I–V–T analysing an inhomogeneous Au/Poly(4-vinyl phenol)/p-Si structure with a double Gaussian distribution of barrier heights

Abstract

In this study, the current–voltage (I–V) characteristics of Au/Poly(4-vinyl phenol)/p-Si structures have been measured over a wide temperature range (100–300 K). These structures have been analyzed according to thermionic emission (TE) theory, as a result of which an abnormal decrease occurred in the zero-bias barrier height ( $$ \phi_{b0} $$ ) and an increase in the ideality factor (n) was observed with temperature decrease and nonlinearity in the activation energy plot. By assuming a Gaussian distribution (GD) of barrier heights of the Au/Poly(4-vinyl phenol)/p-Si structures, barrier inhomogeneities are believed to responsible for this behavior. Evidence is given for the existence of a double GD with mean barrier heights ( $$ \bar{\phi }_{b0} $$ ) of 1.042 and 0.623 eV, standard deviations of 0.138 and 0.081 V, and ideality factors 2.76 and 7.26, which remain effective in the temperature ranges of 180–300 and 100–160 K, respectively. As a result, without using the temperature coefficient of the barrier height, the modified ln(I o /T 2) − q 2 σ 2 /2(kT)2 vs. q/kT plot gives $$ \bar{\phi }_{b0} $$ values and Richardson constants (A * ) as 1.036 and 0.623 eV, and 36.20 and 19.99 A/cm2 K2, respectively. The effective Richardson constant value of 36.20 A/cm2 K2 is very similar to the theoretical value of 32 A/cm2K2 for p-Si. Consequently, the temperature dependence of the forward bias I–V characteristics of Au/Poly(4-vinyl phenol)//p-Si (MIS) structure could be attributed to the thermionic emission (TE) mechanism with double GD of the barrier heights.