Epitaxial structure of multiband LED and preparation method thereof

Abstract

The invention relates to the technical field of light emitting diodes, and discloses a multiband LED epitaxial structure and a preparation method thereof, the epitaxial structure comprises a substrate, a buffer layer, an N-type semiconductor layer, a low temperature stress release layer, a multi-quantum well light emitting layer, an electron blocking layer and a P-type semiconductor layer, the multi-quantum well light-emitting layer comprises a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer and a fourth multi-quantum well layer which are sequentially stacked, and each multi-quantum well layer comprises an InGaN quantum well layer and a variable barrier height regulation barrier layer which are periodically and alternately stacked. The variable barrier height regulation barrier layer comprises five sub-layers which are sequentially stacked on the InGaN quantum well layer, lambda 1 > lambda 2 > lambda 3, and lambda 3 = lambda 4. The healthy full-spectrum white light LED light source with the high color rendering index can be generated, the short-wave blue light is small in proportion, damage to human eye omentum cells is small, and the light emitting efficiency is high.

Description

Technical Field

[0001] The present invention relates to the technical field of light emitting diodes, and in particular to an epitaxial structure of a multi-band LED and a preparation method thereof. Background Art

[0002] LED light sources offer advantages such as compact size, long life, and high efficiency, enabling continuous operation for up to 100,000 hours. They have become mainstream in the lighting industry. As the application of LED light sources continues to expand, higher requirements are being placed on their luminous properties. Expanding the spectral range of LED light sources has become a key area of ​​improvement. These products are referred to in the industry as full-spectrum white light LED light sources. Full spectrum refers to a spectrum that includes ultraviolet, visible, and infrared light, with a red, green, and blue ratio within the visible portion similar to sunlight, resulting in a color rendering index close to 100. The spectrum of sunlight can be called full spectrum.

[0003] White LED devices currently on the market typically use a fluorescent adhesive coated on a blue LED chip to produce white light. However, within the spectral curve of a full-spectrum white LED source, the blue light band exhibits significant fluctuations and poor stability. Furthermore, as early as 1966, Nell et al. discovered that exposure to blue light can damage retinal cells, leading to decreased or even loss of vision. Short-wavelength blue light, with a wavelength between 400nm and 450nm, is particularly harmful to the retina. At the 2010 International Association of Optics Annual Meeting, leading optical experts worldwide unanimously stated that short-wavelength blue light has extremely high energy and can penetrate the lens directly to the retina. Exposure to blue light on the retina generates free radicals, which can cause the death of retinal pigment epithelial cells. This cell death deprives light-sensitive cells of nutrients, leading to irreversible vision loss. In response to the shortcomings of current full-spectrum white light LED light sources, further optimization and research have been conducted on the structure and process of blue light LED chips, in order to use multi-band LED chips to stimulate the red and green mixed phosphor layers to produce a full-spectrum white light LED light source that is less damaging to the human retinal cells, healthier, has a high color rendering index and is closer to the sunlight spectrum. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an epitaxial structure of a multi-band LED and a preparation method thereof, wherein a multi-band LED chip is used to excite a mixed phosphor layer to produce a full-spectrum white light LED light source, in which the short-wave blue light accounts for a small proportion and causes little damage to the retinal cells of the human eye, thereby realizing a healthy full-spectrum white light LED light source with a high color rendering index.

[0005] In order to solve the above technical problems, the first aspect of the present invention provides an epitaxial structure of a multi-band LED, comprising a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, an electron blocking layer and a P-type semiconductor layer stacked in sequence, wherein:

[0006] The multi-quantum well light-emitting layer includes a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer, and a fourth final quantum well layer stacked in sequence; the first multi-quantum well layer, the second multi-quantum well layer, the third multi-quantum well layer, and the fourth final quantum well layer all include periodically alternately stacked InGaN quantum well layers and variable barrier height control barrier layers, and the variable barrier height control barrier layer includes five sublayers stacked in sequence on the InGaN quantum well layer: a first variable barrier control barrier layer sublayer, a second variable barrier control barrier layer sublayer, a third variable barrier control barrier layer sublayer, a fourth variable barrier control barrier layer sublayer, and a fifth variable barrier control barrier layer sublayer;

[0007] The emission wavelength of the first multi-quantum well layer is λ1, the emission wavelength of the second multi-quantum well layer is λ2, the emission wavelength of the third multi-quantum well layer is λ3, and the emission wavelength of the fourth final quantum well layer is λ4, λ1>λ2>λ3, λ3=λ4.

[0008] As an improvement to the above solution, the energy band barrier height of the first multi-quantum well layer is φ1, the energy band barrier height of the second multi-quantum well layer is φ2, the energy band barrier height of the third multi-quantum well layer is φ3, and the energy band barrier height of the fourth final quantum well layer is φ4, φ1>φ4, φ4>φ2, φ2>φ3;

[0009] The λ1 is 460nm-480nm, λ2 is 445nm-460nm, λ3 is 430nm-445nm, and λ4 is 430nm-445nm.

[0010] As an improvement of the above solution, the first variable barrier regulating barrier layer sublayer is a GaN layer, and the first variable barrier regulating barrier layer sublayer is N-type doped or P-type doped; the second variable barrier regulating barrier layer sublayer is Al x Ga 1-x N layer, the second variable barrier regulating barrier layer sublayer is not intentionally doped; the third variable barrier regulating barrier layer sublayer is Al w In z Ga 1-w-z N layer, the third variable barrier regulating barrier layer sublayer is N-type doped or P-type doped; the fourth variable barrier regulating barrier layer sublayer is Al y Ga 1-yN layer, the fourth variable barrier regulation barrier layer sublayer is not intentionally doped; the fifth variable barrier regulation barrier layer sublayer is a GaN layer, and the fifth variable barrier regulation barrier layer sublayer is N-type doped or P-type doped.

