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Kada, Wataru*; Kambayashi, Yuya*; Iwamoto, Naoya*; Onoda, Shinobu; Makino, Takahiro; Koka, Masashi; Kamiya, Tomihiro; Hoshino, Norihiro*; Tsuchida, Hidekazu*; Kojima, Kazutoshi*; et al.
Nuclear Instruments and Methods in Physics Research B, 348, p.240 - 245, 2015/04
Times Cited Count：4 Percentile：30.80(Instruments & Instrumentation)Deki, Manato*; Makino, Takahiro; Kojima, Kazutoshi*; Tomita, Takuro*; Oshima, Takeshi
Materials Science Forum, 778-780, p.440 - 443, 2014/02
Times Cited Count：4 Percentile：80.53(Crystallography)no abstracts in English
Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Nozaki, Shinji*
Proceedings of SPIE, Vol.8725 (CD-ROM), 8 Pages, 2013/06
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)Oshima, Takeshi; Deki, Manato; Makino, Takahiro; Iwamoto, Naoya; Onoda, Shinobu; Hirao, Toshio*; Kojima, Kazutoshi*; Tomita, Takuro*; Matsuo, Shigeki*; Hashimoto, Shuichi*
AIP Conference Proceedings 1525, p.654 - 658, 2013/04
Times Cited Count：0 Percentile：0.00(Physics, Applied)Metal-Oxide-Semiconductor (MOS) capacitors were fabricated on n-type 4H-SiC epitaxial layers, and the leakage current through the gate oxide during heavy ion irradiation was investigated in order to evaluate dielectric breakdown induced by heavy ions (Single Event Gate Rupture: SEGR). The gate oxide at thickness ranges between 60 and 80 nm was formed using pyrogenic oxidation at 1100 
C for 60 min. Circular electrodes with 180 
diameter were formed using Al evaporation and a lift-off technique. The leakage current observed through the gate oxide was monitored during 18 MeV oxygen (O) or nickel (Ni) ions. As a result, although no significant difference in the value of the electric field at the dielectric breakdown (around 8.2 MV/cm) was observed between non-irradiated and 18 MeV-O irradiated samples, the value decreased to be 7.3 MV/cm in the case of 18 MeV-Ni ion incidence. The Linier Energy Transfer (LET) for 18 MeV-O is 7 MeV cm
/mg, and this value is smaller than that for 18 MeV-Ni (24 MeV cm/mg). Also, 18 MeV-Ni ions deposit energy in narrower regions than 18 MeV-O ions. Thus, it can be concluded that the high density of charge induced by 18 MeV-Ni ions triggers SEGR in SiC MOS capacitors.
Iwamoto, Naoya; Johnson, B. C.; Hoshino, Norihiro*; Ito, Masahiko*; Tsuchida, Hidekazu*; Kojima, Kazutoshi*; Oshima, Takeshi
Journal of Applied Physics, 113(14), p.143714_1 - 143714_5, 2013/04
Times Cited Count：34 Percentile：76.30(Physics, Applied)
traps in 6H-SiC studied with Laplace deep level transient spectroscopyKoizumi, Atsushi*; Markevich, V. P.*; Iwamoto, Naoya; Sasaki, Sho*; Oshima, Takeshi; Kojima, Kazutoshi*; Kimoto, Tsunenobu*; Uchida, Kazuo*; Nozaki, Shinji*; Hamilton, B.*; et al.
Applied Physics Letters, 102(3), p.032104_1 - 032104_4, 2013/01
Times Cited Count：12 Percentile：42.62(Physics, Applied)Deki, Manato; Makino, Takahiro; Tomita, Takuro*; Hashimoto, Shuichi*; Kojima, Kazutoshi*; Oshima, Takeshi
Proceedings of 10th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-10) (Internet), p.78 - 81, 2012/12
Metal-Oxide-Semiconductor (MOS) capacitors fabricated on Silicon Carbide (SiC) under applied biases were irradiated with heavy ions. The relationship between critical electric field (E
) and Linear Energy Transfer (LET) was investigated. As a results of 9 MeV-Ni, 18 MeV-Ni, Kr-322 MeV and 454 MeV-Xeirradiation (the values of LET are 14.6, 23.8, 42.2 and 73.2 MeV cm/mg, respectively), reciprocal value of E increases with increasing LET. The similar relationship was also reported Si MOS capacitors. However, the increase in SiC MOS capacitors is smaller than that in Si ones because the generation energy of one electron-hole pair for SiC is larger than that for Si.
