Wide Effective Work-Function Tuning of Al/SiO$_2$/Si Junction Achieved with Graphene Interlayer at Al/SiO$_2$ Interface

TL;DR

This study demonstrates a significant increase in the effective work-function of aluminum in a metal-oxide-semiconductor junction by inserting a graphene interlayer, enabling potential advancements in CMOS device engineering.

Contribution

The paper introduces a novel method of tuning aluminum's work-function using a graphene interlayer, supported by device-physical analysis and potential CMOS applications.

Findings

Effective work-function of Al increased by ~1.04 eV with graphene interlayer.

Electrical dipole layer formed at Al/graphene interface explains work-function tuning.

Feasibility of dual-metal gate CMOS circuitry using Al and graphene.

Abstract

The effective work-function of metal electrode is one of the major factors to determine the threshold voltage of metal/oxide/semiconductor junction. In this work, we demonstrate experimentally that the effective work-function of Aluminum (Al) electrode in Al/SiO$_2$/n-Si junction increases significantly by $\sim$1.04 eV with the graphene interlayer inserted at Al/SiO$_2$ interface. We also provide the device-physical analysis of solving Poisson equation when the flat-band voltage is applied to the junction, supporting that the wide tuning of Al effective work-function originates from the electrical dipole layer formed by the overlap of electron orbitals between Al and graphene layer. Our work suggests the feasibility of constructing the dual-metal gate CMOS circuitry just by using Al electrodes with area-specific underlying graphene interlayer.