases with increasing Eu concentration and saturate at Eu concentrations around 2.810/cm.
Tanaka, Toru*; Yamaguchi, Toshiyuki*; Oshima, Takeshi; Ito, Hisayoshi; Wakahara, Akihiro*; Yoshida, Akira*
Solar Energy Materials and Solar Cells, 75(1-2), p.109 - 113, 2003/01
Times Cited Count:17 Percentile:55.67(Energy & Fuels)Single crystalline CuInSe thin films grown on GaAs were implanted with Cl ions at room temperature. The mean concentration of Cl ranges from 5E17 to 5E19 /cm. Residual defects introduced in implantated layer are removed by annealing at 400C in N. As a result of Hall effects measuremant, electron concentration in implanted layer increases with increasing implanted Cl concentration. This result suggests that Cl acts as donor in CuLnSe. Ionizing energy of Cl is estimated to be 78 meV from the temperature dependence of electron concentation.
Nakanishi, Yasuo*; Wakahara, Akihiro*; Okada, Hiroshi*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi
Physica Status Solidi (C), 0(1), p.461 - 464, 2002/12
no abstracts in English
Nakanishi, Yasuo*; Wakahara, Akihiro*; Okada, Hiroshi*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi
Applied Physics Letters, 81(11), p.1943 - 1945, 2002/09
Times Cited Count:19 Percentile:59.26(Physics, Applied)Eu-doped GaN samples were irradiated with 3MeV-electrons at RT at 10 - 3x10/cm. Photoluminescence (PL) propeties related to D-F in Eu were studied using He-Cd laser as excitation source. As the results, it is found that PL intensity is not affected by electron irradiation.Considering that PL peak related to near-band-edge strongly decreases due to electron irradiation, we can conclude that PL related to D-F in Eu has very strong radiation resistance.
Fujita, Naoki*; Lee, H.-S.*; Okada, Hiroshi*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi
Shingaku Giho, 102(77), p.79 - 84, 2002/05
no abstracts in English
Nakanishi, Yasuo*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi; Sakai, Shiro*
IPAP Conference Series 1 (Proceedings of International Workshop on Nitride Semiconductors), p.486 - 489, 2000/11
no abstracts in English
Tanaka, Toru*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi; Okada, Sohei
Journal of Applied Physics, 87(7), p.3283 - 3286, 2000/01
Times Cited Count:11 Percentile:46.92(Physics, Applied)no abstracts in English
Yoshida, Akira*; Natsume, Satoshi*; Lee, H.-S.*; Okada, Hiroshi*; Wakahara, Akihiro*; Oshima, Takeshi; Ito, Hisayoshi
no journal, ,
CuInSe (CIS)-based thin film solar cells have excellent radiation hardness and are promising in applications in space. However, although CIS thin film is used as an absorption layer in the cell, the details of radiation-induced degradation mechanism are not yet clear. In this report, n-type CIS thin film was fabricated by RF sputtering and was annealed at 823 K together with CuSe film evaporated on the CIS thin film, resulting in p-type CIS thin layer. The electrical properties of p-type CIS thin films were investigated. These films were irradiated with high energy electrons, up to the irradiation fluence 210[1/cm] of electrons accelerated up to 2 MeV. Over 110[1/cm], the resistivity began to increase drastically. The temperature dependence of the resistivity was measured below room temperature down to 20 K. These behaviors are explained by the grain-boundary-dominated transport with the increased barrier energy at the grain boundary.
Oikawa, Fumitake*; Wakahara, Akihiro*; Takemoto, Kazumasa*; Okada, Hiroshi*; Oshima, Takeshi; Ito, Hisayoshi
no journal, ,
no abstracts in English