CN112993110B - Light-emitting diode - Google Patents

Light-emitting diode Download PDF

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Publication number
CN112993110B
CN112993110B CN201911304255.6A CN201911304255A CN112993110B CN 112993110 B CN112993110 B CN 112993110B CN 201911304255 A CN201911304255 A CN 201911304255A CN 112993110 B CN112993110 B CN 112993110B
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light
semiconductor layer
emitting
electrode
layer
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CN112993110A (en
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闫春辉
蒋振宇
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Naweilang Technology Shenzhen Co ltd
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Shenzhen Third Generation Semiconductor Research Institute
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Priority to PCT/CN2020/137282 priority patent/WO2021121334A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of group III and group V of the periodic system
    • H01L33/32—Materials of the light emitting region containing only elements of group III and group V of the periodic system containing nitrogen
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
    • H01L33/38—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
    • H01L33/38—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape
    • H01L33/387—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape with a plurality of electrode regions in direct contact with the semiconductor body and being electrically interconnected by another electrode layer

Abstract

The application discloses a light emitting diode includes: a substrate; the light-emitting epitaxial layer comprises a first semiconductor layer, an active light-emitting layer and a second semiconductor layer which are sequentially stacked on the substrate; and a first electrode and a second electrode electrically connected to the first semiconductor layer and the second semiconductor layer, respectively. The projections of the first electrode and the second electrode on the substrate are staggered with each other, the sum of the shortest spacing distances between the projection of any luminous point on the substrate in at least part of the luminous region of the luminous epitaxial layer and the projections of the first electrode on the substrate and the second electrode on the substrate is not more than 80 microns, the ratio of the effective luminous area to the total area of the luminous epitaxial layer is not more than 65%, and the first semiconductor layer and the second semiconductor layer are both made of materials based on an aluminum gallium nitride system. Through the mode, the uniformity of current distribution can be effectively improved, the lumen density and the lumen efficiency of the light emitting diode are further improved, and the lumen cost is reduced.

Description

Light-emitting diode
Technical Field
The application relates to the field of semiconductors, in particular to a light-emitting diode.
Background
The light emitting diode is a solid element for converting electric energy into light, has the advantages of small volume, high efficiency, long service life and the like, and is widely applied to the fields of traffic indication, outdoor full color display and the like. In particular, the semiconductor solid-state lighting can be realized by using a high-power light emitting diode, which has caused the revolution of the human lighting history, and thus the semiconductor solid-state lighting becomes a research hotspot in the field of electronics at present.
At present, the current of the light emitting diode is generally injected into the active light emitting layer by a lateral diffusion method, and the lateral diffusion method has a natural characteristic of non-uniform current distribution, which results in an excessive current density in a local area. Excessive current density in local areas tends to cause two problems:
1. the local current is too large, so that the electro-optic conversion efficiency is easily reduced, and the lumen efficiency and the lumen density are reduced;
2. local overheating is easily caused by excessive local current, the service life and the reliability of the light emitting diode are reduced, heat dissipation needs to be realized through a complex packaging design, and the lumen cost is increased.
Disclosure of Invention
The application provides a light emitting diode, can improve current distribution homogeneity to make light emitting diode can bear higher operating current, and then promote light emitting diode's lumen efficiency and lumen density, and reduce lumen cost.
In one aspect, the present application provides a light emitting diode, including: a substrate; the light-emitting epitaxial layer comprises a first semiconductor layer, an active light-emitting layer and a second semiconductor layer which are sequentially stacked on the substrate; a first electrode electrically connected to one of the first semiconductor layer and the second semiconductor layer, and a plurality of second electrodes electrically connected to the other of the first semiconductor layer and the second semiconductor layer; the first electrode is a surface electrode, projections of the second electrodes on the substrate are arranged in the projections of the first electrodes on the substrate at intervals, the sum of the shortest spacing distances between the projection of any light-emitting point in at least part of the light-emitting area of the light-emitting epitaxial layer on the substrate and the projections of the two adjacent second electrodes on the substrate is not more than 80 micrometers, the proportion between the effective light-emitting area and the total area of the light-emitting epitaxial layer is not more than 65%, and the first semiconductor layer and the second semiconductor layer are both made of materials based on an aluminum gallium nitride system.
In another aspect, the present application provides a light emitting diode, including: a substrate; the light-emitting epitaxial layer comprises a first semiconductor layer, an active light-emitting layer and a second semiconductor layer which are sequentially stacked on the substrate; a first electrode electrically connected to one of the first semiconductor layer and the second semiconductor layer, and a plurality of second electrodes electrically connected to the other of the first semiconductor layer and the second semiconductor layer; the first electrode is a surface electrode, projections of the second electrodes on the substrate are arranged in the projections of the first electrodes on the substrate at intervals, the shortest spacing distance between every two adjacent second electrodes is not more than 80 micrometers, the proportion between the effective light-emitting area and the total area of the light-emitting epitaxial layer is not more than 65%, and the first semiconductor layer and the second semiconductor layer are both made of materials based on an aluminum gallium nitride system.
The beneficial effect of this application is: in contrast to the prior art, the present application sets the sum L1+ L2 of the shortest distance of the light emitting diode based on the aluminum gallium nitride material system to be less than 80 μm and sets the ratio between the effective light emitting area and the total area of the light emitting epitaxial layer to be less than 65% according to the change rule of the operating voltage VF with the sum L1+ L2 of the projection of any light emitting point on the substrate in at least part of the light emitting area of the light emitting epitaxial layer and the projection of the first electrode on the substrate and the projection of the second electrode on the substrate under different operating currents at the expense of the effective light emitting area. Under the size and proportion range, the uniformity of current distribution can be effectively improved, so that the light-emitting diode can bear higher working current, and the lumen efficiency and the lumen density of the light-emitting diode are further improved. Meanwhile, the service life and the reliability of the light-emitting diode are high, the heat dissipation is carried out without complex packaging design, and the lumen cost of the light-emitting diode is reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts. Wherein:
FIG. 1 is a top view of a light emitting diode according to a first embodiment of the present application;
FIG. 2 is a schematic partial cross-sectional view taken along the line A1-A1 of FIG. 1;
FIG. 3 is a graph illustrating the variation of the operating voltage of a blue LED based on the GaN material system with different operating currents according to L1+ L2, which uses the structure shown in FIG. 1;
FIG. 4 is a graph illustrating the photoelectric conversion efficiency of a blue LED based on a GaN material system with the structure of FIG. 1 varying with L1+ L2 at different operating currents;
FIG. 5 is a top view of a light emitting diode according to a second embodiment of the present application;
FIG. 6 is a schematic partial cross-sectional view taken along the line A2-A2 of FIG. 5;
FIG. 7 is a top view of a light emitting diode according to a third embodiment of the present application;
FIG. 8 is a top view of a light emitting diode according to a fourth embodiment of the present application;
FIG. 9 is a schematic partial cross-sectional view taken along the line B1-B1 of FIG. 8;
FIG. 10 is a graph illustrating the operating voltage of a blue LED based on the GaN material system using the structure of FIG. 8 as a function of M1+ M2;
FIG. 11 is a top view of a light emitting diode according to a fifth embodiment of the present application;
FIG. 12 is a schematic partial cross-sectional view taken along line B2-B2 of FIG. 11;
FIG. 13 is a top view of a light emitting diode according to a sixth embodiment of the present application;
FIG. 14 is a schematic partial cross-sectional view taken along direction B3-B3 of FIG. 13;
FIG. 15 is a top view of a light emitting diode according to a seventh embodiment of the present application;
FIG. 16 is a schematic partial cross-sectional view taken along direction B4-B4 of FIG. 15.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
As shown in fig. 1 and 2, the light emitting diode according to the first embodiment of the present application is a light emitting diode of a front-mount structure, and includes a substrate 11, a light emitting epitaxial layer 12, a first electrode 13, and a second electrode 14. The light-emitting epitaxial layer 12 is further formed by sequentially stacking a first semiconductor layer 121, an active light-emitting layer 122, and a second semiconductor layer 123 on the substrate 11. In the present embodiment, the substrate 11 may be made of, for example, sapphire, SiC, GaN, AlN, silicon, or other suitable material. The first semiconductor layer 121 is an N-type semiconductor layer, and the corresponding first electrode 13 is also referred to as an N-type electrode. The second semiconductor layer 123 is a P-type semiconductor layer, and the corresponding second electrode 14 is also referred to as a P-type electrode. In other embodiments, the first semiconductor layer 121 and the second semiconductor layer 123 may be a single layer or a multi-layer structure of any other suitable material having different conductivity types.
