This Non-provisional application claims priority under 35 U.S.C. ยง119(a) on Patent Application No(s). 096118930 filed in Taiwan, Republic of China on May 28, 2007, the entire contents of which are hereby incorporated by reference.
1. Field of Invention
The invention relates to a light-emitting diode (LED) apparatus and manufacturing method thereof. More particularly, the invention relates to a current spreading layer and a LED apparatus having a micro/nano structure, and manufacturing method thereof.
2. Related Art
A light-emitting diode (LED) apparatus is a lighting apparatus made of semiconductor materials. The LED apparatus pertaining to a cold lighting apparatus has the advantages of low power consumption, long lifetime, high response speed and small size, and can be manufactured into an extremely small or array-type apparatus. With the continuous development of the recent technology, the application range thereof covers an indicator of a computer or a house appliance product, a backlight source of a liquid crystal display (LCD) apparatus, etc.
However, the LED apparatus still has the problems in that the currents cannot be uniformly spread and that the total reflection decreases the light outputting efficiency so that the light emitting efficiency of the LED apparatus cannot be effectively enhanced.
In general, the LED apparatus may be a flip-chip type LED apparatus, a vertical type LED apparatus or a front-side type LED apparatus. In order to solve the problem of the lowed light emitting efficiency caused by the reflection, the following technology has been proposed. As shown in
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In addition, it is also possible to directly form the roughing surface on a surface of the n-type semiconductor doping layer 121 or the p-type semiconductor doping layer 123 (see
As mentioned hereinabove, although the conventional method can solve the problem of the total reflection, the structure still has the problem that the currents cannot be uniformly spread because the currents flow through the shortest circuit paths. Therefore, when the light emitting area of the LED apparatus is enlarged, the currents still cannot be uniformly distributed.
Therefore, it is an important subject to provide a current spreading layer with a micro/nano structure, a light-emitting diode (LED) apparatus and its manufacturing method that are capable of decreasing the total reflection of light and making currents be uniformly distributed.
In view of the foregoing, the invention is to provide a current spreading layer with a micro/nano structure, a light-emitting diode (LED) apparatus and its manufacturing method that are capable of decreasing the total reflection of light and making currents be uniformly distributed.
To achieve the above, the invention discloses a current spreading layer including a micro/nano roughing structure layer and a transparent conductive layer. The current spreading layer is connected to a semiconductor structure. The micro/nano roughing structure layer has a plurality of hollow parts. The transparent conductive layer covers one surface of the micro/nano roughing structure layer and is filled within the hollow parts.
To achieve the above, the invention also discloses a light-emitting diode (LED) apparatus including an epitaxial layer and a current spreading layer. The epitaxial layer includes a first semiconductor layer, an active layer and a second semiconductor layer in sequence. The current spreading layer is connected to the epitaxial layer and has a micro/nano roughing structure layer and a transparent conductive layer. The micro/nano roughing structure layer has a plurality of hollow parts. The transparent conductive layer covers one surface of the micro/nano roughing structure layer and is filled within the hollow parts.
To achieve the above, the invention further discloses a manufacturing method of a LED apparatus. The method includes the following steps of: forming a first semiconductor layer on an epitaxial substrate; forming an active layer on the first semiconductor layer; forming a second semiconductor layer on the active layer; removing a portion of the active layer and a portion of the second semiconductor layer to expose a portion of the first semiconductor layer; forming a micro/nano roughing structure layer with a plurality of hollow parts on the second semiconductor layer; and forming a transparent conductive layer on the micro/nano roughing structure layer and within the hollow parts.
In addition, the invention also discloses a manufacturing method of a LED apparatus including the following steps of: forming a first semiconductor layer on an epitaxial substrate; forming an active layer on the first semiconductor layer; forming a second semiconductor layer on the active layer; forming a micro/nano roughing structure layer with a plurality of hollow parts on the second semiconductor layer; and forming a transparent conductive layer on the micro/nano roughing structure layer and within the hollow parts.
In summary, the current spreading layer with the micro/nano structure, the LED apparatus and its manufacturing method have the following features. First, the current spreading layer with the micro/nano structure is used in conjunction with a reflective layer, a thermoconductive insulating layer or a thermoconductive adhesive layer so that the current spreading layer with good Ohmic junction is formed in the flip-chip type, vertical type or front-side LED apparatus. Thus, the currents can be uniformly spread, the total reflection can be decreased, and the light extracting efficiency can be enhanced.
The invention will become more fully understood from the detailed description and accompanying drawings, which are given for illustration only, and thus are not limitative of the present invention, and wherein:
The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.
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In this embodiment, the first semiconductor layer 212 and the second semiconductor layer 214 can be respectively a P-type epitaxial layer and an N-type epitaxial layer or an N-type epitaxial layer and a P-type epitaxial layer without any limitation. A refractive index of the micro/nano roughing structure layer 221 is greater than that of air and smaller than that of the epitaxial layer. According to the appearance thereof, the micro/nano roughing structure layer 221 can include a nano-ball, a nano-column, a nano-void, a nano-grid, a nano-line or a nano-concave-convex structure. Herein, the micro/nano roughing structure layer 221 includes a nano-ball, for example, and the material thereof can be aluminum oxide (Al2O3), silicon nitride (Si3N4), tin oxide (SnO2), silicon dioxide (SiO2), resin, polycarbonate or combinations thereof. The material of the transparent conductive layer 222 can include indium tin oxide (ITO), aluminum-doped zinc oxide (AZO) or indium zinc oxide (IZO).
