Transistor Material Beyond Silicon

Jesus del Alamo

Each of us has several billion transistors working on our behalf every day in our phone, laptop, iPod, car, kitchen and more. Estimates that float around in the semiconductor industry circle state that within the next 10 to 15 years we will reach the limit, in terms of size and performance, of the silicon transistors key to the industry. As a result, both academic and industrial laboratories around the world are working on new materials and technologies that may be able to reach beyond the limits of silicon. Scientists are looking at new semiconductor materials for transistors that will continue to improve in performance, while devices get smaller and smaller.

Here steps in Jesus del Alamo, an MIT professor of electrical engineering and computer science and member of MIT's Microsystems Technology Laboratories (MTL). One such material del Alamo and his students at the MTL are investigating is a family of semiconductors known as III-V compound semiconductors. Unlike silicon, these are composite materials. A particularly hot prospect is indium gallium arsenide (InGaAs), a material in which electrons travel many times faster than in silicon. As a result, it should be possible to make very small transistors that can switch and process information very quickly.

Del Alamo's group recently demonstrated this by fabricating InGaAs transistors that can carry 2.5 times more current than state-of-the-art silicon devices. More current is the key to faster operation. In addition, each InGaAs transistor is only 60 nanometers (billionths of a meter), long. That's similar to the most advanced 65-nanometer silicon technology available in the world today.

Del Alamo notes, however, that InGaAs transistor technology is still in its infancy. Some of the challenges include manufacturing transistors in large quantities, because InGaAs is more prone to breakage than silicon. But del Alamo expects prototype InGaAs microdevices at the required dimensions to be developed over the next two years and the technology to take off in a decade or so.

The work was presented at the IEEE International Electron Devices Meeting Dec. 11-13 by Dae-Hyun Kim, a postdoctoral associate in the laboratory of Jesus del Alamo.