Light-emitting diode epitaxial wafer, preparation method thereof, and light-emitting diode

Abstract

The present invention discloses a light-emitting diode epitaxial wafer, a method for preparing the same, and a light-emitting diode, relating to the field of semiconductor optoelectronic devices. The light-emitting diode comprises a substrate and a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially disposed on the substrate. The undoped GaN layer sequentially comprises a first GaN layer disposed on the buffer layer, a plurality of micromirror pillars arrayed on the first GaN layer, and a second GaN layer wrapped around the micromirror pillars. Each micromirror pillar has a periodic structure, with each period comprising a sequentially stacked Ta2O5 layer and a SiO2 layer, with the number of periods ranging from 1 to 20. Each micromirror pillar has a width of 0.1 to 10 μm and a height of 0.1 to 6 μm, with the distance between adjacent micromirror pillars ranging from 0.3 to 8 μm. Implementation of the present invention can improve the light extraction efficiency of the light-emitting diode epitaxial wafer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic devices, and in particular to a light-emitting diode epitaxial wafer and a preparation method thereof, and a light-emitting diode. Background Art

[0002] Factors influencing the light extraction efficiency of GaN-based LEDs include epitaxy and chip design. In epitaxy, the transition from a flat substrate to a PSS pattern reduces refraction of light emitted by the LED; however, as the PSS base width increases, growing GaN epitaxial crystals becomes more difficult. In epitaxial structure design, the P-type layer is thinned and coarsened, and a new epitaxial structure is introduced to reduce light absorption by the P-type layer and improve the light extraction efficiency of the LED. However, with the adjustment of the epitaxial structure, the thickness of the P-type GaN layer has become very thin, leaving little room for improving light extraction efficiency through epitaxial layer structures. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a light emitting diode epitaxial wafer and a preparation method thereof, which can improve the light efficiency of the light emitting diode.

[0004] Another technical problem to be solved by the present invention is to provide a light emitting diode with high luminous efficiency.

[0005] In order to solve the above problems, the present invention discloses a light-emitting diode epitaxial wafer, comprising a substrate and a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially arranged on the substrate; the undoped GaN layer sequentially comprises a first GaN layer arranged on the buffer layer, a plurality of micro-mirror pillars arrayed on the first GaN layer, and a second GaN layer wrapped around the micro-mirror pillars;

[0006] Among them, each micromirror column has a periodic structure, and each period includes Ta2O5 layers and SiO2 layers stacked in sequence, with the number of periods being 1 to 20; the width of each micromirror column is 0.1 to 10 μm, the height is 0.1 to 6 μm, and the distance between adjacent micromirror columns is 0.3 to 8 μm.

[0007] As an improvement of the above technical solution, the thickness of the first GaN layer is 0.5-2 μm, and the thickness of the second GaN layer is 0.8-5 μm.

[0008] As an improvement of the above technical solution, the ratio of the thickness of a single Ta2O5 layer to the thickness of a single SiO2 layer is 1:(1 to 5).

[0009] As an improvement to the above technical solution, the cross section of the micromirror column is triangular, trapezoidal, rectangular or circular.

[0010] As an improvement to the above technical solution, the cross section of the micromirror column is circular.

[0011] As an improvement of the above technical solution, the diameter of the micromirror column is 0.5-5 μm, and the height is 0.5-5 μm; the distance between adjacent micromirror columns is 0.5-2 μm.

[0012] Correspondingly, the present invention also discloses a method for preparing a light-emitting diode epitaxial wafer, which is used to prepare the above-mentioned light-emitting diode epitaxial wafer, and comprises:

[0013] A substrate is provided, and a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer are sequentially grown on the substrate; the undoped GaN layer sequentially includes a first GaN layer provided on the buffer layer, a plurality of micro-mirror pillars arrayed on the first GaN layer, and a second GaN layer wrapped around the micro-mirror pillars;

[0014] Each micromirror column has a periodic structure, and each period includes a Ta2O5 layer and a SiO2 layer, with the number of periods ranging from 1 to 20. The width of each micromirror column is 0.1 to 10 μm, the height is 0.1 to 6 μm, and the distance between adjacent micromirror columns is 0.3 to 8 μm.

[0015] The preparation method of the micro mirror column is: periodically growing a Ta2O5 layer and a SiO2 layer to obtain a micro mirror layer, and etching to form a plurality of arrays of micro mirror columns.

