Electricity makes porous silicon grow.

Several research groups report that they have induced silicon - long considered an "optically dead" material - to emit light when zapped with electrical current. These demonstrations of electroluminescence follow announcements that British and French researchers had used laser light to make porous silicon wafers light up (SN: 8/31/91, p. 135). These unexpected light-emitting properties mean that engineers might successfully use silicon to make optoelectronic devices essential to faster computers, says physicist Frederick Koch of the Technical University of Munich in Germany.

Researchers make silicon porous by putting it in acid. W. Lang and his colleagues at the Institute for Solid State Technology, also in Munich, observe orange light when they apply voltage to a contact atop porous silicon, Lang says. Nobuyoshi Koshida of Tokyo University of Agriculture and Technology  also reports seeing orange electroluminescence in his group's silicon.

Scientists at IBM's Thomas J. Watson Research Center in Yorktown Heights, N.Y., and at Spire Corp. in Bedford, Mass., report building prototype devices for studying the potential applications of porous silicon electroluminescence. A voltage makes these devices give off visible light.

Although many researchers have ideas about how silicon's luminescence occurs, there is no general agreement about what causes silicon to glow.