LED: The End Of the Light Bulb As We Know It?

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December 12, 2000 (6:03 PM EST)

LED: The End Of the Light Bulb As We Know It?

SAN FRANCISCO -- White LEDs will replace incandescent bulbs in traffic lights and other applications, drawing less power and lasting over ten times longer.

So said Shuji Nakamura, faculty member at the University of California, Santa Barbara, in a keynote address at the International Electron Devices Meeting.

Nakamura, the inventor of the blue, green, and white LEDs, and of the blue laser, had a trailblazing career as a researcher at Nichia Chemical Industries in Tokushima, Japan, before recently accepting an appointment to the College of Engineering at UC Santa Barbara.

In his address, Nakamura said that red, blue, and green LEDs based on indium gallium nitride can outperform incandescent bulbs by using less energy and lasting 10 to 50 times longer. Standard light bulbs typically last one year, Nakamura said.

White LEDs are twice as bright as incandescent bulbs, use non-toxic materials, and are more energy efficient, all of which help preserve natural resources

Reviewing the performance of the latest nitride-based ultraviolet blue, green, amber, and white LEDs, as well as violet/blue laser diodes, Nakamura said the development of InGaN-based compound semiconductors will open the way to solid-state semiconductor light sources.

"In the past, electronic circuits were based on vacuum tubes in spite of poor reliability and durability," he said. "With the advance of solid-state semiconductor materials, all electronics are now highly reliable circuits. Only light sources are still made of an old traditional technology."

Nakamura aims to change that.

At Nichia, where he began his research career in 1979, Nakamura developed a two-flow MOVCD (metal-organic chemical vapor deposition) process.

Now the white LED, which has been described as the Holy Grail of semiconductor optoelectronic engineers, has Nakamura's full attention at UC Santa Barbara.

The MOVCD process, where gases flow in two directions instead of one, thereby improving the material quality, enabled Nakamura to make a blue LED, which led to the white LED and the blue laser. By adding a little more indium, a blue LED can be turned into a green LED. To get a white light, Nakamura placed a novel phosphor over his blue chip.

The resultant white LED can produce a flashlight that shines for 35 hours, almost 30 hours longer than a standard incandescent flashlight bulb.

Because a typical 60-watt light bulb puts out a lot of electromagnetic energy in the infrared part of the spectrum, which can't be seen but is felt as heat, using white LEDs would reduce the energy needed to power lights bulbs.

By eliminating the heat-producing infrared radiation generated from an incandescent bulb, air conditioning costs would also be reduced, said Nakamura.

Nakamura, who holds 80 Japanese patents and 10 U.S. patents, said he believes material science must precede any progress in the physics of using InGaN materials.

But he expects the material will provide a means of producing white LEDs in volume, eventually leading to their replacing incandescent light sources.