LED epitaxial structure and manufacturing method thereof

Abstract

The invention discloses an LED epitaxial structure and a manufacturing method thereof. The LED epitaxial structure comprises an N-type semiconductor layer, an active layer and a P-type semiconductor layer which are sequentially arranged in a stacked mode in the first direction. The first direction is perpendicular to the N-type semiconductor layer and points to the active layer from the N-type semiconductor layer; the active layer comprises N quantum barrier layers which are sequentially stacked in the first direction, and N is a positive integer; in the first direction, the last quantum barrier layer comprises a first sub-layer and a second sub-layer; the first sub-layer comprises an N-type doped I nGaN layer, an undoped I nGaN layer and a P-type doped I nGaN layer which are sequentially stacked in the first direction, the I n component of the first sub-layer is gradually reduced in the first direction, and the second sub-layer is a GaN layer. Due to the arrangement, the LED epitaxial structure can weaken the polarization electric field of the active layer, reduce the adverse effect of QCSE, accelerate hole injection, facilitate electron constraint and improve the luminous efficiency of the LED.

Description

Technical Field

[0001] The present invention relates to the technical field of light emitting diodes, and more specifically, to an LED epitaxial structure and a manufacturing method thereof. Background Art

[0002] At present, AlInGaN-based luminescent materials are increasingly being used in the fields of display and lighting due to their physical and chemical properties such as large bandgap, high breakdown electric field, and high electron saturation mobility. As the active layer of LED, multi-quantum well InGaN / GaN is particularly important for the optical properties of LED. However, in the long-wave band, such as green light, yellow light, red light, etc., as the In component in the active layer InGaN becomes higher and higher, its crystal quality deteriorates, defects increase, and the LED luminous efficiency is reduced. In addition, due to the serious lattice mismatch and low miscibility between InN and GaN, In clusters are likely to appear in the InGaN / GaN active layer, resulting in unfocused luminescence and impure color rendering. In addition, due to its spontaneous polarization and piezoelectric polarization, group III nitrides will form a built-in electric field, which is easy to produce quantum confined Stark effect, aggravating electron leakage, and the small effective mass and high mobility of electrons, which makes it easy for electrons to cross the active layer and enter the P-type semiconductor layer to cause electron leakage. Furthermore, the effective mass of holes is large and their mobility is low, which leads to the fact that in traditional LED structures, holes are mainly concentrated in a few quantum wells close to the P-type semiconductor layer. These reasons will cause uneven distribution of carriers in the active layer, reduce radiative recombination, and thus affect the luminous efficiency of the LED.

[0003] To solve this problem, it is currently common to insert an AlGaN electron blocking layer (EBL) between the InGaN / GaN active layer and the P-type semiconductor layer to increase the conduction band electron barrier and reduce electron leakage. However, this method also hinders the transmission of holes from the P-type semiconductor layer to the active layer, thereby hindering the recombination of electrons and holes in the active layer, thereby affecting the luminous efficiency of the LED.

[0004] Therefore, reducing electron leakage and increasing hole injection efficiency have become urgent issues to be solved in order to improve the luminous efficiency of LEDs. Summary of the invention

[0005] In view of this, the present invention provides an LED epitaxial structure capable of improving the LED luminous efficiency and a method for manufacturing the same.

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

[0007] An LED epitaxial structure comprises an N-type semiconductor layer, an active layer and a P-type semiconductor layer stacked in sequence along a first direction; the first direction is perpendicular to the N-type semiconductor layer and points from the N-type semiconductor layer to the active layer;

[0008] The active layer includes N quantum barrier layers stacked in sequence along a first direction, where N is a positive integer;

[0009] Along the first direction, the last quantum barrier layer includes a first sublayer and a second sublayer; the first sublayer includes an N-type doped InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer stacked in sequence along the first direction, and the In component of the first sublayer gradually decreases along the first direction, and the second sublayer is a GaN layer.

[0010] Furthermore, a quantum well layer and a protective layer stacked in sequence along a first direction are provided between two adjacent quantum barrier layers, wherein the quantum well layer is an InGaN layer, and the protective layer is a GaN layer.

[0011] Furthermore, the P-type doping of the P-type doped InGaN layer is Mg, and the doping concentration of Mg is 1*10 18 cm -3 -5*10 18 cm -3 The N-type doping of the N-type doped I nGaN layer is Si, and the doping concentration of Si is 2*17cm -3 -9*17cm -3 .

[0012] Furthermore, along the first direction, the thickness of the first N-1 quantum barrier layers is less than the thickness of the last quantum barrier layer.

