The fabrication of single-walled carbon nanotube field-effect transistors (CNTFETs) has been the subject of extensive research, but challenges remain. The yield of well performing devices is often low because currently there is no effective way to separate metallic carbon nanotubes, which shunt FET characteristics, from semiconducting tubes, which are the active elements of the device.
To solve this problem, researchers at Alabama A&M University and the Center for Functional Nanomaterials at Brookhaven National Laboratory have replaced metal electrodes for semiconducting ones in CNTFETs. The reason for this substitution resides in the current-blocking action produced by the back-to-back metal–semiconductor junctions formed at the interfaces between semiconducting electrodes and metallic nanotubes. This current-blocking action electrically isolates metallic nanotubes and as a result improves the performance of the device.
The figure above shows a schematic of the CNTFET with semiconducting (Sb2Te3 or Bi2Te2Se) source/drain contacts. IV curves are pMOS-like and have a higher on/off drain-source current ratio at large drain-source voltages and better saturation of drain-source current with increasing drain-source voltage than curves from reference devices fabricated with gold source/drain contacts. The researchers believe that the fabrication processes can be applied to other semiconductor electrode materials and could be employed in future wafer-scale CNTFET-based nanoelectronic circuits.
The researchers presented their work in Nanotechnology.