LED epitaxial wafer, growth method of LED epitaxial wafer and LED chip

Abstract

The invention provides an LED epitaxial wafer, a growth method of the LED epitaxial wafer and an LED chip. The LED epitaxial wafer comprises a substrate, a buffer layer, an N-type layer, a quantum well layer and a P-type layer which are sequentially stacked, the quantum well layer comprises a plurality of groups of quantum well structures, and each group of quantum well structure comprises a first GaN layer, an AlGaN layer, a second GaN layer and an InGaN layer which are stacked in sequence; and the multiple groups of quantum well structures are stacked in sequence. The quantum well layer increases radiative recombination of electrons and electron holes and improves luminous efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to an LED epitaxial wafer, a method for growing an LED epitaxial wafer, and an LED chip. Background Technology

[0002] Light Emitting Diode (LED) An LED (Emitting Diode) is a semiconductor electronic device that converts electrical energy into light energy. When current flows through an LED, electrons and holes recombine within its multiple quantum wells to emit monochromatic light. LED chips are fabricated based on LED epitaxial wafers. Existing gallium nitride (GaN)-based epitaxial wafers generally use sapphire (Al2O3) as a substrate, on which a buffer layer, an N-type layer, a quantum well layer, and a P-type layer are sequentially fabricated.

[0003] However, gallium nitride (GaN)-based LED chips have always suffered from piezoelectric and spontaneous polarization effects. The polarization effect generates a strong built-in electric field, which causes spatial separation of electrons and holes in the quantum well, thereby reducing the effective radiative recombination, i.e., photon emissivity. Summary of the Invention

[0004] Therefore, in order to improve the optical characteristics of LEDs and reduce the influence of polarization electric field on LED luminous power, the present invention provides an LED epitaxial wafer and its growth method.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: An LED epitaxial wafer includes a substrate, a buffer layer, an N-type layer, a quantum well layer, and a P-type layer stacked sequentially; wherein the quantum well layer includes multiple sets of quantum well structures, each set of quantum well structures including a first GaN layer, an AlGaN layer, a second GaN layer, and an InGaN layer stacked sequentially; the multiple sets of quantum well structures are stacked sequentially.

[0006] Furthermore, the number of quantum well structures in the quantum well layer is 5-12 groups.

[0007] Furthermore, each set of InGaN layers in the quantum well structure is divided into a first InGaN layer and a second InGaN layer stacked on the first InGaN layer in its thickness direction, and the band gap of the second InGaN layer is larger than that of the first InGaN layer.

[0008] Furthermore, the thickness of the first InGaN layer is 1-4 times the thickness of the second InGaN layer.

[0009] Furthermore, in the quantum well layer, at least the top 1-2 sets of AlGaN layers with quantum well structures are replaced with multiple sets of sequentially stacked AlGaN layers and a third GaN layer to form an AlGaN / GaN layer.

[0010] Furthermore, the AlGaN / GaN layer has 2-5 layers.

[0011] Furthermore, the substrate is a sapphire substrate, the buffer layer is an undoped GaN buffer layer, the N-type layer includes a Si-doped n-type GaN layer and a Si-doped AlGaN electron blocking layer stacked on the surface of the n-type GaN layer, and the P-type layer includes a Mg-doped p-type AlGaN layer and a Mg-doped p-type GaN layer stacked on the surface of the p-type AlGaN layer.

[0012] A method for growing an LED epitaxial wafer includes, in sequence: processing a substrate, growing a buffer layer, growing an N-type layer, growing a quantum well layer, and growing a P-type layer; wherein the specific steps for growing the quantum well layer are as follows: S1, the first GaN layer is grown at temperature T1, and the temperature is changed from T1 to T2 during the growth process; S2, an AlGaN layer is grown at temperature T2; S3, the second GaN layer is grown at temperature T2, and the temperature is changed from T2 to T1 during the growth process; S4, InGaN layers are grown at temperature T1; a set of quantum well structures are obtained; S5. Repeat steps S1-S4 and cycle multiple times to obtain a quantum well layer consisting of multiple sets of quantum well structures stacked sequentially.

[0013] Furthermore, the temperature T1 value is lower than the temperature T2 value.