[0013] Furthermore, along the first direction, the first N-1 quantum barrier layers are Al GaN; the first N-1 quantum barrier layers form a first layer group; the first layer group includes A layers of continuously arranged quantum barrier layers, A is a positive integer; each quantum barrier layer of the first layer group is provided with an insertion layer, and each insertion layer is Al GaN; the Al component of each insertion layer is greater than the Al component of its corresponding quantum barrier layer; the Al component of each insertion layer gradually increases along the first direction.

[0014] Furthermore, the first N-1 quantum barrier layers form a second layer group located between the first layer group and the N-type semiconductor layer; the second layer group includes B continuously arranged quantum barrier layers, B is a positive integer; the Al component of the quantum barrier layers of the second layer group gradually decreases along the first direction.

[0015] Furthermore, the sum of A and B is equal to N-1.

[0016] Further, along the first direction, the second layer group includes the first N-3 quantum barrier layers, and the first layer group includes the N-2 th and N-1 th quantum barrier layers.

[0017] Furthermore, the thickness of the insertion layer ranges from 1 nm to 3 nm, including the endpoint values.

[0018] The present invention also provides a method for manufacturing an LED epitaxial structure, wherein an N-type semiconductor layer, an active layer, and a P-type semiconductor layer are sequentially manufactured along a first direction; the first direction is perpendicular to the N-type semiconductor layer and points from the N-type semiconductor layer to the active layer;

[0019] The active layer includes N quantum barrier layers sequentially grown along the first direction, where N is a positive integer;

[0020] Along the first direction, the last quantum barrier layer includes a first sublayer and a second sublayer; the first sublayer includes an N-type doped InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer grown in sequence along the first direction, and the In component of the first sublayer gradually decreases along the first direction, and the second sublayer is a GaN layer.

[0021] Furthermore, a quantum well layer and a protective layer sequentially grown along the first direction are provided between two adjacent quantum barrier layers, the quantum well layer is an InGaN layer, and the protective layer is a GaN layer.

[0022] Furthermore, along the first direction, the first N-1 quantum barrier layers are AlGaN; the first N-1 quantum barrier layers form a first layer group; the first layer group includes A layers of continuously arranged quantum barrier layers, A is a positive integer; each quantum barrier layer of the first layer group is provided with an insertion layer, and each insertion layer is AlGaN; the Al component of each insertion layer is greater than the Al component of its corresponding quantum barrier layer; the Al component of each insertion layer gradually increases along the first direction.

[0023] Furthermore, the first N-1 quantum barrier layers form a second layer group located between the first layer group and the N-type semiconductor layer; the second layer group includes B layers of quantum barrier layers continuously arranged, B is a positive integer; the Al component of the quantum barrier layers of the second layer group gradually decreases along the first direction.

[0024] Furthermore, the sum of A and B is equal to N-1.

[0025] Further, along the first direction, the second layer group includes the first N-3 quantum barrier layers, and the first layer group includes the N-2 th and N-1 th quantum barrier layers.

[0026] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0027] 1. An LED epitaxial structure, comprising an N-type semiconductor layer, an active layer and a P-type semiconductor layer stacked in sequence along a first direction; the first direction is perpendicular to the N-type semiconductor layer and points from the N-type semiconductor layer to the active layer; the active layer comprises N quantum barrier layers stacked in sequence along the first direction, N being a positive integer; along the first direction, the last quantum barrier layer comprises a first sublayer and a second sublayer; the first sublayer comprises an N-type doped InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer grown in sequence along the first direction, and the In component of the first sublayer gradually decreases along the first direction, and the second sublayer is a GaN layer. Due to the above-mentioned structural setting, the last quantum barrier layer of the LED epitaxial structure of the present application includes a first sublayer and a second sublayer, and the first sublayer includes InGaN with a variable In component combined NiP structure (i.e., N-type doped-undoped-P-type doped structure), and an internal electric field is formed in the i layer, and the direction of the electric field is the reverse growth direction; on the one hand, the polarization electric field in the active layer can be weakened to reduce the adverse effects of QCSE; on the other hand, the internal electric field is opposite to the direction of electron movement, slowing down the electron migration rate, and at the same time is the same as the direction of hole movement, accelerating hole injection; the step barrier formed by the variable InGaN component is conducive to binding electrons and has a blocking effect on electrons; thereby improving the luminous efficiency of the LED.

