Showa Denko Launches GaN-based Near Ultraviolet and Green LED Chips

Showa Denko K.K. (SDK) has launched its proprietary gallium-nitride-based near ultraviolet and green light-emitting diode (LED) chips for use in general white lighting and backlighting of large LCD screens, respectively.

Those LED chips with high power and brightness will be shown at Inchem Tokyo 2005 international exhibition to be held at Tokyo Big Sight from November 15 through 18.

The GaN-based near ultraviolet LED will be combined with phosphor to provide white lighting. So far, blue LEDs and yellow phosphor are combined for white backlighting of LCD screens in mobile phones. However, the existing white lighting is not sufficient for general lighting applications due to low levels of its red/green components and color rendering property.

When the newly developed near ultraviolet LED is combined with the mixture of phosphor of the three primary colors (red/green/blue), it achieves high levels of color rendering property, enabling its use in general lighting. Since the general lighting market in Japan is as large as approximately ¥1 trillion, LED-based white lighting has a huge market potential.

Using its already commercialized GaN-based blue LED technology as the basis, SDK has developed the near ultraviolet LED with a flip chip structure1), achieving a high power of 14 mW in the wavelengths of around 400nm. The power level is sufficient for use in general lighting as combined with highly efficient phosphor. This new LED also uses the ultraviolet LED epitaxial wafer technology developed as part of the high-efficiency electro-optic conversion compound semiconductor development program (the Light for the 21st Century project) of the New Energy and Industrial Technology Development Organization (NEDO).

SDK’s newly developed GaN-based green LED ensures higher brightness and reliability compared with existing products on the market. At present, green LEDs are used in traffic lights and various displays. They are also used in combination with blue and red LEDs to provide full-color large displays.

In addition, there is an increasing need for use as backlighting of LCD TV screens with high levels of color reproduction. The world’s LCD TV production--now14 million units a year--is expected to grow further. Demand for LEDs for backlighting will grow rapidly as they replace cold-cathode tubes.

SDK has developed green LEDs with a face-up structure2) far brighter than existing products on the market: 6.5 mW (400mcd) in the wavelengths of 505nm (bluish green) and 6 mW (500mcd) in the wavelengths of 525nm. SDK will also produce pure-green LEDs in the wavelengths of 555nm that are not so far available on the market. These new products have been made possible with the use of new crystallization conditions, newly developed electrodes and the above-mentioned proprietary blue LED technology.

SDK has established a wide-ranging product line of GaN-based LED chips covering the wavelengths from 390nm (near ultraviolet) to 555nm (pure green), in addition to the already commercialized aluminum-gallium-indium-phosphide (AlGaInP) red to yellow-green LED. Thus SDK now offers high-brightness LEDs for all colors from the infrared LED to high-power near ultraviolet LED.

The production of the two new types of LEDs started this month at SDK’s Chiba Plant where blue LED chips are also being produced. SDK is also working to increase the brightness of blue LED, and has recently started marketing 12mW LEDs with a face-up structure. SDK’s Chiba Plant has the capacity to produce 30 million units a month of GaN-based LED chips. The company is planning to expand the production capacity to meet a growing demand while continuing R&D efforts to develop new LEDs with more diverse colors and higher performance.

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