Light-emitting diode device and manufacturing method thereof

[0001] This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 096147919 filed in Taiwan, Republic of China on Dec. 14, 2007, the entire contents of which are hereby incorporated by reference.

[0002] 1. Field of Invention

[0003] The invention relates to a light-emitting diode (LED) device and a manufacturing method thereof.

[0004] 2. Related Art

[0005] A light-emitting diode (LED) device is a lighting device made of semiconductor materials. The LED device has the advantages of small size, low power consumption, no radiation, mercury-free, long lifetime, fast response speed and high reliability. With the continuous progress of the recent technology, the application range thereof covers the information, communication, customer electronics, vehicle, lighting and traffic sign.

[0006] With reference to FIG. 1, a conventional LED device 1 includes a substrate 11, an epitaxial layer 12, a buffer layer 14, an N-type electrode 16, a P-type electrode 17 and a transparent conductive layer 18. The buffer layer 14, epitaxial layer 12 and transparent conductive layer 18 are disposed on the substrate 11 in sequence.

[0007] The epitaxial layer 12 includes an N-type semiconductor layer 121, a light-emitting layer 122 and a P-type semiconductor layer 123 in sequence. The N-type semiconductor layer 121 is disposed on the buffer layer 14. The light-emitting layer 122 is disposed on the N-type semiconductor layer 121. The P-type semiconductor layer 123 is disposed on the light-emitting layer 122. The N-type electrode 16 is electrically connected to the transparent conductive layer 18 via the epitaxial layer 12, and the P-type electrode 17 are electrically connected to the transparent conductive layer 18.

[0008] In general, the voltage and current of the LED device 1 usually have an exponential relationship. When the N-type electrode 16 and the P-type electrode 17 are applied with a voltage larger than the threshold voltage, the current through the LED device 1 is increased sharply. At the same time, the LED device 1 starts to light.

[0009] However, in the conventional structure of the LED device 1, the current distribution is non-uniform and is concentrated in the area A. This will cause the exceed current density in local area, which affects the lighting efficiency and results in overheat of the local area. Moreover, the lifetime of the LED device 1 will be shortened.

[0010] In view of the foregoing, the invention is to provide a light-emitting diode (LED) device, which has uniform current distribution, and manufacturing method thereof.

[0011] To achieve the above, the invention discloses an LED device including an epitaxial layer, a current blocking layer and a current spreading layer. The current blocking layer is disposed on one side of the epitaxial layer and in contact with a portion of the epitaxial layer. The current spreading layer is disposed on the side of the epitaxial layer and in contact with a portion of the current blocking layer.

[0012] To achieve the above, the invention also discloses a manufacturing method of an LED device. The method includes the steps of: forming an epitaxial layer on a first substrate, forming a current blocking layer on the epitaxial layer, and forming a current spreading layer to cover the current blocking layer or a portion of the epitaxial layer.

[0013] In addition, the invention further discloses a manufacturing method of an LED device. The method includes the steps of: forming a first semiconductor layer on an epitaxial substrate, forming a light-emitting layer on the first semiconductor layer, forming a second semiconductor layer on the light-emitting layer, wherein the second semiconductor layer has a first micro-nano structure, removing a portion of the second semiconductor layer and a portion of the light-emitting layer to expose a portion of the first semiconductor layer, forming a current blocking layer to cover a portion of the second semiconductor layer, a portion of the light-emitting layer and a portion of the first semiconductor layer, and forming a current spreading layer to cover a portion of the second semiconductor layer and a portion of the current blocking layer.

[0014] As mentioned above, the LED device of the present invention has the current blocking layer and current spreading layer, which are disposed adjacent to each other, so that the current distribution of the LED device can be homogenized. That is, the operating LED device of the present invention can have uniform current density so that the heat distribution can be homogenized. Therefore, the lighting efficiency of the LED device can be enhanced.

[0023] 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.

[0024] With reference to FIG. 2, a manufacturing method of a light-emitting diode (LED) device according to a first embodiment of the present invention includes the steps S101 to S110. Illustrations will be made by referring to FIG. 2 in conjunction with FIGS. 3A to 31.

