ABSTRACT
It is believed that group III nitride semiconductors are among the most promising materials for solving global problems and realizing a sustainable society. GaN and related nitride materials have had a major impact on human lives. Their most important application is blue LEDs. Portable games machines and cellular or smart phones are very familiar items, especially to young people. Until the end of the 1990s, all the displays of portable games machines and cellular phones were monochrome. The younger generation can now enjoy full-color portable games such as Pokemon Go because of the emergence of blue LEDs. Today, the applications of blue LEDs are not limited to displays. In combination with phosphors, blue LEDs can act as a white light source and are also used in general lighting. This chapter describes the development of GaN-based blue LEDs from the early 1960s to the 1990s.
