Towards more energy-efficient 2D semiconductor devices

According to researchers from the Singapore University of Technology and Design (SUTD), a precocious discovered household of two-dimensional (2D) semiconductors could pave the mode for high-performance and energy-efficient electronics. Their findings, published successful npj 2D Materials and Applications, whitethorn pb to the fabrication of semiconductor devices applicable successful mainstream electronics and optoelectronics—and adjacent perchance regenerate silicon-based instrumentality exertion altogether.

In the quest of miniaturizing physics devices, 1 well-known inclination is Moore's law, which describes however the fig of components successful the integrated circuits of computers doubles each 2 years. This inclination is imaginable acknowledgment to the ever-decreasing size of transistors, immoderate of which are truthful tiny that millions of them tin beryllium crammed onto a spot the size of a fingernail. But arsenic this inclination continues, engineers are starting to grapple with the inherent worldly limitations of silicon-based instrumentality technology.

"Due to the quantum tunneling effect, shrinking a silicon-based transistor excessively tiny volition pb to highly uncontrollable instrumentality behaviors," said SUTD Assistant Professor Ang Yee Sin, who led the study. "People are present looking for caller materials beyond the 'silicon era', and 2D semiconductors are a promising candidate."

2D semiconductors are materials that are lone a fewer atoms thick. Because of their nanoscale size, specified materials are beardown contenders arsenic replacements for silicon successful the quest of processing compact electronic devices. However, galore presently disposable 2D semiconductors are plagued by precocious electrical absorption erstwhile they travel into interaction with metals.

"When you signifier a interaction betwixt metal and semiconductor, often determination volition beryllium what we telephone a Schottky barrier," explained Ang. "In bid to unit energy done this barrier, you request to use a beardown voltage, which wastes energy and generates discarded heat."

This piqued the team's involvement successful Ohmic contacts, oregon metal-semiconductor contacts with nary Schottky barrier. In their study, Ang and collaborators from Nanjing University, the National University of Singapore and Zhejiang University showed that a precocious discovered household of 2D semiconductors, namely MoSi₂N₄ and WSi₂N₄, signifier Ohmic contacts with the metals titanium, scandium and nickel, which are wide utilized successful the semiconductor instrumentality industry.

Furthermore, the researchers besides showed that the caller materials are escaped from Fermi level pinning (FLP), a occupation that severely limits the exertion imaginable of different 2D semiconductors.

"FLP is an adverse effect that happens successful galore metal-semiconductor contacts, and is caused by defects and analyzable materials interactions astatine the interaction interface," Ang said. "Such an effect 'pins' the electrical properties of the interaction to a constrictive scope careless of the metallic utilized successful the contact."

Because of FLP, engineers are incapable to tune oregon set the Schottky obstruction betwixt the metallic and semiconductor—diminishing the plan flexibility of a semiconductor device.

To minimize FLP, engineers usually employment strategies similar precise mildly and dilatory positioning the metallic connected apical of the 2D semiconductor, creating a buffer furniture betwixt the metallic and semiconductor oregon utilizing a 2D metallic arsenic a interaction worldly with the 2D semiconductor. While these methods are feasible, they are not yet applicable and are incompatible with wide fabrication utilizing mainstream manufacture techniques disposable today.

Amazingly, Ang's squad showed that MoSi₂N₄ and WSi₂N₄ are people protected from FLP owed to an inert Si-N outer furniture that shields the underlying semiconducting furniture from defects and worldly interactions astatine the interaction interface.

Because of this protection, the Schottky obstruction is 'unpinned' and tin beryllium tuned to lucifer a wide array of exertion requirements. This betterment successful show helps enactment 2D semiconductors successful the moving arsenic replacements for silicon-based technology, with large players similar TSMC and Samsung already expressing involvement successful 2D semiconductor electronics.

Ang hopes that their enactment volition promote different researchers to probe much members of the recently discovered 2D semiconductor household for absorbing properties, adjacent those with applications beyond electronics.

"Some of them mightiness beryllium precise mediocre successful presumption of electronics applications but precise bully for spintronics, photocatalysts oregon arsenic a gathering artifact for star cells," helium concluded. "Our adjacent situation is to systematically scan done each of these 2D materials and categorize them according to their imaginable applications."

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More information: Qianqian Wang et al, Efficient Ohmic contacts and built-in atomic sublayer extortion successful MoSi2N4 and WSi2N4 monolayers, npj 2D Materials and Applications (2021). DOI: 10.1038/s41699-021-00251-y