Multi-junction monolithic light emitting element, method for manufacturing the same, and light emitting device

Abstract

The present application relates to the technical field of semiconductor device manufacturing, and particularly provides a multi-junction monolithic light emitting element, a manufacturing method thereof and a light emitting device. The multi-junction monolithic light emitting element is formed by stacking N (N >= 2, N is a natural number) light emitting units from bottom to top; wherein, the first to the N-1th light emitting units are the same, the first light emitting unit comprises a first N-type layer, a first light emitting layer and a first P-type layer stacked in sequence from bottom to top, and no electron blocking layer is arranged between the first light emitting layer and the first P-type layer; the Nth light emitting unit comprises an Nth N-type layer, an Nth light emitting layer and an Nth P-type layer stacked in sequence from bottom to top, and an electron blocking layer is arranged between the Nth light emitting layer and the Nth P-type layer. The light emitting device adopts the multi-junction monolithic light emitting element, which can effectively reduce the resistance value of the series resistance, reduce the voltage of the light emitting device, and improve the light emitting brightness.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device manufacturing technology, and in particular to a multi-junction monolithic light-emitting element, its manufacturing method, and a light-emitting device. Background Technology

[0002] A light-emitting diode (LED) is a solid-state semiconductor light-emitting element that contains various light-emitting materials and components. Due to its advantages such as low cost, low power consumption, high luminous efficiency, small size, energy saving, environmental friendliness, and good reliability, it is widely used in various scenarios including lighting, visible light communication, and light-emitting displays.

[0003] To improve the luminous efficiency of light-emitting diodes (LEDs), researchers are increasingly exploring the use of tunnel junctions (TJs) to stack two or more LEDs (or PN junctions) to form multi-junction LEDs. Compared to a single LED, a multi-junction LED can emit more light from its emitting surface, thereby increasing its brightness.

[0004] In existing multi-junction light-emitting devices, multiple PN junction structures (light-emitting units) are connected in series to form a single multi-junction light-emitting element. In this structure, the movement of charge carriers (electrons and holes) becomes difficult. The excessively high energy level of the electron blocking layer (EBL) in each PN junction structure (light-emitting unit) hinders the flow of electrons between adjacent PN junction structures (light-emitting units), while the difficulty of holes transitioning to the light-emitting layer (active region) increases. This leads to an increase in the series resistance of the light-emitting device, resulting in an increase in voltage and consequently affecting the luminous brightness. Summary of the Invention

[0005] To achieve at least one or more advantages of the present invention, one embodiment of the present invention provides a multi-junction monolithic light-emitting element, wherein the multi-junction monolithic light-emitting element is composed of N (N≧2, N is a natural number) light-emitting units stacked from bottom to top; wherein the first to the (N-1)th light-emitting units do not have an electron blocking layer, and the Nth light-emitting unit has an electron blocking layer.

[0006] In some embodiments, the first to the (N-1)th light-emitting units do not contain aluminum (Al) elements, while the Nth light-emitting unit contains aluminum (Al) elements.

[0007] In some embodiments, the first light-emitting unit comprises, from bottom to top, a first N-type layer, a first stress-relieving layer, a first light-emitting layer, and a first P-type layer stacked in sequence.

[0008] In some embodiments, the first light-emitting unit may further include a first P-type contact layer located above the first P-type layer. The thickness of the first P-type contact layer is greater than or equal to 1 nanometer and less than or equal to 10 nanometers.

[0009] In some embodiments, the Nth light-emitting unit comprises, from bottom to top, an Nth N-type layer, an Nth stress-relieving layer, an Nth light-emitting layer, an electron-blocking layer, and an Nth P-type layer stacked sequentially. The Nth N-type layer is made of N-type doped gallium nitride or indium gallium nitride, with a doping concentration of 5E18 to 5E20 atmos / cm³. The thickness of the Nth N-type layer is greater than or equal to 2 nanometers and less than or equal to 300 nanometers.

[0010] In some embodiments, the Nth light-emitting unit may further include an (N-1)th N-type contact layer, located below the Nth N-type layer and facing the (N-1)th light-emitting unit.

[0011] In some embodiments, the (N-1)th N-type contact layer is made of N-type doped gallium nitride or indium gallium nitride, with a doping concentration of 5E19 atm / cm3 to 5E21 atm / cm3. The thickness of the (N-1)th N-type contact layer is greater than or equal to 2 nanometers and less than or equal to 50 nanometers.

