Fastest Transistor Approaches Terahertz Speed
Peter Singer, Editor-in-Chief -- Semiconductor International, 1/1/2007
Scientists at the University of Illinois at Urbana-Champaign have again broken their own speed record for the world's fastest transistor. With a frequency of 845 GHz, their latest device is ~300 GHz faster than transistors built by other research groups, and approaches the goal of a terahertz device.
Made from indium phosphide and indium gallium arsenide, “The new transistor utilizes a pseudomorphic grading of the base and collector regions,” said Milton Feng, Holonyak Chair Professor of electrical and computer engineering at U of I. “The compositional grading of these components enhances the electron velocity, hence, reduces both current density and charging time.”
With this latest device, Feng and his research group have taken the transistor to a new range of high-speed operation, finally bringing the “Holy Grail” of a terahertz transistor within reach. In addition to using pseudomorphic material construction, the researchers also refined their fabrication process to produce tinier transistor components. For example, the transistor's base is only 12.5 nm.
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Clocking in at 845 GHz, the transistor is fabricated with InP and GaAs, and employs pseudomorphic grading of the base and collector regions. (Source: University of Illinois)
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“By scaling the device vertically, we have reduced the distance electrons have to travel, resulting in an increase in transistor speed,” said graduate student William Snodgrass, who described the new device at the International Electronics Device Meeting (IEDM) , held in San Francisco Dec. 11-13. “Because the size of the collector has also been reduced laterally, the transistor can charge and discharge faster.”
Operating at room temperature (25°C), transistor speed is 765 GHz. Chilled to -55°C, the speed increases to 845 GHz. Feng, Snodgrass and graduate student Walid Hafez (now at Intel Corp .) fabricated the high-speed device in the university's Micro and Nanotechnology Laboratory. In addition to further increasing the transistor speed, Feng wants to reduce the current density even more, which will reduce junction temperature and improve device reliability.
Find more information on wafer processing.
