After Demonstrating Its Worth in Electronics Applications, Graphene Tackles Optoelectronics

Graphene's peculiar properties are being managed in ways that make the wonder material possibly ideal for many electronic and optoelectronic applications

2 min read
After Demonstrating Its Worth in Electronics Applications, Graphene Tackles Optoelectronics

Graphene has been on a run of sorts over the last few years, consistently amazing researchers with its capabilities. And in the past few months, it all seems to have accelerated when it comes to electronics applications.

IBM has been behind two of the most recent major breakthroughs. One being the creation of a band gap in graphene and the other a graphene transistor twice as fast as silicon chips.

It still may be a few years off before we see graphene-based transistors in our computers since improvements to large-scale graphene production is still needed as well as the band gap issue to be further addressed as Phaedon Avouris, IBM Fellow and Manager, Nanometer Scale Science & Technology noted to us in our recent interview with him.

However, the work in this area is progressing and has a relative maturity. But the field of optoelectronics is opening up now too as an application area for graphene. Researchers at the University of Cambridge in the UK and CNRS in Grenoble, France have created an ultrafast "mode-locked" graphene laser that would be suitable for optoelectronic applications.

While IBM may have solved the band gap problem, it appears that the UK and French researchers were surprised that their device worked despite not having a band gap, which is the key feature that allows typical “mode-locked” lasers made from semiconductor saturable absorber mirrors (SESAMs) to operate.

Strange indeed and indicative of how far we still need to go in understanding the fundamentals of how some of these nanomaterials, like graphene, operate. Nonetheless the researchers were able to fabricate a device with “the most wideband saturable light absorber ever”.

As the Institute of Physics article cited above describes the process of fabrication:

“The team studied how light is absorbed in graphene and how photo-excited charge carriers behave in the material. In particular, they highlighted the key role of "Pauli blocking" in saturating the light absorption. Because of the Pauli exclusion principle, when pumping of electrons in the excited state is quicker than the rate at which they relax, the absorption saturates. This is because no more electrons can be excited until there is "space" available for them in the excited state.

Since the Dirac electrons in graphene linearly disperse, this means that it is the most wideband saturable light absorber ever, far out-passing the bandwidth provided by any other known material.” 

It seems as though graphene’s strange properties just keep knocking off one electronic application after another.

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3D-Stacked CMOS Takes Moore’s Law to New Heights

When transistors can’t get any smaller, the only direction is up

10 min read
An image of stacked squares with yellow flat bars through them.
Emily Cooper

Perhaps the most far-reaching technological achievement over the last 50 years has been the steady march toward ever smaller transistors, fitting them more tightly together, and reducing their power consumption. And yet, ever since the two of us started our careers at Intel more than 20 years ago, we’ve been hearing the alarms that the descent into the infinitesimal was about to end. Yet year after year, brilliant new innovations continue to propel the semiconductor industry further.

Along this journey, we engineers had to change the transistor’s architecture as we continued to scale down area and power consumption while boosting performance. The “planar” transistor designs that took us through the last half of the 20th century gave way to 3D fin-shaped devices by the first half of the 2010s. Now, these too have an end date in sight, with a new gate-all-around (GAA) structure rolling into production soon. But we have to look even further ahead because our ability to scale down even this new transistor architecture, which we call RibbonFET, has its limits.

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