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Journal Articles

Development of diagnostic method for deep levels in semiconductors using charge induced by heavy ion microbeams

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:40.75(Instruments & Instrumentation)

Journal Articles

Single event gate rupture in SiC MOS capacitors with different gate oxide thicknesses

Deki, Manato*; Makino, Takahiro; Kojima, Kazutoshi*; Tomita, Takuro*; Oshima, Takeshi

Materials Science Forum, 778-780, p.440 - 443, 2014/02

 Times Cited Count:1 Percentile:60.31

no abstracts in English

Journal Articles

Effects of radiation-induced defects on the charge collection efficiency of a silicon carbide particle detector

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:0.02

Journal Articles

Breakdown voltage in silicon carbide metal-oxide-semiconductor devices induced by ion beams

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:0.05

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 $$^{circ}$$C for 60 min. Circular electrodes with 180 $$mu$$ 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$$^{2}$$/mg, and this value is smaller than that for 18 MeV-Ni (24 MeV cm$$^{2}$$/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.

Journal Articles

Defect-induced performance degradation of 4H-SiC Schottky barrier diode particle detectors

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:27 Percentile:77.13(Physics, Applied)

Journal Articles

$$E_1/E_2$$ traps in 6H-SiC studied with Laplace deep level transient spectroscopy

Koizumi, 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:8 Percentile:38.93(Physics, Applied)

Journal Articles

LET dependence of gate oxide breakdown of SiC-MOS capacitors due to single heavy ion irradiation

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$$_{rm CR}$$) 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$$^{2}$$/mg, respectively), reciprocal value of E$$_{rm CR}$$ 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.

Journal Articles

Peak degradation of heavy-ion induced transient currents in 6H-SiC MOS capacitor

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:60.76

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.

Journal Articles

Defects in an electron-irradiated 6H-SiC diode studied by alpha particle induced charge transient spectroscopy; Their impact on the degraded charge collection efficiency

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:60.76

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$$times$$10$$^{15}$$ /cm$$^{2}$$. Collected charges of the diodes were measured in room temperature using 5.486 MeV alpha particles from $$^{241}$$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$$_{1}$$ and X$$_{2}$$ 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$$_{2}$$ is more critical to the charge collection than X$$_{1}$$.

Journal Articles

Single-alpha-particle-induced charge transient spectroscopy of the 6H-SiC p$$^+$$n diode irradiated with high-energy electrons

Iwamoto, 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:42.62(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Oxygen ion induced charge in SiC MOS capacitors irradiated with $$gamma$$-rays

Oshima, 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:61.2

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 $$gamma$$-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 $$gamma$$-ray irradiation.

Journal Articles

Transient analysis of an extended drift region in a 6H-SiC diode formed by a single alpha particle strike and its contribution to the increased charge collection

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:9 Percentile:62.21(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Charge enhancement effects in 6H-SiC MOSFETs induced by heavy ion strike

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

Journal Articles

Enhanced charge collection in drain contact of 6H-SiC MOSFETs induced by heavy ion microbeam

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

Journal Articles

Time-dependent collected charges of 6H-SiC p$$^+$$n diodes measured using alpha particles

Iwamoto, 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

Journal Articles

Charge collection efficiency of 6H-SiC P$$^{+}$$N diodes degraded by low-energy electron irradiation

Iwamoto, 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 p$$^{+}$$n 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.

Journal Articles

Reduction of effective carrier density and charge collection efficiency in SiC devices due to radiations

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

Journal Articles

Transient response to high energy heavy ions in 6H-SiC n$$^+$$p diodes

Onoda, 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

Journal Articles

Effects of fabrication process on the electrical characteristics of n-channel MOSFETs irradiated with gamma-rays

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.

Journal Articles

Charge collection properties of 6H-SiC diodes by wide variety of charged particles up to several hundreds MeV

Onoda, Shinobu; Iwamoto, Naoya; Murakami, Makoto; Oshima, Takeshi; Hirao, Toshio; Kojima, Kazutoshi*; Kawano, Katsuyasu*; Nakano, Itsuo*

Materials Science Forum, 615-617, p.861 - 864, 2009/00

no abstracts in English

65 (Records 1-20 displayed on this page)