The barrier height inhomogeneity in Al/p-Si Schottky barrier diodes with native insulator layer

Abstract

The current–voltage ( I– V) characteristics of Al/p-Si Schottky barrier diodes (SBDs) with native insulator layer were measured in the temperature range of 150–375 K. The estimated zero-bias barrier height Φ B0 and the ideality factor n assuming thermionic emission (TE) theory show strong temperature dependence. Evaluation of the forward I– V data reveals an increase of zero-bias barrier height Φ B0 but decrease of ideality factor n with increase in temperature. The conventional Richardson plot exhibits non-linearity below 250 K with the linear portion corresponding to activation energy of 0.41 eV and Richardson constant ( A *) value of 1.3 × 10 −4 A cm −2 K −2 is determined from intercept at the ordinate of this experimental plot, which is much lower than the known value of 32 A cm 2 K 2 for holes in p-type Si. Such behavior is attributed to Schottky barrier inhomogene ties by assuming a Gaussian distribution of barrier heights (BHs) due to barrier height inhomogeneities that prevail at interface. Also, Φ B0 versus q/2 kT plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and values of Φ B0 = 1.055 eV and σ 0 = 0.13 V for the mean BH and zero-bias standard deviation have been obtained from this plot, respectively. Thus, the modified ln ( I 0 / T 2 ) − q 2 σ o 2 / 2 k 2 T 2 versus q/ kT plot gives Φ B0 and A * as 1.050 eV and 40.08 A cm −2 K −2, respectively, without using the temperature coefficient of the barrier height. This value of the Richardson constant 40.03 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.