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SDK Develops Four-Element LEDs with Exceptional Brightness

December 8, 2003

Showa Denko K.K. (SDK) has developed aluminum indium gallium phosphide (AlInGaP) light-emitting diode three times as bright as existing ones. The new product, developed at SDK’s Chichibu Plant, features a flip chip structure and is expected to fulfill a growing demand for use in outdoor displays, illumination, mobile phones, traffic light and automotive devices.

SDK’s proprietary flip chip technology has enabled production of LEDs with transparent substrate and a special electrode structure. This technology has obviated the use of wire bonding in the assembly process, resulting in smaller and thinner packaging. The newly developed LEDs emit red and orange light with exceptional levels of brightness compared with existing products on the market.

SDK is planning to start commercial production of the product, while further increasing the brightness and diversifying the product lines. SDK expects to sell ¥3 billion of AlInGaP LEDs with exceptional brightness in 2005.

AlInGaP LEDs have increasingly been used in recent years as they emit bright light in the wavelengths from red to yellow-green. Efforts are being made to further increase their brightness. They are also used in combination with indium gallium nitride (InGaN) LEDs that emit light in the wavelengths from blue to green.

Applications of AlInGaP LEDs, now centering on outdoor displays and car interior trim, are expected to broaden to include illumination, traffic light, and car exterior trim. In particular, the combination of AlInGaP LED with InGaN LED having exceptional brightness will find wide applications in the area of illumination.

Thus, demand for AlInGaP LEDs is expected to continue to grow at a yearly rate of around 20%. SDK has been supplying differentiated AlInGaP LEDs with the aim of participating in the growing market for high-brightness LEDs.

SDK’s compound semiconductor business center on various epitaxial wafers. Specifically, SDK provides gallium phosphide (GaP), aluminum gallium arsenide (AlGaAs) and AlInGaP epitaxial wafers and chips for LEDs.
The Company has a leading share in the world’s market for indium phosphide (InP) epitaxial wafers for optical fiber communications equipment.It is also expanding into the area of AlInGaP and AlGaAs epitaxial wafers for DVD and CD laser diodes.

In the ongoing medium-term consolidated business plan called the “Sprout Project,” SDK classifies the compound semiconductor operation as one the “strategic growth businesses,” allocating a substantial portion of its resources into the operation.

[Reference]

1. SDK’s compound semiconductor portfolio

  • (a)LED materials (epitaxial wafers and chips)
    GaP (yellow-green); AlGaAs (red, infrared); AlInGaP (red to yellow-green)
  • (b)Epitaxial wafers for optical pickups
    AlInGaP (red) for DVD; AlGaAs (infrared) for CD
  • (c)Mirror wafers and epitaxial wafers for optical fiber communications equipment
    InP
  • (d)Mirror wafers for mobile communications equipment
    GaAs

2.Terminology

  • (a)Flip chips
    LED chips, having anodes and cathodes on the epitaxial layer, and assembled after being turned upside down. Due to adoption of a transparent substrate (used to be the lower part), light can be brought out from all parts of the LED chips. The efficiency can be further increased by adding an appropriate reflector to the epitaxial layer side.
    urthermore, the device can be miniaturized because the electrode side can be directly assembled by the use of gold bumps.
  • (b)Laser diodes for optical pickups
    Laser diodes used for reading out information recorded on CD or DVD. (Similar to the needle for analog-type records) For both CD and DVD, there are two different types of optical pickups: read only and read/write. Diodes with higher laser output are used for the latter application.
  • (c)Wire bonding
    This means connecting chip electrode with lead electrode by the use of wire when assembling LED chips into a lamp.