[0014] Furthermore, the crystal growth process in step S4 is divided into two steps: S41, increasing the amount of TMI (trimethylindium) to prepare the first InGaN layer; S42, decreasing the amount of TMI to prepare the second InGaN layer; the stacked first InGaN layer and the second InGaN layer together constitute the InGaN layer; wherein, the band gap of the second InGaN layer is greater than the band gap of the first InGaN layer.

[0015] Furthermore, the thickness of the first InGaN layer is 1-4 times the thickness of the second InGaN layer. Furthermore, in step S5, steps S1-S4 are repeated multiple times to obtain a quantum well layer consisting of 5-12 sets of quantum well structures stacked sequentially.

[0016] Furthermore, in the quantum well layer, at least in the last 1-2 cycles, the crystal growth process of step S2 is divided into: S21, growing an AlGaN layer at temperature T2; S22, growing a third GaN layer at temperature T2; S23, repeating S21 and S22 multiple times to obtain multiple sets of sequentially stacked AlGaN layers and a third GaN layer to form an AlGaN / GaN layer.

[0017] An LED chip is prepared from the LED epitaxial wafer described above.

[0018] The technical solution provided by this invention has the following beneficial effects: 1. In this application, the quantum well layer is designed as multiple sets of quantum well structures stacked sequentially. Each set of quantum well structures includes a first GaN layer, an AlGaN layer, a second GaN layer, and an InGaN layer stacked sequentially. This quantum well layer increases the radiative recombination of electrons and holes, thereby improving the luminescence efficiency.

[0019] 2. Based on point 1 above, the InGaN layer of the quantum well structure is further divided into a first InGaN layer and a second InGaN layer stacked on the first InGaN layer in its thickness direction. The band gap of the second InGaN layer is larger than that of the first InGaN layer. This reduces the band tilt, increases the overlap integral of the electron-hole wave function, and improves radiative recombination, thereby further enhancing the luminous power of the LED.

[0020] 3. Based on point 1 or 2 above, furthermore, at least the top 1-2 sets of quantum well AlGaN layers are replaced with multiple sets of sequentially stacked AlGaN layers and a third GaN layer to form a deformed barrier structure of AlGaN / GaN layers, increasing the radiative recombination of electrons and holes, and further improving the luminescence efficiency. Attached Figure Description

[0021] Figure 1 The diagram shown is a schematic representation of the structure of the LED epitaxial wafer in the embodiment. Figure 2 The diagram shown is a schematic diagram of the single-layer quantum well structure of the LED epitaxial wafer in Example 1; Figure 3 The diagram shown is a schematic diagram of the energy band of the quantum well layer of the LED epitaxial wafer in Example 1; Figure 4 The diagram shown is a schematic diagram of the single-layer quantum well structure of the LED epitaxial wafer in Example 2; Figure 5 The diagram shown is a schematic diagram of the energy band structure of the quantum well layer of the LED epitaxial wafer in Example 2; Figure 6The diagram shown is a schematic diagram of the top quantum well structure of the LED epitaxial wafer in Example 3; Figure 7 The diagram shown is a schematic diagram of the energy band structure of the quantum well layer of the LED epitaxial wafer in Example 3; Figure 8 The diagram shown is a schematic diagram of the top quantum well structure of the LED epitaxial wafer in Example 4; Figure 9 The diagram shown is a schematic diagram of the energy band structure of the quantum well layer of the LED epitaxial wafer in Example 4; Figure 10 The image shows a comparison of photoelectric detection between multiple control and experimental groups. Detailed Implementation

[0022] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, primarily used to illustrate the embodiments and to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0023] In the description of this invention, terms such as "upper," "lower," "left," "right," "front," and "rear," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0025] Example 1 Reference Figure 1 As shown, this embodiment provides an LED epitaxial wafer, comprising a substrate 1, a buffer layer 2, an N-type layer 3, a quantum well layer 4, and a P-type layer 5 stacked sequentially. The substrate 1 is a sapphire (Al₂O₃) substrate, the buffer layer 2 is an undoped GaN buffer layer, the N-type layer 3 comprises a Si-doped n-type GaN layer 31 and a Si-doped AlGaN electron blocking layer 32 stacked on the surface of the n-type GaN layer 31, and the P-type layer 5 comprises a Mg-doped p-type AlGaN layer 51 and a Mg-doped p-type GaN layer 52 stacked on the surface of the p-type AlGaN layer 51. Specifically, the structures of the substrate 1, buffer layer 2, N-type layer 3, and P-type layer 5 described above are all prior art and not improvements of this application; therefore, they will not be described in detail here.

