An atomistic quantum transport solver with dephasing for field-effect transistors

TL;DR

This paper introduces a versatile atomistic quantum transport solver incorporating dephasing effects, 3D electrostatics, and arbitrary contact geometries, demonstrated on a CNT-C60 device to model quantum transport phenomena.

Contribution

The paper presents a novel EHT-NEGF solver with self-consistent Born approximation for dephasing, including 3D electrostatics, applicable to diverse nano-scale devices.

Findings

Dephasing reduces the negative differential resistance peak.

The model accurately reproduces experimental characteristics.

Application to CNT-C60 device demonstrates effectiveness.

Abstract

Extended Huckel theory (EHT) along with NEGF (Non-equilibrium Green's function formalism) has been used for modeling coherent transport through molecules. Incorporating dephasing has been proposed to theoretically reproduce experimental characteristics for such devices. These elastic and inelastic dephasing effects are expected to be important in quantum devices with the feature size around 10nm, and hence an efficient and versatile solver is needed. This model should have flexibility to be applied to a wide range of nano-scale devices, along with 3D electrostatics, for arbitrary shaped contacts and surface roughness. We report one such EHT-NEGF solver with dephasing by self-consistent Born approximation (SCBA). 3D electrostatics is included using a finite-element scheme. The model is applied to a single wall carbon nanotube (CNT) cross-bar structure with a C60 molecule as the active channel. Without dephasing, a negative differential resistance (NDR) peak appears when the C60 lowest unoccupied molecular orbital level crosses a van Hove singularity in the 1D density of states of the metallic CNTs acting as contacts. This NDR diminishes with increasing dephasing in the channel as expected.