Light-emitting diode

Abstract

To provide a light emitting diode structure and a manufacturing method, capable of improving the problem of low brightness, complex manufacturing process, high cost, excessive forward voltage, or the like.SOLUTION: The present invention relates to a light emitting diode 2 which includes multiple dot-like transparent conductive electrodes 170, a dielectric layer 160, and an epitaxial composite layer. The dielectric layer is disposed around each dot-like transparent conductive electrode. The epitaxial composite layer is disposed both on each dot-like transparent conductive electrode and the dielectric layer, and includes a carbon-doped gallium arsenide epitaxial layer 150 electrically connected to each dot-like transparent conductive electrode.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a light emitting diode, and particularly to a high-brightness light emitting diode.

Background Art

[0002] A light emitting diode (hereinafter referred to as LED) has advantages such as high brightness, small size, low power consumption, and long life, and is widely used in lighting and display products. In conventional short-wave infrared light emitting diodes (SWIR LEDs), various specifications are developed, and usually, various tests are performed on the P-type ohmic contact metal and the mirror reflection system in the light emitting diode structure in order to improve light reflection and light extraction efficiency. Specifically, FIG. 1 shows the structure of a currently common quaternary infrared light emitting diode 1 of 850 to 1100 nanometers (nm). The structure of this type of light emitting diode 1 has a transition layer 10, a P-type semiconductor layer 20 of magnesium (Mg)-doped gallium phosphide (GaP), and a P-type semiconductor layer 30 of carbon (C)-doped gallium phosphide (GaP). The structure of this type of light emitting diode 1 uses the transition layer 10 to adjust the lattice mismatch between the epitaxial layer 20 of magnesium-doped gallium phosphide and the epitaxial layer 40 of aluminum indium phosphide located thereon, and uses the epitaxial layer 20 of magnesium-doped gallium phosphide as a current diffusion layer to obtain the effects of current dispersion and brightness improvement. In addition, the epitaxial layer 30 of carbon-doped gallium phosphide is used as a P-type ohmic contact layer for being electrically connected to the lower metal electrode 50. However, since the epitaxial layer 30 of carbon-doped gallium phosphide absorbs light, it will have an adverse effect on the brightness.

[0003] In order to overcome the above problems, it has become an urgent issue in the industry to develop an innovative light emitting diode structure and manufacturing process that improve the brightness while simultaneously improving problems such as increased cost due to a complicated process and high forward voltage.

Summary of the Invention

[0004] The main object of the present invention is to provide a light-emitting diode that realizes high brightness, a simplified process, and cost reduction. Through an innovative mirror structure, the effect of improving the light extraction efficiency is realized, and problems such as insufficient brightness, complexity of the manufacturing process, high cost, and high forward voltage, which were problems of the conventional light-emitting diode structure, are improved.

[0005] To achieve the above object, the present invention provides a light-emitting diode including a plurality of dot-shaped transparent conductive electrodes, a dielectric layer, and an epitaxial composite layer. The dielectric layer is disposed surrounding each dot-shaped transparent conductive electrode. The epitaxial composite layer is disposed on each dot-shaped transparent conductive electrode and the dielectric layer, and includes an epitaxial layer of carbon-doped gallium arsenide that is electrically connected to each dot-shaped transparent conductive electrode.

[0006] In an embodiment of the present invention, the material of the dot-shaped transparent conductive electrode of the light-emitting diode includes indium tin oxide.

[0007] In an embodiment of the present invention, the ratio of the total distribution area of the dot-shaped transparent conductive electrodes to the area of the epitaxial composite layer in the light-emitting diode is about 3.5% - 8%.

[0008] In an embodiment of the present invention, the thickness of the epitaxial layer of carbon-doped gallium arsenide in the light-emitting diode is about 100 - 1000 angstroms (Å).

[0009] In an embodiment of the present invention, the epitaxial layer of carbon-doped gallium arsenide in the light-emitting diode has a carbon doping concentration of about 4.0*E19 - 1.5*E20.

[0010] In an embodiment of the present invention, the epitaxial composite layer of the light-emitting diode includes a first semiconductor layer, a light-emitting layer, a second semiconductor layer, and a third semiconductor layer. The third semiconductor layer is disposed on an epitaxial layer of carbon-doped gallium arsenide. The second semiconductor layer is disposed on the third semiconductor layer. The light-emitting layer is disposed on the second semiconductor layer. The first semiconductor layer is disposed on the light-emitting layer.

[0011] In an embodiment of the present invention, the first semiconductor layer of the light-emitting diode is an epitaxial layer of N-type aluminum gallium arsenide (AlGaAs). The second semiconductor layer is an epitaxial layer of P-type aluminum gallium arsenide (AlGaAs). The third semiconductor layer is an epitaxial layer of P-type aluminum indium phosphide (AlInP).

