On the intersecting behaviour of experimental forward bias current-voltage (Ⅰ-Ⅴ) characteristics of Al/SiO_2/p-Si (MIS) Schottky diodes at low temperatures

摘要

In this study, we have investigated the intersection behaviour of forward and reverse bias current-voltage (Ⅰ-Ⅴ) characteristics of Al/SiO_2/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) Φ_(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 1000T 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 Φ_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.