ISABEL RUBIO ARROYO | Tungsteno
From mobile phones, computers and processors to electric cars and photovoltaic panels, almost all modern electronic devices use silicon chips. But in recent years, the limited capacity of this chemical element has led scientists around the world to study other materials; for example, gallium arsenide, graphene or carbon nanotubes. Among all the candidates for replacing silicon, one of the most promising is gallium nitride (GaN). This material is already here, in the form of products for sale, and may be a good alternative in the short term.
Moore's law states that the number of transistors that fit inside a chip doubles about every two years on average. Silicon is not a perfect conductor, so it is increasingly difficult to make smaller, yet more powerful, processors. With the expected slowdown in Moore's Law, technology companies, governments and universities are looking for alternatives to the current methods of microchip manufacturing.
Unlike crystalline silicon, which has been used in microchips and solar panels for half a century, gallium nitride is a man-made material that does not exist in nature. "But the atoms it is made of do," explains Colin Humphreys, a researcher at the Centre for Gallium Nitride at Cambridge University. GaN is composed of gallium and nitrogen atoms. Gallium is extracted from the ground, while nitrogen "is in the atmosphere we breathe."
Thanks to its properties, a massive use of GaN in lighting could save the world 25% of the electricity used.. Credit: Cambridge Center for Gallium Nitride. Credit: Cambridge Centre for Gallium Nitride.
Efficiency and Resilience
GaN stands out because it can become much more efficient than silicon and use less energy. This allows, for example, charging devices to be much smaller than conventional ones. Proof of this is a power adapter manufactured in 2019 by the company Anker. It is a small cube with a USB-C port that weighs barely 60 grams and can easily power a computer.
In addition, gallium nitride can be used to emit bright light in the form of light-emitting diodes (LEDs) and laser diodes. It also beats silicon when operating at high temperatures. This capability opens up new possibilities for designing the devices of the future. This is the case with electric vehicles, which today often have their electronics far from the engine to prevent them from getting too hot.
Such is the importance of gallium nitride that more and more research teams are studying the potential of this material. In fact, the University of Cambridge and the Massachusetts Institute of Technology have set up specific research groups to explore its electronic applications. Both groups aim to measure the physical properties of GaN. The MIT research team is specifically looking at which gallium nitride devices are compatible with the technologies that today use silicon devices. Even the U.S. Department of Energy has promoted projects to analyse its properties.
The key to the future of transistors
For Humphreys, GaN "is possibly the most relevant new material since silicon." He has no doubt that it will be a key element for the next generation of transistors: "Gallium nitride can make electronic devices work at higher power, higher frequency and higher temperature than silicon, and using less energy." 5G communications, he notes, will in many cases use GaN electronics instead of silicon. "5G works at higher frequencies than 4G. Gallium nitride chips are more powerful and can operate at these frequencies, but silicon chips cannot," explains the researcher.
In addition to being useful for this type of equipment, its properties for lighting are also relevant. "It is an important material because mixed with another element, Indian, it emits a bright light when a small electric current passes through it," he says. Gallium nitride light-emitting diodes, he says, have a very promising future because "they are very efficient and have begun to dominate the world’s lighting."
This efficiency manifests itself in considerable savings. In fact, according to the researcher, a massive use of GaN in lighting "would lead to a 15% savings of the electricity used worldwide." If we also take into account the electronic devices that would work with this material, the figures would be even more considerable. In total, Humphreys argues that the use of GaN "could save the world 25% of the electricity used."
GaN will be a key element for the next generation of transistors, as it makes electronic devices operate at a higher power, frequency and temperature than silicon. Credit :Bryce Vickmark / MIT.
Barriers to implementation
Why for the moment isn’t silicon being replaced by GaN? Despite the advantages of this material, it is not yet being extensively used. The main disadvantage of GaN devices is that they are more expensive than silicon ones. In addition, silicon is a very mature material and firmly established in society. In order for gallium nitride to be successful in the future, its reliability must be proven beforehand through extensive research.
It is still too early to determine the true impact that gallium nitride will have on society. In fact, different research is underway on possible substitutes for silicon. For example, a team of scientists has developed a 16-bit processor with some 14,000 carbon nanotube transistors (CNTs), according to research published in 2019 in the journal Nature. Meanwhile, a CSIC research group is working on optical or photonic semiconductor processing.
But Humphreys has no doubt that gallium nitride will eventually supersede many other materials. The researcher explains that this material is not yet used in computers and mobiles, although "the light from the flash of a smartphone camera is a GaN LED." However, this element is already beginning to replace silicon in 4G mobile phone base stations, which are used to amplify the signals of our smartphones. GaN amplifiers "are more powerful than silicon amplifiers, allowing base stations to be separated even further from each other."
Gallium nitride can also enable everything from inventing electric cars with longer range to making smaller, more powerful processors without the limitations of silicon. "Silicon devices will be with us for a long time, but GaN devices will gradually replace them," Humphreys concludes.
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Tungsteno is a journalism laboratory to scan the essence of innovation. Devised by Materia Publicaciones Científicas for Sacyr’s blog.