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    The electrical current characteristics of thermally annealed Co/anodic oxide layer/n-GaAs sandwich structures
    (World Scientific Publ Co Pte Ltd, 2019) Yildirm, N.; Turut, A.; Biber, M.; Saglam, M.; Guzeldir, B.
    The Co/anodic oxide layer/n-GaAs MOS structures have been fabricated by us. The MOS structures have shown an excellent rectifying behavior before and after thermal annealing of 500 degrees C for 2 min. It has been stated in the literature that the thermal annealing at a relatively low-temperature can improve the quality and performance of the anodic MOS structure. The current-voltage (I-V) measurements of the annealed MOS structure have been attempted in the measurement temperature range 60-320 K with the steps of 20 K. The I-V plot at 300 K has given the diode parameter values as barrier height (Phi(b0) = 0.96 eV and ideality factor n = 1.22, diode series resistance R-s = 124 Omega for the annealed sample, and (Phi(b0) = 0.87 eV and n = 2.11, R-s = 204 Omega for the nonannealed structure. A mean tunneling potential barrier value of 0.59 eV for the anodic oxide layer at the Co/n-GaAs interface has been calculated from the current- voltage-temperature curves. Furthermore, Phi(b0)(T) versus (2kT)(-1) curve has followed a double Gaussian distribution (GD) of the barrier heights. It has been stated that the double GD may be originated from the presence of the surface patches and phases arisen at the anodic oxide layer/n-GaAs interface.
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    Interpretation of the I-V, C-V and G/?-V characteristics of the Au/ZnS/n-GaAs/In structure depending on annealing temperature
    (Elsevier, 2021) Baltakesmez, A.; Guzeldir, B.; Saglam, M.; Biber, M.
    The Zinc Sulphide (ZnS) thin film, which is included in the Au/n-GaAs/In diode as the interface layer, was grown on the n-GaAs semiconductor substrate by the spray pyrolysis method. First, to reveal some structural, surface and optical properties of the ZnS thin film, XRD, SEM and absorption measurements were taken. It was determined that the ZnS thin film completely covering the surface of the n-GaAs semiconductor substrate has a hexagonal structure and a forbidden energy range of 3.83 eV. Later, the current-voltage (I?V), the capacitancevoltage (C?V) and the conductance-voltage (G/?-V) measurements of the Au/ZnS/n-GaAs/In structure were taken at room temperature, and various important parameters of the structure were calculated with different methods. In order to reveal the effects of annealing temperature on the I?V, C?V and G/?-V measurements of Au/ ZnS/n-GaAs/In structure, the device was annealed at 100, 200 and 300 ?C respectively for 5 min in nitrogen gas environment. The characteristic parameters were calculated again and the results were interpreted comparatively. At the same time, with the help of the C?V and G/?-V characteristics, the dependence on applied bias voltage and frequency of the parameters such as dielectric constant, dielectric loss, loss tangent, ac electrical conductivity and real and imaginary part of electric modulus of the diode have been revealed. After thermal annealing at 200 ?C, it has been determined that the ideality factor, turn-on voltage and leakage current values are at minimum level and the barrier height and rectification ratio values are at maximum level. In other words, it has been revealed that the optimum thermal annealing temperature for this device is 200 ?C.