6G Communications needs graphene. 6G will initially launch at a few hundred GHz where several diode and transistor technologies are available in the laboratory but things get tough when second-generation 6G operates at around 1THz to get the ultimate response time, data capacity, data transfer and other promised advances.
This will coincide with 6G adding promised user benefits that can only come by handling higher power. The later 6G Reflective Intelligent Surfaces RIS everywhere will do more than smarten up and redirect the beams but actually amplify them, charging your phone and operating devices with no power. Making, manipulating and using the beams all potentially benefit from graphene, the total graphene opportunity being in the IDTechEx report, ‘Graphene Market & 2D Materials Assessment 2021-2031’.
Fit-and-forget graphene supercapacitors will often replace batteries as 6G devices need less power. These supercapacitors excel in energy and power density leveraging graphene’s excellent conductivity, huge area density and compatibility with best-performing new electrolytes. Pseudocapacitors promise even more. Most of their research involves graphene. See the IDTechEx report, ‘Supercapacitor Materials and Formats 2020-2040’.
Desired THz electronics necessarily become smaller and thinner. Heat dissipation then adds to the challenges so graphene’s area density, heat conduction, thinness and electrical conductivity are some of the reasons for its appeal in planned 6G communications. Indeed, graphene is a candidate both in the 6G active devices and the metamaterials essential to the manufacture of smart surfaces to get the feeble beams through. 6G cannot succeed without widely deployed reprogrammable intelligent surfaces RIS and they cannot succeed unless made as metasurfaces affordably collimating, polarising and redirecting beams with almost no electricity. Both the sub-wavelength patterning and the integrated active devices are candidates for graphene. See the IDTechEx report, ‘6G Communications Reconfigurable Intelligent Surfaces Roadmap, Materials, Market 2021-2045’.
New wide-bandwidth plasmonic antennas are intrinsically small, efficiently operating at THz. Contrary to electronic and optical technologies relying on up-conversion of microwave and mm-wave signals or down-conversion of optical signals, direct generation of THz signals is possible in hybrid graphene/3-5 semiconductor devices. Efficiency increases by lack of energy loss through harmonics. 100 times smaller than traditional metallic antennas, they easily embed. Their frequency response can be electronically reprogrammed.
One efficient THz Schottky-diode detection scheme employs epitaxial graphene on silicon carbide. Biological and chemical sensors can be manufactured this way – relevant to 6G because it is intended to have ubiquitous sensing and positioning at its heart.
A German-Spanish research team revealed its gold-covered graphene to better generate THz pulses possibly in CMOS for 6G. Epitaxial graphene on GaN promises functional electronics, single-molecule electronics, plasmonics and phononics and detection of ultra-fast electronic processes.
Little wonder that the EU Graphene Technology and Innovation Roadmap predicts graphene-enabled on-chip optical data, spin-logic devices and 6G networks will be in development in 2030. 1THz second-stage 6G gets very serious preparation then.
Due to unique band structure, the conductivity of graphene can be dynamically modulated optically or electrically creating reprogrammable electric and optoelectronic devices. A new type of optical transistor – a working THz amplifier – uses graphene and a high-temperature superconductor. Here graphene excels in transparency, insensitivity to light and massless electrons. Double graphene with a superconductor traps graphene electrons. THz radiation hits powered graphene making trapped particles inside attach to outgoing waves, amplifying them.
NAIST Korea and others demonstrate real-time modulation of wave amplitude and phase in reflection and transmission. Graphene is patterned into an array of nanoribbons exciting localised THz plasmon resonance with a trade‐off between graphene carrier mobility or relaxation time and efficiency.
Appropriate structures tightly localise incident fields enhancing graphene light-matter interaction potentially for 6G reprogrammable intelligent surfaces RIS everywhere. Graphene’s THz conductivity can be modified by an optical pump altering the carrier concentration and energy distribution. Recently, a variety of optically stimulated graphene‐based tunable metasurfaces have been proposed. See the IDTechEx report, ‘6G Communications Market, Devices, Materials 2021-2041’.
THz dynamically-controlled graphene multifunctional metasurfaces are appearing experimentally. One large array of graphene reflective unit cells has them controlled independently by size and external static gate voltage realising multi-functionality. The so-called graphene field-effect transistor is another THz focus.
Raghu Das, IDTechEx CEO, summarises, “6G systems may become a trillion-dollar business. Exploiting a variety of benefits, graphene may be used for the metasurfaces, supercapacitors and various active components involved. Near term IDTechEx forecasts for open-market graphene sales remain modest partly because 6G applications kick in from 2030 at the earliest and much of the graphene employed will be made in the process as with epitaxial growth. Graphene supercapacitor manufacturers often make their own and anyway these are currently only a few per cent of the supercapacitor market.”