Papers by Keyword: Charge Collection Efficiency

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Authors: Alexander M. Ivanov, Evgenia V. Kalinina, Nikita B. Strokan, Alexander A. Lebedev
Abstract: The spectrometric characteristics of detectors based on 4H-SiC films with ion-doped p+–n junctions in a temperature range from 25 to 375 °C have been studied. The experiments with 5.8-MeV α-particles in a high-temperature chamber were performed. The interference factors of the detectors operation in a mode of spectrometry are established. The energy resolution of 1.35% is received. An increase of the efficiency of the diffusion–drift charge transport with increasing temperature has been observed. The last is explained by an increase in the diffusion length of minority carriers.
Authors: Naoya Iwamoto, Shinobu Onoda, Takeshi Ohshima, Kazutoshi Kojima, Atsushi Koizumi, Kazuo Uchida, Shinji Nozaki
Abstract: The effect of electron irradiation on the charge collection efficiency of a 6H-SiC p+n diode has been studied. The diodes were irradiated with electrons of energies from 100 keV to 1 MeV. The charge collection efficiencies of the samples were measured for alpha particles before and after the electron irradiation. The electron irradiation at 100 keV does not affect the charge collection efficiency, while the electron irradiation at 200 keV or higher decreases the charge collection efficiency. The degree of the degradation of the diodes correlates with the energy of the electron irradiation.
Authors: Shinobu Onoda, Naoya Iwamoto, Makoto Murakami, Takeshi Ohshima, Toshio Hirao, Kazu Kojima, K. Kawano, I. Nakano
Abstract: We investigated the energy spectra in p+n 6H-SiC diodes by a wide variety of charged particles with energies up to several hundred MeV. Though Pulse Height Defect (PHD) was detected when the samples were irradiated with high energy heavy ions (322MeV-Kr and 454MeV-Xe), linearity between pulse height (peak channel) and ion energy up to 150MeV was observed.
Authors: Cheol Soon Shon, Ho Kyung Kim, Min Kook Cho, Min Ho Cheong, Chang Hwy Lim, Jung Min Kim
Abstract: We have designed a computational tool for generating X-ray photon spectra for a range of applications both in diagnostic radiology and mammography. As a library, we have adapted the spectral data based on the interpolating polynomials methods by Boone et al [5,6] as well as the computer data files given by Cranley et al [8]. The attenuated spectra for element or compound materials can be calculated based on the mass-attenuation coefficients from NIST (National Institute of Science and Technology), which were also incorporated as a database. Furthermore, a function that a user can generate any filter material by editing the NIST data has been implemented. Parameters related to the beam quality, such as mean photon energy, fluence, exposure, half-value layer (HVL), etc., are considered as important outputs. All of functions and database are integrated in a form of graphical user interface (GUI) by using Microsoft Visual C++TM. This self-developed spectrum-generating code can be usefully served to design X-ray sensors. In this study, we have applied the code to estimate quantum efficiency and charge collection efficiency in various detector materials.
Authors: Kin Kiong Lee, Jamie Steward Laird, Takeshi Ohshima, Shinobu Onoda, Toshio Hirao, Hisayoshi Itoh
Abstract: This paper investigates the transient induced currents by energetic carbon ions in 6H-SiC MOSFETs and the carrier dynamic response due to such a heavy ion collision is simulated by Technology Computer Aided Design (TCAD). It was found that a heavy ion strike induces a bipolar effect on the transistor, whereby the current transients can vary in both polarities. And this has been attributed to the inherent in the MOSFET is a parasitic bipolar junction transistor.
Authors: Takeshi Ohshima, Takahiro Satoh, Masakazu Oikawa, Shinobu Onoda, Shigeomi Hishiki, Toshio Hirao, Toshio Kamiya, T. Yokoyama, A. Sakamoto, R. Tanaka, I. Nakano, Günter Wagner, Hisayoshi Itoh
Abstract: The charge generated in 6H-SiC n+p diodes by gold (Au) ion irradiation at an energy of 12 MeV was evaluated using the Transient Ion Beam Induced Current (TIBIC). The signal peak of the transient current increases, and the fall-time decreases with increasing applied reverse bias. The value of collected charge experimentally obtained is smaller than the ideal value. The Charge Collection Efficiency (CCE) of 6H-SiC n+p diodes irradiated with Au ions is approximately 50 % in spite that the CCE of 100 % is obtained in the case of oxygen (O) ion irradiation.
