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29 January 2007


Picogiga samples SopSiC composite substrates for GaN-based RF power devices

Picogiga International of Les Ulis, France, a division of silicon-on-insulator substrate manufacturer Soitec, has announced availability of pre-production samples of its silicon-on-polysilicon-carbide (SopSiC) composite engineered substrates for low-cost gallium nitride-based RF power devices.

Picogiga says that SopSiC bridges the compound epiwafer void between low-cost, low-power GaN-on-Si and high-cost, high-power single-crystal SiC for GaN HEMT devices. SopSiC is designed to provide cost-efficient substrates for high-power devices used in wireless (RF) communication systems such as radar, satellite communications and base-stations, the firm adds.

"SopSiC is an excellent example of how Smart Cut engineered substrates can be used to solve challenges for III-V applications,” says Picogiga’s chief operating officer Jean-Luc Ledys. "While GaN on both silicon and silicon carbide is part of our existing epiwafer product line for high-power applications, SopSiC gives our customers a significantly better performing solution than silicon - and a considerably less expensive solution than SiC,” he adds. “In terms of dollar per watt, SopSiC is an extremely attractive solution.”

In November, the three-year European R&D project HYPHEN (Hybrid Substrates for Competitive High Frequency Electronics), in which Picogiga participates, announced initial material characterization results that suggested that GaN HEMTs on SopSiC substrates are more reliable than on silicon.

The SopSiC structure is engineered using Soitec’s Smart Cut layer transfer and bonding technology, which it uses to make silicon-on-insulator wafers. It includes a bottom layer of polysilicon carbide, an insulating buried oxide layer, and a high-resistivity (1-1-1) silicon top layer. The top layer serves as the seed layer for GaN epitaxial growth using either MBE or MOCVD. The bottom polysilicon carbide layer is designed to evacuate the heat generated by high-power HEMT devices. SopSiC marks the first industrialized compound epiwafer product combining both Smart Cut and MBE technologies, says Picogiga.

Samples are available in 3-inch and 4-inch diameters. But because the fabrication process is not limited by the small diameters of bulk single-crystal SiC, the process is scalable to the larger wafer sizes standard for silicon - a 6-inch version is currently in development.

See related items:

HYPHEN program indicates GaN HEMTs on composite substrates more reliable than on silicon

Picogiga's sales fall due to weaker demand for RF applications