Further, as shown in fig. 1 and 2, in the present embodiment, the first electrode 13 and the second electrode 14 are stripe-shaped electrodes, and the projection of the first electrode 13 on the substrate 11 and the projection of the second electrode 14 on the substrate 11 are shifted from each other. Specifically, in the present embodiment, the first electrode 13 and the second electrode 14 are finger electrodes extending along the first direction D1 and spaced from each other along the second direction D2 perpendicular to the first direction D1, respectively, so that the projections of the two on the substrate 11 are offset from each other. The first electrode 13 and the second electrode 14 further connect the first pad 15 and the second pad 16, and further, are connected to an external circuit through the first pad 15 and the second pad 16.
Further, grooves 124 are disposed on the second semiconductor layer 123 and the active light emitting layer 122, and the grooves 124 divide the second semiconductor layer 123 and the active light emitting layer 122 into a plurality of Mesa structures (Mesa)125 arranged in an array with a first direction D1 and a second direction D2 spaced apart from each other and expose a portion of the first semiconductor layer 121.
In the present embodiment, the first electrode 13 and the second electrode 14 are respectively disposed in the trenches 124 on both sides of the mesa structure 125. The first electrode 13 is disposed on the first semiconductor layer 121 and electrically connected to the first semiconductor layer 121, for example, in the embodiment, the first electrode 13 is electrically connected to the first semiconductor layer 121 by directly contacting.
The mesa structure 125 and the first semiconductor layer 121 exposed by the first electrode 13 are further covered with an insulating layer 17, the insulating layer 17 extends along the sidewall of the mesa structure 125 to the top of the mesa structure 125 and at least partially exposes the second semiconductor layer 123 on the top of the mesa structure 125, and the current diffusion layer 18 is electrically connected to the second semiconductor layer 123. The current spreading layer 18 further extends into the trench 124 and is electrically isolated from the first semiconductor layer 121 and the active light emitting layer 122 by the insulating layer 17. The second electrode 14 is disposed on the current diffusion layer 18 located in the trench 124, and is electrically connected to the second semiconductor layer 123 through the current diffusion layer 18.
In other embodiments, the first electrode 13 and the second electrode 14 may also be electrically connected to the first semiconductor layer 121 and the second semiconductor layer 123 by other means, including but not limited to other means described below.
With the above structure, a current formed of electrons is injected from the first electrode 13 into the first semiconductor layer 121, diffused laterally along the first semiconductor layer 121 and injected into the active light emitting layer 122, and a current formed of holes is injected from the second electrode 14 into the second semiconductor layer 123 through the current diffusion layer 18, diffused laterally along the current diffusion layer 18 and the second semiconductor layer 123 and injected into the active light emitting layer 122. The electrons and holes undergo radiative recombination within the active light emitting layer 122 and generate photons, thereby forming light emission. Further, as shown in fig. 2, the cross section of the mesa structure 125 along the second direction D2 is trapezoidal, so that the light generated by the active light emitting layer 122 can exit from the inclined sidewall of the mesa structure 125, thereby improving the light extraction efficiency. In the present embodiment, the insulating layer 17 is made of a transparent dielectric material (e.g., SiO) 2 ) And the current spreading layer 18 is made of a transparent conductive material (e.g., ITO). Insulating layer 17 further provides water oxygen protection and electrical isolation for mesa structure 125.
As can be seen from the above structure, the distance over which the current in the light-emitting epitaxial layer 12 laterally spreads is determined by the lateral distance between the first electrode 13 and the second electrode 14. In the related art, the lateral spacing between the first electrode 13 and the second electrode 14 is set too large, resulting in poor uniformity of current density distribution of current injected into the active light emitting layer 122, thereby causing the problems described in the background art above.
In the present embodiment, the shortest distance between the projection of any one of the light-emitting points a in the at least partial light-emitting region of the light-emitting epitaxial layer 12 on the substrate 11 and the projection of the first electrode 13 on the substrate 11 is L1, and the shortest distance between the projection of the second electrode 14 on the substrate 11 is L2. The sum of the two shortest separation distances is L1+ L2, and the sum of the shortest separation distances L1+ L2 is determined by the lateral spacing between the first electrode 13 and the second electrode 14.
Due to the existence of the trench 124, the first electrode 13 and/or the second electrode 14, the effective light emitting area of the light emitting epitaxial layer 12 is smaller than the total area of the light emitting epitaxial layer 12, and the smaller the lateral distance between the first electrode 13 and the second electrode 14 is, the larger the number of the first electrode and the second electrode which need to be laid under the same chip area is, the larger the loss of the effective light emitting area is, so in order to ensure the maximization of the effective light emitting area, the lateral distance between the first electrode 13 and the second electrode 14 is set to be as large as possible, and is generally larger than the lateral diffusion length of the current. However, through a lot of experiments, by reasonably setting the sum of the shortest separation distances L1+ L2 and the loss of the effective light-emitting area, the applicant of the present application makes the performance improvement yield of the light-emitting diode due to the reduction of the lateral distance far greater than the loss caused by the sacrifice of the effective light-emitting area, and simultaneously ensures that the first electrode 13 and the second electrode 14 can bear relatively large working current, thereby greatly improving the performance of the light-emitting diode.
