Due to the capability
of ballistic transport, carbon nanotube field-effect transistors
(CNTFETs) have been studied in recent years as a potential alternative
to CMOS devices. CNTFETs can be fabricated with Ohmic or Schottky type
contacts. Schottky barrier CNTFETs operate by modulating the
transmission coefficient of Schottky barriers at the contact between
the metal and the carbon nanotube (CNT) while the ohmic contact CNTFETs
operate like conventional FETs.
To understand and improve the behavior of CNTFETs, a Schrödinger
solver has been integrated into the device simulator Minimos-NT. The simulation results,
in good agreement with experimental results, indicate the ambipolar
behavior of Schottky barrier CNTFETs which limits the performance of
these devices. Based on the simulation result, we developed a double
gate structure which can suppress the ambipolar behavior of Schottky
barrier CNTFETs considerably. By coupling Minimos-NT to SIESTA, an optimization framework,
several CNTFET device characteristics optimizations have been
performed.
Due to the complexity of the operation of CNTFETs, more rigorous
methods
for the analysis of these devices are required. Among these methods is
the Non-Equilibrium Greens Function (NEGF) method which is becoming
more popular for the analysis of nano-scale devices. Future work
requires using more rigorous methods like the NEGF method for the
analysis of CNTFETs.
|