LED epitaxial structure and manufacturing method thereof

Abstract

An LED epitaxial structure and a manufacturing method thereof, wherein the LED epitaxial structure comprises 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 comprises N quantum barrier layers which are sequentially stacked along the first direction, N being a positive integer; along 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 InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer which are sequentially stacked along the first direction and the In component of the first sub-layer gradually decreases along the first direction, and the second sub-layer is a GaN layer. The LED epitaxial structure can weaken the polarization electric field of the active layer, reduce the adverse effects of QCSE, accelerate hole injection, be beneficial to bound electrons and improve the light-emitting efficiency of the LED due to the above arrangement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of light emitting diode, more particularly to a LED epitaxial structure and a manufacturing method thereof. BACKGROUND

[0002] At present, Al InGaN-based light emitting materials play more and more applications in display and lighting fields due to their physical and chemical properties such as wide band gap, 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 long-wave bands such as green light, yellow light and red light, as the In content in the active layer InGaN becomes higher, the crystal quality becomes worse and the defects increase, thereby reducing the light emitting efficiency of LED. In addition, the lattice mismatch and low miscibility between InN and GaN easily cause In clusters in the InGaN / GaN active layer, thereby causing phenomena such as non-concentrated light emission and impure color rendering. In addition, due to the spontaneous polarization and piezoelectric polarization of III-nitride, an internal electric field is formed, which easily causes quantum confinement Stark effect, aggravates electron leakage, and causes electron to easily leak into the P-type semiconductor layer from the active layer due to small electron effective mass and large electron mobility. In addition, the large hole effective mass and low hole mobility result in that in the traditional LED structure, holes are mainly distributed in a few quantum wells close to the P-type semiconductor layer side; these reasons will make the carrier distribution in the active layer uneven, reduce the radiation recombination, and thus affect the light emitting efficiency of LED.

[0003] In order to solve this problem, it is common at present to insert an Al GaN electron blocking layer (EBL) between the InGaN / GaN active layer and the P-type semiconductor layer, increase the conduction band electron barrier, and reduce electron leakage, but 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, and thus affecting the light emitting efficiency of LED.

[0004] Therefore, reducing electron leakage and increasing hole injection efficiency have become urgent problems to be solved for improving the light emitting efficiency of LED. SUMMARY

[0005] Therefore, the present application provides a LED epitaxial structure and a manufacturing method thereof capable of improving the light emitting efficiency of LED.

[0006] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0007] An LED epitaxial structure, comprising 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;

[0008] The active layer comprises N quantum barrier layers which are sequentially stacked along the first direction, N being a positive integer;

[0009] Along 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 InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer which are sequentially stacked along the first direction, and the In component of the first sub-layer gradually decreases along the first direction, and the second sub-layer is a GaN layer.

[0010] Further, a quantum well layer and a protection layer are arranged between two adjacent quantum barrier layers along the first direction; the quantum well layer is an InGaN layer, and the protection layer is a GaN layer.

[0011] Further, 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 .

[0012] Further, 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] Further, 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 comprises A quantum barrier layers which are sequentially arranged, A being a positive integer; each of the quantum barrier layers of the first layer group is provided with an insertion layer, and each of the insertion layers is AlGaN; the Al component of each of the insertion layers is greater than the Al component of the corresponding quantum barrier layer; and the Al component of each of the insertion layers gradually increases along the first direction.

[0014] Further, the first N-1 quantum barrier layers form a second layer group between the first layer group and the N-type semiconductor layer; the second layer group comprises B quantum barrier layers which are sequentially arranged, B being a positive integer; and the Al component of the quantum barrier layers of the second layer group gradually decreases along the first direction.

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

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

[0017] Further, the thickness of the insertion layer ranges from 1nm to 3nm, inclusive.

[0018] The application further provides a method for manufacturing an LED epitaxial structure, which comprises sequentially manufacturing an N-type semiconductor layer, an active layer and a P-type semiconductor layer 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 comprises N quantum barrier layers sequentially grown along the first direction, wherein N is a positive integer.

[0020] Along 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 InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer sequentially grown along the first direction, and the In component of the first sub-layer gradually decreases along the first direction; and the second sub-layer is a GaN layer.

[0021] Further, a quantum well layer and a protection layer are arranged between two adjacent quantum barrier layers along the first direction; the quantum well layer is an InGaN layer, and the protection layer is a GaN layer.

