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Author: Gullu, H. H.COAR Access Rights: open access

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Now showing 1 - 3 of 3
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    Article
    Citation - WoS: 14
    Citation - Scopus: 14
    Temperature Dependence of Electrical Properties in In/Cu2< Diodes
    (indian Acad Sciences, 2019) Gullu, H. H.; Yildiz, D. E.; Surucu, O. Bayrakli; Terlemezoglu, M.; Parlak, M.
    Cu2ZnSnTe4 (CZTTe) thin films with In metal contact were deposited by thermal evaporation on monocrystalline n-type Si wafers with Ag ohmic contact to investigate the device characteristics of an In/CZTTe/Si/Ag diode. The variation in electrical characteristics of the diode was analysed by carrying out current-voltage (I-V) measurements in the temperature range of 220-360 K. The forward bias I-V behaviour was modelled according to the thermionic emission (TE) theory to obtain main diode parameters. In addition, the experimental data were detailed by taking into account the presence of an interfacial layer and possible dominant current transport mechanisms were studied under analysis of ideality factor, n. Strong effects of temperature were observed on zero-bias barrier height (Phi(B0)) and n values due to barrier height inhomogeneity at the interface. The anomaly observed in the analysis of TE was modelled by Gaussian distribution (GD) of barrier heights with 0.844 eV mean barrier height and 0.132 V standard deviation. According to the Tung's theoretical approach, a linear correlation between Phi(B0) and n cannot be satisfied, and thus the modified Richardson plot was used to determine Richardson constant (A*). As a result, A* was calculated approximately as 120.6 A cm(-2) K-2 very close to the theoretical value for n-Si. In addition, the effects of series resistance (R-s) by estimating from Cheng's function and density of surface states (N-ss) by taking the bias dependence of effective barrier height, were discussed.
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    Article
    Citation - WoS: 8
    Citation - Scopus: 9
    Investigation of Electrical Properties of In/Znin2< Diode
    (indian Acad Sciences, 2019) Gullu, H. H.
    In/ZnIn2Te4/n-Si/Ag diode structure was fabricated by the thermal deposition of a ZnIn2Te4 thin film on n-Si wafer substrate with Ag metal back contact. The structural characteristics of the film were investigated in terms of composition, X-ray diffraction and topographic measurements. The diode structure was completed by evaporating In metal on the film surface as a top contact. The diode parameters as saturation current, barrier height, ideality factor and series resistance values were determined from the semi-logarithmic forward bias current-voltage characteristics of the diode. According to the assumption of the thermionic emission model, the ideality factor was found higher than unity and it was also observed that the barrier height and ideality factor showed a temperature-dependent profile resulting from the non-ideality in the current-voltage behaviour of the diode. As a result, the model was modified by considering inhomogeneous barrier formation and Gaussian distribution was expected to be dominant on 1.37 eV mean barrier height with a deviation of 0.18. In addition, the voltage dependence of these Gaussian diode parameters was investigated. The forward and reverse bias capacitance and conductance measurements showed that there was a slight change in capacitance values with frequency whereas the conductance values decreased with increase in frequency. In addition to the current-voltage analysis, the distribution of density of interface states and the values of series resistance were evaluated as a function of bias voltage and frequency.
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    Article
    Annealing Effect on Dark Electrical Conductivity and Photoconductivity of Ga-In Thin Films
    (Polish Acad Sciences inst Physics, 2018) Isik, M.; Gullu, H. H.
    Dark-conductivity and photoconductivity properties of thermally evaporated Ga-In-Se (GIS) thin films were investigated in the temperature range of 80-430 K. All measurements were performed on as-grown and annealed GIS thin films at 300 and 400 degrees C to get information about the effect of the annealing temperature on the conductivity properties. Room temperature conductivity was obtained as 1.8 x 10(-8) Omega(-1) cm(-1) for as-grown films and increased to 3.6 x 10(-4) Omega(-1) cm(-1) for annealed films at 400 degrees C. Analysis of the dark-conductivity data of as-grown films revealed nearly intrinsic type of conductivity with 1.70 eV band gap energy. Temperature dependent dark conductivity curves exhibited two regions in the 260-360 and 370-430 K for both of annealed GIS films. Conductivity activation energies were found as 0.05, 0.16 and 0.05, 0.56 eV for films annealed at temperatures of 300 and 400 degrees C, respectively. The dependence of photoconductivity on illumination intensity was also studied in the range from 17 to 113 mW/cm(2).