The distribution of the barrier height in Al–TiW–Pd2Si/n-Si Schottky diodes from I–V–T measurements

Abstract

The forward and reverse bias current–voltage (I–V) characteristics of Al–TiW–Pd2Si/n-Si Schottky barrier diodes (SBDs) were measured in the temperature range of 300–400 K. The estimated zero-bias barrier height ΦB0 and the ideality factor n assuming thermionic emission (TE) theory show a strong temperature dependence. While n decreases, ΦB0 increases with increasing temperature. The Richardson plot is found to be linear in the temperature range measured, but the activation energy value of 0.378 eV and the Richardson constant (A*) value of 15.51 A cm−2 K−2 obtained in this plot are much lower than the known values. Such behavior is attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution of barrier heights (BHs) due to BH inhomogeneities that prevail at the interface. Also, the ΦB0 versus q/2kT plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and ΦB0 = 0.535 eV and σ0 = 0.069 V for the mean BH and zero-bias standard deviation, respectively, have been obtained from this plot. Thus, the modified ln(I0/T2) − q2σ20/2k2T2 versus q/kT plot gives ΦB0 and A* as 0.510 eV and 121.96 A cm−2 K−2, respectively. This value of the Richardson constant 121.96 A cm−2 K−2 is very close to the theoretical value of 120 A K−2 cm−2 for n-type Si. Hence, it has been concluded that the temperature dependence of the forward I–V characteristics of the Al–TiW–Pd2Si/n-Si Schottky barrier diodes can be successfully explained on the basis of a thermionic emission mechanism with a Gaussian distribution of the BHs.