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Author: search.filters.author.Funasaki, SuguruSubject: search.filters.subject.Heterojunction

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    Temperature dependent current-voltage characteristics of n-type nanocrystalline-FeSi2/p-type Si heterojunctions fabricated by pulsed laser deposition
    (2014-01-08)
    Promros, Nathaporn
    ;
    Iwasaki, Ryuhei
    ;
    Funasaki, Suguru
    ;
    Yamashita, Kyohei
    ;
    Li, Chen
    n-Type NC-FeSi<inf>2</inf>/p-type Si heterojunctions were successfully fabricated by PLD, and their forward current-voltage characteristics were analyzed on the basis of thermionic emission theory (TE) in the temperature range from 300 down to 77 K. With a decrease in the temperature, the ideality factor was increased while the zero-bias barrier height was decreased. The calculated values of ideality factor and barrier height were 3.07 and 0.63 eV at 300 K and 10.75 and 0.23 eV at 77 K. The large value of ideality factor indicated that a tunneling process contributes to the carrier transport mechanisms in the NC-FeSi<inf>2</inf> films. The series resistance, which was estimated by Cheung's method, was strongly dependent on temperature. At 300 K, the value of series resistance was 12.44 Ω and it was dramatically enhanced to be 1.71× 10<sup>5</sup> Ω at 77 K. © (2014) Trans Tech Publications, Switzerland.
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    Fabrication of mesa structural n-type nanocrystalline-FeSi2/p-type Si heterojunction photodiodes by liftoff technique combined with photolithography
    (2013-12-01)
    Funasaki, Suguru
    ;
    Promros, Nathaporn
    ;
    Iwasaki, Ryuhei
    ;
    Takahara, Motoki
    ;
    Shaban, Mahmoud
    Mesa structural n-type nanocrystalline (NC) FeSi<inf>2</inf>/p-type Si heterojunctions were fabricated by a liftoff technique combined with photolithography in order to improve the diode performance, particularly to reduce the parasitic capacitance. Their current-voltage characteristics were experimentally studied in the dark and under illumination using a 1.31 μm laser at room temperature. Their junction capacitance density and leakage current density were evidently reduced as compared with those of the normal structural diodes. The mesa diode exhibits a good rectifying action with a rectification ratio of approximately three orders of magnitude at bias voltages of ±1 V. The photodetection was clearly observed owing to the suppression in the dark current. The estimated detectivity is 2.0 × 10<sup>9</sup> cm√Hz/W at zero bias, which is an order of magnitude larger than that of the normal structural diodes. This should be because the formation of interface states is reduced accompanied by the interface area reduction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Current transport mechanism of n-type nanocrystalline FeSi2/intrinsic si/p-type si heterojunctions fabricated by facing-targets direct-current sputtering
    (2013-10-29)
    Promros, Nathaporn
    ;
    Funasaki, Suguru
    ;
    Iwasaki, Ryuhei
    ;
    Yoshitake, Tsuyoshi
    N-Type nanocrystalline FeSi<inf>2</inf>/intrinsic Si/p-type Si heterojunctions were successfully fabricated by FTDCS and their forward current-voltage characteristics at low temperatures were analyzed on the basis of thermionic emission theory. The analysis of J-V characteristics exhibits an increase in the ideality factor and a decrease in the barrier height at low temperatures. The values of ideality factor were estimated to be 2.26 at 300 K and 9.29 at 77 K. The temperature dependent ideality factor together with the constant value of parameter A indicated that a trap assisted multistep tunneling process is the dominant carrier transport mechanism in this heterojunction. At high voltages, the current transport mechanism is dominated by SCLC process. © (2013) Trans Tech Publications, Switzerland.
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    Characterizations of mesa structural near-infrared n-type nanocrystalline-FeSi2/p-type si heterojunction photodiodes at low temperatures
    (2013-10-04)
    Promros, Nathaporn
    ;
    Iwasaki, Ryuhei
    ;
    Funasaki, Suguru
    ;
    Yamashita, Kyohei
    ;
    Yoshitake, Tsuyoshi
    In order to reduce the parasitic capacitance, mesa structural n-type NC-FeSi<inf>2</inf>/p-type Si heterojunctions were fabricated by photolithography. Their current-voltage characteristics were measured in the dark and under illumination using a 1.31 μm laser in the temperature range of 60 - 300 K. Their junction capacitance density was evidently reduced as compared with that of the normal structural diodes. The dark current was markedly reduced with a decrease in the temperature. At 60 K, a rectifying current ratio in the dark became more than five orders of magnitude at ±1V. The ratio of the photocurrent to the dark current was dramatically enhanced to be approximately two orders of magnitude, and the detectivity was calculated to be 1.5 × 10<sup>11</sup> cmHz<sup>1/2</sup>/W at -1V. The obtained results showed a remarkable improvement in the device performance as compared with those at 300 K. © (2013) Trans Tech Publications, Switzerland.