Light emitting diode

Abstract

The invention relates to a light emitting diode which comprises a substrate and a semiconductor epitaxial structure. The semiconductor epitaxial structure is arranged on the substrate and comprises a semiconductor composite layer and a plurality of current diffusion layers. Each current diffusion layer is disposed in the semiconductor composite layer. Wherein the doping concentrations of the upper and lower adjacent current diffusion layers in the current diffusion layers are alternated from high to low.

Description

Technical Field

[0001] The invention relates to a light emitting diode, in particular to a light emitting diode with uniform current diffusion. Background Art

[0002] Light-emitting diodes (LEDs) in solid-state light-emitting components have low power consumption, low heat generation, long life, drop resistance, small size, fast response speed, and good photoelectric properties, such as stable light wavelength, so they have been widely used in household devices, indicator lights, and optoelectronic products. With the development of optoelectronic technology, solid-state light-emitting components have made considerable progress in luminous efficiency, operating life, and brightness. LEDs have become the mainstream of future lighting devices.

[0003] The working principle of light-emitting diodes is to guide electrons and holes into the PN junction area by applying voltage between two different types of semiconductor materials. Current diffusion enables these carriers to move from high concentration areas to low concentration areas, thereby achieving effective carrier injection. When electrons and holes are injected into the PN junction area, they recombine in this area, and this recombination process releases energy, which is the light emitted by the LED. Current diffusion ensures that a large number of electrons and holes can meet in the light-emitting area, increasing the chance of carrier recombination, thereby enhancing the luminous efficiency. If the carrier density is uneven, only some areas will emit light, which will result in uneven light emission and color changes.

[0004] In order to overcome the above problems, the industry is in urgent need of an innovative light emitting diode structure to improve the above problem of poor current diffusion and thereby enhance the brightness of the light emitting diode. Summary of the invention

[0005] The main purpose of the present invention is to provide an innovative light-emitting diode structure to improve the problems of reduced luminous efficiency, uneven luminescence, color variation, etc. caused by uneven current distribution in existing light-emitting diode elements, thereby improving the brightness of the light-emitting diode.

[0006] To achieve the above-mentioned object, the present invention provides a light-emitting diode, which comprises a substrate and a semiconductor epitaxial structure. The semiconductor epitaxial structure is disposed on the substrate, and comprises a semiconductor composite layer and a plurality of current diffusion layers. Each current diffusion layer is disposed in the semiconductor composite layer. Among the current diffusion layers, the doping concentrations of the upper and lower adjacent current diffusion layers are alternating between high and low.

[0007] In one embodiment, the light-emitting diode provided by the present invention, wherein the material of each current diffusion layer is selected from one of 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), indium gallium arsenide phosphide (InGaAsP).

[0008] In one embodiment, the light-emitting diode provided by the present invention, wherein the doping material of each current diffusion layer comprises silicon or tellurium.

[0009] In one embodiment, the light-emitting diode provided by the present invention, wherein the high doping concentration of the current diffusion layers adjacent to each other up and down is about 0.9 - 3.5E18 / cm 3 and the low doping concentration is about 0.9 - 3.5E17 / cm 3 .

[0010] In one embodiment, the light-emitting diode provided by the present invention, wherein the thickness of the lower current diffusion layer among these current diffusion layers is thicker than the adjacent upper current diffusion layer.

[0011] In one embodiment, the light-emitting diode provided by the present invention, wherein the thickness of each current diffusion layer is b + a×(N - 1), where N is the total number of these current diffusion layers, N is a positive integer between 1 and 1000, b is the thickness of the first layer among these current diffusion layers, 0 < b < 10 microns, and a is the thickness increased for each layer among these current diffusion layers, 0 < a < 10 microns.

[0012] To achieve the above object, the present invention provides another light-emitting diode, which comprises a substrate and a semiconductor epitaxial structure. The semiconductor epitaxial structure is disposed on the substrate and comprises a semiconductor composite layer and a plurality of current diffusion layers. Each current diffusion layer is disposed in the semiconductor composite layer. Among them, the thickness of the lower current diffusion layer among these current diffusion layers is thicker than the adjacent upper current diffusion layer.

[0013] After referring to the accompanying drawings and the embodiments described subsequently, those of ordinary skill in the art can understand other objects of the present invention, as well as the technical means and embodiments of the present invention. Description of the Drawings

[0014] Figure 1 is a schematic structural diagram of a light-emitting diode in an embodiment of the present invention;

[0015] Figure 2is a schematic diagram of the structure of a light emitting diode in one embodiment of the present invention; and

[0016] Figure 3 It is a partially enlarged schematic diagram of a light emitting diode in one embodiment of the present invention.

