light-emitting diode

Abstract

To provide an innovative light emitting diode structure that improves the problems of low luminous efficiency, uneven luminescence, and uneven colors caused by non-uniform current distribution in conventional light emitting diodes, and increases the brightness of light emitting diodes.SOLUTION: The present invention relates to a light emitting diode that includes a substrate and a semiconductor epitaxial structure. The semiconductor epitaxial structure is placed on the substrate. The semiconductor epitaxial structure has a semiconductor composite layer and a plurality of current diffusion layers. Each current diffusion layer is located within the semiconductor composite layer. In the plurality of current diffusion layers, current diffusion layers with high doping concentration and current diffusion layers with low doping concentration are alternately stacked.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to light emitting diodes, and more particularly to light emitting diodes with uniform current spreading. [Background technology]

[0002] Light-emitting diodes (LEDs), a type of solid-state light-emitting device, have advantages such as low power consumption, low heat generation, long life, drop resistance, small size, fast response, good photoelectric properties, and stable emission wavelength, and are therefore widely used in home appliances, display lamps, optoelectronic products, etc. With the development of optoelectronic technology, the luminous efficiency, operating life, and brightness of solid-state light-emitting devices have improved significantly, making light-emitting diodes the mainstream of future lighting devices.

[0003] Light-emitting diodes function by applying a voltage between two different types of semiconductor materials, directing electrons and holes into the PN junction region. Current spreading allows carriers to move from high-concentration regions to low-concentration regions, achieving effective carrier injection. When electrons and holes are injected into the PN junction region, they combine in this region. The combination process releases energy, which is what causes the LED to emit light. Current spreading allows many electrons and holes to meet in the light-emitting region, increasing the chances of carrier combination and improving light-emitting efficiency. If the carrier density is not uniform, only some areas will emit light, resulting in uneven lighting and color variation.

[0004] In order to overcome the above problems, it has become an urgent task in the industry to develop an innovative light emitting diode structure that can improve the problem of poor current spreading and increase the brightness of the light emitting diode. Summary of the Invention

[0005] The main object of the present invention is to provide an innovative light-emitting diode structure that improves the problems of reduced light-emitting efficiency, uneven light emission, and uneven color caused by uneven current distribution in conventional light-emitting diodes, and increases the brightness of the light-emitting diode.

[0006] To achieve the above object, the present invention provides a light-emitting diode including a substrate and a semiconductor epitaxial structure. The semiconductor epitaxial structure is disposed on the substrate. The semiconductor epitaxial structure includes a semiconductor composite layer and a plurality of current spreading layers. Each current spreading layer is disposed within the semiconductor composite layer. The plurality of current spreading layers are formed by alternating current spreading layers with high doping concentrations and current spreading layers with low doping concentrations.

[0007] In an embodiment of the present invention, the material of each current spreading layer is one selected from the group consisting of indium gallium phosphide (InGaP), aluminum gallium indium phosphide (AlGaInP), aluminum indium phosphide (AlInP), indium gallium arsenide (InGaAs), aluminum indium gallium arsenide (AlInGaAs), aluminum gallium arsenide (AlGaAs), aluminum gallium arsenide phosphide (AlGaAsP), gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), and indium gallium arsenide phosphide (InGaAsP).

[0008] In an embodiment of the present invention, the doping material of each current spreading layer includes silicon or tellurium.

[0009] In an embodiment of the present invention, one of the two vertically adjacent current spreading layers has a conductivity of about 0.9 to 3.5E18 / cm 3 and the other has a high doping concentration of about 0.9 to 3.5E17 / cm 3 has a low doping concentration of .

[0010] In an embodiment of the present invention, in the plurality of current spreading layers, a thickness of a lower current spreading layer is greater than a thickness of an adjacent upper current spreading layer.

[0011] In an embodiment of the present invention, the thickness of the current diffusion layer is b + a×(N - 1), where N is the total number of the current diffusion layers, N is a positive integer from 1 to 1000, b is the thickness of the first layer of the plurality of current diffusion layers, 0 < b < 10 micrometers, a is the increased thickness of each layer of the current diffusion layer, and 0 < a < 10 micrometers.

[0012] To achieve the above object, the present invention provides another light-emitting diode including a substrate and a semiconductor epitaxial structure. The semiconductor epitaxial structure is disposed on the substrate. The semiconductor epitaxial structure has a semiconductor composite layer and a plurality of current diffusion layers. Each current diffusion layer is disposed within the semiconductor composite layer. In the plurality of current diffusion layers, the thickness of the lower current diffusion layer is greater than the thickness of the adjacent upper current diffusion layer.

