This Non-provisional application claims priority under 35 U.S.C. ยง19(a) on Patent Application No(s). 096111216 filed in Taiwan, Republic of China on Mar. 30, 2007, the entire contents of which are hereby incorporated by reference.
1. Field of Invention
The invention relates to a light emitting source and, in particular, to a light emitting diode apparatus.
2. Related Art
A light emitting diode (LED), a cold lighting element for releasing energy, generates light when electrons and holes in a semiconductor material are combined together Monochromatic light with different wavelengths can be outputted according to the used material. The LEDs can be mainly classified into a visible light LED and an invisible light (infrared) LED. Compared with the conventional light bulb or lamp, the LED has the advantages of power-saving property, vibration-resistant property and high flickering speed. Thus, the LED has become an indispensable and important element in the daily life.
Referring to
In order to achieve the heat-dissipating effect and to enhance the light outputting efficiency, the LED element 10 is typically packaged on a heat dissipating substrate in a flip chip manner, and a reflective layer is formed between the heat dissipating substrate and the LED element 10. The heat dissipating substrate can solve the problem of poor heat dissipating efficiency caused by the conventional epitaxial substrate. The reflective layer reflects the light outputted from the active layer 102 to concentrate the outputted light and thus to emit the concentrated light in the same direction. Thus, the phenomenon of the light loss, which is caused when the light is shielded by the conventional electrodes 11, 12 and the light is outputted toward the epitaxial substrate 100, can be eliminated.
In addition, as shown in
Therefore, there is a need to provide a light emitting diode apparatus having evenly diffused currents, good thermal conductivity and high opto-electronic conversion efficiency.
An object of the invention is to provide a light emitting diode apparatus having evenly diffused currents, good thermal conductivity and high opto-electronic conversion efficiency.
To achieve the above, the invention discloses a light emitting diode apparatus including a heat dissipating substrate, a composite layer, an epitaxial layer, a first electrode and a second electrode. The composite layer includes a reflective layer, a transparent conductive layer and a patterned insulating thermoconductive layer disposed between the reflective layer and the transparent conductive layer. The composite layer is disposed between the heat dissipating substrate and the epitaxial layer and allows currents to concentrate to the reflective layer or the transparent conductive layer and then to be evenly diffused through the transparent conductive layer. The epitaxial layer includes a first semiconductor layer, an active layer and a second semiconductor layer. The first electrode is electrically connected to the first semiconductor layer. The second electrode is electrically connected to the second semiconductor layer.
As mentioned above, the composite layer, which includes the transparent conductive layer, the patterned insulating thermoconductive layer and the reflective layer, is formed between the epitaxial layer and the heat dissipating substrate in the light emitting diode apparatus according to the invention, so that the currents can concentrate and pass through the composite layer and the currents can be evenly distributed through the transparent conductive layer. In addition, the junction between the transparent conductive layer and the epitaxial layer can provide good Ohmic contact to prevent the conventional phenomenon of current blocking effect effectively. In addition, the high thermal conductivity of the patterned insulating thermoconductive layer can provide the heat dissipating path so that the heat dissipating efficiency of the light emitting diode apparatus can be enhanced more effectively with respect to the prior art.
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.
Referring to
The heat dissipating substrate 31 is a permanent substrate having a high coefficient of heat conductivity, and can be made of a metal material, a composite material or an insulating material. In this embodiment, the material of the heat dissipating substrate 31 can be aluminum, copper, aluminum copper oxide, silicon, gallium arsenide, gallium phosphide, silicon carbide, boron nitride, aluminum nitride, a ceramic material or any combination thereof.
The composite layer S includes a reflective layer 32, a transparent conductive layer 34 and a patterned insulating thermoconductive layer 33 disposed between the reflective layer 32 and the transparent conductive layer 34. In this embodiment, the material of the reflective layer 32 is metal, such as platinum (Pt), gold (Au), silver (Ag), palladium (Pd), aluminum (Al), titanium (Ti), iridium (Ir) or rhodium (Rh).
