November 9, 2006 – A European R&D program says it has achieved “excellent” initial material characterization results for gallium nitride (GaN) on compound engineered substrates, in its three-year efforts to develop and evaluate new silicon and silicon carbide-based substrates for GaN-based RF devices, in applications such as radar, satellite communications and base stations.

The HYPHEN project, launched in 2005, aims to bridge the gap between low-performance, low-cost single crystal silicon and high-performance, high-cost single crystal silicon carbide, by creating scalable composite substrates with dielectric and thermal properties far above those of silicon, yet costing significantly less than semi-insulating SiC.

Last year the project compared GaN on bulk silicon and GaN on bulk SiC with GaN grown on two composite engineered substrates: silicon-on-polycrystalline silicon carbide (SopSiC), and SiC on polycrystalline SiC (SiCopSiC), using Soitec’s technology for use with silicon-on-insulator wafers. Examined with metallic organic CVD (MOCVD) and molecular beam epitaxy (MBE) techniques, the GaN-composite substrate materials showed critical performance factors (e.g. crystal quality, mobility, and surface morphology) that equaled or exceeded current materials.

The results also suggested the composite substrates were better attuned to pilot production yields and repeatability. Preliminary results showed epitaxy of GaN HEMT on SopSiC composite substrates were more reliable than on conventional silicon substrates, in addition to being cheaper and better suited to high volumes for frequency scale of <10GHz.

“Until now, designers of GaN-based RF power devices have had to choose between the extremes of high-performance/high-cost SiC starting substrates and low-performance/low-cost silicon,” said Philippe Bove, HYPHEN project leader, in a statement. “The HYPHEN material characterization results indicate that composite materials like SopSiC provide a scalable, cost-effective substrate solution that can fill the chasm between the very high and the very low ends of the cost-performance trade-off.”

Participants in the HYPHEN project include Picogiga International (a division of the Soitec Group); The U. of Padova (Italy); Alcatel-Thales III-V Lab (France); the Research Institute for Technical Physics and Material Science (Hungary); SiC wafer supplier Norstel (Sweden); the Institute of Electron Technology (Poland); the IEMN research unit of French national research organization CNRS; and United Monolithic Semiconductors, a Thales-EADS joint venture. The work is partially supported by the European Community, under the Innovation Society Technologies (IST) program of the 6th Framework Program.