Browsing by Author "Çiçek O."

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Comparative investigation on electronic properties of metal-semiconductor structures with variable ZnO thin film thickness for sensor applications
(2019-10-01) Çiçek O.; Kurnaz S.; Bekar A.; Öztürk Ö.
In this work, AuPd/n-GaAs and Ag/n-GaAs metal–semiconductor structures, which is known as Schottky Junction Structures (SJSs), with various ZnO thin film thickness (25–250 nm) classified as Group AuPd and Group Ag were produced to investigate electronic properties on SJSs. The current-voltage (I–V) characteristics of SJSs operating in their forward and reverse regions operating at ±3 V were measured at room temperature (295 K). The electronics parameters such as the series resistance (Rs), the shunt resistance (Rsh), the ideality factor (n) and the barrier height (ΦB0) were calculated by using thermionic emission (TE) theory, Ohm's law, Cheung and Cheung's function and modified Norde's function. Labview® based characterization tool developed to calculate the electronic parameters. The results were compared according to the various thicknesses and different rectifier contacts. Experimentally, if the results are analysed for each group, a (gradual) decrease in ZnO thicknesses is caused by an increase in the values of n, ФB0, RR. In addition, the Rsh values were significantly increased while the Rs values were almost close to each other. As the ΦB0 values, while compatible with the values found in the Cheung and Cheung's function, they are slightly higher than the values found in the TE theory. On the other hand, due to the voltage-dependent barrier height and nature of the used method, ФB0 values from modified Norde's function are a little higher than the TE theory. Finally, it can be clearly seen that electronic parameters of SJSs based on sensor applications can be arranged with various thicknesses according to extracted results.
Correction to: Identifying of series resistance and interface states on rhenium/n-GaAs structures using C–V–T and G/ω–V–T characteristics in frequency ranged 50 kHz to 5 MHz (Journal of Materials Science: Materials in Electronics, (2020), 31, 1, (704-713), 10.1007/s10854-019-02578-1)
(2020-01-01) Çiçek O.; Durmuş H.; Altındal Ş.
The original version of the article inadvertently published without the character omega “ω” in all the places. This has been corrected by publishing this erratum. The original article has been corrected.
Dielectric properties, electric modulus and conductivity profiles of Al/Al2O3/p-Si type MOS capacitor in large frequency and bias interval
(2022-03-01) Tan S.O.; Çiçek O.; Türk Ç.G.; Altındal Ş.
The letter reports that the impedance spectroscopy method has been performed to acquire impeccable results on the ac electric conductivity (σac), dielectric (ε′ and ε′′) and electric modulus (M' and M'') components of the Al/Al2O3/p-Si type MOS capacitor. The relevant parameters are defined with C-V-f and G/ω-V-f data between 1 kHz and 5 MHz and ± 3 V at room temperature. Both parts of dielectric constants are decreasing at high frequencies to prevent the interface dipoles from gaining enough time to return to the alternative area. Depending on the restructuring and reorganization of surface states (Nss) in the alternative field, tanδ decreases at higher frequencies. The M' values reach maximum by frequency increment in the depletion region, while M'' values shift to the forward biases depending on a certain density distribution of Nss. The σac values increase with increasing frequency in the accumulation region depending on series resistance. Considering polarization processes, surface conditions (Nss) and Al2O3 interlayer, frequency and biases are extremely effective and dependent on the dielectric specifications, electrical modulus and conductivity.
Electrical characterizations of Au/ZnO/n-GaAs Schottky diodes under distinct illumination intensities
(2016-08-01) Tan S.O.; Uslu Tecimer H.; Çiçek O.; Tecimer H.; Orak; Altındal
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.
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
(2016-08-01) Çiçek O.; Tecimer H.U.; Tan S.O.; Tecimer H.; Altindal; 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 (Io), ideality factor (n), barrier height (ΦBo), series (Rs) and shunt resistances (Rsh) 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 Rs value and an increase in Rsh value for Gr-doped PVA in comparison with the pure PVA structure under dark and illuminated conditions, therefore rectifier rate (RR = IF/IR), is the proof of the quality for diodes, significantly improved. Also, the ΦBo 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.