The reasonable arrangement between the sum of the shortest separation distances L1+ L2 and the ratio Se/Sa of the effective light-emitting area Se of the light-emitting epitaxial layer to the total area Sa will be described below in conjunction with the change rule of the operating voltage VF and the photoelectric conversion efficiency WPE with the sum of the shortest separation distances L1+ L2 under different operating currents in different material systems. Wherein the effective light emitting area Se is equal to the total area Sa minus a non-light emitting area due to the presence of the trenches 124, the first and/or second electrodes 13 and 14, the pads, and the like.
First, fig. 3 shows the variation curve of the operating voltage of the blue led with the first semiconductor layer and the second semiconductor layer based on the gan material along with L1+ L2 at different operating currents.
In this application, by blue light emitting diode is meant a light emitting diode with a peak wavelength in operation between 440nm and 480 nm. By gallium nitride material system is meant that in the material system, the molar proportion of nitrogen in anions is not less than 90%, and the molar proportion of gallium in cations is not less than 90%.
In the present application, the conventional led with a size of 425 micrometers by 750 micrometers and a Se/Sa of 85% and L1+ L2 as a reference sample, the first electrode 13 and the second electrode 14 extend along the length of 750 micrometers, and the leds with L1+ L2 as 72, 60, 50, 40, 30 and 20 micrometers as comparison samples are used to fit the variation rule of the operating voltage VF and the photoelectric conversion efficiency WPE with L1+ L2. In order to ensure that the first electrode 13 and the second electrode 14 have sufficient line widths to enable the first electrode 13 and the second electrode 14 to bear a sufficiently large operating current, the Se/Sa of each of the comparative samples is set to be 75%, 67%, 60%, 55%, 40%, and 25%, respectively, further at the expense of an effective light-emitting area.
In fig. 3, in order to more clearly show the effect of the change in the operating voltage, the operating voltage at each operating current is normalized at a point L1+ L2 equal to 100 micrometers, and the change rule of the normalized operating voltage VF is shown in the process that L1+ L2 gradually decreases from 100 micrometers.
As shown in fig. 3, from 100 micrometers, the normalized operating voltage VF decreases slowly with the decrease of L1+ L2, and after decreasing to 72 micrometers, the decreasing tendency of the normalized operating voltage VF increases significantly, and the decreasing slope is larger the current.
The falling tendency of the normalized operating voltage VF becomes gentle after L1+ L2 is further decreased to 60 micrometers, and the falling tendency becomes further gentle after being decreased to 50 micrometers. As L1+ L2 decreases further to 40 microns, the normalized operating voltage VF at partial operating current goes from a downward trend to an upward trend and all goes to an upward trend after decreasing to 30 microns. After further reduction to 20 microns of L1+ L2, the overall normalized operating voltage VF is still lower than the normalized operating voltage VF at the 72 micron and 100 micron locations, although it rises as compared to the 30 micron location.
Further, fig. 4 shows the change curve of the photoelectric conversion efficiency WPE of the blue light emitting diode with L1+ L2 at different operating currents. In order to more clearly show the change effect of the photoelectric conversion efficiency WPE, the photoelectric conversion efficiency WPE at each operating current is normalized at a position where L1+ L2 is 100 micrometers, and the change rule of the normalized photoelectric conversion efficiency WPE is measured in the process where L1+ L2 is gradually decreased from 100 micrometers.
As shown in fig. 4, from 100 μm, at a small operating current, the normalized photoelectric conversion efficiency WPE shows a downward trend as L1+ L2 decreases, whereas only at a large operating current, the normalized photoelectric conversion efficiency shows a gradual upward trend as L1+ L2 decreases. After reduction to 72 microns, the normalized photoelectric conversion efficiency at each operating current showed an upward trend with decreasing L1+ L2, and the higher the current, the larger the rising slope.
As L1+ L2 further decreased to 60 microns, the upward trend of the normalized photoelectric conversion efficiency decreased, and after 50 microns, the normalized photoelectric conversion efficiency began to slowly decrease. The decreasing trend of the normalized photoelectric conversion efficiency worsened as L1+ L2 further decreased to 40 microns, and the decreasing area of the normalized photoelectric conversion efficiency further worsened after 30 microns, but the overall was still greater than the normalized photoelectric conversion efficiency at the 73 micron location. As L1+ L2 was further reduced to 20 microns, the normalized photoelectric conversion efficiency at the bulk operating current was still greater than the normalized photoelectric conversion efficiency at the 100 micron position.
As can be seen from fig. 3 and 4, as L1+ L2 decreases below 60 microns, although the ratio Se/Sa of the effective light-emitting area Se to the total area Sa of the light-emitting diode decreases to 67%, the operating voltage is significantly lower and the photoelectric conversion efficiency is significantly higher than that of the conventional light-emitting diode. Therefore, when the voltage of L1+ L2 is reduced to be less than 60 micrometers, the performance improvement benefit of the LED due to the reduction of L1+ L2 is far greater than the loss caused by the sacrifice of the effective light-emitting area, and the performance of the LED chip is greatly improved.
Therefore, in a specific embodiment, the sum of the shortest separation distances L1+ L2 is set to not more than 60 μm, and the ratio Se/Sa between the effective light-emitting area of the light-emitting epitaxial layer 12 and the total area is set to not more than 67%. Under the size and proportion range, the uniformity of current distribution can be effectively improved, so that the light-emitting diode can bear higher working current, and the lumen efficiency and the lumen density of the light-emitting diode are further improved. Meanwhile, the service life and the reliability of the light emitting diode are high, the heat dissipation is carried out without a complex packaging design, and the lumen cost of the light emitting diode is reduced.
Further, the sum of the shortest separation distances L1+ L2 may be set to be between 30 microns and 60 microns, and the ratio Se/Sa between the effective light emitting area of the light emitting epitaxial layer and the total area may be set to be between 40% and 67%. Further, the sum of the shortest separation distances L1+ L2 may be set to be between 30 micrometers and 50 micrometers, and the ratio Se/Sa between the effective light emitting area of the light emitting epitaxial layer and the total area may be set to be between 40% and 60%.
Still further, it is also possible to set the sum of shortest spacing distances L1+ L2 to be less than 20 micrometers, the ratio Se/Sa between the effective light emitting area of the light emitting epitaxial layer and the total area to be less than 25%, or the sum of shortest spacing distances L1+ L2 to be between 20 micrometers and 30 micrometers, the ratio Se/Sa between the effective light emitting area of the light emitting epitaxial layer and the total area to be between 25% and 40%, or the sum of shortest spacing distances L1+ L2 to be between 30 micrometers and 40 micrometers, the ratio Se/Sa between the effective light emitting area of the light emitting epitaxial layer and the total area to be between 40% and 55%, or the sum of shortest spacing distances L1+ L2 to be between 40 micrometers and 50 micrometers, and the ratio Se/Sa between the effective light emitting area of the light emitting epitaxial layer and the total area to be between 55% and 60%, according to actual use requirements (ii) a Or the sum of the shortest separation distances L1+ L2 is set to be between 50 micrometers and 60 micrometers, and the ratio Se/Sa between the effective light-emitting area of the light-emitting epitaxial layer and the total area is set to be between 60% and 67%. It is noted that, as used herein, the term "between" and "an" is intended to include both of the recited values.
