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

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 110-360 K. 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 1.395×10−8 A/cm2 K2 which is much lower than the known theoretical value of 112 A/cm2 K2 for n-Si. The Φ¯bo and standard deviation (σ0) were obtained from the intercept and slope of Φbo vs q/kT plot as 1.146 eV and 0.13 V. Thus, the Φ¯bo and effective value of A⁎ were obtained as 1.078 eV and 113.03 A/cm2 K2 from the modified Richardson plot. The obtained experimental value of A⁎ is in a good agreement with the theoretical value of 112 A/cm2 K2 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.