- 15 February 2006 -

World first: GaN-on-diamond

Group4 Labs LLC, of Menlo Park, USA, has developed what they claim to be the world’s first gallium nitride (GaN)-on-diamond semiconductor wafer. The Xero Wafer, which has been under development for three years, sits less than 0.5 nanometres away from a synthetic diamond substrate. It offers high temperature resilience for high-power, high-frequency electronic, solid-state white lighting, photonics and military applications. Military applications include: microwave and millimetre wave circuits for radar, and communications satelite. It is ideal for use in the conventional epitaxial growth of GaN and its aluminium and indium-based alloys, and is initially available in 10mm x 10mm square pieces.

Using the new technology, the GaN layer is atomically attached to a freestanding, proprietary polycrystalline chemical-vapour-deposited (CVD) diamond substrate (25-microns thick). The GaN exposed is an atomically smooth surface finish that is ready for further epitaxial processing. The wafer is available freestanding or on a disposable, silicon wafer mount.

Designed to address the heat problems associated with high power and high-speed transistors, the GaN-on-diamond wafer offers a solution by extricating heat from the chip’s core almost at the instant that it is generated. This is due to the sub-nanometre proximity of the chip’s active region to diamond. CVD diamond’s thermal conductivity is about 3x to 30x more than that of conventional semiconductors. A 3x improvement in the thermal conductivity of a transistor array could boost the array’s power-density by ten fold.

The new wafer is set to compete with existing technologies; the three contenders being GaN-on-silicon carbide, GaN-on-silicon, and GaN-on-sapphire. To date, GaN-on-silicon carbide has produced the most powerful transistors on the market, with GaN-on-silicon, and GaN-on-sapphire producing the second and third most powerful respectively. However, Group4Labs' assert that GaN-on-diamond can improve the power density of an array of transistors by 5x to 100x over GaN-on-silicon carbide, depending on operating conditions such as temperature, and drive current.

Group4Labs’ CEO, Felix Ejeckam, said: “This new type of semiconductor allows manufacturers of power amplifiers (for cellular base stations), microwave and millimeter-wave circuits, UV laser diodes and ultra-bright blue/green/white LEDs, to achieve power density and efficiency levels never before attained.”

Priced at $450 per unit, the new wafers are available through the company’s online store.

Web: www.Group4Labs.com/Products