In the present embodiment, at least a portion of the light-emitting region constrained by the above dimensions and proportions covers the entire light-emitting region of the light-emitting epitaxial layer 12, i.e., all of the mesa structures 125. In other embodiments, at least a portion of the light emitting area may be configured to include one or more mesa structures 125. In other embodiments, the area ratio of the set of all at least part of the light-emitting regions satisfying the above-described constraint conditions to the entire light-emitting region on the light-emitting epitaxial layer 12 may be further not less than 50%, 60%, 70%, 80%, 90%.
Further, as shown in fig. 3 and 4, the higher the operating current is, the more significant the effect of improving the performance of the light emitting diode is. Therefore, the constraint manner of the present embodiment with respect to the sum of the shortest separation distances L1+ L2 and the ratio Se/Sa between the effective light-emitting area and the total area is particularly suitable for a high-power light-emitting diode. In one embodiment, the average current density J of the LED during operation is set to not less than 0.5A/mm 2 . In other embodiments, the average current density J of the LED during operation can be further set to not less than 0.75, 1, 1.5, 2, 3, 5, 10, 20A/mm 2 . Further, in order to accommodate the need for a large light emitting area of a high power light emitting diode, the sum of the numbers of the first electrodes 13 and the second electrodes 14 is set to not less than 5, 7, 9, or 11.
It is noted that the above dimensional and scale definitions apply equally to light emitting diodes based on other peak wavelengths of the gallium nitride material system, such as 365nm-400nm, 400nm-440nm, 440nm-480nm, 480nm-540nm, 540nm-560nm, 560nm-600nm, or 600nm-700 nm.
It is to be noted that the sum L1+ L2 of the shortest separation distances in the present embodiment is actually limited by the shortest separation distance between the projections of the first electrode 13 and the second electrode 14 on the substrate 11, and therefore in the present embodiment and other embodiments, the shortest separation distance between the projections of the first electrode 13 and the second electrode 14 on the substrate 11 can be constrained by utilizing the above-mentioned dimensional definition. Specifically, the shortest separation distance between the projections of the first electrode 13 and the second electrode 14 on the substrate 11 can be set to not more than 60, 50, 40, 30, and 20 micrometers according to actual needs.
In conclusion, the arrangement mode effectively improves the uniformity of current distribution, so that the light-emitting diode can bear higher working current, and the lumen efficiency and the lumen density of the light-emitting diode are improved. Meanwhile, the service life and the reliability of the light emitting diode are high, the heat dissipation is carried out without a complex packaging design, and the lumen cost of the light emitting diode is reduced.
Further, the above design concept can be applied to light emitting diodes using other material systems with the above structure, such as aluminum gallium nitride material system, indium gallium nitride material system, and aluminum gallium indium phosphide material system. Wherein, the aluminum gallium nitride material system means that in the material system, the molar ratio of nitrogen element in anion is not less than 90%, the molar ratio of aluminum element and gallium element in cation is not less than 90%, and the molar ratio of aluminum element in cation is not less than 10%. The indium gallium nitride material system means that in the material system, the molar ratio of nitrogen element in anion is not less than 90%, the molar ratio of indium element and gallium element in cation is not less than 90%, and the molar ratio of indium element in cation is not less than 10%. The aluminum gallium indium phosphide system means that in the material system, the molar proportion of phosphorus element in anions is not less than 90%, and the molar proportion of aluminum element, indium element and gallium element in cations is not less than 90%.
Specific design parameters of L1+ L2 and Se/Sa of the light emitting diode based on the indium gallium nitride material system and the aluminum gallium indium phosphide material system and adopting the structure are given below.
In the indium gallium nitride material system, the sum of the shortest spacing distances L1+ L2 is set to be not more than 80 micrometers, and the ratio Se/Sa of the effective light-emitting area Se to the total area Sa is set to be not more than 72%. Further, the sum of the shortest spacing distances L1+ L2 is set to be between 30 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa is set to be between 40% and 67%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 60 micrometers and 80 micrometers, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa is set to be between 67% and 72%.
Further, the sum of the shortest separation distances L1+ L2 is set to be between 30 micrometers and 50 micrometers, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa is set to be between 40% and 60%.
Still further, the following settings can be made according to actual situations: the sum of the shortest separation distances L1+ L2 is set to less than 20 microns, and the ratio Se/Sa of the effective light-emitting area Se of the light-emitting epitaxial layer to the total area Sa is set to less than 25%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 20 microns and 30 microns, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layers to the total area Sa is set to be between 25% and 40%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 30 micrometers and 40 micrometers, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa is set to be between 40% and 55%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 40 microns and 50 microns, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layers to the total area Sa is set to be between 55% and 60%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 50 micrometers and 60 micrometers, and the ratio of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa, Se/Sa, is set to be between 60% and 67%.
The peak wavelength of a light emitting diode based on an indium gallium nitride material system during operation may be between 400nm and 440nm, 440nm and 480nm, 480nm and 540nm, 540nm and 560nm, 560nm and 600nm, 600nm and 700nm, or 700nm and 850 nm.
Under the aluminum indium gallium phosphide material system, the sum L1+ L2 of the shortest spacing distances is set to be not more than 100 micrometers, and the ratio Se/Sa of the effective light-emitting area Se to the total area Sa is set to be not more than 75%. Further, the sum of the shortest spacing distances L1+ L2 is set to be between 30 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa is set to be between 40% and 67%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 60 micrometers and 80 micrometers, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa is set to be between 67% and 72%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 80 and 100 micrometers, and the ratio Se/Sa of the effective light-emitting area Se of the light-emitting epitaxial layer to the total area Sa is set to be between 72 and 75 percent
Further, the sum of the shortest separation distances L1+ L2 is set to be between 30 micrometers and 50 micrometers, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layers to the total area Sa is set to be between 40% and 60%.
Still further, the following settings can be made according to actual situations: the sum of the shortest separation distances L1+ L2 is set to less than 20 microns, and the ratio Se/Sa of the effective light-emitting area Se of the light-emitting epitaxial layer to the total area Sa is set to less than 25%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 20 micrometers and 30 micrometers, and the ratio of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa, Se/Sa, is set to be between 25% and 40%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 30 micrometers and 40 micrometers, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa is set to be between 40% and 55%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 40 micrometers and 50 micrometers, and the ratio Se/Sa of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa is set to be between 55% and 60%. Alternatively, the sum of the shortest separation distances L1+ L2 is set to be between 50 micrometers and 60 micrometers, and the ratio of the effective light emitting area Se of the light emitting epitaxial layer to the total area Sa, Se/Sa, is set to be between 60% and 67%.
