Epitaxial structure, LED chip and manufacturing method thereof

Abstract

The invention discloses an epitaxial structure, an LED chip and a manufacturing method thereof, the epitaxial structure comprises N stacked light-emitting units and tunnel junctions located between two adjacent light-emitting units, N is greater than or equal to 2, and N is a positive integer; the light-emitting unit comprises a first type waveguide layer, an active layer and a second type waveguide layer; the tunnel junction comprises a first type material layer and a second type material layer which are stacked; the forbidden bandwidths of the first type doping layer and the second type doping layer of the tunnel junction in the light emitting direction are not changed or are gradually increased; the array substrate further comprises a plurality of first-type reflecting layers; the first type reflection layer is laminated on the surface, facing the first type waveguide layer, of each tunnel junction; or the first type reflection layer is laminated on the surface, deviating from the active layer, of each first type waveguide layer. The epitaxial structure is combined with a plurality of light-emitting units through tunnel junctions to form a multi-junction structure, so that the working voltage is effectively improved. And moreover, the occupied area is small, and the epitaxial area loss is reduced. Through the arrangement of the forbidden band width of the tunnel junction, the top light absorption from the epitaxial structure along the light emitting direction is reduced, and the higher light emitting efficiency is ensured.

Description

Technical Field

[0001] This invention relates to the field of light-emitting diode technology, and more specifically, to an epitaxial structure, an LED chip, and a method for manufacturing the same. Background Technology

[0002] Light-emitting diodes (LEDs) are widely used in lighting, displays, communications, and other fields due to their low power consumption, small size, and high reliability. With the rapid development of industry, the demand for LED power is increasing while costs are decreasing, making the manufacture of high-power, low-cost LEDs a growing trend. One important technological branch of this is high-voltage LEDs.

[0003] High-voltage LEDs are a type of high-power LED. A common approach is for LED manufacturers to integrate high-power LED chips using a series connection of low-power LEDs. The traditional chip-connection technique involves using multiple LED chips connected horizontally in a wire-connected configuration. This connection links the P-electrode of one LED to the N-electrode of another LED, and so on, to form a high-voltage chip.

[0004] Using this traditional high-voltage chip structure has several drawbacks. First, the manufacturing process is prone to open circuits due to the step difference between the N and P electrodes, resulting in a high failure rate. Second, this horizontal connection technology requires a large number of LEDs, leading to a large area of ​​high-voltage LEDs. Third, the large number of LEDs necessitates more trenches for insulation and the connection of P and N electrodes between different light-emitting units requires significant loss of electrode area. Therefore, overall, the epitaxial area loss is substantial. Summary of the Invention

[0005] In view of this, the present invention provides an epitaxial structure, an LED chip and a method for manufacturing the same, to solve the problems of large LED chip area and large epitaxial area loss caused by traditional horizontal series structures.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An epitaxial structure includes: N light-emitting units stacked sequentially and a tunnel junction located between two adjacent light-emitting units, where N≥2 and N is a positive integer;

[0008] The light-emitting unit includes a first type waveguide layer, an active layer, and a second type waveguide layer stacked sequentially.

[0009] Each of the tunneling joints includes a first type of material layer and a second type of material layer stacked together;

[0010] The band gap of the first type doped layer of the tunnel junction remains unchanged or gradually increases along the light emission direction of the epitaxial structure;

[0011] The band gap of the second-type doped layer of the tunnel junction remains unchanged or gradually increases along the light-emitting direction of the epitaxial structure;

[0012] It also includes several first-type reflective layers; the first-type reflective layers are stacked on the surface of each of the tunnel junctions facing the first-type waveguide layer; or, the first-type reflective layers are stacked on the surface of each of the first-type waveguide layers away from the active layer.

[0013] Furthermore, the doping concentration of the first type doped layer of the tunnel junction remains unchanged or gradually decreases along the light-emitting direction of the epitaxial structure;

[0014] The doping concentration of the second-type doped layer of the tunnel junction remains constant or gradually decreases along the light-emitting direction of the epitaxial structure.

[0015] Furthermore, the first type of reflective layer is a DBR reflective layer;

[0016] Along the light emission direction of the epitaxial structure, the logarithm of the first type of reflective layer gradually decreases; the logarithm of the first type of reflective layer ranges from 2 to 60, including the endpoint values.

[0017] Furthermore, along the light emission direction of the epitaxial structure, the number of logarithms of the active layer gradually decreases;

[0018] The logarithm of the active layer ranges from 2 to 20, including endpoint values.

[0019] Furthermore, the growth temperature of the first type of reflective layer is higher than the growth temperature of the first type of waveguide layer, the active layer, and the second type of waveguide layer in the light-emitting unit; the growth temperature of the first type of waveguide layer, the active layer, and the second type of waveguide layer is higher than the growth temperature of the tunnel junction.

[0020] Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer of the j-th light-emitting unit is higher than that of the first type reflective layer of the (j+1)-th light-emitting unit.

[0021] Along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer of the j-th light-emitting unit is higher than that of the first type waveguide layer of the (j+1)-th light-emitting unit.

[0022] Along the growth direction of the epitaxial structure, the growth temperature of the active layer of the j-th light-emitting unit is higher than that of the active layer of the (j+1)-th light-emitting unit.

[0023] Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer of the j-th light-emitting unit is higher than that of the second type waveguide layer of the (j+1)-th light-emitting unit; where 2≤j≤N-1;

[0024] Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction is higher than that of the (i+1)-th tunnel junction, where 1≤i<N-1.

[0025] Furthermore, the growth temperature of the first type of reflective layer is 10°C to 150°C higher than the growth temperature of the first type of waveguide layer, active layer and second type of waveguide layer in the light-emitting unit that are in contact with it, including the endpoint values.

[0026] The growth temperature of the first type waveguide layer, the active layer, and the second type waveguide layer in the light-emitting unit is 40°C-150°C higher than the growth temperature of the tunnel junction located on the second type waveguide layer of the light-emitting unit, including the endpoint values.

[0027] Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer of the j-th light-emitting unit is 0-30℃ higher than that of the first type reflective layer of the (j+1)-th light-emitting unit, including the right endpoint value;

[0028] Along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer of the j-th light-emitting unit is 0-30℃ higher than that of the first type waveguide layer of the (j+1)-th light-emitting unit, including the right endpoint value.

[0029] Along the growth direction of the epitaxial structure, the growth temperature of the active layer of the j-th light-emitting unit is 0-30℃ higher than that of the active layer of the (j+1)-th light-emitting unit, including the right endpoint value.

[0030] Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer of the j-th light-emitting unit is 0-30℃ higher than that of the second type waveguide layer of the (j+1)-th light-emitting unit, including the right endpoint value; where 2≤j≤N-1;

[0031] Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction is 0-30℃ higher than that of the (i+1)-th tunnel junction, including the right endpoint value; where 1≤i<N-1.

[0032] The present invention also provides an LED chip, comprising: a substrate, at least two epitaxial structures, a transparent conductive layer, a first electrode, and a second electrode;

[0033] Each of the epitaxial structures is an epitaxial structure as described above, and the first type reflective layer of the epitaxial structure is stacked on the surface of each first type waveguide layer away from the active layer; the at least two epitaxial structures are sequentially stacked on one side surface of the substrate;

[0034] The transparent conductive layer is located between two adjacent epitaxial structures, and the two adjacent epitaxial structures are connected in series;

[0035] The first electrode is disposed on the side of the substrate away from the epitaxial stack and is electrically connected to the first type waveguide layer;

[0036] The second electrode is located on the side of the epitaxial structure furthest from the substrate, away from the substrate, and is electrically connected to the second type waveguide layer.

