Northrop Grumman Creates One-Terahertz Transistor

The emphasis at CPU companies in recent years has been on cores, not clock speed. Try telling that to defense contractor Northrop Grumman, for which 2.4 or 3.2 gigahertz is now small potatoes: It’s developed the first 1,000GHz transistor.

The company described how it developer the 1 terahertz (THz) transistor in a paper presented at the 2007 International Electron Devices Meeting in Washington, D.C., sponsored by the Electron Devices Society of the Institute of Electrical & Electronic Engineers.

The High Electron Mobility Transistor (HEMT) is unlike anything you’ll see anytime soon from Intel or AMD. It’s based on an indium phosphide compound instead of the silicon oxide used in a typical CPU. Indium phosphide is a more expensive compound to use but its atomic composition makes it ideal for high-frequency operation.

“Our primary focus has been on compound semiconductors based on indium phosphide and gallium arsenide because they offer very high-speed performance,” said Tom Romesser, vice president and general manager of the Technology and Emerging Systems Division at Northrop Grumman. “We look at them for very high-speed analog performance. Having focused on that, we take a different approach from that of silicon-based manufacturers.

The 1THz clock speed is the HEMT’s theoretical maximum frequency of oscillation, not its average or sustained performance rate, but it’s still fast even at a sustained load. Northrop conducted tests with NASA’s Jet Propulsion Laboratory in Pasadena, Calif. and validated the transistor by operating a three-stage millimeter-wave integrated circuit low-noise amplifier at 340GHz with greater than 15 decibel gain.

In plain English, that means tremendous power throughput, but also a trade-off. The HEMT transistor can only be used in very specialized cases, where power or signal amplification is required. The NASA test, for example, only used three transistors. Intel’s new quad core Penryn processor has 820 million transistors.

“They [the transistor] perform a very specific function,” said William Deal, a Northrop engineer and co-author of the paper. “It’s not a digital circuit with millions of logic gates working together.”

Perhaps just as remarkable, Northrop Grumman claims to use a 35nm gate process to manufacture the transistor. Intel is at 45nm while AMD is making the move to 45nm, with 32nm a few years off for both companies as well as for IBM.

Northrop has its own fabrication facilities to make processors in the limited volumes it needs. Since its business is highly vertical, chips are done in smaller batches. Romesser said the cost isn’t quite as expensive as one might think, and Intel/AMD don’t make for a good comparison.

“The cost of semiconductor foundries are for producing product in commercial volumes,” he said.

This technology can find its way into other consumer products, however. Deal pointed out that at high frequencies, silicon is severely limited — making the HEMT a compelling option.

One potential area of use for the HEMT transistor is a 60GHz wireless HDTV transmitter. The HD signal would come into a home via cable or satellite and then could be transmitted wirelessly around the home to HDTV sets, thereby eliminating the need for expensive HDMI cables.

Another example Romesser cited is atmospheric monitoring, where sensors need to operate in the 80GHz to 250GHz range.

“These types of transistors, with their capability, enable transitions of global climate monitoring for better long-range forecasts,” he said. “So NASA and NOAA and the National Weather Service will get better sensors.”

Romesser estimates those sensors should be available within the next few years.

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