Beyond Silicon: The Potential Of Graphene In Semiconductors

By John Oncea, Editor

The first working semiconductor made of graphene outperformed one made of silicon leading to speculation that graphene could be the future of computing. But will graphene replace silicon, despite challenges such as the lack of a natural bandgap, scalability, integration with existing technologies, and long-term reliability?

Let’s start at the very beginning. *

Graphene is a single-layer structure made up of carbon atoms arranged in a hexagonal pattern. It serves as the fundamental component of graphite, which is utilized in pencil tips, among other things. However, graphene is an extraordinary substance in its own right, possessing a variety of incredible characteristics that frequently earn it the moniker “wonder material.”

“Among graphene’s remarkable properties are unique mechanical, thermal, electrical, and optical behaviors,” writes Graphene-info. “Note that most of these features relate to perfect, pristine graphene sheets. Defects in graphene (some of which stem from the production processes or connection points of several smaller graphene flakes stitched together, for example) can make graphene weaker and with quite different properties. Defects, however, can bring about new and different properties that make graphene more suitable for certain applications!”

Graphene is the total package: it’s harder than either steel or diamond of the same dimension, lightweight (it weighs just 0.77 milligrams per square meter), flexible (it can be stretched up to 20% of its initial size without breaking), and highly impermeable (even helium atoms can’t go through it).

“Graphene has an extremely high electrical current density (a million times that of copper) and intrinsic mobility (100 times that of silicon),” Graphene-info reports. “Graphene has a lower resistivity than any other known material at room temperature, including silver.”

Graphene is the perfect thermal conductor, featuring record thermal conductivity higher than that of carbon nanotubes, graphite, and diamond (over 5,000 W/m/K). It is also an isotropic conductor, able to conduct heat in all directions.

Graphene possesses unique characteristics that have the potential to revolutionize the electronics industry. By incorporating this material, smaller, lighter, tougher, and more efficient devices could be produced. Moreover, if graphene is applied to electronic circuits, it could make devices impervious to dampness, one of the primary reasons for damage and deterioration. There is even a school of thought that, one day, graphene could replace silicon in the production of semiconductors. **

* A very good place to start.

** This is called “foreshadowing.”

The Future Is Here

Word came out in early January that researchers at Georgia Tech Institute of Technology (go, Yellow Jackets!) created the first working graphene semiconductor, a success that could allow for smaller and faster electronic devices and may have applications for quantum computing.

“Their discovery comes at a time when silicon, the material from which nearly all modern electronics are made, is reaching its limit in the face of increasingly faster computing and smaller electronic devices,” writes Georgia Tech. “Walter de Heer, Regents’ Professor of physics at Georgia Tech, led a team of researchers based in Atlanta and Tianjin, China, to produce a graphene semiconductor that is compatible with conventional microelectronics processing methods — a necessity for any viable alternative to silicon.”

de Heer and his team managed to overcome a major obstacle that has been hindering graphene research for years – band gap, a critical electronic property required for semiconductors to switch on and off. Graphene was unable to perform this function until now thanks to de Heer's team.

"We now have an extremely robust graphene semiconductor with 10 times the mobility of silicon, and which also has unique properties not available in silicon," de Heer said.

How The Sausage … Err, Graphene … Is Made

Graphene is a semimetal that is not naturally a semiconductor or a metal. For transistors and other silicon electronics to work, a material with a band gap is needed. The band gap can be turned on and off by applying an electric field. The main challenge in research on graphene electronics was figuring out how to switch it on and off like silicon so that it could function as a semiconductor.

To create a functional transistor, a semiconducting material must be manipulated extensively, which can potentially harm its properties. To demonstrate that their platform could be used as a viable semiconductor, the research team needed to measure its electronic properties without causing any damage. To achieve this, they used a technique called doping, where they added atoms to the graphene that "donate" electrons to the system. This allowed them to determine if the material was a good conductor without harming its properties, and the technique succeeded in achieving this goal.

“The team’s measurements showed that their graphene semiconductor has 10 times greater mobility than silicon,” Georgia Tech writes. “In other words, the electrons move with very low resistance, which, in electronics, translates to faster computing. “It's like driving on a gravel road versus driving on a freeway,’ de Heer said. ‘It's more efficient, it doesn't heat up as much, and it allows for higher speeds so that the electrons can move faster.’”

The team has developed a two-dimensional semiconductor that possesses all the necessary properties to be used in nanoelectronics. Its electrical properties are far superior to any other 2D semiconductors currently in development.

On The Other Hand

With the bandgap issue possibly resolved, there still are challenges that need to be addressed before graphene can fully replace traditional semiconductor materials like silicon. Some of these challenges include:

• Mass Production: Scalable and cost-effective methods for mass-producing high-quality graphene are still under development. The production process needs to be optimized to meet the demands of the semiconductor industry.
• Integration with Existing Technology: Graphene-based semiconductors need to be seamlessly integrated into existing semiconductor manufacturing processes. Compatibility with current technologies is crucial for practical adoption.
• Reliability and Stability: Ensuring the long-term reliability and stability of graphene-based semiconductors under various conditions is a key concern. Understanding the material's behavior over time is essential for practical applications.

While graphene holds great promise, it is not yet clear if it will completely replace silicon. It is more likely that graphene will find specific niche applications or be used in combination with other materials to enhance overall performance, though ongoing research and development will determine the extent of graphene’s role in the future of semiconductors.