[0016] As an improvement of the above technical solution, the growth temperature of the first GaN layer is 1000-1500° C., and the growth pressure is 50-300 torr;

[0017] The growth temperature of the Ta2O5 layer is 1000-1000°C, and the growth pressure is 50-500 torr;

[0018] The growth temperature of the SiO2 layer is 1000-1100°C, and the growth pressure is 50-500 torr;

[0019] The growth temperature of the second GaN layer is 1000-1500° C., and the growth pressure is 50-300 Torr.

[0020] Correspondingly, the present invention also discloses a light emitting diode, which includes the light emitting diode epitaxial wafer mentioned above.

[0021] The implementation of the present invention has the following beneficial effects:

[0022] 1. The light-emitting diode epitaxial wafer of the present invention adopts a structure of a first GaN layer + micromirror column + second GaN layer to replace the traditional non-doped GaN layer. Among them, the micromirror column is a periodic structure, and each period includes a Ta2O5 layer and a SiO2 layer. Their refractive indexes are 2.18 / 1.50, respectively, which are smaller than the refractive index of GaN (2.5), thereby effectively improving the reflection efficiency of light from the epitaxial structure, improving the external quantum efficiency of the light-emitting diode, and improving the light extraction efficiency. Furthermore, by controlling the width, height and spacing of the micromirror column, the growth quality of other epitaxial layers can be improved while adjusting the reflected light efficiency. Moreover, by setting the first GaN layer and the second GaN layer, the gaps between the micromirror columns can be effectively filled, thereby improving the crystal quality of other layers subsequently grown.

[0023] 2. The cross-section of the micromirror column of the present invention is circular, which can better release stress, reduce the extension of dislocations and defects into the multi-quantum well layer, improve the crystal quality of the epitaxial wafer, and improve the luminous efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1 is a schematic structural diagram of a light emitting diode epitaxial wafer according to an embodiment of the present invention;

[0025] Figure 2 is a schematic structural diagram of an undoped GaN layer in one embodiment of the present invention;

[0026] Figure 3 2 is a schematic structural diagram of a micromirror column in one embodiment of the present invention;

[0027] Figure 4 is a schematic structural diagram of a non-doped GaN layer in another embodiment of the present invention;

[0028] Figure 5 This is a flow chart of a method for preparing a light-emitting diode epitaxial wafer in one embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0030] refer to Figures 1 to 3The present invention discloses a light-emitting diode epitaxial wafer, comprising a substrate 1 and a buffer layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6, and a P-type GaN layer 7, sequentially disposed on the substrate 1. The undoped GaN layer 3 sequentially comprises a first GaN layer 31 disposed on the buffer layer 2, a plurality of micro-mirror pillars 32 arrayed on the first GaN layer, and a second GaN layer 33 wrapped around the micro-mirror pillars 32. Each micro-mirror pillar 32 has a periodic structure, with each period comprising a Ta2O5 layer 321 and a SiO2 layer 322 stacked in sequence, with the number of periods ranging from 1 to 20. Since the refractive indices of Ta2O5 and SiO2 are 2.18 and 1.50, respectively, and the refractive index of GaN is 2.5, light emitted from the multi-quantum well layer 5 is totally reflected at the micro-mirror pillars, effectively improving the light reflection efficiency from the epitaxial layer, thereby increasing the external quantum efficiency of the light-emitting diode and improving the light extraction efficiency.

