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Premio Nobel de Física 2014: LED Azul

publicado a la‎(s)‎ 7 oct. 2014 7:34 por Web Dep Fisica   [ actualizado el 10 oct. 2014 5:48 ]

In a choice that surprised Nobel watchers, this year's physics prize is going to three Japanese scientists not for a basic discovery, as is typical, but rather for an invention: the blue light-emitting diode (LED). The Nobel committee recognized three researchers as contributing equally to the breakthrough: Isamu Akasaki of Meijo University in Nagoya and of Nagoya University; Hiroshi Amano of Nagoya University; and Shuji Nakamura, now of theUniversity of California, Santa Barbara.

Light emitting diodes appeared in commercial applications in the early 1960s. But even until the early 1990s they only came in such colors as red and green. They were used as indicator lights in electronic devices and in electronic displays and, later, in high center-mount auto brake lights. But without a blue LED there was no way to create the white light needed for general purpose lighting.

The challenge was in the materials. LEDs are semiconductor constructions that rely on an applied voltage to drive electrons and positive carriers called holes through different layers of a crystal sandwich. When electrons and holes come together in the so-called active layer of the sandwich they give off photons--light. The wavelength of the light, and thus the color, depends on the properties of the crystal and the embedded impurities, which are called dopants. For years, major corporations tried to find the right combination of semiconductor materials and dopants to produce blue light, but they failed.

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