|
06/16/2006 - The 2006 Millennium Technology Prize has been awarded to Shuji Nakamura. Professor Nakamura has developed a new, revolutionary source of light – bright-blue, green and white LEDs and a blue laser. The technology is used in several applications which improve the quality of human life. The world’s largest technology prize, now being awarded by Finland’s Millennium Prize Foundation for the second time, has a value of one million euros.  Professor Shuji Nakamura’s innovation has launched a totally-new sector in light-producing semiconductor research and development. His development also made possible the widescale industrial production of efficient, energy-saving LED lights and created the conditions for applications that improve the quality of human life. LED lights have extremely long lives and consume far less energy than normal incandescent lamps. In industrialised countries, the opportunities for energy-saving LED lights are significant – it has been calculated that in the USA alone, replacing current lighting systems with systems based on LED lights could achieve very significant reductions in energy consumption in future decades. The new light sources are also well suited to operation with solar power systems and are therefore ideal for use in remote areas of developing countries. One of the most significant future applications for Shuji Nakamura’s invention is the sterilisation of drinking water, since the use of ultraviolet LEDs makes the water purification process both cheaper and more efficient. Systems based on this technology are expected to improve the lives and health of tens of millions of people. Data storage and transfer using light generated by blue lasers brings significant benefits, for example, the amount of data stored on CDs or DVDs can be increased by some five times compared to current techniques. ”Shuji Nakamura is a splendid example of perseverance and dedicated research work, and of making a major breakthrough. He has worked with great determination for decades, and even severe setbacks have not prevented him from achieving something that other workers in the field regarded as almost impossible: using a reactor system of his own design to develop a solid material, in this case gallium nitride, into a powerful light source producing blue, green and white light, and also creating a blue laser. The lighting applications now made possible by his achievement can be compared with Thomas Edison’s invention of the incandescent lamp. In the course of time, energy-efficient light sources based on Shuji Nakamura’s innovation will undoubtedly become predominant,” says Pekka Tarjanne, Chairman of the International Selection Committee. Professor Shuji Nakamura was born in Japan in 1954. He has worked in the USA at the University of California, Santa Barbara since 2000, and his research work into new sources of light continues. In accordance with the rules of the Millennium Prize Foundation, a proposal concerning the winner of the Millennium Technology Prize is made to the Board of the foundation by the eight-member International Selection Committee, and the final decision on the prize winner is made by the Board. Shuji Nakamura will receive the Millennium Technology prize at a ceremony to be held in Helsinki on the 8th of September. The prize is awarded every second year for an innovation that improves the quality of human life and well-being. Millennium Technology Prize winner Professor Shuji Nakamura and his work Professor Shuji Nakamura is one of the most significant inventors of our time. In 1993, he stunned the optoelectronic community with the announcement of very-bright blue GaN-based light emitting diodes (LEDs). In rapid succession, he then announced a green GaN-based LED, a blue laser diode, and a white LED. All these developments were things that other researchers in the semiconductor field had spent decades trying to do. Professor Nakamura’s story is unique. Born in 1954 in Japan on the island called Shikoku, he received his master’s degree in 1979 at the University of Tokushima. He started his scientific and technological career outside mainstream Japanese technology, working as an engineer at Nichia Chemical, a small phosphor company in the countryside.  At Nichia Chemical’s laboratory, with only a limited budget and modest support from company management, Nakamura developed a highly-original two-flow growth system which led to the successful epitaxial growth of gallium nitride (GaN) in 1989. Three years later, he managed to produce p-type GaN, a fundamental breakthrough in III-V nitride research. Since the beginning of research into GaN almost three decades earlier, no-one had been able to create this particular compound.
In 1993, to universal surprise, Nakamura demonstrated bright-blue LEDs. Two years later he announced a green GaN-based LED, a blue laser diode, and a white LED. Professor Nakamura patented his innovations. Innovative MOCVD technique
Nakamura's road to his innovations began with his development of a new technique for Metal-Organic Chemical Vapour Deposition (MOCVD). In the conventional MOCVD technique, semiconductors are manufactured by passing reactant gases over a substrate. Nakamura pioneered a method whereby the gases flow in two directions instead of just one, improving material quality. This novel MOCVD technique first enabled him to make a bright-blue LED, which led to a white LED and then to a blue laser.
Semiconductors are crystalline materials in which electrons moving from higher to lower energy levels in the structure emit photons of light whose frequency (i.e. colour) is determined by the size of the gap between the energy levels. Optoelectronic engineers call this difference in energy levels the "band gap." As the gap that an electron has to traverse to emit a blue photon is greater than that for any other visible colour, the electron must have a higher initial level of energy to be able to give off the higher frequency blue photon.
