Current-transport mechanism in Au/V-doped PVC plus TCNQ/p-Si structures

Abstract

The forward and reverse bias current-voltage (I-V) characteristics of Au/V-doped polyvinyl chloride+Tetracyanoquino dimethane/porous silicon (PVC+TCNQ/p-Si) structures have been investigated in the temperature range of 160-340 K. The zero bias or apparent barrier height (BH) (Phi(ap) = Phi(Bo)) and ideality factor (n(ap) = n) were found strongly temperature dependent and the value of nap decreases, while the n(ap) increases with the increasing temperature. Also, the Phi(ap) versus T plot shows almost a straight line which has positive temperature coefficient and it is not in agreement with the negative temperature coefficient of ideal diode or forbidden bandgap of Si (alpha(Si) = -4.73x10(-4) eV/K). The high value of n cannot be explained only with respect to interfacial insulator layer and interface traps. In order to explain such behavior of Phi(ap) and nap with temperature, Phi(ap) Versus q/2kT plot was drawn and the mean value of ((Phi) over bar (Bo)) and standard deviation (sigma(s)) values found from the slope and intercept of this plot as 1.176 eV and 0.152 V, respectively. Thus, the modified (ln(I-o/T-2) - (q sigma(s))(2)/2(kT)(2) versus (q/kT) plot gives the (Phi) over bar (Bo) and effective Richardson constant A* as 1.115 eV and 31.94 A.(cm.K)(-2), respectively. This value of A* (= 31.94 A.(cm.K)(-2)) is very close to the theoretical value of 32 A.(cm.K)(-2) for p-Si. Therefore, the forward bias I-V-T characteristics confirmed that the current-transport mechanism (CTM) in Au/V-doped PVC+TCNQ/p-Si structures can be successfully explained in terms of the thermionic emission (TE) mechanism with a Gaussian distribution (GD) of BHs at around mean BH.