[0037] The present invention also provides an LED chip, characterized in that it includes a substrate, a first epitaxial structure, a second epitaxial structure, a bonding layer, a metal reflector, a first electrode, and a second electrode;

[0038] The first epitaxial structure is any one of the epitaxial structures described above, and the first type of reflective layer of the epitaxial structure is stacked on the surface of each first type of waveguide layer away from the active layer;

[0039] The second epitaxial structure is the epitaxial structure according to any one of claims 1-6, and the first type of reflective layer is stacked on the surface of each of the tunnel junctions facing the first type of waveguide layer;

[0040] The first epitaxial structure is located on one side surface of the substrate;

[0041] The second epitaxial structure is bonded to the side of the substrate opposite to the first epitaxial structure via a bonding layer, and is connected in series with the first epitaxial structure;

[0042] The metal mirror is located between the bonding layer and the second epitaxial structure;

[0043] The first electrode is disposed on the side of the second epitaxial structure opposite to the substrate and is electrically connected to the first type of waveguide layer;

[0044] The second electrode is disposed on the surface of the first epitaxial structure opposite to the substrate and is electrically connected to the second type waveguide layer.

[0045] This invention also provides a method for manufacturing an LED chip, comprising:

[0046] Provide substrate;

[0047] An epitaxial structure is grown on one side surface of the substrate to form an epitaxial wafer; the growth of the epitaxial structure includes growing N light-emitting units stacked sequentially along a direction away from the substrate and a tunnel junction located between two adjacent light-emitting units, where N≥2 and N is a positive integer;

[0048] The light-emitting unit includes a first type waveguide layer, an active layer, and a second type waveguide layer grown sequentially along a direction away from the substrate.

[0049] The tunneling junction includes a first type of material layer and a second type of material layer stacked together.

[0050] The band gap of the first type doped layer of the tunnel junction remains unchanged or gradually increases along the light emission direction of the epitaxial structure;

[0051] The band gap of the second-type doped layer of the tunnel junction remains unchanged or gradually increases along the light-emitting direction of the epitaxial structure;

[0052] It also includes growing several first-type reflective layers; firstly, the first-type reflective layers are grown before each first-type waveguide layer is grown, and then the first-type waveguide layers are grown on the first-type reflective layers;

[0053] The growth temperature of the first type of reflective layer is higher than that of the first type of waveguide layer, active layer and second type of waveguide layer in the light-emitting unit; the growth temperature of the first type of waveguide layer, active layer and second type of waveguide layer is higher than that of the tunnel junction.

[0054] Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer of the j-th light-emitting unit is higher than that of the first type reflective layer of the (j+1)-th light-emitting unit.

[0055] Along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer of the j-th light-emitting unit is higher than that of the first type waveguide layer of the (j+1)-th light-emitting unit.

[0056] Along the growth direction of the epitaxial structure, the growth temperature of the active layer of the j-th light-emitting unit is higher than that of the active layer of the (j+1)-th light-emitting unit.

[0057] Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer of the j-th light-emitting unit is higher than that of the second type waveguide layer of the (j+1)-th light-emitting unit; where 2≤j≤N-1;

[0058] Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction is higher than that of the (i+1)-th tunnel junction, where 1≤i<N-1;

[0059] A first transparent conductive bonding layer is grown on the side of an epitaxial wafer away from the substrate; the first transparent conductive bonding layer is electrically connected to the second type waveguide layer;

[0060] Another epitaxial wafer is bonded to a transfer substrate on the side opposite to the substrate. After removing the substrate, a second transparent conductive bonding layer is grown on the side of the epitaxial structure opposite to the transfer substrate. The second transparent conductive bonding layer is electrically connected to the first type waveguide layer.

[0061] The first transparent conductive bonding layer and the second transparent conductive bonding layer are bonded together, and the transfer substrate is removed;

[0062] A first electrode and a second electrode are fabricated on the bonded epitaxial wafer; the first electrode is disposed on the side of the substrate away from the epitaxial structure and electrically connected to a first type waveguide layer; the second electrode is disposed on the side of the epitaxial structure away from the substrate and electrically connected to a second type waveguide layer.

[0063] The present invention also provides a method for manufacturing an LED chip, comprising:

[0064] Provide substrate;

[0065] An epitaxial structure is grown on one side surface of the substrate to form an epitaxial wafer; the growth of the epitaxial structure includes growing N light-emitting units stacked sequentially along a direction away from the substrate and a tunnel junction located between two adjacent light-emitting units, where N≥2 and N is a positive integer;

[0066] The light-emitting unit includes a first type waveguide layer, an active layer, and a second type waveguide layer grown sequentially along a direction away from the substrate.

[0067] The tunneling junction includes a first type of material layer and a second type of material layer stacked together;

[0068] The band gap of the first type doped layer of the tunnel junction remains unchanged or gradually increases along the light emission direction of the epitaxial structure;

[0069] The band gap of the second-type doped layer of the tunnel junction remains unchanged or gradually increases along the light-emitting direction of the epitaxial structure;

[0070] It also includes growing a plurality of first-type reflective layers; growing the first-type reflective layer before growing each of the first-type waveguide layers, and then growing the first-type waveguide layer on the first-type reflective layer; or, growing the first-type reflective layer on each tunnel junction after each of the tunnel junctions has been grown; the first-type reflective layer is grown in the former manner to form a first epitaxial wafer, and the first-type reflective layer is grown in the latter manner to form a second epitaxial wafer;

[0071] A metal mirror is fabricated on the side of the second epitaxial wafer that is away from the substrate;

[0072] The metal mirror of the second epitaxial wafer is bonded to the side of the first epitaxial wafer substrate away from the epitaxial structure through a bonding layer, and the substrate of the second epitaxial wafer is removed.

[0073] A first electrode and a second electrode are fabricated on the first epitaxial wafer and the second epitaxial wafer after bonding. The first electrode is disposed on the side of the second epitaxial wafer opposite to the first epitaxial wafer and electrically connected to a first type waveguide layer. The second electrode is disposed on the side of the first epitaxial wafer opposite to the second epitaxial wafer and electrically connected to a second type waveguide layer.

[0074] Compared with existing technologies, the technical solution provided by this invention has at least the following advantages:

[0075] The epitaxial structure provided in this application includes: N light-emitting units stacked sequentially and a tunnel junction located between two adjacent light-emitting units, where N ≥ 2 and N is a positive integer; each light-emitting unit includes a first-type waveguide layer, an active layer, and a second-type waveguide layer stacked sequentially; each tunnel junction includes a first-type material layer and a second-type material layer stacked sequentially; the bandgap of the first-type doped layer of the tunnel junction remains constant or gradually increases along the light-emitting direction of the epitaxial structure; the bandgap of the second-type doped layer of the tunnel junction remains constant or gradually increases along the light-emitting direction of the epitaxial structure; it also includes several first-type reflective layers; the first-type reflective layers are stacked on the surface of each tunnel junction facing the first-type waveguide layer; or, the first-type reflective layers are stacked on the surface of each first-type waveguide layer away from the active layer. This epitaxial structure forms a multi-junction structure by combining multiple light-emitting units through tunnel junctions, effectively increasing the operating voltage of the epitaxial structure to increase the operating voltage of the LED chip, and also occupying a small area, reducing epitaxial area loss. Furthermore, by setting the bandgap of the first type doped layer of the tunnel junction along the light-emitting direction of the epitaxial structure to remain unchanged or gradually increase, and the bandgap of the second type doped layer of the tunnel junction along the light-emitting direction of the epitaxial structure to remain unchanged or gradually increase, the light absorption from the top of the epitaxial structure along the light-emitting direction is reduced, thus ensuring a high light extraction efficiency. Attached Figure Description

[0076] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0077] Figure 1 This is a schematic diagram of one embodiment of the extensional structure in this application;

[0078] Figure 2 This is a schematic diagram of another embodiment of the extensional structure in this application;

[0079] Figure 3 This is a schematic diagram of another embodiment of the extensional structure in this application;

[0080] Figure 4 This is a schematic diagram of the structure of one embodiment of the LED chip in this application;

[0081] Figure 5-8 for Figure 4 A structural diagram illustrating the LED chip manufacturing process;

[0082] Figure 9 A schematic diagram of another embodiment of the LED chip in this application;

[0083] Figure 10 for Figure 9 A schematic diagram of the LED chip manufacturing process.

