Breaking the Silicon Barrier: Walt de Heer's Semiconducting Graphene Innovation

Breaking the Wall of Moore's Law

Winner Interview 2024: Engineering & Technology

Walt de Heer is revolutionizing electronics with semiconducting epigraphene. Overcoming the limitations of silicon, his pioneering research focuses on developing graphene grown on silicon carbide, promising a new era in high-performance, low-energy electronics.

Which wall does your research or project break?

Moore’s law accurately predicted the doubling of the performance of silicon electronics every 18 months starting in 1960. The inevitable end to this exponential increase, which we are hitting now, is appropriately known in the industry as the “Red Brick Wall”, which future technologies will have to overcome in order that we will continue to prolong this trend. Specifically, silicon electronics components cannot be made much smaller, energy consumption is unsustainable, and speeds are reaching physical limits. However silicon is not the only material that can be used for electronics. Since the 1990’s there have been world-wide searches for alternative electronics platforms that go beyond the conventional silicon electronics paradigm.

In 2001 my colleagues and I focused on graphene, which is a single sheet of carbon atoms, as a possible successor of silicon. This pioneering work resulted in the first graphene electronics patent in 2003.

In the meantime, others also recognized the potential of graphene and it was awarded a Nobel prize in 2010. However, graphene is not a semiconductor and efforts to convert it to semiconductor had failed for 2 decades.

From the outset the efforts at Georgia Tech focused on epigraphene which is graphene that is grown on silicon carbide. Together with our collaborators at the Tianjin International Center for Nanoparticles and Nanostructures, which was created by my ex-postdoc, Prof. Lei Ma and me, we succeeded in producing semiconducting graphene. This so-called semiconducting epigraphene, is a 2-dimensional semiconductor with excellent properties that may introduce a new era in electronics.

Semiconducting epigraphene research is still in its infancy and many technical hurdles still need to be overcome before our dream of graphene electronics is realized, but the most important step in that direction has been achieved.

What are the three main goals of your research or project?

From its inception in 2001, our primary goal was to find a viable successor to silicon  which was known to hit its fundamental limits around 2020. Silicon is a ubiquitous semiconductor that is used in the vast majority of electronic devices. While it is not the only semiconductor that is used in electronics its properties turned out to be particularly well suited for a variety of reasons. In fact, many proposed alternative electronics schemes do not use semiconductors at all but rather rely on the quantum mechanical wave properties of electrons as well as their magnetic properties.

Graphene itself is not a semiconductor, but a (semi)metal. However, it was theoretically demonstrated that graphene nanoribbons would have semiconducting like properties so that these ribbons could in principle be used in more or less conventional electronics architectures. Our initial plan was to produce semiconducting graphene nanoribbons that were seamlessly  interconnected with  metallic graphene. This architecture has enormous advantages since it would avoid interconnecting graphene with conventional metals, like copper or aluminum.

This was our initial goal, which we ultimately failed to achieve since we could not produce the semiconducting epigraphene nanoribbons.

Alternatively it  was long known that under specific conditions, graphene on silicon carbide (epigraphene) had semiconducting properties. While our initial experiments at Georgia Tech showed that the semiconducting graphene invariably was too disordered so that it was not useful, followup work at the TICNN significantly enhanced the quality of semiconducting graphene, as was ultimately demonstrated in a series of experiments.

Following this demonstration,  main three goals of our research are

1.     To demonstrate a semiconducting epigraphene field effect transistor that significantly surpasses the silicon transistor.

2.     To demonstrate rudimentary epigraphene devices that rely on the quantum mechanical wave properties of the electrons.

3.     To demonstrate seamlessly interconnected epigraphene nanoscale devices that have very low power dissipation and operate at very high frequencies.

Achieving these three goals will bring us significantly closer to epigraphene nanoelectronics.

What advice would you give to young scientists or students interested in pursuing a career in research, or to your younger self starting in science?

Science has fundamentally transformed the world. It pervades all areas of our daily lives, most obviously in the wide variety of technological innovations that it inspired: from cars to airplanes to spaceships, from the telegraph to the telephone to cell phones. Computer chips are now ubiquitous. Not only are they the heart of laptops, they are essential for every form of transportation, they are in our household appliances and they are even embedded in our bodies to monitor biological functions.

These transformative technologies are all ultimately based on science, involving countless scientists who have taken it upon themselves to explore not only the fundamental principles underlying the workings of the technological miracles that we now basically take for granted, but it also makes us aware of our place in the universe.

From that perspective it actually does not make much of a difference if one is interested in exploring the origin of the universe, the origin of life, the electronic properties or a specific material or for that matter the social structure of baboons. These very different scientific topics are all above all driven by pure curiosity.

We are now so lucky to live in a time where society honors these efforts by creating and maintaining universities that pursue science with no political, religious or geographic boundaries; that embrace that science is an international cooperative effort.

So, my advice to young scientists is to follow your dream to learn about the world along whatever path you wish, realizing that, no matter how specialize your field of choice is, you will contribute to the enormous tapestry of science. But remember that while science is driven by your curiosity it survives by virtue of your integrity and humility.

What inspired you to be in the profession you are today?

From an early age I have always had a very strong interest in physics and physics related subjects. Not sure why that is.

What impact does your research or project have on society?

If this is successful, it can introduce a new generation of electronics that uses less power and is faster.

What is one surprising fact about your research or project that people might not know?

People may not realize that there are alternative ways to do electronics which may be quite different from what we have now. 

What’s the most exciting moment you've experienced over the course of your research or project?

We discovered that the graphene edges are extremely good conductors, exceeding that what is possible according to current theory. It is still not known why this is so.