A polarized LED and a method of fabricating and packaging the device.
It has recently become possible to prepare AlInGaN LEDs on a-planes and m-planes. These LEDs exhibit linearly polarized light emission. The polarization field is in a particular direction (c-direction) in the plane, and the stress in the QW is anisotropic due to different degrees of lattice mismatch between the substrate and QW in the two perpendicular directions in the plane. Linearly polarized light is an electromagnetic wave that has its electric field only in one plane perpendicular to its propagation. Non-polarized light has its electric field evenly distributed in directions in planes perpendicular to its propagation. A principle application for polarized light is backlighting for liquid crystal displays (LCDs), in which LEDs are beneficial due to their compactness and energy efficiency compared to conventional cold cathode fluorescent tubes. Nitride-based LEDs prepared on a semi-polar plane have also been confirmed to emit polarized light. What is needed is a simplified method of fabricating polarized LEDs and packaging such LEDs.
Researchers at the University of California, Santa Barbara have developed a polarized LED and a method of fabricating and packaging the device. The LED may be attached in a favorable orientation with respect to a package, so that the light polarization direction of emitted light from the package is apparent. The package may include at least one additional marker indicating the light polarization direction. Regardless, if a LCD is large (as for a television screen) or small (as for a cell phone screen), multiple LEDs are used to obtain sufficient brightness. To use an LED array as a linearly polarized light source, the orientation of each die must match. To fabricate these LED arrays as polarized light sources, the marker technique of this technology will make the whole production process simple and reliable, from die attachment into a package to final display unit assembling.
This technology is available for licensing.
|United States Of America||Issued Patent||7,723,746||05/25/2010||2005-614|
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