Light emitting diode

Abstract

The invention relates to a light-emitting diode, which comprises a plurality of dotted conducting electrodes, a dielectric layer and an epitaxial composite layer. The dielectric layer is arranged around the point-shaped conducting electrodes, and the epitaxial composite layer is arranged on the point-shaped conducting electrodes and the dielectric layer. Each dotted conduction electrode comprises an ohmic contact metal layer and a carbon-doped gallium arsenide epitaxial layer. Wherein the carbon-doped gallium arsenide epitaxial layer is arranged on the ohmic contact metal layer and is electrically connected with the epitaxial composite layer. According to the invention, the epitaxial structure of the light-emitting diode and the manufacturing process steps thereof can be simplified, the manufacturing process cost is reduced, the overall brightness of the light-emitting diode is effectively improved, and the forward voltage is reduced.

Description

Technical Field

[0001] The invention relates to a light emitting diode, in particular to a high brightness light emitting diode. Background Art

[0002] Light Emitting Diode (hereinafter referred to as LED) has the advantages of high brightness, small size, low power consumption and long life, and is widely used in lighting or display products. Among them, in the existing short-wave infrared light-emitting diode (SWIR LED), in pursuit of the goal of developing different size specifications and improving brightness, the existing technology usually performs different structural tests on the P-type ohmic contact metal and mirror reflection system in the LED structure to improve light reflection and extraction efficiency. For details, please refer to Figure 1 , which shows a common four-element infrared light emitting diode 1 in the wavelength band of 850 to 1100 nanometers (nm). The structure of this type of light emitting diode 1 includes 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. This type of light emitting diode 1 uses the transition layer 10 to adjust the lattice mismatch between the magnesium doped gallium phosphide epitaxial layer 20 and the upper aluminum indium phosphide epitaxial layer 40, and uses the magnesium doped gallium phosphide epitaxial layer 20 as a current spreading layer to achieve the effect of dispersing current and improving brightness, and uses the carbon doped gallium phosphide epitaxial layer 30 as a P-type ohmic contact layer to electrically connect to the lower metal electrode 50. However, the entire structure of the carbon doped gallium phosphide epitaxial layer 30 affects the brightness due to its light absorption effect. Furthermore, since the carbon-doped GaP epitaxial layer 30 and the upper Mg-doped GaP epitaxial layer 20 are made of the same epitaxial material, it is also impossible to perform patterning on the carbon-doped GaP epitaxial layer 30 to reduce the area of ​​a portion of the carbon-doped GaP epitaxial layer 30 and reduce the light absorption effect of the entire structure of the carbon-doped GaP epitaxial layer 30.

[0003] To overcome the above problems, the industry is in urgent need of an innovative light-emitting diode structure and manufacturing process to improve brightness, while also improving the problems of complicated manufacturing process, high cost, and high forward voltage. Summary of the invention

[0004] The main purpose of the present invention is to provide a light-emitting diode with high brightness, simplified manufacturing process steps and reduced cost. Through a new mirror structure, the light extraction efficiency is improved, thereby improving the problems of existing light-emitting diode structures such as poor brightness, complex manufacturing process, high cost and high forward voltage.

[0005] To achieve the above-mentioned purpose, the present invention provides a light-emitting diode, which comprises a plurality of point-shaped conduction electrodes, a dielectric layer and an epitaxial composite layer. The dielectric layer is arranged around each point-shaped conduction electrode, and the epitaxial composite layer is arranged on each point-shaped conduction electrode and the dielectric layer. Each point-shaped conduction electrode comprises an ohmic contact metal layer and a carbon-doped gallium arsenide epitaxial layer. The carbon-doped gallium arsenide epitaxial layer is arranged on the ohmic contact metal layer and is electrically connected to the epitaxial composite layer.

[0006] In one embodiment, the epitaxial composite layer of the light-emitting diode of the present invention comprises a first semiconductor layer, a light-emitting layer, a second semiconductor layer and a third semiconductor layer, wherein 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 one embodiment, the first semiconductor layer of the light emitting diode of the present invention 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 one embodiment, the ratio of the total distribution area of ​​each dot-shaped conducting electrode of the light emitting diode of the present invention to the area of ​​the epitaxial composite layer is about 2.8% to 5.2%.