[0012] In some embodiments, the multi-junction monolithic light-emitting element may further include N-1 (N≧2, N is a natural number) tunnel junctions (TJs) located between the N light-emitting units to superimpose the N light-emitting units and conduct current. The tunnel junctions may have an unintentionally doped structure. The thickness of the tunnel junction is greater than the thickness of the (N-1)th N-type contact layer.

[0013] In some embodiments, the thickness of the tunnel junction is greater than or equal to 2 nanometers and less than or equal to 20 nanometers. The material of the tunnel junction is unintentionally doped gallium nitride or unintentionally doped indium gallium nitride. The carbon atom concentration in the tunnel junction is greater than or equal to 5E18 atoms / cm3.

[0014] In some embodiments, the multi-junction monolithic light-emitting element may further include a substrate. One side surface of the substrate includes, from bottom to top, sequentially stacked first to Nth light-emitting units. An undoped layer may also be included between the substrate and the first light-emitting unit.

[0015] In some embodiments, the substrate is at least one of a sapphire substrate, a silicon substrate, and a silicon carbide substrate. The undoped layer is unintentionally doped gallium nitride (U-GaN).

[0016] To achieve at least one or more advantages of the present invention, one embodiment of the present invention provides a light-emitting device, comprising: a substrate; and a light-emitting element mounted on the substrate, wherein the light-emitting element is a multi-junction monolithic light-emitting element as described above.

[0017] To achieve at least one or more advantages of the present invention, one embodiment of the present invention provides a method for manufacturing a multi-junction monolithic light-emitting element, comprising the following steps:

[0018] A substrate is provided, and a first light-emitting unit is grown on the substrate. The first light-emitting unit includes, from bottom to top, a first N-type layer, a first stress-relieving layer, a first light-emitting layer, a first P-type layer and a first P-type contact layer stacked in sequence.

[0019] The first N-type contact layer is grown on the first P-type contact layer in the first light-emitting unit.

[0020] A second light-emitting unit is formed on the first N-type contact layer, and the second light-emitting unit has the same configuration as the first light-emitting unit;

[0021] The above steps are repeated multiple times until N (N≧2, N is a natural number) light-emitting units are formed on the same side of the substrate. The Nth light-emitting unit includes, from bottom to top, the Nth N-type layer, the Nth stress-relieving layer, the Nth light-emitting layer, the electron blocking layer, the Nth P-type layer and the Nth P-type contact layer stacked in sequence, thereby forming a multi-junction monolithic light-emitting element.

[0022] In some embodiments, the method for manufacturing a multi-junction monolithic light-emitting element may further include a tunnel junction formation step: forming a tunnel junction on a first P-type contact layer, and then forming a first N-type contact layer on the tunnel junction.

[0023] In some embodiments, the first to the Nth light-emitting units and the tunnel junction are grown in the same device.

[0024] Other features and beneficial effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other beneficial effects of the invention can be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0025] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Unless otherwise specified, the positional relationships shown in the drawings in the following description are based on the direction in which the components are drawn in the figure.

[0026] Figure 1 This is a cross-sectional structural diagram of the first embodiment of the multi-junction monolithic light-emitting element in this invention;

[0027] Figure 2 This is a cross-sectional structural diagram of the second embodiment of the multi-junction monolithic light-emitting element in this invention;

[0028] Figure 3 This is a schematic flowchart illustrating a manufacturing method for a multi-junction monolithic light-emitting element according to an embodiment of the present invention.

[0029] Figures 4a to 4c Based on Figure 3 The diagram shows a process flow diagram of one embodiment of the preparation method.

[0030] Figure reference numerals: 1-Multi-junction monolithic light-emitting element; 10-Substrate; 2-First light-emitting unit; 21-First N-type layer; 22-First light-emitting layer; 23-First P-type layer; 24-First stress-relieving layer; 25-First P-type contact layer; 26-First low-temperature insertion layer; 3-Nth light-emitting unit; 31-Nth N-type layer; 32-Nth light-emitting layer; 33-Nth P-type layer; 34-Nth stress-relieving layer; 35-Nth P-type contact layer; 36-N-1th N-type contact layer; 37-Nth low-temperature insertion layer; 4-Tunnel junction; 100-Electron blocking layer; 200-Undoped layer. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] In the description of this invention, it should be noted that all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and should not be construed as limiting the invention; it should be further understood that the terms used in this invention should be understood to have the same meaning as those in the context of this specification and in the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this invention.

