Challenges from quantum capacitance in process of high performance carbon nanotube-FETs design

Due to effective elimination of carriers band-to-band tunneling through channel-source/drain interface, Dual-Gate-Material MOS-like Carbon Nanotube Field Effect Transistors (DGMC-CNFETs), proposed by our research group previously, can not only increase the ON-OFF current ratio, tune sub-threshold voltage, decrease device power, but also eliminate the ambipolar transporting property effectively. However, as a typical low-dimension system, DGMC-CNFETs suffer from effects of quantum capacitance inevitably. The effect of quantum capacitance on device band profile and thus the transporting characteristic is studied. Simulation results show that quantum capacitance can not only result in a great increase of OFF current, but also prevent sub-threshold swing from decreasing with the increase of insulator capacitance. What´s more important is that, due to the appearance of band-to-band tunneling at gate electrode-tuning electrode interface, quantum capacitance can even destroy the unipolar transporting property of this novel device design, which would have a negative impact on its application in circuits. At last, several suggestions are given to reduce the effects of quantum capacitance on the performance of DGMC-CNFETs.