Epitaxial structure of long-wavelength ingan-based light-emitting diode, and preparation method therefor

Abstract

Disclosed in the present invention are an epitaxial structure of a long-wavelength InGaN-based light-emitting diode, and a preparation method therefor. The epitaxial structure comprises a substrate, an unintentionally doped gallium nitride layer, an n-type doped gallium nitride layer, a trench-type multi-quantum well, a repair layer, a light-emitting multi-quantum well and a p-type doped gallium nitride layer, wherein the surface of the trench-type multi-quantum well has an annular V-pit, which provides stress relaxation for the trench-type multi-quantum well and the repair layer, such that crystal lattices of the repair layer are expanded, thereby facilitating an increase in the incorporation of indium in the light-emitting multi-quantum well, and the annular V-pit serves as a spatial isolator to prevent carriers in a quantum well inside the annular V-pit from being affected by external defects; the repair layer repairs a rough surface of the trench-type multi-quantum well that grows at a low temperature, so as to provide a smooth growth surface for the light-emitting multi-quantum well that grows subsequently; and the repair layer serves as a hole barrier layer to block holes, which are from the p-type doped gallium nitride layer, from entering the trench-type multi-quantum well, such that the holes are concentrated in the light-emitting multi-quantum well and used for radiative recombination.

Description

An epitaxial structure of a long-wavelength InGaN-based light-emitting diode and a preparation method thereof

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on December 15, 2023, with application number CN202311727409.9 and invention name “A long-wavelength InGaN-based light-emitting diode epitaxial structure and its preparation method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the field of semiconductor devices, and in particular to an epitaxial structure of a long-wavelength InGaN-based light-emitting diode and a preparation method thereof. Background Art

[0003] Highly efficient indium gallium nitride (InGaN)-based light-emitting diodes (LEDs) play an important role in lighting, display, visible light communications, and biomedical health. Currently, full-color displays based on InGaN-based LEDs are a key requirement in the emerging display field. However, while the efficiency of blue and green InGaN-based LEDs is relatively high, the efficiency of red InGaN-based LEDs remains relatively low.

[0004] There are two main reasons for the low efficiency of red InGaN LEDs. One reason is the low growth temperature of the red quantum wells. For red InGaN LEDs with a high indium content, the quantum well growth temperature is generally below 700°C when using metalorganic vapor phase epitaxy (MOVPE) to maintain incorporation of In. However, low-temperature-grown multiple quantum wells typically contain a high density of defects, which significantly reduces the radiative recombination efficiency of red InGaN-based LEDs. Another factor is the excessive compressive stress introduced by the lattice mismatch in the red quantum wells. This compressive stress induces a strong polarization electric field in the InGaN quantum well layer, leading to the quantum-confined Stark effect. Furthermore, according to the principle of energy minimization, when the strain energy required for In-N bonding is large, compressive strain inhibits indium incorporation.

[0005] Due to the defect shielding and stress release effect of the V-pit structure, the V-pit (V-pits) structure in the multiple quantum well can be used to solve problems such as defects, polarization electric fields and indium incorporation in red light quantum wells. In InGaN / GaN multiple quantum wells, there are two main sources of V-pits: one is a single V-pit structure induced by threading dislocations, and the other is a ring-shaped V-pit structure induced by stacking faults in quantum barriers, that is, a groove structure. In the past, a single V-pit structure induced by threading dislocations has been effectively used to improve the luminous efficiency of red light InGaN LEDs (Photon.Res.7,144-148(2019), Photon.Res.8,1671-1675(2020)). However, the groove structure induced by stacking faults has always been considered to be a defect structure that seriously reduces the luminous efficiency of InGaN LEDs.

[0006] In previous studies, trench structures significantly reduced the overall luminous efficiency of blue and green InGaN LEDs (Appl. Phys. Lett. 105, 112-110 (2014)). However, localized luminescence enhancement and wavelength redshift have been observed in quantum wells within some trench structures (Appl. Phys. Lett. 98, 141-908 (2011)). This localized intensity enhancement is primarily attributed to screening defects and stress relaxation within the trench structure, while the wavelength redshift is attributed to increased indium incorporation (Nanoscale, 14, 402 (2022)). Therefore, trench structures have the potential to improve the efficiency of red InGaN LEDs. However, there is currently a lack of reasonable control methods to utilize the shielding defects and stress relaxation effects of the trench structure to improve the overall luminous efficiency of red InGaN LEDs.

