  Behaviour of hot electrons under the influence of dc field in carbon
nanotubes is theoretically considered. The study was done semi-classically by
solving Boltzmann transport equation with the presence of the hot electrons
source to derive the current densities. Plots of the normalized axial current
density versus electric field strength of the chiral CNTs reveal a negative
differential conductivity (NDC). Unlike achiral CNTs, the NDC occurs at a low
field about $\mathrm{6\ kV/cm}$ for chiral CNT. We further observed that the
switch from NDC to PDC occurs at lower dc field in chiral CNTs than achiral
counterparts. Hence the suppression of the unwanted domain instability usually
associated with NDC and a potential generation of terahertz radiations occurs
at low electric field for chiral CNTs.