[0011] As an improvement of the above solution, the growth thickness of the first variable barrier regulating barrier layer sublayer is 0.6nm-6nm, the growth temperature of the first variable barrier regulating barrier layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr;

[0012] The second variable barrier regulates the growth thickness of the barrier layer sublayer to be 0.2nm-2nm, the growth temperature of the second variable barrier regulates the growth of the barrier layer sublayer to be 825℃-938℃, and the growth pressure to be 50torr-360torr;

[0013] The thickness of the third variable barrier regulating barrier layer sublayer is 0.5nm-6nm, the growth temperature of the third variable barrier regulating barrier layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr;

[0014] The growth thickness of the fourth variable barrier regulating barrier layer sublayer is 0.2nm-2nm, the growth temperature of the fourth variable barrier regulating barrier layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr;

[0015] The growth thickness of the fifth variable barrier regulating barrier layer sublayer is 0.6nm-6nm, the growth temperature of the fifth variable barrier regulating barrier layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr.

[0016] As an improvement to the above solution, the InGaN quantum well layer in the fourth final quantum well layer is an InGaN layer that has undergone surface roughening annealing treatment, and the surface roughening annealing treatment includes: after the growth of the InGaN layer is completed, intermittently and cyclically introducing a mixed gas of N2 and H2 into the reaction chamber and stabilizing it for 5s-50s, the temperature of the surface roughening annealing treatment is 820°C-1080°C, the pressure is 50torr-360torr, and the mixing ratio of N2 and H2 is 1:(0.2-3);

[0017] The third variable barrier control barrier layer sublayer in the fourth final quantum well layer is an AlInGaN layer that has undergone surface roughening annealing treatment. The surface roughening annealing treatment includes: after the growth of the AlInGaN layer is completed, intermittently and cyclically introducing a mixed gas of N2 and H2 into the reaction chamber and stabilizing it for 10s-100s. The temperature of the surface roughening annealing treatment is 820℃-1080℃, the pressure is 50torr-360torr, and the mixing ratio of N2 and H2 is 1:(0.5-6).

[0018] As an improvement to the above solution, the first multi-quantum well layer is a superlattice structure formed by periodically alternatingly growing a first InGaN quantum well layer and a first variable barrier height control barrier layer, with a period number of 1-5; wherein the first variable barrier height control barrier layer includes a first GaN sublayer, an Al sublayer, and a GaN sublayer sequentially stacked on the first InGaN quantum well layer. x1 Ga 1-x1 N sublayer, Al w1 In z1 Ga 1-w1-z1 N sublayer, Al y1 Ga 1-y1 N sublayer, second GaN sublayer;

[0019] The second multi-quantum well layer is a superlattice structure formed by a second InGaN quantum well layer and a second variable barrier height control barrier layer grown periodically and alternately, with a period number of 2-6; wherein the second variable barrier height control barrier layer includes a third GaN sublayer, an Al sublayer, and a plurality of other sublayers sequentially stacked on the second InGaN quantum well layer. x2 Ga 1-x2 N sublayer, Al w2 In z2 Ga 1-w2-z2 N sublayer, Al y2 Ga 1-y2 N sublayer, fourth GaN sublayer;

[0020] The third multi-quantum well layer is a superlattice structure formed by a third InGaN quantum well layer and a third variable barrier height control barrier layer grown periodically and alternately, with a period number of 2-5; wherein the third variable barrier height control barrier layer includes a fifth GaN sublayer, an Al sublayer, and a plurality of other sublayers sequentially stacked on the third InGaN quantum well layer. x3 Ga 1-x3 N sublayer, Al w3 In z3 Ga 1-w3-z3 N sublayer, Al y3 Ga 1-y3 N sublayer, sixth GaN sublayer;

[0021] The fourth final quantum well layer includes a fourth InGaN quantum well layer and a fourth variable barrier height control barrier layer stacked in sequence; wherein the fourth variable barrier height control barrier layer includes a seventh GaN sublayer, an Al sublayer, and a seventh GaN sublayer stacked in sequence on the fourth InGaN quantum well layer. x4 Ga 1-x4 N sublayer, Al w4 In z4 Ga 1-w4-z4 N sublayer, Al y4 Ga 1-y4 N sub-layer, and eighth GaN sub-layer.

[0022] As an improvement to the above solution, the first GaN sublayer is N-type doped, and the N-type doping concentration is 1.8×10 17 / cm 3 ~8.7×10 17 / cm 3 ; The Al w1 In z1 Ga 1-w1-z1 The N sublayer is N-type doped, and the doping concentration of N-type doping is 1.3×10 17 / cm 3 ~6.8×10 17 / cm 3 The second GaN sublayer is N-type doped, and the doping concentration of N-type doping is 1.8×10 17 / cm 3 ~8.7×10 17 / cm 3 ;

[0023] The third GaN sublayer is N-type doped, and the doping concentration of the N-type doping is 1.5×10 17 / cm 3 ~7.6×10 17 / cm 3 ; The Al w2 In z2 Ga 1-w2-z2 The N sublayer is N-type doped, and the doping concentration of N-type doping is 1.1×10 17 / cm 3 ~6.0×10 17 / cm 3 The fourth GaN sublayer is N-type doped, and the doping concentration of N-type doping is 1.5×10 17 / cm 3 ~7.6×10 17 / cm 3 ;

[0024] The fifth GaN sublayer is N-type doped, and the doping concentration of the N-type doping is 1.2×10 17 / cm 3 ~6.5×10 17 / cm 3 ; The Al w3 In z3 Ga 1-w3-z3 The N sublayer is N-type doped, and the doping concentration of N-type doping is 0.8×10 17 / cm 3 ~5.2×10 17 / cm 3The sixth GaN sublayer is N-type doped, and the doping concentration of N-type doping is 1.2×10 17 / cm 3 ~6.5×10 17 / cm 3 ;

[0025] The seventh GaN sublayer is P-type doped, and the doping concentration of the P-type doping is 1.8×10 18 / cm 3 ~5.6×10 19 / cm 3 ; The Al w4 In z4 Ga 1-w4-z4 The N sublayer is doped with P-type, and the doping concentration of N-type is 3.6×10 18 / cm 3 ~7.8×10 19 / cm 3 The eighth GaN sublayer is P-type doped and the N-type doping concentration is 1.8×10 18 / cm 3 ~5.6×10 19 / cm 3 .