The peak wavelength of the light-emitting diode based on the aluminum indium gallium phosphide material system can be 560nm-600nm, 600nm-700nm, 700nm-850nm, 850nm-980nm, 980nm-1300nm or 1300nm-1600nm during operation.
It is noted that other parameters of the front-loading led based on the ingan material system and the alinga phosphide material system can be set with reference to the front-loading led based on the gan material system. In addition, the dimensional and proportional limitations under the various material systems are equally applicable to other light emitting diodes in a forward mounted configuration.
As shown in fig. 5 and 6, a light emitting diode according to a second embodiment of the present application is a modification of the front-mount structure shown in fig. 1 and 2, and includes a substrate 21, a light emitting epitaxial layer 22, a first electrode 23, and a second electrode 24. The light-emitting epitaxial layer 22 is further formed by sequentially stacking a first semiconductor layer 221, an active light-emitting layer 222, and a second semiconductor layer 223 on the substrate 21. Grooves 224 are disposed on the second semiconductor layer 223 and the active light emitting layer 222, the grooves 224 divide the second semiconductor layer 223 and the active light emitting layer 222 into a plurality of mesa structures 225 spaced apart from each other in the second direction D2 'and integrally disposed in the first direction D1', and expose a portion of the first semiconductor layer 221. The first direction D1 'is an extending direction of the first electrode 23 and the second electrode 24, and the second direction D2' is a spacing direction of the first electrode 23 and the second electrode 24. The first electrode 23 and the second electrode 24 are further connected to pads 25 and 26, respectively.
The main difference between the light emitting diode of the present embodiment and the light emitting diode shown in fig. 1 and 2 is that the second electrode 24 is directly disposed on the second semiconductor layer 123 on top of the mesa structure 225 and electrically connected to the second semiconductor layer 124.
In the present embodiment, the second electrode 24 is electrically connected to the second semiconductor layer 223 through the current diffusion layer 27 provided thereunder. The current diffusion layer 27 mainly aims to improve the uniformity of current diffusion in the second semiconductor layer 223, and a transparent material (for example, ITO) having a conductivity higher than that of the second semiconductor layer 223 may be used.
Further, as shown in fig. 5 and 6, the light emitting diode of the present embodiment further includes a current blocking layer 28 disposed directly below the second electrode 24 and between the current diffusion layer 27 and the second semiconductor layer 223. Since the first electrode 23 and the second electrode 24 are generally made of metal materials, light generated from the light emitting epitaxial layer 22 cannot pass through the second electrode 24. The current blocking layer 28 prevents current from being directly injected into the light-emitting epitaxial layer 22 right below the second electrode 24 from the second electrode 24, thereby reducing the amount of light emitted by the second electrode 24 and improving the lumen efficiency.
The light emitting diode in this embodiment further comprises a transparent dielectric layer 29 (e.g., SiO) covering the sloped sidewalls of the mesa structure 225 2 ). The transparent dielectric layer 29 serves to protect the mesa structure 225 from water and oxygen and to electrically isolate it.
As shown in fig. 7, the light emitting diode according to the third embodiment of the present invention is different from the light emitting diode shown in fig. 5 and 6 in that a portion of the second electrode 34 is disposed in the trench 324 in the form of a trunk electrode 341, and another portion of the second electrode 34 extends to the top of the mesa structure 325 in the form of a branch electrode 342 and is electrically connected to the second semiconductor layer (not shown).
The sum L1'+ L2' of the shortest separation distance between the projection of the first electrode and the projection of the second electrode on the substrate and the sum a 'of any light-emitting point a' of at least a part of the light-emitting region of the light-emitting diode in the second and third embodiments described above, and the shortest separation distance between the projections of the first electrode and the second electrode on the substrate are also constrained by the above dimensions, while the ratio between the effective light-emitting area and the total area of the light-emitting epitaxial layer is also constrained by the above ratio.
Further, the above design concept of the light emitting diode based on the forward mounting structure is also applicable to the light emitting diode based on the vertical and inverted mounting structure.
As shown in fig. 8 and 9, the light emitting diode according to the third embodiment of the present application includes a substrate 41, a light emitting epitaxial layer 42, a first electrode 43, and a second electrode 44. The light-emitting epitaxial layer 42 further includes a first semiconductor layer 421, an active light-emitting layer 422, and a second semiconductor layer 423 which are sequentially stacked over the substrate 41. In the present embodiment, the substrate 41 may be made of a conductive material such as Si, Ge, Cu, CuW, or the like. The first semiconductor layer 421 is a P-type semiconductor layer, and the corresponding first electrode 43 is also referred to as a P-type electrode. The second semiconductor layer 423 is an N-type semiconductor layer, and the corresponding second electrode 44 is also referred to as an N-type electrode. In other embodiments, the first semiconductor layer 421 and the second semiconductor layer 423 may be a single layer or a multi-layer structure of any other suitable material having different conductivity types.
Further, as shown in fig. 8 and 9, the first electrode 43 is a planar electrode, the plurality of second electrodes 44 are respectively strip-shaped electrodes, and the projections on the substrate 41 fall inside the projections of the first electrodes 43 on the substrate 41 and are arranged at intervals from each other. Specifically, in the present embodiment, the second electrodes 44 are respectively finger electrodes extending along the first direction D1 ″ and disposed at intervals from each other along the second direction D2 ″ perpendicular to the first direction D1 ″ such that the projections of the second electrodes 44 on the substrate 41 are disposed at intervals from each other along the second direction D2 ″. The first electrode 43 and the second electrode 44 are further connected to a first pad (not shown) and a second pad 46, and are further connected to an external circuit via the first pad and the second pad 46.
Further, in the present embodiment, the light emitting diode is a vertical light emitting diode, and the second electrode 44 and the first electrode 43 are respectively located on two opposite sides of the light emitting epitaxial layer 420. The second electrode 44 is disposed on a side of the second semiconductor layer 423 away from the active light emitting layer 422, and the second electrode 44 is electrically connected to the second semiconductor layer 423, for example, in this embodiment, the second electrode 44 is electrically connected to the second semiconductor layer 423 in a direct contact manner.
The first electrode 43 is disposed on a side of the substrate 41 away from the light-emitting epitaxial layer 42, and is electrically connected to the first semiconductor layer 421 through the substrate 41. Further, a metal bonding layer 47 and a reflector 48 may be further disposed between the substrate 41 and the first semiconductor layer 421, the reflector 48 is configured to reflect light generated by the active light emitting layer 422, so that light is emitted from the side where the second semiconductor layer 423 is located, and the metal bonding layer 47 is configured to improve the adhesion of the light emitting epitaxial layer 42.
In the present embodiment, the projection of the second electrode 44 on the substrate 41 and the projection of the first electrode 43 on the substrate 41 overlap each other, and further fall within the projection of the first electrode 43 on the substrate 41. It is to be noted here that the projection of the first electrode 43 onto the substrate 41 referred to in the present application includes both the projection of the first electrode 43 onto the substrate 41 shown in fig. 9 and the subsequent projection of the first electrode onto the substrate shown in fig. 15-16.