[0084] Figure label:

[0085] Substrate 11; Transfer substrate 13; Type I waveguide layer 500; Type II waveguide layer 600; Active layer 4; Transparent conductive layer 5; First transparent conductive bonding layer 5a; Second transparent conductive bonding layer 5b; Type I reflective layer 81; Metal reflector 82; First electrode 91; Second electrode 92; Buffer layer 10; Type I current spreading layer 40; Second current spreading layer 50; Type I ohmic contact layer 60; Second ohmic contact layer 70; Bonding layer D;

[0086] Tunnel junction TJ; First tunnel junction TJ1; N-1th tunnel junction TJ(N-1); First light-emitting unit W1; Second light-emitting unit W2; Nth light-emitting unit Wn; Corrosion cutoff layer E; First light emission direction L1; Second light emission direction L2; Third light emission direction L3. Detailed Implementation

[0087] To make the content of this invention clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0088] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0089] Secondly, this application provides a detailed description in conjunction with schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included. In this application, unless specifically stated otherwise, all numerical ranges include endpoint values.

[0090] In view of the technical problems described in the background art, this application provides an epitaxial structure, an LED chip and a method for manufacturing the same, which can improve the operating voltage of the LED and occupy a small area, thereby reducing epitaxial area loss.

[0091] like Figure 1 As shown, the epitaxial structure includes N light-emitting units stacked sequentially and tunnel junctions TJ located between adjacent light-emitting units, where N ≥ 2 and N is a positive integer. Each light-emitting unit includes a first-type waveguide layer 500, an active layer 4, and a second-type waveguide layer 600 stacked sequentially. Each tunnel junction TJ includes a stacked first-type material layer and a second-type material layer; the bandgap of the first-type doped layer of the tunnel junction TJ remains constant or gradually increases along the light-emitting direction of the epitaxial structure; the bandgap of the second-type doped layer of the tunnel junction TJ remains constant or gradually increases along the light-emitting direction of the epitaxial structure. The epitaxial structure also includes several first-type reflective layers 81; the first-type reflective layers 81 are stacked on the surface of each tunnel junction TJ facing the first-type waveguide layer 500 (e.g., ...). Figure 3 (as shown); or, the first type of reflective layer 81 is stacked on the surface of each first type of waveguide layer away from the active layer (as shown). Figure 1 , 2 (As shown).

[0092] It should be understood that epitaxial structures are generally grown on one side of the substrate surface. Figure 1-3 The diagram exemplarily shows the first light-emitting unit W1, the second light-emitting unit W2, and the Nth light-emitting unit Wn along the growth direction of the epitaxial structure, as well as the first tunnel junction TJ1 and the (N-1)th tunnel junction TJ(N-1).

[0093] Preferably, the bandgap values ​​of the first-type doped layer and the second-type doped layer of the tunnel junction TJ range from 1.0 eV to 2.4 eV, including the endpoint values.

[0094] In this application, the first and second types of doping are opposite, being either N-type or P-type doping, respectively. That is, when the first type is N-type doped, the second type is P-type doped; and vice versa. This application uses an example where the first type is N-type doped and the second type is P-type doped.

[0095] Optionally, the materials of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 can be one or more of GaAs, AlGaAs, AlAs, GaInAs, AlGaInAs, AlGaAsP, AlInP, AlGaInP, and GaInP.

[0096] This epitaxial structure forms a multi-junction structure by combining multiple light-emitting units through a tunnel junction, effectively increasing the operating voltage of the epitaxial structure and thus the operating voltage of the LED chip. Furthermore, it occupies a small area, reducing epitaxial area loss. Moreover, by setting the bandgap of the first-type doped layer of the tunnel junction TJ along the light-emitting direction of the epitaxial structure to remain constant or gradually increase, and the bandgap of the second-type doped layer of the tunnel junction TJ along the light-emitting direction of the epitaxial structure to remain constant or gradually increase, light absorption from the top of the epitaxial structure along the light-emitting direction is reduced, ensuring high light extraction efficiency.

[0097] Optionally, in one embodiment of the epitaxial structure, such as Figure 1 As shown, Figure 1 As shown, the epitaxial structure also includes a second-type current spreading layer 50 and a second-type ohmic contact layer 70 located on the second-type waveguide layer 600 of the Nth light-emitting unit; the second-type ohmic contact layer 70 is stacked on the surface of the second-type current spreading layer 50 away from the light-emitting unit and exposes a portion of the second-type current spreading layer 50. Specifically, the second-type ohmic contact layer 70 can be configured in a mesh shape to expose a portion of the second-type current spreading layer 50.

[0098] Further optional, such as Figure 1 As shown, the epitaxial structure also includes an etch stop layer E and a buffer layer 10 on the side of the first type waveguide layer 500 of the first light-emitting unit W1 away from the active layer 4; the etch stop layer E is located between the buffer layer 10 and the first light-emitting unit W1.

[0099] Optionally, in one embodiment of the epitaxial structure, such as Figure 2 As shown, it also includes a buffer layer 10 located on the side of the first type waveguide layer 500 opposite to the active layer of the first light-emitting unit W1. That is, the etch stop layer E may not be included, and the remaining structure is the same as... Figure 1 They have the same extensional structure.

[0100] Optionally, in one embodiment of the epitaxial structure, such as Figure 3 As shown, the epitaxial structure may include a second type current spreading layer 50 located on the second type waveguide layer 600 of the Nth light-emitting unit Wn.

[0101] Further optional, such as Figure 3 As shown, the epitaxial structure also includes a first-type current spreading layer 40, a first-type ohmic contact layer 60, an etching stop layer E, and a buffer layer 10 located on the side of the first light-emitting unit W1 facing the substrate 11. The first-type current spreading layer 40, the first-type ohmic contact layer 60, the etching stop layer E, and the buffer layer 10 are arranged sequentially in a direction away from the light-emitting unit.

[0102] Optionally, the materials of the current spreading layer and the ohmic contact layer can be one or more of GaAs, AlGaAs, GaInAs, AlGaInAs, AlGaAsP, AlGaInP, and GaInP.

[0103] Optionally, the material of the corrosion stop layer E can be one or more of GaAs, AlGaAs, AlAs, AlInP, AlGaInP, and GaInP.

[0104] The material of the buffer layer 10 can be one or more of GaAs, AlGaAs, AlGaInP, and GaInP.

[0105] In a preferred embodiment based on the above embodiments, the doping concentration of the first type doped layer of the tunnel junction TJ along the light-emitting direction of the epitaxial structure remains unchanged or gradually decreases; the doping concentration of the second type doped layer of the tunnel junction TJ along the light-emitting direction of the epitaxial structure remains unchanged or gradually decreases. This configuration reduces light absorption from the top of the epitaxial structure along the light-emitting direction, ensuring high light extraction efficiency.

[0106] Preferably, the doping concentration of the first-type doped layer and the second-type doped layer is greater than 1E19 / cm². 3 .

[0107] Along the light-emitting direction of the epitaxial structure, the doping concentration of the first type doped layer of the tunnel junction TJ gradually decreases. Taking three tunnel junction TJs as an example, that is, along the light-emitting direction of the epitaxial structure, the doping concentration of the first type doped layer of the first tunnel junction is greater than that of the second tunnel junction, the doping concentration of the first type doped layer of the second tunnel junction is greater than that of the third tunnel junction, and so on.

[0108] Along the light-emitting direction of the epitaxial structure, the doping concentration of the type II doped layer of the tunnel junction TJ gradually decreases. Taking three tunnel junction TJs as an example, that is, along the light-emitting direction of the epitaxial structure, the doping concentration of the type II doped layer of the first tunnel junction is greater than that of the second tunnel junction, the doping concentration of the type II doped layer of the second tunnel junction is greater than that of the third tunnel junction, and so on.

[0109] In a preferred embodiment based on any of the above embodiments, the first type of reflective layer 81 is a DBR reflective layer. The number of logarithms of the first type of reflective layer 81 gradually decreases along the light emission direction of the epitaxial structure.