The patterned insulating thermoconductive layer 33 is disposed on the reflective layer 32 and is a patterned layer having patterns arranged separately. The intervals between adjacent patterns of the patterned insulating thermoconductive layer 33 can be the same or different from one another. Because the bandgap of aluminum nitride (AlN) is about 6.2 electron volts (eV), the aluminum nitride (AlN) is light-permeable under the condition of the UV light having the wavelength of about 360 nm. Thus, the patterned insulating thermoconductive layer 33 in this embodiment is light-permeable and has high thermal conductivity. The material of the patterned insulating thermoconductive layer 33 may be silicon carbide (SiC) or aluminum nitride (AlN).
As shown in
As shown in
The first electrode 35 is electrically connected to the first semiconductor layer 301, and the second electrode 36 is electrically connected to the second semiconductor layer 303. Detailed descriptions will be made according to the example, in which the first electrode 35 and the second electrode 36 are disposed at the same side of the heat dissipating substrate 31 to form a front-side light emitting diode apparatus. As shown in
In addition, as shown in
As shown in
When the first electrodes 35, 45 and 55 and the second electrodes 36, 46 and 56 apply voltages to the first semiconductor layer 301 and the second semiconductor layer 303 to generate currents, respectively, the patterned insulating thermoconductive layer 33 can force the currents to concentrate to the transparent conductive layer 34 and then to be evenly diffused through the transparent conductive layer 34. Thus, the electrons and the holes of the first semiconductor layer 301 and the second semiconductor layer 303 are combined in the active layer 302, and the energy released when the electrons and the holes are combined is finally converted into the light.
In addition, the patterned insulating thermoconductive layer 33 having high thermal conductivity can provide a good path for conducting the heat to the heat dissipating substrate 31 so that the operating temperature of the light emitting diode apparatuses 3, 4 and 5 can be effectively lowered.
Furthermore, as shown in
Also, each of the light emitting diode apparatuses 3, 4, 5 of this embodiment further includes an adhesive layer 38, which is disposed between the reflective layer 32 and the heat dissipating substrate 31, and especially disposed between the barrier layer 37 and the heat dissipating substrate 31. The adhesive layer 38 connects the epitaxial layer 30 to the heat dissipating substrate 31, and the material of the adhesive layer 38 can be a silver paste, a solder paste or a solder-silver paste. The adhesive layer 38 is firstly formed on one side of the barrier layer 37, and then the adhesive layer 38 is connected to the barrier layer 37 and the heat dissipating substrate 31.
Also, the patterned insulating thermoconductive layer and the transparent conductive layer can be formed on the concave-convex surface of the reflective layer, and the transparent conductive layer is formed over the patterned insulating thermoconductive layer and the reflective layer. As shown in
In addition, the concave-convex surface of the reflective layer can also be filled by the patterned insulating thermoconductive layer, the transparent conductive layer and the second semiconductor layer. As shown in
Furthermore, as shown in
As shown in
As mentioned hereinabove, the composite layer having the reflective layer, the patterned insulating thermoconductive layer and the transparent conductive layer can also be applied to the front-side light emitting diode apparatus, the vertical light emitting diode apparatus or the flip-chip type light emitting diode apparatus.
In summary the composite layer, which includes the transparent conductive layer, the patterned insulating thermoconductive layer and the reflective layer, is formed between the epitaxial layer and the heat dissipating substrate in the light emitting diode apparatus according to the invention, so that the currents can concentrate and pass through the composite layer and the currents can be evenly distributed through the transparent conductive layer. In addition, the junction between the transparent conductive layer and the epitaxial layer can provide good Ohmic contact to prevent the conventional phenomenon of current blocking effect effectively. In addition, the high thermal conductivity of the patterned insulating thermoconductive layer can provide the heat dissipating path so that the heat dissipating efficiency of the light emitting diode apparatus can be enhanced more effectively with respect to the prior art.
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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096111216 | Mar 2007 | TW | national |