Light-emitting diode

Abstract

To provide a light emitting diode which achieves high brightness, a simplified process steps and reduced costs.SOLUTION: The present invention relates to a light emitting diode 2 which includes multiple dot-like conductive electrodes 162, a dielectric layer 170, and an epitaxial composite layer. The dielectric layer is disposed around each dot-like conductive electrode. The epitaxial composite layer is disposed both on the dot-like conductive electrodes and the dielectric layer. Each dot-like conductive electrode includes an ohmic-contact metal layer 160 and a carbon-doped gallium arsenide epitaxial layer 150. The carbon-doped gallium arsenide epitaxial layer is disposed on the ohmic-contact metal layer and electrically connected to the epitaxial composite layer.SELECTED DRAWING: Figure 11

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 lifespan, 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 to improve light reflection and light extraction efficiency. Specifically, FIG. 1 shows a general light emitting diode 1 for quaternary infrared light 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 electrically connecting 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 brightness. In addition, since the epitaxial layer 30 of carbon-doped gallium phosphide and the epitaxial layer 20 of magnesium-doped gallium phosphide thereon are formed of the same epitaxial material, the area of the epitaxial layer 30 of carbon-doped gallium phosphide cannot be reduced by performing a patterning process on the epitaxial layer 30 of carbon-doped gallium phosphide, and the light absorption effect due to the entire structure of the epitaxial layer 30 of carbon-doped gallium phosphide cannot be reduced.

[0003] To overcome the above problems, developing an innovative light emitting diode structure and manufacturing process that increase brightness while improving problems such as high cost due to a complicated process and high forward voltage has become an urgent issue in the industry.

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 conductive electrodes, a dielectric layer, and an epitaxial composite layer. The dielectric layer is arranged to surround each dot-shaped conductive electrode. The epitaxial composite layer is arranged on each dot-shaped conductive electrode and the dielectric layer. Each dot-shaped conductive electrode includes an ohmic contact metal layer and an epitaxial layer of carbon-doped gallium arsenide. The epitaxial layer of carbon-doped gallium arsenide is arranged on the ohmic contact metal layer and is electrically connected to the epitaxial composite layer.

[0006] 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 electrically connected to the epitaxial layer of carbon-doped gallium arsenide. The second semiconductor layer is arranged on the third semiconductor layer. The light-emitting layer is arranged on the second semiconductor layer. The first semiconductor layer is arranged on the light-emitting layer.

[0007] 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, the second semiconductor layer is an epitaxial layer of P-type aluminum gallium arsenide, and the third semiconductor layer is an epitaxial layer of P-type aluminum indium phosphide.

[0008] In an embodiment of the present invention, the ratio of the total distribution area of the dot-shaped conductive electrodes to the area of the epitaxial composite layer in the light-emitting diode is about 2.8% - 5.2%.

[0009] In an embodiment of the present invention, the thickness of the carbon-doped gallium arsenide epitaxial layer in the dot-shaped conductive electrode of the light-emitting diode is about 100 to 1000 angstroms (Å).

[0010] In an embodiment of the present invention, the carbon-doped gallium arsenide epitaxial layer in the dot-shaped conductive electrode of the light-emitting diode has a carbon doping concentration of about 4.0*E19 to 1.5*E20.

[0011] In an embodiment of the present invention, the light-emitting diode further includes a reflective layer, and the dielectric layer and each dot-shaped conductive electrode are disposed on the reflective layer.

[0012] In an embodiment of the present invention, the reflective layer of the light-emitting diode includes a transparent conductive layer and a reflective metal layer, and the transparent conductive layer is disposed on the reflective metal layer.

[0013] In an embodiment of the present invention, the transparent conductive layer of the light-emitting diode is made of indium tin oxide, aluminum zinc oxide, zinc tin oxide, nickel oxide, cadmium tin oxide, antimony tin oxide, or a combination thereof.

[0014] In an embodiment of the present invention, the light-emitting diode further includes a substrate, and the reflective layer is disposed on the substrate.

