Motorola mixes up chip chemistry for faster circuits

Researchers combine silicon with gallium arsenide to create durable, cost-effective optical chips for the first time
Written by Rupert Goodwins, Contributor

Motorola's semiconductor research labs have announced a new technique for making chips that could cut the cost of very fast devices by up to ten times. The technology layers gallium arsenide (GaAs) on top of silicon, marrying the very high speed of the first compound with the ease of manufacturing of the second. Until now, GaAs circuits could only be produced by expensive, non-standard processes.

The circuits made by the new method will be particularly interesting to the optoelectronic and wireless data industries, two areas where future growth is intimately tied to greater bandwidth and higher speed. As well as making GaAs production cheaper, Motorola says that there are many benefits from being able to tightly integrate very fast areas of a design with silicon computation and control circuits on the same chip. It predicts applications across the board of consumer and commercial electronics.

Motorola's system works by introducing a new layer of strontium titanate between the silicon and GaAs. Without this, the molecular structures of the two layers are physically mismatched and stresses in the GaAs layer leads to microscopic disruption in its crystal lattice. The new layer acts as a molecular-level adaptor plug. Although the concept is simple, it has taken decades of development to reach this point and Motorola has in the region of 270 patents covering all aspects of the process.

The company has started a subsidiary to widely licence the technology, which is initially looking at optical networking and lighting systems. The technique is not limited to gallium arsenide -- other gallium compounds have been used, and the same idea is thought to be workable for still more exotic semiconductors.

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