Nav: Home

New method gives robust transistors

January 07, 2020

A new method to fit together layers of semiconductors as thin as a few nanometres has resulted in not only a scientific discovery but also a new type of transistor for high-power electronic devices. The result, published in Applied Physics Letters, has aroused huge interest.

The achievement is the result of a close collaboration between scientists at Linköping University and SweGaN, a spin-off company from materials science research at LiU. The company manufactures tailored electronic components from gallium nitride.

Gallium nitride, GaN, is a semiconductor used for efficient light-emitting diodes. It may, however, also be useful in other applications, such as transistors, since it can withstand higher temperatures and current strengths than many other semiconductors. These are important properties for future electronic components, not least for those used in electric vehicles.

Gallium nitride vapour is allowed to condense onto a wafer of silicon carbide, forming a thin coating. The method in which one crystalline material is grown on a substrate of another is known as "epitaxy". The method is often used in the semiconductor industry since it provides great freedom in determining both the crystal structure and the chemical composition of the nanometre film formed.

The combination of gallium nitride, GaN, and silicon carbide, SiC (both of which can withstand strong electric fields), ensures that the circuits are suitable for applications in which high powers are needed.

The fit at the surface between the two crystalline materials, gallium nitride and silicon carbide, is, however, poor. The atoms end up mismatched with each other, which leads to failure of the transistor. This has been addressed by research, which subsequently led to a commercial solution, in which an even thinner layer of aluminium nitride was placed between the two layers.

The engineers at SweGaN noticed by chance that their transistors could cope with significantly higher field strengths than they had expected, and they could not initially understand why. The answer can be found at the atomic level - in a couple of critical intermediate surfaces inside the components.

Researchers at LiU and SweGaN, led by LiU's Lars Hultman and Jun Lu, present in Applied Physics Letters an explanation of the phenomenon, and describe a method to manufacture transistors with an even greater ability to withstand high voltages.

The scientists have discovered a previously unknown epitaxial growth mechanism that they have named "transmorphic epitaxial growth". It causes the strain between the different layers to be gradually absorbed across a couple of layers of atoms. This means that they can grow the two layers, gallium nitride and aluminium nitride, on silicon carbide in manner so as to control at the atomic level how the layers are related to each other in the material. In the laboratory they have shown that the material withstands high voltages, up to 1800 V. If such a voltage were placed across a classic silicon-based component, sparks would start flying and the transistor would be destroyed.

"We congratulate SweGaN as they start to market the invention. It shows efficient collaboration and the utilisation of research results in society. Due to the close contact we have with our previous colleagues who are now working for the company, our research rapidly has an impact also outside of the academic world", says Lars Hultman.
-end-
The research has been funded by research grants from the Knut and Alice Wallenberg Foundation and from the CoolHEMT programme, part of the EU Horizon 2020. The article, which is linked below, was specially selected by the editor of Applied Physics Letters, and is one of the journal's most read articles, with nearly 1,000 downloads one week after publication on 25 November 2019. It is also featured on the journal´s cover.

Transmorphic Epitaxial Growth of AlN Nucleation Layers on SiC Substrates for High-Breakdown Thin GaN Transistors, Jun Lu, Jr-Tai Chen, Martin Dahlqvist, Riad Kabouche, Farid Medjdoub, Johanna Rosen, Olof Kordina, and Lars Hultman. Appl. Phys. Lett. 115, 221601 (2019). doi 10.1063/1.5123374
https://doi.org/10.1063/1.5123374
https://aip.scitation.org/doi/10.1063/1.5123374

Linköping University

Related Semiconductors Articles:

The future of semiconductors is clear
Mobility is a key parameter for semiconductor performance and relates to how quickly and easily electrons can move inside a substance.
Semiconductors can behave like metals and even like superconductors
The crystal structure at the surface of semiconductor materials can make them behave like metals and even like superconductors, a joint Swansea/Rostock research team has shown.
KIST unveils the mystery of van der Waals magnets, a material for future semiconductors
The Korea Institute of Science and Technology (KIST) have announced that their team successfully controlled the magnetic properties of FGT (Fe3GeTe2) in a joint research project with for Basic Science(IBS) team.
Blue-emitting diode demonstrates limitations and promise of perovskite semiconductors
Halide perovskites have garnered attention because they're highly efficient at capturing energy in solar cells and efficient emitters in diodes.
Bending an organic semiconductor can boost electrical flow
Slightly bending semiconductors made of organic materials can roughly double the speed of electricity flowing through them and could benefit next-generation electronics such as sensors and solar cells, according to Rutgers-led research.
Stretchable, degradable semiconductors
To seamlessly integrate electronics with the natural world, materials are needed that are both stretchable and degradable -- for example, flexible medical devices that conform to the surfaces of internal organs, but that dissolve and disappear when no longer needed.
Scientists spy unstable semiconductors
Scientists from Cardiff University have, for the first time, spotted previously unseen 'instabilities' on the surface of a common compound semiconductor material.
Researchers repurpose failed cancer drug into printable semiconductor
Many potential pharmaceuticals end up failing during clinical trials, but thanks to new research from the University of Illinois, biological molecules once considered for cancer treatment are now being repurposed as organic semiconductors for use in chemical sensors and transistors.
Does one size does fit all? A new model for organic semiconductors
A team including researchers from Osaka University has used a single rubrene crystal to investigate the room temperature behavior of organic single crystals, and in so doing have dispelled previously-held assumptions based on inorganic semiconductor behavior.
UK researchers develop ultrafast semiconductors
UK researchers have developed world-leading Compound Semiconductor (CS) technology that can drive future high-speed data communications.
More Semiconductors News and Semiconductors Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.