Catir, Fulya Esra Cimilli; Saglam, Mustafa

In this study, Schottky contacts have been fabricated on n-InP (1 0 0) using an Al/n-InP/In configuration. The current voltage (I-V) and capacitance voltage (C-V) characteristics of Al/n-InP/In Schottky diodes were calculated from the liquid nitrogen temperature to the room temperature by steps of 10 K before annealing of this structure and after annealing at 400 °C for 3 min. The series resistance, ideality factor and barrier height values calculated using I-V characteristics, Cheung functions, Norde (F-V) functions, and C-V characteristics before and after annealing the contact and compared for each temperature. These measurements clearly showed that the Al/n-InP/In Schottky diode became extremely stable due to the annealing process and the mean barrier height value have been increased from 0,494 to 0,674 eV after thermal annealing at 400 °C. In addition, temperature dependent barrier height values of as-fab. and annealed (at 400 °C) Al/n-InP/InSchottky contacts are consistent with "the barrier inhomogeneous model" of Schottky diodes.

Özakin, Oǧuzhan; Güzeldir, Betül; Yildirim, M. Ali; Saǧlam, Mustafa; Ateş, Aytunş

ZnS thin films were deposited on glass substrates using SILAR method at room temperature and ambient pressure. The relationship between refractive index and energy bandgap was investigated. The film thickness effect on the structural, morphological and optical properties of ZnS thin films was investigated. The crystalline and surface properties of the films improved with increasing film thickness. The energy bandgap values changed from 3.87 to 3.58 eV with increasing film thickness. The refractive index (n), high frequency dielectric constant (ε ∞) values were calculated by using the energy bandgap values as a function of the film thickness. Also, ZnS thin film was deposited directly on n-GaAs substrate for obtaining the Zn/ZnS/n-GaAs/In sandwich structure at room temperature. The sandwich structure demonstrated clearly rectifying behaviour by the current-voltage (I-V) curves at room temperature. From I-V characteristics n and φ b values were calculated as 1.894 and 0.632 eV at room temperature, respectively.

Ateş, A.; Saǧlam, M.; Güzeldir, B.; Yildirim, M.A.; Astam, A.

Cu/CuS/p-Si/Al structure formed using CuS thin film on p-Si substrate. CuS thin film has been grown with using Successive Ionic Layer Adsorption and Reaction (SILAR) method. The Cu/CuS/p-Si/Al structure has demonstrated clearly rectifying behavior by the current-voltage (I-V) curves studied at room temperature. The characteristic parameters such as barrier height, ideality factor and series resistance of Cu/CuS/p-Si/Al structure have been calculated from the forward bias I-V and reverse bias C-2-V characteristics. The ideality factor and barrier height have been obtained as n=1.63 and Φb=0.69 eV by applying a thermo-ionic emission theory. At high current densities in the forward direction, the series resistance effect has been observed. The values of Rs obtained from dV/d(lnI) - I and H(I) - I plots are near to each others (Rs=340.33 □ and R s=346.24 □, respectively). In the same way, the barrier height calculated from C-2-V characteristics have been varied from 0.523 to 0.601 eV. Furthermore, the density distribution of interface states of the multilayer device has been obtained from the semi-log forward bias I-V characteristics. It has been seen that the Nss has almost an exponential rise with bias voltage from top of the valance band toward to mid gap.

Saǧlam, M.; Ateş, A.; Yildirim, M.A.; Güzeldir, B.; Astam, A.

In this study, this is the first time, it has been employed Successive Ionic Layer Adsorption and Reaction (SILAR) method in order to prepare Cd/CdO/n-Si/Au-Sb sandwich structure. The sample temperature effect on the current-voltage (I-V) characteristics of Cd/CdO/n-Si/Au-Sb structure has been investigated in a wide temperature range by steps of 20 K. The parameters such as barrier height, ideality factor and series resistance of this structure have been calculated from the forward bias I-V characteristics as a function of sample temperature. With a decreasing temperature, a decreasing in the apparent barrier height (Φb0), an increasing in the ideality factor (n) and a nonlinearity in the activation energy plot have been seen. The experimental values of barrier height and ideality factor for this device have been calculated as 0.871 eV and 1.787 at 300 K and 0.436 eV and 2.221 at 80 K, respectively. These abnormal behaviors can be explain by the barrier inhomogeneities at the metal-semiconductor (M-S) interface. From the temperature dependent I-V characteristics of the Cd/CdO/n-Si/Au-Sb sandwich structure, over(Φ, ̄)b 0 and A* are calculated as 0.790 and 1.160 eV, and 153.90 and 188.42 A/cm2 K2, respectively, by using ln (I0 / T2) - q2 σs2 / 2 k2 T2 vs. 1/T plot for the two temperature regions. Deviation of experimental values of A* from known value for n-Si has been attributed to the spatial inhomogeneous barrier heights and potential fluctuations at the interface that consist of low and high barrier areas.

