Metal contacts in carbon nanotube field effect transistors: Beyond the Schottky barrier paradigm

TL;DR

This study uses first-principles calculations to analyze how different metal contacts, specifically Au and Pd, affect the electrical behavior of carbon nanotube transistors, revealing that Pd provides perfect hole injection.

Contribution

It provides the first direct numerical evidence that Pd contacts can be perfectly transparent for hole injection, challenging the traditional Schottky barrier paradigm.

Findings

Pd contacts exhibit perfect transparency for hole injection

Schottky barrier heights are similar for Au and Pd contacts

Contacts actively influence the device I-V behavior

Abstract

The observed performances of carbon nanotube field effect transistors are examined using first-principles quantum transport calculations. We focus on the nature and role of the electrical contact of Au and Pd electrodes to open-ended semiconducting nanotubes, allowing the chemical contact at the surface to fully develop through large-scale relaxation of the contacting atomic configuration. We present the first direct numerical evidence of Pd contacts exhibiting perfect transparency for hole injection as opposed to that of Au contacts. Their respective Schottky barrier heights, on the other hand, turn out to be fairly similar for realistic contact models. These findings are in general agreement with experimental data reported to date, and show that a Schottky contact is not merely a passive ohmic contact but actively influences the device I-V behavior.