Yazar "Tecimer, H. Uslu" seçeneğine göre listele

Listeleniyor 1 - 6 / 6
  • Küçük Resim Yok
    Öğe
    Detection of current transport mechanisms for graphene-doped-PVA interlayered metal/semiconductor structures
    (Elsevier, 2020) Baydilli, E. Evcin; Tan, S. O.; Tecimer, H. Uslu; Altindal, S.
    The possible current-transport mechanisms (CTMs) of Au/(%7Gr-doped)PVA/n-GaAs structure was examined between 80 K and 360 K. The forward bias semi-logarithmic I-V curves have two different linear regions; as 0.30 V and 0.56 V (Region I), and 0.72 V and 0.92 V (Region II). Contrary to classical thermionic emission (TE) theory, the ideality factor (n) decreases but the zero bias barrier height (Phi(Bo)) increases while the temperature increases for both regions. The plots of n vs Phi(B0), q/2 kT vs Phi(Bo) and q/2 kT vs n(-1)-1 have two linear regions from 80 K to 160 K and 180 K-360 K. This indicates the Double Gaussian Distribution (DGD). Experimental Richardson constant (A*) was acquired as 8.73 A/cm(2)K(2) and 8.14 A/cm(2)K(2) for Region I and II which are quite close to theoretical A* value for n-GaAs. Consequently, the predominant CTMs at M/S interfaces can be clarified by DGD on the basis of TE.
  • Küçük Resim Yok
    Öğe
    The effect of radiation on the forward and reverse bias current-voltage (I-V) characteristics of Au/(Bi4Ti3O12/SiO2)/n-Si (MFIS) structures
    (Springer, 2020) Dulkadir, S.; Tecimer, H. Uslu; Parlakturk, F.; Altmdar, S.; Karal, O.
    Determining the radiation effects on the basic electrical parameters of the fabricated high-dielectric MFIS structures, they were exposed to the high-energy(60)Co gamma-rays. For this purpose, the values of ideality factor (n), barrier height (phi(B)) and series resistance (R-s) were extracted from the forward biasI-Vdata before and after irradiation by using various methods such as standard thermionic emission (TE) theory, Cheung's and Norde functions. Additionally, the energy-dependent profile of surface statesN(ss)was extracted by considering voltage dependence ofn,phi(B)andR(s)and compared each other. Experimental results show that the reverse saturation current (I-o),nandR(s)values increase with increasing radiation dose, but phi(B)decreases. When the value ofR(s)is considered in the calculation ofN(ss), they were found to be considerably decreased. The observed low discrepancies betweenN(ss)after irradiation show that the use of a high-dielectric ferroelectric interlayer leads to an increase in the resistance of MS to radiation. It is more important to fabricate radiation-resisted electronic device, especially in the satellites due to hard radiation in space. As a result,N-ss,R(s)and the existence of interlayer are more effectual on theI-Vcharacteristics which must be considered in the electrical parameter calculation.
  • Küçük Resim Yok
    Öğe
    Electrical characterizations of Au/ZnO/n-GaAs Schottky diodes under distinct illumination intensities
    (Springer, 2016) Tan, S. O.; Tecimer, H. Uslu; Cicek, O.; Tecimer, H.; Orak, I.; Altindal, S.
    The Au/ZnO/n-GaAs Schottky barrier diode was fabricated and examined regarding to its current-voltage characteristics under distinct illumination intensities at room temperature. The reverse biased current increases with increasing illumination level while forward biased current is almost unchanged with illumination which states that the fabricated diodes exhibit photosensitive character or photodiode behavior. Hence, the shunt resistance is decreased with illumination while the series resistance is almost remained constant. The increment in the ideality factor after illumination can be ascribed to the assumption of inhomogeneities at M/S interface. Considering the ideality factor and the voltage dependent effective barrier height, the energy distribution profiles of surface states (Nss) were formed by the forward bias current-voltage data and increased with increasing illumination level. The Nss values acquired by considering series resistance are lower than those acquired by ignoring series resistance. Consequently, surface states can serve as recombination centers and have great importance especially in reverse bias current-voltage characteristics.
  • Küçük Resim Yok
    Öğe
    Evaluation of electrical and photovoltaic behaviours as comparative of Au/n-GaAs (MS) diodes with and without pure and graphene (Gr)-doped polyvinyl alcohol (PVA) interfacial layer under dark and illuminated conditions
    (Elsevier Sci Ltd, 2016) Cicek, O.; Tecimer, H. Uslu; Tan, S. O.; Tecimer, H.; Altindal, S.; Uslu, I.