[0009] In one embodiment, the thickness of the carbon-doped gallium arsenide epitaxial layer in each dot-shaped conducting electrode of the light-emitting diode of the present invention is about

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

[0011] In one embodiment, the light emitting diode of the present invention further comprises a reflective layer, and the dielectric layer and each of the dot-shaped conducting electrodes are disposed on the reflective layer.

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

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

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

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

[0016] In one embodiment, the light emitting diode of the present invention further comprises an upper electrode, which is disposed on the epitaxial composite layer and does not overlap with the dot-shaped conducting electrodes in a vertical position.

[0017] After referring to the accompanying drawings and the embodiments described below, a person skilled in the art will be able to understand other objects of the present invention, as well as the technical means and implementation schemes of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of an existing light emitting diode;

[0019] Figure 2 to Figure 11 A diagram showing the steps of manufacturing a light emitting diode according to an embodiment of the present invention; and

[0020] Fig.12 FIG. 4 is a top view of a light emitting diode structure according to an embodiment of the present invention.

[0021] Description of Reference Numerals

[0022] 1.2 Light Emitting Diode

[0023] 10 Transition layer

[0024] 20 Mg-doped GaP epitaxial layer

[0025] 30 Carbon-doped GaP epitaxial layer

[0026] 40 AlInP epitaxial layer

[0027] 50 Lower metal electrode

[0028] 100 substrates

[0029] 110 first semiconductor layer

[0030] 120 Luminous Layer

[0031] 130 Second semiconductor layer

[0032] 140 Third semiconductor layer

[0033] 150 Carbon doped GaAs epitaxial layer

[0034] 160 ohm contact metal layer

[0035] 162 Point-shaped conductive electrode

[0036] 170 Dielectric layer

[0037] 180 Transparent conductive layer

[0038] 182 Bonding metal layer

[0039] 184 Permanently bonded substrate

[0040] 190 Upper electrode. DETAILED DESCRIPTION

[0041] The present invention will be explained below through embodiments. The embodiments of the present invention are not intended to limit the present invention to any specific environment, application or special method as described in the embodiments. Therefore, the description of the embodiments is only for the purpose of explaining the present invention, and is not intended to limit the present invention. It should be noted that in the following embodiments and drawings, elements that are not directly related to the present invention have been omitted and not shown, and the dimensional relationship between the elements in the drawings is only for easy understanding, and is not intended to limit the actual proportion.

[0042] Please refer to Figure 2 , which discloses one embodiment of the present invention for making a light-emitting diode, especially taking a short-wave infrared light-emitting diode as an example, which uses a gallium arsenide (GaAs) as an epitaxial growth substrate 100, but is not limited to this. Subsequently, an epitaxial composite layer is formed on the gallium arsenide substrate, and the composite layer can be 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. Among them, the light-emitting layer 120 is formed by a multiple quantum well (MQW) structure. In this embodiment, the light-emitting wavelength band of the multiple quantum well can be 1000 to 1200 nanometers (nm). The first semiconductor layer 110 is an N-type aluminum gallium arsenide (AlGaAs) epitaxial layer, the second semiconductor layer 130 is a P-type aluminum gallium arsenide epitaxial layer, and the third semiconductor layer 140 is a P-type aluminum indium phosphide (AlInP) epitaxial layer. It should be noted that the material described in the above embodiment is only an example, and the present invention is not limited thereto. In practical applications, the material and its composition can be adjusted according to the light emission wavelength. For example, the epitaxial layer can be aluminum gallium indium phosphide (AlGaInP), indium gallium phosphide (InGaP), aluminum gallium arsenide (AlGaAs), indium gallium arsenide (InGaAs), indium phosphide (InP), etc.