[0012] In an embodiment of the present invention, the light-emitting diode further includes a first transparent conductive layer, a second transparent conductive layer, and a metal layer. The first transparent conductive layer is disposed on the second transparent conductive layer and is electrically connected to each dot-shaped transparent conductive electrode. The second transparent conductive layer is disposed on the metal layer.

[0013] In an embodiment of the present invention, the material of the first transparent conductive layer of the light-emitting diode includes indium tin oxide.

[0014] In an embodiment of the present invention, the second transparent conductive layer of the light-emitting diode is composed of indium tin oxide, aluminum zinc oxide, zinc tin oxide, nickel oxide, cadmium tin oxide, antimony tin oxide, or a combination thereof.

[0015] In an embodiment of the present invention, the light-emitting diode further includes an upper electrode disposed on the epitaxial composite layer, and the upper electrode does not overlap with each dot-shaped transparent conductive electrode when viewed from the vertical direction.

[0016] Those skilled in the art can understand other objects of the present invention, as well as the technical means and embodiments of the present invention, by referring to the drawings and the embodiments described below.

Brief Description of the Drawings

[0017]

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Mode for Carrying Out the Invention

[0018] Hereinafter, the content of the present invention will be described through examples. Note that the examples of the present invention show examples of embodiments, and are not intended to be limited to the environments, applications, or specific modes as described in the examples. Therefore, the description of the examples is for explaining the present invention, but does not limit the present invention. In the embodiments and the drawings, components not directly related to the present invention are omitted and not shown. The dimensional relationships of the components in the drawings are for facilitating understanding and do not limit the actual dimensions.

[0019] Figure 2 is a diagram showing an embodiment of a light-emitting diode fabricated according to the present invention. The present invention takes a short-wavelength infrared light-emitting diode using gallium arsenide (GaAs) as a substrate for epitaxial growth as an example, but is not limited thereto. Next, an epitaxial composite layer is formed on the gallium arsenide substrate. The composite layer has a double heterostructure of aluminum gallium arsenide (AlGaAs). Specifically, in this embodiment, the double heterostructure includes a first semiconductor layer 110, a light-emitting layer 120 formed on the first semiconductor layer 110, a second semiconductor layer 130 formed on the light-emitting layer 120, and a third semiconductor layer 140 formed on the second semiconductor layer 130. The light-emitting layer 120 is formed in a multiple quantum well (MQW) structure. In this embodiment, the multiple quantum well has an emission wavelength of 1000 to 1200 nanometers (nm). The first semiconductor layer 110 is an epitaxial layer of N-type aluminum gallium arsenide (AlGaAs). The second semiconductor layer 130 is an epitaxial layer of P-type aluminum gallium arsenide. The third semiconductor layer 140 is an epitaxial layer of P-type aluminum indium phosphide (AlInP). Note that the materials described in the above embodiment are examples, and the present invention is not limited thereto. In practice, the material and its composition can be adjusted according to the emission wavelength. For example, the epitaxial layer may be aluminum gallium indium phosphide (AlGaInP), indium gallium phosphide (InGaP), aluminum gallium arsenide (AlGaAs), indium gallium arsenide (InGaAs), indium phosphide (InP), etc.

[0020] As shown in FIG. 2, an epitaxial layer 150 of P-type carbon (C)-doped gallium arsenide (GaAs) is formed on the third semiconductor layer 140. Specifically, since there is no lattice mismatch between this carbon-doped gallium arsenide epitaxial layer 150 and the aluminum indium phosphide epitaxial layer 140, the transition layer in the conventional structure can be omitted. Note that the carbon-doped gallium arsenide epitaxial layer 150 has no problem of light absorption by the carbon-doped gallium phosphide epitaxial layer described in the prior art in the emission band of 1000 to 1200 nanometers (nm). Therefore, the light-emitting diode structure of the present invention uses a single-layer structure of the carbon-doped gallium arsenide epitaxial layer 150 to replace the three-layer structure of the transition layer 10, the magnesium-doped gallium phosphide epitaxial layer 20, and the carbon-doped gallium phosphide epitaxial layer 30 in the conventional light-emitting diode structure shown in FIG. 1. Thereby, not only can the structure of the light-emitting diode be simplified, but it is also possible to reduce the time and cost of the conventional time-consuming epitaxial process. In a preferred embodiment of the present invention, the thickness of the carbon-doped gallium arsenide epitaxial layer 150 is about 100 to 1000 angstroms (Å). The carbon-doped gallium arsenide epitaxial layer 150 has a carbon doping concentration of about 4.0*E19 to 1.5*E20.

