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13 December 2006


MIT demonstrates InGaAs transistors that could succeed silicon

At this week’s IEEE International Electron Devices Meeting (IEDM) in San Francisco, CA, USA, the Massachusetts Institute of Technology (MIT) presented results on InGaAs-based high-electron mobility transistors (HEMTs) with thin InAlAs barrier layers that could succeed silicon in logic chips.

The increase in performance of CMOS-based ICs with shrinking of the constituent MOSFET transistors is expected to reach a limit for silicon within the next 10-15 years. “Unless we do something very radical pretty soon, the microelectronics revolution that has enriched our lives in so many different ways might come to a screeching halt,” says professor Jesus del Alamo, a member of MIT's Microsystems Technology Laboratories.

InGaAs has much higher electron mobility than silicon, but InGaAs HEMTs have previously been limited to transistor gate lengths of about 100nm. But using the capabilities of MIT’s Microsystems Technology Laboratories, Scanning-Electron-Beam Lithography Facility and the Nanostructures Laboratory, del Alamo’s group fabricated In0.7Ga0.3As quantum-well HEMT transistors on InP substrates using a thinner InAlAs barrier layer than before, allowing devices with a length of just 60nm size (similar to the most advanced 65nm silicon technology available). The devices can carry 2.5 times more current than state-of-the-art silicon devices and provide high performance at supply voltages as low as 0.5V. Del Alamo says that one reason for the performance of the transistors is the high quality of the epitaxial material, grown by epiwafer foundry MBE Technology of Singapore.

The results were described as ‘a very important research milestone’ by Robert Chau, senior fellow and director of transistor research and nanotechnology at Intel, one of the sponsors of the research (along with Microelectronics Advanced Research Corp).

However, Del Alamo notes that InGaAs transistor technology is still in its infancy. 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. "With more work, this semiconductor technology could greatly surpass silicon," he adds.