[0007] Summary of the Invention

[0008] In response to the above problems in the existing technology, the present invention proposes an epitaxial structure of a long-wavelength InGaN-based light-emitting diode and a preparation method thereof. By introducing grooves into the quantum well and utilizing the luminescence enhancement and wavelength red-shift effects of the grooves on the quantum well, a high-efficiency long-wavelength InGaN-based light-emitting diode epitaxial structure is prepared.

[0009] One object of the present invention is to provide an epitaxial structure of a long-wavelength InGaN-based light-emitting diode.

[0010] The epitaxial structure of the long-wavelength InGaN-based light-emitting diode of the present invention comprises: a substrate, an unintentionally doped gallium nitride layer, an n-type doped gallium nitride layer, a trench-type multi-quantum well, a repair layer, a light-emitting multi-quantum well and a p-type doped gallium nitride layer.

[0011] Preferably, the method for preparing the epitaxial structure comprises the following steps:

[0012] forming an unintentionally doped gallium nitride layer and an n-type doped gallium nitride layer in sequence on the substrate;

[0013] Growing a trench multi-quantum well epitaxially on the n-type doped gallium nitride layer, and forming a high-density trench on the surface during the epitaxial growth of the trench multi-quantum well by controlling the growth conditions, wherein the material of the trench multi-quantum well is In x Ga 1-x N / GaN, where x is the indium component in a trench-type multi-quantum well. The trenches of the trench-type multi-quantum well serve as spatial isolation to prevent carriers in the quantum wells inside the trench from being affected by external defects.

[0014] forming a repair layer on the trench-type multi-quantum well, the repair layer being used to repair the rough surface of the trench-type multi-quantum well, providing a smooth growth surface for the subsequently grown light-emitting multi-quantum well, and the repair layer acting as a hole blocking layer, blocking holes from the p-type doped gallium nitride layer from entering the trench-type multi-quantum well, so that the holes are concentrated in the light-emitting multi-quantum well for radiative recombination;

[0015] Epitaxially grow a luminescent multi-quantum well on the repair layer. The luminescent multi-quantum well is used as a luminescent quantum well when current is injected, and is used to emit light of a long set wavelength. The material of the luminescent multi-quantum well is In z Ga 1-z N / GaN, wherein z is the indium component in the light-emitting multi-quantum well, and the indium component z in the light-emitting multi-quantum well is greater than the indium component x in the trench-type multi-quantum well; the trenches in the trench-type multi-quantum well provide stress relaxation for the repair layer, thereby expanding the lattice of the repair layer, thereby increasing incorporation of indium into the light-emitting multi-quantum well, and the increased incorporation of indium into the light-emitting multi-quantum well reduces the band gap width of the well layer of the light-emitting multi-quantum well, thereby achieving long-wavelength luminescence;

[0016] A p-type doped gallium nitride layer is formed on the light-emitting multi-quantum well to obtain the epitaxial structure of the long-wavelength InGaN-based light-emitting diode.

[0017] The substrate is made of sapphire (Al2O3), silicon (Si) or silicon carbide (SiC).

[0018] The thickness of the unintentionally doped gallium nitride layer is 1 μm to 5 μm, the thickness of the n-type doped gallium nitride layer is 1 μm to 10 μm; the doping concentration of the n-type doped gallium nitride layer is 1×10 18 cm -3 ~1×10 20 cm -3 .

[0019] In the trench-type multiple quantum well x Ga 1-x The indium component of N satisfies 0.1≤x≤0.4. The density of the grooves generated on the surface of the grooved multi-quantum well is 1×10 7 cm -2 ~1×10 10 cm -2 The lateral size of a single groove is 10nm~1μm, and the depth is 10nm~300nm.

[0020] The thickness of the repair layer is less than 500nm; the material of the repair layer is In y Ga 1-y N thick film, In y Ga 1-y N / GaN superlattice or gallium nitride layer, where y is the In in the repair layer y Ga 1-y The indium component in N is 0.01≤y≤0.2, and the indium component of the repair layer is lower than the indium component of the trench-type multi-quantum well.

