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 more particularly to a high brightness light emitting diode. [Background technology]

[0002] Light emitting diodes (hereinafter referred to as LEDs) have advantages such as high brightness, small size, low power consumption, and long life, and are widely used in lighting and display products. In conventional short-wave infrared light emitting diodes (SWIR LEDs), various specifications are developed and various tests are usually performed on the P-type ohmic contact metal and mirror reflection system in the light emitting diode structure in order to improve the light reflection and light extraction efficiency. Specifically, FIG. 1 shows a currently common 850-1100 nanometer (nm) quaternary infrared light emitting diode 1. The structure of this type of light emitting diode 1 has a transition layer 10, a magnesium (Mg)-doped gallium phosphide (GaP) P-type semiconductor layer 20, and a carbon (C)-doped gallium phosphide (GaP) P-type semiconductor layer 30. The structure of this type of light-emitting diode 1 uses a transition layer 10 to adjust the lattice mismatch between the magnesium-doped gallium phosphide epitaxial layer 20 and the aluminum indium phosphide epitaxial layer 40 located thereon, and uses the magnesium-doped gallium phosphide epitaxial layer 20 as a current spreading layer to achieve the effects of current spreading and brightness improvement. Also, the carbon-doped gallium phosphide epitaxial layer 30 is used as a P-type ohmic contact layer to be electrically connected to the lower metal electrode 50. However, the carbon-doped gallium phosphide epitaxial layer 30 absorbs light, which adversely affects the brightness. Furthermore, since the carbon-doped gallium phosphide epitaxial layer 30 and the magnesium-doped gallium phosphide epitaxial layer 20 thereon are formed of the same epitaxial material, the area of ​​the carbon-doped gallium phosphide epitaxial layer 30 cannot be reduced by patterning the carbon-doped gallium phosphide epitaxial layer 30, and the light absorption effect of the entire structure of the carbon-doped gallium phosphide epitaxial layer 30 cannot be reduced.

[0003] In order to overcome the above problems, it has become an urgent task in the industry to develop an innovative light-emitting diode structure and manufacturing process that can increase brightness while improving problems such as high cost and high forward voltage due to complicated processes. Summary of the Invention

[0004] The main objective of the present invention is to provide a light emitting diode that realizes high brightness, simplified manufacturing process, and low cost. The innovative mirror structure realizes the effect of improving the light extraction efficiency, and improves the problems of the conventional light emitting diode structure, such as insufficient brightness, complicated manufacturing process, high cost, and high forward voltage.

[0005] In order 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 disposed surrounding each of the dot-shaped conductive electrodes. The epitaxial composite layer is disposed on each of the dot-shaped conductive electrodes and the dielectric layer. Each of the dot-shaped conductive electrodes includes an ohmic contact metal layer and a carbon-doped gallium arsenide epitaxial layer. The carbon-doped gallium arsenide epitaxial layer is disposed on the ohmic contact metal layer and 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 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.

[0007] In an embodiment of the present invention, the first semiconductor layer of the light emitting diode is an N-type aluminum gallium arsenide epitaxial layer, the second semiconductor layer is a P-type aluminum gallium arsenide epitaxial layer, and the third semiconductor layer is a P-type aluminum indium phosphide epitaxial layer.

[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% to 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 electrodes 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 comprised of indium tin oxide, zinc aluminum 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 in a 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]

[0018] [Figure 1] Schematic diagram showing the structure of a conventional light-emitting diode [Diagram 2] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Diagram 3] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Figure 4] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Diagram 5] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Figure 6] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Figure 7] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Figure 8] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Figure 9] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Figure 10] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Figure 11] 1 is a diagram showing a manufacturing process of a light-emitting diode according to an embodiment of the present invention. [Figure 12] FIG. 1 is a top view showing a structure of a light-emitting diode according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The contents of the present invention will be described below through examples. The examples of the present invention are examples of embodiments, and are not intended to limit the present invention to the environments, applications, or specific aspects described in the examples. Therefore, the explanation of the examples is for explaining the present invention, but does not limit the present invention. In the embodiments and drawings, components that are not directly related to the present invention are omitted and not shown. The dimensional relationship between the components in the drawings is for ease of understanding, and does not limit the actual dimensions.

[0020] FIG. 2 is a diagram showing an embodiment of a light-emitting diode produced by the present invention. The present invention takes as an example a short-wavelength infrared light-emitting diode using gallium arsenide (GaAs) as an epitaxial growth substrate 100, but is not limited thereto. Next, an epitaxial composite layer is formed on the gallium arsenide substrate. The composite layer is 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 merely examples, and the present invention is not limited thereto. In practice, the materials and their compositions 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), or the like.

[0021] As shown in FIG. 2, a P-type carbon (C) doped gallium arsenide (GaAs) epitaxial layer 150 is formed on the third semiconductor layer 140. In particular, since there is no lattice mismatch between the carbon doped gallium arsenide epitaxial layer 150 and the previous layer, the aluminum indium phosphide epitaxial layer 140, the transition layer in the conventional structure can be omitted. Then, 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 metallization process and a yellow light etching process. In particular, 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 patterned ohmic contact metal layer 160 is used as a hard mask to directly etch the carbon-doped gallium arsenide epitaxial layer 150. As a result, the patterned carbon-doped gallium arsenide epitaxial layer 150 and the ohmic contact metal layer 160 have the same pattern structure and distribution area. 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 150 in the dot-shaped conductive electrodes 162 of the light-emitting diode is about 100 to 1000 angstroms (Å). In addition, 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 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 electrodes 162 is exposed. Specifically, the dielectric layer 170 is a low refractive index dielectric layer, and is made of silicon dioxide (SiO2), silicon nitride (Si3N4), etc. 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 deposition process. The material of the transparent conductive layer 180 is indium tin oxide (ITO), aluminum zinc oxide (AZO), zinc tin oxide (IZO), nickel oxide, cadmium tin oxide, antimony tin oxide, or a combination thereof.

