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Author: search.filters.author.Niemcharoen, S.Subject: search.filters.subject.Shot noise

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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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    White noise due to photocurrents in planar MSM structures on low-resistivity Si
    (2003-10-01)
    Khunkhao, S.
    ;
    Niemcharoen, S.
    ;
    Supadech, S.
    ;
    Sato, K.
    The noise due to photocurrent at low frequencies (3-100 kHz) has been observed of planar aluminum/n-type silicon/aluminum (Al/n-Si/Al) structures based on low-resistivity silicon. It was found that these structures exposed to illumination showed much lower noise than the full shot noise above 5 kHz under a certain operating condition. If the current noise power spectrum is expressed as S(ω) = 2eI<inf>p</inf>Γ<sup>2</sup>, where e is the electronic charge and I<inf>p</inf> is the photocurrent, the noise ratio Γ<sup>2</sup> lies between 0.2 and 1.0, depending on the bias voltage. These results are attributed to the planar structures of the samples having wide electrode separation. Spatially uniform carrier generation due to illumination at the active surface and the decrease in the cross-correlation between the current components in the structure might be playing the key role to reduce the noise to lower levels than that of full shot noise under a certain operating condition. © 2003 Elsevier Ltd. All rights reserved.
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    Observation of photoinduced shot noise in planar Mo/n-Si/Mo structures with undepleted region
    (2002-04-01)
    Niemcharoen, S.
    ;
    Ando, T.
    ;
    Supadech, S.
    ;
    Yasumura, Y.
    ;
    Sato, K.
    Measurements of low frequency shot noise due to photoinduced currents have been carried out on planar molybdenum/n-type silicon/molybdenum structures having long neutral region and Schottky barriers at both ends. Measurements were performed in the frequency range between 1 and 200 kHz at room temperature. The observed shot noise was found to be lower than the level of full shot noise. That is, when the current noise is expressed as S(ω) = 2qIΓ<sup>2</sup> (q, the electronic charge; I, the average current), the noise factor, Γ<sup>2</sup>, was estimated to be around 0.9, which is smaller than unity corresponding to so-called full shot noise. These results are attributed to the decay of autocorrelation effect in the current component photoinduced in the neutral region. © 2002 Elsevier Science Ltd. All rights reserved.