Professor Shuji Nakamura: The LED Story


Last year, the 2014 Nobel Prize in Physics was awarded to Dr Shuji Nakamura, professor of materials at the University of California, Santa Barbara, and two others: Isamu Akasaki and Hiroshi Amano, both from Nagoya University.

CREST | 2 Feb 2015

Last year, the 2014 Nobel Prize in Physics was awarded to Shuji Nakamura, professor of materials at the University of California, Santa Barbara, and two others: Isamu Akasaki and Hiroshi Amano, both from Nagoya University.

The prize was given for the invention of blue light-emitting diodes (LED), which has enabled energy-saving white lighting. According to the Royal Swedish Academy of Sciences, when three of them produced bright blue light beams from their semiconductors in the early 1990s, they triggered a fundamental transformation of lighting technology. Red and green diodes had been around for a long time, but without blue light, white lamps could not be created. Despite considerable efforts, both in the scientific community and in industry, the blue LED had remained a challenge for three decades.

The introduction of blue LED has led to direct applications such as Blu-Ray disc players. However, the most significant impact is the development of white LED. White LED bulbs last roughly 25 times longer than regular light bulbs. Nakamura, who has a degree in electrical engineering from the University of Tokushima, is widely recognised as the pioneer in developing a practical way to manufacture efficient blue LED, which are the basis for white LED.

After graduating from University of Tokushima, Nakamura began working for the Tokushima-based Nichia Corporation. In 1989, when Nakamura began his research on blue LED researchers and companies were using zinc selenide-based materials to try to develop the blue LED.

Nakamura, who was trying to get more scientific articles published so as to earn his PhD, decided to opt for gallium nitride instead because there were so few people working on it. In the process, he discovered gallium nitride (GaN) LED whose blue light, when converted to yellow by a phosphor coating, is the key to white LED lighting.

By 1993, the device was ready for commercialisation. It emitted light with intensity more than 100 times brighter than conventional lighting. After successfully manufacturing blue LED in 1994, Nichia went on to develop commercialised green LED the following year, and laser diodes in 1999.

That same year, Nakamura was promoted to management position but he found such a desk job boring and decided to leave the company to join the faculty at the University of California, Santa Barbara.

In 2007, Nakamura and his colleagues at UCSB’s Solid State Lighting and Energy Center achieved major breakthrough in laser diode development, demonstrating the world’s first non-polar blue-violet laser diodes.

A year later, in 2008, Nakamura, along with fellow UCSB professors Dr. Steven DenBaars and Dr. James Speck, founded Soraa, a developer of solid-state lighting technology built on pure gallium nitride substrates via the GaN on GaN process Typically LED were made of GaN crystals grown onto sapphire or silicon carbide but Soraa uses GaN on GaN to produce more light per area of LED.

Today, Soraa is the only company making commercial GaN-on-GaN LED lighting products.