Metal-induced gap states model of nonideal Au/Si Schottky barrier with low defect density

Abstract

Temperature dependence of current–voltage characteristics was investigated on Au/n-Si Schottky barrier. The experimental current density can be represented by a modified equation of the thermionic emission, in which nearly the same ideality factors n Φ and n v appear in the temperature dependent exponential term of the barrier height Φ B and in that of the applied voltage V, respectively. Origin of n Φ is considered to be spatially inhomogeneous Schottky barrier height distribution. Origin of n v is considered to be applied bias dependence of the effective barrier height. A microscopic model of the inhomogeneity based on the MIGS model is proposed. Positively charged defects close to interface but outside the evanescent tail of MIGS produce local lowering of barrier height due to induced charge density, which depends on a distance of the defect from interface. The local barrier height lowering is restored by disappearance of the defect charge under forward bias. This model is applicable to interfaces of defect density lower than 10 14 cm −2, which has been considered to be necessary for the Fermi level pinning.