Frequency dependent C–V and G/ω–V characteristics on the illumination-induced Au/ZnO/n-GaAs Schottky barrier diodes
(2017-03-01) Tan S.O.; Tecimer H.U.; Çiçek O.; Tecimer H.; Altındal
Au/ZnO/n-GaAs Schottky barrier diodes (SBDs) have been examined by the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The frequency dependence characteristics of measurements were obtained under various illumination levels at room temperature. The C and G/ω 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/ω 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.
Frequency Response of C–V and G/ω-V Characteristics of Au/(Nanographite-doped PVP)/n-Si Structures
(2021-01-01) Akbaş A.M.; Çiçek O.; Altındal Ş.; Azizian-Kalandaragh Y.
This paper reports that frequency response on profile of C–V–ƒ and G/ω–V–ƒ characteristics of spin-coated nanographite (NG)-doped polyvinylpyrrolidone (PVP)/n-Si structures in a wide frequency (1 kHz–5 MHz) and voltage (± 3 V) ranges at room temperature. Hereby, the basic parameters of the structure such as diffusion potential (VD), doping donor density (ND), Fermi energy level (EF), maximum electric field (Em), depletion layer thickness (Wd), and barrier height (ΦB) are derived by using the intercept and slope of C−2–V–ƒ plot for each frequency. Additionally, the energy density distribution of surface states (Nss) and their relaxation time values (τ) are also attained from the conduction method and their values are found as 4.999 × 1012 eV−1 cm−2 and 2.92 µs at 0.452 eV, and 3.857 × 1012 eV−1 cm−2 and 164 µs at 0.625 eV, respectively. The lower Nss values are the consequence of passivation effect of the used nanographite (NG)-PVP polymer interlayer. As a result, the polymer interlayer based nanographite (NG)-PVP is candidate instead of the widely used oxide/insulator layer for the purpose of decreasing the surface states or dislocations.
Identifying of series resistance and interface states on rhenium/n-GaAs structures using C–V–T and G/ω–V–T characteristics in frequency ranged 50 kHz to 5 MHz
(2020-01-01) Çiçek O.; Durmuş H.; Altındal Ş.
In this study, Re/n-GaAs with a native oxide layer based on metal–semiconductor (MS) structures were produced and then, the capacitance–voltage–temperature (C–V–T) and the conductance–voltage–temperature (G/ω–V–T) data of them were obtained in the frequency ranged 50 kHz to 5 MHz. Using the raw data, the electronic parameters was calculated by the developed LabVIEW-based program. Methodologically, the series resistance (Rs) values were calculated from the measured capacitance (Cm) and conductivity (Gm) values, while the interface state (Nss) values were obtained from using the combined high (CHF)–low (CLF) frequency capacitance method by Nicollian and Brews. Experimentally, the C values increased with a decreasing frequency, while decreased with increasing temperatures in the depletion and accumulation regions. On the other hand, G/ω values decreased with increasing frequency in forward and reverse bias regions. It can be attributed that, the C and the G/ω values are quite affected by the presence of the Rs and the Nss in the forbidden energy gap and a native oxide layer between M and S. The Rs–V–T curves have especially peaks in accumulation and depletion regions at low frequency values, whereas these peaks decreased at high frequencies. In addition, the Nss–V–T curves give peaks in the range of − 0.1 V to 0.7 V at variable temperatures and the Nss values decrease with increasing temperature and shift towards negative bias regions. Experimental results indicate that the Rs and Nss are important parameters and so, these parameters must be considered in sensor applications based on Re/n-GaAs structures.
Role of Graphene-Doped Organic/Polymer Nanocomposites on the Electronic Properties of Schottky Junction Structures for Photocell Applications
(2018-12-01) Çiçek O.; Tan S.O.; Tecimer H.; Altındal Ş.
