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    A comparative study on the electrical parameters of Au/n-Si Schottky diodes with and without interfacial (Ca1.9Pr0.1Co4Ox) layer
    (World Scientific Publ Co Pte Ltd, 2016) Kaya, A.; Cetinkaya, H. G.; Altindal, S.; Uslu, I.
    In order to compare the main electrical parameters such as ideality factor (n), barrier height (BH) (Phi(I-V)), series (R-s) and shunt (R-sh) resistances and energy density distribution profile of surface states (N-ss), the Au/n-Si (MS) Schottky diodes (SDs), with and without interfacial (Ca1.9Pr0.1Co4Ox) layer were obtained from the current Z voltage (I-V) measurements at room temperature. The other few electrical parameters such as Fermi energy level (E-F), BIT (Phi(C-V)), Re and voltage dependence of N-ss profile were also obtained from the capacitance voltage (C-V) measurements. The voltage dependence of N-ss profile has two distinctive peaks in the depletion region for two diodes and they were attributed to a particular distribution of N-ss located at metal semiconductor (MS) interface. All of these results have been investigated at room temperature and results have been compared with each other. Experimental results confirmed that interfacial (Ca1.9Pr0.1Co4Ox) layer enhanced diode performance in terms of rectifier rate (RR = I-F/I-R at +/- 3.4 V), N-ss (at 0.5 eV) and Rsh (-3.4 V) with values of 265, 5.38 x 10(13)eV(-1).cm(-2) and 7.87 x 10(4) Omega for MS type Schottky barrier diode and 2.56 x 10(6), 1.15 x 10(13) eV(-1).cm(-2) and 7.50 x 10(8) Omega for metal insulator semiconductor (MIS) type SBD, respectively. It is clear that the rectifying ratio of MIS type SBD is about 9660 times greater than MS type SBD. The value of barrier height (BIT) obtained from C-V data, is higher than the forward bias I-V data and it was attributed to the nature of measurements. These results confirmed that the interfacial (Ca1.9Pr0.1Co4Ox) layer has considerably improved the performance of SD.
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    Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors
    (Elsevier Science Bv, 2016) Demirezen, S.; Kaya, A.; Yeriskin, S. A.; Balbasi, M.; Uslu, I.
    In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of epsilon', epsilon', tan delta, electric modulus (M' and M '') and sigma(ac) of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of epsilon', epsilon', tand, M', M '' and sigma(ac) of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of epsilon', epsilon '' and tand show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of sigma(ac) and the electric modulus increase with increasing frequency. The high dispersion in epsilon' and epsilon '' values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of epsilon' may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M ' and M '' reach a maximum constant value corresponding to M-infinity approximate to 1/epsilon(infinity) due to the relaxation process at high frequencies, but both the values of M ' and M '' approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of N-ss and R-s of the capacitors. As a result, the change in the epsilon', epsilon '', tan delta, M', M '' and ac electric conductivity (sigma(ac)) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization. (C) 2016 The Authors. Published by Elsevier B.V.
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    Illumination and Voltage Dependence of Electrical Characteristics of Au/0.03 Graphene-Doped PVA/n-Si Structures via Capacitance/Conductance-Voltage Measurements
    (Iop Publishing Ltd, 2015) Sahar, Alialy; Ahmet, Kaya; Uslu, I.; Semsettin, Altindal
    Au/n-Si (MS) structures with a high dielectric interlayer (0.03 graphene-doped PVA) are fabricated to investigate the illumination and voltage effects on electrical and dielectric properties by using capacitance-voltage (C - V)and conductance-voltage (G/omega-V) measurements at room temperature and at 1 MHz. Some of the main electrical parameters such as concentration of doping atoms (N-D), barrier height (Phi(B)(C - V)), depletion layer width (W-D) and series resistance (R-s) show fairly large illumination dispersion. The voltage-dependent profile of surface states (N-ss) and resistance of the structure (R-i) are also obtained by using the dark-illumination capacitance (C-dark - C-ill) and Nicollian-Brews methods, respectively. For a clear observation of changes in electrical parameters with illumination, the values of N-D, W-D, Phi(B)(C - V) and R-s are drawn as a function of illumination intensity. The values of N-D and W-D change almost linearly with illumination intensity. On the other hand, R-s decreases almost exponentially with increasing illumination intensity whereas Phi(B)(C - V) increases. The experimental results suggest that the use of a high dielectric interlayer (0.03 graphene-doped PVA) considerably passivates or reduces the magnitude of the surface states. The large change or dispersion in main electrical parameters can be attributed to generation of electron-hole pairs in the junction under illumination and to a good light absorption. All of these experimental results confirm that the fabricated Au/0.03 graphene-doped PVA/n-Si structure can be used as a photodiode or a capacitor in optoelectronic applications.