[0025] As shown in FIG. 3A, the step S101 is to form an epitaxial layer 32 on an epitaxial substrate 31. The epitaxial layer 32 includes a first semiconductor layer 321, a light-emitting layer 322 and a second semiconductor layer 323. The first semiconductor layer 321 is formed on the epitaxial substrate 31. Next, the light-emitting layer 322 is formed on the first semiconductor layer 321. Then, the second semiconductor layer 323 is formed on the light-emitting layer 322. The first semiconductor layer 321 and the second semiconductor layer 323 can be, for example but not limited to, an N-type epitaxial layer and a P-type epitaxial layer, respectively. Of course, the first semiconductor layer 321 and the second semiconductor layer 323 can be a P-type epitaxial layer and an N-type epitaxial layer, respectively.

[0026] Referring to FIG. 3B, in the step S102, a current blocking layer 33 is formed on the second semiconductor layer 323. In the embodiment, as shown in FIG. 3C, a first micro-nano structure 33a of the current blocking layer 33 can be formed by way of, for example but not limited to, stacking, sintering, anodic aluminum oxidizing (AAO), nano-imprinting, hot pressing, transfer printing, etching or electron beam writer (E-beam writer) processing. The material of the current blocking layer 33 includes a dielectric material, such as nitride, oxide or carbide, or an insulating material with high thermal-conductive coefficient, such as aluminum nitride (AIN).

[0027] Then, as shown in FIG. 3D, the second semiconductor layer 323 is etched by using the first micro-nano structure 33a of the current blocking layer 33 as an etching stop layer by a thin-film process, a photolithograph process, an etching process, an electron beam writer (E-beam writer) processing, an anodic aluminum oxidizing (AAO) or micro-nano particles.

[0028] Herein, the current blocking layer 33 has the first micro-nano structure 33a, and the second semiconductor 323 has a second micro-nano structure 323a corresponding to the first micro-nano structure 33a. In the embodiment, both of the first and second micro-nano structures 33a, 323a include at least one nano-ball, nano-column, nano-hole, nano-point, nano-line, a nano-concave-convex structure, periodic hole or non-periodic hole.

[0029] As shown in FIG. 3E, the step S103 is to form a current spreading layer 34 to cover the current blocking layer 33 and a portion of the second semiconductor layer 323. The material of the current spreading layer 34 can have high thermal conductivity, low manufacturing cost and high stability. For example, the material of the current spreading layer 34 can be indium tin oxide (ITO), nickel/aluminum alloy (Ni/Au), nickel oxide (NiOx), aluminum-doped zinc oxide (AZO), zinc gallium oxide (GZO), antimony tin oxide (ATO) or any kind of transparent conductive material.

[0030] In the step S104, a reflective layer 35 is then formed on the current spreading layer 34. The reflective layer 35 can be a metal reflective layer so that it can provide the reflection function and a preferred heat conducting path. In the embodiment, the material of the reflective layer 35 can be platinum (Pt), gold (Au), silver (Ag), palladium (Pd), nickel (Ni), chromium (Cr), titanium (Ti), chromium/aluminum alloy (Cr/Al), nickel/aluminum alloy (Ni/Al), titanium/aluminum alloy (Ti/Al), titanium/silver alloy (Ti/Ag), chromium/platinum/aluminum alloy (Cr/Pt/Al) or combinations thereof.

[0031] Alternatively, the reflective layer 35 can also be an optical reflective device composed of dielectric films with different refraction indexes, a metal reflective layer, a metal dielectric reflective layer or an optical reflective device composed of micro/nano balls. Thus, the reflective layer 35 can be formed by combining or stacking several different materials.

[0032] Referring to FIG. 3F, the step S105 is to form an adhesive layer 36 on a substrate 37, such as a conductive substrate or a metal substrate. The adhesive layer 36 can be a conductive adhesive layer capable of adhering at low temperature (lower than 400° C.), such as a pure metal, an alloy, an electroconductive material, a non-electroconductive material, solder, an organic material or any kind of conductive adhesive agent.