[0110] Taking a case with 4 light-emitting units as an example, along the light-emitting direction of the epitaxial structure, the number of pairs of the first type-1 reflective layer 81 is greater than the number of pairs of the second type-1 reflective layer 81; the number of pairs of the second type-1 reflective layer 81 is greater than the number of pairs of the third type-1 reflective layer 81; and the number of pairs of the third type-1 reflective layer 81 is greater than the number of pairs of the fourth type-1 reflective layer 81.

[0111] Preferably, the logarithm of the first type of reflective layer 81 ranges from 2 to 60, including the endpoint values.

[0112] Along the light emission direction of the epitaxial structure, the logarithm of each type 81 first-type reflective layer gradually decreases, enabling each light-emitting unit to resonate and emit light, and reducing the light absorption of the active region beneath each light-emitting unit, effectively improving light emission efficiency and reducing the light emission angle. Since too many logarithms in the DBR will cause increased stress, setting the logarithm of the DBR in the range of 2-60 is more effective.

[0113] In a preferred embodiment based on any of the above embodiments, the number of active layers gradually decreases along the light emission direction of the epitaxial structure.

[0114] Taking a case with 4 light-emitting units as an example, along the light-emitting direction of the epitaxial structure, the number of logarithms of the first active layer 4 is greater than that of the second active layer 4; the number of logarithms of the second active layer 4 is greater than that of the third active layer 4; and the number of logarithms of the third active layer 4 is greater than that of the fourth active layer 4.

[0115] Preferably, the logarithm of the active layer 4 ranges from 2 to 20, including endpoint values.

[0116] The number of logarithms in each active layer 4 gradually decreases along the light-emitting direction of the epitaxial structure, reducing light absorption from the top of the epitaxial structure along the light-emitting direction and ensuring high light-emitting efficiency. As the number of logarithms in the active layer 4 increases, the internal quantum efficiency also increases. However, when the number of logarithms in the active layer 4 increases to a certain value, since the carrier lifetime is constant, those regions of the active layer 4 where there are too many holes and electrons to recombine or where the recombination number is small become more light-absorbing than recombination-emitting, which leads to a decrease in internal quantum efficiency. Therefore, the optimal effect is achieved when the number of logarithms in the active layer 4 is in the range of 2-20.

[0117] In a preferred embodiment based on any of the above embodiments, the growth temperature of the first type reflective layer 81 is higher than the growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 in the light-emitting unit; the growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 is higher than the growth temperature of the tunnel junction TJ.

[0118] Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer 81 of the j-th light-emitting unit is higher than that of the first type reflective layer 81 of the (j+1)-th light-emitting unit.

[0119] Along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer 500 of the j-th light-emitting unit is higher than that of the first type waveguide layer 500 of the (j+1)-th light-emitting unit.

[0120] Along the growth direction of the epitaxial structure, the growth temperature of the active layer 4 of the j-th light-emitting unit is higher than that of the active layer 4 of the (j+1)-th light-emitting unit.

[0121] Along the growth direction of the epitaxial structure, the growth temperature of the second-type waveguide layer 600 of the j-th light-emitting unit is higher than that of the second-type waveguide layer 600 of the (j+1)-th light-emitting unit. Wherein, 2≤j≤N-1.

[0122] Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction TJ is higher than that of the (i+1)-th tunnel junction TJ, where 1≤i<N-1.

[0123] During epitaxial growth, a stepped cyclic cooling method was used to ensure the quality of polycrystalline structures and subsequent doping efficiency, and to improve the impact of doping sources on subsequent multijunctions.

[0124] Figure 1 , 2 The epitaxial structure shown, taking an example with four light-emitting units and three tunnel junctions (TJs), illustrates the growth temperature. Along the growth direction of the epitaxial structure, the growth temperature of the first type-1 reflective layer 81 is higher than that of the first type-1 waveguide layer 500, active layer 4, and second type-1 waveguide layer 600 of the first light-emitting unit. The growth temperature of the first type-1 waveguide layer 500, active layer 4, and second type-1 waveguide layer 600 of the first light-emitting unit is higher than that of the first tunnel junction. The growth temperature of the second type-1 reflective layer 81 is higher than that of the first type-1 waveguide layer 500, active layer 4, and second type-1 waveguide layer 600 of the second light-emitting unit. The growth temperature of the first type-1 waveguide layer 500, active layer 4, and second type-1 waveguide layer 600 of the second light-emitting unit is higher than that of the second tunnel junction. The growth temperature of the third type-1 reflective layer 81 is higher than that of the first type-1 waveguide layer 500, active layer 4, and second type-1 waveguide layer 600 of the third light-emitting unit. The growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 of the third light-emitting unit is higher than the temperature of the third tunnel junction. The growth temperature of the fourth first type reflective layer 81 is higher than the growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 of the fourth light-emitting unit.

[0125] Figure 3The epitaxial structure shown, taking an example with four light-emitting units and three tunnel junctions (TJs), illustrates the growth temperature. Along the growth direction of the epitaxial structure, the growth temperatures of the first type waveguide layer 500, active layer 4, and second type waveguide layer 600 in the first light-emitting unit are higher than the growth temperature of the first tunnel junction. The growth temperature of the first type I reflective layer 81 is higher than that of the first type waveguide layer 500, active layer 4, and second type waveguide layer 600 in the second light-emitting unit. The growth temperatures of the first type waveguide layer 500, active layer 4, and second type waveguide layer 600 in the second light-emitting unit are higher than the growth temperature of the second tunnel junction. The growth temperature of the second type I reflective layer 81 is higher than that of the first type waveguide layer 500, active layer 4, and second type waveguide layer 600 in the third light-emitting unit. The growth temperatures of the first type waveguide layer 500, active layer 4, and second type waveguide layer 600 in the third light-emitting unit are higher than the temperature of the third tunnel junction. The growth temperature of the third type I reflective layer 81 is higher than that of the growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 in the fourth light-emitting unit.

[0126] Along the growth direction of the epitaxial structure, the growth temperature of the first type I reflective layer 81 is higher than that of the second type I reflective layer 81, the growth temperature of the second type I reflective layer 81 is higher than that of the third type I reflective layer 81, and so on.

[0127] Along the growth direction of the epitaxial structure, the growth temperature of the first type I waveguide layer 500 is higher than that of the second type I waveguide layer 500, the growth temperature of the second type I waveguide layer 500 is higher than that of the third type I waveguide layer 500, and the growth temperature of the third type I waveguide layer 500 is higher than that of the fourth type I waveguide layer 500.

[0128] Along the growth direction of the epitaxial structure, the growth temperature of the first active layer 4 is higher than that of the second active layer 4, the growth temperature of the second active layer 4 is higher than that of the third active layer 4, and the growth temperature of the third active layer 4 is higher than that of the fourth active layer 4.

[0129] Along the growth direction of the epitaxial structure, the growth temperature of the first type II waveguide layer 600 is higher than that of the second type II waveguide layer 600, the growth temperature of the second type II waveguide layer 600 is higher than that of the third type II waveguide layer 600, and the growth temperature of the third type II waveguide layer 600 is higher than that of the fourth type II waveguide layer 600.

[0130] Along the growth direction of the epitaxial structure, the growth temperature of the first tunnel junction is higher than that of the second tunnel junction, and the growth temperature of the second tunnel junction is higher than that of the third tunnel junction.

[0131] Optionally, the first type of reflective layer 81 is a high-Al composition AlGaAs material, which has a higher growth temperature, thus helping to obtain AlGaAs material with high crystal quality. The doping concentration of the tunnel junction TJ needs to reach a high level, therefore the tunnel junction TJ temperature is relatively low, which can effectively increase the doping concentration of the tunnel junction TJ doped with impurities.

[0132] Alternatively, the temperature range of the first type of reflective layer 81 is 750°C-660°C.

