Two new methods push graphene’s electronic quality beyond traditional semiconductors

Graphene, a single sheet of carbon atoms arranged in a honeycomb lattice, is known for its exceptional strength, flexibility and conductivity. However, despite holding the world record for room-temperature electron mobility, graphene’s performance at cryogenic temperatures has remained below that of the best gallium arsenide (GaAs)-based semiconductor systems, which have benefited from many decades of refinement.

One key obstacle is electronic disorder. In practical devices, graphene is highly sensitive to stray electric fields from charged defects in surrounding materials. These imperfections create spatial fluctuations in charge density, known as electron-hole puddles, that scatter electrons and limit mobility. This disorder has prevented graphene from realizing its full potential as an ultra-clean electronic system.

Now, in two parallel studies, researchers from the National University of Singapore (NUS) and The University of Manchester (UK) report distinct strategies that finally push graphene past this long-standing benchmark. The results set new records for electron mobility, matching and in some cases surpassing GaAs in both transport and quantum mobility, and enabling the observation of quantum effects in unprecedented conditions.

“Mobility is a measure of how easily electrons can move through a material when an electric field is applied. High mobility means electrons can travel faster and more freely, which is crucial for building faster and more energy-efficient electronic devices,” said Assistant Professor Alexey Berdyugin from the Department of Materials Science and Engineering, College of Design and Engineering (CDE), NUS. “Materials with high mobility are especially important for advanced computing, sensing and quantum technologies.” Asst Prof Berdyugin is also a scientist in the Department of Physics at the NUS Faculty of Science.

“This opens up opportunities not just for fundamental research, but also for high-performance applications where ultra-clean materials are critical,” he added.

Twisted graphene and tunable Coulomb screening

In the first study, published in Nature Communications on 11 August 2025 and led by Asst Prof Berdyugin together with collaborators from the United Kingdom, Spain and Japan, the researchers developed a method to shield graphene from environmental disorder by using additional graphene layers as ultra-thin electrostatic screens. They achieved this by stacking two graphene layers with a large relative twist angle (between 10° and 30°), thereby ensuring the layers were electronically decoupled while separated by less than a nanometer.

One layer could then be deliberately doped to act as a metallic screen, suppressing the fluctuating electric fields from charged impurities that otherwise disrupt electron motion.

As a result, charge inhomogeneity was reduced to just a few electrons per square micrometer—an order of magnitude better than state-of-the-art devices. The high quality of the graphene layer enabled the onset of Landau quantization, which is a hallmark of quantum behavior in two-dimensional materials, to be observed at magnetic fields of just 5–6 milli-Tesla. In most graphene devices, several hundred times stronger fields are required.

Because the technique minimizes scattering from long-range electric field fluctuations, the transport mobility exceeded 20 million cm²/Vs, and quantum mobility surpassed that of the best GaAs two-dimensional electron gases.

“Graphene has finally caught up and even exceeded traditional semiconductors in some critical aspects,” added Ian Babich, a Ph.D. student in CDE and the Institute for Functional Intelligent Materials at NUS and first author of the study. “It’s a historical moment for graphene devices, and it enables further exploration of delicate quantum phenomena that were previously out of reach.”

Proximity metallic screening for record mobilities

The second study, published in Nature on 20 August 2025 and led by Nobel Laureate Sir Andre Geim and Dr. Daniil Domaretskiy at The University of Manchester, with Asst Prof Berdyugin as co-corresponding author, took a different approach. Instead of using another graphene layer, the team placed graphene less than one nanometer away from a metallic graphite gate, separated by an ultrathin dielectric made of just three to four atomic layers of hexagonal boron nitride.

This ultra-close proximity created exceptionally strong Coulomb screening, dramatically reducing disorder and bringing charge inhomogeneity down to around 3×10⁷ cm⁻², equivalent to roughly one extra charge carrier per 100 million carbon atoms at the charge neutrality point.

With this level of purity, the devices reached Hall mobilities exceeding 60 million cm²/Vs, surpassing the most advanced GaAs-based systems. Quantum Hall plateaus, which normally require magnetic fields of several Tesla, appeared below 5 milli-Tesla. Shubnikov–de Haas oscillations, another quantum signature, were visible at just 1 milli-Tesla, comparable in strength to the pristine magnetic field of Earth.

Complementary routes to ultra-clean graphene

The two studies provide complementary solutions to the same longstanding problem: how to protect graphene from the charged defects which are always present in its surrounding materials, which limit its electronic performance.

“Of course, each approach has its strengths,” said Asst Prof Berdyugin. “Large twist angle graphene devices provide highly tunable and controllable screening.

“On the other hand, proximity screening with graphite separated by a thin dielectric spacer allows us to probe the properties of a pristine graphene layer directly. This way, there is no additional signal from the screening layer, and one can observe absolutely beautiful Quantum Hall plateaus already at a few milli Tesla. Together, those methods expand our experimental toolkit in a way that will benefit the field of two-dimensional materials.”

The researchers’ breakthroughs could accelerate progress in areas ranging from quantum metrology, where the quantum Hall effect underpins international resistance standards, to ultra-sensitive sensing technologies that depend on pristine electronic behavior.

The exceptional mobilities achieved could also advance next-generation high-speed electronics, where low disorder is critical for performance and energy efficiency. In addition, the methods provide cleaner experimental platforms for exploring correlated electron states relevant to emerging quantum information technologies.

Looking ahead, the teams aim to adapt these methods to more complex graphene-based heterostructures, including moiré quantum materials that host intriguing many-body effects.

“These results change what we thought was possible for graphene,” said Babich. “The performance we can now achieve means there is a whole new space of physics to explore.”