[0033] As shown in FIG. 3G, the substrate 37 is combined with the reflective layer 35 by the adhesive layer 36 in the step S106. In the step S107, the LED device 3 formed in the step S106 is turned over, and then the epitaxial substrate 31 is removed, as shown in FIG. 3H.

[0034] Referring to FIG. 3I, the step S108 is to form a transparent conductive layer 38 on the first semiconductor layer 321. In the embodiment, the material of the transparent conductive layer 38 can be indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), nickel/aluminum alloy (Ni/Au), zinc oxide or zinc gallium oxide (GZO).

[0035] The step S109 is to form a first electrode E1 electrically connecting to the transparent conductive layer 38 and form a second electrode E2 electrically connecting to the substrate 37.

[0036] In the step S110, a protective layer 39 is formed on the transparent conductive layer 38 so that a LED 3 is formed. In the embodiment, the protective layer 39 is an anti-reflecting layer, which is made of micro-nano particles, nitride, oxide, carbide, a dielectric material or an insulating material with high thermoconductive coefficient. In practice, the micro-nano particle can be a nano-ball, which is formed on the protective layer 39 by way of, for example but not limited to, dip coating, spin coating or spray coating. By adjusting the material, size and refraction index of the micro-nano particles, the protective layer 39 can have a light-outputting surface with multiple functions of scattering, light-homogenizing, light-diffusing and anti-reflecting.

[0037] It is to be noted that the order of the above-mentioned steps can be changed according to the actual requirement.

[0038] With reference to FIG. 4, a manufacturing method of a light-emitting diode (LED) device according to a second embodiment of the present invention includes the steps S201 to S211. Illustrations will be made by referring to FIG. 4 in conjunction with FIGS. 5A to 5J. Herein, the steps S201 to S203 as shown in FIGS. 5A to 5E are similar to the steps S101 to S103 of the first embodiment, so the detailed descriptions will be omitted.

[0039] In step S204, a reflective layer 35 is formed on the current spreading layer 34, and then an insulating thermoconductive layer 40 is formed on the reflective layer 35. In the embodiment, the material of the insulating thermoconductive layer 40 includes nitride, oxide, carbide, aluminum oxide, silicon carbide or any kind of dielectric materials.

[0040] As shown in FIG. 5F, the step S205 is to form an adhesive layer 36 on a substrate 37. Herein, the material of the adhesive layer 36 is capable of adhering at low temperature and can be a non-conductive material, an organic material or any kind of adhesive agents. The substrate 37 can be a light permeable substrate, a heat-dissipating substrate, an insulating substrate, a heat-dissipating insulating substrate or a complex substrate.

[0041] With reference to FIG. 5G, the substrate 37 and the insulating thermoconductive layer 40 are combined by the adhesive layer 36 in the step S206. As shown in FIG. 5H, the step S207 is to turn over the LED device formed in the step S206, and then remove the epitaxial substrate 31.

[0042] Referring to FIG. 5I, in the step S208, a portion of the first semiconductor layer 321, a portion of the light-emitting layer 322, a portion of the second semiconductor layer 323 and a portion of the current spreading layer 34 are removed so as to expose a portion of the current spreading layer 34.

[0043] In the step S209, a transparent conductive layer 38 is formed on the first semiconductor layer 321 as shown in FIG. 5J. In the embodiment, the material of the transparent conductive layer 38 includes indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), nickel/aluminum alloy (Ni/Au), zinc oxide or zinc gallium oxide.

[0044] Then, the step S210 is to form a first electrode E3 electrically connecting to the transparent conductive layer 38 and form a second electrode E4 electrically connecting to the exposed current spreading layer 34.

[0045] In the step S211, a protective layer 39 is formed on the transparent conductive layer 38 and a portion of the current spreading layer 34 so that the LED 4 is formed. In the embodiment, the protective layer 39 is an anti-reflecting layer, which is made of micro-nano particles, nitride, oxide, carbide, a dielectric material or an insulating material with high thermoconductive coefficient. In practice, the micro-nano particle can be a nano-ball, which is formed on the protective layer 39 by way of, for example but not limited to, dip coating, spin coating or spray coating. By adjusting the material, size and refraction index of the micro-nano particles, the protective layer 39 can have a light-outputting surface with multiple functions of scattering, light-homogenizing, light-diffusing and anti-reflecting.