[0026] As an improvement to the above solution, x3<x2<x4<x1, y3<y2<y4<y1;

[0027] w1>w2, w2=w3=w4, z4>z3, z3>z1, z3=z2;

[0028] 0.03≤x1≤0.18, 0.03≤y1≤0.18; 0.01≤x2≤0.12, 0.01≤y2≤0.12; 0≤x3≤0.10, 0≤y3≤0.10; 0.02≤x4≤0.15, 0.02≤y4≤0.15;

[0029] 0.03≤w1≤0.36, 0≤z1≤0.03; 0≤w2≤0.10, 0≤z2≤0.05; 0≤w3≤0.10, 0≤z3≤0.05; 0≤w4≤0.10, 0.03≤z4≤0.12.

[0030] As an improvement to the above solution, the first InGaN quantum well layer, the second InGaN quantum well layer, the third InGaN quantum well layer, and the fourth InGaN quantum well layer are all unintentionally doped InGaN single-layer structures or InGaN multi-layer structures;

[0031] The proportion of In component in the first InGaN quantum well layer is 0.16-0.19, and the growth thickness is 2.0nm-4.7nm; the proportion of In component in the second InGaN quantum well layer is 0.13-0.16, and the growth thickness is 2.0nm-4.7nm; the proportion of In component in the third InGaN quantum well layer is 0.10-0.13, and the growth thickness is 2.0nm-4.7nm; the proportion of In component in the fourth InGaN quantum well layer is 0.10-0.13, and the growth thickness is 2.0nm-4.7nm.

[0032] The second aspect of the present invention further provides a method for preparing the epitaxial structure of the multi-band LED, comprising:

[0033] (1) providing a substrate;

[0034] (2) sequentially growing a buffer layer on the substrate;

[0035] (3) growing an N-type semiconductor layer on the buffer layer;

[0036] (4) growing a low-temperature stress release layer on the N-type semiconductor layer;

[0037] (5) growing a multi-quantum well light-emitting layer on the low-temperature stress release layer;

[0038] (6) growing an electron blocking layer on the multi-quantum well light-emitting layer;

[0039] (7) growing a P-type semiconductor layer on the electron blocking layer;

[0040] The multi-quantum well light-emitting layer includes a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer, and a fourth final quantum well layer stacked in sequence; the first multi-quantum well layer, the second multi-quantum well layer, the third multi-quantum well layer, and the fourth final quantum well layer all include periodically alternately stacked InGaN quantum well layers and variable barrier height control barrier layers, and the variable barrier height control barrier layer includes five sublayers stacked in sequence on the InGaN quantum well layer: a first variable barrier control barrier layer sublayer, a second variable barrier control barrier layer sublayer, a third variable barrier control barrier layer sublayer, a fourth variable barrier control barrier layer sublayer, and a fifth variable barrier control barrier layer sublayer;

[0041] λ1>λ2>λ3, λ3=λ4.

[0042] The implementation of the present invention has the following beneficial effects:

[0043] The epitaxial structure of the multi-band LED chip in the present application is used to form a multi-band LED chip in the LED chip, which produces a full-spectrum white light LED light source by exciting the red and green mixed phosphor layer with three-band light sources. Compared with the blue light LED chip with only one band, its short-wave blue light below 450nm accounts for a small proportion, which causes less damage to the human retinal cells. Moreover, its excitation light source has three bands, and the full-spectrum white light generated is closer to the sunlight spectrum, thereby realizing a healthy full-spectrum white light LED light source with a high color rendering index.

[0044] Furthermore, the emission wavelength of the first multi-quantum well layer is λ1, the emission wavelength of the second multi-quantum well layer is λ2, the emission wavelength of the third multi-quantum well layer is λ3, and the emission wavelength of the fourth final quantum well layer is λ4, where λ1>λ2>λ3, and λ3=λ4. The resulting epitaxial structure of the multi-band LED chip makes it easier to obtain high-quality multi-band multi-quantum well light-emitting layers, thereby improving the radiative recombination efficiency of the active region and further enhancing the luminous efficiency of the multi-band LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 : Schematic diagram of the epitaxial structure of a multi-band LED in the present invention;

[0046] Figure 2 : A schematic structural diagram of a multi-quantum well light-emitting layer in the present invention;

[0047] Figure 3 : A schematic structural diagram of the first variable barrier height control barrier layer in the present invention;

[0048] Figure 4 : A schematic structural diagram of the second variable barrier height control barrier layer in the present invention;

[0049] Figure 5 : A schematic structural diagram of the third variable barrier height control barrier layer in the present invention;

[0050] Figure 6 : Schematic diagram of the structure of the fourth variable barrier height control barrier layer in the present invention.

[0051] Reference numerals:

[0052] 100-substrate; 200-buffer layer; 300-N-type semiconductor layer; 400-low-temperature stress release layer; 500-multi-quantum well light-emitting layer; 510-first multi-quantum well layer; 511-first InGaN quantum well layer; 512-first variable barrier height control layer; 5121-first GaN sublayer; 5122-Al x1 Ga 1-x1 N sublayer; 5123-Al w1 In z1 Ga 1-w1-z1N sublayer; 5124-Al y1 Ga 1-y1 N sublayer; 5125-second GaN sublayer; 520-second multi-quantum well layer; 521-second InGaN quantum well layer; 522-second variable barrier height control barrier layer; 5221-third GaN sublayer; 5222-Al x2 Ga 1-x2 N sublayer; 5223-Al w2 In z2 Ga 1-w2-z2 N sublayer; 5224-Al y2 Ga 1-y2 N sublayer; 5225-fourth GaN sublayer; 530-third multi-quantum well layer; 531-third InGaN quantum well layer; 532-third variable barrier height control barrier layer; 5321-fifth GaN sublayer; 5322-Al x3 Ga 1-x3 N sublayer; 5323-Al w3 In z3 Ga 1-w3- z3 N sublayer; 5324-Al y3 Ga 1-y3 N sublayer; 5325-sixth GaN sublayer; 540-fourth final quantum well layer; 541-fourth InGaN quantum well layer; 542-fourth variable barrier height control barrier layer; 5421-seventh GaN sublayer; 5422-Al x4 Ga 1-x4 N sublayer; 5423-Al w4 In z4 Ga 1-w4-z4 N sublayer; 5424-Al y4 Ga 1-y4 N sublayer; 5245-eighth GaN sublayer; 600-electron blocking layer; 700-P-type semiconductor layer. DETAILED DESCRIPTION

[0053] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail with reference to specific embodiments below.