With the above structure, a current formed of holes is directly injected from the first electrode 43 into the active light emitting layer 42 in the lamination direction thereof via the substrate 41, the metal bonding layer 47, and the mirror 48, and a current formed of electrons is injected from the second electrode 44 into the second semiconductor layer 43, and is laterally diffused along the second semiconductor layer 423 and injected into the active light emitting layer 422. The electrons and holes radiatively recombine within the active light emitting layer 422 and generate photons, which in turn generate light.
As can be seen from the above structure, the distance for the current in the light-emitting epitaxial layer 42 to laterally diffuse is determined by the lateral distance between the adjacent second electrodes 44. In the related art, the lateral spacing between the adjacent second electrodes 44 is set too large, resulting in poor uniformity of current density distribution of current injected into the active light emitting layer 422, thereby causing the problems described in the background art above.
In the present embodiment, the shortest separation distance between the projection of any light-emitting spot B in at least a part of the light-emitting region of the light-emitting epitaxial layer 42 on the substrate 41 and the projections of the two adjacent second electrodes 44 on the substrate 41 is M1 and M2, respectively. The sum of the two shortest separation distances is M1+ M2.
Fig. 10 shows the variation of the operating voltage of the blue led using the structures shown in fig. 8 and 9, wherein the first semiconductor layer and the second semiconductor layer are both based on the gallium nitride system material, with M1+ M2 at different operating currents.
In this embodiment, the variation rule of the operating voltage VF with M1+ M2 is fit by using a vertical led with M1+ M2 being 230 microns and Se/Sa being 75% as a reference sample, and using leds with M1+ M2 being 105, 80, 50, and 30 microns as comparison samples. Further, in order to ensure that the second electrode 34 has a sufficient line width so that the second electrode 34 can withstand a sufficiently large operating current, the Se/Sa of each of the above comparative samples is set to 70%, 65%, 63%, and 45%, respectively, further at the expense of an effective light-emitting area.
The actual voltage was used for the reason that the 230 micron size samples saturated too early at high current and could not be normalized. As can be seen from the figure, at 1A/mm 2 And 2A/mm 2 When the size is reduced to about 100 microns under the high-power current injection, the voltage is sharply reduced. For 5A/mm 2 At very high current injection, the 230 micron size samples had already saturated failure, while the 105, 50 and 30 micron sizes were still working. For 10A/mm 2 At very high current injection, the 230 and 105 micron size samples had already failed in saturation, while the 50 and 30 micron size remained workable.
Therefore, in the present embodiment, the sum M1+ M2 of the shortest spacing distances is set to not more than 100 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to not more than 70%. Under the size and proportion range, the uniformity of current distribution can be effectively improved, so that the light-emitting diode can bear higher working current, and the lumen efficiency and the lumen density of the light-emitting diode are further improved. Meanwhile, the service life and the reliability of the light emitting diode are high, the heat dissipation is carried out without a complex packaging design, and the lumen cost of the light emitting diode is reduced.
Further, the sum of the shortest separation distances M1+ M2 may be further set to be between 30 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa may be set to be between 45% and 60%. Or the sum of the shortest separation distances M1+ M2 is further set to be between 60 and 100 micrometers, and the ratio Se/Sa of the effective light-emitting area Se to the total area Sa is set to be between 60 and 70 percent
Further, the sum of the shortest spacing distances M1+ M2 is set to be less than 20 micrometers and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be less than 38%, or the sum of the shortest spacing distances M1+ M2 is set to be between 20 micrometers and 30 micrometers and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 38% and 45%. Alternatively, the sum of the shortest separation distances M1+ M2 is set to be between 30 micrometers and 40 micrometers, and the ratio Se/Sa of the effective light-emitting area Se to the total area Sa is set to be between 45% and 55%. The sum of the shortest separation distances M1+ M2 is set to be between 40 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 55% and 60%. The sum of the shortest separation distances M1+ M2 is set to be between 60 micrometers and 80 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 60% and 65%. Alternatively, the sum of the shortest separation distances M1+ M2 is set to be between 80 micrometers and 100 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 65% and 70%.
In the present embodiment, the area ratio of the set of all at least part of the light-emitting regions satisfying the above-described constraint conditions to the entire light-emitting region on the light-emitting epitaxial layer 32 may further be not less than 50%, 60%, 70%, 80%, 90%.
Further, the average current density J at the time of operating the light emitting diode is set to not less than 0.5A/mm 2 . In other embodiments, the average current density J of the light emitting diode during operation can be further set to be not less than 1, 1.5, 2, 3, 5, 10, 20A/mm 2 . Further, in order to accommodate the need for a large light emitting area of a high power light emitting diode, the sum of the number of the second electrodes 34 is set to not less than 5, 7, 9, or 11.
Also, the sum M1+ M2 of the shortest separation distances in the present embodiment is actually limited by the shortest separation distance between the projections of the adjacent two second electrodes 44 on the substrate 41, and therefore, in the present embodiment and other embodiments, the shortest separation distance between the projections of the adjacent two second electrodes 44 on the substrate 41 can be constrained by using the above dimensions. Specifically, the shortest separation distance between the projections of the adjacent two second electrodes 44 on the substrate 41 is set to be not more than 100 micrometers.
Furthermore, constraints of aluminum gallium nitride material systems, indium gallium nitride material systems, and aluminum gallium indium phosphide material systems can be given based on a similar manner.
In the aluminum gallium nitride material system, the sum of the shortest spacing distances M1+ M2 is set to not more than 80 μ M, and the ratio Se/Sa of the effective light-emitting area Se to the total area Sa is set to not more than 65%.
Further, the sum of the shortest separation distances M1+ M2 may be further set to be between 30 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa may be set to be between 45% and 60%. Or the sum of the shortest separation distances M1+ M2 is further set to be between 60 micrometers and 80 micrometers, and the ratio Se/Sa of the effective light-emitting area Se to the total area Sa is set to be between 60% and 65%.
Further, the sum of the shortest spacing distances M1+ M2 is set to be less than 20 micrometers and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be less than 38%, or the sum of the shortest spacing distances M1+ M2 is set to be between 20 micrometers and 30 micrometers and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 38% and 45%. Alternatively, the sum of the shortest separation distances M1+ M2 is set to be between 30 micrometers and 40 micrometers, and the ratio Se/Sa of the effective light-emitting area Se to the total area Sa is set to be between 45% and 55%. The sum of the shortest separation distances M1+ M2 is set to be between 40 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 55% and 60%.
In the indium gallium nitride material system, the sum L1+ L2 of the shortest spacing distances is set to be not more than 120 micrometers, and the ratio Se/Sa of the effective light-emitting area Se to the total area Sa is set to be not more than 72%.