[0021] As shown in FIG. 3, a dielectric layer 160 covering the entire wafer surface is formed by a vapor deposition method. This dielectric layer 160 is a low refractive index dielectric layer and is made of silicon dioxide (SiO2), silicon nitride (Si3N4), or the like. Next, a part of the dielectric layer 160 is removed by a yellow light etching process until the epitaxial layer 150 of carbon-doped gallium arsenide is exposed. Thereby, the distribution position and area of the subsequent dot-shaped lower electrodes are defined. As shown in FIG. 4, a plurality of dot-shaped transparent conductive electrodes 170 covering the exposed epitaxial layer 150 of carbon-doped gallium arsenide are formed of a transparent conductive material by a vapor deposition process. After the formation of the plurality of dot-shaped transparent conductive electrodes 170, the vapor deposition process is continued to form a first transparent conductive layer 180 covering the dielectric layer 160 and the dot-shaped transparent conductive electrodes 170 with the transparent conductive material. The first transparent conductive layer 180 is electrically connected to each dot-shaped transparent conductive electrode 170. In a specific embodiment, the transparent conductive material includes at least indium tin oxide (ITO).

[0022] As shown in FIG. 5, in a preferred embodiment, a second transparent conductive layer 182 electrically connected to the first transparent conductive layer 180 may be formed by a vapor deposition process to enhance adhesion. The material of the second transparent conductive layer 182 is indium tin oxide, aluminum zinc oxide (AZO), indium zinc oxide (IZO), nickel oxide, cadmium tin oxide, antimony tin oxide, or a combination thereof.

[0023] As shown in FIG. 6, after a bonding metal layer 184 is formed on the second transparent conductive layer 182 by a vapor deposition process, a metal bond is made with the bonding metal layer 184 of the permanent bonding substrate 186. The transparent conductive layers 180 and 182 and the bonding metal layer 184 function as a mirror system of the light-emitting diode of the present invention, reflect the light emitted from the light-emitting layer upward, and can improve the light extraction efficiency. The material of the bonding metal layer 184 is gold (Au), indium gold (InAu) alloy. The permanent bonding substrate 186 may be a silicon substrate or a sapphire substrate, but is not limited thereto.

[0024] As shown in FIG. 7, the first semiconductor layer 110 is exposed by removing the gallium arsenide epitaxial substrate 100. The whole is turned over so that the permanent bonding substrate 186 becomes the bottom of the light-emitting diode structure. Next, as shown in FIG. 7, the planar region of the upper electrode to be formed next on the N-type first semiconductor layer 110 is defined, and a roughening process is performed on other regions in the N-type first semiconductor layer 110. Next, as shown in FIG. 8, a MESA process is performed to etch a part of the epitaxial composite layer. That is, a part of the N-type first semiconductor layer 110, the light-emitting layer 120, the P-type second semiconductor layer 130, the P-type third semiconductor layer 140, and the P-type carbon-doped gallium arsenide epitaxial layer 150 is etched to expose a part of the dielectric layer 160. A protective thin film layer (for example, a silicon oxide protective thin film layer, not shown) is formed on the surface of the dielectric layer 160 and the surface of the first semiconductor layer 110 after the roughening process. Finally, a street is formed on the substrate. In a preferred embodiment of the present invention, after the MESA process, in the light-emitting diode according to the present invention, the ratio of the total distribution area of the dot-shaped transparent conductive electrodes 170 to the area of the epitaxial composite layer is about 3.5% to 8%.

[0025] As shown in FIG. 9, when a patterned N-type upper electrode 190 is formed on the planar region of the first semiconductor layer 110, the structure of the light-emitting diode 2 according to the present invention is completed. The material of the upper electrode 190 is gold germanium (GeAu), germanium gold nickel (GeAuNi), or a combination thereof. In particular, the upper electrode 190 does not overlap with a plurality of lower dot-shaped transparent conductive electrodes 170 when viewed from the vertical direction. FIG. 10 is a top view showing the light-emitting diode 2 of the present invention in FIG. 9. As shown in FIG. 10, the upper electrode 190 does not overlap with a plurality of lower dot-shaped transparent conductive electrodes 170 when viewed from the vertical direction. Thus, with the design of the upper electrode and the lower electrode, not only the purpose of current diffusion can be achieved, but also the light emitted from the light-emitting layer can be prevented from being blocked by the upper electrode 190, and the light extraction efficiency can be improved.