[0021] In the light-emitting multi-quantum well z Ga 1-z The indium component of N satisfies 0.2≤z≤0.5, and the indium component of the light-emitting multi-quantum well is higher than the indium component of the trench-type multi-quantum well.

[0022] Another object of the present invention is to provide a method for preparing an epitaxial structure of a long-wavelength InGaN-based light-emitting diode.

[0023] The method for preparing the epitaxial structure of a long-wavelength InGaN-based light-emitting diode of the present invention comprises the following steps:

[0024] 1) Providing a substrate capable of growing gallium nitride;

[0025] 2) epitaxially growing an unintentionally doped gallium nitride layer and an n-type doped gallium nitride layer on the substrate;

[0026] 3) epitaxially growing a trench multi-quantum well on the n-type doped gallium nitride layer, and simultaneously generating a high-density trench on the surface during the epitaxial growth of the trench multi-quantum well by controlling the growth conditions; the growth conditions for generating the high-density trench are to reduce the growth temperature of the well layer and / or the barrier layer, use trimethyl gallium (TMGa) as a metal source, reduce the flow ratio of ammonia (NH3) to the metal source, or increase the flow ratio of trimethyl indium (TMIn) to triethyl gallium (TEGa); the material of the trench multi-quantum well is In x Ga 1-xN / GaN, wherein x is the indium component in the trench multi-quantum well; the trench multi-quantum well comprises a plurality of overlapping well layers and barrier layers, and the material of the well layer is In x Ga 1-x N, where x is the indium component in the trench-type multi-quantum well, and the material of the barrier layer is GaN; the trench of the trench-type multi-quantum well serves as a spatial isolation to prevent the carriers in the quantum well inside the trench from being affected by external defects;

[0027] 4) epitaxially growing a repair layer on the trench multi-quantum well, wherein the growth temperature of the repair layer is higher than the growth temperature of the trench multi-quantum well; the repair layer is used to repair the rough surface of the trench multi-quantum well, providing a flat growth surface for the subsequently grown light-emitting multi-quantum well, and the repair layer acts as a hole blocking layer to block holes from the p-type doped gallium nitride layer from entering the trench multi-quantum well, so that the holes are concentrated in the light-emitting multi-quantum well for radiative recombination;

[0028] 5) epitaxially growing a luminescent multi-quantum well on the repair layer, and in the process of epitaxially growing the luminescent multi-quantum well, controlling the growth conditions to avoid the formation of unintentionally introduced grooves, and the luminescent multi-quantum well serves as a luminescent layer when current is injected, for emitting long-wavelength light; the well layer of the luminescent multi-quantum well is made of In z Ga 1-z N, wherein z is the indium component in the light-emitting multi-quantum well; the light-emitting multi-quantum well comprises a plurality of overlapping well layers and barrier layers, and the material of the well layer is In z Ga 1-z N, wherein z is the indium component in the light-emitting multi-quantum well, and the material of the barrier layer is GaN; the indium component z in the light-emitting multi-quantum well is greater than the indium component x in the trench-type multi-quantum well; the trenches in the light-emitting multi-quantum well provide stress relaxation for the repair layer, so that the lattice of the repair layer is expanded, thereby increasing the incorporation of indium in the light-emitting multi-quantum well, and the increased incorporation of indium in the light-emitting multi-quantum well reduces the band gap width of the well layer of the light-emitting multi-quantum well, thereby achieving long-wavelength luminescence;

[0029] 6) Growing a p-type doped gallium nitride layer on the light-emitting multi-quantum well to obtain the epitaxial structure of the long-wavelength InGaN-based light-emitting diode.

[0030] Wherein, in step 1), the material of the substrate is sapphire (Al2O3), silicon (Si) or silicon carbide (SiC).

[0031] In step 2), the thickness of the unintentionally doped gallium nitride layer is 1 μm to 5 μm, the thickness of the n-type doped gallium nitride layer is 1 μm to 10 μm; the doping concentration of the n-type doped gallium nitride layer is 1×10 18 cm-3 ~1×10 20 cm -3 .

