Two-dimensional Cold Electron Transport for Steep-slope Transistors

TL;DR

This paper introduces a graphene-enabled cold electron injection technique that significantly improves the subthreshold swing and current density in 2D MoS2 transistors, surpassing traditional steep-slope transistor limits at room temperature.

Contribution

It presents a novel 2D Dirac-source cold electron transistor that achieves record-high current density and sub-60 mV/decade switching by utilizing cold electrons from graphene.

Findings

Achieved a subthreshold swing of 29 mV/decade at room temperature.

Realized a record-high current density over 1 μA/μm.

Demonstrated effective electron cooling with an electron temperature of ~145 K.

Abstract

Room-temperature Fermi-Dirac electron thermal excitation in conventional three-dimensional (3D) or two-dimensional (2D) semiconductors generates hot electrons with a relatively long thermal tail in energy distribution. These hot electrons set a fundamental obstacle known as the "Boltzmann tyranny" that limits the subthreshold swing (SS) and therefore the minimum power consumption of 3D and 2D field-effect transistors (FETs). Here, we investigated a novel graphene (Gr)-enabled cold electron injection where the Gr acts as the Dirac source to provide the cold electrons with a localized electron density distribution and a short thermal tail at room temperature. These cold electrons correspond to an electronic cooling effect with the effective electron temperature of ~145 K in the monolayer MoS2, which enable the transport factor lowering and thus the steep-slope switching (across for 3 decades with a minimum SS of 29 mV/decade at room temperature) for a monolayer MoS2 FET. Especially, a record-high sub-60-mV/decade current density (over 1 {\mu}A/{\mu}m) can be achieved compared to conventional steep-slope technologies such as tunneling FETs or negative capacitance FETs using 2D or 3D channel materials. Our work demonstrates the great potential of 2D Dirac-source cold electron transistor as an innovative steep-slope transistor concept, and provides new opportunities for 2D materials toward future energy-efficient nanoelectronics.