Further, the sum of the shortest separation distances M1+ M2 may be further set to be between 30 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa may be set to be between 45% and 60%. Alternatively, the sum of the shortest separation distances M1+ M2 is further set to be between 60 micrometers and 80 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 60% and 65%. Alternatively, the sum of the shortest separation distances M1+ M2 is further set to be between 80 micrometers and 120 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 65% and 72%.
Further, the sum of the shortest spacing distances M1+ M2 is set to be less than 20 micrometers and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be less than 38%, or the sum of the shortest spacing distances M1+ M2 is set to be between 20 micrometers and 30 micrometers and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 38% and 45%. Alternatively, the sum of the shortest separation distances M1+ M2 is set to be between 30 micrometers and 40 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 45% and 55%. The sum of the shortest separation distances M1+ M2 is set to be between 40 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 55% and 60%.
Under an aluminum gallium indium phosphide material system, the sum L1+ L2 of the shortest spacing distances is set to be not more than 150 micrometers, and the ratio Se/Sa of the effective light-emitting area Se to the total area Sa is set to be not more than 75%.
Further, the sum of the shortest separation distances M1+ M2 may be further set to be between 30 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa may be set to be between 45% and 60%. Alternatively, the sum of the shortest separation distances M1+ M2 is further set to be between 60 micrometers and 100 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 60% and 70%. Alternatively, the sum of the shortest separation distances M1+ M2 is further set to be between 100 micrometers and 150 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 65% and 75%.
Further, the sum of the shortest spacing distances M1+ M2 is set to be less than 20 micrometers and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be less than 38%, or the sum of the shortest spacing distances M1+ M2 is set to be between 20 micrometers and 30 micrometers and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 38% and 45%. Alternatively, the sum of the shortest separation distances M1+ M2 is set to be between 30 micrometers and 40 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 45% and 55%. The sum of the shortest separation distances M1+ M2 is set to be between 40 micrometers and 60 micrometers, and the ratio Se/Sa of the effective light emitting area Se to the total area Sa is set to be between 55% and 60%.
It should be noted that the peak wavelength of the aforementioned gan-based vertical led during operation is between 220nm-260nm, 260nm-300nm, 300nm-320nm, or 320nm-365nm, and the peak wavelength of other material systems is the same as that of the above-described forward-mounted led, and will not be described herein again.
In conclusion, the arrangement mode effectively improves the uniformity of current distribution, so that the light-emitting diode can bear higher working current, and the lumen efficiency and the lumen density of the light-emitting diode are improved. Meanwhile, the service life and the reliability of the light emitting diode are high, the heat dissipation is carried out without a complex packaging design, and the lumen cost of the light emitting diode is reduced.
It is noted that the dimensional and scale limitations under the various material systems are equally applicable to other vertical and flip-chip structures of light emitting diodes.
As shown in fig. 11 and 12, a light emitting diode according to a second embodiment of the present application is a modification of the vertical structure light emitting diode shown in fig. 8 and 9. In the present embodiment, the light emitting diode also includes the first electrode 53, the substrate 51, the metal bonding layer 57, the mirror 58, the first semiconductor layer 521, the active light emitting layer 522, the second semiconductor layer 523, and the second electrode 54, which are similar to the light emitting diode shown in fig. 8 and 9. The present embodiment is different from the light emitting diode shown in fig. 8 and 9 in that:
the first semiconductor layer 521, the second semiconductor layer 523, and the active light emitting layer 522 are provided with a trench 524, and the trench 524 is a Mesa structure (Mesa)525 in which the first semiconductor layer 521, the second semiconductor layer 523, and the active light emitting layer 522 are arranged at an interval from each other. Insulating layers 591 and current spreading layers 592 are formed within the sidewalls of the mesa structures 525 and within the exposed regions of the mesa structures 525. The two adjacent second electrodes 54 are respectively disposed in the trenches 524 on both sides of the mesa 525 and are electrically connected to the second semiconductor layer 523 through the current diffusion layer 592. At this time, as shown in fig. 12, the shortest distance between the projection of any one of the light emitting spots B ' on the substrate 51 in at least a partial light emitting region of the light emitting epitaxial layer formed by the first semiconductor layer 521, the second semiconductor layer 523 and the active light emitting layer 522 and the projection of the adjacent two second electrodes 54 on the substrate 51 is M1' and M2', respectively. The sum of the two shortest separation distances is M1'+ M2'.
Further, as shown in fig. 13 and 14, a light emitting diode according to a sixth embodiment of the present application is a further modification of the vertical structure light emitting diode shown in fig. 11 and 12. In the present embodiment, the light emitting diode also includes a first electrode 63, a substrate 61, a metal bonding layer 67, a mirror 68, a first semiconductor layer 621, an active light emitting layer 622, a second semiconductor layer 623, and a second electrode 64 similar to the light emitting diode shown in fig. 11 and 12. In addition, the first semiconductor layer 621, the active light emitting layer 622, and the second semiconductor layer 623 are also divided into mesa structures 625 spaced apart from each other by the trenches 624, and an insulating layer 691 is formed on sidewalls of the mesa structures 625 and exposed regions of the mesa structures 625. The present embodiment is different from the light emitting diode shown in fig. 11 and 12 in that:
a portion of the second electrode 64 is disposed in the trench 624 in the form of a trunk electrode 643, and another portion of the second electrode 64 extends to the top of the mesa 625 in the form of a branch electrode 644, and contacts and is electrically connected to the second semiconductor layer 623. At this time, a point of current injection into the second semiconductor layer 623 is realized by the branch electrode 644. As shown in fig. 14, the shortest separation distances between the projection of any one of the light-emitting spots B ″ on the substrate 61 in at least a partial light-emitting region of the light-emitting epitaxial layer formed by the first semiconductor layer 621, the second semiconductor layer 623 and the active light-emitting layer 622 and the projections of the adjacent two second electrodes 64 on the substrate 61 are M1 ″ and M2', respectively. The sum of the two shortest separation distances is M1 "+ M2".
As shown in fig. 15 and 16, the light emitting diode according to the seventh embodiment of the present invention is a flip chip light emitting diode, and includes a substrate 71, a light emitting epitaxial layer 72, a first electrode 73 and a second electrode 74, where the first electrode 73 is a planar electrode, and the second electrode 74 is plural in number and located on the same side of the light emitting diode. The light-emitting epitaxial layer 72 further includes a first semiconductor layer 721, an active light-emitting layer 722, and a second semiconductor layer 723 which are sequentially stacked over the substrate 71. The first electrode 73 is provided on a side of the second semiconductor layer 723 away from the substrate 71, and is electrically connected to the second semiconductor layer 723. A reflecting mirror 79 is further provided between the first electrode 73 and the second semiconductor layer 723 to reflect light generated by the active light emitting layer 722 to emit light from the side of the substrate 71. The surface of the first electrode 73 is provided with a plurality of grooves 724, and the grooves 724 extend to the first semiconductor layer 721 through the mirror 79, the second semiconductor layer 723, and the active light emitting layer 722. The plurality of second electrodes 74 are respectively disposed in the corresponding recesses 724 and electrically connected to the first semiconductor layer 721. In the present embodiment, the first semiconductor layer 421 is an N-type semiconductor layer (e.g., N-type GaN), and the corresponding second electrode 74 is also referred to as an N-type electrode. The second semiconductor layer 723 is a P-type semiconductor layer (e.g., P-type GaN), and the corresponding first electrode 73 is also referred to as a P-type electrode. In other embodiments, the first semiconductor layer 721 and the second semiconductor layer 723 may be single layer or multilayer structures of any other suitable material having different conductivity types. In the present embodiment, the shortest separation distance between the projection of any one of the light-emitting spots B ' "in at least a partial light-emitting region of the light-emitting epitaxial layer 72 on the substrate 71 and the projections of the two adjacent second electrodes 74 on the substrate 71 is M1 '", M2' ", respectively. The sum of the two shortest separation distances M1'+ M2' ″.
