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

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 space radiation and nuclear radiation are known to cause defects in solids. 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. We investigate how the amplitude of the RTS noise is affected by the composite structure of gate insulators, which contains an inner insulator with a dielectric constant larger than 3.9 and an outer insulator with a dielectric constant of 3.9 (as for SiO2). 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. Due to strong effects of defects in CNFETs, CNFETs have a potential to be used for detecting the space radiation or nuclear radiation.