[0033] Please see Figure 1 , Figure 1This is a cross-sectional structural diagram of the first embodiment of the multi-junction monolithic light-emitting element of the present invention. To achieve at least one or other advantages of the present invention, one embodiment of the present invention provides a multi-junction monolithic light-emitting element 1, which is composed of N (N≧2, N is a natural number) light-emitting units stacked from bottom to top; wherein, the first to the (N-1)th light-emitting units do not have an electron blocking layer, and the Nth light-emitting unit has an electron blocking layer.

[0034] In some embodiments, the materials of different layers in the N light-emitting units can be the same or different. In one specific embodiment, in the first to the (N-1)th light-emitting units, the N-type layer can be n-GaN, the light-emitting layer can be an InGaN / GaN superlattice structure, and the P-type layer can be p-GaN. In the Nth light-emitting unit, the N-type layer can be n-GaN, the light-emitting layer can be entirely an InGaN / GaN superlattice structure or a combination of a partial InGaN / GaN superlattice structure and a partial InGaN / AlGaN superlattice structure, and the P-type layer can be p-GaN. The electron blocking layer in the Nth light-emitting unit is an Al-containing material layer, which can be at least one of AlGaN, AlInGaN, and AlN. The preferred material for the electron blocking layer is AlGaN.

[0035] In some embodiments, the first to the (N-1)th light-emitting units do not contain aluminum (Al), while the Nth light-emitting unit does contain aluminum (Al). This can be understood as the light-emitting layer of the first to the (N-1)th light-emitting units not containing aluminum (Al), while the light-emitting layer and / or electron-blocking layer of the Nth light-emitting unit contain aluminum (Al). The absence of aluminum (Al) in the light-emitting layers of the first to the (N-1)th light-emitting units allows for more uniform electron and hole distribution within the light-emitting unit, resulting in more uniform overall light emission from the multi-junction monolithic light-emitting element 1. The presence of aluminum (Al) in the Nth light-emitting unit increases the band gap, creating a barrier that reduces electron overflow. Electrons can then recombine with holes radiatively in the light-emitting layer of the Nth light-emitting unit, reducing heat generation in the multi-junction monolithic light-emitting element 1, lowering the voltage, and increasing the overall brightness of the multi-junction monolithic light-emitting element 1.

[0036] like Figure 1 As shown, for ease of explanation, this embodiment uses a multi-junction monolithic light-emitting element 1, which is composed of two (N=2) light-emitting units stacked from bottom to top, as an example. The multi-junction monolithic light-emitting element 1 is composed of a first light-emitting unit 2 and a second (N=2) light-emitting unit 3 stacked from bottom to top. The first light-emitting unit 2 does not have an electron blocking layer 100 and does not contain aluminum (Al) element, while the second light-emitting unit 3 has an electron blocking layer (EBL) 100 and contains aluminum (Al) element.

[0037] The multi-junction monolithic light-emitting element 1 may further include a substrate 10. The substrate 10 can be a support substrate or a growth substrate, etc., and can be selected according to the needs of the product manufacturing process. In some specific embodiments, preferably, the substrate 10 is one of a sapphire substrate, a silicon substrate, or a silicon carbide substrate. These are commonly used substrate materials in actual production, and the manufacturing processes are relatively mature, which can reduce the overall cost of the light-emitting element. During the manufacturing process, the first light-emitting unit 2 and the second light-emitting unit 3 are formed on the substrate 10. As shown in the figure, one side surface of the substrate 10 includes the first light-emitting unit 2 and the second light-emitting unit 3 stacked sequentially from bottom to top.

[0038] In some specific embodiments, as shown in the figure, an undoped layer 200 may be included between the substrate 10 and the first light-emitting unit 2 to reduce lattice mismatch defects between the substrate 10 and the first light-emitting unit 2, improve the crystal quality of the first light-emitting unit 2, and thus improve the photoelectric performance of the first light-emitting unit 2. Generally, the undoped layer 200 and the N-type or P-type semiconductor layer in the first light-emitting unit 2 that contacts the undoped layer 200 are made of the same material, thereby ensuring the adhesion and performance between the undoped layer 200 and the first light-emitting unit 2. In some specific embodiments, preferably, the undoped layer 200 is unintentionally doped gallium nitride (U-GaN).

[0039] The first light-emitting unit 2 is formed on one side surface of the substrate 10. In some embodiments, the first light-emitting unit 2 may include, from bottom to top, at least a first N-type layer 21, a first stress-relieving layer 24, a first light-emitting layer 22, and a first P-type layer 23 stacked in sequence. In some embodiments, the first N-type layer 21 and the first P-type layer 23 are preferably made of gallium nitride (GaN).

