Superior GaN-like material made using MOCVD
Researchers at Fraunhofer IAF (Freiburg, Germany) have succeeded in fabricating the promising semiconductor material aluminium yttrium nitride (AlYN) using the MOCVD process.
AlYN has excellent material properties and potential for use in energy-efficient high-frequency and high-performance electronics. It has a close crystal lattice match to GaN but has only previously been made using magnetron sputtering, counting against high volume manufacturing.
The Fraunhofer Institute for Applied Solid State Physics IAF have now succeeded in fabricating the new material using metal-organic chemical vapor deposition (MOCVD) technology, thus enabling the development of new applications.
“AlYN is a material that enables increased performance while minimizing energy consumption, paving the way for innovations in electronics that our digitally connected society and its ever-increasing technology demands urgently need,” said Stefano Leone, scientist at Fraunhofer IAF in the field of epitaxy, in a statement.
AlYN has recently been shown to display ferroelectricity making it a potential non-volatile memory semiconductor.
In 2023, the Fraunhofer IAF research group succeeded in depositing a 600nm-thick AlYN layer with wurtzite crystal structure containing more than 30 percent yttrium. Now the researchers have fabricated AlYN/GaN heterostructures with a precisely adjustable yttrium concentration, which are characterized by excellent structural quality and electrical properties. The heterostructures have an yttrium concentration of up to 16 percent.
“We were able to observe impressive values for sheet resistance, electron density and electron mobility. These results showed us the potential of AlYN for high-frequency and high-performance electronics,” Leone said.
An AlYN/GaN heterostructure promises to enable the development of semiconductor components with improved performance and reliability. In addition, AlYN has the ability to induce a two-dimensional electron gas (2DEG) in heterostructures. Recent research results from Fraunhofer IAF show optimal 2DEG properties in AlYN/GaN heterostructures at an yttrium concentration of about 8 percent.
The material characterization results also show that AlYN can be used in high electron mobility transistors (HEMTs).
Fraunhofer IAF were are able to grow AlYN/GaN heterostructures on 4-inch SiC wafers in a commercial MOCVD reactor with the promise of scale-up to six-inch and 200mm-diameter wafers.
One remaining obstacle to the deployment of AlYN is its susceptibility to oxidation. Leone said that the use of high-purity pre-cursor materials, protective coatings and adaptions of manufacturing techniques could help and are topics for further research.
Related links and articles:
Leone et al. “Metal-Organic Chemical Vapor Deposition of Aluminum Yttrium Nitride”, Phys. Status Solidi RRL 17 2300091 (2023) https://doi.org/10.1002/pssr.202300091
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