[0022] Further, 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 comprises A quantum barrier layers sequentially arranged, wherein A is a positive integer; each quantum barrier layer of the first layer group is provided with an insertion layer, each insertion layer is AlGaN; the Al component of each insertion layer is greater than the Al component of the corresponding quantum barrier layer; and the Al component of each insertion layer gradually increases along the first direction.

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

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

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

[0026] Compared with the prior art, the technical scheme provided by the application 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 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 comprises N quantum barrier layers which are sequentially stacked 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 which are sequentially grown 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 structure, the last quantum barrier layer comprises the first sublayer and the second sublayer, and the first sublayer comprises an InGaN with a variable In component and a N-i-P structure (i.e. an N-type doped-undoped-P-type doped structure), an internal electric field is formed in the i layer, and the direction of the electric field is opposite to the growth direction; on the one hand, the polarization electric field in the active layer can be weakened, and the adverse effects of QCSE can be reduced; on the other hand, the internal electric field is opposite to the direction of electron movement, so that the electron migration rate is slowed down, and the direction of hole movement is the same, so that the hole injection is accelerated; the step barrier formed by the InGaN with a variable In component is beneficial to binding electrons, and has a blocking effect on electrons; and thus the light emitting efficiency of the LED is improved.

[0028] 2. The first layer group is provided with 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, so that the electron binding ability can be enhanced. At the same time, the insertion layer interface has parasitic reverse charges, and an internal reverse electric field is formed, which is beneficial 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 hinders the hole transmission, and the formation of the reverse electric field weakens the positive electric field, so that the hindrance to the hole is reduced.

[0029] In addition, the first sublayer in the last quantum barrier layer is combined with the insertion layer, which not only increases the hole injection, but also is beneficial to the hole transmission, so that the distribution of the carriers in the entire active layer is more uniform, and the overall light emitting efficiency of the device is improved.

[0030] 3. The first N-1 quantum barrier layers are provided between the first layer group and the second layer group between 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 high conduction band barrier height of AlGaN, the electron migration rate is retarded, the electron binding ability is enhanced, the Al component gradually decreases, the subsequent quantum well valence band barrier height is reduced, and the hole transmission is facilitated.

[0031] 4. The thickness of the insertion layer is in the range of 1 nm to 3 nm, and the thinner thickness is beneficial for the holes to tunnel into the quantum well layer. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the provided drawings.

[0033] Figure 1 FIG. 1 is a structural schematic diagram of an embodiment of the LED epitaxial structure in the present application;

[0034] Figure 2 FIG. 2 is a structural schematic diagram of the first sub-layer in the present application;

[0035] Figure 3 FIG. 3 is a structural schematic diagram of the active layer from the first quantum barrier layer to the N-1th quantum barrier layer in the present application;

[0036] Figure 4 FIG. 4 is a structural schematic diagram of the first layer group in the present application;

[0037] Figure 5 FIG. 5 is a structural schematic diagram of another embodiment of the LED epitaxial structure in the present application;

[0038] Figure 6 FIG. 6 is a structural schematic diagram of the active layer when N is 7 in the present application;

[0039] Figure 7 FIG. 7 is a band diagram of the active layer when N is 7 in the present application;

[0040] Figure 8 FIG. 8 is a schematic diagram of the electric field formed inside the first sub-layer in the present application;

[0041] Figure 9 FIG. 9 is a schematic diagram of the electric field formed inside the first layer group in the present application.

[0042] LIST OF 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 sub-layer 7; N-type doped InGaN layer 71; undoped InGaN layer 72; P-type doped InGaN layer; second sub-layer 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] In order to make the content of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0045] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those of ordinary skill in the art can make similar generalizations without departing from the connotation of the present application, therefore the present application is not limited by the specific embodiments disclosed below.

[0046] Secondly, the present application is described in detail in combination with the schematic diagram, and in the detailed description of the embodiments of the present application, the cross-sectional view of the device structure will be partially enlarged without general proportion for the convenience of description, and the schematic diagram is only an example, which should not limit the scope of protection of the present application herein. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in actual manufacture.

[0047] The present application provides an LED epitaxial structure, as shown in the figure, which comprises an N-type semiconductor layer 1, an active layer 2 and a P-type semiconductor layer 3 which are sequentially stacked 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 can be N-GaN, and the P-type semiconductor layer 3 can be P-GaN. Figure 1 The active layer 2 comprises N quantum barrier layers 4 which are sequentially stacked along the first direction D, and N is a positive integer. Along the first direction D, the last quantum barrier layer 4 comprises a first sublayer 7 and a second sublayer 8; as shown in the figure, the first sublayer 7 comprises an N-type doped InGaN layer 71, an undoped InGaN layer 72 and a P-type doped InGaN layer 73 which are sequentially stacked along the first direction D, and the In composition of the first sublayer gradually decreases along the first direction D; the second sublayer 8 is a GaN layer. Wherein, the first sublayer 7 and the second sublayer 8 are sequentially stacked along the first direction D.

