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

摘要

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 Phi(BO) 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 Phi(BO) 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 X 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, Phi(BO) versus q/2kT plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and values of Phi(BO) = 1.055 eV and sigma(0) = 0.13 V for the mean BH and zero-bias standard deviation have been obtained from this plot, respectively. Thus, the modified In (I-0/T-2) - q(2)sigma(2)(0)/2k(2)T(2) versus q/kT plot gives Phi(BO) 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. (c) 2005 Elsevier B.V. All rights reserved.