Electrical Properties of Metal/4H-SiC Junction Modulated by Graphene Insertion Layer

Abstract

We study the electrical characteristics of metal/graphene/SiC junctions by investigating the Schottky barriers for two different metal (Ti, Au) electrodes. The Fermi-level pinning for Schottky junctions on SiC (Silicon Carbide) are known to be relatively weak. However, by inserting a graphene layer at the interface, the Schottky barrier shows the inverse dependence on the metal work function, which leads to the so-called negative Fermi-level pinning. This unusual effect is confirmed from current-voltage (I-V), internal photoemission (IPE), and capacitance-voltage (C-V) measurements. Interestingly, the Schottky barriers of metal/graphene/SiC junctions extracted from C-V measurements are somewhat larger than the barriers obtained from other measurements, considered to be related to the charge carrier transfer into the graphene layer. Additionally, we observe two energy barriers originating from the crystal field splitting of SiC in the IPE measurements and they exist commonly for both metal/SiC and metal/graphene/SiC junctions.