[0028] 2. The first layer group sets an insertion layer with a high Al component in each quantum barrier layer, and the Al component of each insertion layer gradually increases along the first direction, which can enhance the electron binding ability. At the same time, the insertion layer interface parasitic reverse charge forms a reverse electric field inside, which is conducive to hole transmission; that is, a positive electric field is formed in the active layer along the growth direction (i.e., the first direction), which will hinder hole transmission, and the reverse electric field is formed to weaken the positive electric field, so that the obstruction to holes is reduced.

[0029] Moreover, the first sublayer in the last quantum barrier layer is combined with the insertion layer, which not only increases hole injection but also facilitates hole transport, making the carriers more evenly distributed throughout the active layer and improving the overall luminescence efficiency of the device.

[0030] 3. The first N-1 quantum barrier layers are in the second layer group between the first layer group and the N-type semiconductor layer, and the Al component of the quantum barrier layers of the second layer group gradually decreases along the first direction; due to the higher conduction band barrier height of AlGaN, the electron migration rate is retarded, the electron binding ability is enhanced, and the Al component gradually decreases, which reduces the subsequent quantum well valence band barrier height and is beneficial to hole transmission.

[0031] 4. The thickness of the insertion layer ranges from 1nm to 3nm. The thin thickness is conducive to the holes entering the quantum well layer through tunneling. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0033] Figure 1 This is a schematic structural diagram of an implementation method of an LED epitaxial structure in this application;

[0034] Figure 2 This is a schematic diagram of the structure of the first sublayer in this application;

[0035] Figure 3 This is a schematic diagram of the structure of the active layer from the 1st to the N-1th quantum barrier layer in this application;

[0036] Figure 4 It is a schematic diagram of the structure of the first layer group in this application;

[0037] Figure 5 It is a structural schematic diagram of another implementation of the LED epitaxial structure in this application;

[0038] Figure 6 Schematic diagram of the structure of the active layer when N is 7 in this application;

[0039] Figure 7 : is the energy band diagram of the active layer when N is 7 in this application;

[0040] Figure 8 A schematic diagram of the electric field formed inside the first sub-layer in this application;

[0041] Fig. 9 Schematic diagram of the electric field formed inside the first layer group in this application.

[0042] Reference numerals:

[0043] N-type semiconductor layer 1; active layer 2; P-type semiconductor layer 3; quantum barrier layer 4; quantum well layer 5; protective layer 6; first sublayer 7; N-type doped InGaN layer 71; undoped InGaN layer 72; P-type doped InGaN layer; second sublayer 8; first layer group 9; insertion layer 10; second layer group 11; substrate 12; low-temperature nucleation layer 13; undoped GaN layer 14; InGaN / GaN superlattice structure 15; first direction D. DETAILED DESCRIPTION

[0044] To make the content of the present invention clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0045] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0046] Secondly, the present application is described in detail with reference to the schematic diagram. When describing the embodiments of the present application in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present application. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0047] The present application provides an LED epitaxial structure, such as Figure 1 As shown, it includes an N-type semiconductor layer 1, an active layer 2, and a P-type semiconductor layer 3 stacked in sequence along a first direction D. The first direction D is perpendicular to the N-type semiconductor layer 1 and points from the N-type semiconductor layer 1 to the active layer 2. In the present application, the N-type semiconductor layer 1 may be N-GaN, and the P-type semiconductor layer 3 may be P-GaN.

[0048] The active layer 2 includes N quantum barrier layers 4 stacked in sequence along a first direction D, where N is a positive integer. Along the first direction D, the last quantum barrier layer 4 includes a first sublayer 7 and a second sublayer 8; Figure 2 As shown, the first sublayer 7 includes an N-type doped InGaN layer 71, an undoped InGaN layer 72, and a P-type doped InGaN layer 73 sequentially stacked along a first direction D, and the In component of the first sublayer gradually decreases along the first direction D; the second sublayer 8 is a GaN layer. The first sublayer 7 and the second sublayer 8 are sequentially stacked along the first direction D.

[0049] Preferably, the value range of N may be 1<N≤15.

[0050] Preferably, the value range of the In component Z of the first sublayer is 0<Z<0.4, that is, the In component of the first sublayer can gradually decrease within this range along the first direction D. The component contents mentioned in this application are all molar ratios.

[0051] Due to the above-mentioned structural setting, the last quantum barrier layer of the LED epitaxial structure of the present application includes a first sublayer and a second sublayer, and the first sublayer includes InGaN with a variable In component combination NiP structure (i.e., N-type doped-undoped-P-type doped structure), and an internal electric field is formed in the i layer, and the direction of the electric field is the reverse growth direction (such as Figure 8 As shown in the figure); on the one hand, the polarization electric field in the active layer can be weakened, reducing the adverse effects of QCSE; on the other hand, the internal electric field is opposite to the direction of electron movement, slowing down the electron migration rate, and at the same time is in the same direction as the hole movement, accelerating hole injection; the step barrier formed by the InGaN with variable In composition is conducive to binding electrons and has a blocking effect on electrons, thereby improving the luminous efficiency of the LED.

