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Hybrid bipolar transistor emits light

Posted: 16 Jan 2004 ?? ?Print Version ?Bookmark and Share

Keywords:bipolar transistor? indium phosphide/gallium arsenide materials system? university of Illinois?

Integrated optoelectronics could get a boost from the discovery of a bipolar transistor that emits light from its base region. Built in an indium phosphide/gallium arsenide materials system, the device operates as a high-speed bipolar transistor while simultaneously modulating internally generated infrared light.

Laser diode pioneer Nick Holonyak of the University of Illinois developed the hybrid part in collaboration with UI colleague Milton Feng, who recently built a bipolar transistor that set a speed record.

The transistor produces optical output through the recombination of holes and electrons that are injected into the base of the transistor. The recombination effect has long been known to bipolar-transistor designers since it usually generates waste heat, representing a source of inefficiency.

Normally, the effect is minimized in order to maximize the efficiency of the transistors. Holonyak and Feng decided instead to create an architecture that would enhance the effect, to produce enough output to be useful in optical signaling.

"A light-emitting transistor opens up a rich domain of integrated circuitry and high-speed signal processing that involves both electrical signals and optical signals," said Holonyak, who has built his career on innovations in light-emitting devices.

In 1961, while working as a researcher at General Electric, Holonyak invented the visible-light LED. He went on to create the first laser diode to operate in the visible spectrum. More recently, Holonyak has done seminal work on creating optical oxide-isolation processes that have enhanced vertical-cavity surface-emitting lasers, a rapidly growing technology finding applications in optical networking systems.

Last November, Feng reported a bipolar transistor operating at a record 509GHz. The speed was achieved by building ultra-narrow superlattice structures to confine carriers.

- Chappell Brown

EE Times

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