Review— Toyoda Gosei's History of R&D on Blue LEDs with Professor Isamu Akasaki

Abstract

Toyoda Gosei (TG) started joint R&D with Prof. Akasaki and Prof. Amano (collectively, the Akasaki Group) in 1986, immediately after the Akasaki Group succeeded in the growth of high-quality GaN single crystals for the first time in the world. Then, the Akasaki Group and TG concluded an entrustment R&D agreement with Japan Science and Technology Agency (JST) in 1987 to promote R&D through the investment of JST. Under these circumstances, the Akasaki Group achieved the growth of high-quality p-type GaN and n-type GaN, believed impossible at that time. These breakthrough technologies were of fundamental importance for developing blue light-emitting diodes (LEDs). Namely, (1) high-quality GaN single crystals, (2) p-type GaN, and (3) n-type GaN were found to be applicable to industrial products. Thanks to the Akasaki Group, TG started the mass production of blue LEDs in 1995. However, at that time, these LEDs were not particularly bright, and no one believed that they would be used in general lighting. In spite of this prediction, the brightness of blue LEDs was improved markedly by industry-based developments, leading to their widespread adoption in many applications.