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Transport properties

Transport properties

Let there be light

01 Oct 2007

Brilliant!: Shuji Nakamura and the Revolution in Lighting Technology
Bob Johnstone
2007 Prometheus Books
336pp £13.67/$28.00 hb

On display

Gallium nitride (GaN) is probably the most important new semiconductor material since silicon. It owes this status to the development of bright blue, green and white GaN-based light emitting diodes (LEDs), and these in turn owe their invention to a young Japanese researcher named Shuji Nakamura. Brilliant! tells the story of how Nakamura — who was working in the poorly resourced Nichia Chemical industrial research laboratory in a remote part of Japan — overcame huge odds to develop the white LED. This revolutionary technology may eventually replace all the light bulbs and fluorescent tubes in the world, thus saving huge amounts of energy.

Lighting is one of the biggest underlying causes of greenhouse-gas emissions, causing some 1900 megatonnes of carbon dioxide (CO2) to be emitted by power stations each year. This is three times the total CO2 emissions from aircraft, and is comparable to the total amount of CO2 emitted by cars. It is almost certainly easier to reduce CO2 emissions by having more efficient lighting than by making cars and planes more efficient.

Gallium-nitride white LEDs provide an obvious route to this goal. They should eventually be 10 times more efficient than filament light bulbs, and more than twice as efficient as long fluorescent tubes and compact fluorescent lamps (CFLs). White LEDs also have considerably longer lifetimes than these other technologies, and — unlike fluorescent tubes and lamps — they do not contain toxic mercury.

Perhaps this explains why galliumnitride LEDs made it to market so rapidly. The first prototype bright blue LED was demonstrated by Nakamura in his small laboratory in November 1993. Last year galliumnitride LEDs worth over $4bn were sold worldwide. This is more than the total sales of gallium-arsenide (GaAs) devices in 2006, even though most mobile phones contain a GaAs chip.

Brilliant! is a superb and inspirational book that explains the history of this remarkable technology in four easily readable parts. The story starts with Nakamura’s humble origins in rural Japan and plots the path that led to the first GaN-based LEDs. Nakamura joined Nichia in 1979 and spent the next eight years developing various new products, all of which were commercial failures. In desperation, Nakamura went to the president of Nichia — then Nobuo Ogawa — to explain that he wanted to develop a bright blue LED, and that he needed ¥300m (equivalent to 2% of the company’s sales that year). To Nakamura’s astonishment, Ogawa agreed, and also paid for him to spend a year at the University of Florida learning the semiconductor growth technique of metal organic chemical vapour deposition (MOCVD).

While Nakamura was in the US, however, Nobuo Ogawa retired and his successor, Eiji Ogawa, ordered him to stop work on gallium nitride immediately. However, Nakamura disobeyed this instruction and when he returned to Nichia he continued his work in secret. Against all the odds he produced a prototype blue LED in 1993. White LEDs were realized a few years later with the addition of a yellow phosphor coating, which made the emitted light appear white. The second part of the book details some of the first applications of these LEDs. The seven-storey-high Nasdaq full-colour display in New York’s Times Square, for example, consists of 19 million LEDs and covers almost a quarter of an acre.

Nakamura’s story does not end there. In 1999 Eiji Ogawa established a centre for research on nitrides and appointed Nakamura as the manager, but gave him no staff. Realizing he was being sidelined for his earlier disobedience, Nakamura looked for work elsewhere, and in January 2000 he moved to the University of California at Santa Barbara.

Then, 10 months later, the US LED company Cree hired Nakamura as a part-time consultant. Nichia was furious and promptly sued Cree, citing Nakamura for leaking trade secrets. Nakamura responded by hiring a top lawyer and filed a claim in the Tokyo district court against Nichia in August 2001, asking for compensation of ¥2bn (about £8m) as his share of the sales of Nichia LEDs. In January 2004, the court awarded him a massive ¥20bn (£80m), by far the largest award of its kind ever made by a Japanese court. The book concludes with a section on the ongoing revolution in solid-state lighting.

The book’s author Bob Johnstone is an Australia-based science journalist who has a great talent for explaining physics in simple terms, and — apart from the occasional scientific slip-up — the book’s only major weakness is the explicit exclusion of Europe. As Johnstone writes on page 18: “Europeans should ask themselves why, despite the fact that several of the actors in this drama are European by birth, it is possible to write a book such as this essentially without mentioning Europe. Indeed, it is only a slight exaggeration to say that, from a technological and entrepreneurial point of view regarding LEDs, with the honourable exception of Germany’s Osram Opto, Europe hardly exists.”

I understand where Johnstone is coming from. European governments have totally failed to recognize the potential of gallium-nitride-based LEDs, while the US, China, Japan, Korea and Taiwan all have major national solid-state lighting initiatives that pump large sums of money into the research and development of gallium- nitride-based LEDs. Europe is not the hopeless case that Johnstone portrays, however. The German firm Aixtron is the largest manufacturer of gallium-nitride MOCVD equipment in the world. Europe also owns two of the “big five” LED companies in the world in the shape of Philips and Osram, while the UK has a number of thriving companies designing and manufacturing LED products. Various European and UK universities are performing world-leading research in gallium nitride. Reports of the death of gallium-nitride LEDs in the UK and the rest of Europe are greatly exaggerated and need to be countered.

Despite these criticisms, this is a beautifully written, informative and inspiring book. It is a must-read for all academics and industrialists working in the gallium-nitride field, and all physicists, including potential physicists in schools, would greatly benefit from reading it. It is an ideal book for passing the time on your next train or plane journey (when I read my copy). As a present it would be, how can I put it, brilliant!


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