Eur. Phys. J. B (2014) 87: 233
https://doi.org/10.1140/epjb/e2014-50443-3

Regular Article

Effects of a single defect in composite gate insulators of carbon nanotube transistors

Department of Microelectronic Science and Engineering, Science Faculty, Ningbo University, Fenghua Road 818, 315211 Ningbo, P.R. China

^a e-mail: wangnengping@nbu.edu.cn

Received: 30 June 2014
Received in final form: 21 August 2014
Published online: 15 October 2014

Abstract

The current through a carbon nanotube field-effect transistor (CNFET) with cylindrical gate electrode is calculated using the nonequilibrium Greens function method in a tight-binding approximation. The obtained result is in good agreement with the experimental data. The theoretical approach is used to calculate the amplitude of the random-telegraph-signal (RTS) noise due to a single defect in the gate oxide of a long channel p-type CNFET. Considering a composite structure of gate insulators, which contains an inner insulator with a large dielectric constant (ϵ > 3.9) and an outer insulator with a dielectric constant of 3.9 (as for SiO₂), the dependence of the RTS noise amplitude on the structure of composite gate insulators is investigated. It is found that the RTS amplitude increases apparently with the decreasing thickness of the inner gate insulator. If the inner insulator is too thin, even though its dielectric constant is as large as 80, the amplitude of the RTS noise caused by the charge of Q = +1e may amount to around 80% in the turn-on region.