Negative Fermi-Level Pinning Effect Observed in Metal/GaAs Junction with Graphene Insertion Layer

Abstract

We report the negative Fermi-level pinning effect observed experimentally in metal/graphene/n-GaAs(001) junction, supported by the Schottky barrier decreasing as metal work-function increasing. The low interface-trap density regions, protected by the graphene insertion layer, are found to have the local Schottky barrier affected directly by the interaction dipole layer at metal/graphene contact. The polarity of interaction dipole layer, indicating the position of interacting electrons, is likely to be determined by the interplay of exchange repulsion and electronegativity difference between metal and carbon atoms. Our work shows that the graphene insertion layer can invert efficiently the effective metal work-function between high and low, making it possible to form both Schottky and Ohmic-like contacts with identical (particularly high work-function) metal electrodes on a semiconductor substrate possessing low surface-state density.