[0052] Furthermore, a quantum well layer 5 and a protective layer 6 stacked in sequence along the first direction D are provided between two adjacent quantum barrier layers 4, the quantum well layer 5 is an InGaN layer, and the protective layer 6 is a GaN layer.

[0053] In a preferred embodiment, the P-type doping of the P-type doped InGaN layer is Mg, and the doping concentration of Mg is 1*10 18 cm -3 -5*10 18 cm -3 The N-type doping of the N-type doped I nGaN layer is Si, and the doping concentration of Si is 2*17cm -3 -9*17cm -3 .

[0054] In a preferred embodiment, along the first direction D, the thickness of the first N-1 quantum barrier layers 4 is less than the thickness of the last quantum barrier layer 4. Preferably, along the first direction D, the thickness of the first N-1 quantum barrier layers 4 ranges from 10 to 20 nm, including the end value; the thickness of the last quantum barrier layer 4 ranges from 20 to 40 nm, including the end value. The last quantum barrier layer 4 is set thicker to protect the quantum well layer 5.

[0055] In a preferred embodiment, if Figure 3 , 4 As shown, along the first direction D, the first N-1 quantum barrier layers 4 are AlGaN; the first N-1 quantum barrier layers 4 form a first layer group 9; the first layer group 9 includes A layers of quantum barrier layers 4 arranged continuously, A is a positive integer; each quantum barrier layer 4 of the first layer group 9 is provided with an insertion layer 10, and each insertion layer 10 is AlGaN; the Al component of each insertion layer 10 is greater than the Al component of its corresponding quantum barrier layer 4, and the Al component of each insertion layer 10 gradually increases along the first direction D. Preferably, the Al component of each insertion layer 10 can be gradually increased from 0.05 to 0.15, and the interval of the gradual change of the Al component is not limited in this application.

[0056] The first layer group 9 sets an insertion layer 10 with a high Al component in each quantum barrier layer 4, and the Al component of each insertion layer 10 gradually increases along the first direction D, which can enhance the electron binding ability. At the same time, the insertion layer 10 interface parasitic reverse charge forms a reverse electric field inside (such as Fig. 9 As shown), it is beneficial to hole transport; that is, a positive electric field is formed in the active layer 2 along the growth direction (ie, the first direction), which will hinder hole transport, and a reverse electric field is formed to weaken the forward electric field, so that the obstruction to holes is reduced.

[0057] Furthermore, the first sublayer 7 in the last quantum barrier layer 4 is combined with the insertion layer 10, which not only increases hole injection but also facilitates hole transport, allowing carriers to be more evenly distributed throughout the active layer 2, thereby improving the overall luminous efficiency of the device.

[0058] In a preferred embodiment, the thickness of the insertion layer 10 ranges from 1 nm to 3 nm, including the end values. The relatively thin thickness of the insertion layer 10 is conducive to holes entering the quantum well layer 5 through tunneling.

[0059] In a preferred embodiment, if Figure 1 , 3 4, the first N-1 quantum barrier layers 4 form a second layer group 11 located between the first layer group 9 and the N-type semiconductor layer 1; the second layer group 11 includes B layers of quantum barrier layers 4 arranged continuously, B is a positive integer; the Al component of the quantum barrier layers 4 of the second layer group 11 gradually decreases along the first direction D. Preferably, the Al component of the quantum barrier layers 4 of the second layer group 11 can be gradually reduced from 0.15 to 0.05, and the difference in the Al component of each quantum barrier layer 4 is not limited in this application.

[0060] The first N-1 quantum barrier layers 4 are in the second layer group 11 between the first layer group 9 and the N-type semiconductor layer 1, and the Al component of the quantum barrier layers 4 of the second layer group 11 gradually decreases along the first direction D; due to the higher conduction band barrier height of AlGaN, the electron migration rate is retarded, the electron binding ability is enhanced, and the Al component gradually decreases, which reduces the subsequent quantum well valence band barrier height and is beneficial to hole transmission.

[0061] In a preferred embodiment, the sum of A and B is equal to N−1. That is, the first N−1 quantum barrier layers 4 are composed of the first layer group 9 and the second layer group 11 .

