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Preparation and properties indium tin-oxide thin films by RF sputtered for photodetectors
(2008-01-01)
Srithanachai, I.
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Nutaman, K.
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Rerkratn, A.
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Niemcharoen, S.
;
Supadech, S.
This paper descript studying and preparation indium-tin oxide (ITO) thin film from method 90 wt.% ln<inf>2</inf>O<inf>3</inf> and 10 wt.% SnO<inf>2</inf> formula target with 99.99% purity on glass slide by RF reactive sputtering method at room temperature. This paper, sputtering time 5, 15, 30 and 60 mins. Thin films ITO were measured crystallization, optical and electrical characteristic by an X-ray diffractometer (XRD), scan electron microscopy (SEM) , Four Point Probe and UV-VIS spectrophotometry. The results found that thin films which made from RF sputtering method had a high crystallization, order arrangement grain. Strong peak of XRD (400) and (441), low resistivity are 2.2 × 10-3 4.4 × 10-3 1 × 10-3 and 7 × 10-4 β-cm, transmittance are 82%, 84%, 87% and 89%, respectively. The overall experimental results identify that fabricated thin films ITO have good properties and is suitable for transparent electrode application. The ultimate goal is developing schottky photodetector. © 2008 Trans Tech Publications, Switzerland.
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White noise due to photocurrents in planar MSM structures on low-resistivity Si
(2003-10-01)
Khunkhao, S.
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Niemcharoen, S.
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Supadech, S.
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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>Γ2, where e is the electronic charge and I<inf>p</inf> is the photocurrent, the noise ratio Γ2 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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Photosensing properties of interdigitated metal-semiconductor-metal structures with undepleted region
(2003-08-01)
Masui, T.
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Khunkhao, S.
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Kobayashi, K.
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Niemcharoen, S.
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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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Observation of photoinduced shot noise in planar Mo/n-Si/Mo structures with undepleted region
(2002-04-01)
Niemcharoen, S.
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Ando, T.
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Supadech, S.
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Yasumura, Y.
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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) = 2qIΓ2 (q, the electronic charge; I, the average current), the noise factor, Γ2, 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.
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UV photodetector from Schottky diode diamond film
(2002-03-01)
Thaiyotin, L.
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Ratanaudompisut, E.
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Phetchakul, T.
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Cheirsirikul, S.
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Supadech, S.
Diamond film was synthesized on a silicon substrate by hot-filament CVD and used to fabricate a Schottky photodiode for the detection of UV light. This paper presents an improved structure of photodiode, which reduces the effect of grain boundaries in the polycrystalline diamond film. The Schottky photodiode was fabricated on free-standing diamond film and operation in a vertical direction can be expected to reduce the effect of grain boundaries. The device shows good response to UV light and a very low response to visible light. The dark current is less than 10 pA. The device response time is less than 20 μs. Furthermore, the device reveals little change in spectral response with increasing temperature at all wavelengths. © 2002 Elsevier Science B.V. All rights reserved.
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Study of silicon thermopile
(2000-12-01)
Muanghlua, R.
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Cheirsirikul, S.
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Supadech, S.
This research paper introduces a silicon thermopile sensor, which shows higher Seebeck coefficient than a metal thermopile sensor. The vacuum evaporation technique was used to fabricate this silicon-based thermopile with Titanium as parts of the sensor. By using the concept that different of temperature between junctions would induce voltage that corresponse to the temperature different and materials used for the device. This work starting from design, fabricate, and test the device. At the ends of this work, we successfully fabricated the sensor and tested. The results show that the sensor demonstrate higher Seebeck coefficient than the one from metal-base thermopile sensor. For the future work, the different materials will be used to fabricate the thermopile sensor and compared to the Seebeck coefficient of the one from silicon.
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UV photodetectors from B-doped diamond film
(2000-12-01)
Thaiyotin, L.
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Phetchakul, T.
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Cheirsirikul, S.
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Supadech, S.
The diamond film synthesized on silicon substrate by hot-filament CVD has been used to fabricate photoconductive and photodiode structures for the detection of UV light. The photoconductive device which the higher boron doped has a greater different response between UV light and visible light more than the lower one, but it has more dark current and response time. The Al schottky photodiode fabricated on the B-doped diamond film showed lower dark current and shorter response time than photoconductive device.
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Switching Phenomena in Reverse-Biased Gold-Diffused Silicon p+-i-n+ Diodes
(1979-01-01)
Supadech, S.
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Heng, T.
A novel mode of operation for a reverse-biased narrow i-region gold-diffused silicon p+-i-n+ diode exhibiting switching negative resistance is reported. The i-region width is in the range of 12–16 µm, and gold has been used to generate deep trapping levels in the i-region. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.

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