[0040] In some specific embodiments, such as Figure 1 As shown, a first stress-relieving layer 24 may be provided between the first N-type layer 21 and the first light-emitting layer 22 to balance the internal stress in the first light-emitting unit 2, thereby improving the reliability and performance of the first light-emitting unit 2. In some specific embodiments, a first low-temperature insertion layer 26 may be provided between the first light-emitting layer 22 and the first P-type layer 23 to increase the number of holes, thereby increasing the radiative recombination of electrons and holes and improving the luminous efficiency of the first light-emitting unit 2.

[0041] In some specific embodiments, as shown in the figure, the first light-emitting unit 2 may further include a first P-type contact layer 25. The first P-type contact layer 25 is located above the first P-type layer 23, and the second light-emitting unit 3 is located above the first P-type contact layer 25. In other words, the first P-type contact layer 25 is disposed between the first P-type layer 23 and the second light-emitting unit 3 in the first light-emitting unit 2. The thickness of the first P-type contact layer 25 is greater than or equal to 1 nanometer and less than or equal to 10 nanometers. The arrangement of the first P-type contact layer 25 facilitates current conduction between the first light-emitting unit 2 and the second light-emitting unit 3.

[0042] The second light-emitting unit 3 is formed on the surface of the first P-type contact layer 25 on the side away from the first light-emitting unit 2. In some specific embodiments, the second light-emitting unit 3 may include, from bottom to top, at least a second N-type layer 31, a second stress-relieving layer 34, a second light-emitting layer 32, an electron blocking layer (EBL) 100, and a second P-type layer 33 stacked sequentially. In some specific embodiments, preferably, the material of the second N-type layer 31 is N-type doped gallium nitride or indium gallium nitride, but not limited to these two materials; the doping concentration is preferably 5E18 Atoms / cm3 to 5E20 Atoms / cm3. The thickness of the second N-type layer 31 is greater than or equal to 2 nanometers and less than or equal to 300 nanometers.

[0043] The thicknesses of the first N-type layer 21 and the second N-type layer 31 can be the same or different, depending on the actual needs of the product. In some specific embodiments, preferably, the thickness of the first N-type layer 21 is greater than or equal to the thickness of the second N-type layer 31. If the second to N N-type layers in the second to N light-emitting units are grown at high temperatures, it will cause the first light-emitting layer 22 in the first light-emitting unit 2 located below it to be lost. Therefore, the second to N N-type layers are generally grown at low temperatures. However, low-temperature growth is prone to other defects. By controlling the thickness of the second to N N-type layers to be less than or equal to the thickness of the first N-type layer 21 under low-temperature growth, the generation of defects can be reduced, the growth quality can be improved, and thus the performance of the multi-junction monolithic light-emitting element 1 can be improved.

[0044] The second N-type layer 31 and the second P-type layer 33 are preferably made of gallium nitride (GaN). A second stress-relieving layer 34 may also be provided between the second N-type layer 31 and the second light-emitting layer 32 to balance the internal stress in the second light-emitting unit 3, thereby improving the reliability and performance of the second light-emitting unit 3. An electron blocking layer (EBL) 100 may also be provided between the second light-emitting layer 32 and the second P-type layer 33 to control the flow of electrons in the second light-emitting unit 3 and improve the luminous efficiency. A second low-temperature insertion layer 37 may also be provided between the second light-emitting layer 32 and the electron blocking layer (EBL) 100 to increase the number of holes, thereby increasing the radiative recombination of electrons and holes and improving the luminous efficiency of the second light-emitting unit 3.

[0045] In the second light-emitting unit 3, a second P-type contact layer 35 is provided on the side surface of the second P-type layer 33 away from the second light-emitting layer 32, so as to facilitate the placement of other light-emitting units above the second light-emitting unit 3, and to realize the current conduction between the second light-emitting unit 3 and other light-emitting units adjacent to the second light-emitting unit 3 through the second P-type contact layer 35.

[0046] In some embodiments, as shown in the figure, the second light-emitting unit 3 may further include a first N-type contact layer 36, located below the second N-type layer 31 and facing the first light-emitting unit 2. In other words, the first N-type contact layer 36 is disposed between the first P-type contact layer 25 in the first light-emitting unit 2 and the second N-type layer 31 in the second light-emitting unit 3, which facilitates current conduction between the second light-emitting unit 3 and the first light-emitting unit 2.