The sum of the two shortest separation distances of the above-mentioned several led structures and other similar structures, M1' + M2', M1 "+ M2" and M1 "+ M2 '", is constrained by the above-mentioned dimensions, while the ratio between the effective light-emitting area and the total area of the light-emitting epitaxial layer is constrained by the above-mentioned ratio.
The above description is only an embodiment of the present application, and is not intended to limit the scope of the present application, and all equivalent structures or equivalent processes performed by the present application and the contents of the attached drawings, which are directly or indirectly applied to other related technical fields, are also included in the scope of the present application.

Claims (19)

1. A light emitting diode, comprising:
a substrate;
the light-emitting epitaxial layer comprises a first semiconductor layer, an active light-emitting layer and a second semiconductor layer which are sequentially stacked on the substrate;
a first electrode electrically connected to one of the first semiconductor layer and the second semiconductor layer, and a plurality of second electrodes electrically connected to the other of the first semiconductor layer and the second semiconductor layer;
wherein the light emitting diode is a vertical light emitting diode or a flip light emitting diode; the first electrode is a face electrode, projections of the second electrodes on the substrate are arranged in the projections of the first electrodes on the substrate at intervals, the sum of the shortest interval distance between the projection of any light-emitting point in at least part of light-emitting areas of the light-emitting epitaxial layer on the substrate and the projections of the two adjacent second electrodes on the substrate is not more than 80 micrometers, the proportion between the effective light-emitting area and the total area of the light-emitting epitaxial layer is not more than 65%, and the first semiconductor layer and the second semiconductor layer are both made of materials based on an aluminum gallium nitride system.
2. The led of claim 1, wherein the peak wavelength of the led during operation is between 220nm-260nm, 260nm-300nm, 300nm-320nm, or 320nm-365 nm.
3. The led of claim 1, wherein the sum of said shortest separation distances is further between 60-80 microns, the ratio between the effective light-emitting area of said light-emitting epitaxial layer and the total area is between 60-65%;
alternatively, the sum of the shortest separation distances is further between 30 and 60 microns, and the ratio between the effective light emitting area of the light emitting epitaxial layer and the total area is between 45 and 60 percent.
4. The light-emitting diode according to claim 1,
the sum of the shortest separation distances is further less than 20 microns, and the ratio of the effective light-emitting area to the total area of the light-emitting epitaxial layer is less than 38%;
the sum of the shortest spacing distances is further between 20 and 30 micrometers, and the ratio of the effective light-emitting area of the light-emitting epitaxial layer to the total area is between 38 and 45 percent;
the sum of the shortest spacing distances is further between 30 and 40 micrometers, and the ratio of the effective light-emitting area of the light-emitting epitaxial layer to the total area is between 45 and 55 percent;
the sum of the shortest separation distances is further between 40 and 60 micrometers, and the ratio of the effective light-emitting area of the light-emitting epitaxial layer to the total area is between 55 and 60 percent.
5. The led of claim 1, wherein the sum of the number of the first and second electrodes is no less than 5.
6. The led of claim 1, wherein the total number of the first and second electrodes is no less than 7.
7. The led of claim 1, wherein the total number of the first and second electrodes is no less than 9.
8. The led of claim 1, wherein the total number of the first and second electrodes is no less than 11.
9. The light-emitting diode according to claim 1, wherein a trench is provided on the second semiconductor layer and the active light-emitting layer, the trench dividing the second semiconductor layer and the active light-emitting layer into at least two mesa structures spaced apart from each other and exposing a portion of the first semiconductor layer, wherein the at least a portion of the light-emitting region includes at least one mesa structure, the first electrode is disposed in the trench and electrically connected to the first semiconductor layer, the second electrode is disposed on the second semiconductor layer and electrically connected to the second semiconductor layer, or the second electrode is disposed at least partially in the trench and electrically connected to the second semiconductor layer through a branch electrode or a current diffusion layer.
10. The led of claim 9, wherein the first and second electrodes are respectively stripe-shaped electrodes extending along a first direction and spaced apart from each other along a second direction perpendicular to the first direction.
11. The light-emitting diode according to claim 1, wherein an area ratio of a set of all of the at least part of the light-emitting areas on the light-emitting epitaxial layer to the entire light-emitting areas on the light-emitting epitaxial layer is not less than 50%.
12. The light-emitting diode according to claim 1, wherein an area ratio of a set of all of the at least part of the light-emitting areas on the light-emitting epitaxial layer to the entire light-emitting areas on the light-emitting epitaxial layer is not less than 70%.
13. The led of claim 1, wherein the area ratio of the set of all of said at least some light-emitting areas on said light-emitting epitaxial layer to the total light-emitting area on said light-emitting epitaxial layer is not less than 90%.
14. The led of claim 1, wherein the led has an average current density of not less than 0.5A/mm during operation 2 。
15. The led of claim 1, wherein the led has an average current density of not less than 1A/mm during operation 2 。
16. The led of claim 1, wherein the led has an average current density of not less than 2A/mm during operation 2 。
17. The led of claim 1, wherein the led has an average current density of not less than 10A/mm during operation 2 。
18. The led of claim 1, wherein the led has an average current density of not less than 20A/mm during operation 2 。
19. A light emitting diode, comprising:
a substrate;
the light-emitting epitaxial layer comprises a first semiconductor layer, an active light-emitting layer and a second semiconductor layer which are sequentially stacked on the substrate;
a first electrode electrically connected to one of the first semiconductor layer and the second semiconductor layer, and a plurality of second electrodes electrically connected to the other of the first semiconductor layer and the second semiconductor layer;
wherein the light emitting diode is a vertical light emitting diode or a flip light emitting diode; the first electrode is a face electrode, projections of the second electrodes on the substrate are arranged in the projections of the first electrodes on the substrate at intervals, the shortest distance between two adjacent second electrodes is not more than 80 micrometers, the ratio of the effective light-emitting area to the total area of the light-emitting epitaxial layer is not more than 65%, and the first semiconductor layer and the second semiconductor layer are both made of materials based on an aluminum gallium nitride system.
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