Using lattice distortions to improve carrier mobility in 2D semiconductors

Using lattice distortions to improve carrier mobility in 2D semiconductors

The researchers’ method: introducing ripples into 2D material, molybdenum disulfide, to achieve two orders of magnitude improvement in the mobility of carriers at room temperature, allowing electrons to move faster through the material. Credit: Dr. Wu Jing, A*STAR, Institute of Materials Research and Engineering.

Two-dimensional (2D) semiconductors are semiconducting materials with atomic-scale thicknesses, which have exceptional electronic properties. In the future, these materials could have the potential to replace silicon in the development of numerous electronic and optoelectronic devices.

Despite their advantages, the use of 2D semiconductors has been limited to date, in part due to their low carrier mobility at room temperature† This is caused by strong scattering of phonons (ie quasiparticles associated with collective atomic vibrations) in the lattices of the materials.

Researchers from the Agency for Science, Technology and Research (A*STAR) in Singapore and the Hong Kong Polytechnic University in Hong Kong, China, recently developed a design strategy that could help overcome this limitation and enhance the mobility of 2D materials. for wearers. Their proposed approach, outlined in a paper published in Nature Electronicsinvolves the introduction of lattice deformations into a 2D material, using bulging substrates.

“Our paper is inspired by the high carrier mobility observed in 2D TMDs on substrates with a high surface roughness by Tao Liu et al. back in 2019,” Dr. Ming Yang and Dr. Jing Wu. Two of the researchers who conducted the study told TechXplore. “However, the observed mobility improvement was simply attributed to stress effects and the fundamental mechanism remains unclear. To that end, we dug deeper to unravel the underlying physics responsible for such a significant improvement in mobility and to demonstrate lattice engineering as an effective strategy to create high-performance electronic devices at room temperature.”

Most conventional strategies for improving carrier mobility of 2D semiconductors rely on achieving ideal lattice structures. In contrast, the strategy proposed by Yang, Wu and their colleagues only involves the introduction of bulging substrates, which create wrinkles in a 2D semiconductor and suppress the scattering of phonons.

“We simply placed 2D materials on substrates with bulging morphologies, creating ripples in the material that lead to lattice distortion,” explained Yang and Wu. “Normally, lattice distortions are planned to adversely affect carrier mobility. However, we show that such lattice distortions create greater electrical polarization, which can renormalize not only the frequency of phonons to effectively suppress scattering between electrons and phonons, but also the intrinsic dielectric constant to further screen the polar phonon scattering.”

Compared to other existing approaches for increasing carrier mobility in 2D semiconductors, the strategy proposed by these researchers is both simple and cost-effective. As part of their study, the team tested it on 2D molybdenum disulfide (Moss2) and found that this resulted in a carrier mobility at room temperature of about 900 cm2V−1s−1showing the predicted phonon-restricted mobility of flat MoS. exceeds2 (varying between 200 and 410 cm2V−1s−1

“The observed mobility enhancement and the underlying mechanism of such high carrier mobility in rippled-MoS2representing the predicted phonon-restricted mobility in flat-MoS. exceeds2is particularly remarkable,” Yang and Wu said. “So high carrier mobility can pave the way for low power electronics and is an important parameter for most applications ranging from field effect transistors to photo detectors and more.”

The study conducted by this team of researchers highlights the enormous potential of lattice engineering strategies to improve the performance of electronics and thermoelectric devices at room temperature. In the future, their method could be used to create more efficient devices based on 2D semiconductors. In addition, it could potentially inspire the development of other design strategies based on: schedule engineering.

“In our next studies, we plan to systematically create corrugated/bulging substrates to minimize variability, and to study the correlations between bulges,” Yang and Wu added.

A strategy to modulate the doping of 2D transistors remotely

More information:
Hong Kuan Ng et al, Improving the mobility of carriers in two-dimensional semiconductors with corrugated materials, Nature Electronics (2022). DOI: 10.1038/s41928-022-00777-z

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