Almost all computer chips use two types of transistors: one called p-type, for positive, and one called n-type, for negative. Improving the performance of the chip as a whole requires parallel improvements in both types. At the IEEE’s International Electron Devices Meeting (IEDM) in December, researchers from MIT’s Microsystems Technology Laboratories (MTL) presented a p-type transistor with the highest “carrier mobility” yet measured. By that standard, the device is twice as fast as previous experimental p-type transistors and almost four times as fast as the best commercial p-type transistors.
Judy Hoyt, a professor of electrical engineering and computer science; her graduate students Winston Chern, lead author on the new paper, and James T. Teherani; Pouya Hashemi, who was an MIT postdoc at the time and is now with IBM; Dimitri Antoniadis, the Ray and Maria Stata Professor of Electrical Engineering; and colleagues at MIT and the University of British Columbia achieved their record-setting hole mobility by “straining” the germanium in their transistor — forcing its atoms closer together than they’d ordinarily find comfortable. To do that, they grew the germanium on top of several different layers of silicon and a silicon-germanium composite. The germanium atoms naturally try to line up with the atoms of the layers beneath them, which compresses them together. Read the article on MIT news. photo courtesy of Winston Chern, Pouya Hashemi and James Teherani