[0026] For details, please refer to... Figure 2As shown, the quantum well layer 4 includes 5-12 groups of quantum well structures 40, such as 12 groups of quantum well structures 40 used in this embodiment; each group of quantum well structures 40 includes a first GaN layer 41, an AlGaN layer 42, a second GaN layer 43, and an InGaN layer 44 stacked sequentially; the 12 groups of quantum well structures 40 are stacked sequentially to form a stepped quantum well layer 4, the energy band diagram of which is shown in the figure. Figure 3 As shown, this can effectively increase the radiative recombination of electrons and holes (i.e., cavitation holes), thereby improving luminescence efficiency.

[0027] This embodiment also provides a method for growing an LED epitaxial wafer, used to prepare the aforementioned LED epitaxial wafer. The growth method sequentially includes: processing a substrate 1, growing a buffer layer 2, growing an N-type layer 3, growing a quantum well layer 4, and growing a P-type layer 5. Specifically, the substrate 1 is a sapphire (Al2O3) substrate, and the buffer layer 2 is an undoped GaN buffer layer. The GaN buffer layer can be prepared in multiple stages, such as first preparing a nanometer-thick (e.g., 20 nm) bottom layer, and then preparing a micrometer-thick (e.g., 3 μm) top layer; the N-type layer... The substrate 3 includes a Si-doped n-type GaN layer 31 and a Si-doped AlGaN electron blocking layer 32 stacked on the surface of the n-type GaN layer 31. The p-type layer 5 includes a Mg-doped p-type AlGaN layer 51 and a Mg-doped p-type GaN layer 52 stacked on the surface of the p-type AlGaN layer 51. The thickness of the n-type GaN layer 31 is 2.5 μm; the thickness of the electron blocking layer (i.e., the AlGaN electron blocking layer 32) is 120 nm; the thickness of the p-type AlGaN layer 51 is 30 nm; and the thickness of the p-type GaN layer 52 is 60 nm. The processing of the substrate 1, the growth and preparation of the buffer layer 2, the N-type layer 3, and the p-type layer 5 are all existing technologies, and their thicknesses can be adjusted according to actual conditions; they will not be described in detail here.

[0028] The specific steps for growing quantum well layer 4 are as follows: S1, the first GaN layer 41 is grown at a temperature T1 (700℃-800℃ in this embodiment), and the temperature is changed from T1 to T2 (840℃-900℃ in this embodiment) during the growth process; specifically, the thickness of the first GaN layer 41 is 2nm-5nm. S2, an AlGaN layer 42 is grown at a temperature T2; specifically, the thickness of the AlGaN layer 42 is 2nm-5nm. S3, a second GaN layer 43 is grown at temperature T2, and the temperature is changed from T2 to T1 during the growth process; specifically, the thickness of the second GaN layer 43 is 2nm-5nm; S4, InGaN44 is grown at temperature T1; specifically, the thickness of the InGaN layer 44 is 2nm-4nm; Thus, we obtain a set of... Figure 2 The quantum well structure 40 shown; S5, repeat steps S1-S4, and cycle multiple times; to obtain a quantum well layer 4 consisting of 12 sets of quantum well structures 40 stacked sequentially.

[0029] Specifically, temperature T1 is the preparation temperature for growing InGaN layer 44, and temperature T2 is the preparation temperature for growing AlGaN layer 42. The first GaN layer 41 and the second GaN layer 43 are both transition layers. Of course, in other embodiments, the values ​​of temperature T1 and temperature T2 are not limited to these.

[0030] Specifically, the thickness of each of the above-mentioned layers is one of the preferred thicknesses in this application. Of course, in other embodiments, the thickness of each layer can be adjusted according to the actual situation.

[0031] This embodiment also provides an LED chip, which is prepared from the LED epitaxial wafer described above.