[0054] In the description of this application, it is necessary to understand that the orientations or positional relationships indicated by “upper”, “lower”, “top”, “bottom”, “inside”, “outside”, etc. are all based on the orientations or positional relationships shown in the accompanying drawings. The purpose is only to facilitate the description of the present invention and simplify the description. It does not indicate or imply that the referred parts must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0055] In order to solve the above problems, the first aspect of the present invention provides an epitaxial structure of a multi-band LED, see Figure 1 , including a substrate 100, a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress release layer 400, a multi-quantum well light-emitting layer 500, an electron blocking layer 600 and a P-type semiconductor layer 700 stacked in sequence, wherein the multi-quantum well light-emitting layer 500 includes a first multi-quantum well layer 510, a second multi-quantum well layer 520, a third multi-quantum well layer 530, and a fourth final quantum well layer 540 stacked in sequence, with the number of periods being 6-19.

[0056] The emission wavelength of the first multi-quantum well layer 510 is λ1, the emission wavelength of the second multi-quantum well layer 520 is λ2, the emission wavelength of the third multi-quantum well layer 530 is λ3, and the emission wavelength of the fourth final quantum well layer 540 is λ4, where λ1>λ2>λ3 and λ3=λ4. Optionally, λ1 is 460nm-480nm, λ2 is 445nm-460nm, λ3 is 430nm-445nm, and λ4 is 430nm-445nm, so that the first multi-quantum well layer 510 is a long-wave blue multi-quantum well layer, the second multi-quantum well layer 520 is a medium-wave blue multi-quantum well layer, the third multi-quantum well layer 530 is a short-wave blue multi-quantum well layer, and the fourth final quantum well layer 540 is a short-wave blue final quantum well layer.

[0057] The epitaxial structure of the multi-band LED chip in the present application is used to form a multi-band LED chip in the LED chip, which produces a full-spectrum white light LED light source by exciting the red and green mixed phosphor layer with three-band light sources. Compared with the blue light LED chip with only one band, its short-wave blue light below 450nm accounts for a small proportion, which causes less damage to the human retinal cells. Moreover, its excitation light source has three bands, and the full-spectrum white light generated is closer to the sunlight spectrum, thereby realizing a healthy full-spectrum white light LED light source with a high color rendering index.

[0058] Furthermore, the energy band barrier height of the first multi-quantum well layer 510 is φ1, the energy band barrier height of the second multi-quantum well layer 520 is φ2, the energy band barrier height of the third multi-quantum well layer 530 is φ3, and the energy band barrier height of the fourth final quantum well layer 540 is φ4, φ1>φ4, φ4>φ2, φ2>φ3, forming a first high-barrier long-wave blue light multi-quantum well layer, a second low-barrier medium-wave blue light multi-quantum well layer, a third low-barrier short-wave blue light multi-quantum well layer, and a fourth medium-barrier short-wave blue light final quantum well layer stacked in sequence. The multi-quantum well light-emitting layer 500 is usually prepared by low-temperature deposition growth at 650℃-935℃. As the deposition thickness increases, the crystallization quality and surface flatness of the deposited epitaxial thin film material will become worse and worse. The longer the emission wavelength, the higher the In component of the InGaN material in the quantum well layer, and the more defects are caused by the mismatch stress caused by the well-barrier mismatch. In addition, the growth temperature of the InGaN material with a high In component is lower, and the defects of the grown epitaxial film are further increased. Therefore, the growth order of the multi-band multi-quantum well light-emitting layer 500 is designed to preferably deposit and grow long-wave quantum wells first and then deposit and grow short-wave quantum wells. The epitaxial structure of the prepared multi-band LED chip makes it easier to obtain a high-quality multi-band multi-quantum well light-emitting layer 500, thereby improving the radiation recombination efficiency of the active area and further improving the luminous efficiency of the multi-band LED chip.

[0059] Specifically, the first multi-quantum well layer 510, the second multi-quantum well layer 520, the third multi-quantum well layer 530, and the fourth final quantum well layer 540 all include periodically alternating stacked InGaN quantum well layers and variable barrier height control barrier layers, and the variable barrier height control barrier layer includes five sublayers stacked in sequence on the InGaN quantum well layer: a first variable barrier control barrier layer sublayer, a second variable barrier control barrier layer sublayer, a third variable barrier control barrier layer sublayer, a fourth variable barrier control barrier layer sublayer, and a fifth variable barrier control barrier layer sublayer.

[0060] The first variable barrier regulating barrier layer sublayer is a GaN layer, and the first variable barrier regulating barrier layer sublayer is N-type doped or P-type doped; the second variable barrier regulating barrier layer sublayer is Al x Ga 1-x N layer, the second variable barrier regulating barrier layer sublayer is not intentionally doped; the third variable barrier regulating barrier layer sublayer is Al w In z Ga 1-w-z N layer, the third variable barrier regulating barrier layer sublayer is N-type doped or P-type doped; the fourth variable barrier regulating barrier layer sublayer is Al y Ga 1-yN layer, the fourth variable barrier regulation barrier layer sublayer is not intentionally doped; the fifth variable barrier regulation barrier layer sublayer is a GaN layer, and the fifth variable barrier regulation barrier layer sublayer is N-type doped or P-type doped.

