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Paolo Pedrinazzi: Ultra-low contact resistance in graphene devices

posted 6 Jul 2016, 06:36 by info admin
Paolo Pedrinazzi,[1] Luca Anzi,[1] Marco Fiocco, [1] Erica Guerriero, [1] Aida Mansouri,[1] Ashkan Behnam,[2] Enrique A. Carrion,[2] Amaia Pesquera,[3] Alba Centeno,[3] Amaia Zurutuza,[3] Eric Pop,[4] Roman Sordan [1]
[1] L-NESS, Department of Physics, Politecnico di Milano, Via Anzani 42, 22100 Como, Italy 
[2] Electrical and Computer Engineering, University of Illinois, Urbana IL 61801, USA
[3] Graphenea, Avenida de Tolosa 76, 20018 Donostia/San Sebastián, Spain
[4] Electrical Engineering, Stanford University, Stanford, CA 94305, USA

Graphene is one of the possible contenders in high-frequency electronics, mainly due to its high charge carrier mobility and velocity saturation, which exceed that of conventional highmobility semiconductors. Scalable production techniques, such as CVD, can now deliver graphene on a large scale which is interesting from the industrial point of view. One of the main parameters degrading high-frequency response of GFETs is contact resistance which should be reduced below 100 Ωµm to reach that of conventional high-frequency transistors. 

Here we demonstrate graphene/metal contacts with a typical contact resistance of 80 Ωµm at the Dirac point. The contact resistance was determined by transmission line measurements (TLMs) at room temperature. The low contact resistance was obtained by etching holes in CVD-grown graphene before the deposition of contacts. This increases the contact edge with metal contacts deposited on top and therefore the injection of carriers at the graphene edges [1,2]. Pure Au contacts were used without any adhesion layer or thermal treatment. The lowest contact resistance was 72 Ωµm. Such ultra-low contact resistance is comparable to that of InP THz transistors [3] and provides a viable route to high-frequency GFETs.

[1] J. T. Smith et al., ACS Nano 7, 3661 (2013).
[2] S. Song et al., Appl. Phys. Lett. 104, 183506 (2014)
[3] R. Lai et al., Int. El. Devices Meet. pp. 609–611 (2007)

Paolo Pedrinazzi is currently a PhD student in Physics at Politecnico di Milano, Milan, Italy. He is primarily interested in the electrical and optical properties of atomically thin materials such as graphene and hBN. He received his bachelor and master degree in Physics from University of Pavia (2010 and 2013) where he studied the electrical properties at low temperatures and Raman properties of graphene during his master thesis, partially done at the University of Salamanca, Salamance, Spain. During his Ph.D, he is spending 6 months in the Nanocarbon Group at Nanotech Department at DTU studying the stacking methods for the fabrication of Van der Walls heterostructures of graphene and hBN and their electrical properties.