For about 30 years, researchers have attempted to epitaxially grow one semiconductor material on substrates of another material. If the two materials' lattice constants (the distance between atoms in each crystal) do not differ by more than about 2%, if the thermal coefficients of the two materials are similar, and if several other conditions are met, such epitaxial growth can be done.
Throughout the late 1970s and the 1980s, significant research funds were expended in the attempt to grow gallium arsenide on silicon, initially for military purposes and later for the then-infant cellular telephone market. But no such process even got close to commercialisation. Concurrent technology advances in GaAs technology led most researchers to abandon their efforts to combine GaAs and silicon. Two largely separate semiconductor industries evolved, one working in silicon and another smaller one working in GaAs. Few companies worked 'both sides of the street.' Motorola was one of the relatively few companies to continue in both technologies.
On 4 September, Motorola announced the successful growth of thin-film gallium arsenide circuits on silicon substrates, finally bridging the gap between the two families of materials. This effort, still in the research stage, leverages silicon's physical robustness and well-known process technology with the high circuit speeds and optical properties of GaAs.
So far, Motorola has produced GaAs power amplifiers (on a 300 mm silicon wafer, no less) and then incorporated those devices in cellphones, with device performance equivalent to present-day circuits. Motorola has also built light-emitting diodes in the GaAs thin films (no diode lasers yet, but that doesn't look far away).
Motorola plans to produce mixed GaAs-silicon chipsets in some markets, like the cellular handset market, where the company already has a large footprint. Motorola expects to reach commercialisation in 2003. In other product areas, where the company is not entrenched, Motorola plans to license the technology aggressively. Motorola has also begun to investigate other III-V semiconductor materials like indium phosphide and gallium nitride.
One likely area for licensing is optical networking, where indium gallium arsenide laser diodes and photodetectors can be found at the ends of every fibre, with numerous silicon chips nearby, performing electronic data processing functions.
In-Stat is highly impressed. We tend to be careful when hearing others toss around phrases like 'technology breakthrough' or 'disruptive technology'. We are sceptics.
But every now and then, that sort of phrasing is justified. It is here.
For further information contact Richard Cunningham, In-Stat, rcunningham@instat.com
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