In a choice that surprised Nobel watchers, this year's physics prize is going to three Japanese scientists not for a basic discovery, as is typical, but rather for an invention: the blue light-emitting diode (LED). The Nobel Committee recognized three researchers as contributing equally to the breakthrough: Isamu Akasaki of Meijo University in Nagoya and Nagoya University; Hiroshi Amano of Nagoya University; and Shuji Nakamura, now of the University of California, Santa Barbara.
Light-emitting diodes appeared in commercial applications in the early 1960s. But even until the early 1990s they only came in such colors as red and green. They were used as indicator lights in electronic devices and in electronic displays and, later, in high center-mount auto brake lights. But without a blue LED there was no way to create the white light needed for general purpose lighting.
The challenge was in the materials. LEDs are semiconductor constructions that rely on an applied voltage to drive electrons and positive carriers called holes through different layers of a crystal sandwich. When electrons and holes come together in the so-called active layer of the sandwich, they give off photons—light. The wavelength of the light, and thus the color, depends on the properties of the crystal and the embedded impurities, which are called dopants. For years, major corporations tried to find the right combination of semiconductor materials and dopants to produce blue light, but they failed.
This trio of Japanese researchers tried working with gallium nitride. Theoretically, gallium nitride had the right stuff to produce blue light, but it was notoriously finicky to work with. “People thought [a blue LED] wouldn’t be achieved during the 20th century,” Akasaki said during a press conference today in Nagoya. “Other researchers gave up, but I didn’t think of doing so, I was doing what I liked,” he said.
Akasaki and Amano, working together at Nagoya University, tried different ways of growing the semiconductor crystal and made the first breakthrough, coaxing faint blue light from a gallium nitride semiconductor in 1986. As they continued improving their blue LED, Nakamura, who then had only a master's degree and was working independently at Nichia Chemical Industries, a small maker of phosphors located in a small town in rural Shikoku, continued to try different ways of growing the needed gallium nitride layers and in 1990 got a device emitting very bright, very blue light.
The breakthroughs initiated a still ongoing revolution in lighting. LED lighting is far more efficient than previous forms of lighting, which involve heating a filament or a gas and wastes most of the input energy. LEDs are now over 50% of the theoretical maximum efficiency. And "it will be hard to find something better" than LEDs, said Per Delsing, chair of the Nobel Committee for Physics, in an interview after today’s press conference in Sweden. He added that LEDs also avoid the use of mercury, a toxic material common in fluorescent lights. The committee emphasized the usefulness of the invention, saying it is something that touches virtually everyone relying on illumination. "I think Alfred Nobel would be really happy about this prize," Delsing said.
The switchover from incandescent bulbs to more efficient lighting such as LEDs has greatly reduced the amount of energy used in lighting worldwide, with obvious environmental benefits. But the Nobel Committee also pointed out that LEDs’ efficiency means that they can be run on low-cost solar power and simple batteries, bringing light to the 1.5 billion people who are not connected to energy grids. “With 20% of the world’s electricity used for lighting, it’s been calculated that optimal use of LED lighting could reduce this to four per cent. Akasaki, Amano and Nakamura’s research has made this possible and this prize recognises this contribution,” said Frances Saunders, president of the U.K. Institute of Physics, in a statement. “This is physics research that is having a direct impact on the grandest of scales, helping protect our environment, as well as turning up in our everyday electronic gadgets.”
Japanese politicians heaped praise on the trio on evening newscasts. But Nakamura may have mixed feelings about his homeland. He had a falling out with Nichia Chemical and sued the company, eventually winning a share of the profits it earned from his invention. He also decided to move to the United States after failing to find an academic position in Japan. During a January 2005 press conference after the settlement of his suit, Nakamura blasted Japan's courts, educational system, and treatment of researchers. “Basically, Japanese society doesn't value the contributions of individuals. In Japan, the world is centered on big companies," he said. He is now an American citizen.
Science profiled Nakamura in a 1997 feature: Staying Off Beaten Track Puts LED Researcher a Step Ahead.