Creative Way to bring New Materials to Integrated Circuits
Silicon has been serving us very well for a long time, but we are rapidly approaching its limits and we will have to find a way to continue advancing. One possibility is to add new materials to the mix and exploit their properties, which can be superior to silicon's. Researchers at the University of California, Davis have recently found a way to achieve this by taking advantage of nanowires.
Growing layers of a nonsilicon material on top of a silicon substrate is prohibitively difficult, due to mismatches in crystal structures. The researchers got around this problem by not growing full layers of materials like gallium nitride, gallium arsenide, or indium phosphide, but growing nanopillars of these other material. Of course free-standing pillars are not too useful on their own, which is why the researchers then grew nanowires to connect them, completing the circuits and transistors they desired.
This use of nanowires does more than just allow nonsilicon materials to be combined with silicon as the structures behave better when heated and cooled. Thermal expansion can be a big problem when combining mismatched materials, but is less an issue in this situation.
Source: University of California, Davis