Blue LEDs – a breakthrough in semiconductor research
The usual semiconductor picture is rather too simplified for an understanding of Nakamura's breakthrough in making a blue LED. Blue LEDs actually consist of a two-sided crystal in which the "sides" represent an n-type and a p-type semiconductor. The N-type conducts electrons, and the p-type conducts holes, which are an absence of electrons. The electrons flow in one direction, the holes flow in the opposite direction. The location in the crystal where electrons and holes fall into, or are injected into, is called the junction, and that is where the photons - particles of light - are emitted.
 Nakamura discovered how to grow semiconductor crystals so that they have the structure required to create "quantum wells" for electrons at the junction. One of the key techniques for creating these wells was the addition of indium to the GaN crystal. Without the indium, GaN produces a higher frequency of ultraviolet light which is not in the visible spectrum. Adding indium results in a lowering of the frequency of the emitted photons to visible blue, but the indium also creates the required quantum well effect, so that electrons that fall into passing holes first fall into the well and gain additional mass before being injected into the holes. This adding of mass in the well creates a more vigorous injection - and therefore more light.
Green LED – additional spectrum colours
With the addition of a fraction more indium, a blue LED can be turned into a green LED. Before Nakamura’s innovation, the green in full-colour displays was a phosphorescent yellow. His blue LED technology makes the greens even in large full-panel LED displays really green.
White LED – revolutionizing illumination
Professor Nakamura's next step was to add a novel phosphor to his blue chip to obtain white light.
Domestic 60-watt light bulbs emit a lot of electromagnetic energy in the infrared section of the spectrum. While this radiation cannot be seen, it can be felt as heat. The essence of this innovation is to eventually replace the world’s inefficient incandescent light bulbs with white LEDs to reduce the amount of energy required to produce light. An additional benefit will then be accomplished through a significant reduction in air-conditioning costs. Not only do white LEDs produce light energy more efficiently, they have a working life of orders of magnitude longer than conventional light bulbs. Blue lasers – multiplying information storage capacity
In the mid-1990s when Nakamura was using his blue LEDs to make white LEDs, he was also adapting his blue LED technology to make a blue laser. In blue LEDs, the photons emitted fall in a range of similar frequencies – resulting in the blue colour. In lasers, the frequency of the photons must all be the same. To amplify a single light frequency in a crystal, Nakamura worked out how to etch a highly-polished mirror on each side of the crystal so that the light bouncing back and forth between the two mirrors resonated at the required frequency. His breakthrough was not only to form the mirrors on each side of the crystal, but also to make it possible for the crystal to accept the strong electrical currents necessary to create high-frequency blue laser light.
Blue lasers are a substitute for the infrared lasers used in compact-disc (CD) players. Using them means that the information storage capacity of a CD is increased five times. Blue lasers mean not only more data on CDs, but also on DVDs. Next-generation high-definition DVDs employing blue lasers are about to reach the market. Professor Nakamura’s work continues
All of Nakamura's impressive innovations depend on the use of GaN semiconductors. Current research developments based on this material appear to herald a revolution in which gallium nitride will replace gallium arsenide as the semiconductor material of choice. Although gallium is common to both materials, it is the move from its combination with arsenic to a combination with nitrogen that is key. Unlike the former, the latter is an environmentally-friendly element.
In 1994, Nakamura received his doctorate in engineering at the University of Tokushima. Five years later he left Japan and joining the faculty of the University of California, Santa Barbara (UCSB). At UCSB he has built up a significant research programme in new areas of nitride research. Professor Nakamura’s current research interests are the growing of optoelectronic materials and the fabrication of novel semiconductor devices. In more specific terms, he is working on new devices including full-colour LEDs, an efficient white-LED light bulb, laser diodes and high-power, microwave communication devices.
Nakamura’s inventions in both GaN materials and associated devices are having an extensive impact in many areas that improve human quality of life and promote sustainable development. Applications that have already been developed by using Nakamura’s technology can reduce energy consumption, bring reading lights to the outermost areas of developing countries, sterilise water in a more efficient and cheaper way, and store data in much smaller spaces. New applications for the technology and ways of using it to improve human quality of life are being developed all the time.
The Millennium Technology Prize
The Millennium Technology Prize is awarded every second year for a technological innovation that significantly improves the quality of human life. The intention is to encourage human-centred technological development by rewarding both innovations and research and development work that are aimed at improving quality of life and sustainable development. Finnish organisations, industry and the Finnish state founded and fund the prize in partnership. The first Millennium Technology Prize was awarded to Sir Tim Berners-Lee in June 2004 for his invention of the World Wide Web.
The Millennium Prize Foundation
www.millenniumprize.fi |
