Analysis of the forward and reverse bias I-V characteristics on Au/PVA:Zn/n-Si Schottky barrier diodes in the wide temperature range

Abstract

In this study, the forward and reverse bias current-voltage (I-V) characteristics of Au/Zinc acetate doped polyvinyl alcohol/n-Si Schottky barrier diodes (SBDs) have been investigated over the temperature range of 80-400 K. The values of zero-bias barrier height evaluated from forward and reverse bias I-V data, (ФBFo) and (ФBRo), increase with increasing temperature, and a discrepancy is observed between the values of ФBFo and ФBRo. Because the apparent barrier height (BH) seen from metal to semiconductor is higher than the one seen from semiconductor to metal, the obtained value of ФBFo is always greater than ФBRo value. The difference between them is almost the same as the Fermi energy level. The crossing of the experimental forward bias semilogarithmic ln I-V plots appears as an abnormality when compared to the conventional behavior of ideal SBDs. This behavior was attributed to the lack of free charge at a low temperature and could be expected in the temperature region where there is no carrier freezing out, which is non-negligible at low temperatures. Prior to intersection, the voltage dependent value of resistance (Ri) obtained from Ohm’s law decreases with increasing temperature, but it begins to increase after this intersection point. Such an increase in ФBo and series resistance (Rs) with temperature corresponding to high voltage region is in obvious disagreement with the reported negative temperature coefficients. However, the value of shunt resistance (Rsh) corresponding to a low or negative voltage region decreases with increasing temperature. In addition, the temperature dependent energy density distribution profiles of interface states (Nss) were obtained from forward bias I-V measurements by taking into account the bias dependence of the effective barrier height (Фe) and Rs of the device, and the values of Nss without considering Rs are almost one order of magnitude larger than Nss when considering Rs value.