The analysis of I– V characteristics of Schottky diodes by thermionic emission with a Gaussian distribution of barrier height

Abstract

The current–voltage ( I– V) characteristics of Al/p-Si Schottky barrier diode (SBD) with native insulator layer were measured in the temperature range of 178–440 K. The estimated zero-bias barrier height Φ B 0 and the ideality factor n assuming thermionic emission (TE) theory have shown strong temperature dependence. Evaluation of the forward I– V data have revealed an increase of zero-bias barrier height Φ B 0 but the decrease of ideality factor n with the increase in temperature. The experimental and theoretical results of the tunneling current parameter E o against kT/ q were plotted to determine predominant current-transport mechanism. But the experimental results were found to be disagreement with the theoretical results of the pure TE, the thermionic-field emission (TFE) and the field emission (FE) theories. The conventional Richardson plot has exhibited non-linearity below 240 K with the linear portion corresponding to the activation energy of 0.085 eV and Richardson constant ( A * ) value of 2.48 × 10 −9 A cm −2 K −2 which is much lower than the known value of 32 A cm −2 K −2 for holes in p-type Si. Such behaviours were attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution of barrier heights (BHs) due to barrier height inhomogeneities that prevail at interface. Thus, the modified ln( I o / T 2) − q2σ o2/2 k 2 T 2 vs q/kT has plotted. Then A * was calculated as 38.79 A cm −2 K −2 without using the temperature coefficient of the barrier height. This value of the Richardson constant 38.79 A cm −2 K −2 is very close to the theoretical value of 32 A K −2 cm −2 for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I– V characteristics of the Al/p-Si Schottky barrier diodes with native insulator layer can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights.