Graphene boosts next-generation telecom and datacom devices

An international team of researchers from the Graphene Flagship have developed new graphene-integrated photodetectors – micro-devices used to convert light to electrical signals – with enhanced performance. 

The team consisted of researchers from Istituto Italiano di Tecnologia (IIT), the University of Pisa and Consorzio Nazionale Interuniversitario per le Telecomunicazioni (CNIT) in Italy, the Technion in Israel, the Institute of Photonic Sciences (ICFO) in Spain, Thales in France, and the University of Cambridge in the United Kingdom.

In our increasingly connected world, graphene-enabled photodetectors have the potential to overcome limitations in the datacom and telecom sectors by providing high-efficiency, lower-cost devices. Graphene's lack of a band gap, combined with its high charge carrier mobility, makes it ideal for high-speed and broadband optical communications with high rates of data transfer. 

To improve power consumption and noise performance, Graphene Flagship researchers constructed photodetectors that take advantage of the photo-thermoelectric effect: the light absorbed by a single layer graphene sheet on top of a silicon nitride layer generates an electrical signal. By confining the light absorption to a narrow region of the graphene channel, the device's structure improved the responsivity while maintaining a high-speed of at least 42 GHz.

"We obtained this promising result with graphene constructed using chemical vapor deposition (CVD). This results in better reproducibility and scalability than exfoliated graphene flakes," explains Jakob Ewald Muench at the University of Cambridge. 

The scientists developed another set of devices with a dielectric spacer, which was made of polyvinyl alcohol, deposited between two CVD graphene sheets by spin-coating, and integrated on a silicon nitride waveguide. Thanks to the dielectric spacer, the team obtained a high carrier mobility of more than 16,000 cm²/Vs and an operation speed of 67 GHz: the highest values recorded to-date for this type of device.

"To disrupt photonic technologies, we need to demonstrate graphene-enabled high-performing devices on a standard platform – which is what this work shows. We adopted scalable materials and demonstrated ultrafast photodetectors on a realistic photonic platform," says Marco Romagnoli, researcher at CNIT and Leader of the Graphene Flagship's Wafer-scale System Integration Work Package. 

"Thanks to the Graphene Flagship, we were able to move from proof-of-concept devices to the demonstration of scalable photonic building blocks. In the future, we will continue to concentrate on further improving the device performance and, of course, making sure the devices are compatible with industrial requirements," comments Camilla Coletti, coordinator of Graphene Labs at IIT in Pisa.

Amaia Zurutuza, Deputy Leader of the Graphene Flagship's Wafer-scale System Integration Work Package, adds: "These latest results demonstrate that we are advancing in the right direction to move graphene from the lab to the industry. The next step will be to demonstrate the performance of these devices on the wafer scale." 

"These studies show the power of graphene for optoelectrical applications and highlight the progress made in bringing graphene to the market. These achievements exemplify graphene's potential over many conventional materials," comments Kari Hjelt, Head of Innovation at the Graphene Flagship. 

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Romagnoli, Marco, et al. "Graphene-based integrated photonics for next-generation datacom and telecom." Nature Reviews Materials 3.10 (2018): 392-414.

Koppens, F. H. L., et al. "Photodetectors based on graphene, other two-dimensional materials and hybrid systems." Nature nanotechnology 9.10 (2014): 780-793.

Bonaccorso, Francesco, et al. "Graphene photonics and optoelectronics." Nature photonics 4.9 (2010): 611.

Muench, Jakob E., et al. "Waveguide-integrated, plasmonic enhanced graphene photodetectors." Nano letters19.11 (2019): 7632-7644.

Mišeikis, Vaidotas, et al. "Ultrafast, Zero-Bias, Graphene Photodetectors with Polymeric Gate Dielectric on Passive Photonic Waveguides." ACS nano 14.9 (2020): 11190-11204.