Silicon chips have revolutionized electronics, but for certain purposes, such as radio frequency transmission, chips made from compound semiconductors like gallium arsenide or indium phosphide work much better. Erik Bakkers of Philips Research Laboratories in Eindhoven, the Netherlands, has found a way to mix semiconductors on a single chip.
Different semiconductors are normally incompatible, partly because they expand at different rates when heated. Combining them thus leads to physical strain that reduces performance. Bakkers solved the problem by building circuits out of nanowires. Because the point of contact between the different semiconductors is small--just a few tens of nanometers--there is no strain.
To grow a nanowire, Bakkers places a gold nanoparticle on top of a silicon wafer. Then he exposes the wafer to a vapor of, say, gallium arsenide; the nanoparticle catalyzes the growth of a gallium arsenide nanowire.
This technique opens up possibilities for multipurpose chips that could be used in wireless devices and other applications. It could also make it easier for engineers to take advantage of the inherent properties of compound semiconductors to create highly efficient LEDs, faster transistors, optical interconnects to rapidly shunt data around chips, or fast, highly sensitive biosensors to detect diseases.
--Neil Savage
