Breaking barriers

A new type of transistor structure, invented by scientists at the

, has broken the 600 gigahertz speed barrier. The goal of a terahertz transistor for high-speed computing and communications applications could now be within reach.

The new device – built from indium phosphide and indium gallium arsenide – is designed with a compositionally graded collector, base and emitter to reduce transit time and improve current density. With their pseudomorphic heterojunction bipolar transistor, the researchers have demonstrated a speed of 604 gigahertz, which is said to be the fastest transistor operation to date.

“Pseudomorphic grading of the material structure allows us to lower the bandgap in selected areas,” said Milton Feng, the Holonyak Professor of Electrical and Computer Engineering and a researcher at the Co-ordinated Science Laboratory at Illinois. “This permits faster electron flow in the collector. The compositional grading of the transistor components also improves current density and signal charging time.”