[0023] As shown in FIG. 7, a reflective bonding metal layer 182 is formed on the transparent conductive layer 180 by a deposition process, and then metal bonding is performed with 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 reflector system of the light-emitting diode of the present invention, and can reflect the light emitted from the light-emitting layer upward to improve the light extraction efficiency. The material of the bonding metal is gold (Au) or indium gold (InAu) alloy. The permanent bonding substrate 184 can be, but is not limited to, a silicon substrate or a sapphire substrate. Next, as shown in FIG. 8, the gallium arsenide epitaxial substrate 100 is removed to expose the first semiconductor layer 110. The whole is turned over so that the permanent bonding substrate 184 becomes the bottom of the light-emitting diode structure. Next, as shown in FIG. 9, a planar region of the top electrode to be formed next is defined on the N-type first semiconductor layer 110, and other regions of the N-type first semiconductor layer 110 are roughened. Next, as shown in FIG. 10, the 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 treatment. 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, a patterned N-type upper electrode 190 is formed on the planar region of the first semiconductor layer 110, completing the structure of the light-emitting diode 2 according to the present invention. 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 the plurality of lower dot-shaped conductive electrodes 162, which are composed of the carbon-doped gallium arsenide epitaxial layer 150 and the ohmic contact metal layer 160, when viewed from the vertical direction. FIG. 12 is a top view of the light-emitting diode 2 according to the present invention in FIG. 11. As shown in FIG. 12, the upper electrode 190 does not overlap the plurality of lower dot-shaped conductive electrodes 162 when viewed from the vertical direction. In this way, the design of the upper electrode and the lower electrode not only achieves the purpose of current spreading, but also prevents the light emitted from the light-emitting layer from being blocked by the upper electrode 190, and improves the light extraction efficiency.

[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) The P-type carbon-doped gallium arsenide epitaxial layer 150 and the overlying aluminum indium phosphide epitaxial layer 140 are lattice-matched. 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 and its manufacturing process of the light-emitting diode, and reduce the process cost. (2) The P-type carbon-doped gallium arsenide epitaxial layer 150 is turned simultaneously with the underlying ohmic contact metal layer 160. The transparent conductive layer and the reflective metal layer form an innovative reflector system. The distribution area of ​​the dot-shaped carbon-doped gallium arsenide epitaxial layer 150 is greatly reduced, accounting for only 2.8%-5.2% of the area of ​​the epitaxial composite layer after the MESA process, which effectively improves the light absorption problem in the entire structure of the conventional carbon-doped gallium phosphide epitaxial layer shown in Figure 1, and effectively improves 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 reducing the forward voltage.

[0026] The above examples are for explaining the embodiments of the present invention and for explaining the characteristic configuration of the present invention. The present invention is not limited to the above examples. 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 is based on the claims. [Explanation of symbols]

[0027] 1, 2 Light emitting diode 10 Transition layer 20 Magnesium-doped gallium phosphide epitaxial layers 30 Carbon-doped gallium phosphide epitaxial layers 40 Epitaxial layer of aluminum indium phosphide 50 Lower metal electrode 100 Substrates 110 First semiconductor layer 120 Light-emitting layer 130 Second semiconductor layer 140 Third semiconductor layer 150 Carbon-doped gallium arsenide epitaxial layers 160 Ohmic contact metal layer 162 Dot-shaped conductive electrode 170 Dielectric layer 180 Transparent conductive layer 182 Bonding metal layer 184 Permanently bonded substrate 190 Upper electrode

Claims

1. A light emitting diode, 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; The dot-shaped conductive electrodes are an ohmic contact metal layer; a carbon-doped gallium arsenide epitaxial layer disposed on the ohmic contact metal layer and electrically connected to the epitaxial composite layer.

2. 2. The light-emitting diode of claim 1, 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 being electrically connected to the carbon-doped gallium arsenide epitaxial layer, the second semiconductor layer being disposed on the third semiconductor layer, the light-emitting layer being disposed on the second semiconductor layer, and the first semiconductor layer being disposed on the light-emitting layer.

3. 3. The light-emitting diode according to claim 2, wherein the first semiconductor layer is an N-type aluminum gallium arsenide (AlGaAs) epitaxial layer, the second semiconductor layer is a P-type aluminum gallium arsenide (AlGaAs) epitaxial layer, and the third semiconductor layer is a P-type aluminum indium phosphide (AlInP) epitaxial layer.

4. 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 about 2.8% to 5.2%.

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

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

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

8. 8. The light emitting diode of claim 7, wherein the reflective layer includes a transparent conductive layer and a reflective metal layer, the transparent conductive layer being disposed on the reflective metal layer.

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

10. 8. The light emitting diode of claim 7, further comprising a substrate, the reflective layer being disposed on the substrate.

11. 2. The light emitting diode of 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.

12. The light emitting diode according to claim 1 , further comprising an upper electrode disposed on the epitaxial composite layer, the upper electrode not overlapping the dot-shaped conductive electrodes when viewed in a vertical direction.

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