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    On double exponential forward bias current-voltage (I-V) characteristics of Au/Ca3Co4Ga0.001Ox/n-Si/Au (MIS) type structures in temperature range of 80-340 K
    (Taylor & Francis Ltd, 2015) Maril, E.; Altindal, S.; Kaya, A.; Kocyigit, S.; Uslu, I.
    Current transport mechanisms (CTMs) of Au/Ca3Co4Ga0.001Ox/n-Si/Au (MIS) type structures were investigated using current-voltage (I-V) characteristics in the temperature range of 80-340K. Semilogarithmic I-V plots show two linear regions corresponding to low (0.075-0.250V) and moderate (0.27-0.70V) biases, respectively. Zero-bias barrier height (phi(B0)) was observed to increase with increase in the temperature, whereas opposite behaviour was observed for ideality factor (n). phi(B0) and (n(-1)-1) vesus q/2kT and phi(B0) versus n plots were drawn to get an evidence of Gaussian distribution (GD) of the barrier heights. These plots, too, show two linear regions corresponding to low (80-160K) and high (200-340K) temperature ranges (LTR and HTR), respectively. Mean value of barrier height ( [GRAPHICS] (B0)) and standard deviation (sigma(s)) were extracted from the intercept and slope of phi(B0) versus q/2kT plots for two linear regions as 0.382eV, 0.0060V for LTR and 0.850eV, 0.135V for HTR at low biases and 0.364eV, 0.0059V for LTR and 0.806eV, 0.132V for HTR at high biases, respectively. [GRAPHICS] (B0) and Richardson constant (A*) values were also obtained from the intercept and slope of the modified Richardson (Ln(I-o/T-2)-(q(2)sigma(2)(s)/2k(2)T(2)) versus q/kT) plots as 131.81 Acm(-2)K(-2), 0.381eV for LTR and 129.35 Acm(-2)K(-2), 0. 854eV for HTR at low biases and 148.01 Acm(-2)K(-2), 0.377eV for LTR and 143.77 Acm(-2)K(-2), 0.812eV for HTR at high biases, respectively. In conclusion, CTM in the structure can be successfully explained in terms of thermionic emission theory with the double GD of barrier heights.
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    The comparative electrical characteristics of Au/n-Si (MS) diodes with and without a 2% graphene cobalt-doped Ca3Co4Ga0.001Ox interfacial layer at room temperature
    (Elsevier Science Bv, 2016) Kaya, A.; Maril, E.; Altindal, S.; Uslu, I.
    To investigate the effect of 2% graphene cobalt (GC)-doped (Ca3Co4Ga0.001Ox) interfacial layer on the main electrical parameters, Au/n-Si (MS) Schottky barrier diodes (SBDs) were fabricated with and without this inter-facial layer. Using forward and reverse bias current-voltage (I-V) measurements, selected electrical parameters of these diodes were obtained and compared at room temperature. The energy density distribution profiles of the surface states (N) were obtained from the forward-bias I-V data by taking into account the voltage-dependent effective barrier height (be) and ideality factor (n(V)). The value of Ns, for the MPS-type diode is one order of magnitude lower than that of the MS diode. These results indicated that the 2% GC-doped (Ca(3)Co(4)Oa(0.001)O(x)) interfacial layer prevents reaction and inter-diffusion between Au and n-Si as well as passivating the active dangling bonds at the semiconductor surface. In addition, the voltage-dependent profile of the resistance (11,) was also obtained for the two diodes from the I-V data using Ohm's law. In both the MS- and MPS-type diodes, an apparent exponential increase in hl was observed from the mid-gap toward the bottom of the E. The experimental results show that the existence of Nss, Rs, and the interfacial layer has a great effect on the electrical characteristics of these structures. The value of the depletion layer width was obtained from C-V measurements at 300 kHz for the two diodes. The obtained results show that the GC-doped (Ca3Co4Ga0.001Ox) interfacial layer considerably enhances the diode performance. (C) 2015 Elsevier B.V. All rights reserved.