[0032] In step 3), the indium component x in the trench multi-quantum well satisfies 0.1≤x≤0.4. The density of the trenches generated on the surface of the trench multi-quantum well is 1×10 7 cm -2 ~1×10 10 cm -2 The lateral dimension of a single trench is 10 nm to 1 μm, and the depth is 10 nm to 300 nm. The growth conditions for generating the trench are: the temperature of the well layer growth is 500° C. to 750° C., and the temperature of the barrier layer is 600° C. to 850° C.; the flow ratio of trimethyl indium (TMIn) to triethyl gallium (TEGa) is 5 to 50; or, the flow ratio of ammonia (NH3) to the metal source is 50 to 500.

[0033] In step 4), the thickness of the repair layer is less than 500 nm; the material of the repair layer is In y Ga 1-y N thick film, In y Ga 1-y N / GaN superlattice or gallium nitride layer, where y is the In in the repair layer y Ga 1-y The indium component in N is 0.01≤y≤0.2; the growth temperature of the repair layer is 750°C to 1000°C.

[0034] In step 5), the indium component z in the light-emitting multi-quantum well satisfies 0.2≤z≤0.5; wherein the growth temperature of the well layer of the light-emitting multi-quantum well is 600°C to 750°C, the growth temperature of the barrier layer is 700°C to 900°C, and triethylgallium is used as the metal source, and the flow ratio of trimethylindium (TMIn) to triethylgallium (TEGa) is 1 to 20.

[0035] Advantages of the present invention:

[0036] (1) The grooves in the trench-type multi-quantum wells provide stress relaxation for the repair layer, which expands the lattice of the repair layer and is conducive to improving the incorporation of indium in the light-emitting multi-quantum wells;

[0037] (2) The trenches in the trench-type multi-quantum wells act as spatial isolation to prevent the carriers in the quantum wells inside the trenches from being affected by external defects;

[0038] (3) The repair layer repairs the rough surface of the low-temperature grown trench multi-quantum wells, providing a smooth growth surface for the subsequent growth of light-emitting multi-quantum wells;

[0039] The repair layer acts as a hole blocking layer, blocking holes from the p-type doped gallium nitride layer from entering the trench multi-quantum wells, so that the holes are concentrated in the light-emitting multi-quantum wells for radiative recombination. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG1 is a block diagram of the epitaxial structure of a long-wavelength InGaN-based light-emitting diode according to the present invention;

[0041] FIG2 is a cross-sectional view of an embodiment of the epitaxial structure of a long-wavelength InGaN-based light-emitting diode of the present invention;

[0042] FIG3 is a scanning electron microscope image of the surface of a trench-type multi-quantum well of an embodiment of the epitaxial structure of a long-wavelength InGaN-based light-emitting diode of the present invention;

[0043] FIG4 is a schematic diagram of a trench in a trench-type multi-quantum well of an embodiment of an epitaxial structure of a long-wavelength InGaN-based light-emitting diode of the present invention;

[0044] FIG5 is a scanning electron microscope image of the surface of the repair layer of an embodiment of the epitaxial structure of a long-wavelength InGaN-based light-emitting diode of the present invention;

[0045] FIG6 is a fluorescence spectrum diagram of an embodiment of the epitaxial structure of a long-wavelength InGaN-based light-emitting diode of the present invention under a 405 nm laser. DETAILED DESCRIPTION

[0046] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0047] As shown in Figures 1 and 2, the method for preparing the epitaxial structure of the long-wavelength InGaN-based light-emitting diode of this embodiment includes the following steps:

[0048] 1) Providing sapphire as a substrate 100;

[0049] 2) The substrate 100 is placed in an MOCVD reaction chamber and heated to 1050°C in an H2 atmosphere for 10 minutes of purging. The temperature is then lowered to 540°C, and TMGa, NH3, and H2 are introduced to grow a nucleation layer. The temperature is then raised to 1040°C to grow a 2 μm thick undoped GaN layer 200.

