KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Settings

Author: search.filters.author.Khunkhao, S.Subject: search.filters.subject.Optical sensor

Search Results

Now showing 1 - 2 of 2
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    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.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    On laterally spreading of space-charge-region in planar metal-semiconductor-metal structures
    (2003-10-01)
    Khunkhao, S.
    ;
    Yasumura, Y.
    ;
    Kitagawa, K.
    ;
    Masui, T.
    ;
    Sato, K.
    Lateral spreading along the surface of space-charge-region (SCR) of planar metal-semiconductor-metal (MSM) structures has been investigated. Planar MSM structures have been attracted much attention as viable optical sensor structures. For this purpose, the SCR of such a structure plays a key role in generating photocurrent and thus, in dc (static) and/or low frequency scheme, the wider SCR along the active surface is the better from the efficiency point of view. To study the spreading properties of the SCR along the surface of MSM structures, we prepared planar MSM structures leaving the undepleted region between the electrodes. We examined their SCR spreading through the photocurrent-bias voltage characteristics. The experimental results were compared with the numerical simulation using a quasi-1D (one-dimensional) model of such a planar structure. It was found that the change in the photocurrents is proportional to the square root of the bias applied, implying that the current varies with the lateral spreading of the SCR. Further, the value of the surface spreading of the SCR might be roughly equal to the results predicted from the numerical simulation. These results also suggest that the effective photocurrent generation is occurring principally at the very surface of the SCR. © 2003 Elsevier Ltd. All rights reserved.