Current-transport mechanisms in gold/polypyrrole/n-silicon Schottky barrier diodes in the temperature range of 110–360 K

Abstract

In this study, Au/polypyrrole/n-Si metal-polymer-semiconductor (MPS) Schottky barrier diode (SBD) was fabricated by using a spin coating system for formation of polypyrrole (PPy) organic layer and a thermal evaporation system for deposition of metal contacts. The forward bias current–voltage–temperature (I–V–T) characteristics of the diode were investigated in the temperature range of 110–360K. The some main electrical parameters such as the zero-bias barrier height (Φbo), ideality factor (n), and effective barrier height (Φbef) were found as function temperature. The experimental results show that the I–V–T characteristics have a non-linear behavior especially due to the effect of series resistance (Rs) and interfacial polymer layer by resulting a higher n value of 3.09 larger than unity (n>1). While the value of Φbo increases, n decreases with increasing temperature and such changes in Φbo and n with temperature was attributed to the presence of saddle point or pinch-off at around mean BH value (Φ¯bo) at M/S interface. The value of Richardson constant (A⁎) was obtained from the slope of conventional Richardson plot, ln(I0/T2) vs (q/kT) as 1.395×10−8A/cm2K2 which is much lower than the known theoretical value of 112A/cm2K2 for n-Si. The Φ¯bo and standard deviation (σ0) were obtained from the intercept and slope of Φbo vs q/kT plot as 1.146eV and 0.13V. Thus, the Φ¯bo and effective value of A⁎ were obtained as 1.078eV and 113.03A/cm2K2 from the modified Richardson plot. The obtained experimental value of A⁎ is in a good agreement with the theoretical value of 112A/cm2K2 for n-Si. As a result, current transport mechanism (CTM) in MPS type SBD can be successfully explained on the basis of thermionic emission (TE) theory with Gaussian distribution (GD) of barrier heights (BHs) around Φ¯bo.