[0133] The growth temperature of the first-type reflective layer 81 is 10°C-150°C higher than the growth temperatures of the first-type waveguide layer 500, the active layer 4, and the second-type waveguide layer 600 in the light-emitting unit it contacts, including the endpoint values. For example, as Figure 1 , 2 As shown, the growth temperature of the first type-1 reflective layer 81 is 10℃-150℃ higher than the growth temperatures of the first type-1 waveguide layer 500, active layer 4, and second type-1 waveguide layer 600 of the first light-emitting unit, including the endpoint values; the growth temperature of the second type-1 reflective layer 81 is 10℃-150℃ higher than the growth temperatures of the first type-1 waveguide layer 500, active layer 4, and second type-1 waveguide layer 600 of the second light-emitting unit, including the endpoint values; and so on. Figure 3 As shown, the growth temperature of the first type-1 reflective layer 81 is 10℃-150℃ higher than the growth temperature of the first type-1 waveguide layer 500, the active layer 4, and the second type-1 waveguide layer 600 of the second light-emitting unit, including the endpoint values; the growth temperature of the second type-1 reflective layer 81 is 10℃-150℃ higher than the growth temperature of the first type-1 waveguide layer 500, the active layer 4, and the second type-1 waveguide layer 600 of the third light-emitting unit, including the endpoint values; and so on.

[0134] The growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 in the light-emitting unit is 40℃-150℃ higher than the growth temperature of the tunnel junction TJ located on the second type waveguide layer 600 of the light-emitting unit, including the endpoint values. For example, the growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 in the first light-emitting unit is 40℃-150℃ higher than the growth temperature of the first tunnel junction, including the endpoint values; the growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 in the second light-emitting unit is 40℃-150℃ higher than the growth temperature of the second tunnel junction; and so on.

[0135] Along the growth direction of the epitaxial structure, the growth temperature of the j-th type I reflective layer 81 is 0-30℃ higher than the growth temperature of the (j+1)-th type I reflective layer 81, including the right endpoint. Where 2≤j≤N-1. For example, the growth temperature of the first type I reflective layer 81 is 0-30℃ higher than the growth temperature of the second type I reflective layer 81, including the right endpoint; the growth temperature of the second type I reflective layer 81 is 0-30℃ higher than the growth temperature of the third type I reflective layer 81, including the right endpoint; and so on.

[0136] Along the growth direction of the epitaxial structure, the growth temperature of the first-type waveguide layer 500 of the j-th light-emitting unit is 0-30℃ higher than that of the first-type waveguide layer 500 of the (j+1)-th light-emitting unit, including the right endpoint. Where 2≤j≤N-1. For example, the growth temperature of the first-type waveguide layer 500 of the 1st light-emitting unit is 0-30℃ higher than that of the 2nd light-emitting unit, including the right endpoint; the growth temperature of the first-type waveguide layer 500 of the 2nd light-emitting unit is 0-30℃ higher than that of the 3rd light-emitting unit, including the right endpoint; and so on.

[0137] Along the growth direction of the epitaxial structure, the growth temperature of the active layer 4 of the j-th light-emitting unit is 0-30℃ higher than that of the active layer 4 of the (j+1)-th light-emitting unit, including the right endpoint. Where 2≤j≤N-1. For example, the growth temperature of the active layer 4 of the 1st light-emitting unit is 0-30℃ higher than that of the 2nd light-emitting unit, including the right endpoint; the growth temperature of the active layer 4 of the 2nd light-emitting unit is 0-30℃ higher than that of the 3rd light-emitting unit, including the right endpoint; and so on.

[0138] Along the growth direction of the epitaxial structure, the growth temperature of the second-type waveguide layer 600 of the j-th light-emitting unit is 0-30℃ higher than that of the second-type waveguide layer 600 of the (j+1)-th light-emitting unit, including the right endpoint. Where 2≤j≤N-1. For example, the growth temperature of the second-type waveguide layer 600 of the 1st light-emitting unit is 0-30℃ higher than that of the 2nd light-emitting unit, including the right endpoint; the growth temperature of the second-type waveguide layer 600 of the 2nd light-emitting unit is 0-30℃ higher than that of the 3rd light-emitting unit, including the right endpoint; and so on.

[0139] Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction is 0-30℃ higher than that of the (i+1)-th tunnel junction, including the right endpoint; where 1≤i<N-1. For example, the growth temperature of the 1st tunnel junction is 0-30℃ higher than that of the 2nd tunnel junction, including the right endpoint; the growth temperature of the 2nd tunnel junction is 0-30℃ higher than that of the 3rd tunnel junction, including the right endpoint; and so on.

[0140] like Figure 4 As shown, this application also provides an LED chip, which includes a substrate 11, at least two epitaxial structures, a transparent conductive layer 5, a first electrode 91, and a second electrode 92.

[0141] Each epitaxial structure is the epitaxial structure described in any of the above embodiments, and the first type reflective layer 81 of the epitaxial structure is stacked on the surface of each first type waveguide layer 500 away from the active layer 4; the at least two epitaxial structures are sequentially stacked on one side surface of the substrate 11. The transparent conductive layer 5 is located between two adjacent epitaxial structures and connects the two adjacent epitaxial structures in series. The first electrode 91 is disposed on the side of the substrate 11 away from the epitaxial stack and is electrically connected to the first type waveguide layer 500. The second electrode 92 is disposed on the side of the epitaxial structure furthest from the substrate 11 away from the substrate 11 and is electrically connected to the second type waveguide layer 600.

[0142] In actual fabrication, multiple epitaxial structures grown on a substrate are bonded together by flipping them using a transfer substrate 13. When the epitaxial structure includes a buffer layer 10 and / or an etch stop layer E, the buffer layer 10 and / or the etch stop layer E are generally removed together after the substrate 11 is removed. (Appendix to this application) Figure 4 With Figure 1 Taking the bonding of two epitaxial structures as an example, one epitaxial structure grown on substrate 11 is flipped onto transfer substrate 13, and then substrate 11, buffer layer 10, and etching stop layer E are removed. Then, it is bonded to another epitaxial structure grown on substrate 11 via transparent conductive layer 5. After removing transfer substrate 13, the electrode is fabricated. Figure 4 The LED chip shown. Figure 4 The light emission directions of the two epitaxial structures are as follows: Figure 8 The first light emission direction L1 shown is the light emission direction from the substrate 11 to the epitaxial structure.

[0143] LED chips utilize any of the aforementioned epitaxial structures to increase operating voltage, and further increase operating voltage by connecting multiple epitaxial structures in series. Furthermore, bonding multi-junction epitaxial structures into a vertical structure instead of the traditional horizontal series structure avoids the open-circuit problem that easily occurs in series leads, simplifies chip manufacturing processes, and enables simpler and more reliable implementation of high-voltage structures. Additionally, it occupies a smaller area, reducing epitaxial area loss.

[0144] This application also provides a method for manufacturing an LED chip, used to manufacture the LED chip of the previous embodiment. Specifically, it includes:

[0145] S1: Provide substrate 11.

[0146] S2: As Figure 1 As shown, an epitaxial structure is grown on one side surface of the substrate 11 to form an epitaxial wafer. The grown epitaxial structure includes N light-emitting units stacked sequentially along a direction away from the substrate 11 and a tunnel junction TJ located between two adjacent light-emitting units, where N ≥ 2 and N is a positive integer.

[0147] The light-emitting unit includes a first-type waveguide layer 500, an active layer 4, and a second-type waveguide layer 600, grown sequentially along a direction away from the substrate. The tunnel junction TJ includes a first-type material layer and a second-type material layer stacked together. The bandgap of the first-type doped layer of the tunnel junction TJ remains constant or gradually increases along the light-emitting direction of the epitaxial structure; the bandgap of the second-type doped layer of the tunnel junction TJ remains constant or gradually increases along the light-emitting direction of the epitaxial structure.

[0148] It also includes growing a plurality of first-type reflective layers 81; the first-type reflective layers 81 are grown first before each first-type waveguide layer 500 is grown, and then the first-type waveguide layer 500 is grown on the first-type reflective layers 81.

