2014 Nobel Prize in Physics

Isamu Akasaki, Hiroshi Amano and Shuji Nakamura share the physics Nobel for the invention of efficient blue light–emitting diodes, which has enabled bright and energy-saving white light sources.

“This year’s prize is about light.” Royal Swedish Academy of Sciences Permanent Secretary Staffan Normark.

“The Royal Swedish Academy of Sciences has decided to award the 2014 Nobel Prize in Physics to Professor Isamu Akasaki at Meijo University, Nagoya, and Nagoya University, Japan; Professor Hiroshi Amano at Nagoya University, Japan; and Professor Shuji Nakamura at University of California, Santa Barbara, for the invention of efficient blue light–emitting diodes which has enabled bright and energy-saving white light sources. Professor Per Delsing will now give us a short summary.”

“Red and green LEDs have been around for many years, but the blue was really missing. This lamp contains three LEDs: one red, one green and one blue. If you combine these colors you get white light. This is something that Isaac Newton showed already in 1671. Thanks to the blue LED, we can now get white light sources which have very high energy efficiency and very long lifetime. This LED technology is now replacing older technologies. In fact, many of you carry this technology in your pocket. The flashlight and also the screen of modern smartphones uses LED technology.”

—Steve Mirsky

Source: SCIENTIFIC AMERICAN

The 2014 Nobel prizes: Physics: Blue's brothers

This year’s prize is awarded for work that will ultimately light up the world

THE Nobel prizes were instituted as a means to reward individuals or organisations who, as Alfred Nobel's will had it, "have conferred the greatest benefit on mankind". Often in the field of physics, the benefit is a measure of understanding of the very small or the very distant: a light shone into the vast darkness of our ignorance about how the universe is composed, and how it works. This year, by contrast, the physics prize has been awarded for an actual light. But it is a light that has already conferred great benefit on mankind, and promises yet more. Japanese researchers Isamu Akasaki of Meijo University, Hiroshi Amano of Nagoya University, and Shuji Nakamura of the University of California, Santa Barbara shared in cracking the problem of making diodes that give off blue light.

The light and the heat of fire gave way to the incandescent bulb in the early 19th century, but such bulbs still squander a great deal of electrical energy as heat. A light-emitting diode, first posited in the 1920s, accomplishes the trick of converting electrical energy with almost perfect efficiency into light. It pairs semiconductor materials that create an imbalance of electrons and their counterparts, called holes. When the twain meet, out comes a discrete burst of light.

However, LEDs tend to make light in narrow bands of colour, dictated by the properties of the semiconductor. Red LEDs proved relatively easy to manufacture in the early 1960s, but orchestrating the dance of electrons and holes to elicit green light took until the end of that decade. A blue LED required a material that hadn't been tamed for industrial use. That took until the early 1990s, when Drs Akasaki, Amano and Nakamura figured out how to make pristine films of the semiconductor gallium nitride, with just the right recipe of impurities that created electron-hole pairs suitable for a blue hue.

It would now be hard to enumerate all of the applications that make use of blue LEDs, principally because they are joined with their green and red brethren to make the light to which people are most accustomed: white. LED-based lighting is finding its way into more and more global markets as it becomes cheaper; already it is in the flash of cameras and smartphones. But blue light has made its own way as well. Blue diodes lie at the heart of DVD and the aptly named Blu-Ray players. By using the same approach, slightly more energetic ultraviolet light can be made—a boon for sterilising surfaces and drinking water using little energy. Communications and computing seem inexorably headed to a future that makes more use of light's properties, and blue light's short wavelength is best for ever-smaller technologies. As the members of the Sweden's Royal Academy of Science put it during their press conference, this year's award is more an "invention" prize than a "discovery" prize. But it is an invention, they said, that would have made Alfred Nobel happy.

Source: The Economist

Isamu Akasaki, Hiroshi Amano and Shuji Nakamura win 2014 Nobel Prize for Physics

The 2014 Nobel Prize for Physics has been awarded to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for their development of blue LEDs. The prize is worth SEK 8m (£690,000) and will be shared by the three winners who will receive their medals at a ceremony in Stockholm on 10 December.