[0032] Example 2 This embodiment provides an LED epitaxial wafer, the structure of which is largely the same as that of Embodiment 1, except that: Figure 4 As shown, in this embodiment, the InGaN layer 44 of each group of quantum well structures 40 is further improved, specifically: the InGaN layer 44 of the quantum well structure 40 is divided into a first InGaN layer 441 and a second InGaN layer 442 stacked on the first InGaN layer 441 in its thickness direction, and the band gap of the second InGaN layer 442 is larger than the band gap of the first InGaN layer 441; thus forming a stepped quantum well structure 40 with a gradient change in In composition.

[0033] The blue shift in quantum well layer 4 is caused by its physical mechanism. Due to the presence of the polarization field, the energy band is tilted, leading to spatial separation of electrons and holes. When the injection current increases, the injected carriers shield the polarization field. This charge shielding mitigates the quantum-bound Stark effect, and the band gap may also be a factor, resulting in an increase in the energy distance between the conduction and valence bands, thus causing a blue shift in wavelength. However, as the injection current continues to increase, the thermal effect of the chip becomes the dominant factor, leading to a decrease in the band gap and a red shift in wavelength. The energy band diagram of the quantum well layer 4 structure in this embodiment is shown below. Figure 5 As shown, this can reduce the bandgap, increase the overlap integral of the electron-hole wavefunction, and improve radiative recombination, thereby further enhancing the luminous power of the LED.

[0034] Furthermore, the thickness of the first InGaN layer 441 is preferably 1-4 times the thickness of the second InGaN layer 442. This is to increase the recombination efficiency of electrons and holes, so that the main luminescence is concentrated in the InGaN layer 441 as much as possible, avoiding an excessively thick InGaN layer 442 which would reduce luminescence purity.

[0035] Furthermore, this embodiment also provides a method for growing an LED epitaxial wafer, used to prepare the LED epitaxial wafer described above. The growth method is largely the same as the method provided in Embodiment 1, except that: step S4 uses the TMI flow rate and crystal growth time to control the In composition of the quantum well; the crystal growth process is specifically divided into two steps: S41, increasing the TMI amount to prepare the first InGaN layer 441; S42, decreasing the TMI amount to prepare the second InGaN layer 442; the stacked first InGaN layer 441 and second InGaN layer 442 together constitute the InGaN layer 44; as in this specific embodiment, if in Embodiment 1 a single layer... When the thickness of the InGaN layer 44 is set to 3nm, the crystal growth time is 2 minutes and 30 seconds. Therefore, this 2 minutes and 30 seconds crystal growth time can be divided into 1 minute and 30 seconds and 1 minute. Specifically, in step S41, the TMI amount is increased by 15% and crystal growth is performed for 1 minute and 30 seconds to form the first InGaN layer 441 with a small band gap. In step S42, the TMI amount is reduced by 25% and crystal growth is performed for 1 minute to form the second InGaN layer 442 with a large band gap. That is, the band gap of the second InGaN layer 442 is greater than that of the first InGaN layer 441. Preferably, the thickness of the first InGaN layer 441 is 1-4 times the thickness of the second InGaN layer 442. This yields the LED epitaxial wafer of this embodiment.

[0036] This embodiment also provides an LED chip, which is prepared from the LED epitaxial wafer described above.

[0037] Example 3 This embodiment provides an LED epitaxial wafer, the structure of which is largely the same as that of Embodiment 1, except that: Figure 6 As shown, in this embodiment, in the quantum well layer 4, at least the top 1-2 groups (i.e., the 12th group, or the 11th and 12th groups) of the AlGaN layers 42 of the quantum well structure 40 are replaced with multiple groups of sequentially stacked AlGaN layers 421 and third GaN layers 422 to form an AlGaN / GaN layer, resulting in a superlattice structure. The number of AlGaN / GaN layers is 2-5. In this embodiment, the last 2 groups (i.e., the 11th and 12th groups) of the quantum well structure 40's AlGaN layers 42 are replaced with 3 AlGaN / GaN layers, i.e., there are 3 groups of sequentially stacked AlGaN layers 421 and third GaN layers 422.

[0038] Specifically, the thicknesses of the AlGaN layer 421 and the third GaN layer 422 in the AlGaN / GaN layer can be the same or different.

[0039] The scheme in this embodiment changes the energy level of the barrier, and its energy band diagram is as follows. Figure 7 As shown, the quality of the barrier crystal growth is improved, thereby increasing radiative recombination; which in turn further improves the luminescence efficiency.

