Tag: Inventions

Chemical Industries Company

In the early 80s, GV Saparin and M. Chukichev at Moscow State University. MV University found that after of the electron beam pattern GN, doped with Zn, is striking a phosphor. But the reason for the bright light – the activation of Zn acceptors under the influence of the electron beam – then could not understand. His first blue LED Nakamura made the March 28, 1991. He left the LED on, when he left home, and after a sleepless night, arriving early in the morning to the lab, saw the LED still shines. Although the radiation was not very bright, it was a victory. Two and a half years later, after numerous improvements Nakamura produced diodes emitting emitting mkkd 1000, and another six months, the company announced the release of 2000’s mkkd diode that emits so bright that it hurts to watch.

November 29, 1993 Nichia Chemical Industries Company announced that it completed the development of blue LEDs based on GN and plans to begin mass production of them. Few, even in Japan had ever heard of Nichia, and few people paid attention to a couple of articles published shortly before the S. Nakamura. The first commercial blue LED was made by Nakamura in early 1994 based on heterostructures InGN / AlGN active layer of InGN, doped with Zn. Output power was 3 mW at a forward current of 20 mA with a quantum yield of 5.4% at a wavelength of 450 nm. Shortly thereafter, by increasing the concentration of In in the active layer was fabricated green LED that emits light with a force 2 cd. It consists of 3-nm active layer of InGN, concluded between the layers of p-AlGN and n-GN, grown on sapphire. Such a thin layer of InGN minimizes the influence of mismatch of lattices: the elastic strain in the layer can be removed without the formation of dislocations, and quality the crystal is high.

In 1995, with even less InGN layer thickness and higher content of In was increased by up to 10 light candles at a wavelength of 520 nm and quantum efficiency of up to 6.3%, the measured lifetime of LEDs was 50 000 h, and on theoretical estimates – more than 106 hours ( 150 years). Nakamura patented technology milestones, and the end of 1997 the firm Nichia has produced 10 … 20 million blue and green LEDs per month. Cases of rapidly sped up, revenues have grown from 20 billion yen in 1993 to 116 billion yen in 2002 and the order of 180 billion yen in 2003. To date, the external quantum efficiency of LED radiation, based on GN and its solid solutions (InGN, AlGN) reached values of 29/15/12%, respectively, for purple / blue / green LEDs, their light output has reached values 30 … 50 lm / watt. Internal quantum efficiency for “good” crystals with a powerful heatsink is almost 100% record external quantum yield for red LEDs are 55% and 35% for blue. External quantum efficiency of emission of yellow and red LEDs based on AlInGP solid solutions reached values 25 … 55%, respectively, and the light output has reached 100 lm / W, ie caught up with luminous best of modern fluorescent lamps.