Towards the terahertz transistor

Researchers at the University of Illinois at Urbana-Champaign have broken their own record for the world’s fastest transistor. Their latest device, with a frequency of 509 GHz, is 57 GHz faster than their previous record holder.

‘The steady rise in the speed of bipolar transistors has relied largely on the vertical scaling of the epitaxial layer structure to reduce the carrier transit time,’ said Milton Feng, the Holonyak Professor of Electrical and Computer Engineering at Illinois, whose team has been working on high-speed compound semiconductor transistors since 1995.

‘However, this comes at the cost of increasing the base-collector capacitance. To compensate for this unwanted effect, we have employed lateral scaling of both the emitter and the collector,’ he added.

Feng and graduate students Walid Hafez and Jie-Wei Lai fabricated the high-speed devices in the University’s Micro and Nanotechnology Laboratory. Unlike traditional transistors, which are built from silicon and germanium, the Illinois transistors are made from indium phosphide and indium gallium arsenide.

In January, Feng’s group announced a transistor with a 150nm collector and a top frequency of 382GHz. In May, the group reported a 452GHz device with a 25nm base and a 100nm collector. Further scaling reduced the collector size to 75nm, resulting in a 509GHz device, announced last month.

‘Our ultimate goal is to make a Terahertz transistor,’ Feng concluded.