TITLE: Connecting Metals and Semimetals to Semiconductors: The Ubiquity of Schottky Barriers and Tunnel Junctions
ABSTRACT: It is widely recognized that interfaces between metals and most semiconductors form Schottky barriers with rectifying properties that are essential components of present-day electronics. This talk will begin with a tutorial overview of Schottky barriers and describe the physical concepts that are necessary and sufficient to gain a working understanding of their operation. Research will then be described which uncovers surprising phenomenology that points to new physics and novel device concepts. These phenomena include magnetodielectric coupling in nonmagnetic Au/GaAs:Si Schottky barriers, the formation of Schottky barriers at the interface of one-atom-thick zero-gap semiconductors (graphene), and the Schottky barriers formed by contacting freshly exfoliated flakes of van der Waals crystals such as Bi2Se3, a topological insulator, and layered chalcogenides to doped Si and GaAs wafers. Interestingly, modifications to the thermionic emission equation provide an excellent description of current-voltage characteristics at low temperatures where tunneling is known to be important, thereby providing a segue to a full tunneling description. Temperature, frequency and magnetic field dependence of current-voltage and capacitance-voltage characteristics will be described.