[0047] In a preferred embodiment, the second N-type contact layer 36 is made of N-type doped gallium nitride or indium gallium nitride, with a doping concentration of 5E19 to 5E21 atmos / cm3. The thickness of the second N-type contact layer 36 is greater than or equal to 2 nanometers and less than or equal to 50 nanometers.

[0048] In some embodiments, the multi-junction monolithic light-emitting element 1 may further include N-1 (N≧2, N is a natural number) tunnel junctions (TJs) located between the N light-emitting units to superimpose the N light-emitting units and conduct current. The tunnel junctions may have an unintentionally doped structure.

[0049] Please cooperate. Figure 1 See Figure 2 , Figure 2 This is a cross-sectional structural schematic diagram of a second embodiment of the multi-junction monolithic light-emitting element of the present invention. To achieve at least one or more advantages of the present invention, one embodiment of the present invention provides a multi-junction monolithic light-emitting element 1, which... Figure 1 Compared to the multi-junction monolithic light-emitting element 1 shown, Figure 2The multi-junction monolithic light-emitting element 1 shown includes at least a first light-emitting unit 2, a tunnel junction 4, and a second light-emitting unit 3 stacked from bottom to top. The structural arrangement of the first light-emitting unit 2 and the second light-emitting unit 3 is similar to... Figure 1 The embodiment shown is the same. The arrangement of the tunnel junction 4 facilitates current conduction between the first light-emitting unit 2 and the second light-emitting unit 3.

[0050] A tunnel junction 4 is formed on the surface of the first light-emitting unit 2 away from the substrate 10. In the illustration, the tunnel junction 4 is formed on the surface of the first P-type contact layer 25 in the first light-emitting unit 2 away from the first P-type layer 23. The material of the tunnel junction 4 is preferably unintentionally doped gallium nitride (GaN) or unintentionally doped indium gallium nitride (InGaN), but is not limited to these two materials. Excessive or insufficient thickness of the tunnel junction 4 can easily lead to excessively high voltage in the multi-junction monolithic light-emitting element 1, thereby affecting the performance of the multi-junction monolithic light-emitting element 1. Preferably, the thickness of the tunnel junction 4 is greater than or equal to 2 nanometers and less than or equal to 20 nanometers, which ensures that the first light-emitting unit 2 and the second light-emitting unit 3 are connected and electrically conductive through the tunnel junction 4, while also ensuring the overall stability of the multi-junction monolithic light-emitting element 1.

[0051] Generally, the carbon atom concentration in the tunnel junction 4 differs depending on whether the multi-junction monolithic light-emitting element 1 is formed through a single growth cycle or two growth cycles. The carbon atom concentration in the tunnel junction 4 is related to the growth temperature of the tunnel junction 4. A higher growth temperature results in a lower carbon atom concentration, and vice versa. In some specific embodiments, preferably, the growth temperature of the tunnel junction 4 is 750℃-950℃, and the carbon atom concentration in the tunnel junction 4 is greater than or equal to 5E18 atoms / cm³. The thickness of the tunnel junction 4 is greater than the thickness of the first N-type contact layer 36. Among the tunnel junction 4, the first N-type contact layer 36, and the first P-type contact layer 25, the first P-type contact layer 25 is the thinnest. If the first P-type contact layer 25 is thicker, the voltage in the multi-junction monolithic light-emitting element 1 will be higher than expected, reducing the current conduction effect between the first light-emitting unit 2 and the second light-emitting unit 3, thereby affecting the overall performance and stability of the multi-junction monolithic light-emitting element 1.

[0052] In the multi-junction monolithic light-emitting element 1, the first N-type contact layer 36 and the first P-type contact layer 25 are both highly doped, with concentrations higher than those of the underlying layers of the same doping type. The first N-type layer 21 and the first P-type layer 23 of the first light-emitting unit 2, and the second N-type layer 31 and the second P-type layer 33 of the second light-emitting unit 3, also have relatively high doping concentrations. However, the doping concentrations of these N-type and P-type layers are lower than those of the first N-type contact layer 36 and the first P-type contact layer 25, so as to provide more electrons and holes and improve luminous efficiency.

[0053] The concentrations of the first N-type layer 21 and the first P-type layer 23 are relatively high to provide more electrons and holes. The concentrations of the first N-type layer 21 and the first P-type layer 23 are lower than the concentration of the first P-type contact layer 25.

