Graphene integrated on wafer scale marks step towards next-gen photonics

Among other applications, graphene has the potential to enhance photonics devices. Graphene-enabled photonic devices absorb light from ultraviolet to the far-infrared parts of the spectrum, allowing for ultra-broadband communications. They can also have ultra-high carrier mobility, enabling vast data transmission speeds, breaking the barrier of 100Gbps.

The growth of graphene-enabled photonic devices could allow engineers to work around the size and cost limitations that apply to classical devices and pave the way to a new generation of telecommunications and datacom devices. Graphene-based photonic devices – which allow almost all light energy to be converted into electric signals, maximising efficiency – could also be crucial for reducing the energy demands of information and communication technologies, which are associated with a steadily growing carbon footprint.

A study by Graphene Flagship researchers describes a wafer-scale fabrication technology which – thanks to predetermined graphene single-crystal templates – allows for integration into silicon wafers. This renders the process compatible with existing automated fabrication systems, allowing for mass production in the future.

“Traditionally, when aiming at wafer-scale integration, one grows a wafer-sized layer of graphene and then transfers it onto silicon,” said Dr Camille Coletti, coordinator of the Instituto Italiano di Tecnologia Graphene Labs. “Transferring an atom-thick layer of graphene over wafers while maintaining its integrity and quality is challenging.”

“The crystal seeding, growth and transfer technique adopted in this work ensures wafer-scale high-mobility graphene exactly where it is needed: a great advantage for the scalable fabrication of photonic devices like modulators.”

According to estimates, by 2023 the world may contain over 28 billion connected devices, most of which will require 5G connectivity and push at the limits of existing technology.

“Silicon and germanium alone have limitations; however, graphene provides many advantages,” said Marco Romagnoli, of the Consorzio Nazionale Interuniversitario per le Telecomunicazioni. “This methodology allows us to obtain over 12,000 graphene crystals in one wafer, matching the exact configuration and disposition we need for graphene-enabled photonic devices.”

A separate Graphene Flagship study used this technique it to design high-speed graphene photodetectors.

Frank Koppens, who leads the Graphene Flagship in photonics and optoelectronics, commented: “This is the first time that high-quality graphene has been integrated on the wafer-scale. The work shows direct relevance by revealing high-yield and high-speed absorption modulators. These impressive achievements bring commercialisation of graphene devices into 5G communications very close”