Graphene FETs in Microwave Applications
Doktorsavhandling, 2012

Graphene is a one-atom-thick sheet of carbon with numerous impressive properties. It is a promising material for future high-speed nanoelectronics due to its intrinsic superior carrier mobility and very high saturation velocity. These exceptional carrier transport properties suggest that graphene field effect transistors (G-FETs) can potentially outperform other FET technologies. This doctoral thesis presents the realisation of G-FET circuits at microwave frequencies (0.3-30 GHz) with emphasis on a novel subharmonic resistive mixer. The work covers device manufacturing, modelling, circuit design, and characterisation. The developed mixer exploits the G-FETs ability to conduct current in both n-channel and p-channel modes for subharmonic (×2) mixing. Consequently, the mixer operates with a single transistor and unlike the conventional subharmonic resistive FET mixers, it does not need any balun at the local oscillator (LO) port. In addition, the mixer has potential to operate unbiased. These aspects enable us to utilise G-FET subharmonic mixers in compact high frequency heterodyne detectors. A 30 GHz mixer is realised in microstrip technology on a 250 μm high resistivity silicon substrate. A conversion loss (CL) of 19 ± 1 dB in the frequency range of 24 to 31 GHz is obtained with an LO to RF isolation better than 20 dB. For designing and analysing G-FET circuits a closed-form semiempirical largesignal model is proposed and experimentally verified under both DC and RF operation. The model is implemented in a standard Electronic Design Automation (EDA) software for device-circuit co-design. By using the model, the first G-FET microwave amplifier is realised. The amplifier exhibits a small-signal power gain of 10 dB at 1 GHz.

microwave amplifiers

S-parameters characterisation

device modelling


device fabrication


subharmonic resistive mixers

integrated circuits

harmonic balance analysis

microwave FETs

MC2, Kollektorn
Opponent: Prof. Tomas Palacios


Omid Habibpour

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

10 dB small-signal graphene FET amplifier

Electronics Letters,; Vol. 48(2012)p. 861-863

Artikel i vetenskaplig tidskrift

Resistive Graphene FET Subharmonic Mixers: Noise and Linearity Assessment

IEEE Transactions on Microwave Theory and Techniques,; Vol. 60(2012)p. 4035-4042

Artikel i vetenskaplig tidskrift

A 30-GHz Integrated Subharmonic Mixer based on a Multichannel Graphene FET

IEEE Transactions on Microwave Theory and Techniques,; Vol. 61(2013)p. 841-847

Artikel i vetenskaplig tidskrift

A Large Signal Graphene FET Model

IEEE Transactions on Electron Devices,; Vol. 59(2012)p. 1567-1567

Artikel i vetenskaplig tidskrift

A subharmonic graphene FET mixer

IEEE Electron Device Letters,; Vol. 33(2012)p. 71-73

Artikel i vetenskaplig tidskrift

Mobility Improvement and Microwave Characterization of a Graphene Field Effect Transistor With Silicon Nitride Gate Dielectrics

IEEE Electron Device Letters,; Vol. 32(2011)p. 871-873

Artikel i vetenskaplig tidskrift


Electronic devices are traditionally and mainly made from silicon. Carbon-based electronics, however, offer a number of exciting properties and may be considered as a complement to or extension of the existing silicon-based technology. Specifically, graphene, a single atom layer of carbon, is considered to be one of the materials of choice for future high frequency nanoelectronics due to the very high electron speed in graphene. The current research project aims to realise electronic circuits based on graphene field effect transistors (G-FETs), at microwave frequencies (0.3-30 GHz). A new type of high frequency signal detector has been proposed, which take advantage of unique properties in graphene. Using a G‐FET in this new topology enables us to extend its operation to higher frequencies thereby exploiting the exceptional properties of graphene. Since this type of mixer has potential to operate without DC bias, it can be a promising candidate for compact heterodyne detector arrays. This paves the way for future technologies operating at extremely high frequencies. In addition, in order to be able to use standard circuit simulation softwares for designing and analysing circuits based on G-FETs, a device model is developed. The model can be easily implemented which allows simulation of complete circuits. By utilising the model, the first microwave signal amplifier based on G-FET is designed.


Informations- och kommunikationsteknik

Nanovetenskap och nanoteknik




Annan elektroteknik och elektronik



Technical report MC2 - Department of Microtechnology and Nanoscience, Chalmers University of Technology: 234

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 3458

MC2, Kollektorn

Opponent: Prof. Tomas Palacios