Georgia Tech group create world’s first graphene-based semiconductor

A group of researchers at the Georgia Institute of Technology (Georgia Tech) have created the world’s first functional semiconductor made from graphene, a development that could lead to advanced electronic devices and quantum computing applications.

Seen as the building block of electronic devices, semiconductors are essential for communications, computing, healthcare, military systems, transportation and countless other applications.

Semiconductors are typically made from silicon, a material that revolutionised the electronics industry and ushered in the digital age. Purified silicon is used in devices such as computer chips, transistors, integrated circuits and liquid crystal displays.

Its highly stable atomic structure means it has the conductive properties of metal as well as being an insulator, so silicon can both conduct and block electricity. This characteristic allows semiconductors to switch on and off.

Despite its advantages, silicon is reaching its limit in the face of increasingly faster computing and smaller electronic devices, according to the Georgia Tech research team who published their findings in Nature earlier this year.

In a drive to find a viable alternative to silicon, Walter de Heer, Regents’ Professor of physics at Georgia Tech, led a team of researchers based in Atlanta, Georgia and Tianjin, China to produce a graphene semiconductor that is compatible with microelectronics processing methods.

The graphene material inside a bottle. ©Chris McKenney

The group sought to solve a decades-long roadblock in graphene research known as the ‘band gap’ – a crucial electronic property that enables transistors and silicon electronic devices to be turned on and off when an electric field is applied.

“We were motivated by the hope of introducing three special properties of graphene into electronics,” said de Weer. “It’s an extremely robust material, one that can handle very large currents, and can do so without heating up and falling apart.”

Because graphene is neither a semiconductor nor a metal, but a semimetal, the team had to find a way to switch it on and off so it can work like silicon.

To do this, the researchers placed atoms on the graphene that donate electronics to the system – a technique called doping, which helps to measure the material’s conductivity.

The team found that the graphene semiconductor had ten times higher mobility than silicon, meaning electrons move with minimal resistance, leading to faster computing in electronics.

“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 claims that its product is currently the only two-dimensional semiconductor that has all the necessary properties to be used in nanoelectronics.

“A long-standing problem in graphene electronics is that graphene didn’t have the right band gap and couldn’t switch on and off at the correct ratio,” said Lei Ma, co-author of the group’s latest paper.

“Over the years, many have tried to address this with a variety of methods. Our technology achieves the band gap, and is a crucial step in realising graphene-based electronics.”

The material could usher in the next generation of electronics and allow for the quantum mechanical wave properties of electrons to be utilised, a requirement for quantum computing.

A study published in Nature Nanotechnology in 2013 titled ‘Graphene Quantum Dots at Room Temperature’ outlined how graphene can be used to create quantum dots, which are nanoscale semiconductor particles that can confine electrons.

Bilayer graphene, formed by stacking two graphene sheets, offers a platform with adjustable band gaps using an electric field perpendicular to the layers.

This feature is useful for crafting quantum dots, tiny containers for electronics which are crucial for potential use in quantum computing due to their versatile characteristics.

Global graphene boom

A recently published analysis into the global graphene market revealed that it has been continuously growing over the last years to reach an average estimated global annual revenue of $380m in 2022.

More than 85% of the market reports forecast growth rates of more than 20%, with 70% of the reports expecting a CAGR of more than 30% in the near- to medium-term future.

According to the study, the global graphene demand could increase to a range of 9,000 and 170,000 tonnes per year in 2028, with a median of 30,000 tonnes.

The graphene electronics market in particular could see revenue values reach from below $100m to more than $1bn and growth rates to increase from below 20 to almost 40%.

Henning Döscher, researcher at Fraunhofer ISI and one of the four authors of the publication, said, “Emerging niche players largely dominate graphene production so far. They also venture in promising application fields, where the market leaders usually still ignore opportunities arising from graphene.”

“However, some already [began] to build up significant graphene applications such as Samsung in the electronics sector.”