Comparison of energy relaxation in one-dimensional thermionic and tunneling transistors

We compare energy relaxation in 1-D tunnel field-effect transistors (FETs) vs. thermionic FETs, focusing on carbon nanotubes (CNTs). In CNTs the strongest inelastic scattering process with optical phonons has very high energy, n¿_OP ¿ 0.18 eV, three times higher than in Si. We find the energy relaxation rate in tunnel FETs is up to 20 times slower than in thermionic FETs for ~1000 ¿A/¿m current and -0.3 eV band gap, when most carriers are injected below the OP energy. More generally, this relaxation rate depends on band gap, phonon energy, inelastic scattering rate, and desired drive current. The results have strong implications for the design of new, low-energy transistors based on non-equilibrium tunneling transport.