Analytical study of non-linear transport across a semiconductor-metal junction

Abstract

In this paper we study analytically a one-dimensional model for a semiconductor-metal junction.We study the formation of Tamm states and how they evolve when the semi-infinite semiconductor and metal are coupled together. The non-linear current, as a function of the bias voltage, is studied using the non-equilibrium Green's function method and the density matrix of the interface is given. The electronic occupation of the sites defining the interface has strong non-linearities as function of the bias voltage due to strong resonances present in the Green's functions of the junction sites. The surface Green's function is computed analytically by solving a quadratic matrix equation, which does not require adding a small imaginary constant to the energy. The wave function for the surface states is given.The electronic properties of surfaces and interfaces has many fascinating features, associated with the formation of surface states, modification of the band structure and corresponding density of states, and electronic transport [1]. Strongly localized surface states are known since a long time to be present at the interface of semiconductors and metals [2] and have been shown to influence the conductance of scanning tunneling microscopy (a quasione-dimensional process) [3]. Also these states have re-

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