[0061] More preferably, in the first multi-quantum well layer 510, the second multi-quantum well layer 520, and the third multi-quantum well layer 530, the first variable barrier control barrier layer sublayer, the third variable barrier control barrier layer sublayer, and the fifth variable barrier control barrier layer sublayer are N-type doped; in the fourth final quantum well layer 540, the first variable barrier control barrier layer sublayer, the third variable barrier control barrier layer sublayer, and the fifth variable barrier control barrier layer sublayer are P-type doped, which can respectively provide part of the electrons and holes to the light-emitting quantum well region to participate in radiative recombination and luminescence, so as to improve the matching degree of the electron-hole concentration in the light-emitting quantum well region, thereby improving the luminous efficiency of the multi-band LED chip. Exemplarily, the N-type doping includes but is not limited to Si doping, and the P-type doping includes but is not limited to Mg doping.

[0062] Optionally, the growth thickness of the first variable barrier regulating barrier layer sublayer is 0.6nm-6nm; the growth thickness of the second variable barrier regulating barrier layer sublayer is 0.2nm-2nm; the growth thickness of the third variable barrier regulating barrier layer sublayer is 0.5nm-6nm; the growth thickness of the fourth variable barrier regulating barrier layer sublayer is 0.2nm-2nm; and the growth thickness of the fifth variable barrier regulating barrier layer sublayer is 0.6nm-6nm.

[0063] Furthermore, the Al in the third multi-quantum well layer 530 x Ga 1-x The Al content of the N layer is less than that of the Al in the second multi-quantum well layer 520. x Ga 1-x The Al component ratio of the N layer, the Al in the second multi-quantum well layer 520 x Ga 1- x The Al content of the N layer is less than that of the Al in the fourth final quantum well layer 540. x Ga 1-x The Al component ratio of the N layer, the Al in the fourth final quantum well layer 540 x Ga 1-x The Al content of the N layer is less than that of the Al in the first multi-quantum well layer 510. x Ga 1-x The Al component ratio of the N layer, the Al in the third multi-quantum well layer 530 y Ga 1-y The Al content of the N layer is less than that of the Al in the second multi-quantum well layer 520. y Ga 1-yThe Al component ratio of the N layer, the Al in the second multi-quantum well layer 520 y Ga 1-y The Al content of the N layer is less than that of the Al in the fourth final quantum well layer 540. y Ga 1-y The Al component ratio of the N layer, the Al in the fourth final quantum well layer 540 y Ga 1-y The Al content of the N layer is less than that of the Al in the first multi-quantum well layer 510. y Ga 1-y The Al component ratio of the N layer makes φ1>φ4, φ4>φ2, and φ2>φ3, forming a multi-layer structure in which a high barrier layer, a low barrier layer, and a medium barrier layer are stacked in sequence in the variable barrier height control barrier layer of the multi-quantum well light-emitting layer 500. The barrier layer design of this structure and process can effectively confine carrier electrons and holes in the multi-quantum well light-emitting layer 500 area, thereby improving the matching degree of the electron-hole concentration in the light-emitting quantum well area, so as to improve the light efficiency of the multi-band LED chip.

[0064] Furthermore, the Al in the first multi-quantum well layer 510 w In z Ga 1-w-z The Al component ratio of the N layer is greater than that of the Al in the second multi-quantum well layer 520 and the third multi-quantum well layer 530. w In z Ga 1-w-z The Al component ratio of the N layer, the Al in the fourth final quantum well layer 540 w In z Ga 1-w-z The In component ratio of the N layer is greater than that of the Al in the second multi-quantum well layer 520 and the third multi-quantum well layer 530. w In z Ga 1-w-z The In component ratio of the N layer is such that the third variable barrier control barrier layer sublayer in the first multi-quantum well layer 510 is an AlInGaN layer with a high Al component, the third variable barrier control barrier layer sublayers in the second multi-quantum well layer 520 and the third multi-quantum well layer 530 are both AlInGaN layers with low Al and low In components, and the third variable barrier control barrier layer sublayer in the fourth final quantum well layer 540 is an AlInGaN layer with a high In component.

[0065] The present invention controls the band barrier height and resistance value of the variable barrier height control barrier layer in the multi-quantum well light-emitting layer 500 by regulating the material component ratio, material doping type, doping concentration, etc. in the variable barrier height control barrier layer in the multi-quantum well light-emitting layer 500, thereby controlling the current expansion performance of the epitaxial structure and improving the hole injection efficiency of the P-type semiconductor material, thereby achieving the purpose of regulating the electron hole concentration distribution in the multi-quantum well light-emitting layer 500 and improving the luminous efficiency of the multi-band LED chip.

[0066] Furthermore, the InGaN quantum well layer in the fourth final quantum well layer 540 is an InGaN layer that has undergone surface roughening annealing treatment. The surface roughening annealing treatment can decompose defects such as parts with poor crystallization quality on the material surface and clusters with high In components, which is beneficial to improving the crystal quality of the InGaN layer material. At the same time, a roughened material surface is formed, which can reduce the in-plane total reflection and absorption loss of photons in the semiconductor material and improve the light extraction efficiency.

[0067] Exemplarily, the surface roughening annealing treatment includes: after the InGaN layer is grown, intermittently and cyclically introducing a mixed gas of N2 and H2 into the reaction chamber and stabilizing it for 5s-50s, the temperature of the surface roughening annealing treatment is 820℃-1080℃, the pressure is 50torr-360torr, and the mixing ratio of N2 and H2 is 1:(0.2-3). It can be understood that the intermittent and cyclic introduction of the mixed gas of N2 and H2 and stabilizing it for 5s-50s means that after each gas introduction, the introduction is paused and the conditions in the chamber are kept unchanged, and the duration is 5s-50s.

[0068] Furthermore, the third variable barrier control barrier layer sublayer in the fourth final quantum well layer 540 is an AlInGaN layer that has undergone surface roughening annealing treatment. The surface roughening annealing treatment can decompose defects such as parts with poor crystallization quality and clusters with high In components on the material surface, which is beneficial to improving the crystal quality of the AlInGaN layer. At the same time, a rough material surface is formed, which can reduce the in-plane total reflection and absorption loss of photons in the semiconductor material, improve the light extraction efficiency, and further improve the light efficiency of the multi-band LED chip.

