Physics Nobel winners Isamu Akasaki, Hiroshi Amano and Shuji Nakamura

It may be going too far to say this year’s Nobel prize in physics will save the world – but it will certainly make it more efficient.

The prize has gone to three semiconductor physicists who invented the blue LED (light emitting diode). Their invention has transformed the way we light our world, watch movies and store data.

Isamu Akasaki and Hiroshi Amano at Nagoya University in Japan, and Shuji Nakamura at the University of California in Santa Barbara, share the prize of 8 million Swedish kronor (£0.7 million).

LEDs as we know them were invented in the late 1950s, but only came in one colour: red. Green followed later, but although both were fine for indicator lights and digital watches, researchers really wanted a white LED. These are replacing traditional incandescent bulbs, which lose much of their energy as heat.


“Lighting currently consumes 20 per cent of all electricity,” says Colin Humphreys at the University of Cambridge. “Switching to LEDs could save 50 per cent, or over £2 billion in the UK alone.”

Colour addition

The key to producing white light was to make a blue LED and shine its light through a thin layer of yellow-emitting phosphor. This combination of yellow and blue makes white light much more efficiently than incandescent bulbs.

But blue LEDs had stymied researchers until the Nobel trio made their breakthrough in the late 1980s. The reason is to do with the way the devices are made. LEDs are made from multiple layers of semiconductor sandwiched together, one with an excess of electrons and the next with an excess of positively charged holes. Applying a voltage to the device drives the electrons and holes together into the “filling layer”, where they combine to emit light. The colour of this light depends on the semiconductor material. Red LEDs, for example, are made from gallium arsenide crystals.

Researchers realised that gallium nitride with a smattering of indium had the perfect quantum properties to emit blue light. But no one was able to make a semiconductor sandwich with a gallium nitride filling. That’s because the crystal structure of the gallium nitride needs to match that of the surrounding layers to prevent defects from forming that wreck the light-emitting properties.

In 1986, Akasaki and Amano succeeded in finding a match. Their trick was to add an extra layer to the sandwich. They grew their gallium nitride on top of a sapphire covered with a layer of aluminium nitride. Meanwhile Nakamura found his own way to create a gallium nitride crystal by growing a thin layer at low temperatures, then subsequent layers at higher temperatures. Nakamura had to work on his idea in secret after bosses at the Japanese company he worked for, Nichia, stopped his research because of lack of progress. Nakamura later sued Nichia and won more than $7 million compensation.

Blu movies

The trio went on to turn their blue LEDs into blue lasers, found in Blu-ray players. Because the wavelength of blue light is shorter than that of red LEDs, the beam can be focused to a small spot. This lets you cram more information on to a disc and read it out, giving Blu-rays a better picture quality than regular DVDs.

As well as saving money, LED lights can reduce pressure on Earth’s resources. Lights made from LEDs last for 100,000 hours, 10 times longer than fluorescent lamps and 100 times longer than incandescent bulbs. “The electronic circuits that control them give out before the LED,” says Humphreys.

He predicts many more advances to come.

Smart lighting that adapts to its surroundings could reduce energy bills by another 5 per cent. And by changing the phosphor coating on a blue LED it should be possible to produce lighting that mimics sunlight, which plays a key role in the human body clock. “This could be the end of jet lag and could improve the health of shift workers, who have been shown to have a higher risk of cancer.”

Akasaki, Amano and Nakamura will receive their award at the Nobel ceremony in December.