Current crowding mediated large contact noise in graphene field-effect transistors.

Paritosh Karnatak,Arindam Ghosh,Srijit Goswami,T Phanindra Sai,Sanjeev Kaushal,Subhamoy Ghatak

doi:10.1038/ncomms13703

Abstract

The impact of the intrinsic time-dependent fluctuations in the electrical resistance at the graphene–metal interface or the contact noise, on the performance of graphene field-effect transistors, can be as adverse as the contact resistance itself, but remains largely unexplored. Here we have investigated the contact noise in graphene field-effect transistors of varying device geometry and contact configuration, with carrier mobility ranging from 5,000 to 80,000 cm2 V−1 s−1. Our phenomenological model for contact noise because of current crowding in purely two-dimensional conductors confirms that the contacts dominate the measured resistance noise in all graphene field-effect transistors in the two-probe or invasive four-probe configurations, and surprisingly, also in nearly noninvasive four-probe (Hall bar) configuration in the high-mobility devices. The microscopic origin of contact noise is directly linked to the fluctuating electrostatic environment of the metal–channel interface, which could be generic to two-dimensional material-based electronic devices.

Highlights

The impact of the intrinsic time-dependent fluctuations in the electrical resistance at the graphene–metal interface or the contact noise, on the performance of graphene field-effect transistors, can be as adverse as the contact resistance itself, but remains largely unexplored
While it is clear that current crowding and the characteristics of the metal–graphene junction directly influence the contact resistance[25,29,34,36,37,38,39,40,41,42], how these factors have an impact on the noise originating at the contacts is still not known
In this work we study a series of graphene field-effect transistor (FET) with different mobilities, substrates and contacting configurations to demonstrate that electrical noise at the metal–graphene junction can be the dominant source of 1/f noise in graphene FETs, especially for invasive contacting geometry, where the probe contacts lie directly in the path of the current flow

Summary

Introduction

The impact of the intrinsic time-dependent fluctuations in the electrical resistance at the graphene–metal interface or the contact noise, on the performance of graphene field-effect transistors, can be as adverse as the contact resistance itself, but remains largely unexplored. Conflicting claims exist, where some studies attribute the 1/f noise in graphene transistors primarily to noise generated within the channel region[7,8,9], whereas other investigations indicate a strong contribution from the contacts[10,11,12] This distinction has remained elusive to existing studies[7,8,9,10,11,12,13,14,15,16,17,18,19,20,21] because of the lack of a microscopic understanding of how processes characteristic to the metal–graphene junctions, in particular the current-crowding effect[22,23,24,25,26,27], has an impact on the nature and magnitude of 1/f noise. In view of the recent observations of contact noise[43,44] and currentcrowding effect in molybdenum disulphide (MoS2) and black phosphorus FETs26,27, many of the results and concepts developed in this paper can be extended to other members of 2D semiconductor family as well

Methods

Results

Conclusion