General atomistic approach for modeling metal-semiconductor interfaces using density functional theory and non-equilibrium Green's function

TL;DR

This paper introduces an atomistic modeling approach combining density functional theory and non-equilibrium Green's function to accurately simulate metal-semiconductor interfaces, addressing limitations of traditional methods and enabling direct comparison with experimental I-V data.

Contribution

The paper presents a novel atomistic method that effectively models realistic metal-semiconductor interfaces, including doping effects and electron tunneling, surpassing traditional analytical and numerical techniques.

Findings

Accurately characterizes Ag/Si interfaces relevant for photovoltaics.

Demonstrates limitations of the 'Activation Energy' method for non-ideal interfaces.

Shows the new approach effectively accounts for space-charge effects and tunneling.

Abstract

Metal-semiconductor contacts are a pillar of modern semiconductor technology. Historically, their microscopic understanding has been hampered by the inability of traditional analytical and numerical methods to fully capture the complex physics governing their operating principles. Here we introduce an atomistic approach based on density functional theory and non-equilibrium Green's function, which includes all the relevant ingredients required to model realistic metal-semiconductor interfaces and allows for a direct comparison between theory and experiments via I-V bias curves simulations. We apply this method to characterize an Ag/Si interface relevant for photovoltaic applications and study the rectifying-to-Ohmic transition as function of the semiconductor doping.We also demonstrate that the standard "Activation Energy" method for the analysis of I-V bias data might be inaccurate for non-ideal interfaces as it neglects electron tunneling, and that finite-size atomistic models have problems in describing these interfaces in the presence of doping, due to a poor representation of space-charge effects. Conversely, the present method deals effectively with both issues, thus representing a valid alternative to conventional procedures for the accurate characterization of metal-semiconductor interfaces.