[0050] TMGa, NH3, SiH4 and H2 are introduced to grow an n-type doped gallium nitride layer 300 with a thickness of 1.5 microns on the undoped gallium nitride layer 200 at a temperature of 1060°C;

[0051] 3) The temperature was lowered to 690° C., TEGa, NH 3 , SiH 4 and N 2 were introduced to grow periodic trench multi-quantum wells. The trench multi-quantum wells in this embodiment are eight periods of green quantum wells 400, each period including an InGaN green quantum well layer 401 and a trench GaN barrier layer 402. The InGaN green quantum well layer 401 was grown at a temperature of 630° C., TEGa, TMIn, NH 3 and N 2 were introduced, and the growth thickness was 2.5 nm, with an indium component of approximately 25%. The trench GaN barrier layer 402 was grown at a temperature of 690° C., TEGa, NH 3 and N 2 were introduced, and the thickness was 10 nm. A scanning electron microscope image of the surface of the trench multi-quantum well is shown in FIG3 . Due to the low growth temperature, a density of approximately 5×10 9 cm -2 As shown in the schematic diagram of the trench in Figure 4, the trench in the trench-type multiple quantum well serves as a spatial isolation to prevent the carriers in the quantum well inside the trench from being affected by external defects;

[0052] 4) Epitaxial growth of n-type doped In on the trench multi-quantum well 0.05 Ga 0.95 N thick film, as the repair layer 500; raise the temperature to 790 ℃, introduce TEGa, TMIn, NH3, SiH4 and N2, grow 80nm thick n-type doped In 0.05 Ga 0.95 N thick film, since the growth temperature is higher than the previous green quantum well, the surface flatness will be improved; at the same time, the n-type doped In 0.05 Ga 0.95 The N repair layer 500 acts as a hole blocking layer, preventing holes from entering the green quantum well under electrical injection conditions. In addition, as shown in FIG5 , the compressive stress on the repair layer 500 is reduced due to the presence of high-density trenches in the green quantum well, and thus the lattice itself is expanded, which facilitates the incorporation of indium into the subsequent quantum well.

[0053] 5) Epitaxially growing a light-emitting multi-quantum well on the repair layer. The light-emitting multi-quantum well in this embodiment is a three-period red light quantum well 600, each period comprising an InGaN red light quantum well layer 601 and a red light GaN barrier layer 602. The InGaN red light quantum well layer 601 is grown at a temperature of 665°C, with TEGa, TMIn, NH3, and N2 introduced, to a thickness of 2.5 nm, and an indium component of approximately 40%. The red light GaN barrier layer 602 is grown at a temperature of 770°C, with TEGa, NH3, and N2 introduced, to a thickness of 10 nm. The light-emitting multi-quantum well serves as the light-emitting layer during current injection. During laser excitation, both the light-emitting multi-quantum well and the trench multi-quantum well serve as the light-emitting layer.

[0054] The grooves in the trench-type multi-quantum wells provide stress relaxation for the repair layer, so that the lattice of the repair layer is expanded, thereby increasing the incorporation of indium in the luminescent multi-quantum wells. The incorporation of indium provides high efficiency, enabling long-wavelength luminescence.

[0055] 6) A p-type doped gallium nitride layer 700 is grown on the light-emitting multi-quantum well, and TMGa, NH3, Cp2Mg and H2 are introduced at 920°C to a thickness of about 150nm to obtain the epitaxial structure of a long-wavelength InGaN-based light-emitting diode.

[0056] After completing the epitaxial structure of the long-wavelength InGaN-based light-emitting diode, an epitaxial wafer emitting in the red wavelength band is obtained. Figure 6 shows the fluorescence spectrum of this red epitaxial wafer under a 405nm laser. The figure shows that the emission spectrum includes green light with a peak wavelength of approximately 525nm and red light with a peak wavelength of approximately 625nm. The green light originates from the trench multi-quantum wells, while the red light originates from the light-emitting quantum wells. Because the trench multi-quantum wells are grown at low temperatures, the density of defects within the quantum wells is high, such as stacking faults and misfit dislocations. These defects weaken the intensity of the green emission. Under current injection, the underlying green quantum wells do not participate in the emission due to the weak mobility of holes. However, the low temperature introduces a high density of trenches into the green quantum wells, as shown in Figure 4. This high density of trenches helps enhance the emission of the subsequent red quantum wells.

