Yazar "Gullu, O." seçeneğine göre listele

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    Characterization of an Au/n-Si photovoltaic structure with an organic thin film
    (Elsevier Sci Ltd, 2013) Ozaydin, C.; Akkilic, K.; Ilhan, S.; Ruzgar, S.; Gullu, O.; Temel, H.
    We demonstrate that a copper(II) organic complex can control the electrical characteristics of conventional Au/n-Si metal semiconductor (MS) contacts. We investigated the electronic and photovoltaic properties of a Cu(II) complex/n-Si heterojunction diode. The ideality factor n and barrier height Phi(b) of the diode were 2.22 and 0.736 eV, respectively. An ideality factor greater than unity indicates that the diode exhibits non-ideal current voltage behavior. This behavior results from the effect of series resistance and the presence of an interfacial layer. The series resistance and barrier height determined using Norde's method were 6.7 k Omega and 0.77 eV, respectively. The device showed photovoltaic behavior, with a maximum open-circuit voltage of 0.24 V and a short circuit current of 1.7 mu A under light of 8 mW/cm(2). (C) 2013 Elsevier Ltd. All rights reserved.
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    Current-voltage and capacitance-voltage characteristics of Fe/p-InP Schottky barriers
    (Taylor & Francis Ltd, 2010) Asubay, S.; Gullu, O.
    The electrical properties of identically prepared Fe/p-InP (29 dots in total) Schottky barrier diodes on the same p-type InP single crystal have been studied in this article. The effective Schottky barrier heights (SBHs) and ideality factors obtained from current-voltage (I-V) characteristics differ from diode to diode. The SBHs and the ideality factors for the Fe/p-InP diodes ranged from 0.71 to 0.86eV and 1.21 to 1.69, respectively. A lateral homogeneous SBH value of 0.91eV for the Fe/p-InP diodes has been calculated from the linear relationship between barrier heights and ideality factors, which can be explained by lateral inhomogeneities of the SBHs.
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    Determination of the laterally homogeneous barrier height of metal/p-InP Schottky barrier diodes
    (Pergamon-Elsevier Science Ltd, 2009) Asubay, S.; Gullu, O.; Turut, A.
    We have reported a study of a number of metal/p-type InP (Cu, Au, Al, Sn, Pb, Ti, Zn) Schottky barrier diodes (SBDs). Each one diode has been identically prepared on p-InP under vacuum conditions with metal deposition. In Schottky diodes, the current transport occurs by thermionic emission over the Schottky barrier. The current-voltage characteristics of Schottky contacts are described by two fitting parameters such as effective barrier height and the ideality factor. Due to lateral inhomogeneities of the barrier height, both characteristic diode parameters differ from one diode to another. We have determined the lateral homogeneous barrier height of the SBDs from the linear relationship between experimental barrier heights and ideality factors that can be explained by lateral inhomogeneity of the barrier height. Furthermore, the barrier heights of metal-semiconductor contacts have been explained by the continuum of metal-induced gap states (MIGS). It has been seen that the laterally homogeneous barrier heights obtained from the experimental data of the metal/p-type InP Schottky contacts quantitatively confirm the predictions of the combination of the physical MIGS and the chemical electronegativity. (C) 2009 Elsevier Ltd. All rights reserved.
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    Determination of the laterally homogeneous barrier height of thermally annealed and unannealed Au/p-InP/Zn-Au Schottky barrier diodes
    (Elsevier, 2008) Asubay, S.; Gullu, O.; Turut, A.
    We have identically prepared Au/p-InP Schottky barrier diodes (SBDs). The diodes were annealed up to 400 degrees C thermally. The barrier height (BH) for the as-deposited Au/p-InP/Zn-Au SBDs from the current-voltage characteristics have varied from 0.58 to 0.72 eV, and ideality factor n from 1.14 to 1.47. The BH for the annealed SBDs from the current-voltage characteristics have varied from 0.76 to 0.82 eV, and ideality factor n from 1.17 to 1.39. As a result of the thermal annealing, it has been seen that the BH values of the annealed SBDs are larger than those of the as-deposited SBDs. We have determined a lateral homogeneous BH value of 0.72 eV for the as-deposited Au/p-InP SBD from the experimental linear relationship between barrier heights and ideality factors, and a value of 0.85 eV for the annealed Au/p-InP SBD. The increase of 0.13 eV in the BH value by means of 400 degrees C annealing has been ascribed to the formation of the excess charges that electrically actives on the semiconductor surface. (C) 2007 Elsevier B.V. All rights reserved.
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    Electrical characterization of the Al/new fuchsin/n-Si organic-modified device
    (Elsevier, 2010) Gullu, O.; Asubay, S.; Aydogan, S.; Turut, A.
    The current-voltage (I-V) and the capacitance-voltage (C-V) characteristics of the Al/new fuchsin (NF)/n-Si device have been investigated at room temperature. The I-V characteristic of the device shows a good rectification. The ideality factor and the barrier height from the I-V characteristics have been determined as 3.14 and 0.80 eV, respectively. A modified Norde's function combined with the conventional I-V method has been used to extract the parameters including the barrier height and the series resistance. The barrier height and the series resistance obtained from Norde's function have been compared with those from Cheung functions, and it has been seen that there was a good agreement between those from both method. It has also been seen that the values of diode capacitance increased up to the constant values for the forward bias. (C) 2009 Elsevier B.V. All rights reserved.
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    Electrical properties of safranine T/p-Si organic/inorganic semiconductor devices
    (Edp Sciences S A, 2010) Gullu, O.; Asubay, S.; Biber, M.; Kilicoglu, T.; Turut, A.