[0149] Among them, the growth temperature of the first type reflective layer 81 is higher than that of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600; the growth temperatures of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 are higher than that of the tunnel junction TJ.

[0150] Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer 81 of the j-th light-emitting unit is higher than that of the first type reflective layer 81 of the (j+1)-th light-emitting unit.

[0151] Along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer 500 of the j-th light-emitting unit is higher than that of the first type waveguide layer 500 of the (j+1)-th light-emitting unit.

[0152] Along the growth direction of the epitaxial structure, the growth temperature of the active layer 4 of the j-th light-emitting unit is higher than that of the active layer 4 of the (j+1)-th light-emitting unit.

[0153] Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer 600 of the j-th light-emitting unit is higher than that of the second type waveguide layer 600 of the (j+1)-th light-emitting unit; where 2≤j≤N-1.

[0154] Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction is higher than that of the (i+1)-th tunnel junction, where 1≤i<N-1.

[0155] Optionally, the epitaxial structure further includes a second type current spreading layer 50 and a second type ohmic contact layer 70 located on the side of the Nth light-emitting unit Wn facing away from the substrate 11; the second type ohmic contact layer 70 is stacked on the surface of the second type current spreading layer 50 facing away from the light-emitting unit, and exposes a portion of the second type current spreading layer 50. Specifically, the second type ohmic contact layer 70 is configured in a mesh shape to expose a portion of the second type current spreading layer 50.

[0156] Optionally, the epitaxial LED chip further includes a buffer layer 10 located on the side of the first light-emitting unit facing the substrate 11. Optionally, the epitaxial LED chip further includes an etching stop layer E, which is located between the buffer layer 10 and the first light-emitting unit W1.

[0157] S3: As Figure 5 As shown, a first transparent conductive bonding layer 5a is grown on the side of an epitaxial wafer away from the substrate 11; the first transparent conductive bonding layer 5a is electrically connected to the second type waveguide layer 600.

[0158] S4: As Figure 6 , 7 As shown, another epitaxial wafer is bonded to the transfer substrate 13 on the side away from the substrate 11. After removing the substrate 11, a second transparent conductive bonding layer 5b is grown on the side of the epitaxial structure away from the transfer substrate. The second transparent conductive bonding layer 5b is electrically connected to the first type waveguide layer 500.

[0159] When the epitaxial structure includes an etching stop layer E and a buffer layer 10, the buffer layer 10 and the etching stop layer E are removed together after the substrate 11 is removed.

[0160] S5: As Figure 8 As shown, the first transparent conductive bonding layer 5a and the second transparent conductive bonding layer 5b are bonded together, and the transfer substrate 13 is removed. The first transparent conductive bonding layer 5a and the second transparent conductive bonding layer 5b, after being bonded together, together form the transparent conductive layer 5.

[0161] S6: Fabricate the first electrode 91 and the second electrode 92 on the bonded epitaxial wafer to obtain... Figure 4The LED chip shown has a first electrode 91 located on the side of the substrate 11 away from the epitaxial structure and electrically connected to the first type waveguide layer 500; and a second electrode 92 located on the side of the epitaxial structure away from the substrate 11 and electrically connected to the second type waveguide layer 600, which is located above the second type ohmic contact layer 70.

[0162] In a preferred embodiment, in step S2, the temperature range of the first type of reflective layer 81 is preferably 750°C-660°C.

[0163] The growth temperature of the first type reflective layer 81 in the light-emitting unit is 10℃-150℃ higher than the growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600, including the endpoint values, where 2≤j≤N-1.

[0164] The growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 in the light-emitting unit is 40℃-150℃ higher than the growth temperature of the tunnel junction TJ located on the second type waveguide layer 600 of the light-emitting unit, including the endpoint values, where 2≤j≤N-1.

[0165] Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer 81 of the j-th light-emitting unit is 0-30℃ higher than that of the first type reflective layer 81 of the (j+1)-th light-emitting unit, including the right endpoint value, where 2≤j≤N-1.

[0166] The growth temperature of the first type waveguide layer 500 of the j-th light-emitting unit along the growth direction of the epitaxial structure is 0-30℃ higher than that of the first type waveguide layer 500 of the (j+1)-th light-emitting unit, including the right endpoint value, where 2≤j≤N-1.

[0167] The growth temperature of the active layer 4 of the j-th light-emitting unit along the growth direction of the epitaxial structure is 0-30℃ higher than the growth temperature of the active layer 4 of the (j+1)-th light-emitting unit, including the right endpoint value, where 2≤j≤N-1.

[0168] The growth temperature of the second type waveguide layer 600 of the j-th light-emitting unit along the growth direction of the epitaxial structure is 0-30℃ higher than that of the second type waveguide layer 600 of the (j+1)-th light-emitting unit, including the right endpoint value; where 2≤j≤N-1.

[0169] The growth temperature of the i-th tunnel junction along the growth direction of the epitaxial structure is 0-30℃ higher than that of the (i+1)-th tunnel junction, including the right endpoint value; where 1≤i<N-1.

[0170] The method for manufacturing this LED chip is used to manufacture the LED chip of the previous embodiment. The remaining settings of the LED chip epitaxial structure have been described in detail in the various embodiments of the epitaxial structure described above, and will not be repeated here.

[0171] like Figure 9 As shown, this application also provides another LED chip, including a substrate 11, a first epitaxial structure, a second epitaxial structure, a bonding layer D, a metal reflector 82, a first electrode 91, and a second electrode 92.

[0172] The first epitaxial structure is the epitaxial structure described in any of the above embodiments, and the first type reflective layer 81 of the epitaxial structure is stacked on the surface of each first type waveguide layer 500 facing away from the active layer 4. The second epitaxial structure is the epitaxial structure described in any of the above embodiments, and the first type reflective layer 81 is stacked on the surface of the tunnel junction TJ facing the first type waveguide layer 500.

[0173] The first epitaxial structure is located on one side surface of the substrate. The second epitaxial structure is bonded to the side of the substrate opposite to the first epitaxial structure via a bonding layer D, and is connected in series with the first epitaxial structure. A metal mirror 82 is located between the bonding layer D and the second epitaxial structure. A first electrode 91 is disposed on the side of the second epitaxial structure opposite to the substrate and is electrically connected to the first type waveguide layer 500. A second electrode 92 is disposed on the surface of the first epitaxial structure opposite to the substrate and is electrically connected to the second type waveguide layer 600.

[0174] In the actual fabrication process, each epitaxial structure is grown on a substrate. Similar to the previous LED chip embodiment, the two epitaxial structures are integrated together by means of substrate flipping and bonding, which will not be described in detail here. Appendix to this application Figure 9 With Figure 2 , 3 The bonding of the two epitaxial structures shown is illustrated as an example. Figure 9 In the LED chip shown, the light emission direction of the epitaxial structure above the substrate is the second light emission direction L2 shown in the figure (i.e., the direction from the substrate to the first epitaxial structure), and the light emission direction of the epitaxial structure below the substrate is the third light emission direction L3 shown in the figure (i.e., the direction from the substrate to the second epitaxial structure). In this way, the light from the epitaxial structure below the substrate can be reflected by the bottom condenser cup, which is suitable for traditional LED products packaged in condenser cups.

[0175] This application also provides a method for manufacturing an LED chip, used to manufacture the LED chip of the previous embodiment. Specifically, it includes:

[0176] R1: Provides substrate 11.

[0177] R2: An epitaxial structure is grown on one side surface of the substrate to form an epitaxial wafer; the grown epitaxial structure includes N light-emitting units stacked sequentially along the direction away from the substrate and a tunnel junction located between two adjacent light-emitting units, where N≥2 and N is a positive integer.

[0178] The light-emitting unit includes a first type waveguide layer 500, an active layer 4, and a second type waveguide layer 600, which are grown sequentially in a direction away from the substrate.

