Carbon Nanotubes as Schottky Barrier Transistors
S. Heinze, J. Tersoff, R. Martel, V. Derycke, J. Appenzeller, and Ph.Avouris
IBM Research Division, US
Keywords: carbon nanotubes, nanoelectronics
The demonstration of field-effect transistors (FETs) using carbon nanotubes (CNs) as channels [1,2] has caused much hope for new nanoscale devices. Although great progress has been made in the fabrication of such devices [3,4] the theoretical understanding has been limited. Initially, it was assumed that transistor action occurred in a manner analogous to ordinary silicon based FETs. Recently, however, there has been increasing experimental evidence that the Schottky Barrier (SB) formed at the contact between the metallic electrodes and the carbon nanotube may play an important role in the device characteristics [4-7].
Here we show that the existence of a substantial SB leads to the operation of the CN-FET by the modulation of the contact resistance rather than the channel conductance. The potential of such SB-FETs for further device miniaturization has already been proposed for silicon technology . Using a semiclassical model we explore the characteristics of carbon nanotube SB-FETs. We show that a number of essential experimental observations can be understood within this model, e.g. the effect of doping and the non-ideal switching behavior. We can further clarify the role of adsorbed gases, showing that they affect the device characteristics by changing the metal work function rather than by doping the nanotube as had been generally believed. By comparing different device geometries we point out the key role of the contact geometry in determining the device performance.
NSTI Nanotech 2003 Conference Technical Program Abstract