[0043] Please continue reading Figure 2, a P-type carbon (C)-doped gallium arsenide (GaAs) epitaxial layer 150 is epitaxially formed on the third semiconductor layer 140. It should be noted that there is no lattice mismatch problem between this carbon-doped gallium arsenide epitaxial layer 150 and the upper aluminum indium phosphide epitaxial layer 140, so the transition layer of the existing structure can be omitted. Next, a metal plating manufacturing process and a yellow light etching manufacturing process are performed on the carbon-doped gallium arsenide epitaxial layer 150 to form a patterned ohmic contact metal layer 160. Specifically, this ohmic contact metal layer 160 can be made of gold (Au), silver (Ag), aluminum (Al), beryllium gold (BeAu), germanium gold (GeAu), zinc gold (AuZn) or a combination thereof, such as Figure 3 See next. Figure 4 , the carbon-doped gallium arsenide epitaxial layer 150 is directly etched using the patterned ohmic contact metal layer 160 as a hard mask, so that the patterned carbon-doped gallium arsenide epitaxial layer 150 and the ohmic contact metal layer 160 have the same pattern structure and distribution area, and a plurality of point-shaped conduction electrodes 162 in the light-emitting diode are formed, which are electrically connected to the third semiconductor layer 140. In a preferred embodiment of the present invention, the thickness of the carbon-doped gallium arsenide epitaxial layer 150 in each point-shaped conduction electrode 162 of the light-emitting diode is about Moreover, the carbon doping concentration of the carbon-doped GaAs epitaxial layer is about 4.0*E19 to 1.5*E20.

[0044] See also Figure 5 After a dielectric layer 170 is formed by deposition to cover the entire wafer surface, a portion 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, the dielectric layer 170 is a low refractive index dielectric layer, and its material can be silicon dioxide (SiO2), silicon nitride (Si3N4), etc. Figure 6 As shown, a transparent conductive layer 180 is formed on the surface of the wafer by evaporation to cover the exposed ohmic contact metal layer 160 and the dielectric layer 170, and is electrically connected to the ohmic contact metal layer 160. The transparent conductive layer 180 is made of indium tin oxide (ITO), aluminum zinc oxide (AZO), zinc tin oxide (IZO), nickel oxide, indium tin oxide, cadmium tin oxide, antimony tin oxide or a combination thereof.

[0045] See also Figure 7After forming a reflective bonding metal layer 182 on the transparent conductive layer 180 by vapor deposition, the reflective bonding metal layer 182 on another permanent bonding substrate 184 is metal-bonded, wherein the transparent conductive layer 180 and the reflective bonding metal layer 182 serve as a mirror system of a reflective layer in the light-emitting diode structure of the present invention, and are used to reflect the light emitted by the light-emitting layer upward to increase the light extraction efficiency. The bonding metal material can be gold (Au) or indium gold (InAu) alloy, and the permanent bonding substrate 184 can be, but is not limited to, a silicon substrate or a sapphire substrate. Next, please refer to Figure 8 , remove the GaAs epitaxial substrate 100 to expose the first semiconductor layer 110, and flip it over so that the permanent bonding substrate 184 is located at the bottom of the light emitting diode structure. Fig. 9 , define a planar region of the N-type first semiconductor layer 110 where the upper electrode is to be formed, and perform a roughening process on other regions of the N-type first semiconductor layer 110. Fig.10 As shown, the MESA manufacturing process is performed to etch part of the epitaxial composite layer, that is, to etch 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 to expose part of the dielectric layer 170 and form a protective thin layer (not shown) on the surface of the dielectric layer 170 and the surface of the roughened first semiconductor layer 110, and finally form a cutting path on the substrate. In a preferred embodiment of the present invention, the ratio of the total distribution area of ​​each point-shaped conductive electrode 162 in the light-emitting diode of the present invention to the area of ​​the epitaxial composite layer after the MESA manufacturing process is about 2.8% to 5.2%.

[0046] See also Fig.11 , a patterned N-type upper electrode 190 is formed on the plane area of ​​the first semiconductor layer 110 to form the final structure of the light emitting diode 2 of the present invention. The material of the upper electrode 190 can be germanium gold (GeAu), germanium gold nickel (GeAuNi) or a combination thereof. In particular, the upper electrode 190 and the plurality of lower dot-shaped conductive electrodes 162 composed of the carbon-doped gallium arsenide epitaxial layer 150 and the ohmic contact metal layer 160 do not overlap in vertical position. Please refer to Fig.12 , Fig.12 for Fig.11 The top view of the light emitting diode 2 of the present invention shows that the upper electrode 190 and the lower dot-shaped conductive electrode 162 are not overlapped in vertical position distribution. In this way, the design of the upper and lower electrodes can not only achieve the purpose of current diffusion, but also prevent the light emitted by the light emitting layer from being shielded by the upper electrode 190, thereby improving the light extraction efficiency.

