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Author: search.filters.author.Khunkhao, S.Subject: search.filters.subject.Photocurrent control

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    White noise in silicon-based planar metal-semiconductor-metal photodiodes
    (2008-10-06)
    Khunkhao, S.
    ;
    Nanthivatana, P.
    ;
    Niemcharoen, S.
    ;
    Titiroongruang, W.
    ;
    Sato, K.
    Low-frequency 3-100 kHz shot noise (white noise) emerging from photoinduced current in Mo/n-Si/Mo structures leaving undepleted region has been observed under different bias and optical intensity conditions. The measurements revealed that the current noise observed depends not only on the illumination intensity levels but also on bias voltage. The current noise observed is expressed as S(ω)=2IΓ<sup>2</sup> and analyzed, where I and Γ<sup>2</sup> is the average current and noise factor, respectively. The measurements reveal that Γ<sup>2</sup> has strong bias dependence, lying Γ<sup>2</sup>- 0.01 to about unity corresponding to simple shot noise. Such experimental results are explained, stating that the reduction of cross correlation between drift and diffusion currents and autocorrelation of drift current component determining the level of noise occurs with decrease in SCR width bias-dependent. To explain the behavior of observed noise more properly, we propose, in addition to the mechanisms above, that the reduction in autocorrelation effect of each current component plays an important role to decrease the relevant noise to such extremely low levels. © 2008 IEEE.
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    Photosensing properties of interdigitated metal-semiconductor-metal structures with undepleted region
    (2003-08-01)
    Masui, T.
    ;
    Khunkhao, S.
    ;
    Kobayashi, K.
    ;
    Niemcharoen, S.
    ;
    Supadech, S.
    We previously reported that it is possible to achieve bias-controllable photocurrent characteristics using planar metal-semiconductor-metal (MSM) structures with depleted and undepleted regions at the active area under optical illumination. To make the structures of this type more sensitive to dc and/or ac optical quantities, interdigitated Schottky-barrier MSM (SB-MSM) structures for visible range having voltage-controllable iris function have been fabricated and examined. By introducing an undepleted region between Schottky barriers on both sides, the depleted region width at the front surface under illumination varies with bias applied, where this region would be more sensitive to optical quantity than the undepleted region to generate the photocurrent. Making use of planar molybdenum n-type silicon molybdenum (Mo/n-Si/Mo) structures, it has been experimentally demonstrated that such a structure exhibits voltage controllability of photocurrents whilst maintaining the inherent function converting optical signal into electronic signal. An appreciable improvement in obtaining output photocurrent was confirmed from both dc and low frequency (1-20) kHz signal measurements. It was found that the experimental results are substantially explained by the simplified model of this structure. © 2003 Elsevier Science Ltd. All rights reserved.