[0015] In an embodiment of the present invention, the ohmic contact metal layer of the light-emitting diode is made of gold (Au), silver (Ag), aluminum (Al), beryllium gold (BeAu), gold germanium (GeAu), gold zinc (AuZn), or a combination thereof.

[0016] 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 conductive electrode when viewed from the vertical direction.

[0017] 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

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Figure 1

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Modes for Carrying Out the Invention

[0019] The content of the present invention will be described below through examples. It should be noted that the examples of the present invention are examples of the embodiments and are not intended to be limited to the environments, applications, or specific aspects 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.

[0020] 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). It should be noted that the materials described in the above embodiment are only 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.

[0021] 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 previous layer, the epitaxial layer 140 of aluminum indium phosphide, the transition layer in the conventional structure can be omitted. Next, as shown in FIG. 3, a patterned ohmic contact metal layer 160 is formed on the carbon-doped gallium arsenide epitaxial layer 150 by a metal coating process and a yellow light etching process. Specifically, the ohmic contact metal layer 160 is made of gold (Au), silver (Ag), aluminum (Al), beryllium gold (BeAu), gold germanium (GeAu), gold zinc (AuZn), or a combination thereof. Next, as shown in FIG. 4, the carbon-doped gallium arsenide epitaxial layer 150 is directly etched using the patterned ohmic contact metal layer 160 as a hard mask. Thereby, the pattern structure and the distribution area of the patterned carbon-doped gallium arsenide epitaxial layer 150 and the ohmic contact metal layer 160 become the same. In the light-emitting diode, a plurality of dot-shaped conductive electrodes 162 electrically connected to the third semiconductor layer 140 are formed. In a preferred embodiment of the present invention, the thickness of the carbon-doped gallium arsenide epitaxial layer in the dot-shaped conductive electrode 162 of the light-emitting diode is about 100 to 1000 angstroms (Å). Further, the carbon-doped gallium arsenide epitaxial layer has a carbon doping concentration of about 4.0*E19 to 1.5*E20.

[0022] As shown in FIG. 5, a dielectric layer 170 covering the entire wafer surface is formed by a vapor deposition method. Next, a part of the dielectric layer 170 is removed by a yellow light etching process until the ohmic contact metal layer 160 in the dot-shaped conductive electrode 162 is exposed. Specifically, this dielectric layer 170 is a low refractive index dielectric layer and is made of silicon dioxide (SiO2), silicon nitride (Si3N4), or the like. As shown in FIG. 6, a transparent conductive layer 180 covering the exposed ohmic contact metal layer 160 and the dielectric layer 170 and electrically connected to the ohmic contact metal layer 160 is formed on the wafer surface by a vapor deposition process. The material of the transparent conductive layer 180 is indium tin oxide (ITO), 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. 7, after forming the reflective bonding metal layer 182 on the transparent conductive layer 180 by the vapor deposition process, a metal bond is formed between the reflective bonding metal layer 182 of the permanent bonding substrate 184. The transparent conductive layer 180 and the reflective bonding metal layer 182 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 is gold (Au) or indium-gold (InAu) alloy. The permanent bonding substrate 184 may be a silicon substrate or a sapphire substrate, but is not limited thereto. Next, as shown in FIG. 8, 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 184 becomes the bottom of the structure of the light-emitting diode. Next, as shown in FIG. 9, the planar region of the upper electrode to be formed next is defined in the N-type first semiconductor layer 110, and a roughening process is performed on other regions in the N-type first semiconductor layer 110. Next, as shown in FIG. 10, 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, and the P-type third semiconductor layer 140 is etched to expose a part of the dielectric layer 170. A protective thin film (not shown) is formed on the surface of the dielectric layer 170 and the surface of the first semiconductor layer 110 after the roughening process. Next, a street is formed on the substrate. In a preferred embodiment of the present invention, the ratio of the total distribution area of the dot-shaped conductive electrodes 162 to the area of the epitaxial composite layer after the MESA process in the light-emitting diode is about 2.8% to 5.2%.