[0031] Among them, the cross-section of the micromirror column 32 is circular, triangular, rectangular, trapezoidal or polygonal (the number of sides ≥ 5), that is, the micromirror column 32 is cylindrical, prism-shaped (triangular prism, quadrangular prism or multi-prism) or prism-shaped as a whole, but is not limited to this. The above various shapes of micromirror columns 32 can effectively improve the light reflection efficiency and improve the light extraction efficiency. Among them, the width of the micromirror column 32 is 0.1~10μm. When its width is greater than 10μm, it will cause the crystal quality of the subsequent epitaxial layer to be poor, reducing the luminous efficiency. When its width is less than 0.1μm, the light reflection efficiency is low. Exemplarily, the width of the micromirror column 32 is 0.5μm, 1μm, 3μm, 5μm, 7μm or 9μm. Preferably it is 0.5~5μm. The height of the micromirror pillars 32 is 0.1 to 6 μm, with exemplary heights of 0.5 μm, 1.2 μm, 2.3 μm, 3.5 μm, or 4.4 μm, but not limited thereto. Preferably, the height is 0.5 to 6 μm. The ratio of the thickness of a single Ta2O5 layer to the thickness of a single SiO2 layer is 1:(1 to 5), with exemplary heights of 1:1, 1:2, 1:3.5, or 1:4, but not limited thereto. The distance between adjacent micromirror pillars 32 is 0.3 to 8 μm. When the spacing is less than 0.3 μm, total light reflection is not achieved, and more dislocations are generated, reducing light extraction efficiency. When the spacing is greater than 8 μm, leveling becomes more difficult, reducing the quality of subsequent layer growth. Exemplary distances between micromirror pillars 32 are 0.5 μm, 1.5 μm, 2 μm, 3.5 μm, 5 μm, 6 μm, or 7.5 μm, but not limited thereto. Preferably, the distance between adjacent micromirror pillars 32 is 0.5 to 5 μm. It should be noted that the micromirror pillars 32 are distributed across the entire surface of the substrate 1 along at least one direction (direction A) of the substrate 1, meaning their length is the same as the length of the substrate 1 along direction A. The width of a micromirror pillar 32 refers to its maximum width in the cross-sectional direction. For example, if the cross-section is triangular, it is the length of the base; if the cross-section is circular, it is the diameter; if the cross-section is rectangular, it is the width of the base in contact with the buffer layer 2, but is not limited thereto. The height of a micromirror pillar 32 refers to the maximum height in the cross-sectional direction. For example, if the cross-section is triangular, it is the height corresponding to the base; if the cross-section is circular, it is the diameter; if the cross-section is rectangular, it is the height of the side perpendicular to the buffer layer 2. The distance between micromirror pillars 32 refers to the distance at their maximum width.

[0032] Preferably, in one embodiment of the present invention, the cross-section of the micromirror pillars 32 is circular. This shape of the micromirror pillars 32 not only improves light reflection efficiency but also better relieves stress, reduces the extension of dislocations and defects into the multi-quantum well layer 5, improves the crystal quality of the epitaxial wafer, and enhances luminous efficiency. Specifically, when a cylindrical structure is employed, the diameter of the micromirror pillars 32 is 0.5 to 5 μm, and the height is 0.5 to 5 μm; the distance between adjacent micromirror pillars 32 is 0.5 to 2 μm.

[0033] The first GaN layer 31 can serve as a template for the second GaN layer to improve the quality of the subsequently grown crystal. The thickness of the first GaN layer 31 is 0.5 to 2 μm, exemplified by, but not limited to, 0.7 μm, 0.9 μm, 1.2 μm, 1.4 μm, 1.6 μm, or 1.8 μm.

[0034] The second GaN layer 33 primarily fills the gaps between the micromirror pillars 32, converting three-dimensional growth into two-dimensional growth. The thickness of the second GaN layer 33 is 0.8 to 5 μm, with exemplary thicknesses of 1 μm, 1.4 μm, 2.1 μm, 3 μm, 3.8 μm, 4 μm, or 4.5 μm being examples, but not limited thereto.

[0035] The substrate 1 may be a sapphire substrate, a silicon substrate, or a silicon carbide substrate, but is not limited thereto.

[0036] The buffer layer 2 may be an AlN layer and / or a GaN layer, but is not limited thereto. Preferably, the buffer layer 2 is an AlN layer. The thickness of the buffer layer 2 is 10 to 50 nm, and is exemplarily 15 nm, 25 nm, 35 nm, or 45 nm, but is not limited thereto.

[0037] The doping element of the N-type GaN layer 4 is Si, but not limited thereto. The doping concentration of the N-type GaN layer 4 is 1×10 19 ~5×10 19 cm -3 The thickness is 0.5 to 5 μm, and is exemplified by 0.8 μm, 1.3 μm, 2.5 μm, 3.7 μm or 4.4 μm, but is not limited thereto.

[0038] The multi-quantum well layer 5 has a periodic structure with 6 to 12 periods. Each period includes a stacked InGaN well layer and an AlGaN barrier layer. The InGaN well layer has a thickness of 2 to 5 nm and an In component ratio of 0.2 to 0.4. The AlGaN barrier layer has a thickness of 5 to 15 nm and an Al component ratio of 0.01 to 0.1.

[0039] The electron blocking layer 6 is an AlGaN layer or an AlInGaN layer, but is not limited thereto. Preferably, in one embodiment of the present invention, the electron blocking layer 6 is an Al α In β The GaN layer has an α value of 0.05 to 0.1, a β value of 0.01 to 0.2, and a thickness of 10 to 40 nm.

