Blue LED & White LED Lighting
Nakamura's bright blue LED from gallium nitride (Nichia, 1993), built on Akasaki and Amano's p-type GaN (1989), gave white LED light; Nobel Prize in Physics 2014.
Open in the interactive tree →Red LEDs existed from the 1960s, but blue needed gallium nitride, whose crystals were hard to grow and could not be made p-type. Akasaki and Amano in Nagoya made p-type GaN with magnesium and electron-beam treatment and built the first GaN blue LED in 1989; Nakamura at Nichia found a thermal annealing method suited to mass production and by 1993 had a blue LED about 1,000 times brighter than earlier ones. A blue chip with a yellow phosphor gives white light, on sale from autumn 1996. Lighting used about 8% of the world's electricity in 2024, and LEDs now average close to 100 lumens per watt, up to 230 at best, against about 20 for halogen lamps.
Prerequisites
- Solid-State Physics & Bands1931Band-gap theory pointed to gallium nitride as the material for blue.
- Light-Emitting Diode (LED)1962The red LED showed the principle; blue light needed a wider-gap semiconductor.
Unlocks
- Smartphone2007White LEDs backlight the phone screen.