Abderrahmane, A.*; Ko, P. J.*; Okada, Hiroshi*; Sato, Shinichiro; Oshima, Takeshi; Shibasaki, Ichiro*; Sandhu, A.*
IEEE Electron Device Letters, 35(12), p.1305 - 1307, 2014/12
Tolerance of AlInSb/InAsSb/AlInSb heterostructures quantum-well-based micro-Hall sensors against proton irradiation of 380 keV and proton fluence in the range 10 and 10 (proton/cm) is reported. Defects and deep levels induced by proton irradiation into the heterostructures caused decreases in the mobility of the micro-Hall sensors. Degradation of the magnetic sensitivity started at a proton fluence of 10 (proton/cm) and continued with increasing proton fluence. The variation of the micro-Hall sensors sensitivity was minimal in low doped AlInSb/InAsSb/AlInSb heterostructure quantum wells. These micro-Hall sensors were operable even at proton fluence of 10 (proton/cm), which makes these devices suitable for space applications with lifetime of thousands of years in the outer space.
Abderrahmane, A.*; Ko, P. J.*; Okada, Hiroshi*; Sato, Shinichiro; Oshima, Takeshi; Sandhu, A.*
IEEE Electron Device Letters, 35(11), p.1130 - 1132, 2014/11
The longitudinal and transverse magnetoresistances of AlGaN/GaN heterostructure-based micro-Hall sensors were compared with samples irradiated with protons with an energy of 380 keV and fluence of 10 (protons/cm). Increases in the elastic and inelastic scattering were deduced from weak localization behavior in both samples. The AlGaN/GaN micro-Hall sensors showed stable magnetic sensitivity in non and irradiated samples and increased resistivity after proton irradiation yielded an enhanced magnetoresistance sensitivity in nonirradiated sensors from 160 to 417 V/(A T). The minimum detectable magnetic field of irradiated micro-Hall sensors determined from magneto-voltage measurements at 4 K was similar to the minimum detectable magnetic field in the nonirradiated sensors.
Abderrahmane, A.*; Takahashi, Hiroki*; Tashiro, Tatsuya*; Ko, P. J.*; Okada, Hiroshi*; Sato, Shinichiro; Oshima, Takeshi; Sandhu, A.*
AIP Conference Proceedings 1585, p.123 - 127, 2014/02
The effect of annealing at 673 K on irradiated micro-Hall sensors irradiated with protons at 380 keV and fluences of 1 cm, 1 cm, 1 cm is reported. Cathodoluminescence measurements were carried out at room temperature before and after annealing and showed improvement in the band edge band emission of the GaN layer. After annealing a sensor irradiated by 1 cm the device became operational with improvements in its magnetic sensitivity. All irradiated sensors showed improvement in their electrical characteristics after annealing.
Abderrahmane, A.*; Tashiro, Tatsuya*; Takahashi, Hiroki*; Ko, P. J.*; Okada, Hiroshi*; Sato, Shinichiro; Oshima, Takeshi; Sandhu, A.*
Applied Physics Letters, 104(2), p.023508_1 - 023508_4, 2014/01
The effect of annealing on the magnetoelectrical properties of proton-irradiated micro-Hall sensors at an energy of 380 keV and very high proton fluences was studied. Recovery of the electron mobility and a decrease in the sheet resistance of the annealed micro-Hall sensors, as well as an enhancement in their magnetic sensitivity were reported. Trap removal and an improvement in the crystal quality by removing defects were confirmed through current-voltage measurements and Raman spectroscopy, respectively.
Abderrahmane, A.*; Koide, Shota*; Okada, Hiroshi*; Takahashi, Hiroki*; Sato, Shinichiro; Oshima, Takeshi; Sandhu, A.*
Applied Physics Letters, 102(19), p.193510_1 - 193510_4, 2013/05
The magnetoelectric properties of AlGaN/GaN micro-Hall effect sensors were studied after 380 keV proton irradiation. After irradiation the current-voltage measurements, stability of the magnetic sensitivity of the sensors, and the sheet electron density were degraded with a dramatic decrease of the electron mobility at high temperatures. Raman spectroscopy showed a degradation in the crystalline quality of GaN crystal, but there was no change in the strain.