[0040] The doping element in the P-type GaN layer 7 is Mg, but not limited thereto. The doping concentration of Mg in the P-type GaN layer 7 is 1×10 19 ~1×10 21 cm-3 The thickness of the P-type GaN layer 7 is 10 to 50 nm.

[0041] Accordingly, reference Figure 5 The present invention also discloses a method for preparing a light-emitting diode epitaxial wafer, which is used to prepare the above-mentioned light-emitting diode epitaxial wafer, and comprises the following steps:

[0042] S1: providing a substrate;

[0043] Preferably, in one embodiment of the present invention, the substrate is loaded into an MOCVD and annealed at 1000-1200° C., 200-600 torr, and a hydrogen atmosphere for 1-10 minutes to remove impurities such as particles and oxides on the substrate surface.

[0044] S2: sequentially growing a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer on the substrate;

[0045] Specifically, S200 includes:

[0046] S21: growing a buffer layer on the substrate;

[0047] Specifically, a GaN layer may be grown by MOCVD as the buffer layer, or an AlN layer may be grown by PVD as the buffer layer, but the present invention is not limited thereto. Preferably, the AlN layer is grown by PVD.

[0048] S22: growing a non-doped GaN layer on the buffer layer;

[0049] Specifically, in one embodiment of the present invention, the growth of the undoped GaN layer includes the following steps:

[0050] S221: growing a first GaN layer;

[0051] Specifically, the first GaN layer can be grown by, but is not limited to, PECVD, MOCVD, or PVD. Preferably, in one embodiment of the present invention, the first GaN layer is grown by MOCVD at a growth temperature of 1000-1500°C and a growth pressure of 50-300 Torr. This high-temperature, low-pressure growth method improves atomic mobility and promotes lateral growth of GaN crystals.

[0052] S222: periodically growing a Ta2O5 layer and a SiO2 layer to obtain a micromirror layer;

[0053] Specifically, the Ta2O5 layer and the SiO2 layer can be grown by PECVD, MOCVD, PVD, etc., but are not limited thereto. Preferably, in one embodiment of the present invention, the Ta2O5 layer and the SiO2 layer are grown by MOCVD. The growth temperature of the Ta2O5 layer is 1000-1100°C, the growth pressure is 50-500 Torr, and TaF5 is used as the Ta source during growth. The growth temperature of the SiO2 layer is 1000-1100°C, and the growth pressure is 50-500 Torr.

[0054] S223: etching the micromirror layer to form a plurality of arrays of micromirror columns;

[0055] Specifically, dry etching (such as ICP, but not limited thereto) or wet etching (such as AZ400K wet etching solution, but not limited thereto) can be used for etching. Preferably, an ICP etching system is used to etch the micromirror layer to form micromirror pillars.

[0056] S224: growing a second GaN layer on the substrate obtained in step S223;

[0057] Specifically, the second GaN layer can be grown by, but is not limited to, PECVD, MOCVD, or PVD. Preferably, in one embodiment of the present invention, the second GaN layer is grown by MOCVD at a growth temperature of 1000-1500°C and a growth pressure of 50-300 Torr. This high-temperature, low-pressure growth method improves atomic mobility and promotes lateral growth of GaN crystals.

[0058] S23: growing an N-type GaN layer on the undoped GaN layer;

[0059] Specifically, the N-type GaN layer is grown in MOCVD at a growth temperature of 1050-1200° C. and a growth pressure of 100-600 Torr.

[0060] S24: growing a multi-quantum well layer on the N-type GaN layer;

[0061] Specifically, InGaN well layers and AlGaN barrier layers are periodically grown in MOCVD to form a multi-quantum well layer. The InGaN well layers are grown at a temperature of 790-810°C and a pressure of 50-300 Torr, while the AlGaN barrier layers are grown at a temperature of 800-900°C and a pressure of 50-300 Torr.

[0062] S25: growing an electron blocking layer on the multi-quantum well layer;

[0063] Specifically, in one embodiment of the present invention, Al is grown in MOCVD. α In βThe GaN layer acts as an electron blocking layer and is grown at a temperature of 900-1000°C and a pressure of 100-300 Torr.

[0064] S26: growing a P-type GaN layer on the electron blocking layer;

[0065] Specifically, the P-type GaN layer is grown in MOCVD at a growth temperature of 900-1050° C. and a growth pressure of 100-600 Torr.

[0066] The present invention will be further described below with specific embodiments:

[0067] Example 1

[0068] This embodiment provides a light emitting diode epitaxial wafer, referring to Figures 1 to 3 It includes a substrate 1 and a buffer layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6 and a P-type GaN layer 7 which are sequentially arranged on the substrate 1.