[0062] In a preferred embodiment, along the first direction D, the second layer group 11 includes the first N-3 quantum barrier layers 4, and the first layer group 9 includes the N-2nd and N-1th quantum barrier layers 4. That is, the value of B is N-3, and the value of A is 2.

[0063] like Figure 5As shown, the N-type semiconductor layer 1 or the P-type semiconductor layer 3 of the LED epitaxial structure is stacked on one side surface of the substrate 12. The present application takes the N-type semiconductor layer 1 disposed on one side surface of the substrate 12 as an example for explanation. Preferably, the LED epitaxial structure also includes a low-temperature nucleation layer 13 located between the substrate 12 and the N-type semiconductor layer 1, and the low-temperature nucleation layer 13 can be a GaN layer. Further preferably, the LED epitaxial structure also includes an undoped GaN layer 14 located between the low-temperature nucleation layer 13 and the N-type semiconductor layer 1, and by growing a high-quality GaN layer, the lattice mismatch between the sapphire substrate 12 and the subsequent growth material is reduced. Further preferably, the LED epitaxial structure also includes an InGaN / GaN superlattice structure 15 located between the N-type semiconductor layer 1 and the active layer 2, and the growth difference of Ga on different polarity planes is used to form a V-shaped pit (Vp its). The LED epitaxial structure of the present application can be processed by etching to expose part of the N-type semiconductor layer 1, and the N electrode and the P electrode are made to form an LED chip, and can also be made into LED chips of other types of structures, such as a vertical structure, a flip-chip structure, etc.

[0064] For ease of understanding, an embodiment of the active layer 2 of the present application is described in detail by taking N as 7, A as 2, and B as 4 as an example:

[0065] like Figure 6 As shown, the active layer 2 includes 7 quantum barrier layers 4 stacked in sequence along a first direction D. A quantum well layer 5 ( Figure 5 Omitted and not shown) and protective layer 6 ( Figure 5 The quantum well layer 5 is an InGaN layer, and the protective layer 6 is a GaN layer. Figure 1 , 2 , 3, 4, and 6, along the first direction D, the last quantum barrier layer 4 (the seventh quantum barrier layer) includes a first sublayer 7 and a second sublayer 8; the first sublayer 7 includes an N-type doped InGaN layer 71, an undoped InGaN layer 72, and a P-type doped InGaN layer 73 sequentially grown along the first direction D, and the In component of the first sublayer 7 gradually decreases along the first direction; the second sublayer 8 is a GaN layer. The quantum well layer 5 is an InGaN layer, and the protective layer 6 is a GaN layer.

[0066] The P-type doping of the P-type doped InGaN layer 73 in the first sublayer 7 is Mg, and the doping concentration of Mg is 1*10 18 cm -3 -5*10 18 cm -3 The N-type doping of the N-type doped I nGaN layer 71 is Si, and the doping concentration of Si is 2*17cm -3 -9*17cm -3The thickness of the first six quantum barrier layers 4 ranges from 10 to 20 nm, including the end values; the thickness of the last quantum barrier layer 4 ranges from 20 to 40 nm, including the end values.

[0067] Along the first direction D, the first six quantum barrier layers 4 are AlGaN, and the first six quantum barrier layers 4 form a first layer group 9 and a second layer group 11 . The second layer group 11 is located between the N-type semiconductor layer 1 and the first layer group 9 .

[0068] like Figure 6 As shown, the second layer group 11 includes 4 consecutively arranged quantum barrier layers 4, and the Al component of the quantum barrier layers 4 of the second layer group 11 gradually decreases along the first direction D; that is, the 1st, 2nd, 3rd, and 4th quantum barrier layers 4 constitute the second layer group 11, the Al component of the 1st quantum barrier layer 4 is greater than the Al component of the 2nd quantum barrier layer 4, the Al component of the 2nd quantum barrier layer 4 is greater than the Al component of the 3rd quantum barrier layer 4, and the Al component of the 3rd quantum barrier layer 4 is greater than the Al component of the 4th quantum barrier layer 4.

[0069] like Figure 4 , 6 As shown, the first layer group 9 includes two layers of quantum barrier layers 4 arranged continuously, and each quantum barrier layer 4 of the first layer group 9 is provided with an insertion layer 10, and each insertion layer 10 is AlGaN; the Al component of each insertion layer 10 is greater than the Al component of the corresponding quantum barrier layer 4, and the Al component of each insertion layer 10 gradually increases along the first direction D. That is, the 5th and 6th quantum barrier layers 4 constitute the first layer group 9, and the 5th quantum barrier layer 4 and the 6th quantum barrier layer 4 are provided with insertion layers 10. The Al component of the insertion layer 10 in the 5th quantum barrier layer 4 is greater than the Al component of the 5th quantum barrier layer 4, and the Al component of the insertion layer 10 in the 5th quantum barrier layer 4 gradually increases along the first direction D. The Al component of the insertion layer 10 in the 6th quantum barrier layer 4 is greater than the Al component of the 6th quantum barrier layer 4, and the Al component of the insertion layer 10 in the 6th quantum barrier layer 4 gradually increases along the first direction D. The thickness of each insertion layer 10 ranges from 1nm to 3nm, including the end value.