[0048] Figure 2 Preferably, the value of N can be in the range of 1 < N ≤ 15.

[0049] Preferably, the value of the In composition Z of the first sublayer is in the range of 0 < Z < 0.4, that is, the In composition of the first sublayer can gradually decrease along the first direction D within this range. The composition content mentioned in the present application is the molar ratio.

[0050] Preferably, the value of the In composition Z of the first sublayer is in the range of 0 < Z < 0.4, that is, the In composition of the first sublayer can gradually decrease along the first direction D within this range. The composition content mentioned in the present application is the molar ratio.

[0051] ​The LED epitaxial structure of the present application, due to the above structure, the last quantum barrier layer comprises a first sub-layer and a second sub-layer, and the first sub-layer comprises InGaN with variable In composition and N-i-P structure (i.e. N-type doped-undoped-P-type doped structure), an internal electric field is formed in the i layer, and the direction of the electric field is the opposite direction of the growth direction (as shown in Figure 8 On one hand, the internal electric field is opposite to the direction of electron movement, which slows down the electron migration rate, while the internal electric field is the same as the direction of hole movement, which accelerates the hole injection; on the other hand, the step potential barrier formed by the InGaN with variable In composition is beneficial to the confinement of electrons, which plays a blocking effect on the electrons, thereby improving the light emitting efficiency of the LED.

[0052] Further, each of two adjacent quantum barrier layers 4 is provided with a quantum well layer 5 and a protection layer 6 which are sequentially stacked along the first direction D, the quantum well layer 5 is an InGaN layer, and the protection 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 -9*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 10nm to 20nm, inclusive; and the thickness of the last quantum barrier layer 4 ranges from 20nm to 40nm, inclusive. The thickness of the last quantum barrier layer 4 is set to be relatively thick to protect the quantum well layer 5.

[0055] In a preferred embodiment, as shown in Figure 3 , 4 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 comprises A quantum barrier layers 4 which are sequentially arranged, A is a positive integer; each of the quantum barrier layers 4 of the first layer group 9 is provided with an insertion layer 10, and each of the insertion layers 10 is AlGaN; the Al composition of each of the insertion layers 10 is greater than the Al composition of the corresponding quantum barrier layer 4, and the Al composition of each of the insertion layers 10 gradually increases along the first direction D. Preferably, the Al composition of each of the insertion layers 10 gradually increases from 0.05 to 0.15, and the interval of the gradual change of the Al composition is not limited in the present application.

[0056] The first layer group 9 sets the insertion layer 10 with 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 an internal reverse electric field (as shown in Figure 9 The insertion layer 10 is beneficial to the hole transport; that is, the positive electric field formed in the active layer 2 along the growth direction (i.e., the first direction) hinders the hole transport, and the formation of the reverse electric field weakens the positive electric field, so that the hindrance to the hole is reduced.

[0057] In addition, the first sublayer 7 in the last quantum barrier layer 4 combines the insertion layer 10, which not only increases the hole injection but also is beneficial to the hole transport, so that the distribution of the carriers in the entire active layer 2 is more uniform, and the overall light-emitting efficiency of the device is improved.

[0058] In a preferred embodiment, the thickness of the insertion layer 10 is in the range of 1 nm-3 nm, including the end point value. The insertion layer 10 is relatively thin, which is beneficial to the hole to pass through the tunneling into the quantum well layer 5.

[0059] In a preferred embodiment, as shown in Figure 1 , 3 , 4, the first N-1 quantum barrier layers 4 form a second layer group 11 between the first layer group 9 and the N-type semiconductor layer 1; the second layer group 11 includes quantum barrier layers 4 arranged continuously in the B layer, and 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 gradually decrease from 0.15 to 0.05, and the difference of the Al component of each quantum barrier layer 4 is not limited in the present application.

[0060] The first N-1 quantum barrier layers 4 form 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 high conduction band barrier height of AlGaN, the electron migration rate is delayed, the electron binding ability is enhanced, the Al component gradually decreases, the subsequent quantum well valence band barrier height is reduced, and the hole transport is facilitated.