[0069] The substrate 1 is a sapphire substrate, and the buffer layer 2 is an AlN layer with a thickness of 15 nm. The undoped GaN layer 3 includes a first GaN layer 31 disposed on the buffer layer 2, a plurality of micromirror pillars 32 arrayed on the first GaN layer, and a second GaN layer 33 wrapped around the micromirror pillars 32. The thickness of the first GaN layer 31 is 1.8 μm, and the thickness of the second GaN layer 33 is 1.55 μm. The cross-section of the micromirror pillars 32 is an equilateral triangle with a width of 2.85 μm, a height of 1.2 μm, and a pitch of 3 μm. The micromirror pillars 32 have a periodic structure, with each period comprising a Ta2O5 layer 321 and a SiO2 layer 322 stacked in sequence. The number of periods is 10; the thickness ratio of the Ta2O5 layer 321 to the SiO2 layer 322 is 1:1.5.

[0070] The multi-quantum well layer 5 includes alternating InGaN well layers 51 and AlGaN barrier layers 52, with a stacking period of 10. The InGaN layer 51 is 3.5 nm thick and has an In component ratio of 0.22; the AlGaN barrier layer 52 is 9.8 nm thick and has an Al component ratio of 0.05.

[0071] The electron blocking layer 6 is Al α In β The GaN layer (α = 0.05, β = 0.01) has a thickness of 15 nm. The doping element of the P-type GaN layer 7 is Mg, and the doping concentration is 2×10 20 cm -3 , with a thickness of 15nm.

[0072] The method for preparing a light-emitting diode epitaxial wafer in this embodiment includes the following steps:

[0073] (1) Providing a substrate; loading the substrate into an MOCVD device and annealing it at 1150°C, 400 torr, and a hydrogen atmosphere for 6 minutes.

[0074] (2) growing a buffer layer on the substrate;

[0075] Specifically, the AlN layer is grown by PVD.

[0076] (3) growing a first GaN layer on the buffer layer;

[0077] Specifically, the non-first GaN layer is grown by MOCVD at a growth temperature of 1120° C. and a growth pressure of 150 Torr.

[0078] (4) periodically growing a Ta2O5 layer and a SiO2 layer on the first GaN layer to obtain a micromirror layer;

[0079] Specifically, MOCVD is used to grow the Ta2O5 layer and the SiO2 layer, wherein the growth temperature of the Ta2O5 layer is 1050° C. and the growth pressure is 100 torr; the growth temperature of the SiO2 layer is 1050° C. and the growth pressure is 100 torr.

[0080] (5) Etching the micromirror layer to form multiple arrays of micromirror columns

[0081] Specifically, an ICP etching system is used to etch the micromirror layer.

[0082] (6) growing a second GaN layer on the substrate obtained in step (5);

[0083] Specifically, the non-second GaN layer is grown by MOCVD at a growth temperature of 1120° C. and a growth pressure of 150 Torr.

[0084] (7) Growing an N-type GaN layer on the second GaN layer

[0085] Specifically, the N-type GaN layer is grown in MOCVD at a growth temperature of 1120° C. and a growth pressure of 100 Torr.

[0086] (8) growing a multi-quantum well layer on the N-type GaN layer;

[0087] Specifically, InGaN well layers and AlGaN barrier layers are periodically grown in MOCVD to form a multi-quantum well layer. The InGaN well layers are grown at a temperature of 795°C and a pressure of 200 Torr, while the AlGaN barrier layers are grown at a temperature of 855°C and a pressure of 200 Torr.

[0088] (9) growing an electron blocking layer on the multi-quantum well layer;

[0089] Specifically, MOCVD is used to grow Al α In β The GaN layer, which serves as an electron blocking layer, is grown at a temperature of 965°C and a pressure of 200 Torr.

[0090] (10) growing a P-type GaN layer on the electron blocking layer;

[0091] Specifically, the P-type GaN layer is grown by MOCVD at a growth temperature of 985° C. and a growth pressure of 200 torr.

[0092] Example 2

[0093] This embodiment provides a light emitting diode epitaxial wafer, referring to Figures 1 to 3 It includes a substrate 1 and a buffer layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6 and a P-type GaN layer 7 which are sequentially arranged on the substrate 1.