[0069] Exemplarily, the third variable barrier control barrier layer sublayer in the fourth final quantum well layer 540 is an AlInGaN layer that has undergone surface roughening annealing treatment, and the surface roughening annealing treatment includes: after the growth of the AlInGaN layer is completed, a mixed gas of N2 and H2 is intermittently and cyclically introduced into the reaction chamber and stabilized for 10s-100s, the temperature of the surface roughening annealing treatment is 820℃-1080℃, the pressure is 50torr-360torr, and the mixing ratio of N2 and H2 is 1:(0.5-6). It can be understood that the intermittent and cyclic introduction of the mixed gas of N2 and H2 and stabilization for 10s-100s means that after each gas introduction, the introduction is paused and the conditions in the chamber are kept unchanged, and the duration is 10s-100s.

[0070] In some specific embodiments, see Figure 2-Figure 6 The first multi-quantum well layer 510 is a superlattice structure formed by a first InGaN quantum well layer 511 and a first variable barrier height control barrier layer 512 that are periodically and alternately grown, with a period number of 1-5; wherein the first variable barrier height control barrier layer 512 includes a first GaN sublayer 5121, an Al sublayer 5122, and a GaN sublayer 5123 sequentially stacked on the first InGaN quantum well layer 511. x1 Ga 1-x1 N sublayer 5122, Al w1 In z1 Ga 1-w1-z1 N sublayer 5123, Al y1 Ga 1-y1 N sublayer 5124 and second GaN sublayer 5125 .

[0071] The second multi-quantum well layer 520 is a superlattice structure of a second InGaN quantum well layer 521 and a second variable barrier height control barrier layer 522 that are periodically grown alternately, with a period number of 2-6; wherein the second variable barrier height control barrier layer 522 includes a third GaN sublayer 5221, an Al sublayer 5222, and a plurality of other sublayers stacked sequentially on the second InGaN quantum well layer 521. x2 Ga 1-x2 N sublayer 5222, Al w2 In z2 Ga 1-w2-z2 N sublayer 5223, Al y2 Ga 1-y2 N sublayer 5224 and fourth GaN sublayer 5225 .

[0072] The third multi-quantum well layer 530 is a superlattice structure of a third InGaN quantum well layer 531 and a third variable barrier height control barrier layer 532 that are grown periodically and alternately, with a period number of 2-5; wherein the third variable barrier height control barrier layer 532 includes a fifth GaN sublayer 5321, an Al sublayer 5322, and a plurality of GaN sublayers 5321, 5 Al sublayers 5323, 5 Al sublayers 5324, 5 Al sublayers 5325, 5 Al sublayers 5326, 5 Al sublayers 5327, 5 Al sublayers 53 ... x3 Ga 1-x3 N sublayer 5322, Al w3 In z3 Ga 1-w3-z3 N sublayer 5323, Al y3 Ga 1-y3 N sublayer 5324 and sixth GaN sublayer 5325 .

[0073] The fourth final quantum well layer 540 is a superlattice structure of a fourth InGaN quantum well layer 541 and a fourth variable barrier height control barrier layer 542 that are periodically grown alternately, with a period number of 1-3; wherein the fourth variable barrier height control barrier layer 542 includes a seventh GaN sublayer 5421, an Al sublayer 5422, and a plurality of GaN sublayers 5423, 5424, 5425, 5426, 5427, 5428, 5429, 543, 543, 544, 545, 546, 547, 548, 549, 550, 560, 561, 562, 563, 564, 565, 566, 567, 568, 570, 571, 572, 5 x4 Ga 1-x4 N sublayer 5422, Al w4 In z4 Ga 1-w4-z4 N sublayer 5423, Al y4 Ga 1-y4 N sublayer 5424 and eighth GaN sublayer 5425 .

[0074] Preferably, the proportion of In component in the first InGaN quantum well layer 511 is 0.16-0.19, and the growth thickness is 2.0nm-4.7nm; the proportion of In component in the second InGaN quantum well layer 521 is 0.13-0.16, and the growth thickness is 2.0nm-4.7nm; the proportion of In component in the third InGaN quantum well layer 531 is 0.10-0.13, and the growth thickness is 2.0nm-4.7nm; the proportion of In component in the fourth InGaN quantum well layer 541 is 0.10-0.13, and the growth thickness is 2.0nm-4.7nm.

[0075] Preferably, the Al x3 Ga 1-x3 The Al component ratio x3 of the N sublayer 5322 is less than the Al x2 Ga 1-x2 The Al component ratio of the N sublayer 5222 is x2, and the Al x2 Ga 1-x2 The Al component ratio x2 of the N sublayer 5222 is less than the Al x4 Ga 1-x4The Al component ratio of the N sublayer 5422 is x4. x4 Ga 1-x4 The Al component ratio x4 of the N sublayer 5422 is less than the Al x1 Ga 1-x1 The Al component ratio of the N sublayer 5122 is x1, that is, x3<x2<x4<x1, and the Al y3 Ga 1-y3 The Al component ratio y3 of the N sublayer 5324 is less than the Al y2 Ga 1- y2 The Al component of the N sublayer 5224 accounts for y2, the Al y2 Ga 1-y2 The Al component ratio y2 of the N sublayer 5224 is less than the Al y4 Ga 1-y4 The Al component of the N sublayer 5424 accounts for y4, the Al y4 Ga 1-y4 The Al component ratio y4 of the N sublayer 5424 is less than the Al y1 Ga 1-y1 The Al component ratio of the N sub-layer 5124 is y1, that is, y3<y2<y4<y1.

[0076] Illustratively, 0.03≤x1≤0.18, 0.03≤y1≤0.18; 0.01≤x2≤0.12, 0.01≤y2≤0.12; 0≤x3≤0.10, 0≤y3≤0.10; 0.02≤x4≤0.15, 0.02≤y4≤0.15.

