PORTLAND, Ore. -- IBM Research of Zurich is clearing the way for a "new generation of transistor" circuitry based on semiconducting nanowires whose tiny size imparts extraordinary properties not possible with standard bulk materials. The research lab's latest innovation, accomplished with Norwegian University of Science and Technology, is a novel technique of mechanically straining gallium arsenide (GaAs) nanowires on silicon substrates so that they cannot only be tuned to different colors of the spectrum, but can be switched from being emitters of light to being detectors of light as well.
IBM's scanning electron micrograph of a strained gallium arsenide nanowire (orange) that could provide optical capabilities to future silicon chips.
For several years, IBM Zurich has been researching ways to integrate high-electron-mobility III-V materials like gallium arsenide, indium arsenide (InAs,) and indium gallium arsenide (InGaAs) onto standard silicon complementary metal-oxide semiconductor (CMOS) chips. As a result, the lab has explored many novel III-V compounds.
"There are different future candidates to replace/complement the silicon transistor. III-V materials, and in particularly InGaAs ternary alloys, are especially considered for traditional n-channel transistors, because they have higher electron mobility compared to silicon," said Giorgio Signorello, an IBM scientist and an author of its latest paper.
IBM Zurich is also investigating other device architectures, like the Tunneling Field Effect Transistor cast in InGaAs and InAs alloys. The Tunneling FET achieves extraordinary low-energy operation with which IBM hopes to define a new class of nanowire-based CMOS.
"The same class of nanowire materials can also be used to realize some of the optoelectronic components that are needed for the next generation silicon photonic chips. In other words, III-V nanowires enable high-performance CMOS transistors, low-power Tunnel-FETs, silicon photonics, and new physical phenomena which can have technological impact," said Signorello.
The new physical phenomena is realized by straining III-V materials that have been grown as Wurzite crystals -- the same type of atomic structure that gives piezoelectric materials their unusual properties when strained. Instead of generating electricity, as do piezoelectrics, GaAs Wurzite crystals can transform their optical properties when strained, allowing their light emission spectrum to be tuned when stretched, and turning them into light detectors on par with silicon-germanium when they are compressed.