Light emitting diode

Abstract

The invention relates to a light-emitting diode, which comprises a plurality of point-shaped transparent conducting electrodes, a dielectric layer and an epitaxial composite layer, wherein the dielectric layer is arranged around each point-shaped transparent conducting electrode, and the epitaxial composite layer comprises a carbon-doped gallium arsenide epitaxial layer which is arranged on each point-shaped transparent conducting electrode and the dielectric layer and is electrically connected with each point-shaped transparent conducting electrode. 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 can be effectively improved, and the forward voltage can be 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 the common four-element infrared light emitting diode structure 1 in the wavelength band of 850 to 1100 nanometers (nm). This type of light emitting diode structure 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. 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 carbon doped gallium phosphide epitaxial layer 30 affects the brightness due to its light absorption effect.

[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 problems such as increased manufacturing process costs and excessively high forward voltage due to complicated manufacturing processes. 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 includes a plurality of dot-shaped transparent conductive electrodes, a dielectric layer and an epitaxial composite layer. The dielectric layer is disposed around each dot-shaped transparent conductive electrode, and the epitaxial composite layer includes a carbon-doped gallium arsenide epitaxial layer, which is disposed on each dot-shaped transparent conductive electrode and the dielectric layer, and is electrically connected to each dot-shaped transparent conductive electrode.

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

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

[0008] In one embodiment, the thickness of the carbon-doped gallium arsenide epitaxial layer of the light-emitting diode of the present invention is about 100 to 1000 angstroms.

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

[0010] In one embodiment, the epitaxial composite layer of the light-emitting diode of the present invention further includes a first semiconductor layer, a light-emitting layer, a second semiconductor layer and a third semiconductor layer, wherein the third semiconductor layer is disposed on 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.

[0011] In one embodiment, the first semiconductor layer of the light emitting diode of the present invention 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.

[0012] In one embodiment, the light-emitting diode of the present invention further comprises 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 each of the dot-shaped transparent conductive electrodes, and the second transparent conductive layer is disposed on the metal layer.

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

[0014] In one embodiment, the second 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.

[0015] 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 each of the dot-shaped transparent conductive electrodes in a vertical position.

[0016] 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

[0017] Figure 1 It is a structural schematic diagram of an existing light emitting diode;

[0018] Figure 2 to Figure 9 A diagram showing the steps of manufacturing a light emitting diode according to an embodiment of the present invention; and

[0019] Fig.10 FIG. 4 is a top view of a light emitting diode structure according to an embodiment of the present invention.

[0020] Description of Reference Numerals

[0021] 1.2 LED

[0022] 10 Transition Layer

[0023] 20Mg-doped GaP epitaxial layer

[0024] 30 Carbon-doped GaP epitaxial layer

[0025] 40AlInP epitaxial layer

[0026] 50 Lower metal electrode

[0027] 100 substrates

[0028] 110 first semiconductor layer

[0029] 120 Luminous Layer

[0030] 130 Second semiconductor layer

[0031] 140 Third semiconductor layer

[0032] 150 Carbon doped GaAs epitaxial layer

[0033] 160 Dielectric layer

[0034] 170 Point-shaped transparent conductive electrode

[0035] 180 first transparent conductive layer

[0036] 182 second transparent conductive layer

[0037] 184 Bonding metal layer

[0038] 186 Permanently bonded substrate

[0039] 190 Upper electrode. DETAILED DESCRIPTION

[0040] 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.

[0041] 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.

[0042] Please continue reading Figure 2 , a P-type carbon (C)-doped gallium arsenide (GaAs) epitaxial layer 150 is formed on the third semiconductor layer 140. It should be noted that there is no lattice mismatch between the carbon-doped gallium arsenide epitaxial layer 150 and the aluminum indium phosphide epitaxial layer 140, so the transition layer of the existing structure can be omitted. Moreover, the carbon-doped gallium arsenide epitaxial layer 150 does not have the light absorption problem of the carbon-doped gallium phosphide epitaxial layer in the prior art within the light-emitting band of 1000 to 1200 nanometers (nm). Therefore, the light-emitting diode structure of the present invention can use this carbon-doped gallium arsenide epitaxial layer 150 single-layer structure to directly replace Figure 1The 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 existing light-emitting diode structure shown in FIG can not only simplify the light-emitting diode structure, but also save the time of the traditional time-consuming epitaxial manufacturing process and reduce the manufacturing process cost. In the preferred embodiment of the present invention, the thickness of the carbon-doped gallium arsenide epitaxial layer 150 is about 100 to 1000 angstroms. Moreover, the carbon doping concentration of the carbon-doped GaAs epitaxial layer 150 is about 4.0*E19-1.5*E20.

[0043] See also Figure 3 After a dielectric layer 160 is formed by deposition to cover the entire wafer surface, the dielectric layer 160 is a low refractive index dielectric layer, and its material can be silicon dioxide (SiO2), silicon nitride (Si3N4), etc. Then, a yellow light etching process is used to remove part of the dielectric layer 160 until the surface of the carbon-doped gallium arsenide epitaxial layer 150 is exposed, so as to define the distribution position and area of ​​the subsequent dot-shaped lower electrode. Please refer to Figure 4 , a transparent conductive material is covered on the exposed carbon-doped gallium arsenide epitaxial layer 150 by evaporation to form a plurality of dot-shaped transparent conduction electrodes 170, and after the plurality of dot-shaped transparent conduction electrodes 170 are formed, the evaporation manufacturing process is continued so that the transparent conductive material can cover the dielectric layer 160 and each dot-shaped transparent conduction electrode 170 to form a first transparent conductive layer 180, and the first transparent conductive layer 180 is electrically connected to each dot-shaped transparent conduction electrode 170. In a specific embodiment, the transparent conductive material at least includes indium tin oxide (ITO).