Akasaki is a Japanese citizen and works at Meijo University and Nagoya University. Amano is a Japanese citizen and works at Nagoya University. Nakamura is a US citizen and works at University of California, Santa Barbara.

The prize citation honours the trio for "the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources". The now ubiquitous LEDs are used in a wide arrange of applications from televisions to sterilizers and do not contain toxic mercury that is found in fluorescent lamps.

Three-colour blues

A source of white light needs LEDs that deliver red, green and blue light. The first red LED was created in the 1950s and researchers then managed to create devices that emitted light at shorter wavelengths, reaching green by the 1960s. However, researchers struggled to create blue light.

In the 1980s Akasaki and Amano working at Nagoya University and Nakamura working at the Nichia Corporation focussed on the compound semiconductor gallium nitride (GaN), which could be ideal for creating blue LEDs because it had a large band-gap energy corresponding to ultraviolet light.

There were many challenges, however, in making useable LEDs based on GaN. One major problem was how to create high-quality crystals of GaN with good optical properties. This was solved independently in the late 1980s and early 1990s by Akasaki and Amano and also by Nakamura. Both teams used metalorganic vapour phase epitaxy (MOVPE) techniques to deposit thin films of high-quality GaN crystals onto substrates.

Doping discovery

Another seemingly insurmountable challenge facing the researchers was how to dope the GaN so it is a p-type semiconductor, which is crucial for creating an LED. Akasaki and Amano noticed that when GaN doped with zinc is placed in an electron microscope, it gives off much more light. This suggested that electron irradiation improved the p-doping – an effect that was later explained by Nakamura.

The next step for both teams was to use their high-quality, p-doped GaN along with other GaN-based semiconductors in multilayer "heterojunction" structures. Nakamura was then able to create the first high-brightness blue LED in 1993.

Praising the laureates, the chairman of the Nobel committee for physics Per Delsing said "A lot of big companies tried to [develop blue LEDs] and they failed, but these guys persisted and eventually they succeeded."

Today, GaN-based LEDs are used in back-illuminated liquid-crystal displays in devices ranging from mobile phones to TV screens. LEDs emitting blue and ultraviolet (UV) light have also been used in DVDs, where the shorter wavelength of the light allows higher data-storage densities. Looking into the future, UV-emitting LEDs could be used to create basic yet effective water-purification systems, because UV light can destroy micro-organisms.

Invention or discovery?

Over the past 10 years there have been three other physics Nobel prizes awarded for work with significant commercial potential: giant magnetoresistance in 2007; fibre optics and charged-coupled devices in 2009; and graphene in 2010. While most prizes are associated with more esoteric discoveries, like the Higgs boson, Alfred Nobel decreed in his will that the prize could also be given for an important invention in physics.

"Alfred Nobel would be very happy about this prize," says Delsing. "[The blue LED] is really something the will benefit most people."

David Gross from the Kavli Institute for Theoretical Physics at University of California, Santa Barbara, who shared the 2004 Nobel prize for his work on asymptotic freedom, is happy that in recent years both pure and applied research are being recognized. After addressing a meeting in Trieste to mark the 50th anniversary of the International Centre for Theoretical Physics, where he had stressed the importance of blue-sky research, Gross told Physics World that "Every five or six years the prize is awarded to an invention that has conferred a great benefit to humankind, such as the transistor, the laser and fibre optics. I think the existing ratio is just about right."

Akasaki was born in Chiran, Japan, in 1929. He graduated from Kyoto University in 1952 and received his PhD in 1964 from Nagoya University.

Amano was born in Hamamatsu, Japan, in 1960. He received his PhD in 1989 from Nagoya University.

Nakamura was born in Ikata, Japan, in 1954. He graduated from the University of Tokushima in 1977 with a degree in electronic engineering and obtained a Master's degree in the same subject two years later. He then joined the Nichia Corporation, a small company located in Tokushima on the island of Shikoku. Nakamura was awarded a PhD in 1994 from University of Tokushima.

About the author
Hamish Johnston is editor of physicsworld.com

Source: physicsworld.com