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Access type: UnknownAuthor: search.filters.author.Yamashita, Kyohei

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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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    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.
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    Effects of hydrogen passivation on near-infrared photodetection of n-type β-FeSi2/p-type si heterojunction photodiodes
    (2012-10-01)
    Promros, Nathaporn
    ;
    Yamashita, Kyohei
    ;
    Iwasaki, Ryuhei
    ;
    Yoshitake, Tsuyoshi
    Hydrogen passivation was applied to the initial epitaxial growth of n-typeβ-FeSi2 thin films on p-type Si(111) substrates. Such passivation was applied at different gas inflow H2/Ar ratios ranging from 0 to 1.0. The photodetection performance of the photodiode fabricated at the optimum ratio of 0.2 was markedly improved as compared with those of the other samples. The quantum efficiency and detectivity were 2.08% and 5.40×109 cm Hz1=2/W-1, respectively. The enhanced photodetective performance should be mainly because dangling bonds that act as trap centers for photocarriers are effectively inactivated by the passivation. © 2012 The Japan Society of Applied Physics.