Enhanced high-frequency performance of top-gated graphene FETs due to substrate-induced improvements in charge carrier saturation velocity
Journal article, 2021

High-frequency performance of top-gated graphene field-effect transistors (GFETs) depends to a large extent on the saturation velocity of the charge car-riers, a velocity limited by inelastic scattering by surface optical phonons from the dielectrics surrounding the chan-nel. In this work, we show that by simply changing the graphene channel surrounding dielectric with a material having higher optical phonon energy, one could improve the transit frequency and maximum frequency of oscillation of GFETs. We fabricated GFETs on conventional SiO2/Si substrates by adding a thin Al2O3 interfacial buffer layer on top of SiO2/Si substrates, a material with about 30% higher optical phonon energy than that of SiO2, and compared performance with that of GFETs fabricated without adding the interfacial layer. From S-parameter measurements, a transit frequency and a maximum frequency of oscillation of 43 GHz and 46 GHz, respectively, were obtained for GFETs on Al2O3 with 0.5 µm gate length. These values are approximately 30% higher than those for state-of-the-art GFETs of the same gate length on SiO2. For relating the improvement of GFET high-frequency performance to improvements in the charge carrier saturation velocity, we used standard methods to extract the charge carrier veloc-ity from the channel transit time. A comparison between two sets of GFETs with and without the interfacial Al2O3 layer showed that the charge carrier saturation velocity had increased to 2·10^7 cm/s from 1.5·10^7 cm/s.

graphene

optical phonons

maximum frequency of oscillation

Field-effect transistors (FETs)

saturation velocity

transit frequency

Author

Muhammad Asad

Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory

Kjell Jeppson

Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory

Andrei Vorobiev

Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory

Marlene Bonmann

Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory

Jan Stake

Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory

IEEE Transactions on Electron Devices

0018-9383 (ISSN)

Vol. 68 2 899-902

Flexibla terahertz detektorer i grafen

Swedish Research Council (VR), 2018-01-01 -- 2021-12-31.

Carbon Based High Speed 3D GaN Electronics System

Swedish Foundation for Strategic Research (SSF), 2014-03-01 -- 2019-06-30.

Graphene Core Project 3 (Graphene Flagship)

European Commission (EC), 2020-04-01 -- 2023-03-31.

Areas of Advance

Information and Communication Technology

Nanoscience and Nanotechnology (SO 2010-2017, EI 2018-)

Infrastructure

Kollberg Laboratory

Nanofabrication Laboratory

Subject Categories

Electrical Engineering, Electronic Engineering, Information Engineering

Nano Technology

Other Electrical Engineering, Electronic Engineering, Information Engineering

DOI

10.1109/TED.2020.3046172

More information

Latest update

2/24/2021