[0040] Of course, the structure in this embodiment is one of the preferred solutions. In other embodiments, the AlGaN / GaN layer can replace more AlGaN layers 42 in the quantum well structure 40.

[0041] This embodiment also provides a method for growing an LED epitaxial wafer, used to prepare the LED epitaxial wafer described above. The growth method is largely the same as that provided in Embodiment 1, except that: in the quantum well layer, at least in the last 1-2 cycles, the crystal growth process in step S2 is divided into: S21, growing an AlGaN layer 421 at temperature T2; S22, growing a third GaN layer 422 at temperature T2; wherein the AlGaN layer 421 obtained in S21 and the third GaN layer 422 obtained in S22 have the same thickness; S23, repeating S21 and S22 multiple times to obtain 2-5 groups (3 groups in this specific embodiment) of sequentially stacked AlGaN layers 421 and third GaN layers 422 to form a superlattice structure AlGaN / GaN layer. This yields the LED epitaxial wafer of this embodiment.

[0042] This embodiment also provides an LED chip, which is prepared from the LED epitaxial wafer described above.

[0043] Example 4 This embodiment provides an LED epitaxial wafer that, based on Embodiment 1, combines the structures of Embodiments 2 and 3. Specifically, based on the structure of the LED epitaxial wafer in Embodiment 1, the InGaN layer of the quantum well structure is further improved. Specifically, each group of the quantum well structure 40 has an InGaN layer 44 divided into a first InGaN layer 441 and a second InGaN layer 442 stacked on the first InGaN layer 441 in its thickness direction. The band gap of the second InGaN layer 442 is larger than the band gap of the first InGaN layer 441, thus forming a stepped quantum well structure 40 with a gradient change in In composition.

[0044] Simultaneously, at least the AlGaN layers 42 in the top 1-2 groups (i.e., in the 12th group, or in the 11th and 12th groups) of the quantum well structure 40 are replaced with multiple groups of sequentially stacked AlGaN layers 421 and a third GaN layer 422 to form an AlGaN / GaN layer, resulting in a superlattice structure, such as the single-layer quantum well structure 40. Figure 8 As shown; the energy band diagram of the obtained quantum well layer 4 is as follows. Figure 9 As shown.

[0045] The growth method of the LED epitaxial wafer is also described in accordance with the relevant descriptions of Embodiment 1, Embodiment 2 and Embodiment 3 above, and will not be repeated here.

[0046] This embodiment also provides an LED chip, which is prepared from the LED epitaxial wafer described above.

[0047] The above discloses four preferred embodiments of this application. Based on these, the following tests are planned for this application: Control group 1: LED epitaxial wafers using existing technology, the structure of which is: a substrate, a buffer layer, an N-type layer, an electron blocking layer, a quantum well layer and a P-type layer stacked in sequence. The quantum well layer is an existing structure, that is, a 12-group quantum well structure, each group of quantum well structures is obtained by stacking GaN layers and InGaN layers.

[0048] Control group 2: The structure of the LED epitaxial wafer used is as follows: a substrate, a buffer layer, an N-type layer, an electron blocking layer, a quantum well layer and a P-type layer are stacked in sequence. The quantum well layer adopts 12 groups of quantum well structures. Each group of quantum well structures includes a first GaN layer, an InGaN layer, a second GaN layer and an AlGaN layer stacked in sequence. That is, compared with Embodiment 1 of this application, only the order of the InGaN layer and the AlGaN layer has been changed.

[0049] Experimental Group 1: The LED epitaxial wafer provided in Example 1 of this application was used.

[0050] Experimental Group 2: The LED epitaxial wafer provided in Example 4 of this application was used.

[0051] LED chips were fabricated from the four types of LED epitaxial wafers under the same conditions; photoelectric detection was performed on bare die (unpackaged) chips, with 1000 LED chips used in each group for photoelectric detection, and the radiant power (i.e., brightness) at the 454nm main wavelength was compared. Figure 10 As shown; the unit is mW.

[0052] The LED chip prepared in experimental group 1 had a brightness that was about 2% higher than that prepared in control group 1, which is obviously a significant improvement.

