Properties of short channel ballistic carbon nanotube transistors with ohmic contacts

TL;DR

This paper uses advanced simulations to analyze short channel ballistic carbon nanotube transistors with ohmic contacts, revealing how contact properties and quantum effects influence device behavior.

Contribution

It provides a detailed theoretical analysis of contact effects and quantum tunneling in short channel CNT transistors, aligning with recent experimental findings.

Findings

Band lineup is renormalized by charge transfer, affecting contact type.

Source-drain tunneling and barrier lowering impact current-voltage characteristics.

ON state conductance exhibits temperature dependence without phonon scattering.

Abstract

We present self-consistent, non-equilibrium Green's function calculations of the characteristics of short channel carbon nanotube transistors, focusing on the regime of ballistic transport with ohmic contacts. We first establish that the band lineup at the contacts is renormalized by charge transfer, leading to Schottky contacts for small diameter nanotubes and ohmic contacts for large diameter nanotubes, in agreement with recent experiments. For short channel ohmic contact devices, source-drain tunneling and drain-induced barrier lowering significantly impact the current-voltage characteristics. Furthermore, the ON state conductance shows a temperature dependence, even in the absence of phonon scattering or Schottky barriers. This last result also agrees with recently reported experimental measurements.