How it began
Isamu Akasaki worked with Hiroshi Amano, then a doctoral student, at Nagoya University. Shuji Nakamura was employed at Nichia Chemicals, a small company in Tokushima on the island of Shikoku. In 1986 Akasaki and Amano were the first to create a high-quality gallium nitride crystal, by placing a layer of aluminum nitride on a sapphire substrate and growing the gallium nitride on top. Two years later Nakamura also made high-quality gallium nitride, by first growing a thin layer at low temperature and later layers at a higher temperature.
How it works
The diode needs layers of gallium nitride of two types. Akasaki and Amano noticed by chance that their material glowed more intensely when studied in a scanning electron microscope. Nakamura explained why: the electron beam removed hydrogen that was preventing the p-type layer from forming. In 1992 he made a working p-type layer by a simpler and cheaper method, heating the material. Both groups then built increasingly complex structures from gallium nitride alloyed with aluminum or indium.
Who pushed back
Gallium nitride was the choice of all three, although others had failed with it before them. The difficulties lay in growing high-quality crystals. Nakamura chose gallium nitride over zinc selenide, which others considered a more promising material. The Nobel account stresses that the laureates succeeded by challenging convention where others had given up.
What lasted
The Nobel Foundation describes the blue LED as a new energy-efficient and environment-friendly light source. Akasaki with Amano, and Nakamura separately, also invented a blue laser, in which a blue LED the size of a grain of sand is a crucial component. The three shared the 2014 Nobel Prize in Physics for the invention of efficient blue light-emitting diodes.