[0053] The LED chip prepared in experimental group 1 had a brightness that was about 0.5% higher than that prepared in control group 2; and the brightness distribution was more concentrated.

[0054] The LED chip prepared in Experiment 2 showed a brightness increase of about 0.5% compared to the LED chip prepared in Experiment 1; and the brightness distribution was more concentrated, resulting in further improvement.

[0055] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. An LED epitaxial wafer, comprising a substrate, a buffer layer, an N-type layer, a quantum well layer, and a P-type layer sequentially stacked; characterized in that: The quantum well layer includes multiple sets of quantum well structures, each set of quantum well structures including a first GaN layer, an AlGaN layer, a second GaN layer and an InGaN layer stacked sequentially; the multiple sets of quantum well structures are stacked sequentially. Furthermore, in the quantum well layer, at least the top 1-2 sets of AlGaN layers with quantum well structures are replaced with multiple sets of sequentially stacked AlGaN layers and a third GaN layer to form an AlGaN / GaN layer.

2. The LED epitaxial wafer according to claim 1, characterized in that: The number of quantum well structures in the quantum well layer is 5-12 groups.

3. The LED epitaxial wafer according to claim 1, characterized in that: Each group of quantum well structures has an InGaN layer divided into a first InGaN layer and a second InGaN layer stacked on the first InGaN layer in the thickness direction, and the band gap of the second InGaN layer is larger than that of the first InGaN layer.

4. The LED epitaxial wafer according to claim 3, characterized in that: The thickness of the first InGaN layer is 1 to 4 times the thickness of the second InGaN layer.

5. The LED epitaxial wafer according to claim 1, characterized in that: The AlGaN / GaN layer has 2-5 layers.

6. The LED epitaxial wafer according to claim 1, characterized in that: The substrate is a sapphire substrate, the buffer layer is an undoped GaN buffer layer, the N-type layer includes a Si-doped n-type GaN layer and a Si-doped AlGaN electron blocking layer stacked on the surface of the n-type GaN layer, and the P-type layer includes a Mg-doped p-type AlGaN layer and a Mg-doped p-type GaN layer stacked on the surface of the p-type AlGaN layer.

7. A method for growing an LED epitaxial wafer, comprising the following steps: The process involves processing a substrate, growing a buffer layer, growing an N-type layer, growing a quantum well layer, and growing a P-type layer; characterized in that the specific steps for growing the quantum well layer are as follows: S1, the first GaN layer is grown at temperature T1, and the temperature is changed from T1 to T2 during the growth process; S2, an AlGaN layer is grown at temperature T2; S3, the second GaN layer is grown at temperature T2, and the temperature is changed from T2 to T1 during the growth process; S4, InGaN layers are grown at temperature T1; a set of quantum well structures are obtained; S5. Repeat steps S1-S4 and cycle multiple times to obtain a quantum well layer consisting of multiple sets of quantum well structures stacked sequentially. Furthermore, in the quantum well layer, at least in the last 1-2 cycles, the crystal growth process of step S2 is divided into: S21, growing an AlGaN layer at temperature T2; S22, growing a third GaN layer at temperature T2; S23, repeating S21 and S22 multiple times to obtain multiple sets of sequentially stacked AlGaN layers and a third GaN layer to form an AlGaN / GaN layer.

8. The method for growing an LED epitaxial wafer according to claim 7, characterized in that: The temperature T1 value is lower than the temperature T2 value.

9. The method for growing an LED epitaxial wafer according to claim 7, characterized in that: The crystal growth process in step S4 is divided into two steps: S41, increasing the amount of TMI to prepare the first InGaN layer; S42, decreasing the amount of TMI to prepare the second InGaN layer; the stacked first InGaN layer and the second InGaN layer together constitute the InGaN layer; wherein, the band gap of the second InGaN layer is greater than the band gap of the first InGaN layer; the thickness of the first InGaN layer is 1-4 times the thickness of the second InGaN layer.

10. The method for growing an LED epitaxial wafer according to claim 7, characterized in that: In step S5, steps S1-S4 are repeated multiple times to obtain a quantum well layer consisting of 5-12 sets of quantum well structures stacked sequentially.

11. An LED chip, characterized in that: The LED chip is prepared from the LED epitaxial wafer described in any one of claims 1 to 6.

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