[0179] The tunnel junction (TJ) includes a first type material layer and a second type material layer stacked together. The band gap of the first type doped layer of the tunnel junction TJ remains unchanged or gradually increases along the light emission direction of the epitaxial structure. The band gap of the second type doped layer of the tunnel junction TJ remains unchanged or gradually increases along the light emission direction of the epitaxial structure.

[0180] It also includes growing a number of first-type reflective layers 81; growing a first-type reflective layer 80 before growing each first-type waveguide layer 500, and then growing the first-type waveguide layer 500 on the first-type reflective layer 81; or, growing a first-type reflective layer 81 on each tunnel junction TJ after each tunnel junction TJ is grown; the first-type reflective layer 81 is grown in the former manner to form a first epitaxial wafer, and the first-type reflective layer 81 is grown in the latter manner to form a second epitaxial wafer.

[0181] Among them, the growth temperature of the first type reflective layer 81 is higher than that of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600; the growth temperatures of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 are higher than that of the tunnel junction TJ.

[0182] Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer 81 of the j-th light-emitting unit is higher than that of the first type reflective layer 81 of the (j+1)-th light-emitting unit.

[0183] Along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer 500 of the j-th light-emitting unit is higher than that of the first type waveguide layer 500 of the (j+1)-th light-emitting unit.

[0184] Along the growth direction of the epitaxial structure, the growth temperature of the active layer 4 of the j-th light-emitting unit is higher than that of the active layer 4 of the (j+1)-th light-emitting unit.

[0185] Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer 600 of the j-th light-emitting unit is higher than that of the second type waveguide layer 600 of the (j+1)-th light-emitting unit; where 2≤j≤N-1.

[0186] Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction is higher than that of the (i+1)-th tunnel junction, where 1≤i<N-1.

[0187] R3: such as Figure 10 As shown, a metal reflector 82 is fabricated on the side of the second epitaxial wafer away from the substrate.

[0188] R4: The metal reflector 82 of the second epitaxial wafer is bonded to the side of the first epitaxial wafer substrate opposite to the epitaxial structure via bonding layer D, and the substrate of the second epitaxial wafer is removed. Optionally, a first bonding sublayer can be fabricated on the metal reflector 82, and a second bonding sublayer can be fabricated on the substrate of the first epitaxial structure. The first bonding sublayer and the second bonding sublayer are bonded together to form bonding layer D and connect the two epitaxial wafers.

[0189] R5: A first electrode 91 and a second electrode 92 are fabricated on the first and second epitaxial wafers after bonding. The first electrode 91 is disposed on the side of the second epitaxial wafer away from the first epitaxial wafer and electrically connected to the first type waveguide layer 500. The second electrode 92 is disposed on the side of the first epitaxial wafer away from the second epitaxial wafer and electrically connected to the second type waveguide layer 600.

[0190] In a preferred embodiment, in step R2, the temperature range of the first type of reflective layer 81 is preferably 750°C-660°C.

[0191] The growth temperature of the first type reflective layer 81 in the light-emitting unit is 10℃-150℃ higher than the growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600, including the endpoint values, where 2≤j≤N-1.

[0192] The growth temperature of the first type waveguide layer 500, the active layer 4, and the second type waveguide layer 600 in the light-emitting unit is 40℃-150℃ higher than the growth temperature of the tunnel junction TJ located on the second type waveguide layer 600 of the light-emitting unit, including the endpoint values, where 2≤j≤N-1.

[0193] Along the growth direction of the epitaxial structure, in the direction away from the substrate 11, the growth temperature of the first type reflective layer 81 of the j-th light-emitting unit is 0-30℃ higher than the growth temperature of the first type reflective layer 81 of the (j+1)-th light-emitting unit, including the right endpoint value, where 2≤j≤N-1.

[0194] The growth temperature of the first type waveguide layer 500 of the j-th light-emitting unit along the growth direction of the epitaxial structure is 0-30℃ higher than that of the first type waveguide layer 500 of the (j+1)-th light-emitting unit, including the right endpoint value, where 2≤j≤N-1.

[0195] The growth temperature of the active layer 4 of the j-th light-emitting unit along the growth direction of the epitaxial structure is 0-30℃ higher than the growth temperature of the active layer 4 of the (j+1)-th light-emitting unit, including the right endpoint value, where 2≤j≤N-1.

[0196] The growth temperature of the second type waveguide layer 600 of the j-th light-emitting unit along the growth direction of the epitaxial structure is 0-30℃ higher than that of the second type waveguide layer 600 of the (j+1)-th light-emitting unit, including the right endpoint value; where 2≤j≤N-1.

[0197] The growth temperature of the i-th tunnel junction along the growth direction of the epitaxial structure is 0-30℃ higher than that of the (i+1)-th tunnel junction, including the right endpoint value; where 1≤i<N-1.

[0198] The method for manufacturing this LED chip is used to manufacture the LED chip of the previous embodiment. The remaining settings of the LED chip epitaxial structure have been described in detail in the various embodiments of the epitaxial structure described above, and will not be repeated here.

[0199] This application provides an LED chip and a method for manufacturing the LED chip, which employs the aforementioned epitaxial structure and therefore possesses all the beneficial effects of the aforementioned epitaxial structure, which will not be elaborated further here. For any aspects of the LED chip and the method for manufacturing the LED chip not mentioned herein, please refer to the description of the epitaxial structure.

[0200] Those skilled in the art should understand that, in the disclosure of this invention, the terms "lateral", "longitudinal", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0201] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0202] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An epitaxial structure, characterized in that, include: N light-emitting units are stacked sequentially and a tunnel junction is located between two adjacent light-emitting units, where N≥2 and N is a positive integer; The light-emitting unit includes a first type waveguide layer, an active layer, and a second type waveguide layer stacked sequentially. Each of the tunneling joints includes a first type of material layer and a second type of material layer stacked together; The band gap of the first type doped layer of the tunnel junction remains unchanged or gradually increases along the light emission direction of the epitaxial structure; The band gap of the second-type doped layer of the tunnel junction remains unchanged or gradually increases along the light-emitting direction of the epitaxial structure; It also includes several first-type reflective layers; the first-type reflective layers are stacked on the surface of each of the tunnel junctions facing the first-type waveguide layer; or, the first-type reflective layers are stacked on the surface of each of the first-type waveguide layers away from the active layer.

2. The epitaxial structure as described in claim 1, characterized in that, The doping concentration of the first type doped layer of the tunnel junction remains constant or gradually decreases along the light emission direction of the epitaxial structure. The doping concentration of the second-type doped layer of the tunnel junction remains constant or gradually decreases along the light-emitting direction of the epitaxial structure.

3. An epitaxial structure as described in claim 1, characterized in that, The first type of reflective layer is a DBR reflective layer; Along the light emission direction of the epitaxial structure, the logarithm of the first type of reflective layer gradually decreases; the logarithm of the first type of reflective layer ranges from 2 to 60, including the endpoint values.

4. An epitaxial structure as described in claim 1, characterized in that, Along the light emission direction of the epitaxial structure, the number of logarithms of the active layer gradually decreases; The logarithm of the active layer ranges from 2 to 20, including endpoint values.

5. An epitaxial structure as described in claim 1, characterized in that, The growth temperature of the first type of reflective layer is higher than that of the first type of waveguide layer, active layer and second type of waveguide layer in the light-emitting unit; the growth temperature of the first type of waveguide layer, active layer and second type of waveguide layer is higher than that of the tunnel junction. Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer of the j-th light-emitting unit is higher than that of the first type reflective layer of the (j+1)-th light-emitting unit. Along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer of the j-th light-emitting unit is higher than that of the first type waveguide layer of the (j+1)-th light-emitting unit. Along the growth direction of the epitaxial structure, the growth temperature of the active layer of the j-th light-emitting unit is higher than that of the active layer of the (j+1)-th light-emitting unit. Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer of the j-th light-emitting unit is higher than that of the second type waveguide layer of the (j+1)-th light-emitting unit; where 2≤j≤N-1; Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction is higher than that of the (i+1)-th tunnel junction, where 1≤i<N-1.

