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

摘要

Metal-semiconductor contacts are a pillar of modern semiconductor technology.Historically, their microscopic understanding has been hampered by theinability of traditional analytical and numerical methods to fully capture thecomplex physics governing their operating principles. Here we introduce anatomistic approach based on density functional theory and non-equilibriumGreen's function, which includes all the relevant ingredients required to modelrealistic metal-semiconductor interfaces and allows for a direct comparisonbetween theory and experiments via I-V bias curves simulations. We apply thismethod to characterize an Ag/Si interface relevant for photovoltaicapplications and study the rectifying-to-Ohmic transition as function of thesemiconductor doping.We also demonstrate that the standard "Activation Energy"method for the analysis of I-V bias data might be inaccurate for non-idealinterfaces as it neglects electron tunneling, and that finite-size atomisticmodels have problems in describing these interfaces in the presence of doping,due to a poor representation of space-charge effects. Conversely, the presentmethod deals effectively with both issues, thus representing a validalternative to conventional procedures for the accurate characterization ofmetal-semiconductor interfaces.