Tunable conductivity – the deciding feature of semiconductor materials – is the materials science discovery that enabled the modern digital age. Now, scientists are seeking alternatives to the mainstay of the semiconductor industry. Recent research has highlighted cubic boron arsenide as a semiconductor material to remember.
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Modernity is Built on Semiconductors
Semiconductor materials possess unique – and tunable – energy conductivity properties; as small band gap insulators, they can amplify an electron’s signal, for example, or only allow them to flow in one direction. These materials can be altered or tuned in a process known as doping. Their electric properties are changed, and as a result, the wide use of semiconductors in the electronics industry is guaranteed.
Semiconductors like silicon switch electric signals on and off in computer chips, acting as transistors. These solid-state switches are the basis of computer hardware and arguably power the world as we know it today. There are semiconductor transistors in any electronic device with memory, smart functionality, or any kind of connectivity.
As well as transistors, semiconductor materials (mostly silicon) can form diodes like LEDs. Diodes are electronic components whose electrons can only flow in one direction, and the semiconductor part of them is responsible for controlling this flow of electrons LEDs are used in nearly all electronic devices with a display or read-out feature.
Silicon Dominates Semiconductor Manufacturing
Silicon is used for the vast majority of semiconductor applications today. It is durable, has the right electrical properties, and is relatively simple to purify. It also exists in abundance on Earth, making up almost three-tenths of its crust. However, its inability to process light makes it incompatible with cutting edge of electrical and computer engineering.
Silicon does not convert light into electrical signals (or reverse the signal from electricity to light) efficiently. This means that semiconductor applications in solar panels, camera sensors, and other optical settings, including optical computing, are unsuitable for silicon.
Scientists Synthesize New Semiconductor: Cubic Boron Arsenide
Cubic boron arsenide was first synthesized just a few years ago by scientists working with Zhifeng Ren at University of Houston Texas. In 2015, Ren and his colleagues grew crystals of the material from boron and arsenic, later discovering its promising semiconductor properties in 2018.
Boron arsenide (or BAs) has a lattice constant of 0.4777 nm and its indirect band gap is 1.82 eV. It melts at 2076 C, has an optical refractive index of 3.29 at 657 nm wavelength, and elastic modulus is 326 GPa.
In 2022, two of science magazine Physics World’s “Top 10 Breakthroughs'' of the year were allotted to experiments demonstrating the material’s superconductive potential, largely due to its ability to conduct both electrons and “electron-holes” extremely well. Most other semiconductors only allow one type of electron particle to travel through it well, and the material’s overall efficiency is determined by the less conductive of the two.
Cubic boron arsenide is also highly thermally conductive, theoretically reaching 2,200 W/(m-K). It was only around 190 W/(m-K) when it was first synthesized due to defects in the material; scientists improved the process to remove defects, and have now created cubic boron arsenide with thermal conductivity of 1000 W/(m-K). This makes it comparable to extremely thermally conductive materials like diamond and graphite, and much more thermally conductive than other semiconductor materials.
“The potential of this material is tremendous,” said Ren. “While work to consistently produce larger crystals with uniform properties is ongoing, the result could have an even bigger impact on the field than the silicon wafer.”
Applications for Cubic Boron Arsenide
Due to its high electronic and thermal conductivity, boron arsenide is under investigation for application in electronics thermal management. Thermal management is important in most modern electronic systems. Heat energy must be dissipated throughout electronics like computers and cars, leading some to turn to novel semiconductors for answers.
Cubic boron arsenide as well as boron phosphide, could replace silicon in chips and work as cooling as well as electronically conductive substrates.
Overheating is a key cause of failure in electronics, and wastes energy that could be more efficiently used for the purposes of the machine, be that computing or lighting buildings. Electronic substrates that actively cool components would lead to increased efficiency and less demand for energy.
It is important to look ahead to the next stages of electronic and digital technology and ensure that any future progress is not achieved at the expense of the planet’s limited resources. Advanced materials can contribute to this goal by making all kinds of components and devices more efficient.
The ubiquity of electrical products means that even small efficiency gains achieved with new materials can greatly impact the world’s total energy demands, heat pollution, and electronic waste. If cubic boron arsenide can compete with silicon on the market, the impact could be massive.
References and Further Reading
Khan, R. (2022). Physics World Cites UH Research Among Top 10 Breakthroughs of 2022. [Online] University of Houston. Available at: https://uh.edu/news-events/stories/2022-news-articles/december-2022/article.php
Li, S. et al (2018). High thermal conductivity in cubic boron arsenide crystals. Science. doi.org/10.1126/science.aat8982.
Li, S., et al (2022). Anomalous thermal transport under high pressure in boron arsenide. Nature. doi.org/10.1038/s41586-022-05381-x.
Remmel, A. (2022). This semiconductor breaks the rules of physics under pressure. [Online] Chemical and Engineering News. Available at: https://cen.acs.org/materials/semiconductor-breaks-rules-physics-under/100/web/2022/12
Tian, F., et al (2018). Unusual high thermal conductivity in boron arsenide bulk crystals. Science. doi.org/10.1126/science.aat7932.
Vandervelde, T. (2016). Beyond silicon: the search for new semiconductors. [Online] The Conversation. Available at: https://theconversation.com/beyond-silicon-the-search-for-new-semiconductors-55795
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