[0094] The substrate 1 is a sapphire substrate, and the buffer layer 2 is an AlN layer with a thickness of 15 nm. The undoped GaN layer 3 includes a first GaN layer 31 disposed on the buffer layer 2, a plurality of micromirror pillars 32 arrayed on the first GaN layer, and a second GaN layer 33 wrapped around the micromirror pillars 32. The thickness of the first GaN layer 31 is 1.8 μm, and the thickness of the second GaN layer 33 is 1.55 μm. The micromirror pillars 32 have a circular cross-section with a diameter of 2.85 μm, a height of 2.85 μm, and a pitch of 3 μm. The micromirror pillars 32 have a periodic structure, with each period comprising a Ta2O5 layer 321 and a SiO2 layer 322 stacked in sequence. The number of periods is 10; the thickness ratio of the Ta2O5 layer 321 to the SiO2 layer 322 is 1:1.5.

[0095] The multi-quantum well layer 5 includes alternating InGaN well layers 51 and AlGaN barrier layers 52, with a stacking period of 10. The InGaN layer 51 is 3.5 nm thick and has an In component ratio of 0.22; the AlGaN barrier layer 52 is 9.8 nm thick and has an Al component ratio of 0.05.

[0096] The electron blocking layer 6 is Al α In β The GaN layer (α = 0.05, β = 0.01) has a thickness of 15 nm. The doping element of the P-type GaN layer 7 is Mg, and the doping concentration is 2×10 20 cm -3 , with a thickness of 15nm.

[0097] The method for preparing a light-emitting diode epitaxial wafer in this embodiment includes the following steps:

[0098] (1) Providing a substrate; loading the substrate into an MOCVD device and annealing it at 1150°C, 400 torr, and a hydrogen atmosphere for 6 minutes.

[0099] (2) growing a buffer layer on the substrate;

[0100] Specifically, the AlN layer is grown by PVD.

[0101] (3) growing a first GaN layer on the buffer layer;

[0102] Specifically, the non-first GaN layer is grown by MOCVD at a growth temperature of 1120° C. and a growth pressure of 150 Torr.

[0103] (4) periodically growing a Ta2O5 layer and a SiO2 layer on the first GaN layer to obtain a micromirror layer;

[0104] Specifically, MOCVD is used to grow the Ta2O5 layer and the SiO2 layer, wherein the growth temperature of the Ta2O5 layer is 1050° C. and the growth pressure is 100 torr; the growth temperature of the SiO2 layer is 1050° C. and the growth pressure is 100 torr.

[0105] (5) Etching the micromirror layer to form multiple arrays of micromirror columns

[0106] Specifically, an ICP etching system is used to etch the micromirror layer.

[0107] (6) growing a second GaN layer on the substrate obtained in step (5);

[0108] Specifically, the non-second GaN layer is grown by MOCVD at a growth temperature of 1120° C. and a growth pressure of 150 Torr.

[0109] (7) Growing an N-type GaN layer on the second GaN layer

[0110] Specifically, the N-type GaN layer is grown in MOCVD at a growth temperature of 1120° C. and a growth pressure of 100 Torr.

[0111] (8) growing a multi-quantum well layer on the N-type GaN layer;

[0112] Specifically, InGaN well layers and AlGaN barrier layers are periodically grown in MOCVD to form a multi-quantum well layer. The InGaN well layers are grown at a temperature of 795°C and a pressure of 200 Torr, while the AlGaN barrier layers are grown at a temperature of 855°C and a pressure of 200 Torr.

[0113] (9) growing an electron blocking layer on the multi-quantum well layer;

[0114] Specifically, MOCVD is used to grow Al α In β The GaN layer, which serves as an electron blocking layer, is grown at a temperature of 965°C and a pressure of 200 Torr.

[0115] (10) growing a P-type GaN layer on the electron blocking layer;

[0116] Specifically, the P-type GaN layer is grown by MOCVD at a growth temperature of 985° C. and a growth pressure of 200 torr.

[0117] Example 3

[0118] This embodiment provides a light emitting diode epitaxial wafer, referring to Figures 1 to 3 It includes a substrate 1 and a buffer layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6 and a P-type GaN layer 7 which are sequentially arranged on the substrate 1.

