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Author: Gullu, H. H.Subject: Gaussian distribution

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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: 25
    Citation - Scopus: 26
    Determination of Current Transport Characteristics in Au-cu/Cuo Schottky Diodes
    (Elsevier, 2019) Surucu, O. Bayrakli; Gullu, H. H.; Terlemezoglu, M.; Yildiz, D. E.; Parlak, M.
    In this study, the material properties of CuO thin films fabricated by sputtering technique and electrical properties of CuO/n-Si structure were reported. Temperature-dependent current-voltage (I-V) measurement was carried out to determine the detail electrical characteristics of this structure. The anomaly in thermionic emission (TE) model related to barrier height inhomogeneity at the interface was obtained from the forward bias I-V analysis. The current transport mechanism at the junction was determined under the assumption of TE with Gaussian distribution of barrier height. In this analysis, standard deviation and mean zero bias barrier height were evaluated as 0.176 and 1.48 eV, respectively. Depending on the change in the diode parameters with temperature, Richardson constant was recalculated as 110.20 Acm(-2)K(-2) with the help of modified Richardson plot. In addition, density of states at the interface were determined by using the forward bias I-V results.
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    Article
    Citation - WoS: 10
    Citation - Scopus: 10
    Electrical Characterization of Cdznte/Si Diode Structure
    (Springer Heidelberg, 2020) Balbasi, C. Dogru; Terlemezoglu, M.; Gullu, H. H.; Yildiz, D. E.; Parlak, M.
    Temperature-dependent current-voltage (I - V), and frequency dependent capacitance-voltage (C - V) and conductance-voltage (G - V) measurements were performed in order to analyze characteristics of CdZnTe/Si structure. Obtained profiles enable us to understand the different characteristics of the diode structure such as the carrier conduction mechanism and the nature of the interfacial layer. Over the temperature range between 220 and 340 K, taking consideration of the disparity in the forward-biased current, the diode parameters such as saturation current (I-0), zero-bias barrier height (Phi(B0)) and ideality factor (n) have been obtained. The barrier height increased (0.53 to 0.80 eV) while the ideality factor decreased (4.63 to 2.79) with increasing temperature from 220 to 340 K, indicating an improvement in the junction characteristics at high temperatures. Due to the inhomogeneity in barrier height, the conduction mechanism was investigated by Gaussian distribution analysis. Hence, the mean zero-bias barrier height ((Phi) over bar (B0)) and zero-bias standard deviation (sigma(0)) were calculated as 1.31 eV and 0.18, respectively. Moreover, for holes in p-type Si, Richardson constant was found to be 32.09 A cm(-2) K-2 via modified Richardson plot. Using the capacitance-voltage (C - V) and conductance-voltage (G - V) characteristics, series resistance (R-s) and density of interfacial traps (D-it) have been also investigated in detail. A decreasing trend for R-s and D-it profiles with increasing frequency was observed due to the impurities at the CdZnTe/Si interface and interfacial layer between the front metal contact and CdZnTe film.