On the intersecting behaviour of experimental forward bias current-voltage (I-V) characteristics of Al/SiO2/p-Si (MIS) Schottky diodes at low temperatures
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In this study, we have investigated the intersection behaviour of forward and reverse bias current-voltage (I-V) characteristics of Al/SiO2/p-Si Schottky diodes in the temperature range of 79-325 K. The crossing of the experimental semi-logarithmic ln(I)-V curves appears as an abnormality when seen with respect to the conventional behaviour of ideal Schottky diodes. Experimental results show that this crossing of ln(I)-V curves is an inherent property of even Schottky diodes. The ideality factor n was found to decrease, while the zero-bias Schottky barrier height (SBH) Phi(B0) increases with increasing temperature. The conventional Richardson plot is found to be nonlinear in the temperature range measured. However, the ln(I-0/T-2) versus 1000/nT plot gives a straight line corresponding to activation energy 0.233 eV. It is shown that the values of series resistance R-S estimated from Cheung's method were strongly temperature dependent and abnormally increased with increasing temperature. In addition, the temperature dependence of energy distribution of interface states density N-SS profiles was obtained from the forward bias I-V measurements by taking into account the bias dependence of the effective barrier height Phi(e) and ideality factor n. All these behaviours indicate that the thermionic emission (TE) cannot be the main current transport mechanism, especially at low temperatures.