[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-2 and N-1 quantum barrier layers 4. That is, the value of B is N-3, and the value of A is 2.

[0063] As shown in Figure 5As shown, the N-type semiconductor layer 1 or the P-type semiconductor layer 3 of the LED epitaxial structure is laminated on one side surface of the substrate 12, and the present application takes the N-type semiconductor layer 1 arranged on one side surface of the substrate 12 as an example for description. Preferably, the LED epitaxial structure further comprises a low-temperature nucleation layer 13 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 further comprises an undoped GaN layer 14 between the low-temperature nucleation layer 13 and the N-type semiconductor layer 1, and the high-quality GaN layer is grown to reduce the lattice mismatch between the sapphire substrate 12 and the subsequent growth material. Further preferably, the LED epitaxial structure further comprises an InGaN / GaN superlattice structure 15 between the N-type semiconductor layer 1 and the active layer 2, and the V-pits are formed by using the growth difference of Ga on different polar planes. The LED epitaxial structure of the present application can be processed by etching to expose part of the N-type semiconductor layer 1, and an N electrode and a P electrode are made to form an LED chip, or it can be made into an LED chip of other types of structures, such as a vertical structure, a flip structure, etc.

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

[0065] As shown in Figure 6 , the active layer 2 comprises 7 quantum barrier layers 4 laminated in sequence along the first direction D. Between two adjacent quantum barrier layers 4, there are quantum well layers 5 (not shown in Figure 5 ) and protective layers 6 (not shown in Figure 5 ) laminated in sequence along the first direction D, the quantum well layers 5 are InGaN layers, and the protective layers 6 are GaN layers. As shown in Figure 1 , 2 , 3, 4, and 6, along the first direction D, the last quantum barrier layer 4 (the 7th quantum barrier layer) comprises a first sublayer 7 and a second sublayer 8; the first sublayer 7 comprises an N-type doped InGaN layer 71, an undoped InGaN layer 72, and a P-type doped InGaN layer 73 grown in sequence along the first direction D, and the In content of the first sublayer 7 gradually decreases along the first direction; and the second sublayer 8 is a GaN layer. The quantum well layers 5 are InGaN layers, and the protective layers 6 are GaN layers.

[0066] Among them, 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 InGaN layer 71 is Si, and the doping concentration of Si is 2*17cm -3 -9*17cm -3The thickness of the first 6 quantum barrier layers 4 ranges from 10nm to 20nm, inclusive of the end values; and the thickness of the last quantum barrier layer 4 ranges from 20nm to 40nm, inclusive of the end values.

[0067] In the first direction D, the first 6 quantum barrier layers 4 are AlGaN, and the first 6 quantum barrier layers 4 are formed with a first layer group 9 and a second layer group 11, and the second layer group 11 is located between the N-type semiconductor layer 1 and the first layer group 9.

[0068] As shown in Figure 6 , the second layer group 11 includes 4 quantum barrier layers 4 arranged in sequence, and the Al composition of the quantum barrier layers 4 of the second layer group 11 gradually decreases along the first direction D; that is, the first, second, third and fourth quantum barrier layers 4 form the second layer group 11, the Al composition of the first quantum barrier layer 4 is greater than that of the second quantum barrier layer 4, the Al composition of the second quantum barrier layer 4 is greater than that of the third quantum barrier layer 4, and the Al composition of the third quantum barrier layer 4 is greater than that of the fourth quantum barrier layer 4.

[0069] As shown in Figure 4 , 6 , the first layer group 9 includes 2 quantum barrier layers 4 arranged in sequence, and each quantum barrier layer 4 of the first layer group 9 is provided with an interlayer 10, and each interlayer 10 is AlGaN; the Al composition of each interlayer 10 is greater than that of the corresponding quantum barrier layer 4, and the Al composition of each interlayer 10 gradually increases along the first direction D. That is, the fifth and sixth quantum barrier layers 4 form the first layer group 9, and the fifth and sixth quantum barrier layers 4 are provided with interlayers 10. The Al composition of the interlayer 10 in the fifth quantum barrier layer 4 is greater than that of the fifth quantum barrier layer 4, and the Al composition of the interlayer 10 in the fifth quantum barrier layer 4 gradually increases along the first direction D. The Al composition of the interlayer 10 in the sixth quantum barrier layer 4 is greater than that of the sixth quantum barrier layer 4, and the Al composition of the interlayer 10 in the sixth quantum barrier layer 4 gradually increases along the first direction D. The thickness of each interlayer 10 ranges from 1nm to 3nm, inclusive of the end values.