[0057] Although the low-temperature grown green quantum well will introduce high-density grooves, the low temperature will cause its surface to coarsen and the crystal quality to be poor, making it difficult to provide a smooth and high-quality crystal surface for the growth of the red quantum well. Therefore, after the green quantum well is introduced into the groove, the growth of the repair layer is particularly important. In this embodiment, the growth temperature of the InGaN thick film of the repair layer is more than 100 degrees higher than that of the green quantum well, the surface flatness is high, and the crystal quality is relatively good, providing a good growth surface for the red quantum well. In addition, the grooves can be retained in the repair layer. As shown in Figure 5, the surface of the repair layer still has a density of about 2×10 9 cm -2 At the same time, due to the presence of high-density grooves, the compressive stress on the repair layer InGaN thick film itself will be partially relaxed, and the lattice will be expanded, which will facilitate the subsequent incorporation of indium in the red light quantum well. Therefore, the main functions of the repair layer InGaN thick film in this embodiment are: (1) repairing the rough surface of the green light quantum well; (2) retaining the high-density grooves; (3) relaxing its own stress, which plays a role in expanding the lattice. In the subsequent red light quantum well, the high-density grooves can provide a defect shielding effect and make the incorporation of indium more efficient, which provides a new idea for achieving high-efficiency red light InGaN LEDs.

[0058] Finally, it should be noted that the purpose of disclosing the embodiments is to facilitate a further understanding of the present invention. However, those skilled in the art will appreciate that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the contents disclosed in the embodiments; the scope of protection claimed by the present invention shall be determined by the scope defined in the claims.

Claims

1. An epitaxial structure of a long-wavelength InGaN-based light-emitting diode, characterized in that: The epitaxial structure includes: a substrate, an unintentionally doped gallium nitride layer, an n-type doped gallium nitride layer, a trench-type multi-quantum well, a repair layer, a light-emitting multi-quantum well, and a p-type doped gallium nitride layer; The material of the trench-type multiple quantum well is In x Ga 1-x N / GaN, where x is the indium component in the trench multiple quantum well; The repair layer acts as a hole blocking layer; The material of the light-emitting multiple quantum well is In z Ga 1-z N / GaN, wherein z is the indium component in the light-emitting multi-quantum well; the indium component z in the light-emitting multi-quantum well is greater than the indium component x in the trench multi-quantum well.

2. The epitaxial structure according to claim 1, wherein the method for preparing the epitaxial structure comprises the following steps: forming an unintentionally doped gallium nitride layer and an n-type doped gallium nitride layer in sequence on a substrate; Growing a trench multi-quantum well epitaxially on the n-type doped gallium nitride layer, and forming high-density trenches on the surface during the epitaxial growth of the trench multi-quantum well by controlling the growth conditions, wherein the material of the trench multi-quantum well is In x Ga 1-x N / GaN, where x is the indium component in the trench multiple quantum well; forming a repair layer on the trench-type multiple quantum well; Epitaxially grow a light-emitting multi-quantum well on the repair layer, wherein the material of the light-emitting multi-quantum well is In z Ga 1-z N / GaN, wherein z is the indium component in the light-emitting multi-quantum well; the indium component z in the light-emitting multi-quantum well is greater than the indium component x in the trench multi-quantum well; A p-type doped gallium nitride layer is formed on the light-emitting multi-quantum well to obtain the epitaxial structure of the long-wavelength InGaN-based light-emitting diode.

3. The epitaxial structure according to claim 1, characterized in that: The thickness of the unintentionally doped gallium nitride layer is 1 μm to 5 μm, the thickness of the n-type doped gallium nitride layer is 1 μm to 10 μm; the doping concentration of the n-type doped gallium nitride layer is 1×10 18 cm -3 ~1×10 20 cm -3 .

4. The epitaxial structure according to claim 1, characterized in that: The In in the trench multiple quantum well x Ga 1-x The indium component of N satisfies 0.1≤x≤0.4; the density of the grooves generated on the surface of the grooved multi-quantum well is 1×10 7 cm -2 ~1×10 10 cm -2 The lateral dimension of a single groove is between 10nm and 1μm, and the depth is between 10nm and 300nm.

5. The epitaxial structure according to claim 1 or 4, characterized in that: The trench-type multi-quantum well comprises a plurality of mutually overlapping well layers and barrier layers; The material of the well layer is In x Ga 1-x N, wherein x is the indium component in the trench-type multiple quantum well; the material of the barrier layer is GaN.

