The distribution of the barrier height in Al-TiW-Pd2Si/n-Si Schottky diodes from I-V-T measurements
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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 Phi(B0) and the ideality factor n assuming thermionic emission ( TE) theory show a strong temperature dependence. While n decreases, Phi(B0) 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 Phi(B0) versus q/2kT plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and Phi(B0) = 0.535 eV and sigma(0) = 0.069 V for the mean BH and zero-bias standard deviation, respectively, have been obtained from this plot. Thus, the modified ln(I-0/T-2) - q(2)sigma(0)(2)/2k(2)T(2) versus q/kT plot gives Phi(B0) 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.