[0017] Description of Reference Numerals

[0018] 10 substrate

[0019] 20 Semiconductor epitaxial structure

[0020] 30 Electrode structure

[0021] 100 Semiconductor composite layer

[0022] 110 P-type semiconductor layer

[0023] 120 Luminous Layer

[0024] 130 N-type semiconductor lower layer

[0025] 140 N-type semiconductor upper layer

[0026] 200 Current diffusion layer

[0027] 210 First current diffusion layer

[0028] 220 Second current diffusion layer

[0029] 230 Third current diffusion layer

[0030] 240 Fourth current diffusion layer

[0031] N: Nth current diffusion layer. DETAILED DESCRIPTION

[0032] The present invention will be explained below by way of examples, and the examples of the present invention are not intended to limit the present invention to any specific environment, application or special method as described in the examples. Therefore, the description of the examples 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 examples and drawings, elements that are not directly related to the present invention have been omitted and are 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.

[0033] See also Figure 1, which is a schematic diagram of the structure of a light emitting diode in 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, wherein the semiconductor epitaxial structure 20 is disposed on the substrate 10. In the embodiment of the present invention, the substrate 10 is a semiconductor substrate. Preferably, a silicon substrate and the semiconductor epitaxial structure 20 are wafer bonded during the manufacturing process of the light emitting diode, and the electrode structure 30 is disposed on the semiconductor epitaxial structure 20. In addition, the semiconductor epitaxial structure 20 of the light emitting diode of the present invention includes a semiconductor composite layer 100 and a plurality of current diffusion layers 200, and each current diffusion layer 200 is disposed in the semiconductor composite layer 100.

[0034] Please refer to the combined Figure 1 and Figure 2 , Figure 2 The light emitting diode structure in one embodiment of the present invention is shown, wherein 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 the 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, and the N-type semiconductor upper layer 140 is disposed on the current diffusion layers 200. In a preferred embodiment of the present invention, the current diffusion layer 200 of the present invention is an epitaxial stack structure composed of homogeneous semiconductors with the same material ratio. Specifically, the material of the P-type semiconductor layer 110 can be aluminum gallium indium phosphide doped with magnesium or carbon, aluminum indium phosphide, and gallium phosphide, and the material of the N-type semiconductor lower layer 130 and the N-type semiconductor upper layer 140 can be aluminum gallium indium phosphide doped with silicon or tellurium, with the ratio of Al to N. x Ga 0.5-x In 0.5 P(x=0~0.5), silicon or tellurium doping concentration is about 0.9~3.5E18 / cm 3 The thickness of each layer of the N-type semiconductor lower layer 130 and the N-type semiconductor upper layer 140 is about 0.05 to 5 microns. The light-emitting layer 120 is formed by a multiple quantum well (MQW) structure. In this embodiment, the multiple quantum well light-emitting band can be 600 to 700 nanometers, but it is not limited thereto. The current diffusion structure disclosed in the present invention can be specifically applied to light-emitting diodes of other light-emitting bands.

[0035] Please refer to the combined Figure 1 , Figure 2 and Figure 3 ,in Figure 3A partially enlarged schematic diagram of the light-emitting diode of the present invention is shown. In order to improve the problems of current crowding and poor diffusion in existing light-emitting diodes, a plurality of current diffusion layers 200 are arranged between the two epitaxial layers of the N-type semiconductor lower layer 130 and the N-type semiconductor upper layer 140 in the semiconductor epitaxial structure 20 of the light-emitting diode of the present invention, so as to achieve the effect of uniform current diffusion, thereby improving the brightness of the light-emitting diode. Specifically, in order to achieve the effect of current diffusion, the present invention has the characteristics of alternating high and low doping concentrations between the upper and lower layers of the N-type semiconductor. For example, the first current diffusion layer 210 of the adjacent N-type semiconductor upper layer 140 is an aluminum gallium indium phosphide epitaxial layer with a low doping concentration, and the specific ratio of aluminum gallium indium phosphide is Al: x Ga 0.5-x In 0.5 P (x = 0 to 0.5), with silicon or tellurium as the doping element, and the doping concentration is about 0.9 to 3.5E17 / cm 3 Secondly, the second current diffusion layer 220 disposed below and adjacent to the first current diffusion layer 210 is a highly doped aluminum gallium indium phosphide epitaxial layer. The ratio of aluminum gallium indium phosphide is also Al x Ga 0.5-x In 0.5 P (x = 0 to 0.5), with silicon or tellurium as the doping element, the doping concentration is about 0.9 to 3.5E18 / cm 3 Similarly, the third current diffusion layer 230 and other odd-numbered current diffusion layers stacked below have the same doping concentration as the first current diffusion layer 210, and the same doping concentration is 0.9-3.5E17 / cm 3 The low-doped AlGaInP epitaxial layer, the fourth current diffusion layer 240 and the even-numbered current diffusion layer have the same doping concentration as the second current diffusion layer 220, and the same doping concentration is 0.9-3.5E18 / cm 3 The invention also provides a highly doped AlGaInP epitaxial layer. Conversely, in other embodiments, the odd-numbered layers can be arranged as highly doped AlGaInP epitaxial layers, and the even-numbered layers can be arranged as low-doped AlGaInP epitaxial layers. The same is true for the following embodiments. In practical applications, the number of the multiple current diffusion layers 200 in the semiconductor epitaxial structure 20 of the light-emitting diode of the present invention can be determined according to the actual diffusion uniformity effect. It should be noted that the low doping concentration or high doping concentration of each layer of the above-mentioned current diffusion layer is only an example and is not limited to this. The present invention has no restrictions on doping elements and doping concentrations. It is only necessary that the upper and lower adjacent diffusion layers have a difference in high and low doping concentrations to cause a substantial resistance difference.