Authors: Alexander M. Ivanov, Marina G. Mynbaeva, Anton V. Sadokhin, Nikita B. Strokan, Alexander A. Lebedev
Abstract: Nonequilibrium-charge transport has been studied in a structure with a Schottky barrier fabricated on a CVD-grown n-4H-SiC film. The charge introduced by single α-particles was recorded by nuclear spectrometric techniques. The maximum electric field strength in the structure was 1.1 MV/cm. The recorded charge as a function of the reverse bias applied to the structure shows a superlinear rise. Simultaneously, the width of the amplitude spectrum increased superlinearly, too. The observed effect is attributed to the initial stage of impact ionization. The manifestation of the process at unusually low fields (~1.0 MV/cm) is accounted for by specific features of the charge generation process. The carriers generated by a α-particle are found to be originally "heated". The results obtained allow prognostication of the appearance of SiC detectors of the "proportional counter" type in the near future. This is enabled by the advances made in the field of high-voltage electronics in obtaining in practice the required electric field strengths.
Authors: Eketerina Tokareva, Gennadiy Koltsov, Nurnaz Burtebaev, Sergey Didenko, Sergey Legotin, Oleg Rabinovich
Abstract: Using computer programs Elmer FEM Solver for calculating electric fields and Geant4 for the passage simulation of particles through matter, calculations of charge collection efficiency for nuclear radiation matrix detector based on GaAs p-i-n diodes with different distances between pixels 110 microns and 50 microns were made. Based on data obtained detector structure optimization solution, which improves energy resolution, is proposed.
Authors: Alexander M. Ivanov, Nikita B. Strokan, Alexander A. Lebedev, Vitalii V. Kozlovski
Abstract: The effect of a cycle "introduction of defects – annealing – introduction of defects" on the SiC properties has been studied to know the degradation of characteristics of p-n- nuclear radiation detectors. The irradiation with 8 МeV protons at fluences of about 3×1014 сm-2 was used. The annealing was carried out in two stages one-hour at temperatures of 600 and 700 °С. Nuclear spectrometric techniques with 5.8 MeV -particles were employed to test the detectors. The charge collection efficiency and features of the amplitude spectrum were determined to study the capture of charge carriers by radiation-induced defects. Measurements were made in the temperature range of 20–250 °С. It is shown that at 250 °С there is a decrease in the carriers capture. The form of the amplitude spectrum essentially improves. The first irradiation and the subsequent annealing do not change significantly the radiation hardness of SiC. During the second irradiation the effective concentration of the introduced centers is 1.3 times higher. This result may be due to the high total fluence of protons, 6×1014 cm-2.
Authors: Alexander M. Ivanov, Nikita B. Strokan, Alexander A. Lebedev, Vitalii V. Kozlovski
Abstract: P+–n–n+-detector structures based on CVD films with an uncompensated donor concentration of 2×1014 cm-3 have been studied. The p+-region was created by implantation of Al ions. Preliminarily, the detectors were irradiated with 8 MeV protons at a fluence of 3×1014 cm-2 and then annealed in a vacuum at 600°C for 1 h and 700°C for 1 h. Nuclear spectrometric techniques with 5.4 MeV a-particles were employed to test the detectors. In measurements performed in the temperature range 20–150°C, the forward- and reverse-bias modes were compared. It is shown that the annealing leads to a higher collection efficiency of carriers generated by nuclear radiation and to a decrease in the amount of charge accumulated by traps in the course of testing. Despite the positive effect of the annealing, there remains a considerable amount of radiation defects, which is manifested, in particular, in the kinetics of the forward current.
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