16) Pioneering the Industrialization of Blue LED becomes a Medal
Picture:A blue LED on a gallium nitride epitaxial layer grown on a sapphire
substrate with electrodes
attached to it and made to shine with a probe
Akasaki being the pioneer of blue LED "research",
then it is Nichia Corporation that put a leading pillar in its "industrialization".
The company is a major domestic company of phosphor materials with the headquarter
in Anan City, Tokushima Prefecture, and because it was involved in the purification
of metallic gallium, it was suitable for tackling on research on gallium nitride
semiconductors.
In the 1980s, the company had been working on the production of gallium nitride
thin films, etc. by introducing organometallic vapor phase epitaxy equipment,
and they succeeded in the fabrication of high-quality gallium nitride crystal
film in September 1990, and a low temperature gallium nitride film fabrication
which was optimum as a buffer film in March 1991. The latter advanced the
development of an aluminum nitride buffer layer by Akasaki one step further
and it became a powerful means of its industrialization.
They also found that gallium nitride semiconductors can be converted to P
type by normal annealing, making its mass production easy.
The blue LED commercialized in November 1994 by Nichia Corporation was realized
for the first time by using, in addition to the above-mentioned technologies,
an indium gallium nitride film (double heterostructure with aluminum gallium
nitride film) for the light emitting layer.
Its brightness is 100 times brighter than a conventional one and it was good
enough for practical use.
It was the moment when the world's first blue LED was born.
The photograph is of a gallium nitride epitaxial layer grown on a sapphire
substrate with electrodes attached to it and made to shine with a prober (at
the time of 1994).
(By courtesy of Nichia Corporation)