Charge carrier velocity in graphene field-effect transistors
Artikel i vetenskaplig tidskrift, 2017

To extend the frequency range of transistors into the terahertz domain, new transistor technologies, materials, and device concepts must be continuously developed. The quality of the interface between the involved materials is a highly critical factor. The presence of impurities can degrade device performance and reliability. In this paper, we present a method that allows the study of the charge carrier velocity in a field-effect transistor vs impurity levels. The charge carrier velocity is found using high-frequency scattering parameter measurements followed by delay time analysis. The limiting factors of the saturation velocity and the effect of impurities are then analysed by applying analytical models of the field-dependent and phonon-limited carrier velocity. As an example, this method is applied to a top-gated graphene field-effect transistor (GFET). We find that the extracted saturation velocity is ca. 1.4×10^7 cm/s and is mainly limited by silicon oxide substrate phonons. Within the considered range of residual charge carrier concentrations, charged impurities do not limit the saturation velocity directly by the phonon mechanism. Instead, the impurities act as traps that emit charge carriers at high fields, preventing the current from saturation and thus limiting power gain of the GFETs. The method described in this work helps to better understand the influence of impurities and clarifies methods of further transistor development. High quality interfaces are required to achieve current saturation via velocity saturation in GFETs.

Graphene

Dielectric materials

Phonons

FETs

Charge transfer

Electronic transport

transistors

Författare

Marlene Bonmann

Chalmers, Mikroteknologi och nanovetenskap (MC2), Terahertz- och millimetervågsteknik

Andrei Vorobiev

Chalmers, Mikroteknologi och nanovetenskap (MC2), Terahertz- och millimetervågsteknik

MICHAEL ANDERSSON

Chalmers University of Technology

Jan Stake

Chalmers, Mikroteknologi och nanovetenskap (MC2), Terahertz- och millimetervågsteknik

Applied Physics Letters

0003-6951 (ISSN) 1077-3118 (eISSN)

Vol. 111 233505- 233505

Styrkeområden

Informations- och kommunikationsteknik

Nanovetenskap och nanoteknik

Infrastruktur

Kollberglaboratoriet

Nanotekniklaboratoriet

Ämneskategorier

Nanoteknik

Annan elektroteknik och elektronik

DOI

10.1063/1.5003684