  Optical emission from carbon nanotube transistors (CNTFETs) has recently
attracted significant attention due to its potential applications. In this
paper, we use a self-consistent numerical solution of the Boltzmann transport
equation in the presence of both phonon and exciton scattering to present a
detailed study of the operation of a partially suspended CNTFET light emitter,
which has been discussed in a recent experiment. We determine the energy
distribution of hot carriers in the CNTFET, and, as reported in the experiment,
observe localized generation of excitons near the trench-substrate junction and
an exponential increase in emission intensity with a linear increase in current
versus gate voltage. We further provide detailed insight into device operation,
and propose optimization schemes for efficient exciton generation; a deeper
trench increases the generation efficiency, and use of high-k substrate oxides
could lead to even larger enhancements.
