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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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    Structural and optical properties of Zn-In-Te thin films deposited by thermal evaporation technique
    (Elsevier Science Sa, 2013) Gullu, H. H.; Bayrakli, O.; Candan, I.; Coskun, E.; Parlak, M.
    Annealing effects on structural and optical properties of the thermally evaporated Zn-In-Te(ZIT) thin films have been investigated. The structural and the compositional analyses were carried out by means of X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDXA). The as-grown and annealed ZIT films had polycrystalline structure and the preferred orientation changed from (220) to (112) direction with increasing annealing temperature. The optical properties and constants were determined by transmittance measurements in the wavelength range of 200-2000 nm. The effect of annealing on the optical parameters was determined by using Single Oscillator Model (SOM), Envelope Model (EM) and Cauchy Method. The absorbance studies revealed that the films had three distinct transitions in the high absorption region because of the tetragonal distortion, and that was used to evaluate the splitting energies of crystal-field and spin-orbit splitting. The fundamental optical band gap values were found to be lying in the range of 1.51 and 1.72 eV and the notable change of the band gaps due to annealing temperatures was observed. Finally, the Urbach energies were calculated and it was observed that the band tail energies were increasing with increasing annealing temperature. (C) 2013 Elsevier B. V. All rights reserved.