[0047] In summary, the short-wave infrared light-emitting diode structure of the present invention has at least the following advantages: (1) The P-type carbon-doped gallium arsenide epitaxial layer 150 and the upper aluminum indium phosphide epitaxial layer 140 can match the lattice. Therefore, a patterned P-type carbon-doped gallium arsenide epitaxial layer 150 can directly 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 existing light-emitting diode structure, thereby simplifying the epitaxial structure of the light-emitting diode and its manufacturing process steps, and reducing the manufacturing process cost. (2) The P-type carbon-doped gallium arsenide epitaxial layer 150 is synchronously patterned with the lower ohmic contact metal layer 160 to form a new reflective mirror system with the transparent conductive layer and the reflective metal layer. Since the distribution area of ​​the point-shaped P-type carbon-doped gallium arsenide epitaxial layer 150 is greatly reduced, it only accounts for 2.8% to 5.2% of the area of ​​the epitaxial composite layer after the overall MESA manufacturing process. Therefore, it can effectively improve the Figure 1 The problem of light absorption of the entire structure of the conventional carbon-doped gallium phosphide epitaxial layer is solved, which effectively improves the overall brightness of the light-emitting diode (3). P-type carbon-doped gallium arsenide epitaxial layer material is also helpful in reducing the forward voltage compared to the existing carbon-doped gallium phosphide epitaxial layer.

[0048] The above embodiments are only used to illustrate the embodiments of the present invention and to explain the technical features of the present invention, and are not used to limit the protection scope of the present invention. Any changes or equivalent arrangements that can be easily completed by those skilled in the art belong to the scope claimed by the present invention, and the scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A light emitting diode, comprising: A plurality of point-shaped conducting electrodes; a dielectric layer, disposed around the dot-shaped conductive electrodes, and An epitaxial composite layer is disposed on the dot-shaped conductive electrodes and the dielectric layer; in, Each of the point-shaped conductive electrodes comprises: an ohmic contact metal layer; and A carbon-doped gallium arsenide epitaxial layer is disposed on the ohmic contact metal layer and is electrically connected to the epitaxial composite layer.

2. The light emitting diode as claimed in claim 1, wherein the epitaxial composite layer comprises a first semiconductor layer, a light emitting layer, a second semiconductor layer and a third semiconductor layer, wherein 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.

3. The light emitting diode as claimed in 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 . The light emitting diode as claimed in claim 1 , wherein a ratio of a total distribution area of ​​the dot-shaped conducting electrodes to an area of ​​the epitaxial composite layer is approximately 2.8% to 5.2%.

5. The light emitting diode as claimed in claim 1, wherein the thickness of the carbon-doped gallium arsenide epitaxial layer in each of the dot-shaped conducting electrodes is about 100 to 1000 angstroms. 6 . The light emitting diode as claimed in claim 1 , wherein the carbon doping concentration of the carbon-doped GaAs epitaxial layer in each of the dot-shaped conducting electrodes is approximately 4.0*E19˜1.5*E20. 7 . The light emitting diode as claimed in claim 1 , further comprising a reflective layer, wherein the dielectric layer and the dot-shaped conducting electrodes are disposed on the reflective layer.

8. The light emitting diode according to claim 7, wherein: The reflective layer includes a transparent conductive layer and a reflective metal layer, wherein the transparent conductive layer is arranged on the reflective metal layer. 9 . The light emitting diode as claimed in claim 8 , wherein the transparent conductive layer is made of indium tin oxide, zinc aluminum oxide, zinc tin oxide, nickel oxide, indium tin oxide, cadmium tin oxide, antimony tin oxide or a combination thereof. 10 . The light emitting diode as claimed in claim 7 , further comprising a substrate, wherein the reflective layer is disposed on the substrate. 11 . The light emitting diode as claimed in claim 1 , wherein the ohmic contact metal layer is made of gold (Au), silver (Ag), aluminum (Al), beryllium gold (BeAu), germanium gold (GeAu), zinc gold (AuZn) or a combination thereof. 12 . The light emitting diode as claimed in claim 1 , further comprising an upper electrode, wherein the upper electrode is disposed on the epitaxial composite layer and does not overlap with the dot-shaped conducting electrodes in a vertical position.

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