[0013] 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

[0014] [Figure 1] Schematic diagram showing the structure of the light-emitting diode in an embodiment of the present invention [Figure 2] Schematic diagram showing the structure of the light-emitting diode in an embodiment of the present invention [Figure 3] Enlarged schematic diagram of a part of the structure of the light-emitting diode in an embodiment of the present invention

Embodiments for Carrying Out the Invention

[0015] The present invention will be described below through examples. Note that the examples of the present invention are merely 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 intended to explain the present invention, but does not limit the present invention. Note that components not directly related to the present invention are omitted and not shown in the embodiments and drawings. The dimensional relationships between the components in the drawings are intended to facilitate understanding and do not limit the actual dimensions.

[0016] FIG. 1 is a schematic diagram showing the structure of a light-emitting diode according to an embodiment of the present invention. As shown in the figure, in this embodiment, the light-emitting diode includes a substrate 10, a semiconductor epitaxial structure 20, and an electrode structure 30. The semiconductor epitaxial structure 20 is disposed on the substrate 10. In this embodiment of the present invention, the substrate 10 is a semiconductor substrate. Preferably, during the manufacturing process of the light-emitting diode, the silicon substrate and the semiconductor epitaxial structure 20 are wafer-bonded. The electrode structure 30 is disposed on the semiconductor epitaxial structure 20. Note that the semiconductor epitaxial structure 20 of the light-emitting diode according to the present invention includes a semiconductor composite layer 100 and a plurality of current spreading layers 200. Each current spreading layer 200 is disposed within the semiconductor composite layer 100.

[0017] The following description will be given with reference to FIGS. 1 and 2. FIG. 2 shows the structure of a light-emitting diode according to an embodiment of the present invention. The semiconductor composite layer 100 includes a P-type semiconductor layer 110, a light-emitting layer 120, an N-type semiconductor lower layer 130, and an N-type semiconductor upper layer 140. Specifically, the P-type semiconductor layer 110 is disposed on a substrate 10. The light-emitting layer 120 is disposed on the P-type semiconductor layer 110. The N-type semiconductor lower layer 130 is disposed on the light-emitting layer 120. The N-type semiconductor upper layer 140 is disposed on a plurality of current spreading layers 200. In a preferred embodiment of the present invention, the current spreading layers 200 have an epitaxial stacked structure of homogeneous semiconductors having the same material composition. Specifically, the P-type semiconductor layer 110 may be made of aluminum gallium indium phosphide, aluminum indium phosphide, or gallium phosphide doped with magnesium or carbon. The material of the N-type semiconductor lower layer 130 and the N-type semiconductor upper layer 140 includes aluminum gallium indium phosphide doped with silicon or tellurium. x Ga 0.5-x In 0.5 P (x = 0 to 0.5). The doping concentration of silicon or tellurium is about 0.9 to 3.5E18 / cm 3 The thickness of the N-type semiconductor lower layer 130 and the N-type semiconductor upper layer 140 is approximately 0.05 to 5 micrometers. The light-emitting layer 120 is formed with a multiple quantum well (MQW) structure. In this embodiment, the multiple quantum well has an emission wavelength of 600 to 700 nanometers, but is not limited thereto. The current spreading structure disclosed in the present invention is also applicable to light-emitting diodes with other emission bands.

[0018] The present invention will be described with reference to FIGS. 1, 2, and 3. FIG. 3 is a schematic diagram showing an enlarged portion of a light-emitting diode according to the present invention. To improve the problems of current crowding and poor diffusion in conventional light-emitting diodes, a semiconductor epitaxial structure 20 of the light-emitting diode according to the present invention includes multiple current spreading layers 200 disposed between the N-type semiconductor lower layer 130 and the N-type semiconductor upper layer 140. This provides a uniform current spreading effect, improving the brightness of the light-emitting diode. Specifically, in the present invention, to achieve the current spreading effect, the multiple current spreading layers disposed between the N-type semiconductor upper and lower layers are alternately stacked with current spreading layers having high and low doping concentrations. For example, the first current spreading layer 210 adjacent to the N-type semiconductor upper layer 140 is an epitaxial layer of aluminum gallium indium phosphide with a low doping concentration. Specifically, the aluminum gallium indium phosphide has a composition of Al x Ga 0.5-x In 0.5 P (x = 0 to 0.5). Silicon or tellurium is used as the doping element, and the doping concentration is about 0.9 to 3.5E17 / cm 3 The second current spreading layer 210, which is adjacent to the first current spreading layer 210, is an epitaxial layer of aluminum gallium indium phosphide with a high doping concentration. The composition of the aluminum gallium indium phosphide is also Al x Ga 0.5-x In 0.5 P (x = 0 to 0.5). Similarly, silicon or tellurium is used as the doping element, and the doping concentration is about 0.9 to 3.5E18 / cm 3 Similarly, the doping concentration of odd-numbered current spreading layers such as the third current spreading layer 230 in the following stacks is the same as the doping concentration of the first current spreading layer 210. The third current spreading layer 230 also has a doping concentration of 0.9 to 3.5E17 / cm 3 The doping concentration of the even-numbered current spreading layers, such as the fourth current spreading layer 240, is the same as the doping concentration of the second current spreading layer 220. The fourth current spreading layer 240 also has a doping concentration of 0.9 to 3.5E18 / cm3 In other embodiments, odd-numbered layers may be aluminum gallium indium phosphide epitaxial layers with high doping concentrations, and even-numbered layers may be aluminum gallium indium phosphide epitaxial layers with low doping concentrations, but this will not be described further. In practical applications, the number of current spreading layers 200 in the semiconductor epitaxial structure 20 of a light-emitting diode according to the present invention can be determined based on the actual diffusion effect. Note that the low or high doping concentrations in each layer of the current spreading layer described above are merely examples and are not intended to be limiting. The present invention does not particularly limit the doping element or doping concentration; in order to create a difference in actual resistance, it is sufficient that the doping concentrations of adjacent diffusion layers above and below are different.