[0036] As described above, when the doping concentration is low, its resistance is relatively large, and conversely, when the doping concentration is high, its resistance is relatively small. The multiple current diffusion layers 200 have an alternating arrangement of high and low doping concentrations between the upper and lower adjacent current diffusion layers, which will cause the current to be strengthened laterally in the high doping concentration layer with low resistance, but when the current flows downward, it encounters the low doping concentration layer with high resistance, so that its longitudinal flow is blocked, forcing the current to develop laterally. Therefore, when the current is injected into the current diffusion layer from the upper electrode 30 downward, the structure of alternating high and low doping concentrations between the layers will produce a diffusion effect of "vertical obstruction and lateral enhancement" between the layers, so that the current can be effectively diffused evenly after the current flows through the current diffusion layer and before it is injected into the light-emitting layer 120.

[0037] The aluminum gallium indium phosphide current diffusion layer disclosed above is only one embodiment. In actual application, adjustments can be made according to different epitaxial structures of visible light emitting diodes. The material of each current diffusion layer can be selected from one of 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).

[0038] In addition, in order to effectively and evenly diffuse the current, in addition to the above-mentioned technical means of alternating high and low doping concentrations, the thickness of each current diffusion layer 200 can also be adjusted to achieve the effect of uniform diffusion of the same current. Specifically, when stacking each current diffusion layer in epitaxial stacking, the thickness of the current diffusion layer in the lower layer of the adjacent current diffusion layers can be thicker than the thickness of the adjacent upper layer of the current diffusion layer. In other words, the thickness of the current diffusion layer 200 is "gradually changed, dense at the top and sparse at the bottom", and the closer to the light-emitting layer 120 from top to bottom, the thicker the current diffusion layer 200 is. Through the influence of the gradual thickening of the thickness of the current diffusion layer, the actual sheet resistance of each diffusion layer will also gradually increase, forcing the current to be injected from top to bottom, and can also achieve the effect of uniform diffusion of "vertical obstruction and lateral enhancement". It should be noted that the so-called "dense on top and sparse on bottom" in the present invention is defined as the direction in which the current diffusion layer is closer to the light-emitting layer is "downward"; conversely, the direction away from the light-emitting layer is "upward", and the thickness of the current diffusion layer closer to the light-emitting layer is relatively thicker than the thickness away from the light-emitting layer, that is, "sparser"; conversely, the thickness of the current diffusion layer away from the light-emitting layer is thinner, that is, "dense". The principle of current diffusion is that the longitudinal flow of current is blocked because of the low concentration and thick epitaxial layer, which has a large resistance; conversely, the resistance of one layer is lower, and the lateral flow of current in the upper layer is enhanced. The closer to the light-emitting layer, the stronger the diffusion effect is expected to be than the upper half, so a higher weight must be assigned, so the thickness of the lower half closer to the light-emitting layer is thicker.

[0039] Specifically, in actual application, the thickness of the Nth current diffusion layer among multiple current diffusion layers can be set to b + a×(N - 1). Here, N is the total number of all current diffusion layers, and N can be a positive integer between 1 and 1000, but not limited to 1000. b is the thickness of the first current diffusion layer 210, where 0 < b < 10 microns, but not limited thereto. a is the increased thickness of each layer among these current diffusion layers, where 0 < a < 10 microns, but not limited thereto. Please refer to Table 1 below, which specifically shows the state where the thickness of each current diffusion layer gradually changes and the doping concentration alternates between high and low in an embodiment of the present invention when the total number of current diffusion layers is 16, the thickness b of the first current diffusion layer 210, and the increased thickness a of each layer.