[0054] High doping concentrations of the N-type and P-type layers provide more holes and electrons, increasing the recombination efficiency and thus improving the brightness of the multi-junction monolithic light-emitting element 1. Furthermore, generally, higher doping concentrations of the first N-type contact layer 36 and the first P-type contact layer 25 result in lower resistance with the N-type and P-type layers, respectively. This facilitates the formation of ohmic contacts with the N-type and P-type layers, promoting current spread and improving the current conduction between the first light-emitting unit 2 and the second light-emitting unit 3, thereby enhancing the overall performance and stability of the multi-junction monolithic light-emitting element 1.

[0055] To achieve at least one or more advantages of the present invention, one embodiment of the present invention provides a light-emitting device, comprising: a substrate; and a light-emitting element mounted on the substrate, wherein the light-emitting element is a multi-junction monolithic light-emitting element 1 as described above.

[0056] Please combine Figure 1 See Figure 3 and Figures 4a to 4c , Figure 3 This is a schematic flowchart illustrating the manufacturing method of a multi-junction monolithic light-emitting element according to an embodiment of the present invention. Figures 4a to 4c Based on Figure 3 A schematic diagram of the process of one embodiment of the preparation method shown. Using... Figure 3 The manufacturing method of the multi-junction monolithic light-emitting element shown obtains as follows: Figure 1 The process flow of the multi-junction monolithic light-emitting element is described below, but the manufacturing method of the multi-junction monolithic light-emitting element is not limited to this.

[0057] To achieve at least one or more advantages of the present invention, one embodiment of the present invention provides a method for manufacturing a multi-junction monolithic light-emitting element 1, which may include at least the following steps: growing a first light-emitting unit 2, growing a first N-type contact layer 36, and growing a second light-emitting unit 3. For ease of explanation, this embodiment uses a multi-junction monolithic light-emitting element 1 composed of two (i.e., N=2) light-emitting units stacked from bottom to top as an example to illustrate its manufacturing method.

[0058] Step S11: Grow the first light-emitting unit 2

[0059] like Figure 4aAs shown, a substrate 10 is provided, and a first light-emitting unit 2 is grown on one side surface of the substrate 10 using metal-organic chemical vapor deposition (MOCVD). The substrate 10 can be a sapphire substrate, a silicon substrate, or a silicon carbide substrate. The first light-emitting unit 2 includes, from bottom to top, a first N-type layer 21, a first stress-relieving layer 24, a first light-emitting layer 22, a first P-type layer 23, and a first P-type contact layer 25, stacked sequentially. A first low-temperature insertion layer 26 may also be provided between the first light-emitting layer 22 and the first P-type layer 23 in the first light-emitting unit 2.

[0060] Step S12: Grow the first N-type contact layer 36

[0061] like Figure 4b As shown, a first N-type contact layer 36 is grown above the first light-emitting unit 2. Specifically, the first N-type contact layer 36 is grown on the first P-type contact layer 25 in the first light-emitting unit 2. In other words, the first N-type contact layer 36 is located on the surface of the first P-type contact layer 25 away from the first P-type layer 23. In some specific embodiments, preferably, the growth temperature of the first N-type contact layer 36 is 750°C-950°C.

[0062] Step S13: Grow the second light-emitting unit 3

[0063] like Figure 4c As shown, a second light-emitting unit 3 is formed on the first N-type contact layer 36. The second light-emitting unit 3 includes, from bottom to top, at least a second N-type layer 31, a second stress-relieving layer 34, a second light-emitting layer 32, an electron blocking layer 100, and a second P-type layer 33 stacked in sequence, thereby forming a multi-junction monolithic light-emitting element 1. In the second light-emitting unit 3, a second low-temperature insertion layer 37 may also be provided between the second light-emitting layer 32 and the electron blocking layer 100.

[0064] In some specific embodiments, the first light-emitting unit 2 and the second light-emitting unit 3 are grown in the same device. The second light-emitting unit 3 may have the same structural configuration as the first light-emitting unit 2.

[0065] If additional light-emitting units need to be grown on the second light-emitting unit 3, a second P-type contact layer 35 can be grown first on the surface of the second P-type layer 33 away from the second light-emitting layer 32. Then, steps S12 and S13 are repeated multiple times until the last light-emitting unit is grown on the second light-emitting unit 3, thereby forming the desired multi-junction monolithic light-emitting element 1. In this case, no electron blocking layer 100 is provided between the second light-emitting layer 32 and the second P-type layer 33 until the last light-emitting unit is grown on the second light-emitting unit 3, at which point the electron blocking layer 100 is provided. In some specific embodiments, preferably, the growth temperature of the second P-type contact layer 35 is 750℃-950℃. In the multi-junction monolithic light-emitting element 1, the provision of a second P-type contact layer 35 or the Nth P-type contact layer in the second light-emitting unit 3 of a double junction or the uppermost light-emitting unit of a triple junction is beneficial for forming ohmic contacts with the electrodes and for current conduction between different light-emitting units.