[0119] The substrate 1 is a sapphire substrate, and the buffer layer 2 is an AlN layer with a thickness of 15 nm. The undoped GaN layer 3 includes a first GaN layer 31 provided on the buffer layer 2, a plurality of micromirror pillars 32 arrayed on the first GaN layer, and a second GaN layer 33 wrapped around the micromirror pillars 32. The thickness of the first GaN layer 31 is 1.8 μm, and the thickness of the second GaN layer 33 is 1.55 μm. The micromirror pillars 32 have a circular cross-section with a diameter of 2 μm, a height of 2 μm, and a pitch of 1.5 μm. The micromirror pillars 32 have a periodic structure, with each period comprising a Ta2O5 layer 321 and a SiO2 layer 322 stacked in sequence. The number of periods is 10; the thickness ratio of the Ta2O5 layer 321 to the SiO2 layer 322 is 1:1.5.

[0120] The multi-quantum well layer 5 includes alternating InGaN well layers 51 and AlGaN barrier layers 52, with a stacking period of 10. The InGaN layer 51 is 3.5 nm thick and has an In component ratio of 0.22; the AlGaN barrier layer 52 is 9.8 nm thick and has an Al component ratio of 0.05.

[0121] The electron blocking layer 6 is Al α In β The GaN layer (α = 0.05, β = 0.01) has a thickness of 15 nm. The doping element of the P-type GaN layer 7 is Mg, and the doping concentration is 2×10 20 cm -3 , with a thickness of 15nm.

[0122] The method for preparing a light-emitting diode epitaxial wafer in this embodiment includes the following steps:

[0123] (1) Providing a substrate; loading the substrate into an MOCVD device and annealing it at 1150°C, 400 torr, and a hydrogen atmosphere for 6 minutes.

[0124] (2) growing a buffer layer on the substrate;

[0125] Specifically, the AlN layer is grown by PVD.

[0126] (3) growing a first GaN layer on the buffer layer;

[0127] Specifically, the non-first GaN layer is grown by MOCVD at a growth temperature of 1120° C. and a growth pressure of 150 Torr.

[0128] (4) periodically growing a Ta2O5 layer and a SiO2 layer on the first GaN layer to obtain a micromirror layer;

[0129] Specifically, MOCVD is used to grow the Ta2O5 layer and the SiO2 layer, wherein the growth temperature of the Ta2O5 layer is 1050° C. and the growth pressure is 100 torr; the growth temperature of the SiO2 layer is 1050° C. and the growth pressure is 100 torr.

[0130] (5) Etching the micromirror layer to form multiple arrays of micromirror columns

[0131] Specifically, an ICP etching system is used to etch the micromirror layer.

[0132] (6) growing a second GaN layer on the substrate obtained in step (5);

[0133] Specifically, the non-second GaN layer is grown by MOCVD at a growth temperature of 1120° C. and a growth pressure of 150 Torr.

[0134] (7) Growing an N-type GaN layer on the second GaN layer

[0135] Specifically, the N-type GaN layer is grown in MOCVD at a growth temperature of 1120° C. and a growth pressure of 100 Torr.

[0136] (8) growing a multi-quantum well layer on the N-type GaN layer;

[0137] Specifically, InGaN well layers and AlGaN barrier layers are periodically grown in MOCVD to form a multi-quantum well layer. The InGaN well layers are grown at a temperature of 795°C and a pressure of 200 Torr, while the AlGaN barrier layers are grown at a temperature of 855°C and a pressure of 200 Torr.

[0138] (9) growing an electron blocking layer on the multi-quantum well layer;

[0139] Specifically, MOCVD is used to grow Al α In β The GaN layer, which serves as an electron blocking layer, is grown at a temperature of 965°C and a pressure of 200 Torr.

[0140] (10) growing a P-type GaN layer on the electron blocking layer;

[0141] Specifically, the P-type GaN layer is grown by MOCVD at a growth temperature of 985° C. and a growth pressure of 200 torr.

[0142] Comparative Example 1

[0143] This comparative example provides a light-emitting diode epitaxial wafer. The difference between this embodiment and Example 1 is that no micromirror pillars are provided in the undoped GaN layer. Accordingly, the preparation method does not include the step of preparing the micromirror pillars (steps (4) to (5)). The remaining steps are the same as those in Example 1.

[0144] Comparative Example 2

[0145] This comparative example provides a light-emitting diode epitaxial wafer. The difference between this embodiment and the first embodiment is that the first GaN layer is not provided in the undoped GaN layer. Accordingly, the preparation method does not include the step of preparing this layer (step (3)). All other steps are the same as those in the first embodiment.

[0146] Comparative Example 3

[0147] This comparative example provides a light-emitting diode epitaxial wafer. The difference between this embodiment and the first embodiment is that the second GaN layer is not provided in the undoped GaN layer. Accordingly, the preparation method does not include the step of preparing this layer (step (6)). All other steps are the same as those in the first embodiment.

