On the origin of contact resistances in graphene devices fabricated by optical lithography

Chavarin, Carlos Alvarado; Sagade, Abhay A.; Bacher, G.; Mertin, W.

doi:10.1007/s00339-015-9582-5

Cited by 18 publications

(19 citation statements)

References 23 publications

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“…The change of device resistance between measurements is related to a change in the doping level due to the absorption or desorption of adsorbates on the graphene, as the devices were not encapsulated and measurements were performed under ambient conditions. The measured device resistance of 127 Ω to 240 Ω for a 50 µm wide and 1.8 µm long two terminal device can be explained well by a sheet resistance of order 1 kΩ and a contact resistance of the order of several kΩµm, which is are typical values for graphene devices fabricated using optical lithography [25].The low frequency response of the photodetectors was measured with a lock-in amplifier at 1 kHz and a modulated laser source at 1550 nm. A photo current was only present in the case of an external bias voltage showing a negative sign with respect to the DC current.…”

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confidence: 75%

Graphene photodetectors with a bandwidth >76 GHz fabricated in a 6″ wafer process line

Schall¹,

Porschatis²,

Otto³

et al. 2017

J. Phys. D: Appl. Phys.

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In recent years, the data traffic has grown exponentially and the forecasts indicate a huge market that could be addressed by communication infrastructure and service providers. However, the processing capacity, space, and energy consumption of the available technology is a serious bottleneck for the exploitation of these markets. Chip-integrated optical communication systems hold the promise of significantly improving these issues related to the current technology. At the moment, the answer to the question which material is best suited for ultrafast chip integrated communication systems is still open. In this manuscript we report on ultrafast graphene photodetectors with a bandwidth of more than 76 GHz well suitable for communication links faster than 100 GBit/s per channel. We extract an upper value of 7.2 ps for the timescale in which the bolometric photoresponse in graphene is generated. The photodetectors were fabricated on 6" silicon-on-insulator wafers in a semiconductor pilot line, demonstrating the scalable fabrication of high-performance graphene based devices.Optical communication in general and especially chip integration of optic and electronic components has been considered as a promising way to significantly increase the performance of datalinks in terms of capacity, energy consumption, and costs [1][2][3]. The current bottleneck that hinders the mass production of chip integrated electro-optic components like modulators and photodetectors is the lack of a material that is compatible to established processing technology of chips while giving high performance devices. The electronic and optic properties of graphene [4], the two dimensional allotrope of carbon, were studied extensively in the last years [5][6][7][8][9]. Moreover, competitive chipintegrated electro-optical devices like electro-optical modulators [10,11], efficient waveguide heaters [12] and ultrafast photodetectors [13][14][15][16] were fabricated using graphene as active material. The performance of graphene photodetectors on integrated silicon waveguides in terms of speed and sensitivity has improved significantly in the last years and the gap between the performance of graphene and competing technologies is vanishing [17][18][19][20][21]. The possible monolithic integration on various substrates that are not necessarily crystalline is a key merit that distinguishes graphene from Ge or III/V materials. The bandwidth reported for graphene photodetectors of up to 65 GHz [16] and sensitivity around 0.4 A/W without bias and 1 A/W with bias [22] underline the potential of graphene for chip integrated photodetectors. Besides an excellent device performance the integration in a large scale production environment is essential. However, the introduction of new materials into an existing fabrication process flow and the required adoption as well as development of entirely new process steps are among the most challenging tasks in the fabrication of integrated circuits. So far, graphene photodetectors on silicon waveguides were fabrica...

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mentioning

confidence: 75%

Graphene photodetectors with a bandwidth >76 GHz fabricated in a 6″ wafer process line

Schall¹,

Porschatis²,

Otto³

et al. 2017

J. Phys. D: Appl. Phys.

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“…We find a contact resistance of 4400 Ωμm, which corresponds to the reported minimum for optical lithography. 47 …”

Section: Resultsmentioning

confidence: 99%

Catalyst Interface Engineering for Improved 2D Film Lift-Off and Transfer

Wang

Whelan

Braeuninger‐Weimer

et al. 2016

ACS Appl. Mater. Interfaces

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The mechanisms by which chemical vapor deposited (CVD) graphene and hexagonal boron nitride (h-BN) films can be released from a growth catalyst, such as widely used copper (Cu) foil, are systematically explored as a basis for an improved lift-off transfer. We show how intercalation processes allow the local Cu oxidation at the interface followed by selective oxide dissolution, which gently releases the 2D material (2DM) film. Interfacial composition change and selective dissolution can thereby be achieved in a single step or split into two individual process steps. We demonstrate that this method is not only highly versatile but also yields graphene and h-BN films of high quality regarding surface contamination, layer coherence, defects, and electronic properties, without requiring additional post-transfer annealing. We highlight how such transfers rely on targeted corrosion at the catalyst interface and discuss this in context of the wider CVD growth and 2DM transfer literature, thereby fostering an improved general understanding of widely used transfer processes, which is essential to numerous other applications.

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“…The negative threshold voltage and the high subthreshold swing indicate that a further reduction of debris is essential for high performance TFTs with laser patterned graphene electrodes. Once this is achieved the laser process is favorable compared to conventional patterning by UV lithography avoiding doping of the graphene electrodes due to resist residues [13].…”

Section: Discussionmentioning

confidence: 99%

“…The handling and processing of graphene, however, still represents a great challenge, since several processing steps induce an unwanted modification of the material properties. For example, the use of photoresists or polymer films on graphene for photolithography and/or transfer processes cause chemical doping of the layer [9][10][11][12][13] or patterning with e-beam lithography hydrogenates the graphene basal plane causing defects [14]. The necessary post-processing cleaning step in Ar/H 2 at 250 − 400 • C for removing polymer residues can also lead to graphene degradation [15].…”

Section: Introductionmentioning

confidence: 99%

Femtosecond laser patterning of graphene electrodes for thin-film transistors

Kasischke

Subaşı

Bock

et al. 2019

Applied Surface Science

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Email address: kasischke@lat.rub.de (Maren Kasischke) The aim of this study is to assess femtosecond laser patterning of graphene in air and in vacuum for the application as source and drain electrodes in thin-film transistors (TFTs). The analysis of the laser-patterned graphene with scanning electron microscopy, atomic force microscopy and Raman spectroscopy showed that processing in vacuum leads to less debris formation and thus re-deposited carbonaceous material on the sample compared to laser processing in air. It was found that the debris reduction due to patterning in vacuum improves the TFT characteristics significantly. Hysteresis disappears, the mobility is enhanced by an order of magnitude and the subthreshold swing is reduced from S sub = 2.5 V/dec to S sub = 1.5 V/dec.

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On the origin of contact resistances in graphene devices fabricated by optical lithography

Cited by 18 publications

References 23 publications

Graphene photodetectors with a bandwidth >76 GHz fabricated in a 6″ wafer process line

Graphene photodetectors with a bandwidth >76 GHz fabricated in a 6″ wafer process line

Catalyst Interface Engineering for Improved 2D Film Lift-Off and Transfer

Femtosecond laser patterning of graphene electrodes for thin-film transistors

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