Charge generated in 6H-SiC np diodes by MeV range heavy ions

Oshima, Takeshi; Iwamoto, Naoya; Onoda, Shinobu; Wagner, G.*; Ito, Hisayoshi; Kawano, Katsuyasu*

Surface & Coatings Technology, 206(5), p.864 - 868, 2011/11

https://doi.org/10.1016/j.surfcoat.2011.03.097

Charge induced in np Silicon Carbide (6H-SiC) diodes by heavy ions, oxygen (O), silicon (Si), nickel (Ni), and gold (Au) using a Transient Ion Beam Induced Current (TIBIC) measurement system. The slight increase in collected charge shows in a low bias region, and then, the values are saturated in a high bias region. This indicates that in the low bias region, since the length of the depletion layer is shorter than the ion range, carriers induced in deeper than the depletion layer diffuse and annihilate before they reach the depletion layer. Since the length of the depletion layer increases with increasing bias voltage, the charge collected by diodes increases with increasing bias voltage. In the case of the high bias, the length of the depletion layer is longer than the ion range. As a result, all carriers are induced in the depletion layer, and they can be collected by the electric field. Thus, This indicates that the value of collected charge does not depend on bias voltage. From the point of view of charge collection efficiency (CCE), the collected charge decrease with increasing atomic number. From the calculation, it is found that dense electron-hole pairs were generated in SiC by irradiation of ions with heavy mass. The decrease in the CCE due to ion irradiation with heavy mass can be interpreted in terms of the annihilation of e-h pairs in plasma due to the Auger recombination.

Comparative study of transient current induced in SiC pn and np diodes by heavy ion micro beams

Oshima, Takeshi; Iwamoto, Naoya; Onoda, Shinobu; Kamiya, Tomihiro; Kawano, Katsuyasu*

Nuclear Instruments and Methods in Physics Research B, 267(12-13), p.2189 - 2192, 2009/06

https://doi.org/10.1016/j.nimb.2009.03.056

In this study, pn and np diodes were fabricated on 6H-SiC epitaxial layers. The transient currents induced in these diodes by the incidence of tens MeV range heavy ion micro beams were collected by the Transient Ion Beam Induced Current (TIBIC) measurement system. The value of Charge Collection Efficiency (CCE) for the SiC diodes was obtained by analyzing the transient currents. As a result using 9 MeV-oxygen ions, the CCE value of around 85 % was obtained from both pn and np diodes. Since the CCE value includes non-ionizing energy loss as well as the decay of charge in the measurement system, the obtained CCE value suggests that SiC pn as well as np diodes are suitable for particle detectors. For ion species dependence, the values of CCE for both pn and np diodes decrease with increasing atomic number of incident ions. This decrease in CCE by heavy ion incidence can be interpreted in terms of Auger recombination in dense electron-hole pairs.

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

https://doi.org/10.1063/1.3119984

no abstracts in English

Transient response to high energy heavy ions in 6H-SiC np 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

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.

Transient currents induced in 6H-SiC MOS capacitors by oxygen ion incidence

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.

Charge collection from SiC MOS capacitors irradiated with oxygen ion

Iwamoto, Naoya; Onoda, Shinobu; Oshima, Takeshi; Kojima, Kazutoshi*; Kawano, Katsuyasu*

Proceedings of the 8th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-8), p.191 - 194, 2008/12

no abstracts in English

Decrease of charge collection due to displacement damage by rays in a 6H-SiC diode

Onoda, Shinobu; Oshima, Takeshi; Hirao, Toshio; Mishima, Kenta; Hishiki, Shigeomi; Iwamoto, Naoya; Kojima, Kazutoshi*; Kawano, Katsuyasu*

IEEE Transactions on Nuclear Science, 54(6), p.1953 - 1960, 2007/12

https://doi.org/10.1109/TNS.2007.910203

Degradation modeling of InGaP/GaAs/Ge triple junction solar cells irradiated with various energy protons

Sato, Shinichiro; Miyamoto, Haruki; Imaizumi, Mitsuru*; Shimazaki, Kazunori*; Morioka, Chiharu*; Kawano, Katsuyasu*; Oshima, Takeshi

Proceedings of 17th International Photovoltaic Science and Engineering Conference (PVSEC-17) (CD-ROM), p.502 - 503, 2007/12

Degradation modeling of InGaP/GaAs/Ge triple junction (3J) solar cells with the use of a one dimensional optical device simulator, PC1D, is performed for cell lifetime prediction. By fitting the quantum efficiencies of 3J solar cells degraded by 30 keV, 150 keV, 3 MeV, or 10 MeV proton irradiation, the short circuit currents (Isc) and open circuit voltages (Voc) are simulated. The damage coefficient of minority carrier diffusion length () and carrier removal rate () of base carrier concentration of each sub cell are also estimated. The values of Isc and Voc obtained using the calculations show good agreement with experimental values. These results confirm that the degradation modeling method is effective for lifetime prediction of 3J solar cells.

Reconsideration of electron irradiation test methods for the evaluation of space solar cells

Oshima, Takeshi; Sato, Shinichiro; Miyamoto, Haruki; Imaizumi, Mitsuru*; Hanaya, Hiroaki; Kawano, Katsuyasu*

Proceedings of 17th International Photovoltaic Science and Engineering Conference (PVSEC-17) (CD-ROM), p.955 - 956, 2007/12

In this study, we reconsider electron irradiation methods for the evaluation of radiation response of space solar cells. We show irradiation test methods performed at JAEA, such as a sequential method, in which the electrical performance of solar cells is measured outside of an irradiation facility after irradiation, and a simultaneous method, in which the electrical performance of solar cells can be measured in-situ. The results obtained from the sequential method are compared to these obtained from the simultaneous method. The reasonable distance between samples and the accelerator window to take reliable data on the basis of the energy decay of electrons by atmosphere is also discussed.