[0148] Comparative Example 4

[0149] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that after the micromirror layer is prepared, no etching treatment is performed on it (ie, step (5) is not included), and the rest is the same as Example 1.

[0150] Comparative Example 5

[0151] This comparative example provides a light emitting diode epitaxial wafer, which differs from Example 1 in that the width of the micromirror column is 12 μm, the height is 0.3 μm, and the distance between adjacent micromirror columns is 10 μm.

[0152] The light-emitting diodes obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were tested. The specific testing method was as follows: 100 10mil*24mil chips were prepared from the epitaxial wafers and their luminous brightness was tested; and the light efficiency improvement rate was calculated based on the comparative examples.

[0153] The specific results are as follows:

[0154] Light efficiency improvement rate (%) Example 1 1.88±0.12 Example 2 1.91±0.23 Example 3 2.35±0.14 Comparative Example 1 - Comparative Example 2 0.35±0.24 Comparative Example 3 0.15±0.28 Comparative Example 4 0.12±0.33 Comparative Example 5 0.44±0.26

[0155] As can be seen from the table, when the traditional undoped GaN layer is replaced with the undoped GaN layer structure of the present invention, the luminous efficiency is significantly improved. In addition, a comparison of Example 1 with Comparative Examples 1 to 5 shows that when the structure of the undoped GaN layer in the present application is changed, it is difficult to effectively improve the luminous efficiency.

[0156] The above is a preferred embodiment of the invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A light-emitting diode epitaxial wafer comprising a substrate and a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially disposed on the substrate; characterized in that: The undoped GaN layer sequentially includes a first GaN layer disposed on the buffer layer, a plurality of micro-mirror pillars arrayed on the first GaN layer, and a second GaN layer wrapped around the micro-mirror pillars; Among them, each micromirror column has a periodic structure, each period includes Ta2O5 layers and SiO2 layers stacked in sequence, and the number of periods is 1 to 20; the ratio of the thickness of a single Ta2O5 layer to the thickness of a single SiO2 layer is 1:(1 to 5); the width of each micromirror column is 0.1 to 10 μm, the height is 0.1 to 6 μm, and the distance between adjacent micromirror columns is 0.3 to 8 μm.

2. The light emitting diode epitaxial wafer according to claim 1, wherein: The thickness of the first GaN layer is 0.5 to 2 μm, and the thickness of the second GaN layer is 0.8 to 5 μm.

3. The light emitting diode epitaxial wafer according to claim 1, wherein: The cross section of the micromirror column is triangular, trapezoidal, rectangular or circular.

4. The light emitting diode epitaxial wafer according to claim 1 or 3, wherein: The cross section of the micromirror column is circular.

5. The light emitting diode epitaxial wafer according to claim 4, wherein: The diameter of the micro mirror column is 0.5-5 μm, and the height is 0.5-5 μm; the distance between adjacent micro mirror columns is 0.5-2 μm.

6. A method for preparing a light emitting diode epitaxial wafer, for preparing the light emitting diode epitaxial wafer according to any one of claims 1 to 5, characterized in that: include: A substrate is provided, and a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer are sequentially grown on the substrate; the undoped GaN layer sequentially includes a first GaN layer provided on the buffer layer, a plurality of micro-mirror pillars arrayed on the first GaN layer, and a second GaN layer wrapped around the micro-mirror pillars; Each micromirror column has a periodic structure, and each period includes a Ta2O5 layer and a SiO2 layer, with the number of periods ranging from 1 to 20. The width of each micromirror column is 0.1 to 10 μm, the height is 0.1 to 6 μm, and the distance between adjacent micromirror columns is 0.3 to 8 μm. The preparation method of the micro mirror column is: periodically growing a Ta2O5 layer and a SiO2 layer to obtain a micro mirror layer, and etching to form a plurality of arrays of micro mirror columns.

7. The method for preparing a light emitting diode epitaxial wafer according to claim 6, wherein: The growth temperature of the first GaN layer is 1000-1500° C., and the growth pressure is 50-300 Torr; The growth temperature of the Ta2O5 layer is 1000-1000°C, and the growth pressure is 50-500 torr; The growth temperature of the SiO2 layer is 1000-1100°C, and the growth pressure is 50-500 torr; The growth temperature of the second GaN layer is 1000-1500° C., and the growth pressure is 50-300 Torr.

8. A light emitting diode, characterized in that: It comprises the light emitting diode epitaxial wafer according to any one of claims 1 to 5.

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