Trying for a Terahertz Transistor

A new transistor design aims to smash speed records.

Researchers at the University of Rochester believe they know how to make a transistor that, at room temperature, could operate at a blazing three terahertz.

In a ballistic deflection transistor, electrons are guided by an electric field and bounced off a central triangle. Some researchers believe that a transistor with this design could run as fast as 3 terahertz. (Credit: University of Rochester)

The device, dubbed a ballistic deflection transistor, won't be in products anytime soon. But it does embody some interesting design theories.

The semiconductor industry is eagerly looking for alternatives to the traditional transistor because engineers predict the device will reach its speed and size limits within the next two decades. "A lot of people are curious and trying to figure out what the next significant thing will be," says Stan Williams, director of quantum science research at Hewlett-Packard in Palo Alto.

Currently, the fastest transistors--found in telecommunication technology--are clocked at a couple hundred gigahertz. Some transistors can run at about 500 gigahertz, but only when they are cooled to low temperatures. The ballistic deflection transistor could break those speed records at room temperature by channeling electrons in a different way.

This early prototype could have potential, says Williams. But he's skeptical that this design will replace present-day transistors. Researchers at HP worked on a similar idea many years ago, Williams said, but decided not to pursue it because, at the time, the transistors required extremely low temperatures to work. However, if the researchers' prototype works as well as they predict at room temperature, he says, "then they've got something."

In contemporary transistors, electrons slog through layers of semiconductor material and collect on a capacitor: a charged capacitor represents a binary 1, or "on" state, whereas a discharged capacitor represents a 0, or "off" state.

In the researcher's prototype, however, electrons would flow in a straight line along a two-dimensional path. An electric field would manipulate their direction as they bounce off of a tiny triangular structure in the path: deflecting to the right corresponds to a 1, and deflecting to the left corresponds to a 0.