[0070] like Figure 7 The energy band diagram of the active layer 2 when N is 7 is shown. From left to right in the figure, the part selected by the first dotted box is the energy band diagram of the active layer including the first layer group area, and the part selected by the second dotted box is the energy band diagram of the area including the last quantum barrier layer.

[0071] The present application also provides a method for manufacturing an LED epitaxial structure, such as Figure 1As shown, it includes sequentially manufacturing an N-type semiconductor layer 1, an active layer 2 and a P-type semiconductor layer 3 along a first direction D; the first direction D is perpendicular to the N-type semiconductor layer 1 and points from the N-type semiconductor layer 1 to the active layer 2; the active layer 2 includes N quantum barrier layers 4 sequentially grown along the first direction D, where N is a positive integer; along the first direction D, the last quantum barrier layer 4 includes a first sublayer 7 and a second sublayer 8; the first sublayer 7 includes an N-type doped InGaN layer 71, an undoped InGaN layer 72 and a P-type doped InGaN layer 73 sequentially stacked along the first direction D, and the In component gradually decreases along the first direction D, and the second sublayer 8 is a GaN layer.

[0072] Furthermore, a quantum well layer 5 and a protective layer 6 sequentially grown along the first direction D are provided between two adjacent quantum barrier layers 4, the quantum well layer 5 is an InGaN layer, and the protective layer 6 is a GaN layer.

[0073] In a preferred embodiment, the P-type doping of the P-type doped InGaN layer 73 is Mg, and the doping concentration of Mg is 1*10 18 cm -3 -5*10 18 cm -3 The N-type doping of the N-type doped I nGaN layer 71 is Si, and the doping concentration of Si is 2*17cm -3 -9*17cm -3 .

[0074] In a preferred embodiment, along the first direction D, the thickness of the first N-1 quantum barrier layers 4 is less than the thickness of the last quantum barrier layer 4. Preferably, along the first direction D, the thickness of the first N-1 quantum barrier layers 4 ranges from 10 to 20 nm, including the end value; the thickness of the last quantum barrier layer 4 ranges from 20 to 40 nm, including the end value.

[0075] In a preferred embodiment, if Figure 3 , 4 As shown, along the first direction D, the first N-1 quantum barrier layers 4 are Al GaN; the first N-1 quantum barrier layers 4 form a first layer group 9; the first layer group 9 includes A layers of quantum barrier layers 4 arranged continuously, A is a positive integer; each quantum barrier layer 4 of the first layer group 9 is provided with an insertion layer 10, and each insertion layer 10 is Al GaN; the Al component of each insertion layer 10 is greater than the Al component of its corresponding quantum barrier layer 4; the Al component of each insertion layer 10 gradually increases along the first direction D.

[0076] In a preferred embodiment, the thickness of the insertion layer 10 ranges from 1 nm to 3 nm, including the end points.

[0077] In a preferred embodiment, if Figure 3As shown, the first N-1 quantum barrier layers 4 form a second layer group 11 located between the first layer group 9 and the N-type semiconductor layer 1; the second layer group 11 includes B layers of quantum barrier layers 4 arranged continuously, B is a positive integer; the Al component of the quantum barrier layers 4 of the second layer group 11 gradually decreases along the first direction D.

[0078] In a preferred embodiment, the sum of A and B is equal to N-1.

[0079] In a preferred embodiment, along the first direction D, the second layer group 11 includes the first N-3 quantum barrier layers 4 , and the first layer group 9 includes the N-2 th and the N-1 th quantum barrier layers 4 .