[0040]

[0041]

[0042] Table 1

[0043] In summary, the design principle of the diffusion structure adopted by the present invention is summarized as follows: (1) Each layer of the current diffusion layer has dopants, and the doping concentration of each layer alternates between high and low. (2) There is no limit to the doping concentration, only a difference between high and low. (3) The present invention uses the means of gradually changing the thickness, without generating an interlattice piezoelectric field effect. Even if the thickness of each diffusion layer is too thick or too thin, a certain degree of diffusion effect can still be achieved. (4) The present invention does not limit the epitaxial layer stacking of the diffusion layer to a superlattice pair with a fixed thickness ratio, but can be a stacking with a gradually changing thickness (dense at the top and sparse at the bottom) and / or an alternating high and low doping concentration.

[0044] The above embodiments are only used to illustrate the implementation schemes of the present invention and to explain the technical features of the present invention, rather than to limit the protection scope of the present invention. Any change or equivalent arrangement that can be easily completed by any person skilled in the art belongs to the scope claimed by the present invention, and the scope of the right protection of the present invention shall be subject to the scope of the appended claims.

Claims

1. A light-emitting diode, comprising: a substrate; and a semiconductor epitaxial structure disposed on the substrate, comprising: a semiconductor composite layer; and a plurality of current diffusion layers disposed in the semiconductor composite layer, in, wherein the doping concentrations of two adjacent current diffusion layers among the current diffusion layers alternate between high and low.

2. The light emitting diode according to claim 1, wherein: The material of each current diffusion layer is selected from one of the group consisting of indium gallium phosphide, aluminum gallium indium phosphide, aluminum indium phosphide, indium gallium arsenide, aluminum indium gallium arsenide, aluminum gallium arsenide, aluminum gallium arsenide phosphide, gallium arsenide, gallium arsenide phosphide, and indium gallium arsenide phosphide.

3. The light emitting diode according to claim 2, wherein: The doping material of each current diffusion layer comprises silicon or tellurium.

4. The light emitting diode according to claim 3, wherein: The high doping concentration of the upper and lower adjacent current diffusion layers is about 0.9 to 3.5E18 / cm 3 , low doping concentration of about 0.9 ~ 3.5E17 / cm 3 .

5. The light emitting diode according to claim 1, wherein: Among the current diffusion layers, the thickness of the lower current diffusion layer is thicker than that of the adjacent upper current diffusion layer.

6. The light emitting diode according to claim 5, wherein: The thickness of each current diffusion layer is b + a×(N - 1), where N is the total number of the current diffusion layers, N is a positive integer between 1 and 1000, b is the thickness of the first layer among the current diffusion layers, 0 < b < 10 microns, and a is the thickness increase of each layer among the current diffusion layers, 0 < a < 10 microns.

7. A light-emitting diode, comprising: a substrate; and a semiconductor epitaxial structure disposed on the substrate, comprising: a semiconductor composite layer; and a plurality of current diffusion layers disposed in the semiconductor composite layer, in, wherein the thickness of the lower current diffusion layer is thicker than that of the adjacent upper current diffusion layer.

8. The light emitting diode according to claim 7, wherein: The thickness of each current diffusion layer is b + a×(N - 1), where N is the total number of the current diffusion layers, N is a positive integer between 1 and 1000, b is the thickness of the first layer among the current diffusion layers, 0 < b < 10 microns, and a is the thickness increase of each layer among the current diffusion layers, 0 < a < 10 microns.

9. The light-emitting diode according to claim 7, wherein the material of each current diffusion layer is selected from one of the group consisting of indium gallium phosphide, aluminum gallium indium phosphide, aluminum indium phosphide, indium gallium arsenide, aluminum indium gallium arsenide, aluminum gallium arsenide, aluminum gallium arsenide phosphide, gallium arsenide, gallium arsenide phosphide, and indium gallium arsenide phosphide.

10. The light emitting diode according to claim 7, wherein: Among the current diffusion layers, the doping concentrations of two adjacent current diffusion layers alternate between high and low.

11. The light emitting diode according to claim 10, wherein: The doping material of each current diffusion layer comprises silicon or tellurium.

12. The light emitting diode according to claim 11, wherein: The high doping concentration of the upper and lower adjacent current diffusion layers is about 0.9 to 3.5E18 / cm 3 , low doping concentration of about 0.9 ~ 3.5E17 / cm 3 .

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