[0046] It is to be noted that the order of the above-mentioned steps can be changed according to the actual requirement.

[0047] With reference to FIG. 6, a manufacturing method of a light-emitting diode (LED) device according to a third embodiment of the present invention includes the steps S301 to S306. Illustrations will be made by referring to FIG. 6 in conjunction with FIGS. 7A to 7E. Herein, the illustration with reference to FIG. 7A is similar to that described in the previous embodiment, so the detailed descriptions will be omitted.

[0048] In the embodiment, the second semiconductor layer 323 is formed on the light-emitting layer 322 and is etched by a thin-film process, a photolithograph process, an etching process, an electron beam writer (E-beam writer) processing, an anodic aluminum oxidizing (AAO) or using micro-nano particles to the first micro-nano structure 323a as shown in FIG. 7B.

[0049] The first micro-nano structure 323a includes at least one nano-ball, nano-column, nano-hole, nano-point, nano-line, a nano-concave-convex structure, periodic hole or non-periodic hole. In the embodiment, the first micro-nano structure includes the nano-column, for example.

[0050] As shown in FIG. 7C, the step S302 is to remove a portion of the epitaxial layer 32. In details, a portion of the second semiconductor layer 323 and a portion of the light-emitting layer 322 are removed to expose a portion of the first semiconductor layer 321.

[0051] As shown in FIG. 7D, in the step S303, a current blocking layer 33 is formed on the second semiconductor layer 323. In the embodiment, the current blocking layer 33 can be formed on the second semiconductor layer 323 by way of, for example but not limited to, stacking, sintering, anodic aluminum oxidizing (AAO), nano-imprinting, hot pressing, transfer printing, etching or electron beam writer (E-beam writer) processing. Thus, the current blocking layer 33 covers a portion of the second semiconductor layer 323, a portion of the light-emitting layer 322 and a portion of the first semiconductor layer 321. The material of the current blocking layer 33 includes nitride, oxide or carbide.

[0052] In the step S304, as shown in FIG. 7E, a current spreading layer 34 is formed to cover a portion of the second semiconductor layer 323 and a portion of the current blocking layer 33. The material of the current spreading layer 34 includes indium tin oxide (ITO), nickel/aluminum alloy (Ni/Au), nickel oxide (NiOx), aluminum-doped zinc oxide (AZO), zinc gallium oxide (GZO), antimony tin oxide (ATO) or any kind of transparent conductive material.

[0053] The step S305 is to form a reflective layer 35 on the current spreading layer 34. The reflective layer 35 can be a metal reflective layer, so that it can provide the reflection function and a preferred heat conducting path. In the embodiment, the material of the reflective layer 35 can be platinum (Pt), gold (Au), silver (Ag), palladium (Pd), nickel (Ni), chromium (Cr), titanium (Ti), chromium/aluminum alloy (Cr/Al), nickel/aluminum alloy (Ni/Al), titanium/aluminum alloy (Ti/Al), titanium/silver alloy (Ti/Ag), chromium/platinum/aluminum alloy (Cr/Pt/Al) or combinations thereof.

[0054] Alternatively, the reflective layer 35 can also be an optical reflective device composed of dielectric films with different refraction indexes, a metal reflective layer, a metal dielectric reflective layer or an optical reflective device composed of micro/nano balls. Thus, the reflective layer 35 can be formed by combining or stacking several different materials.

[0055] The step S306 is to form a first electrode E5 electrically connecting to the exposed first semiconductor layer 321 and form a second electrode E6 electrically connecting to the reflective layer 35 so as to form the LED device 5.

[0056] It is to be noted that the order of the above-mentioned steps can be changed according to the actual requirement.

[0057] In summary, the LED device of the present invention has the current blocking layer and current spreading layer, so that the current distribution of the LED device can be homogenized. That is, the operating LED device of the present invention can have uniform current density so that the heat distribution can be homogenized. Therefore, the lighting efficiency of the LED device can be enhanced.

[0058] Although the present 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 present invention.