Composite Substrates Promise Boost for GaN RF

Results of the HYPHEN project indicate a new path to high-volume, high-power, and high-frequency wireless applications.

The European HYPHEN GaN-RF project is developing and evaluating new types of composite substrates based on silicon and silicon carbide materials. These new substrates are designed to provide cost-efficient solutions for advanced high-power devices used in wireless communication systems such as radar, satellite communications and base stations.

During the first year of this three-year project, we compared the industry’s two standard materials – GaN on bulk silicon and GaN on bulk SiC – with GaN grown on two of the most promising composite, engineered substrates: silicon on poly-crystalline silicon carbide (SopSiC); and SiC on poly-crystalline SiC (SiCopSiC). These substrates were engineered using Soitec’s Smart Cut™ technology.

More reliable epitaxy

The initial material characterization results show that all the critical performance factors (crystal quality, mobility, surface morphology and so forth) of GaN on composite substrate materials are equal to or even better than the current industry standard materials. These substrate comparisons were assessed using the two most established epitaxy techniques: metallic organic CVD (MOCVD) and molecular beam epitaxy (MBE).

The new composite substrates also demonstrated superior results in terms of pilot production yield and repeatability. According to the preliminary results, the epitaxy of GaN HEMT on SopSiC composite substrates is more reliable than on conventional silicon substrates. SopSiC as a substrate for GaN growth also has the advantage of being substantially cheaper and better suited to high-volumes than bulk SiC substrates.

The HYPHEN project is developing and characterizing the complete technology chain, from substrate to GaN HEMT device. The second phase, which is now underway, involves device processing.

Project partners include: Picogiga, University of Padova DEI, Alcatel-Thales III-V Lab, the Research Institute for Technical Physics and Material Science (Hungary), Norstel, Institute of Electron Technology (Poland), IEMN/CNRS (France) and UMS. The work is partially supported by the European Community, under the Innovation Society Technologies (IST) program of the 6th Framework Program.

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