Browsing by Author "Tecimer H."

Now showing 1 - 6 of 6

Comparative investigation on the effects of organic and inorganic interlayers in Au/n-GaAs Schottky diodes
(2017-03-01) Tan S.; Tecimer H.; Cicek O.
There have been many attempts on Schottky barrier diodes (SBDs) to improve the quality of metal-semiconductor (MS) structure and control permanently the barrier height (BH) by utilizing an organic or inorganic interfacial layer instead of widely used SiO2. The organic polymer or inorganic insulator interfacial layer insertion to the M/S interface converts the structure into the metal-polymer-semiconductor (MPS) or metal-insulator-semiconductor (MIS). The reliability and performance of the MIS/MPS-type SBDs is drastically affected by the interface layer quality and also its thickness. In this paper, MS structure forms as Au/n-GaAs are consecutively used with an organic interfacial layer polyvinyl alcohol and inorganic interfacial layer zinc oxide to compare their effects on the electrical characteristics of SBDs under distinct illumination levels. Consequently, the current-voltage characteristics provide us to reveal and compare the improvement and reliability of the MPS and MIS-type SBDs by also considering significant electrical parameters, such as ideality factor, apparent BH, and series resistance.
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.
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.
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.