[0024] As shown in FIG. 11, 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 conductive electrodes 162 composed of a carbon-doped gallium arsenide epitaxial layer 150 and an ohmic contact metal layer 160 when viewed from the vertical direction. FIG. 12 is a top view showing the light-emitting diode 2 of the present invention in FIG. 11. As shown in FIG. 12, the upper electrode 190 does not overlap with a plurality of lower dot-shaped conductive electrodes 162 when viewed from the vertical direction. Thus, by designing 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.

[0025] 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, one P-type carbon-doped gallium arsenide epitaxial layer 150 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 light-emitting diode structure. Therefore, the present invention can simplify the epitaxial structure of the light-emitting diode and its manufacturing process, and can reduce the process cost. (2) The P-type carbon-doped gallium arsenide epitaxial layer 150 is turned at the same time as the underlying ohmic contact metal layer 160. The transparent conductive layer and the reflective metal layer form an innovative mirror system. The distribution area of the dot-shaped carbon-doped gallium arsenide epitaxial layer 150 is significantly reduced, only accounting for 2.8% - 5.2% of the area of the epitaxial composite layer after the MESA process. Therefore, it can effectively improve the light absorption problem in the entire structure of the conventional carbon-doped gallium phosphide epitaxial layer shown in FIG. 1, and can effectively increase the brightness of the entire light-emitting diode. (3) Compared with the conventional carbon-doped gallium phosphide epitaxial layer, the P-type carbon-doped gallium arsenide epitaxial layer can contribute to the reduction of the forward voltage.

[0026] 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

[0027] 1, 2 Light-emitting diode 10 Transition layer 20 Magnesium-doped gallium phosphide epitaxial layer 30 Epitaxial layer of carbon-doped gallium phosphide 40 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 150 Epitaxial layer of carbon-doped gallium arsenide 160 Ohmic contact metal layer 162 Dot-shaped conductive electrode 170 Dielectric layer 180 Transparent conductive layer 182 Bonding metal layer 184 Permanent bonding substrate 190 Upper electrode

Claims

1. A light-emitting diode, comprising: a plurality of dot-shaped conductive electrodes; a dielectric layer disposed surrounding the dot-shaped conductive electrodes; an epitaxial composite layer disposed on the dot-shaped conductive electrodes and the dielectric layer, wherein the dot-shaped conductive electrodes include an ohmic contact metal layer; and a carbon-doped gallium arsenide epitaxial layer disposed on the ohmic contact metal layer and electrically connected to the epitaxial composite layer, wherein 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 electrically connected to the carbon-doped gallium arsenide epitaxial layer, 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).

2. The light-emitting diode according to claim 1, wherein a ratio of a total distribution area of the dot-shaped conductive electrodes to an area of the epitaxial composite layer is 2.8% to 5.2%.

3. The light-emitting diode according to claim 1, wherein a thickness of the carbon-doped gallium arsenide epitaxial layer in the dot-shaped conductive electrodes is 100 to 1000 angstroms (Å).

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

5. The light-emitting diode according to claim 1, further comprising a reflective layer, wherein the dielectric layer and the dot-shaped conductive electrodes are disposed on the reflective layer.

6. The light-emitting diode according to claim 5, wherein the reflective layer includes a transparent conductive layer and a reflective metal layer, and the transparent conductive layer is disposed on the reflective metal layer.

7. The light-emitting diode according to claim 6, wherein the 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. **Claim 8** The light-emitting diode according to claim 5, further comprising a substrate, wherein the reflective layer is disposed on the substrate. **Claim 9** The light-emitting diode according to claim 1, wherein the ohmic contact metal layer is made of gold (Au), silver (Ag), aluminum (Al), beryllium gold (BeAu), gold germanium (GeAu), gold zinc (AuZn), or a combination thereof. **Claim 10** 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 conductive electrode when viewed from the vertical direction.

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