Saǧlam, M.; Ateş, A.; Güzeldir, B.; Astam, A.; Yildirim, M.A.

In general, at the metal-semiconductor contacts, interfacial layers have been fabricated by different methods such as molecular beam epitaxy, metal organic chemical vapor deposition, sputtering and vacuum evaporation. However, all of these techniques have encountered various difficulties in the deposited films. Instead of these methods, since Successive Ionic Layer Adsorption and Reaction (SILAR) method is simple, fast, sensitive, and less costly to prepare interfacial layer, we have first employed this method in order to prepare Cd/CdS/n-Si/Au-Sb sandwich structure. For this reason, the CdS thin film has been directly formed on n-type Si substrate by means of SILAR method. The Cd/CdS/n-Si/Au-Sb sandwich structure has demonstrated clearly rectifying behaviour by the current-voltage (I-V) curves studied at room temperature. In order to observe the effect of the thermal annealing, this structure has been annealed at temperatures from 50 to 300 °C for 3 min in N2 atmosphere. The characteristic parameters such as barrier height, ideality factor and series resistance of this structure have been calculated from the forward bias I-V characteristics as a function of annealing temperature with different methods. The values of n, Φb and mean Rs of the initial Cd/CdS/n-Si/Au-Sb sandwich structure were found to be 2.31, 0.790 eV and 1.86 kΩ respectively. After annealing at 300 °C, these values were changed to 1.89, 0.765 eV and 0.48 kΩ. It has been seen that the barrier height, ideality factor and series resistance have slightly changed with increasing annealing temperature up to 300 °C.

Içelli, Orhan; Erzeneoǧlu, Salih; Saǧlam, Mustafa

Effective atomic numbers (Zeff) of polypyrrole have been determined for total photon interactions in the energy range 15.74-40.93 keV from the accurately measured total attenuation coefficients, for characteristic K and K X-rays of Zr, Mo, Ag, In, Sb, Ba and Pr. The results were compared with the theoretical atomic numbers obtained using the XCOM.

Saǧlam, M.; Ateş, A.; Güzeldir, B.; Yildirim, M.A.; Astam, A.

The CdS thin film has been directly formed on n-type Si substrate to form an interfacial layer between cadmium (Cd) and n-type Si with Successive Ionic Layer Adsorption and Reaction (SILAR) method. An Au-Sb electrode has been used as an ohmic contact. The Cd/CdS/n-Si/Au-Sb structure has demonstrated clearly rectifying behaviour by the current-voltage (I-V) curves studied at room temperature. The characteristics parameters such as barrier height, ideality factor and series resistance of Cd/CdS/n-Si/Au-Sb structure have been calculated from the forward bias I-V and reverse bias C-2-V characteristics. The diode ideality factor and the barrier height have been calculated as n = 2.06 and Φb = 0.92 eV by applying a thermionic emission theory, respectively. The diode shows non-ideal I-V behaviour with an ideality factor greater than unity that can be ascribed to the interfacial layer, the interface states and the series resistance. At high current densities in the forward direction, the series resistance (Rs) effect has been observed. The values of Rs obtained from dV/d(lnI)-I and H(I)-I plots are near to each others (Rs = 182.24 Ω and Rs = 186.04 Ω, respectively). This case shows the consistency of the Cheung′s approach. In the same way, the barrier height calculated from C-2 -V characteristics varied from 0.698 to 0.743 eV. Furthermore, the density distribution of interface states (Nss) of the device has been obtained from the forward bias I-V characteristics. It has been seen that, the Nss has almost an exponential rise with bias from the mid gap toward the bottom of conduction band.