6. The epitaxial structure according to claim 1, characterized in that: The thickness of the repair layer is less than 500nm; the material of the repair layer is In y Ga 1-y N thick film, In y Ga 1-y N / GaN superlattice or GaN layer, where y is the In in the repair layer y Ga 1-y The indium component in N is 0.01≤y≤0.2, and the indium component of the repair layer is lower than the indium component of the trench-type multiple quantum well.

7. The epitaxial structure according to claim 1, characterized in that: The indium component z in the light-emitting multiple quantum well satisfies 0.2≤z≤0.5, and the indium component of the light-emitting multiple quantum well is higher than the indium component of the trench-type multiple quantum well.

8. The epitaxial structure according to claim 1 or 7, characterized in that: The light-emitting multi-quantum well comprises a plurality of overlapping well layers and barrier layers; the material of the well layer is In z Ga 1-z N; the material of the barrier layer is GaN.

9. A method for preparing an epitaxial structure of a long-wavelength InGaN-based light-emitting diode as claimed in any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: 1) Providing a substrate capable of growing gallium nitride; 2) epitaxially growing an unintentionally doped gallium nitride layer and an n-type doped gallium nitride layer on the substrate in sequence; 3) epitaxially growing a trench multi-quantum well on the n-type doped gallium nitride layer, and by controlling the growth conditions, simultaneously generating high-density trenches on the surface during the epitaxial growth of the trench multi-quantum well; the material of the trench multi-quantum well is In x Ga 1-x N / GaN, where x is the indium component in the trench multiple quantum well; 4) epitaxially growing a repair layer on the trench-type multiple quantum well; 5) epitaxially growing a light-emitting multi-quantum well on the repair layer; the well layer of the light-emitting multi-quantum well is made of In z Ga 1-z N, wherein z is the indium component in the light-emitting multi-quantum well; the indium component z in the light-emitting multi-quantum well is greater than the indium component x in the trench multi-quantum well; 6) Growing a p-type doped gallium nitride layer on the light-emitting multi-quantum well to obtain the epitaxial structure of the long-wavelength InGaN-based light-emitting diode.

10. The preparation method according to claim 9, characterized in that: In the step 3), the indium component x in the trench-type multi-quantum well satisfies 0.1≤x≤0.4; the density of the trenches generated on the surface of the trench-type multi-quantum well is 1×10 7 cm -2 ~1×10 10 cm -2 The lateral dimension of a single groove is between 10nm and 1μm, and the depth is between 10nm and 300nm.

11. The preparation method according to claim 9, characterized in that: In the step 3), the growth conditions of the high-density trenches are: lowering the growth temperature of the well layer and / or barrier layer, using trimethylgallium as the metal source, lowering the flow ratio of ammonia to the metal source or increasing the flow ratio of trimethylindium to triethylgallium.

12. The preparation method according to claim 11, characterized in that: In the step 3), the growth conditions of the high-density grooves are: the temperature of the well layer growth is 500°C to 750°C, the temperature of the barrier layer is 600°C to 850°C; the flow ratio of trimethylindium to triethylgallium is 5 to 50; or, the flow ratio of ammonia to metal source is 50 to 500.

13. The preparation method according to claim 9, characterized in that: In the step 4), the thickness of the repair layer is less than 500 nm; the material of the repair layer is In y Ga 1-y N thick film, In y Ga 1-y N / GaN superlattice or GaN layer, where y is the In in the repair layer y Ga 1-y The indium component in N is 0.01≤y≤0.2; the growth temperature of the repair layer is 750°C to 1000°C; the growth temperature of the repair layer is higher than the growth temperature of the trench type multi-quantum well.

14. The preparation method according to claim 9, characterized in that: In the step 5), the indium component z in the light-emitting multi-quantum well satisfies 0.2≤z≤0.

5.

15. The preparation method according to claim 9, characterized in that: In the step 5), the growth temperature of the well layer of the light-emitting multi-quantum well is 600° C. to 750° C., the growth temperature of the barrier layer is 700° C. to 900° C., and triethylgallium is used as the metal source, and the flow ratio of trimethylindium to triethylgallium is 1 to 20.

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