Low Resistive Edge Contacts to CVD‐Grown Graphene Using a CMOS Compatible Metal

Shaygan, Mehrdad; Otto, Martin; Sagade, Abhay A.; Chavarin, Carlos Alvarado; Bacher, G.; Mertin, W.

doi:10.1002/andp.201600410

Cited by 35 publications

(52 citation statements)

References 35 publications

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“…Round holes have also been investigated by Anzi et al for a large variety of metals including Au, Pd, silver (Ag), aluminum (Al), and nickel (Ni). The impact of the contact edges on a low contact resistance, has been confirmed by Kelvin probe force microscopy in Ni/Al contacts …”

Section: Introductionmentioning

confidence: 81%

Ultralow Specific Contact Resistivity in Metal–Graphene Junctions via Contact Engineering

Passi

Gahoi

Marín

et al. 2018

Adv Materials Inter

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A systematic investigation of graphene edge contacts is provided. Intentionally patterning monolayer graphene at the contact region creates well-defined edge contacts that lead to a 67% enhancement in current injection from a gold contact. Specific contact resistivity is reduced from 1372 Ωµm for a device with surface contacts to 456 Ωµm when contacts are patterned with holes. Electrostatic doping of the graphene further reduces contact resistivity from 519 Ωµm to 45 Ωµm, a substantial decrease of 91%. The experimental results are supported and understood via a multi-scale numerical model, based on density-functional-theory calculations and transport simulations. The data is analyzed with regards to the edge perimeter and hole-to-graphene ratio, which provides insights into optimized contact geometries. The current work thus indicates a reliable and reproducible approach for fabricating low resistance contacts in graphene devices.We provide a simple guideline for contact design that can be exploited to guide graphene and 2D material contact engineering.The extraordinary electronic, optoelectronic and mechanical properties of graphene make it a promising candidate as a technology booster for micro-and nanoelectronics applications.Examples include radio frequency electronics, 1,2 integrated photodetectors, 3-5 and nanoelectromechanical systems. 6,7 One of the major bottlenecks limiting the performance of graphene-based devices is the large and varying value of specific contact resistivity (R C ) between metal contact electrodes and graphene. [8][9][10][11] When a metal is brought into contact with graphene, a junction with high contact resistivity is created, typically attributed to the low density of states (DOS) in graphene in particular when the Fermi level is near the Dirac point. 11 Although abinitio calculations provide deeper insights into the contact problem, they also highlight the importance of the metal. 12-14 Experimentally, various methods have been reported to reduce R C : one of the most common approaches is post-metallization annealing. [15][16][17] Other methods aim to modify the graphene prior to metallization in a random manner, such as low power oxygen plasma etch (with or without post-metallization annealing), 18 ozone pre-treatment, 19 intentional doping of graphene below the contact metal, 20 and ion beam irradiation. 21,22 A more deterministic approach is the formation of "edge"-contacts, where the graphene under the contact is partially removed by lithographic methods to enable the formation of covalent bonds between graphene and metal. This idea was proposed by means of an ingenious contact geometry by Wang 23 . Subsequently, the partial removal of the graphene under the contact by lithography, plasma or ion bombardment allowed a more versatile contact design. In particular, Smith et al. 24 investigated edge patterning of graphene with rectangular cuts under palladium (Pd) and copper (Cu) contacts with the transfer length method (TLM). The conclusion of this study was extended by Park et a...

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Section: Introductionmentioning

confidence: 81%

Ultralow Specific Contact Resistivity in Metal–Graphene Junctions via Contact Engineering

Passi

Gahoi

Marín

et al. 2018

Adv Materials Inter

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“…assuming that the access resistance (R a ) is 6 Ω, which is calculated by using an access length of 200 nm, a contact resistance of 200 Ω·µm[22,23] and a sheet resistance of 1 kΩ/□. This would place the 1D-MIG diode among the fastest diodes available.To evaluate the 1D-MIG diode for the application in rectifiers or power detectors, the I-V characteristics was measured under ambient conditions(Figure 2a) and the typical figures of merit (FOMs) for diodes are extracted, in particular, the asymmetry of a diode defined as = | | , where J F and J R are the current density for forward and reverse bias, respectively, the nonlinearity as = ⁄ , where J is the current density of the diode, and the responsivity as = .…”

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confidence: 99%

Flexible One-Dimensional Metal–Insulator–Graphene Diode

Wang

Uzlu

Shaygan

et al. 2019

ACS Appl. Electron. Mater.

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In this work, a novel one-dimensional geometry for metal-insulator-graphene (1D-MIG) diode with low capacitance is demonstrated. The junction of the 1D-MIG diode is formed at the 1D edge of Al 2 O 3 -encapsulated graphene with TiO 2 that acts as barrier material. The diodes demonstrate ultra-high current density since the transport in the graphene and through the barrier is in plane. The geometry delivers very low capacitive coupling between the cathode and anode of the diode, which shows frequency response up to 100 GHz and ensures potential high frequency performance up to 2.4 THz. The 1D-MIG diodes are demonstrated to function uniformly and stable under bending conditions down to 6.4 mm bending radius on flexible substrate.

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“…where R mg is the metal/graphene junctions' resistance and R ung is the ungated region resistance. It can be shown, by separating the R ung , that the values of R mg are lower than those of the lowest previously published for both top and edge graphene/metal contacts, including perforated ones, which are typically above 100 • μm [33]- [36]. For comparison, the state-of-the-art silicon metal-oxidesemiconductor field-effect transistors (MOSFETs) require a contact resistivity of 80…”

Section: E Contact Resistancementioning

confidence: 89%

The Dependence of the High-Frequency Performance of Graphene Field-Effect Transistors on Channel Transport Properties

Asad

Bonmann

Yang

et al. 2020

IEEE J. Electron Devices Soc.

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This paper addresses the high-frequency performance limitations of graphene field-effect transistors (GFETs) caused by material imperfections. To understand these limitations, we performed a comprehensive study of the relationship between the quality of graphene and surrounding materials and the high-frequency performance of GFETs fabricated on a silicon chip. We measured the transit frequency (f T) and the maximum frequency of oscillation (f max) for a set of GFETs across the chip, and as a measure of the material quality, we chose low-field carrier mobility. The low-field mobility varied across the chip from 600 cm 2 /Vs to 2000 cm 2 /Vs, while the f T and f max frequencies varied from 20 GHz to 37 GHz. The relationship between these frequencies and the low-field mobility was observed experimentally and explained using a methodology based on a small-signal equivalent circuit model with parameters extracted from the drain resistance model and the charge-carrier velocity saturation model. Sensitivity analysis clarified the effects of equivalent-circuit parameters on the f T and f max frequencies. To improve the GFET high-frequency performance, the transconductance was the most critical parameter, which could be improved by increasing the charge-carrier saturation velocity by selecting adjacent dielectric materials with optical phonon energies higher than that of SiO 2. INDEX TERMS Graphene, field-effect transistors, high frequency, transit frequency, maximum frequency of oscillation, microwave electronics, contact resistances, transconductance.

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Low Resistive Edge Contacts to CVD‐Grown Graphene Using a CMOS Compatible Metal

Cited by 35 publications

References 35 publications

Ultralow Specific Contact Resistivity in Metal–Graphene Junctions via Contact Engineering

Ultralow Specific Contact Resistivity in Metal–Graphene Junctions via Contact Engineering

Flexible One-Dimensional Metal–Insulator–Graphene Diode

The Dependence of the High-Frequency Performance of Graphene Field-Effect Transistors on Channel Transport Properties

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