»It's a real breakthrough for semiconductor technology«

How do you explain to others in simple terms what the patent is about?

Recently I saw the film Dumbo with my little daughter. It is about a small elephant with big ears who learns to fly. And then I proudly told her that I also made a Dumbo fly. Because that's exactly the difficulty of growing AlScN by MOCVD: the scandium molecule is quite large and heavy – just like Dumbo – so you need the right material and a smart way to bring it into the gas phase. Nevertheless, my team and I managed to make the Scandium Dumbo fly.

How do you rate the significance of your patent?

Our patent is groundbreaking for many different industries, as it covers not only AlScN, but also the epitaxial growth of any material using MOCVD. There are many chemical elements that now can be brought into the gas phase with our process, opening up new technological possibilities. Yttrium, for example, is very interesting for highly efficient green LEDs. And scandium can be used to manufacture more efficient UV LEDs, which are important for water disinfection. So the optoelectronics industry will also benefit from our research.

Is that the »Way Ahead« to you?

Absolutely! There are superconductors like niobium nitride that could play an important role in quantum computing because they can enable a “solid-state miniaturization” of quantum computers. Niobium nitride is currently grown using molecular beam epitaxy, but this process is not suitable for industrial production. With the process described in our patent, we could produce it for industrial use.

And if we think even further into the future, there are research groups that use artificial intelligence to theoretically generate all possible material compounds of nature, in particular relating to nitrides, and they make predictions about the properties of these materials. If you find a particular compound that theoretically has a superconducting temperature characteristic already at the temperature of liquid nitrogen, then we could produce it using MOCVD. So the possibilities for the future are enormous.

How did the patent come about?

We already had the dream to grow AlScN using MOCVD when we first sat together in the team. We thought: If we could do that, we would be the first in the world, we would significantly advance IAF’s technology and we could proudly tell our friends and family that our contribution will make energy conversion much more efficient. From this dream grew the motivation to actually do it.

Last year we sent our first samples out overseas for measurements. The results were expected shortly after Christmas. The night before I could hardly sleep. I was so excited that I had to check my e-mails over and over again. And when the results finally arrived at 4 a.m., they showed that scandium was present in the layers. Only a small amount, but still. That was the moment that I knew we could do it.

What does it mean to you and your team to have achieved the previously impossible?

It is a real breakthrough for semiconductor technology and we are really proud. The whole group has done a great job and it's great to see that our results have been recognized not only in Europe but also in the USA and Japan.

We have a great team here at Fraunhofer IAF that has put all its energy into this goal. Our technicians even reconfigured the epitaxy reactor we used. Our institute director Oliver Ambacher and our head of the business unit have always supported and motivated us to continue.  

What are your next steps now?

We still have a lot of research to do. The main goal is to make the AlScN for HEMT applications top notch. We want to achieve better performance than modern AlGaN HEMTs. We’ve done some preliminary testing and have achieved very good results. We are working on optimizing the parameters such as a cleaner scandium-source material. Ultimately, we want to transfer our technology to a larger reactor in order to achieve a higher technology readiness level so that the industry can use our technology. 

What do you think the world will look like in 30 years?

Oh, there will certainly be quantum computers and I hope that our technology can help achieve this. I think that robots will also become more numerous and normal in our lives. My big hope is that we will succeed in making the energy supply sustainable. And that the process of energy conversion itself is green, so that by-products like CO₂ also become a resource. We have to bring nature into our laboratories and learn from it. I am sure that with the synergy of all our knowledge –  chemistry, biology, physics, electrical engineering and so on –  we can create a world that is a gift to our children.

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Stefano Leone and his research group have achieved the previously impossible: For the first time in the world, they have grown aluminum scandium nitride (AlScN) by metalorganic chemical vapor deposition (MOCVD). This paves the way for the production of power electronics based on the high-performance material AlScN with good industrial quality and productivity. The patent is called »Verfahren und Vorrichtung zur Herstellung einer Schicht, damit versehenes Substrat und dessen Verwendung«.