[0077] Preferably, the Al w1 In z1 Ga 1-w1-z1 The Al component ratio w1 of the N sublayer 5123 is greater than the Al w2 In z2 Ga 1-w2- z2 The Al component of the N sublayer 5223 accounts for w2, the Al w1 In z1 Ga 1-w1-z1 The Al component ratio w1 of the N sublayer 5123 is greater than the Al w3 In z3 Ga 1-w3-z3 The Al component of the N sublayer 5323 accounts for w3, that is, w1>w2, w1>w3, and the Al w4 In z4 Ga 1-w4-z4 The In component ratio z4 of the N sublayer 5423 is greater than that of the Al w2 In z2 Ga1-w2-z2 The In component of the N sublayer 5223 accounts for z2, and the Al w4 In z4 Ga 1-w4-z4 The In component ratio z4 of the N sublayer 5423 is greater than that of the Al w3 In z3 Ga 1-w3-z3 The In component ratio of the N sublayer 5323 is z3, that is, z4>z3, z4>z2, so that the Al w1 In z1 Ga 1-w1-z1 The N sublayer 5123 is an AlInGaN layer with a high Al content. w2 In z2 Ga 1-w2-z2 N sublayer 5223, Al w3 In z3 Ga 1-w3-z3 The N sublayers 5323 are all AlInGaN layers with low Al and low In content. w4 In z4 Ga 1-w4-z4 The N sublayer 5423 is an AlInGaN layer with a high In content. More preferably, w2=w3=w4, z3=z2, and z3>z1.

[0078] Illustratively, 0.03≤w1≤0.36, 0≤z1≤0.03; 0≤w2≤0.10, 0≤z2≤0.05; 0≤w3≤0.10, 0≤z3≤0.05; 0≤w4≤0.10, 0.03≤z4≤0.12.

[0079] Preferably, in the first multi-quantum well layer 510, the growth thickness H of the first GaN sublayer 5121 is 11 is 0.6nm-6nm, the Al x1 Ga 1-x1 The growth thickness H of the N sublayer 5122 12 is 0.2nm-2nm, the Al w1 In z1 Ga 1-w1-z1 The growth thickness H of the N sublayer 5123 13 is 0.5nm-6nm, the Al y1 Ga 1-y1 The growth thickness H of the N sublayer 5124 14 The growth thickness H of the second GaN sublayer 5125 is 0.2nm-2nm. 15 It is 0.6nm-6nm.

[0080] Preferably, in the second multi-quantum well layer 520, the growth thickness H of the third GaN sublayer 5221 is21 is 0.6nm-6nm, the Al x2 Ga 1-x2 The growth thickness H of the N sublayer 5222 22 is 0.2nm-2nm, the Al w2 In z2 Ga 1-w2-z2 The growth thickness H of the N sublayer 5223 23 is 0.5nm-6nm, the Al y2 Ga 1-y2 The growth thickness H of the N sublayer 5224 24 The growth thickness H of the fourth GaN sublayer 5225 is 0.2nm-2nm. 25 It is 0.6nm-6nm.

[0081] Preferably, in the third multi-quantum well layer 530, the growth thickness H of the fifth GaN sublayer 5321 is 31 is 0.6nm-6nm, the Al x3 Ga 1-x3 The growth thickness H of the N sublayer 5322 32 is 0.2nm-2nm, the Al w3 In z3 Ga 1-w3-z3 The growth thickness H of the N sublayer 5323 33 is 0.5nm-6nm, the Al y3 Ga 1-y3 The growth thickness H of the N sublayer 5324 34 The growth thickness H of the sixth GaN sublayer 5325 is 0.2nm-2nm. 35 It is 0.6nm-6nm.

[0082] Preferably, in the fourth final quantum well layer 540, the growth thickness H of the seventh GaN sublayer 5421 is 41 is 0.6nm-6nm, the Al x4 Ga 1-x4 The growth thickness H of the N sublayer 5422 42 is 0.2nm-2nm, the Al w4 In z4 Ga 1-w4-z4 The growth thickness H of the N sublayer 5423 43 is 0.5nm-6nm, the Al y4 Ga 1-y4 The growth thickness H of the N sublayer 5424 44 The growth thickness H of the eighth GaN sublayer 5425 is 0.2nm-2nm. 45 It is 0.6nm-6nm.

[0083] Understandably, H 11 、H 21 、H 31 、H 41 Can be equal or not, H 12 、H 22 、H 32 、H 44 Can be equal or not, H 13 、H 23 、H 33 、H 43 Can be equal or not, H 14 、H 24 、H 34 、H 44 Can be equal or not, H 15 、H 25 、H 35 、H 45 Can be equal or unequal.

[0084] Accordingly, the present invention also provides a method for preparing the epitaxial structure of the multi-band LED, comprising:

[0085] (1) Providing a substrate 100;

[0086] (2) sequentially growing a buffer layer 200 on the substrate 100;

[0087] (3) growing an N-type semiconductor layer 300 on the buffer layer 200;

[0088] (4) growing a low-temperature stress release layer 400 on the N-type semiconductor layer 300;

[0089] (5) growing a multi-quantum well light-emitting layer 500 on the low-temperature stress release layer 400, wherein the multi-quantum well light-emitting layer 500 includes a first multi-quantum well layer 510, a second multi-quantum well layer 520, a third multi-quantum well layer 530, and a fourth final quantum well layer 540 stacked in sequence, wherein the first multi-quantum well layer 510, the second multi-quantum well layer 520, the third multi-quantum well layer 530, and the fourth final quantum well layer 540 all include periodically alternately stacked InGaN quantum well layers and variable barrier height control barrier layers, and the variable barrier height control barrier layer includes five sublayers stacked in sequence on the InGaN quantum well layer: a first variable barrier control barrier layer sublayer, a second variable barrier control barrier layer sublayer, a third variable barrier control barrier layer sublayer, a fourth variable barrier control barrier layer sublayer, and a fifth variable barrier control barrier layer sublayer; λ1>λ2>λ3, λ3=λ4;

