Roland Piquepaille's Technology Trends
How new technologies are modifying our way of life

mardi 6 janvier 2004

Two famous professors of the University of Illinois at Urbana-Champaign (UIUC), Nick Holonyak, Jr., inventor of the light-emitting diode (LED), and Milton Feng, who created the world's fastest transistor last summer (509 GHz), have devised a new unusual transistor with three ports, an input, an electrical output and an optical output ones. This new light-emitting transistor could revolutionize the electronics industry.

Professors Nick Holonyak, Jr. and Milton Feng at UIUC have uncovered a light-emitting transistor that could make the transistor the fundamental element in optoelectronics as well as in electronics. The scientists report their discovery in the Jan. 5 issue of the journal Applied Physics Letters.

The abstract of their paper, "Light-emitting transistor: Light emission from InGaP/GaAs heterojunction bipolar transistors," is available online.

"We have demonstrated light emission from the base layer of a heterojunction bipolar transistor, and showed that the light intensity can be controlled by varying the base current," said Holonyak.
"This work is still in the early stage, so it is not yet possible to say what all the applications will be," Holonyak said. "But 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."

Here is how this new light-emitting transistor works (Credit: UIUC).

New light-emitting transistor

The researchers used unusual materials, indium gallium phosphide and gallium arsenide, to build their light-emitting transistors.

"In a bipolar device, there are two kinds of injected carriers: negatively charged electrons and positively charged holes," Holonyak said. "Some of these carriers will recombine rapidly, supported by a base current that is essential for the normal transistor function."
The recombination process in indium gallium phosphide and gallium arsenide materials also creates infrared photons, the "light" in the researchers’ light-emitting transistors. "In the past, this base current has been regarded as a waste current that generates unwanted heat," Holonyak said. "We’ve shown that for a certain type of transistor, the base current creates light that can be modulated at transistor speed."

The researchers have reached a frequency of 1 megahertz, but think higher speeds are granted. This sure will be needed before revolutionizing the electronics industry.

Source: James E. Kloeppel, UIUC, January 5, 2004

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