Makino, Takahiro; Iwamoto, Naoya*; Onoda, Shinobu; Oshima, Takeshi; Kojima, Kazutoshi*; Nozaki, Shinji*
Materials Science Forum, 717-720, p.469 - 472, 2012/05
Times Cited Count：1 Percentile：52.58(Materials Science, Multidisciplinary)The peak amplitude of ion induced transient current in n-type 6H-SiC MOS capacitors decreased as the number of incident ions increased and the decrease was recovered to the initial value by applying a positive bias at +1 V. In addition, we monitored a change in the capacitance for the MOS capacitors during ion irradiation. The capacitances increase as the number of incident ion increase. Thus, the result obtained in this study indicates that the depletion layer decreased as the increasing number of incident ions and saturated. Since the number of incident ions at the peak current saturation corresponds to the saturation of the capacitance, we can conclude that the decrease in peak current comes from the decrease in the depletion layer. In addition, the generation of electron-hole pairs by incident ion may result in the formation of an inversion layer. This would have the effect of shielding the charge carriers from the applied bias further reducing the depletion layer width.
Iwamoto, Naoya*; Koizumi, Atsushi*; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Koike, Shumpei*; Uchida, Kazuo*; Nozaki, Shinji*
Materials Science Forum, 717-720, p.267 - 270, 2012/05
Times Cited Count：1 Percentile：52.58(Materials Science, Multidisciplinary)In this study, we carried out an attempt to identify the defects responsible for the degraded charge collection efficiency of the 6H-SiC p
n diode irradiated with 1 MeV electrons by the alpha particle induced charge transient spectroscopy. To form defects in the SiC crystal, one of the diodes was irradiated with 1 MeV electrons at a fluence of 1
10
/cm. Collected charges of the diodes were measured in room temperature using 5.486 MeV alpha particles from 
Am source. After the electron irradiation, the collected charge of the diode at a reverse bias of 100 V decreased to 84% of its initial value. In order to investigate the relationship between degradation of collected charge and defects in detail, time-dependent collected charges of the diodes were measured in temperature ranges from 170 K to 310 K. As a result, two distinct peaks labeled X
and X
are found for the electron-irradiated diode, and their activation energies are estimated to be 0.30 and 0.47 eV, respectively. These two peaks are considered to correspond to the defect levels introduced by the electron irradiation. In particular, when the diodes are used in room temperature, X is more critical to the charge collection than X.
n diode irradiated with high-energy electronsIwamoto, Naoya; Koizumi, Atsushi*; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Koike, Shumpei*; Uchida, Kazuo*; Nozaki, Shinji*
IEEE Transactions on Nuclear Science, 58(6), p.3328 - 3332, 2011/12
Times Cited Count：5 Percentile：37.02(Engineering, Electrical & Electronic)no abstracts in English
-raysOshima, Takeshi; Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Nozaki, Shinji*; Kojima, Kazutoshi*
Materials Science Forum, 679-680, p.362 - 365, 2011/03
Times Cited Count：1 Percentile：55.58(Engineering, Multidisciplinary)Charge induced in the 6H-Silicon Carbide (SiC) n Metal-Oxide-Semiconductor (MOS) capacitors by 15 MeV oxygen ion microbeams was evaluated using Transient Ion Beam Induced Current (TIBIC) before and after -ray irradiations. With increasing number of incident ions, the peak height of TIBIC signals decreases and the fall time increases. The decrease in TIBIC peak finally saturated. The peak height of the TIBIC signal can be refreshed to its original shape by applying a positive bias of + 1V to the oxide electrode. This result can be explained in terms of the existence of deep hole traps. Small decrease in both TIBIC signal peak and collected charge was observed due to -ray irradiation.
Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Koizumi, Atsushi*; Uchida, Kazuo*; Nozaki, Shinji*
IEEE Transactions on Nuclear Science, 58(1), p.305 - 313, 2011/02
Times Cited Count：10 Percentile：58.96(Engineering, Electrical & Electronic)no abstracts in English
Onoda, Shinobu; Makino, Takahiro; Iwamoto, Naoya*; Vizkelethy, G.*; Kojima, Kazutoshi*; Nozaki, Shinji*; Oshima, Takeshi
IEEE Transactions on Nuclear Science, 57(6), p.3373 - 3379, 2010/12
no abstracts in English
Onoda, Shinobu; Vizkelethy, G.*; Makino, Takahiro; Iwamoto, Naoya; Kojima, Kazutoshi*; Nozaki, Shinji*; Oshima, Takeshi
Proceedings of 9th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-9), p.230 - 233, 2010/10
n diodes measured using alpha particlesIwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Koizumi, Atsushi*; Uchida, Kazuo*; Nozaki, Shinji*
Proceedings of 9th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-9), p.222 - 225, 2010/10
N diodes degraded by low-energy electron irradiationIwamoto, Naoya; Onoda, Shinobu; Oshima, Takeshi; Kojima, Kazutoshi*; Koizumi, Atsushi*; Uchida, Kazuo*; Nozaki, Shinji*
Materials Science Forum, 645-648, p.921 - 924, 2010/00
Electron irradiation effects on the charge collection efficiency (CCE) of the 6H-SiC pn diodes were investigated. The diodes were irradiated with electrons at energies from 100 keV to 1 MeV. The value of CCE of the diodes using alpha particles compared before and after the electron irradiations. In the case of 100 keV electron, no significant change in CCE was observed. On the other hand, above 200 keV, the values of CCE decreased with increasing fluence. The degradation was larger with increasing incident electron energy.
Onoda, Shinobu; Iwamoto, Naoya; Hirao, Toshio; Kawano, Katsuyasu*; Kojima, Kazutoshi*; Oshima, Takeshi
AIP Conference Proceedings 1099, p.1010 - 1013, 2009/03
no abstracts in English
p diodesOnoda, Shinobu; Oshima, Takeshi; Hirao, Toshio; Hishiki, Shigeomi; Iwamoto, Naoya; Kojima, Kazutoshi*; Kawano, Katsuyasu*
Materials Science Forum, 600-603, p.1039 - 1042, 2009/00
no abstracts in English
Iwamoto, Naoya; Onoda, Shinobu; Oshima, Takeshi; Kojima, Kazutoshi*; Kawano, Katsuyasu*
Materials Science Forum, 615-617, p.517 - 520, 2009/00
Single event transient currents induced in 6H-SiC Metal-Oxide-Semiconductors (MOS) capacitors by using oxygen ions are investigated. Charges collected from the MOS capacitors are estimated by the integration of transient currents. Applying the drift-diffusion model to the collected charges, the diffusion length of electron is estimated. Transient currents induced in the -ray irradiated MOS capacitors are also investigated. No significant change in the transient currents is observed after -ray irradiation.
Hishiki, Shigeomi; Iwamoto, Naoya; Oshima, Takeshi; Ito, Hisayoshi; Kojima, Kazutoshi*; Kawano, Katsuyasu*
Materials Science Forum, 600-603, p.707 - 710, 2009/00
The n-channel 6H-SiC MOSFETs were fabricated using different process. The carbon-coated MOSFETs showed higher radiation resistance than non-coated ones. The generation of interface traps for carbon-coated MOSFETs was smaller than that for non-coated MOSFETs. This origin can be interptered in terms of the surface degradation by thermal annealing process after ion implantation.