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In this embodiment, the order of the steps is not limited thereto and may be adjusted according to the actual requirement.
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In the step S22, a current spreading layer 32 is connected to the epitaxial layer 31. In this embodiment, the current spreading layer 32 is formed with a micro/nano roughing structure layer 321 on the second semiconductor layer 314 by, for example but not limited to, stacking, sintering, anode aluminum oxidizing (AAO), nano-imprinting, hot pressing, etching or electron beam exposing with an E-beam writer. The micro/nano roughing structure layer 321 has a plurality of hollow parts H31. A transparent conductive layer 322 is formed on the micro/nano roughing structure layer 321 and within the hollow parts H31.
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In this embodiment, the material of the thermoconductive substrate 35 can be silicon, gallium arsenide, gallium phosphide, silicon carbide, boron nitride, aluminum, aluminum nitride, copper or combinations thereof. The thermoconductive adhesive layer 36 is utilized for combining the thermoconductive insulating layer 37 with the thermoconductive substrate 35, and the material thereof can be gold, soldering paste, tin-silver paste, silver paste or combinations thereof.
The thermoconductive insulating layer 37 can prevent the epitaxial layer 31 from being electrically connected to an external device through the thermoconductive substrate 35. The material of the thermoconductive insulating layer 37 is an insulation material, such as aluminum nitride or silicon carbide, having a coefficient of thermal conductivity greater than or equal to 150 W/mK (watt/meter*Kelvin temperature). In addition, the refractive index of the thermoconductive insulating layer 37 ranges between the refractive index (about 2.5) of the epitaxial layer 31 and the refractive index (about 1) of the air.
The reflective layer 38 can be an optical reflective device, a metal reflective layer, a metal dielectric reflective layer composed of dielectric films with different refractive indexes or an optical reflective device composed of micro/nano balls. In other words, the reflective layer 38 can be formed by combining or stacking a plurality of materials. The material of the reflective layer 38 can be platinum, gold, silver, palladium, nickel, chromium, titanium or combinations thereof.
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Next, in the step S27, a first electrode 33 electrically connected to the micro/nano roughing structure layer 321 and a second electrode 34 electrically connected to the second semiconductor layer 314 are respectively formed to constitute another front-side LED apparatus 30 having the micro/nano structure. In this embodiment, the order of the steps is not limited thereto and can be adjusted according to the actual requirement.
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In the step S32, a current spreading layer 42 is connected to the epitaxial layer 41. In this embodiment, the current spreading layer 42 is formed with a micro/nano roughing structure layer 421 on the second semiconductor layer 414 by, for example but not limited to, stacking, sintering, anode aluminum oxidizing (AAO), nano-imprinting, hot pressing, etching or electron beam exposing with an E-beam writer; and the micro/nano roughing structure layer 421 has a plurality of hollow parts H41. A transparent conductive layer 422 is formed on the micro/nano roughing structure layer 421 and within the hollow parts H41.
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In this embodiment, the materials of the layers are the same as those of the above-mentioned embodiments, so detailed descriptions thereof will be omitted. In addition, the order of the steps of this embodiment is not limited thereto and can be adjusted according to the actual requirement.
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In the step S42, a current spreading layer 52 is formed with a micro/nano roughing structure layer 521 on the second semiconductor layer 514 of the epitaxial layer 51 by, for example but not limited to, stacking, sintering, anode aluminum oxidizing (AAO), nano-imprinting, hot pressing, etching or electron beam exposing with an E-beam writer, and the micro/nano roughing structure layer 521 has a plurality of hollow parts H51. A transparent conductive layer 522 is formed on the micro/nano roughing structure layer 521 and within the hollow parts H51.
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In this embodiment, the materials of the layers are the same as those of the above-mentioned embodiments, so detailed descriptions thereof will be omitted. In addition, the order of the steps of this embodiment is not limited thereto and can be adjusted according to the actual requirement.
In addition, the current spreading layer of the above-mentioned embodiment can also have a micro/nano concave-convex structure, which is also constituted by the micro/nano roughing structure layer 521 and the transparent conductive layer 522, as shown in
In summary, the current spreading layer with the micro/nano structure, the LED apparatus and its manufacturing method have the following features. First, the current spreading layer with the micro/nano structure is used in conjunction with a reflective layer, a thermoconductive insulating layer or a thermoconductive adhesive layer so that the current spreading layer with good Ohmic junction is formed in the flip-chip type, vertical type or front-side LED apparatus and the light can be well scattered by the micro/nano roughing structure. Thus, the currents can be uniformly spread, the total reflection can be decreased, and the light extracting efficiency can be enhanced.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.
Number | Date | Country | Kind |
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096118930 | May 2007 | TW | national |