[0066] Please combine Figure 2 See Figure 3 and Figures 4a to 4c In some embodiments, the manufacturing method of the multi-junction monolithic light-emitting element 1 may further include a tunnel junction 4 formation step between step S11 (growing the first light-emitting unit 2) and step S12 (growing the first N-type contact layer 36). A tunnel junction 4 is formed on the surface of the first P-type contact layer 25 away from the first P-type layer 23 in the first light-emitting unit 2, and then a first N-type contact layer 36 is formed on the surface of the tunnel junction 4 away from the first P-type contact layer 25. In other words, the multi-junction monolithic light-emitting element 1 is a double-junction structure (a junction refers to a light-emitting unit) or a multi-junction structure. Different junctions are connected through the tunnel junction 4, enabling current conduction between different light-emitting units. The tunnel junctions 4 between different light-emitting units can have the same structural configuration.

[0067] In some specific embodiments, the first light-emitting unit 2 to the second light-emitting unit 3 and the tunnel junction 4 are grown in the same device, which can greatly simplify the growth process, simplify the equipment requirements, improve the light emission brightness, reduce the voltage, reduce leakage current, and thus improve the performance of the multi-junction monolithic light-emitting element 1.

[0068] In summary, compared with existing technologies, in multi-junction light-emitting elements, the multi-junction monolithic light-emitting element 1 provided by this invention reduces the overall series resistance of multiple light-emitting units by simplifying the electron blocking layer (EBL) in the bottom light-emitting unit, thereby significantly reducing the product voltage. For example, the voltage in existing or traditional dual-junction monolithic light-emitting elements is 8.85V, while the voltage in the multi-junction monolithic light-emitting element 1 provided by this invention is 8.10V, a reduction of 0.75V. In other words, the lower the voltage in the multi-junction monolithic light-emitting element 1, the higher the luminous efficacy. Compared with existing similar dual-junction monolithic light-emitting element products, the luminous efficacy of the multi-junction monolithic light-emitting element 1 provided by this invention can be improved by 8-9%.

[0069] Generally, an electron blocking layer (EBL) in the light-emitting unit can prevent electrons from overflowing or escaping from the light-emitting layer, allowing more electrons to remain in the light-emitting layer and recombine with holes radiatively, thus increasing brightness. In the multi-junction monolithic light-emitting element 1, the absence of an electron blocking layer (EBL) in the bottom light-emitting unit facilitates the migration of electrons from the bottom unit to the upper light-emitting units, strengthening the interaction of charge carriers (holes / electrons) between different light-emitting units and increasing the probability of radiative recombination, thereby improving brightness. Furthermore, the absence of aluminum in the bottom light-emitting unit reduces the impact of aluminum-induced bandgap increase on the interaction of charge carriers between different light-emitting units. Adding aluminum to the topmost light-emitting unit prevents electrons from overflowing from the light-emitting layer, increasing the probability of charge carrier interaction and radiative recombination, thereby improving the brightness of the multi-junction monolithic light-emitting element 1.

[0070] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0071] Although this document frequently uses terms such as multi-junction monolithic light-emitting element, tunnel junction, light-emitting unit, N-type contact layer, and P-type contact layer, the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention. The terms "upper," "lower," "vertical," "horizontal," "top," "bottom," "upper surface," "left," "right," "sidewall," and "directly above" in the specification, claims, and accompanying drawings of the embodiments of the invention indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings. They are only for the convenience of describing the 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, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions,

[0073] The essence of the corresponding technical solutions shall not deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A multi-junction monolithic light-emitting element, characterized in that: The multi-junction monolithic light-emitting element is composed of N (N≧2, N is a natural number) light-emitting units stacked from bottom to top; In this case, the first to the (N-1)th light-emitting units do not have an electron blocking layer; the Nth light-emitting unit has an electron blocking layer. The first to the (N-1)th light-emitting units do not contain aluminum, while the Nth light-emitting unit does contain aluminum.

2. The multi-junction monolithic light-emitting element according to claim 1, characterized in that: The first light-emitting unit comprises, from bottom to top, a first N-type layer, a first stress-relieving layer, a first light-emitting layer, and a first P-type layer stacked in sequence.