[0044] See also Figure 5 In a preferred embodiment, in order to increase adhesion, a second transparent conductive layer 182 can be formed on the first transparent conductive layer 180 by evaporation and electrically connected to the first transparent conductive layer 180. The material of the second transparent conductive layer 182 is indium tin oxide, 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 6 , a bonding metal layer 184 is formed on the second transparent conductive layer 182 by evaporation, and then metal bonding is performed with the bonding metal layer 184 on another permanent bonding substrate 186, wherein the transparent conductive layers 180, 182 and the bonding metal layer 184 can be used as a reflective mirror system of the light emitting diode of the present invention, to reflect the light emitted by the light emitting layer upward, so as to increase the light extraction efficiency. The material of the aforementioned bonding metal layer 184 can be gold (Au) or indium gold (InAu) alloy, and the permanent bonding substrate 186 can be, but is not limited to, a silicon substrate or a sapphire substrate.

[0046] See also Figure 7, remove the GaAs epitaxial substrate 100 to expose the first semiconductor layer 110, and flip it over so that the permanent bonding substrate 186 is located at the bottom of the light emitting diode structure. Figure 7 , 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. Figure 8 As shown, a 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, the P-type third semiconductor layer 140 and the P-type carbon-doped gallium arsenide epitaxial layer 150 to expose part of the dielectric layer 160, and to form a protective thin layer (for example, a silicon oxide protective thin layer, not shown) on the surface of the dielectric layer 160 and the roughened surface of the first semiconductor layer 110, and finally form a cutting path on the substrate. In a preferred embodiment of the present invention, after the MESA manufacturing process is performed, the ratio of the total distribution area of ​​each point-shaped transparent conductive electrode 170 in the light-emitting diode of the present invention to the area of ​​the epitaxial composite layer after the MESA manufacturing process is about 3.5% to 8%.

[0047] See also Fig. 9 , 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 transparent conductive electrodes 170 do not overlap in vertical position. Fig.10 , Fig.10 for Fig. 9 The top view of the light emitting diode 2 of the present invention shows that the upper electrode 190 and the lower dot-shaped transparent conductive electrode 170 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.

[0048] 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, the P-type carbon-doped gallium arsenide epitaxial layer 150 of the present invention does not need to set a transition layer in the existing light emitting diode structure, and 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 structure, 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 does not have the light absorption problem of the carbon-doped gallium phosphide epitaxial layer in the existing technology within the light emitting band of 1000 to 1200 nanometers (nm) set by the light emitting diode of the present invention. Therefore, compared with the existing structure, the light emitting diode of the present invention can effectively improve the overall brightness of the light emitting diode. (3) The material of the P-type carbon-doped gallium arsenide epitaxial layer 150 is also helpful in reducing the forward voltage compared with the existing carbon-doped gallium phosphide epitaxial layer.

[0049] The above embodiments are only used to illustrate the implementation scheme 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 transparent conductive electrodes; A dielectric layer is disposed around the dot-shaped transparent conductive electrodes; and an epitaxial composite layer; in, The epitaxial composite layer includes a carbon-doped gallium arsenide epitaxial layer, which is disposed on the dot-shaped transparent conductive electrodes and the dielectric layer and is electrically connected to each of the dot-shaped transparent conductive electrodes. 2 . The light emitting diode as claimed in claim 1 , wherein a material of each of the dot-shaped transparent conductive electrodes comprises indium tin oxide. 3 . The light emitting diode as claimed in claim 1 , wherein a ratio of a total distribution area of ​​the dot-shaped transparent conductive electrodes to an area of ​​the epitaxial composite layer is approximately 3.5% to 8%.

4. The light emitting diode as claimed in claim 1, wherein the thickness of the carbon-doped gallium arsenide epitaxial layer is about 100 to 1000 angstroms. 5 . The light emitting diode as claimed in claim 1 , wherein a carbon doping concentration of the carbon-doped GaAs epitaxial layer is approximately 4.0*E19-1.5*E20.

6. The light emitting diode as claimed in claim 1, wherein the epitaxial composite layer further comprises a first semiconductor layer, a light emitting layer, a second semiconductor layer and a third semiconductor layer, wherein the third semiconductor layer is disposed on 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. 7 . The light emitting diode as claimed in claim 6 , 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.

8. The light emitting diode as described in claim 1 further comprises 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. 9 . The light emitting diode as claimed in claim 8 , wherein a material of the first transparent conductive layer comprises indium tin oxide. 10 . The light emitting diode as claimed in claim 8 , wherein the second transparent conductive layer is made of indium tin oxide, aluminum zinc oxide, zinc tin oxide, nickel oxide, indium tin oxide, cadmium tin oxide, antimony tin oxide or a combination thereof. 11 . 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 transparent conductive electrodes in a vertical position.

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