[0070] As shown in Figure 7 , the energy band diagram of the active layer 2 when N is 7 is shown, and from left to right in the figure, the first dashed box selected part is the energy band diagram of the active layer containing the first layer group region, and the second dashed box selected part is the energy band diagram containing the last quantum barrier layer region.

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

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

[0073] In a preferred embodiment, P-type doping of 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 ; N-type doping of N-type doped InGaN layer 71 is Si, and the doping concentration of Si is 2*17cm -3 -9*17cm -3 .

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

[0075] In a preferred embodiment, as shown in Figure 3 , 4 , along 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 comprises A quantum barrier layers 4 arranged continuously, A being a positive integer; each quantum barrier layer 4 of the first layer group 9 is provided with an insertion layer 10, each insertion layer 10 being AlGaN; the Al composition of each insertion layer 10 is greater than the Al composition of the corresponding quantum barrier layer 4; the Al composition of each insertion layer 10 gradually increases along first direction D.

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

[0077] In a preferred embodiment, as shown in Figure 3As shown, the first N-1 quantum barrier layers 4 form a second layer group 11 between the first layer group 9 and the N-type semiconductor layer 1; the second layer group 11 includes B quantum barrier layers 4 arranged in series, B being a positive integer; the Al composition 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-2th and N-1th quantum barrier layers 4.

[0080] In actual production, as shown in the following process: Figure 4 As shown, the N-type semiconductor layer 1 or the P-type semiconductor layer 3 is grown on one side of the substrate 12, and the present application takes the N-type semiconductor layer 1 grown on one side of the substrate 12 as an example for description. Preferably, before growing the N-type semiconductor layer 1 on the substrate 12, a low-temperature nucleation layer 13 is first grown 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, an undoped GaN layer 14 is grown on the low-temperature nucleation layer 13, thereby reducing the lattice mismatch between the sapphire substrate 12 and the subsequently grown material by growing a high-quality GaN layer. Further preferably, the LED epitaxial structure further 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 describes the method for manufacturing the LED epitaxial structure in more detail:

[0082] The equipment used is MOCVD, and TMGa / TEGa, TMAI, and NH3 are used as Ga source, Al source, and N source, N2 is used as carrier gas, and SiH4 and CP2Mg are used as N-type and P-type doping sources. The pressure during the entire manufacturing process is 80-400 torr.

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

[0084] S02: Reduce the temperature to 750-950°C, pass the TEGa source and the N source to grow a 10-30 nm thick undoped GaN low-temperature nucleation layer 13.

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

[0086] S04: pass in silane, grow 1-3um thick N-GaN.

[0087] S05: cool down to 750-900℃, pass in In source and Ga source, alternately grow 4-12 periods of InGaN / GaN superlattice structure 15.

[0088] S06: grow active layer 2: reduce temperature to 750-950℃, grow 7-25nm thick quantum barrier layer 4; cool down to 650-850℃, continue to pass in TEGa, TMI n, at the same time, close SiH4 and H2, grow 1-6nm thick quantum well layer 5; continue to pass in TEGa source, grow 10A-20A of GaN protective layer 6; finally, open H2, and warm up to the growth temperature of quantum barrier layer 4. Repeat the above growth process for multiple periods, and regrow the last quantum barrier layer 4 to complete the growth process of active layer 2.

[0089] Among them, the quantum barrier layer 4 of the whole active layer 2 has N layers, and the Al composition of the first N-3 quantum barrier layers 4 gradually decreases along the first direction D. In order to realize the gradual growth of Al of the first N-3 quantum barrier layers, on the one hand, the Al composition of different quantum barrier layers can be controlled by adjusting the amount of Al passed in, and on the other hand, the amount of NH3 passed in during the growth of different quantum barrier layers can be used to affect the incorporation of Al, thereby realizing different Al contents of different quantum barrier layers; an AlGaN interlayer 10 is formed in the first N-2 and N-1 quantum barrier layers 4, with a thickness of 1-3nm (including the end point value); the last quantum barrier layer is thicker, with a thickness ranging from 20-40nm, and includes a first sublayer 7 and a second sublayer 8 grown along the first direction D in turn; the first sublayer 7 includes N-type doped InGaN layer 71, undoped InGaN layer 72 and P-type doped InGaN layer 73 stacked along the first direction D in turn; the second sublayer 8 is a GaN layer; the In composition of the first sublayer 7 gradually decreases along the first direction D. 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 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 -3800-950°C for 15-35 minutes under N2atmosphere.

