The 2009 Laureates / Advanced Technology Category / Electronics

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Isamu Akasaki

Japan / January 30, 1929
Semiconductor Scientist
University Professor, Nagoya University ; Professor, Meijo University

"Pioneering Work on Gallium Nitride p-n Junctions and Related Contributions to the Development of Blue Light Emitting Devices"
Dr. Akasaki conducted persistent research on gallium nitride (GaN) for many years toward the realization of blue LEDs. His efforts culminated in the pioneering realization of GaN-based p-n junctions, which were once believed to be practically impossible. This achievement served as the first firm step toward the eventual commercialization of blue LEDs. To this day, Dr. Akasaki has consistently played a leading role in a series of significant research endeavors. His contributions to them certainly deserve the highest recognition the world over.

CITATION

Pioneering Work on Gallium Nitride p-n Junctions and Related Contributions to the Development of Blue Light Emitting Devices

Dr. Isamu Akasaki conducted persistently intensive research on gallium nitride (GaN) for many years toward the realization of blue light-emitting diodes (LEDs). His efforts culminated in the pioneering realization of GaN-based p-n junctions, which were believed to be practically impossible. This achievement has stimulated research activities on blue LEDs in Japan and elsewhere, and served as the first firm step toward their eventual commercialization. To this day, Dr. Akasaki has consistently played a leading role in a series of research endeavors. His contributions to the birth and progress of GaN-based blue LEDs deserve the highest recognition the world over.

With their high efficiency and long life, LEDs can be used in a wide range of applications. For this reason, R&D efforts in this area started early on, resulting in the development of red and green LEDs. With the addition of blue LEDs, the three primary colors of light would be complete, raising expectations that LEDs could be used to realize full-color displays and white illumination. It was hoped that the realization of blue laser diodes would allow the dramatic increase in the recording density of optical discs. These high expectations led to several attempts to realize blue LEDs around 1970, with researchers conducting intensive research on the promising material of GaN. However, it was quite difficult to prepare high-quality GaN and control their electrical properties. One could form n-type GaN, but p-type materials indispensable for LEDs remained out of reach. As a result, most researchers gave up on their attempts to develop blue LEDs and withdrew from such attempts by the end of the 1970s.

Dr. Akasaki, however, did not. He resolutely continued his research and went on to find in 1985 that the crystalline quality of GaN can be remarkably enhanced by forming a buffer layer at low temperatures on sapphire substrate before growing GaN crystals. With the cooperation of Dr. Hiroshi Amano, Dr. Akasaki made groundbreaking discoveries in 1989. His work demonstrated that p-type GaN can be formed by doping magnesium atoms into high quality GaN and irradiating them with electron beams. Using this method, he and his group realized the world's first GaN-based p-n junctions and demonstrated their operation as blue LEDs.

These achievements shed new light on the potential of GaN as a material for blue LEDs and restimulated GaN researches. They induced intense R&D activities to establish the technological basis for the commercialization of blue LEDs. These efforts bore fruit when blue LEDs went on the market in 1993. This device is widely used in displays and lighting. Later, blue laser diodes were commercialized, and played a pivotal role in raising the recording density of optical discs. All through these developments, Dr. Akasaki has played leading roles by his pioneering work for the realization of blue light emitting devices and by his persistent research for the advancement of this field.

For these reasons, the Inamori Foundation is pleased to present the 2009 Kyoto Prize in Advanced Technology to Dr. Isamu Akasaki.

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