Performance comparison of zero-Schottky-barrier single and double walled carbon nanotube transistors

Atomistic quantum simulation is performed to compare the performance of zero-Schottky-barrier single walled (SW) and double walled (DW) carbon nanotube transistors having almost equal magnitude of band gap. The DW nanotube is generated from two semiconducting SW tubes and the SW tube is the outer tube of the DW nanotube. The DW nanotube transistor has better off current, better inverse subthreshold slope, and better on/off current ratio. The SW nanotube transistor has better on current and switching performance. The better switching performance of SW nanotube transistor is the consequence of higher transconductance and on current that results from current saturation in DW nanotube transistor after source-channel flat band condition. The inverse subthreshold slope of DW nanotube transistor is 63.11 mV/dec and that of SW nanotube transistor is 65.26 mV/dec. The on-state transconductance is 21.0963 muS and 1.5023 muS, the intrinsic switching delay is 33.6415 fS and 55.0184 fS, respectively for SW and DW nanotube transistors.