[0019] As previously mentioned, a low doping concentration increases resistance. Conversely, a high doping concentration decreases resistance. The multiple current spreading layers 200 are composed of alternating current spreading layers with high and low doping concentrations. As a result, the lateral current is enhanced through the highly doped, low-resistance layers. However, when the current flows downward, it encounters a low-doped, high-resistance layer, which impedes the vertical current flow and forces the current to flow laterally. Therefore, when a current is injected downward from the upper electrode structure 30 into the current spreading layers, the alternating current spreading layers with high and low doping concentrations create a "vertical impediment, lateral enhancement" diffusion effect. This effectively spreads the current uniformly after passing through the current spreading layers before being injected into the light-emitting layer 120.

[0020] The aluminum gallium indium phosphide current spreading layer described above is only an example, and in actual applications, it can be adjusted according to different epitaxial structures of the light emitting diode. The material of each current spreading layer is one selected from the group consisting of indium gallium phosphide (InGaP), aluminum gallium indium phosphide (AlGaInP), aluminum indium phosphide (AlInP), indium gallium arsenide (InGaAs), aluminum indium gallium arsenide (AlInGaAs), aluminum gallium arsenide phosphide (AlGaAsP), gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), and indium gallium arsenide phosphide (InGaAsP).

[0021] Furthermore, in addition to the aforementioned technical means of alternately stacking current spreading layers with high and low doping concentrations to achieve effective uniform current spreading, adjusting the thickness of each current spreading layer 200 can also achieve a similar uniform current spreading effect. Specifically, in the epitaxial stacking of current spreading layers, the lower current spreading layer is thicker than the upper current spreading layer. In other words, the current spreading layer 200 gradually increases in thickness, becoming denser at the top and sparser at the bottom. The closer to the light-emitting layer 120 from above, the thicker the current spreading layer 200. As the thickness of the current spreading layer increases, the effective resistance of the current spreading layer also gradually increases. As a result, when current is injected from top to bottom, a "vertical interference, lateral enhancement" spreading effect is achieved. Specifically, in the so-called "dense at the top and sparse at the bottom" of this invention, the portion of the current spreading layer closest to the light-emitting layer is the "lower" portion, and the portion away from the light-emitting layer is the "upper" portion. The thickness of the current spreading layer closer to the light-emitting layer is thicker, or "sparser," than the thickness of the current spreading layer farther from the light-emitting layer. Meanwhile, the current spreading layer farther from the light-emitting layer is thinner, or "dense." According to the principle of current spreading, a thin, thick epitaxial layer has high resistance, hindering vertical current flow. Meanwhile, a layer with low resistance enhances lateral current flow. Since a higher diffusion effect is desired closer to the light-emitting layer than at the top, the lower part closer to the light-emitting layer is designed to be thicker.

[0022] Specifically, in actual applications, among the plurality of current diffusion layers, the thickness of the Nth current diffusion layer is b + a×(N - 1). N is the total number of current diffusion layers, which is a positive integer from 1 to 1000, but is not limited to 1000. b is the thickness of the first current diffusion layer 210, where 0 < b < 10 micrometers, but is not limited thereto. a is the increasing thickness of each layer of the current diffusion layer, where 0 < a < 10 micrometers, but is not limited thereto. Table 1 below shows that in the embodiments of the present invention, when the total number of current diffusion layers is 16, the thickness of the first current diffusion layer 210 is b, and the increasing thickness of each layer is a, the thickness of the current diffusion layer gradually changes, and the current diffusion layers with high doping concentration and the current diffusion layers with low doping concentration are alternately laminated.

