Tuesday, October 14, 2014

The Nobel Prize in Physics 2014: Blue LEDs opened a new world in light.



Isamu Akasaki, 85, left, Hiroshi Amano, 54, centre, and Shuji Nakamura, 60, have won the 2014 Nobel Prize in physics for the invention of blue light-emitting diodes. (Kyodo News/AP)



The Nobel Prize in Physics 2014: Blue LEDs opened a new world in light.
The breakthrough of blue LEDs was so significant in changing lighting technology that the scientists behind it were chosen as this year's recipients for the Nobel Prize in physics.
     Isamu Akasaki, professor at Meijo University, Hiroshi Amano, professor at Nagoya University, and Shuji Nakamura, professor at University of California, Santa Barbara, were recognized for their work in this field.
     "It was a shining blue, and I was so excited that my hands trembled," Akasaki said of the experiment conducted roughly 25 years ago in which a blue light-emitting diode glowed for the first time.
     Back then, red and green LEDs already existed. The missing primary color needed to create white light was blue, and scientists around the world raced to develop the blue LED. At the time, three materials were seen as promising: gallium nitride, silicon carbide and zinc selenide.
     Gallium nitride was considered difficult to handle given its hardness and a melting point exceeding 2,500 C. Creating a blue LED requires growing high-quality crystals, but this was a challenge using the technologies at the time. Researchers around the world stopped studying gallium nitride.
     But Akasaki, while working at the company now known as Panasonic, stuck with gallium nitride despite objections from those around him. He quit the company and became a professor at Nagoya University, and worked with Amano at the school on developing crystals.
     The two men kept conducting experiments, sleeping at the laboratory. They thought of a technique of spraying low-temperature aluminum and then layering gallium nitride on top to create crystals. But they could not find the optimum conditions, so they pressed on by trial and error.
     One day, their electric furnace had trouble heating up. But they conducted their experiments anyway and found that high-quality crystals had formed. Later, after adding magnesium, they created gallium nitride crystals essential for the LEDs for the first time in the world.
     Meanwhile, Nakamura opened the way for mass production of blue LEDs using gallium nitride. Based on crystal production equipment seen at academic conferences, he invented a two-flow metal organic chemical vapor deposition technique and announced the results of his research in 1991. This underpinned the creation of new industries, including energy-saving, long-lasting lighting and displays.

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