Characteristics of Interlayer Tunneling Field Effect Transistors Computed by a "DFT-Bardeen" Method

TL;DR

This paper employs a DFT-Bardeen method to predict current-voltage characteristics of 2D heterojunction TFETs, revealing material-dependent variations and highlighting the importance of wavefunction origins in tunneling efficiency.

Contribution

It introduces a first-principles DFT-Bardeen approach for modeling interlayer tunneling in 2D TFETs, allowing material-specific predictions and analysis of contact resistance effects.

Findings

Significant variation in tunneling currents depending on material combinations.

Gamma-point states generally produce larger currents than K-point states.

Predicted currents and subthreshold swings align with low-power application benchmarks.

Abstract

Theoretical predictions are made for the current-voltage characteristics of two-dimensional heterojunction interlayer tunneling field-effect transistors (Thin-TFETs), focusing on the magnitude of the current that is achievable in such devices. A theory based on the Bardeen tunneling method is employed, using wavefunctions from first-principles density-functional theory. This method permits convenient incorporation of differing materials into the source and drain electrodes, i.e. with different crystal structures, lattice constants, and/or band structures. Large variations in the tunnel currents are found, depending on the particular two-dimensional materials used for the source and drain electrodes. Tunneling between states derived from the center (Gamma-point) of the Brillouin zone (BZ) is found, in general, to lead to larger current than for zone-edge (e.g. K-point) states. Differences, as large as an order of magnitude, between the present results and various prior predictions are discussed. Predicted values for the tunneling currents, including subthreshold swing, are compared with benchmark values for low-power digital applications. Contact resistance is considered and its effect on the tunneling currents is demonstrated.