[0080] In actual production, Figure 4 As shown, the N-type semiconductor layer 1 or the P-type semiconductor layer 3 is grown on the surface of one side of the substrate 12. The present application takes the growth of the N-type semiconductor layer 1 on the surface of one side of the substrate 12 as an example for explanation. Preferably, before growing the N-type semiconductor layer 1 on the substrate 12, it also includes growing a low-temperature nucleation layer 13 on the substrate 12, and the low-temperature nucleation layer 13 can be a GaN layer. Further preferably, after growing the low-temperature nucleation layer 13 and before growing the N-type semiconductor layer 1, it also includes growing an undoped GaN layer 14 on the low-temperature nucleation layer 13, and by growing a high-quality GaN layer, the lattice mismatch between the sapphire substrate 12 and the subsequent growth material is reduced. Further preferably, the LED epitaxial structure also includes growing an InGaN / GaN superlattice structure 15 on the N-type semiconductor layer 1 after growing the N-type semiconductor layer 1 and before growing the active layer 2.

[0081] For ease of understanding, the following is a more detailed description of the method for making an LED epitaxial structure:

[0082] The equipment used is MOCVD, with trimethyl / ethylgallium TMGa / TEGa, trimethylaluminum TMA l, ammonia NH3 as Ga source, Al source, N source, N2 as carrier gas, N-type and P-type doping sources are silane SiH4 and bis(cyclopentadienyl)magnesium CP2Mg respectively. The pressure during the entire production process is 80torr-400torr.

[0083] S01: Provide a substrate 12, place the substrate 12 in a MOCVD reaction chamber, and introduce high-purity hydrogen at 1100° C. for 3 min-13 min.

[0084] S02: Cool down to 750℃-950℃ and introduce TEGa source and N source to grow 10-30nm thick undoped GaN low temperature nucleation layer 13

[0085] S03: Raise the temperature to 950° C.-1200° C., turn off the TEGa source, introduce the TMGa source, and grow a 1.5um-3um undoped GaN layer 14.

[0086] S04: Introduce silane to grow 1um-3um thick N-GaN.

[0087] S05: cooling to 750° C.-900° C., introducing In source and Ga source, and alternately growing 4-12 periods of InGaN / GaN superlattice structure 15 .

[0088] S06: Growth of active layer 2: Lower the temperature to 750-950°C, grow a 7-25nm thick quantum barrier layer 4; lower the temperature to 650-850°C, continue to introduce TEGa and TMI n, while turning off SiH4 and H2, grow a 1-6nm thick quantum well layer 5; continue to introduce TEGa source, grow a 10A-20A GaN protective layer 6; finally turn on H2 and raise the temperature to the growth temperature of the quantum barrier layer 4. Repeat the above growth process for multiple cycles, and then grow the last quantum barrier layer 4 to complete the growth process of the active layer 2.

[0089] The quantum barrier layer 4 of the entire active layer 2 has N layers. In the process of growing each quantum barrier layer 4, the Al component of the first N-3 quantum barrier layers 4 is gradually reduced along the first direction D. In order to achieve the Al gradual growth of the first N-3 quantum barrier layers, on the one hand, the Al component of different quantum barrier layers can be controlled by adjusting the content of Al introduced, and on the other hand, the amount of NH3 introduced when growing different quantum barriers can be used to affect the incorporation of Al, thereby achieving different Al contents in different quantum barrier layers; an Al GaN insertion layer 10 is formed in the first N-2 and N-1 quantum barrier layers 4, with a thickness of 1nm-3nm (including end values); the last quantum barrier layer is thicker, with a thickness ranging from 20nm to 40nm, and includes a first sublayer 7 and a second sublayer 8 grown in sequence along the first direction D, the first sublayer 7 includes an N-type doped I nGaN layer 71, an undoped I nGaN layer 72 and a P-type doped I nGaN layer 73 stacked in sequence along the first direction D; the second sublayer 8 is a GaN layer, and the I nGaN layer of the first sublayer 7 is 10. The n component gradually decreases along the first direction D. The P-type doping of the P-type doped I nGaN layer 73 is Mg, and the doping concentration of Mg is 1*10 18 cm -3 -5*10 18 cm -3 The N-type doping of the N-type doped InGaN layer 71 is Si, and the doping concentration of Si is 2*17cm -3 -9*17cm -3 .

[0090] S07: Grow a layer of P-GaN with a P-type doping concentration of 5x10 18 cm -3 -10x10 18 cm -3, anneal at 800℃-950℃ for 15-35 minutes in N2 atmosphere.

[0091] The method for manufacturing the LED epitaxial structure of the present application has the same beneficial effects as the above-mentioned LED epitaxial structure, which will not be described in detail here.

[0092] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "horizontal", "vertical", "upper", "lower", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0093] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0094] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An LED epitaxial structure, characterized in that: It includes an N-type semiconductor layer, an active layer and a P-type semiconductor layer which are sequentially stacked along a first direction; the first direction is perpendicular to the N-type semiconductor layer and points from the N-type semiconductor layer to the active layer; The active layer includes N quantum barrier layers stacked in sequence along a first direction, where N is a positive integer; Along the first direction, the last quantum barrier layer includes a first sublayer and a second sublayer; the first sublayer includes an N-type doped InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer stacked in sequence along the first direction, and the In component of the first sublayer gradually decreases along the first direction; the second sublayer is a GaN layer.

