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    Device behavior of an In/p-Ag(Ga,In)Te2/n-Si/Ag heterojunction diode
    (Elsevier Sci Ltd, 2015) Coskun, E.; Gullu, H. H.; Candan, I.; Bayrakli, O.; Parlak, M.; Ercelebi, C.
    In this work, p-(Ag-Ga-In-Te) polycrystalline thin films were deposited on soda-lime glass and n-type Si substrates by e-beam evaporation of AgGa0.5In0.5Te2 crystalline powder and the thermal evaporation of Ag powder, sequentially in the same chamber. The carrier concentration and mobility of the Ag-Ga-In-Te (AGIT) film were determined as 5.82 x 10(15) cm(-3) and 13.81 cm(2)/(V s) as a result of Hall Effect measurement. The optical analysis indicated that the band gap values of the samples were around 1.58 eV. The structural analysis was carried out by means of X-ray diffraction. Current-Voltage (I-V) measurements depending on the sample temperature were performed to investigate the device characteristics and the dominant conduction mechanism in an In/p-AGIT/n-Si/Ag structure. The series and shunt resistances were calculated by the help of parasitic resistance analysis as 5.73 and 1.57 x 10(4) Omega cm(2), respectively at room temperature. The ideality factors and barrier heights were evaluated as a function of sample temperature. In the low bias region, the thermionic emission together with the generation-recombination mechanism was investigated as the dominant transport mechanism; however, in the high bias region, space charge limited current was analyzed as the other effective mechanism in the carrier conduction. The built-in potential of the device was also determined by the help of capacitance-voltage measurements. (C) 2015 Elsevier Ltd. All rights reserved.
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    FABRICATION AND CHARACTERIZATION OF TiO2 THIN FILM FOR DEVICE APPLICATIONS
    (World Scientific Publ Co Pte Ltd, 2019) Hosseini, A.; Gullu, H. H.; Coskun, E.; Parlak, M.; Ercelebi, C.
    Titanium oxide (TiO2) film was deposited by rectification factor (RF) magnetron sputtering technique on glass substrates and p-Si (111) wafers to fabricate n-TiO2/p-Si heterojunction devices for the investigation of material and device properties, respectively. The structural, surface morphology, optical and electrical properties of TiO(2 )film were characterized by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), UV-visual (UV-Vis) spectral and dark current-voltage (I-V) measurement analyses. The deposited film layer was found to be homogeneous structure with crack-free surface. The bandgap value of TiO2 film was determined as 3.6 eV and transmission was around 65-85% in the spectral range of 320-1100 nm. The conductivity type of the deposited film was determined as n-type by hot probe method. These values make TiO2 film a suitable candidate as the n-type window layer in possible diode applications. TiO2 film was also deposited on p-Si (111) wafer to obtain Al/n-TiO2/p-Si/Al heterojunction device structure. The dark I-V characteristic was studied to determine the possible conduction mechanisms and diode parameters.
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    Öğe
    Study on the Structural and Electrical Properties of Sequentially Deposited Ag-Ga-In-Te Thin Films
    (Springer/Plenum Publishers, 2015) Coskun, E.; Gullu, H. H.; Parlak, M.; Ercelebi, C.
    The structural properties and electrical conduction mechanisms of Ag-Ga-In-Te thin films deposited by a combination of e-beam and thermal evaporation methods were studied for various annealing temperatures. Structural analysis showed the existence of InTe and InTe binary phases at the early stage of crystallization and monophase of AgGaInTe with the main orientation along (112) direction following the post-annealing at 400 C. The effects of the structural changes on electrical properties and temperature dependence of the electrical conductivity of Ag-Ga-In-Te thin films were studied in the temperature range of 90-400 K. The analysis of electrical conductivity revealed the Efros-Shklovskii variable range hopping (VRH) mechanism in between 90 and 210 K and Mott VRH mechanisms for the temperature range of 250-400 K for all deposited films. The VRH parameters including average hopping distance, average hopping energy and characteristic temperature coefficient for Efros-Shklovskii and Mott VRH mechanisms were determined and discussed in detail.