Abderrahmane, A.*; Koide, Shota*; Tahara, Tomoyuki*; Sato, Shinichiro; Oshima, Takeshi; Okada, Hiroshi*; Sandhu, A.*
Journal of Physics; Conference Series, 433, p.012011_1 - 012011_8, 2013/04
We investigated the effect of high energy and high fluence proton irradiation on magnetoelectric properties of AlGaN/GaN micro-Hall sensors from 5.4 K to room temperature. The sensors show good resistance versus the irradiation translated by the stability of the sheet density therefore the stability of the absolute sensitivity of the sensor. However, the proton irradiation damaged the electrical properties of the sensor indicated by the dramatically decrease of the mobility at low temperature by rate of about 81% at 5.4 K. The existing of the 2DEG system either after irradiation with high energy was confirmed by investigation the magnetotransport measurements at low temperature and which show Shubnikov de Haas oscillations at high magnetic field. Damping of the Shubnikov de Haas oscillations and disappearance of Landau plateaus after irradiation were related to the degradation in the mobility causing by increasing the scattering at the interface.
Abderrahmane, A.*; Koide, Shota*; Sato, Shinichiro; Oshima, Takeshi; Sandhu, A.*; Okada, Hiroshi*
IEEE Transactions on Magnetics, 48(11), p.4421 - 4423, 2012/11
Recent industrial trends indicate increasing demand for Hall effect sensors for monitoring magnetic fields under extreme conditions such as high temperatures and under harmful radiation conditions. In this study, robust and high sensitivity Hall effect sensors using AlGaN/GaN heterostructures with a two-dimensional electron gas at the heterointerface were fabricated, and their magnetic properties were investigated. The AlGaN/GaN 2DEG Hall sensors were stable to at least 400 C and even after irradiation of 380 keV protons at the fluence of 1 10 /cm. The results showed that the AlGaN/GaN 2DEG Hall sensors had superior radiation tolerance to AlGaAs/GaAs and AlInSb/InAsSb/AlInSb magnetic sensors.
Okada, Hiroshi*; Abderrahmane, A.*; Koide, Shota*; Takahashi, Hiroki*; Sato, Shinichiro; Oshima, Takeshi; Sandhu, A.*
Journal of Physics; Conference Series, 352, p.012010_1 - 012010_5, 2012/03
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
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.
Takahashi, Shinya*; Inoue, Takanobu*; Tsushima, Koji*; Sakioka, Masamichi*; Matsunaga, Takeshi
Kankyo Kogaku Kenkyu Rombunshu, 46, p.565 - 572, 2009/00
This study analyzed the changes of water quality during rain events at Ijira river, a mountain stream in Gifu Prefecture, by measured the major ion concentration, pH, electric conductivity, discharge, and hydrograph separation using deuterium isotope ratio of the water. During rain events, where the discharge is increase, almost all of the major ion concentration, pH and electric conductivity were decreased. We also found that the correlation of the changes of pH and the changes of electric conductivity with precipitation were negative. The result of hydrograph separation shows that the ratio of surface runoff for discharge is increased with an increased of the precipitation, and also increased in the high precipitation. It was shown that the major factor of the changes of water quality in this study site is the contribution of surface runoff.
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
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.
Matsunaga, Takeshi; Tsuzuki, Katsunori; Yanase, Nobuyuki; Hanzawa, Yukiko; Naganawa, Hirochika; Inoue, Takanobu*; Yamada, Toshiro*; Miyata, Akifumi*
Proceedings of International Symposium on Environmental Modeling and Radioecology, p.243 - 246, 2007/03
The aim of this work is to obtain a fundamental scheme of stream discharge of inorganic toxic materials derived from Characteristics of the stream discharge of metallic elements were investigated in two forested catchments in the Oda River and the Ijira River watersheds. Precipitations, stream water and soil water samples were collected in raining events and were analyzed for inorganic elements, dissolved organic carbon and isotopic abundance of deuterium. Results revealed an accelerated discharge of specific metals of Cu, Sb and Cr and all the studied REE in dissolved form. This feature was commonly found in the two catchments. The specific metals are strongly suspected to be of anthropogenic origin. An analysis of hydrological discharge, using chemical and isotopic tracers, suggested that the increased discharge of the metals originate from their deposits on the ground surface and/or instantaneous resuspension of stream sediment. Contrary, REE discharge was tightly coupled with that of dissolved humic substances.
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
no abstracts in English
Okada, Hiroshi*; Natsume, Satoshi*; Wakahara, Akihiro*; Yoshida, Akira*; Oshima, Takeshi; Kamiya, Tomihiro
Proceedings of 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
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
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
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
no abstracts in English