For decades, silicon was the go-to material for tech applications. It's a useful semiconductor, easy to work with, and one of the most abundant materials on earth. Despite that, there's a new material that might just end up supplanting silicon as tech's go-to semiconducting material—gallium nitride (GaN).
Gallium nitride is a semiconducting compound made up of gallium and nitrogen. It's most notable for having a wider band gap than silicon—giving it a larger range of energy states that are impossible for an electron to take. While silicon has a band gap of 1.2eV, gallium nitride comes in at 3.4eV. This makes GaN a “wide bandgap semiconductor,” which means it can handle higher voltages than silicon.
GaN is also a superior semiconductor compared to silicon in high temperature applications. With its smaller band gap, silicon-based semiconductors are more easily activated by thermal energy, restricting their use to environments under 100°C (212°F). By contrast, GaN's wider band gap requires more thermal energy to experience interference, allowing it to be used in high-temperature applications—up to 300°C (572°F). In optical applications, its wide band gap allows it to produce violet laser light.
While silicon has allowed the tech industry to do some incredible things, science is reaching the limit of what it can make it do. Gallium nitride, however, looks like it can easily step in and take technology even farther.
Since GaN can carry higher voltages than silicon, and do it more quickly, it's more efficient. GaN-based electronics also waste less energy, which means they require less power to operate in the first place. Their efficiency means that they can be used in applications that need to be very small, or packed into larger devices to improve performance and lower power consumption.
There's only one area where silicon has gallium nitride beat: cost. Silica, the basis of silicon, is one of the most abundant materials on earth. It's cheap, easy to source, and (most of all) tech companies already have the knowledge, equipment, and supply chains to work with it. Gallium nitride is more expensive, less abundant, and can't be worked the same as silicon. Both large companies and startups alike are working on making GaN more competitive, by researching ways to grow crystals of it on silicon so existing technology can be retrofitted to work with GaN.
Since it can be used in higher-voltage and higher-temperature applications versus silicon, gallium nitride is, unsurprisingly, employed where things tend to get hot. A new bonding method created by Engineers at the Georgia Institute of Technology allows for the attachment of wide band gap materials to thermal conductors, to allow for the rapid dissipation of heat.
The process works like this: An ion source in a vacuum is used to clean and prepare a wide band gap material, like gallium nitride, and a thermal conductor, like diamond. During this process, both surfaces develop dangling bonds. By introducing very small amounts of silicon, engineers can cause the materials to bond directly to each other to create a high electron mobility transistor (HEMT). Since the interface layer between the wide band gap material and the thermal conductor is so thin (as little as 4 nanometers), heat dissipates very rapidly, keeping the HEMT cool.
This process is superior to previous means of bonding these materials. Previously, engineers grew diamond films directly on the gallium nitride, resulting in a layer of diamond with low thermal conductivity. Doing this required subjecting the materials to high temperatures, which could also cause stress cracks in the finished product. The new method is both better at keeping cool, and results in a better, more reliable transistor.
While the tech industry is currently very reliant on inexpensive, abundant silicon, it's reaching the end of what silicon can do. While gallium nitride is currently more expensive to source and work with, its electrical, thermal, and optical properties make it a very attractive choice for companies looking to create higher-efficiency electronics for use in a wider range of environments.
