The assignee for this patent, patent number 8648522, is
Reporters obtained the following quote from the background information supplied by the inventors: "Light-emitting diodes (LEDs) have become a symbol of energy-saving industry owing to their low power consumption and long operation life. Meanwhile, LEDs are generally expected to replace traditional fluorescent illumination devices. Whether the LEDs can be broadly implemented in a variety of lighting apparatus or not depends on their light-emitting efficiency and cost. Therefore, how to increase the light extraction efficiency becomes one of the decisive factors to improve the light-emitting efficiency.
"Surface roughening has been an effective means to enhance the light-extraction efficiency, whether on a substrate or on a top semiconductor layer. In the U.S. Pat. No. 6,091,085, as shown in FIG. 1, Lester discloses a light-emitting device having a surface-roughened substrate. LED 10 comprises a sapphire substrate 11 and a plurality of protrusions 111 and depressions 112 formed therein for scattering light emitted from a light-emitting layer 14. Therefore the light extraction efficiency of the light-emitting device is enhanced. The plurality of protrusions 111 and depressions 112 are formed by randomly roughening the surface of the substrate 11 by mechanically polishing or reactive-ion-etching (RIE). Although the light extraction efficiency is enhanced because of the roughened surface of the substrate 11, the surface damages such as the alteration of the surface composition and the lattice distortion are resulted from the roughening process as well. Besides, part of the mask materials or the reactive ions are sputtered onto and even doped into a certain depth of the substrate, therefore the quality of the epitaxy layer deposited thereafter is downgraded. The mechanical polishing process also damages the lattice structure of the substrate surface, such that the quality of the successively grown semiconductor layer, such GaN, is worse, and the internal quantum efficiency is lowered.
"Wang et al. published a paper in Journal of
In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "One aspect of the disclosure proposes a light-emitting device having a patterned substrate. The patterned substrate comprises an uneven surface for scattering light emitted from a light-emitting layer.
"Another aspect of the disclosure proposes a light-emitting device having a patterned substrate comprising a plurality of protrusions and/or depressions. At least one of the depressions and/or extrusions comprises a top portion, a bottom portion, and a sidewall portion enclosing the top portion and the bottom portion, and at least part of the sidewall portion comprises a curve for facilitating the subsequent epitaxy deposition.
"In a preferred embodiment, the surface of the depressions and/or protrusions has fewer lattice damages. The sidewall portion comprises a plurality of symmetric planes. At least one of the top portion and the bottom portion comprises a flat plane.
"In another preferred embodiment, the uneven surface further comprises a rough surface formed on at least one of top portion, the bottom portion, and the sidewall portion."
For more information, see this patent: Hsu, Ta-Cheng; Yang, Ya-Lan; Su, Ying-Yong; Yeh, Ching-Shian; Huang, Chao-Shun; Lee, Ya-Ju. Light-Emitting Device Having a Patterned Substrate and the Method. U.S. Patent Number 8648522, filed
Keywords for this news article include: Electronics, Semiconductor,
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