3. The multi-junction monolithic light-emitting element according to claim 2, characterized in that: The first light-emitting unit also includes a first P-type contact layer located above the first P-type layer; the thickness of the first P-type contact layer is greater than or equal to 1 nanometer and less than or equal to 10 nanometers.

4. The multi-junction monolithic light-emitting element according to claim 1, characterized in that: The Nth light-emitting unit comprises, from bottom to top, an Nth N-type layer, an Nth stress-relieving layer, an Nth light-emitting layer, an electron-blocking layer, and an Nth P-type layer stacked sequentially; the Nth N-type layer is made of N-type doped gallium nitride or indium gallium nitride, with a doping concentration of 5E18 Atmos / cm³. 3 Up to 5E20Atoms / cm 3 The thickness of the Nth N-type layer is greater than or equal to 2 nanometers and less than or equal to 300 nanometers.

5. The multi-junction monolithic light-emitting element according to claim 4, characterized in that: The Nth light-emitting unit further includes an (N-1)th N-type contact layer, located below the Nth N-type layer and facing the (N-1)th light-emitting unit.

6. The multi-junction monolithic light-emitting element according to claim 5, characterized in that: The (N-1)th N-type contact layer is made of N-type doped gallium nitride or indium gallium nitride, with a doping concentration of 5E19 Atons / cm³. 3 Up to 5E21Atoms / cm 3 The thickness of the (N-1)th N-type contact layer is greater than or equal to 2 nanometers and less than or equal to 50 nanometers.

7. The multi-junction monolithic light-emitting element according to claim 5, characterized in that: The multi-junction monolithic light-emitting element further includes N-1 (N≧2, N is a natural number) tunnel junctions located between the N light-emitting units to superimpose the N light-emitting units and conduct current; the tunnel junctions have an unintentionally doped structure; the thickness of each tunnel junction is greater than the thickness of the N-1th N-type contact layer.

8. The multi-junction monolithic light-emitting element according to claim 7, characterized in that: The thickness of the tunnel junction is greater than or equal to 2 nanometers and less than or equal to 20 nanometers; the material of the tunnel junction is unintentionally doped gallium nitride or unintentionally doped indium gallium nitride; the carbon atom concentration in the tunnel junction is greater than or equal to 5E18 atoms / cm³. 3 .

9. The multi-junction monolithic light-emitting element according to claim 1, characterized in that: The multi-junction monolithic light-emitting element further includes a substrate, on one side surface of which the first light-emitting unit to the Nth light-emitting unit are stacked sequentially from bottom to top, and an undoped layer is also included between the substrate and the first light-emitting unit.

10. The multi-junction monolithic light-emitting element according to claim 9, characterized in that: The substrate is one of sapphire substrate, silicon substrate, and silicon carbide substrate; the undoped layer is gallium nitride that is not intentionally doped.

11. A light-emitting device, comprising: substrate; A light-emitting element is mounted on the substrate, wherein the light-emitting element is a multi-junction monolithic light-emitting element as described in any one of claims 1 to 10.

12. A method for manufacturing a multi-junction monolithic light-emitting element, characterized in that, The manufacturing method includes at least the following steps: A substrate is provided on which a first light-emitting unit is grown, the first light-emitting unit comprising, from bottom to top, a first N-type layer, a first stress-relieving layer, a first light-emitting layer, a first P-type layer and a first P-type contact layer stacked sequentially; A first N-type contact layer is grown on the first P-type contact layer in the first light-emitting unit. A second light-emitting unit is formed on the first N-type contact layer, and the second light-emitting unit has the same configuration as the first light-emitting unit; The above steps are repeated multiple times until N (N≧2, N is a natural number) light-emitting units are formed on the same side of the substrate. The Nth light-emitting unit includes, from bottom to top, the Nth N-type layer, the Nth stress-relieving layer, the Nth light-emitting layer, the electron blocking layer, the Nth P-type layer and the Nth P-type contact layer stacked in sequence, thereby forming a multi-junction monolithic light-emitting element.

13. The method for manufacturing a multi-junction monolithic light-emitting element according to claim 12, characterized in that: It also includes a tunnel junction formation step, in which the tunnel junction is formed on the first P-type contact layer, and then the first N-type contact layer is formed on the tunnel junction.

14. The method for manufacturing a multi-junction monolithic light-emitting element according to claim 13, characterized in that: The first light-emitting unit to the Nth light-emitting unit and the tunnel junction are grown in the same device.

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