Translucent offers alternative path to GaN-on-silicon

A commercially available “virtual” GaN substrate provides a silicon wafer with engineered epitaxial layers upon which gallium nitride-based LEDs can be fabricated.

Translucent, Inc. (Palo Alto, CA), a manufacturer of rare-earth-oxide (REO) engineered silicon substrates, announced the commercial availability of its vGaN family of silicon-based wafer templates in 100 mm diameter.

The “virtual gallium nitride” wafer substrates are designed to provide a lower-cost alternative to sapphire wafers, while delivering a high-quality epitaxial surface upon which gallium nitride (GaN)-based devices such as LEDs or semiconductor field-effect transistors (FETs) can be fabricated. In FETs, the wide bandgap of the REO layer is expected to lead to much higher breakdown-voltage characteristics.

For solid-state lighting, the wafer stack involves two layers of rare-earth oxide (such as gadolinium oxide, Gd2O3), a silicon substrate with <111> orientation, a (111) silicon interlayer, and a GaN cap. The company uses crystalline REO layers to provide stress relief and wafer flatness through customized lattice engineering.

The vGaN substrate is designed to enable industry-standard MOCVD growth processes (rather than customized) with the low cost structures and economies of scale currently enjoyed by the silicon industry.

Michael Lebby, Translucent’s general manager, noted, “We are bringing a decade of Translucent REO epitaxial experience to bear on the challenge of enabling GaN growth to scale cost-effectively well beyond current limitations. Our vGaN platform is an ‘on-silicon’ technology, allowing us to harness mature silicon-substrate technologies and their low costs, and we expect this to have an extremely beneficial impact in driving down costs for GaN-based LEDs and FETs.”

The vGaN wafers are available today at 100 mm diameters, with 150 and 200 mm becoming available next year.

Several LED manufacturers are pursuing GaN-on-silicon LEDs. Most recently, Bridgelux fabricated GaN-on-si LEDs on a 200 mm wafer in a lab and expects to bring those to market in the next two years.

Separately, the Belgian research institute IMEC is working with its partners Siltronic, Micron Technology, Ultratech and Applied Materials to develop process and equipment technologies for producing LEDs on large-diameter (300 mm) silicon substrates.

Translucent Inc. is a subsidiary of Silex Systems Limited (SLX:ASX), a Sydney, Australian manufacturer of solar cells and panels.

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