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

[0092] Those skilled in the art should understand that, in the disclosure of the present application, the orientation or positional relationship indicated by the terms "lateral", "longitudinal", "upper", "lower" and the like is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above-mentioned terms cannot be understood as a limitation on the present application.

[0093] It should be noted that each of the embodiments in the present specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other.

[0094] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An LED epitaxial structure, characterized in that, The active layer comprises N quantum barrier layers which are sequentially stacked along the first direction, N being a positive integer. The last quantum barrier layer along the first direction comprises a first sub-layer and a second sub-layer; the first sub-layer comprises an N-type doped InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer which are sequentially stacked along the first direction, and the In component of the first sub-layer gradually decreases along the first direction; the second sub-layer is a GaN layer. Quantum well layers and protection layers are sequentially stacked along the first direction between two adjacent quantum barrier layers; the quantum well layers are InGaN layers, and the protection layers are GaN layers.

2. An LED epitaxial structure as claimed in claim 1, wherein, The thickness of the first N-1 quantum barrier layers along the first direction is smaller than the thickness of the last quantum barrier layer.

3. An LED epitaxial structure as claimed in claim 1, wherein, 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. An LED epitaxial structure as claimed in claim 1, wherein, The first N-1 quantum barrier layers along the first direction are AlGaN; the first N-1 quantum barrier layers form a first layer group; the first layer group comprises A quantum barrier layers which are sequentially stacked, A being 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 the corresponding quantum barrier layer; and the Al component of each insertion layer gradually increases along the first direction.

5. An LED epitaxial structure as claimed in claim 1, wherein, The first N-1 quantum barrier layers form a second layer group between the first layer group and the N-type semiconductor layer; the second layer group comprises B quantum barrier layers which are sequentially stacked, B being a positive integer; and the Al component of the quantum barrier layers of the second layer group gradually decreases along the first direction.

6. An LED epitaxial structure as claimed in claim 5, wherein, The sum of A and B is equal to N-1.

7. An LED epitaxial structure as claimed in claim 6, wherein, The second layer group comprises the first N-3 quantum barrier layers along the first direction, and the first layer group comprises the N-2th and N-1th quantum barrier layers.

8. An LED epitaxial structure as claimed in claim 6, wherein, The thickness of the insertion layer ranges from 1 nm to 3 nm, inclusive.

9. An LED epitaxial structure as claimed in claim 5, wherein, The active layer comprises N quantum barrier layers which are sequentially grown along the first direction, N being a positive integer.

10. A method for fabricating an LED epitaxial structure, characterized in that, The last quantum barrier layer along the first direction comprises a first sub-layer and a second sub-layer; the first sub-layer comprises an N-type doped InGaN layer, an undoped InGaN layer and a P-type doped InGaN layer which are sequentially grown along the first direction, and the In component of the first sub-layer gradually decreases along the first direction; the second sub-layer is a GaN layer. Quantum well layers and protection layers are sequentially grown along the first direction between two adjacent quantum barrier layers; the quantum well layers are InGaN layers, and the protection layers are GaN layers. ​ 11. The method of claim 10, wherein the LED epitaxial structure is grown on a substrate, and the substrate is removed after the growth of the LED epitaxial structure. ​ 12. The method of claim 10, wherein the LED epitaxial structure is grown on a substrate. In 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 comprises A layers of quantum barrier layers arranged in succession, A being a positive integer; each of the quantum barrier layers of the first layer group is provided with an interposed layer, each of the interposed layers being AlGaN; the Al composition of each of the interposed layers is greater than the Al composition of the corresponding quantum barrier layer; the Al composition of each of the interposed layers gradually increases in the first direction.

13. The method of claim 12, wherein the LED epitaxial structure is grown on a substrate, and the substrate is removed after the growth of the LED epitaxial structure. The first N-1 quantum barrier layers form a second layer group between the first layer group and the N-type semiconductor layer; the second layer group comprises B layers of quantum barrier layers arranged in succession, B being a positive integer; the Al composition of the quantum barrier layers of the second layer group gradually decreases in the first direction.

14. The method of claim 13, wherein the sum of A and B is equal to N-1.

15. The method of claim 13, wherein the step of growing the LED epitaxial structure is performed by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In the first direction, the second layer group comprises the first N-3 quantum barrier layers, and the first layer group comprises the N-2th and N-1th quantum barrier layers.

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