| In present technology, the carbon nanotube based field effect transistors (CNTFET) are fabricated with Schottky barriers at the metal/nanotube contact. So far, only p-type CNTFET has been the prime focus of research. However, a digital circuit demands both n-type and p-type of devices. In this research work, a model has been proposed in view of the recent experimental demonstration using Calcium (Ca) as a contact metal to realize the n-type CNTFET. In order to fully optimize this proposed device model, effects of different parameters like the work function, oxide thickness, the oxide capacitance and the source velocity limits were studied. Among all the parameters, the work function of the contact metal plays an important role for controlling the flow of carriers through the carbon nanotube channel and to reduce the threshold voltage. A semi-classical simulation of the proposed n-type CNTFET has been performed. Results shows an excellent subthreshold swing value of 62.91 mV/decade, close to the ITRS specifications. A very good Ion/Ioff ratio is achieved that suggests the leakage current for the proposed device is quite low, making it possible to use this kind of device in VLSI circuits easily. The on-current value of the proposed model is 90% of the ballistic limits, which makes this device a potential candidate to replace current CMOS technology. |
