Twin colour LED to enable cheap lighting

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A semiconductor device capable of emitting two distinct colours has been created by researchers from Arizona State University. The development is believed to bring the possibility of using LEDs for cheap and efficient lighting.

Lead author of the study, Professor Cun-Zheng Ning, said: "Semiconductors are traditionally 'grown' together layer by layer. Since different semiconductor crystals typically have different lattice constants, layer by layer growth of different semiconductors will cause defects, stress and, ultimately, bad crystals, killing light emission properties." He says this is why current LEDs cannot have different semiconductors within them to generate red, green and blue colours for lighting. The proof of concept device uses nanoscale materials and processes to emit green and red light separated by a wavelength of 97nm and with better energy efficiency. According to the researchers, recent developments in the field of nanotechnology mean that structures can be grown to tolerate much larger mismatches of lattice structures, and thus allow very different semiconductors to grow together without too many defects. "In addition to being used for solid state lighting and full colour displays, such technology can also be used as light sources for fluorescence, bio and chemical detection," Prof Ning added.