Browsing by Author "Uslu Tecimer H."

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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.
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.