Since the first demonstration of electroluminescence (EL) from a CNTFET about three year ago, significant progress
has been achieved in CNT optoelectronics. We have developed semiclassical and quantum transport simulators for
CNT optoelectronic devices. A self-consistent simulation, which couples a quantum treatment of the metal-CNT
contacts to a semiclassical treatment of the channel, is performed to understand carrier transport and light emission in a
CNT infrared emitter. The results show that when the channel is long, light emission significantly affects carrier
transport, and reduces the source-drain current by a factor of 2 in ambipolar transport regime. The experimentally
observed light-spot movement along the channel can be mostly understood and explained by a simple, semiclassical
picture. The photoconductivity of carbon nanotube (CNT) Schottky barrier transistors is studied by solving the nonequilibrium
Green's function transport equation. The model provides a detailed and coherent picture of electron-photon
coupling and quantum transport effects. The photocurrent shows peaks at photon energies near the subband gaps, which
can be engineered by controlling the CNT diameter. Electron-phonon coupling (i) slightly broadens the peaks, (ii) leads
to phonon-assisted photocurrent at certain energy ranges, and (iii) changes the energy-resolved photocurrent. We also
show that the metal/CNT barrier height has a much smaller effect on the photocurrent than on the dark current. We also
show the important role of sub-bandgap impact ionization and excitation in CNT devices.
Beyond 65 nm node, the ultra-narrow channel memory device serves as a possible technology for further scaling. A self-assembled carbon nanotube (CNT) channel with self aligned metal nanocrystals is proposed as an alternative to Si based ultra-narrow channel memory. The device demonstrates large memory window and single-electron sensitivity. The analysis of the transport in the CNT channel using non-equilibrium Green's function (NEGF) formalism confirms single electron sensitivity quantitatively at room temperature. The CNT channel conductance exhibits sensitivity to position of the charge along the channel. The NEGF based analysis is easily extended to the application of CNTFET as a charge sensor. The electrostatics of the CNT-nanocrystal memory was analyzed for transport between nanocrystal and CNT. Despite the nanocrystal being in close proximity of the CNT, it is strongly coupled to the gate electrode electrostatically. This effect is not observed in the planar 2D Si- based nanocrystal memory. It obviates a major trade-off in memory design of scaling the control dielectric to decrease operational voltage, while ensuring low gate leakage and should allow ultra-low voltage operations. Large tunneling current should also enhance write times. Large electric field asymmetry should enable a better write/retention ratio.