Serhat Orkun Tan

Electrical characterizations of Au/ZnO/n-GaAs Schottky diodes under distinct illumination intensities

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.

Frequency dependent C–V and G/ω–V characteristics on the illumination-induced Au/ZnO/n-GaAs Schottky barrier diodes

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.

Comparative Investigation on the Effects of Organic and Inorganic Interlayers in Au/n-GaAs Schottky Diodes

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.

Performance and cooling efficiency of thermoelectric modules on server central processing unit and Northbridge

Display Omitted The cooling efficiency of the specific cooling systems on critical server hardware is investigated.The performance of the cooling systems on server CPU is outlined.The applied cooling systems in the context of temperature and performance are compared.The superior performance rating and cooling efficiency is obtained by the thermoelectric cooler. Computer systems are required to process data more rapidly than ever, due to recent software and internet technology developments. The server computers work continuously and provide services to many clients simultaneously, which results in greater heat production and high temperature that must be managed in order to avoid malfunction and failure of critical hardware. In this study, three cooling systems were used comparatively to examine the temperature and performance of the CPU and motherboard. The temperature characteristics and performance of the CPU were tested with a heat sink, water cooling system, and thermoelectric cooler. According to the test results, the thermoelectric cooling system has better cooling performance than the other two systems under continuous operating conditions. Additionally, the performance rating of the CPU was the best with a thermoelectric cooler under varying workloads.

The Analysis of Renewable Energy Researches in Turkey

The rapid consumption of limited conventional energy resources mobilizes many countries in the world against global energy crisis. As well as the energy crisis, the environmental pollution caused by existing energy sources also encourages the researchers to study in new energy technologies and also renewable energy resources. From this point of view, it is important for each country to identify its wind, solar, geothermal, biomass, hydro and other renewable energy potentials. Considering this urgent energy requirement, the researches and especially the academic studies have been increased on renewable energy resources to meet the energy demand by means of indigenous resources in each country. Consequently, the main purpose of this study is to analyze the academic studies in Turkey to find out the increment rate of researches, their publication years and the more focusing branch on renewable energy by illustrating the statistical distribution of these data. Automated Data Retrieval Methods have been employed to achieve data from Web of Science database and statistical analyses have been made by SQL server management studio program. The academic studies in all variety of renewable energy areas have a tendency to increase which indicates the importance ratio of renewable energy in Turkey.

Role of Graphene-Doped Organic/Polymer Nanocomposites on the Electronic Properties of Schottky Junction Structures for Photocell Applications

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.