    We investigated the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of identically prepared safranine T/p-Si organic/inorganic Schottky devices (total 26 diodes) formed by evaporation of organic compound solution on p-Si semiconductor substrate. It was seen that the safranine T organic thin film on the p-Si substrate showed a good rectifying behavior. The barrier heights and ideality factors of all devices were extracted from the electrical characteristics. The mean barrier height and mean ideality factor from I-V measurements were calculated as 0.59 +/- 0.02 eV and 1.80 +/- 0.20, respectively. Also, the mean barrier height and mean acceptor doping concentration from C-V measurements were calculated as 0.67 +/- 0.10 eV and (6.96 +/- 0.37) x10(14) cm(-3), respectively. The discrepancy in the barrier height values obtained from I-V and C-V characteristics has been attributed to different nature of the measurements. The discrepancy between these values can also be due to the existence of the interfacial native oxide and the organic safranine T thin layer between the semiconductor substrate and top contact metal.
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    Electronic properties of the metal/organic interlayer/inorganic semiconductor sandwich device
    (Pergamon-Elsevier Science Ltd, 2010) Gullu, O.; Kilicoglu, T.; Turut, A.
    In this study, we prepared a Metal(Al)/Organic Interlayer(Congo Red=CR)/Inorganic Semiconductor (p-Si) (MIS) Schottky device formed by coating of an organic film on p-Si semiconductor wafer. The Al/CR/p-Si MIS device had a good rectifying behavior. By using the forward bias I-V characteristics, the values of ideality factor (n) and barrier height (Phi(b)) for the Al/CR/p-Si MIS device were obtained as 1.68 and 0.77 eV, respectively. It was seen that the Phi(b) value of 0.77 eV calculated for the Al/CR/p-Si MIS device was significantly higher than value of 0.50 eV of the conventional Al/p-Si Schottky diodes. Modification of the interfacial potential barrier of the Al/p-Si diode was achieved by using a thin interlayer of the CR organic material. This was attributed to the fact that the CR organic interlayer increased the effective barrier height by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 1.24 x 10(13) to 2.44 x 10(12) eV(-1) cm(-2). (C) 2009 Elsevier Ltd. All rights reserved.
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    Morphological and electrical properties of Ag/p-type indium phosphide MIS structures with malachite green organic dyes
    (Virtual Co Physics Srl, 2022) Asubay, S.; Ava, C. A.; Gullu, O.
    Malachite Green (MG) organic dye thin film was prepared by simple drop casting method. Microstructural property of MG layer was investigated by Scanning Electron Microscopy (SEM). SEM image indicated that MG organic thin layer was formed from nanoclusters. Later, it was fabricated Ag/Malachite Green(MG)/p-InP diodes by drop cast method. The barrier height (BH) and ideality factor by using I-V characteristics for the device were found as 0.75 eV and 1.68. By using the Norde method, the BH and the resistance of neutral region of the device were extracted as 0.80 eV and 1.17x104 ??. The interfacial states concentration of the device has been seen to decrease from 2.79??1013 eV-1cm-2 to 5.80??1012 eV-1cm-2. By using capacitance-voltage technique, the values of the built-in voltage, BH and semiconductor doping density were found as 1.22 V, 0.83 eV and 1.87x1017 cm-3 for the Ag/MG/p-InP diode, respectively.
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    The optical characterization of organometallic complex thin films by spectroscopic ellipsometry and photovoltaic diode application
    (Pergamon-Elsevier Science Ltd, 2016) Ozaydin, C.; Gullu, O.; Pakma, O.; Ilhan, S.; Akkilic, K.
    In this work, organometallic complex (OMC) films have been deposited onto glass or silicon substrates by spin coating technique and their photovoltaic application potential has been investigated. Optical properties and thickness of the film have been investigated by spectroscopic ellipsometry (SE). Also, transmittance spectrum has been taken by UV/vis spectrophotometer. The optical method has been used to determine the band gap value of the films. Also, Au/OMC/n-Si metal/interlayer/semiconductor (MIS) diode has been fabricated. Current voltage and photovoltaic properties of the structure were investigated. The ideality factor (n) and barrier height (Phi(b)) values of the diode were found to be 2.89 and 0.79 eV, respectively. The device shows photovoltaic behavior with a maximum open-circuit' voltage of 396 mV and a short circuit current of 33.8 mu A under 300W light. (C) 2016 Elsevier Ltd. All rights reserved.
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    Temperature dependence of current-voltage characteristics of Sn/p-Si Schottky contacts
    (Elsevier, 2008) Aydin, M. E.; Gullu, O.; Yildirim, N.
    The current-voltage (I-V) characteristics of Sn/p-Si Schottky barrier diode have been measured over a wide range of temperature (80-300 K) and interpreted on the basis of thermionic emission mechanism by merging the concept of barrier inhomogeneities through a Gaussian distribution function. The analysis has revealed an anomalous decrease of apparent barrier height Phi(b0), increase of ideality factor n, and nonlinearity of the activation energy plot at lower temperatures. A Phi(b0) versus 1/T plot has been drawn to obtain evidence of a Gaussian distribution of barrier heights, and values of 0.97 eV and 0.084 V for the mean barrier height Phi(b0) and standard deviation sigma(0) have been obtained, respectively, from this plot. A modified ln(I-0/T-2)-(q(2)sigma(2)/2k(2)T(2)) versus 1/T plot gives Phi(b0) and Richardson constant A** as 0.95 eV and 15.6 A cm(-2) K-2, respectively. It can be concluded that the temperature dependent I-V characteristics of the Sn/p-Si Schottky barrier diode can be successfully explained on the basis of a thermionic emission mechanism with Gaussian distribution of the barrier heights. We have also discussed whether or not the junction current has been connected with thermionic field-emission mechanism. (C) 2007 Elsevier B.V. All rights reserved.