In this study, the current–voltage characteristics of non-doped and distinct graphene (Gr)-doped polyvinyl alcohol (PVA) interlayers in metal/organic polymer semiconductor type Schottky junction structures (SJSs) were investigated on both forward and reverse biases under distinct levels of illumination. The distinct doping concentration ratios (1%, 3% and 7%) of the Gr added to the PVA interlayers were compared by taking into account the basic electrical parameters, such as saturation current (Io), ideality factor (n), barrier height (ΦBo), series (Rs) and shunt resistance (Rsh). The 7% Gr-doped structure displayed the lowest Io values at zero bias. Moreover, the results indicated that the 7% Gr-doped PVA decreased the n value but increased the ΦBo value compared with values associated with structures that have different doping concentrations. In terms of quality and reliability, the Rs and Rsh values of the SJSs were obtained using Ohm’s law and Cheung’s functions, and the 7% Gr-doped structure eventually displayed more uniformly distributed and lower Rs values and the highest Rsh values. Consequently, the 7% Gr-doped structure had better overall quality because of its superior electrical properties compared with structures that have other doping concentrations. Therefore, the 7% Gr-doped structure can be used as a photodiode in electronic devices.
Self-powered visible-UV light photodiodes based on ZnO nanorods-silicon heterojunctions with surface modification and structural enhancement
(2022-07-01) Çiçek O.; Karasüleymanoğlu M.; Kurnaz S.; Öztürk Ö.; Taşçı A.T.
The letter reports the visible-UV light response of Al/ZnONRs/ZnOseed/p-Si/Al type photodiodes (PDs) with surface modification and structural enhancement. The PDs, which are referred to as PD10–2, PD10–4, PD20–2, PD20–3, and PD20–4 according to molar concentration (mM) and time (hour), were produced for improving the performances. Basic electronic parameters were obtained from the I-V data of Al/ZnONRs/ZnOseed/p-Si/Al type PDs by using thermionic emission (TE) theory, Ohm's law, and Cheung's methods. In accordance with the literature, the results showed that the potential barrier height (ФBo) values decreased with the increasing illumination intensity, while the ideality factor (n) values increased. In addition, voltage-dependent series resistance (Rs) values of the PDs under dark and different visible-UV light intensities were calculated by using Ohm's law and Cheung's method. It was observed that the Rs values decreased with increasing light intensities. On the other hand, the photosensitivity characteristics of the PDs at visible-UV light intensities were investigated depending on the applied voltage. While the photosensitivity value of the produced PD10–2 device reached the maximum value of 6.9 × 103 at the short-circuit voltage Vsc= 0 V, the open-circuit voltage Voc showed better photosensitivity with a minimum value of 0.0702 in the self-powered mode. In addition, the responsivity (R) and the detectivity (D*) values of Al/ZnONRs/ZnOseed/p-Si/Al type PDs were calculated. Herein, the R and D* values decreased with increasing power density at zero-bias voltage in accordance with the literature. Also, the R and D* values of the PD10–2 device are higher and lower than other devices, respectively. The linear dynamic range (LDR) value of the PD10–2 device reaches ~78 dB with a maximum value at Vbias= 0 V, while the dark current is 0.21 nA with a minimum value, self-powered mode. It is concluded that the PD10–2 device is suitable for photodiode applications in self-powered mode.
Synthesis and characterization of pure and graphene (Gr)-doped organic/polymer nanocomposites to investigate the electrical and photoconductivity properties of Au/n-GaAs structures
(2017-03-15) Çiçek O.; Uslu Tecimer H.; Tan S.O.; Tecimer H.; Orak; Altındal
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 (Io), barrier height (ФBo), shunt (Rsh) and series (Rs) resistances) and photoconductivity (i.e. photocurrent (Iph), responsivity (R), photoconductivity sensitivity (Sph), photosensitivity) parameters of Au/n-GaAs devices. Electrical parameters of Au/n-GaAs (MS) type (D1), Au/pure PVA/n-GaAs (MPS) type (D2) and Au/Gr-doped PVA/n-GaAs (MPS) type (D3) 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 (Ri) 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 Rsh value and a decrease in Rs value and rectifier rate (RR = IF/IR) for Gr-doped PVA structure according to the pure PVA structure, when the values of Rs and Rsh are compared between each other. Also, the ΦBo values for D2 and D3 type SDs is lower than that of D1 type SDs. The value of Rs 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 Iph 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 D2 and D3 and a decrease for D1 with increasing illumination intensities in the R and Sph 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.