[0026] Based on the above, the structure of the short-wavelength infrared light-emitting diode according to the present invention has at least the following advantages. (1) Lattice matching can be achieved between the P-type carbon-doped gallium arsenide epitaxial layer 150 and the aluminum indium phosphide epitaxial layer 140 thereon. Therefore, the P-type carbon-doped gallium arsenide epitaxial layer 150 of the present invention does not require a transition layer in the conventional light-emitting diode structure, and can replace the three-layer structure of the transition layer, the P-type magnesium-doped gallium phosphide epitaxial layer, and the P-type carbon-doped gallium phosphide epitaxial layer in the conventional structure. Therefore, the present invention can simplify the epitaxial structure of the light-emitting diode and its manufacturing process, and reduce the process cost. (2) The P-type carbon-doped gallium arsenide epitaxial layer 150 has no problem of light absorption by the carbon-doped gallium phosphide epitaxial layer described in the prior art in the emission band of 1000 to 1200 nanometers (nm) set for the light-emitting diode of the present invention. Therefore, compared with the conventional structure, the light-emitting diode of the present invention can effectively increase the overall brightness. (3) Compared with the conventional carbon-doped gallium phosphide epitaxial layer, the P-type carbon-doped gallium arsenide epitaxial layer 150 can contribute to the reduction of the forward voltage.

[0027] The above embodiments are used to illustrate the embodiments of the present invention and to explain the characteristic configurations of the present invention. The present invention is not limited to the above embodiments. Modifications or equivalent arrangements that can be easily made by those skilled in the art are also within the scope of the present invention. The scope of protection of the rights of the present invention shall be based on the scope of the claims.

Description of Reference Numerals

[0028] 1, 2 Light-emitting diode 10 Transition layer 20 Magnesium-doped gallium phosphide epitaxial layer (P-type semiconductor layer of magnesium-doped gallium phosphide) 30 Carbon-doped gallium phosphide epitaxial layer (P-type semiconductor layer of carbon-doped gallium phosphide) Epitaxial layer of aluminum indium phosphide 50 Lower metal electrode 100 Substrate 110 First semiconductor layer 120 Light-emitting layer 130 Second semiconductor layer 140 Third semiconductor layer (epitaxial layer of aluminum indium phosphide) 150 Epitaxial layer of carbon-doped gallium arsenide 160 Dielectric layer 170 Dot-shaped transparent conductive electrode 180 First transparent conductive layer 182 Second transparent conductive layer 184 Bonding metal layer 186 Permanent bonding substrate 190 Upper electrode

Claims

1. A light-emitting diode, comprising: a plurality of dot-shaped transparent conductive electrodes; a dielectric layer disposed surrounding the dot-shaped transparent conductive electrodes; an epitaxial composite layer; wherein the epitaxial composite layer is disposed on the dot-shaped transparent conductive electrodes and the dielectric layer, and includes an epitaxial layer of carbon-doped gallium arsenide electrically connected to each of the dot-shaped transparent conductive electrodes; the epitaxial composite layer includes a first semiconductor layer, a light-emitting layer, a second semiconductor layer, and a third semiconductor layer, the third semiconductor layer is disposed on the epitaxial layer of carbon-doped gallium arsenide, the second semiconductor layer is disposed on the third semiconductor layer, the light-emitting layer is disposed on the second semiconductor layer, and the first semiconductor layer is disposed on the light-emitting layer; the first semiconductor layer is an epitaxial layer of N-type aluminum gallium arsenide (AlGaAs), the second semiconductor layer is an epitaxial layer of P-type aluminum gallium arsenide (AlGaAs), and the third semiconductor layer is an epitaxial layer of P-type aluminum indium phosphide (AlInP), characterized in that it is a light-emitting diode.

2. The light-emitting diode according to claim 1, wherein the material of the dot-shaped transparent conductive electrodes contains indium tin oxide.

3. The light-emitting diode according to claim 1, wherein the ratio of the total distribution area of the dot-shaped transparent conductive electrodes to the area of the epitaxial composite layer is 3.5% to 8%.

4. The light-emitting diode according to claim 1, wherein the thickness of the epitaxial layer of carbon-doped gallium arsenide is 100 to 1000 angstroms (Å).

5. The light-emitting diode according to claim 1, wherein the epitaxial layer of carbon-doped gallium arsenide has a carbon doping concentration of 4.0*E19 to 1.5*E20.

6. Further comprising a first transparent conductive layer, a second transparent conductive layer, and a metal layer, wherein the first transparent conductive layer is disposed on the second transparent conductive layer and is electrically connected to the dot-shaped transparent conductive electrodes, and the second transparent conductive layer is disposed on the metal layer, characterized in that it is a light-emitting diode according to claim 1.

7. The light-emitting diode according to claim 6, wherein the material of the first transparent conductive layer contains indium tin oxide.

8. The light-emitting diode according to claim 6, wherein the second transparent conductive layer is made of indium tin oxide, aluminum zinc oxide, zinc tin oxide, nickel oxide, cadmium tin oxide, antimony tin oxide, or a combination thereof.

9. The light-emitting diode according to claim 1, further comprising an upper electrode disposed on the epitaxial composite layer, wherein the upper electrode does not overlap the dot-shaped transparent conductive electrode when viewed from the vertical direction.

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