Role of Fermi-Level Pinning in Nanotube Schottky Diodes

At semiconductor-metal junctions, the Schottky barrier height is generally fixed by “Fermi-level pinning.” We find that when a semiconducting carbon nanotube is end contacted to a metal (the optimal geometry for nanodevices), the behavior is radically different. Even when the Fermi level is fully “pinned” at the interface, the turn-on voltage is that expected for an unpinned junction. Thus the threshold may be adjusted for optimal device performance, which is not possible in planar contacts. Similar behavior is expected at heterojunctions between nanotubes and semiconductors.