Inhomogeneous Schottky barriers at Ag/Si(111) and Ag/Si(100) interfaces

We have measured current-voltage and capacitance-voltage characteristics of epitaxial Si(111)7x7-Ag, Si(111)(root 3x root 3)R30 degrees-Ag, Si(100)2x1-Ag, and polycrystalline Ag/Si interfaces, using different doping levels for both n- and p-type silicon wafers. Our data strongly suggest that the Schottky barrier heights (SBHs) are spatially nonuniform. The distribution of local effective SBHs at the epitaxial interfaces is modeled by a summation of a single Gaussian, representing the spread in SBH for the majority of the contact, and two half-Gaussians which represent the high- and low-barrier tails of the full distribution. Despite the fact that the average SBHs of the epitaxial interfaces are hardly structure dependent, the SBH distributions are very broad and markedly different for each interface. The polycrystalline interfaces are characterized by a narrower SBH distribution centered at a substantially smaller mean. We argue that the electrical inhomogeneity is related to structural inhomogeneity at the interface which is a direct consequence of the kinetics and mode of growth of Ag on Si. (C) 1996 American Institute of Physics.