    Au/n-GaAs (MS) type Schottky diodes (SDs) were fabricated with and without pure and Gr-doped PVA interlayer to evaluate the effects of Gr-doped PVA interlayer on the basic electrical parameters (i.e. saturation current (I-o), ideality factor (n), barrier height (Phi(Bo)), series (R-s) and shunt resistances (R-sh) both under dark and illuminated conditions (50-200 W), at room temperature. Using different calculation methods (i.e. thermionic emission (TE) model, Ohm's Law and Norde's method), these parameters were obtained from the current -voltage (I -V) data and compared with each other in various conditions. In our research, it is clear that there are a decrease in R-s value and an increase in R-sh value for Gr-doped PVA in comparison with the pure PVA structure under dark and illuminated conditions, therefore rectifier rate (RR = I-F/I-R), is the proof of the quality for diodes, significantly improved. Also, the Phi(Bo) values with interlayer (pure and Gr-doped PVA) are lower than without. Consequently, these results indicate that the PVA (pure and Gr-doped) changed effectively the BH according to other structure and, moreover, Gr-doped PVA layer significantly improved the quality of Au/PVA/n-GaAs structure under dark and illuminated conditions. (C) 2016 Elsevier Ltd. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Frequency dependent C-V and G/?-V characteristics on the illumination-induced Au/ZnO/n-GaAs Schottky barrier diodes
    (Springer, 2017) Tan, S. O.; Tecimer, H. Uslu; Cicek, O.; Tecimer, H.; Altindal, S.
    Au/ZnO/n-GaAs Schottky barrier diodes (SBDs) have been examined by the capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements. The frequency dependence characteristics of measurements were obtained under various illumination levels at room temperature. The C and G/omega relation was observed as the decrement in capacitance corresponds to an increment in conductance. The increment of negative capacitance (NC) values by high frequency at forward biases was ascribed to the series resistance, interface states and interfacial layer. Considering the illumination intensity, the NC values were observed to increase with the decreasing illumination while the G/omega values increase with the increasing illumination. This behavior was referred to the increments in the polarization and carriers in the SBDs. The adverse impacts of the voltage dependent resistivity were decreased with increasing illumination levels. Eventually, a strong interaction between the electrical properties of SBDs and the frequency, illumination and applied bias voltage was demonstrated by experimental results.
  • Küçük Resim Yok
    Öğe
    Synthesis and characterization of pure and graphene (Gr)-doped organic/polymer nanocomposites to investigate the electrical and photoconductivity properties of Au/n-GaAs structures
    (Elsevier Sci Ltd, 2017) Cicek, O.; Tecimer, H. Uslu; Tan, S. O.; Tecimer, H.; Orak, I.; Altindal, S.
    In the present study, Schottky diodes (SDs) were produced with and without interlayer to evaluate synthesis and characterization of pure and graphene (Gr)-doped organic/polymer nanocomposites on the electrical (i.e. ideality factor (n), saturation current (I-o), barrier height (Phi(Bo)), shunt (R-sh) and series (R-s) resistances) and photoconductivity (i.e. photocurrent (I-ph), responsivity (R), photoconductivity sensitivity (S-ph), photosensitivity) parameters of Au/n-GaAs devices. Electrical parameters of Au/n-GaAs (MS) type (D-1), Au/pure PVA/n-GaAs (MPS) type (D-2) and Au/Gr-doped PVA/n-GaAs (MPS) type (D-3) structures have been obtained to the current-voltage (I-V) measurements using thermionic emission (TE) theory, Cheung's method and modified Norde's methods and, moreover, compared each other. The resistance (R-i) for these SDs was additionally calculated from Ohm's law as function of voltage for each diode. Experimental research indicate that there is an increase in R-sh value and a decrease in R-s value and rectifier rate (RR = I-F/I-R) for Gr-doped PVA structure according to the pure PVA structure, when the values of R-s and R-sh are compared between each other. Also, the Phi(Bo) values for D-2 and D-3 type SDs is lower than that of D-1 type SDs. The value of R-s for Gr-PVA interlayer 286 times lower than without interlayer. Therefore, it can be said that the PVA (pure and Gr-doped) interfacial layer effectively modified the barrier height (BH) according to without interlayer. As photoconductivity properties for SDs, the I-ph values in the reverse bias increased with illumination intensities (50-200 W). On the other hand, it is clear that there are an increase for D-2 and D-3 and a decrease for D1 with increasing illumination intensities in the R and S-ph values. So, they are sensitive to illumination intensities and exhibit a photoconductivity effect. As a result, Gr-doped PVA interlayer substantially got better the quality and performance of Au/PVA/n-GaAs SDs. (C) 2017 Elsevier Ltd. All rights reserved.