Scientists have invented a new transistor that can switch on and off 140 billion times a second, 12 times faster than transistors used in supercomputers.

The "bipolar transistor" was created at the AT&T Bell Laboratories in Murray Hill, N.J., and could have applications in computers as well as microwave communications and light-wave communications systems that use lasers.A transistor is a solid-state device that controls the flow of electrons in a circuit. In radios, for example, transistors are used to amplify weak electrical signals such as those received by the antenna.

Most transistors, invented at Bell Laboratories in 1947, are made from crystals of silicon or germanium that have been "doped" with specific impurities to achieve a desired effect.

The bipolar transistors are made of indium phosphide and gallium indium arsenide, complex crystals that help permit electrons to move 12 times faster than in other transistors.

Bipolar transistor inventors Young-Kai Chen, A.F.J. Levi, Richard Nottenburg and Morton Panish used a technique called gas-source molecular beam epitaxy, or GSMBE, to create the new device.

"We utilize high-speed electrons to relay the signal in the transistor," Chen said in a statement issued by Bell Laboratories. "The electrons operate like a skier who acquires extremely high speed, as if he were going down a cliff.

"By properly engineering the ski path for the downhill electrons with GSMBE technology, we make it possible for the downhill electrons to switch a signal in a very short time," Chen said.

GSMBE was invented by Panish in 1980.

The four scientists presented a paper on their new transistor at the International Electron Device Meeting, sponsored by the Institute of Electrical and Electronic Engineers, in San Francisco.