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Subject: search.filters.subject.Photocurrent control

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    Photocurrent enhancement between two coplanar schottky-barriers on silicon MSM photodetector
    (2013-06-03)
    Atiwongsangthong, Narin
    ;
    Niemcharoen, Surasak
    Gain properties of dc and ac photocurrent generated between two Schottky barriers coplanarly placed on silicon metal-semiconductor-metal photodetector have been investigated experimentally. The test structure has two square Mo/n-Si Schottky barrier junctions on an n-type silicon substrate with a resistivity of 9-12 Ω-cm and the junction internal separation is 20μm. The current-voltage (I-V) characteristics under illumination in visible range showed a rapid increase in the photocurrent at higher bias region. From the I-V characteristics and noise measurements, increase in photocurrent was ascribed to avalanche multiplication of carriers photogenerated in the reverse-biased Schottky junction. From observation of optical signal demodulation at low frequencies (10 kHz and 50 kHz), it was found that multiplication factor larger than 100 at 10 kHz and 30 at 50 kHz was achieved respectively. © (2013) Trans Tech Publications, Switzerland.
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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.
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    Voltage dependence of photocurrent in metal-semiconductor-metal structures under front-illuminated conditions
    (2001-10-01)
    Niemcharoen, S.
    ;
    Kobayashi, K.
    ;
    Kimura, M.
    ;
    Sato, K.
    Bias dependence of the photocurrent in planar metal-semiconductor-metal systems under dc and ac optical illumination conditions has been examined experimentally. Making use of molybdenum-silicon-molybdenum structures with a long undepleted neutral region, we measured their dc and low frequency (100 Hz to 100 kHz) photoresponse properties. It was confirmed that, in addition to opto-electronic conversion function, these structures showed an appreciable voltage controllability of the photocurrent in the device. © 2001 Elsevier Science Ltd. All rights reserved.