Table 1

[0023] As described above, the design principle of the diffusion structure adopted in the present invention is as follows. (1) Each current diffusion layer has a dopant, and the current diffusion layers with high doping concentration and the current diffusion layers with low doping concentration are alternately laminated. (2) There is no particular limitation as long as there is a difference in doping concentration. (3) The present invention adopts the design of a gradually thickening current diffusion layer, and there is no need to utilize the inter-lattice piezoelectric field effect. Whether the thickness of the diffusion layer is too thick or too thin, a certain diffusion effect can be obtained. (4) In the epitaxial layer of the diffusion layer of the present invention, it is not limited to the use of superlattice pairs with a certain thickness, but has technical features such as a gradually changing thickness (dense at the top and sparse at the bottom), and / or a structure in which the current diffusion layers with high doping concentration and the current diffusion layers with low doping concentration are alternately laminated.

[0024] The above embodiments illustrate the embodiments of the present invention and 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.

Explanation of Reference Numerals

[0025] 10 Substrate 20 Semiconductor epitaxial structure 30 Electrode structure 100 Semiconductor composite layer 110 P-type semiconductor layer 120 luminescent layer 130 N-type semiconductor lower layer 140 N-type semiconductor upper layer 200 Current diffusion layer 210 First current diffusion layer 220 Second current diffusion layer 230 Third current diffusion layer 240 Fourth Current Diffusion Layer Nth current spreading layer

Claims

1. A light emitting diode, A substrate; a semiconductor epitaxial structure disposed on the substrate, the semiconductor epitaxial structure having a semiconductor composite layer and a plurality of current spreading layers disposed within the semiconductor composite layer; In the plurality of current spreading layers, the current spreading layers having a high doping concentration and the current spreading layers having a low doping concentration are alternately stacked, a thickness of a lower current spreading layer of the plurality of current spreading layers is greater than a thickness of an adjacent upper current spreading layer; a thickness of the current spreading layer is b+a×(N−1), where N is the total number of the current spreading layers and N is a positive integer from 1 to 1000, b is the thickness of a first layer of the current spreading layers and 0<b<10 micrometers, and a is the increasing thickness of each current spreading layer and 0<a<10 micrometers.

2. 2. The light-emitting diode of claim 1, wherein the material of the current spreading layer is one selected from the group consisting of indium gallium phosphide (InGaP), aluminum gallium indium phosphide (AlGaInP), aluminum indium phosphide (AlInP), indium gallium arsenide (InGaAs), aluminum indium gallium arsenide (AlInGaAs), aluminum gallium arsenide (AlGaAs), aluminum gallium arsenide phosphide (AlGaAsP), gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), and indium gallium arsenide phosphide (InGaAsP).

3. 3. The light-emitting diode according to claim 2, wherein the doping material of the current spreading layer includes silicon or tellurium.

4. One of the two vertically adjacent current spreading layers has a density of about 0.9 to 3.5E18 / cm ３ and the other has a high doping concentration of about 0.9 to 3.5E17 / cm ３ 4. The light emitting diode of claim 3, having a low doping concentration of .beta.

5. A light emitting diode, A substrate; a semiconductor epitaxial structure disposed on the substrate, the semiconductor epitaxial structure having a semiconductor composite layer and a plurality of current spreading layers disposed within the semiconductor composite layer; a thickness of a lower current spreading layer of the plurality of current spreading layers is greater than a thickness of an adjacent upper current spreading layer; a thickness of the current spreading layer is b+a×(N−1), where N is the total number of the current spreading layers and N is a positive integer from 1 to 1000, b is the thickness of a first layer of the current spreading layers and 0<b<10 micrometers, and a is the increasing thickness of each current spreading layer and 0<a<10 micrometers.

6. 6. The light-emitting diode of claim 5, wherein the material of the current spreading layer is one selected from the group consisting of indium gallium phosphide (InGaP), aluminum gallium indium phosphide (AlGaInP), aluminum indium phosphide (AlInP), indium gallium arsenide (InGaAs), aluminum indium gallium arsenide (AlInGaAs), aluminum gallium arsenide (AlGaAs), aluminum gallium arsenide phosphide (AlGaAsP), gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), and indium gallium arsenide phosphide (InGaAsP).

7. 6. The light-emitting diode according to claim 5, wherein the current spreading layers are formed by alternately stacking the current spreading layers having a high doping concentration and the current spreading layers having a low doping concentration.

8. 8. The light-emitting diode according to claim 7, wherein the doping material of the current spreading layer comprises silicon or tellurium.

9. One of the two vertically adjacent current spreading layers has a density of about 0.9 to 3.5E18 / cm ３ and the other has a high doping concentration of about 0.9 to 3.5E17 / cm ３ 9. The light emitting diode of claim 8, having a low doping concentration of .beta.

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