Voltage dependence of effective barrier height reduction in inhomogeneous Schottky diodes

The Schottky barrier height (SBH) variation and its dependence on applied voltage for NiSi/n-Si Schottky diodes with different SBH inhomogeneities have been studied by temperature-dependent current-voltage technique. The results show that the effective barrier height is strongly dependent on the SBH inhomogeneity and the applied voltage. The reduction of effective barrier height increases as the bias varies from forward to reverse, indicating that the pinch off, or more precisely saying, the presence of saddle point in the depletion region, does strongly affect the current transport. Under low reverse bias, the SBH reduction is proportional to one-fourth power of the band bending, which indicates that strip-like SBH inhomogeneity rather than patch-like SBH inhomogeneity exists in our samples. The strip region parameter ω is determined to be 1.63 × 10−3 and 3.21 × 10−3 V−1/2 cm−1/2 for the two diodes respectively. Under high reverse bias, the SBH reduction shows different behaviours for diodes with different SBH inhomogeneity. For diodes with small inhomogeneity, the SBH reduction increases faster than the one-fourth power of the band bending while for diodes with large inhomogeneity, the reduction increases more slowly than in the low reverse bias region. The reason is also explained in term of pinch off.