2. An LED epitaxial structure as claimed in claim 1, characterized in that: A quantum well layer and a protective layer stacked in sequence along a first direction are provided between two adjacent quantum barrier layers, wherein the quantum well layer is an InGaN layer and the protective layer is a GaN layer.

3. The LED epitaxial structure according to claim 1, characterized in that: The P-type doping of the P-type doped InGaN layer is Mg, and the doping concentration of Mg is 1*10 18 cm -3 -5*10 18 cm -3 The N-type doping of the N-type doped InGaN layer is Si, and the doping concentration of Si is 2*17cm -3 -9*17cm -3 .

4. The LED epitaxial structure according to claim 1, characterized in that: Along the first direction, the thickness of the first N-1 quantum barrier layers is less than the thickness of the last quantum barrier layer.

5. The LED epitaxial structure according to claim 1, characterized in that: Along the first direction, the first N-1 quantum barrier layers are AlGaN; the first N-1 quantum barrier layers form a first layer group; the first layer group includes A layers of continuously arranged quantum barrier layers, A is a positive integer; each quantum barrier layer of the first layer group is provided with an insertion layer, and each insertion layer is AlGaN; the Al component of each insertion layer is greater than the Al component of its corresponding quantum barrier layer; the Al component of each insertion layer gradually increases along the first direction.

6. The LED epitaxial structure according to claim 5, characterized in that: The first N-1 quantum barrier layers form a second layer group located between the first layer group and the N-type semiconductor layer; the second layer group includes B continuously arranged quantum barrier layers, B is a positive integer; the Al component of the quantum barrier layers of the second layer group gradually decreases along the first direction.

7. The LED epitaxial structure according to claim 6, characterized in that: The sum of A and B is equal to N-1.

8. The LED epitaxial structure according to claim 6, characterized in that: Along the first direction, the second layer group includes the first N-3 quantum barrier layers, and the first layer group includes the N-2 th and the N-1 th quantum barrier layers.

9. The LED epitaxial structure according to claim 5, characterized in that: The thickness of the insertion layer ranges from 1 nm to 3 nm, including the end points.

10. A method for manufacturing an LED epitaxial structure, characterized in that: An N-type semiconductor layer, an active layer and a P-type semiconductor layer are sequentially fabricated along a first direction; the first direction is perpendicular to the N-type semiconductor layer and points from the N-type semiconductor layer to the active layer; The active layer includes N quantum barrier layers sequentially grown along the first direction, where N is a positive integer; Along the first direction, the last quantum barrier layer includes a first sublayer and a second sublayer; the first sublayer includes an N-type doped InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer grown in sequence along the first direction, and the In component of the first sublayer gradually decreases along the first direction; the second sublayer is a GaN layer.

11. The method for manufacturing an LED epitaxial structure according to claim 10, characterized in that: A quantum well layer and a protective layer grown sequentially along the first direction are provided between two adjacent quantum barrier layers. The quantum well layer is an InGaN layer, and the protective layer is a GaN layer.

12. The method for manufacturing an LED epitaxial structure according to claim 10, characterized in that: Along the first direction, the first N-1 quantum barrier layers are AlGaN; the first N-1 quantum barrier layers form a first layer group; the first layer group includes A layers of continuously arranged quantum barrier layers, A is a positive integer; each quantum barrier layer of the first layer group is provided with an insertion layer, and each insertion layer is AlGaN; the Al component of each insertion layer is greater than the Al component of its corresponding quantum barrier layer; the Al component of each insertion layer gradually increases along the first direction.

13. The method for manufacturing an LED epitaxial structure according to claim 12, characterized in that: The first N-1 quantum barrier layers form a second layer group located between the first layer group and the N-type semiconductor layer; the second layer group includes B layers of quantum barrier layers continuously arranged, B is a positive integer; the Al component of the quantum barrier layers of the second layer group gradually decreases along the first direction.

14. The method for manufacturing an LED epitaxial structure according to claim 13, wherein the sum of A and B is equal to N-1.

15. The method for manufacturing an LED epitaxial structure according to claim 13, characterized in that: Along the first direction, the second layer group includes the first N-3 quantum barrier layers, and the first layer group includes the N-2 th and the N-1 th quantum barrier layers.

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