6. An epitaxial structure as described in claim 5, characterized in that, The growth temperature of the first type of reflective layer is 10°C-150°C higher than the growth temperature of the first type of waveguide layer, active layer and second type of waveguide layer in the light-emitting unit that are in contact with it, including the endpoint values. The growth temperature of the first type waveguide layer, the active layer, and the second type waveguide layer in the light-emitting unit is 40°C-150°C higher than the growth temperature of the tunnel junction located on the second type waveguide layer of the light-emitting unit, including the endpoint values. Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer of the j-th light-emitting unit is 0-30℃ higher than that of the first type reflective layer of the (j+1)-th light-emitting unit, including the right endpoint value; Along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer of the j-th light-emitting unit is 0-30℃ higher than that of the first type waveguide layer of the (j+1)-th light-emitting unit, including the right endpoint value. Along the growth direction of the epitaxial structure, the growth temperature of the active layer of the j-th light-emitting unit is 0-30℃ higher than that of the active layer of the (j+1)-th light-emitting unit, including the right endpoint value. Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer of the j-th light-emitting unit is 0-30℃ higher than that of the second type waveguide layer of the (j+1)-th light-emitting unit, including the right endpoint value; where 2≤j≤N-1; Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction is 0-30℃ higher than that of the (i+1)-th tunnel junction, including the right endpoint value; where 1≤i<N-1.

7. An LED chip, characterized in that, include: A substrate, at least two epitaxial structures, a transparent conductive layer, a first electrode, and a second electrode; Each of the epitaxial structures is the epitaxial structure according to any one of claims 1-6, and the first type reflective layer of the epitaxial structure is stacked on the surface of each first type waveguide layer away from the active layer; the at least two epitaxial structures are sequentially stacked on one side surface of the substrate; The transparent conductive layer is located between two adjacent epitaxial structures, and the two adjacent epitaxial structures are connected in series; The first electrode is disposed on the side of the substrate away from the epitaxial stack and is electrically connected to the first type waveguide layer; The second electrode is located on the side of the epitaxial structure furthest from the substrate, away from the substrate, and is electrically connected to the second type waveguide layer.

8. An LED chip, characterized in that, It includes a substrate, a first epitaxial structure, a second epitaxial structure, a bonding layer, a metal mirror, a first electrode, and a second electrode; The first epitaxial structure is the epitaxial structure according to any one of claims 1-6, and the first type of reflective layer of the epitaxial structure is stacked on the surface of each first type of waveguide layer away from the active layer; The second epitaxial structure is the epitaxial structure according to any one of claims 1-6, and the first type of reflective layer is stacked on the surface of each of the tunnel junctions facing the first type of waveguide layer; The first epitaxial structure is located on one side surface of the substrate; The second epitaxial structure is bonded to the side of the substrate opposite to the first epitaxial structure via a bonding layer, and is connected in series with the first epitaxial structure; The metal mirror is located between the bonding layer and the second epitaxial structure; The first electrode is disposed on the side of the second epitaxial structure opposite to the substrate and is electrically connected to the first type of waveguide layer; The second electrode is disposed on the surface of the first epitaxial structure opposite to the substrate and is electrically connected to the second type waveguide layer.

9. A method for manufacturing an LED chip, characterized in that, include: Provide substrate; An epitaxial structure is grown on one side surface of the substrate to form an epitaxial wafer; the growth of the epitaxial structure includes growing N light-emitting units stacked sequentially along a direction away from the substrate and a tunnel junction located between two adjacent light-emitting units, where N≥2 and N is a positive integer; The light-emitting unit includes a first type waveguide layer, an active layer, and a second type waveguide layer grown sequentially along a direction away from the substrate. The tunneling junction comprises a first type of material layer and a second type of material layer stacked together; The band gap of the first type doped layer of the tunnel junction remains unchanged or gradually increases along the light emission direction of the epitaxial structure; The band gap of the second-type doped layer of the tunnel junction remains unchanged or gradually increases along the light-emitting direction of the epitaxial structure; It also includes growing several first-type reflective layers; firstly, the first-type reflective layers are grown before each first-type waveguide layer is grown, and then the first-type waveguide layers are grown on the first-type reflective layers; The growth temperature of the first type of reflective layer is higher than that of the first type of waveguide layer, active layer and second type of waveguide layer in the light-emitting unit; the growth temperature of the first type of waveguide layer, active layer and second type of waveguide layer is higher than that of the tunnel junction. Along the growth direction of the epitaxial structure, the growth temperature of the first type reflective layer of the j-th light-emitting unit is higher than that of the first type reflective layer of the (j+1)-th light-emitting unit. Along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer of the j-th light-emitting unit is higher than that of the first type waveguide layer of the (j+1)-th light-emitting unit. Along the growth direction of the epitaxial structure, the growth temperature of the active layer of the j-th light-emitting unit is higher than that of the active layer of the (j+1)-th light-emitting unit. Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer of the j-th light-emitting unit is higher than that of the second type waveguide layer of the (j+1)-th light-emitting unit; where 2≤j≤N-1; Along the growth direction of the epitaxial structure, the growth temperature of the i-th tunnel junction is higher than that of the (i+1)-th tunnel junction, where 1≤i<N-1; A first transparent conductive bonding layer is grown on the side of an epitaxial wafer away from the substrate; the first transparent conductive bonding layer is electrically connected to the second type waveguide layer; Another epitaxial wafer is bonded to a transfer substrate on the side opposite to the substrate. After removing the substrate, a second transparent conductive bonding layer is grown on the side of the epitaxial structure opposite to the transfer substrate. The second transparent conductive bonding layer is electrically connected to the first type waveguide layer. The first transparent conductive bonding layer and the second transparent conductive bonding layer are bonded together, and the transfer substrate is removed; A first electrode and a second electrode are fabricated on the bonded epitaxial wafer; the first electrode is disposed on the side of the substrate away from the epitaxial structure and electrically connected to a first type waveguide layer; the second electrode is disposed on the side of the epitaxial structure away from the substrate and electrically connected to a second type waveguide layer.

10. A method for manufacturing an LED chip, characterized in that, include: Provide substrate; An epitaxial structure is grown on one side surface of the substrate to form an epitaxial wafer; the growth of the epitaxial structure includes growing N light-emitting units stacked sequentially along a direction away from the substrate and a tunnel junction located between two adjacent light-emitting units, where N≥2 and N is a positive integer; The light-emitting unit includes a first type waveguide layer, an active layer, and a second type waveguide layer grown sequentially along a direction away from the substrate. The tunneling junction includes a first type of material layer and a second type of material layer stacked together; The band gap of the first type doped layer of the tunnel junction remains unchanged or gradually increases along the light emission direction of the epitaxial structure; The band gap of the second-type doped layer of the tunnel junction remains unchanged or gradually increases along the light-emitting direction of the epitaxial structure; It also includes growing a plurality of first-type reflective layers; growing the first-type reflective layer before growing each of the first-type waveguide layers, and then growing the first-type waveguide layer on the first-type reflective layer; or, growing the first-type reflective layer on each tunnel junction after each of the tunnel junctions has been grown; the first-type reflective layer is grown in the former manner to form a first epitaxial wafer, and the first-type reflective layer is grown in the latter manner to form a second epitaxial wafer; A metal mirror is fabricated on the side of the second epitaxial wafer that is away from the substrate; The metal mirror of the second epitaxial wafer is bonded to the side of the first epitaxial wafer substrate away from the epitaxial structure through a bonding layer, and the substrate of the second epitaxial wafer is removed. A first electrode and a second electrode are fabricated on the first epitaxial wafer and the second epitaxial wafer after bonding. The first electrode is disposed on the side of the second epitaxial wafer opposite to the first epitaxial wafer and electrically connected to a first type waveguide layer. The second electrode is disposed on the side of the first epitaxial wafer opposite to the second epitaxial wafer and electrically connected to a second type waveguide layer.

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