[0090] (6) growing an electron blocking layer 600 on the multi-quantum well light-emitting layer 500;

[0091] (7) growing a P-type semiconductor layer 700 on the electron blocking layer 600;

[0092] Preferably, in the first multi-quantum well layer 510, the growth temperature of the first InGaN quantum well layer 511 is 750°C-929°C, and the growth pressure is 50torr-360torr; the growth temperature of the first GaN sublayer 5121 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al x1 Ga 1-x1 The growth temperature of the N sublayer 5122 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al w1 In z1 Ga 1-w1-z1 The growth temperature of the N sublayer 5123 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al y1 Ga 1-y1 The growth temperature of the N sublayer 5124 is 825° C.-938° C., and the growth pressure is 50 torr-360 torr; the growth temperature of the second GaN sublayer 5125 is 825° C.-938° C., and the growth pressure is 50 torr-360 torr.

[0093] Preferably, in the second multi-quantum well layer 520, the second InGaN quantum well layer 521 is grown at a temperature of 770°C-929°C and a growth pressure of 50torr-360torr; the third GaN sublayer 5221 is grown at a temperature of 825°C-938°C and a growth pressure of 50torr-360torr; the Al x2 Ga 1-x2 The growth temperature of the N sublayer 5222 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al w2 In z2 Ga 1-w2-z2 The growth temperature of the N sublayer 5223 is 825°C-938°C. y2 Ga 1-y2 The growth temperature T of the N sublayer 5224 24 The growth temperature of the fourth GaN sublayer 5225 is 825° C.-938° C., and the growth pressure is 50 torr-360 torr. The growth temperature of the fourth GaN sublayer 5225 is 825° C.-938° C., and the growth pressure is 50 torr-360 torr.

[0094] Preferably, in the third multi-quantum well layer 530, the growth temperature of the third InGaN quantum well layer 531 is 790°C-929°C, and the growth pressure is 50torr-360torr; the growth temperature of the fifth GaN sublayer 5321 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al x3 Ga 1-x3 The growth temperature of the N sublayer 5322 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al w3 In z3 Ga 1-w3-z3 The growth temperature of the N sublayer 5323 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al y3 Ga 1-y3 The growth temperature of the N sublayer 5324 is 825° C.-938° C., and the growth pressure is 50 torr-360 torr; the growth temperature of the sixth GaN sublayer 5325 is 825° C.-938° C., and the growth pressure is 50 torr-360 torr.

[0095] Preferably, in the fourth final quantum well layer 540, the growth temperature of the fourth InGaN quantum well layer 541 is 790°C-929°C, and the growth pressure is 50torr-360torr; the growth temperature of the seventh GaN sublayer 5421 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al x4 Ga 1-x4 The growth temperature of the N sublayer 5422 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al w4 In z4 Ga 1-w4-z4 The growth temperature of the N sublayer 5423 is 825°C-938°C, and the growth pressure is 50torr-360torr; the Al y4 Ga 1-y4 The growth temperature of the N sublayer 5424 is 825° C.-938° C., and the growth pressure is 50 torr-360 torr; the growth temperature of the eighth GaN sublayer 5425 is 825° C.-938° C., and the growth pressure is 50 torr-360 torr.

[0096] It can be understood that the substrate 100 can be a sapphire substrate, a silicon carbide substrate or a silicon substrate; the buffer layer 200, the N-type semiconductor layer 300, the low-temperature stress release layer 400, the electron blocking layer 600 and the P-type semiconductor layer 700 are all grown using existing processes and raw materials, and are not further elaborated in this embodiment.

[0097] The present invention will be further described below with specific embodiments:

[0098] Example 1

[0099] This embodiment provides an epitaxial structure for a multi-band LED, comprising a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer stacked in sequence. The multi-quantum well light-emitting layer comprises a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer, and a fourth final quantum well layer stacked in sequence.

[0100] The first multi-quantum well layer is a superlattice structure formed by a first InGaN quantum well layer and a first variable barrier height control barrier layer grown periodically and alternately, and the number of periods is 3; wherein the first variable barrier height control barrier layer includes a first GaN sublayer, an Al sublayer, and a GaN sublayer sequentially stacked on the first InGaN quantum well layer. x1 Ga 1-x1 N sublayer, Al w1 In z1 Ga 1-w1-z1 N sublayer, Al y1 Ga 1-y1 N sublayer, second GaN sublayer; emission wavelength λ1 is 466nm;

[0101] The first InGaN quantum well layer has an In component ratio of 0.17 and a growth thickness of 3.4 nm. The first GaN sublayer is N-type doped with a doping concentration of 5×10 17 / cm 3 , growth thickness H 11 =3.3nm; the Al x1 Ga 1-x1 The N sublayer is an unintentionally doped AlGaN layer, x1 = 0.05, and the growth thickness is H. 12 =1.1nm, the Al w1 In z1 Ga 1-w1-z1 The N sublayer is N-type doped with a doping concentration of 4×10 17 / cm 3 , w1=0.08,z1=0.03,growth thickness H 13 =3.2nm; the Al y1 Ga 1-y1 The N sublayer is an unintentionally doped AlGaN layer, y1 = 0.05, and the growth thickness is H 14 =1.1nm, the second GaN sublayer is N-type doped with a doping concentration of 5×10 17 / cm 3 , growth thickness H 15 =3.3nm;

[0102] The second multi-quantum well layer is a superlattice structure formed by a second InGaN quantum well layer and a second variable barrier height control barrier layer grown periodically and alternately, and the number of periods is 4; wherein the second variable barrier height control barrier layer includes a third GaN sublayer, an Al sublayer, and a GaN sublayer sequentially stacked on the second InGaN quantum well layer. x2 Ga 1-x2 N sublayer, Al w2 In z2 Ga 1-w2-z2 N sublayer, Al y2 Ga 1-y2 N sublayer, fourth GaN sublayer; emission wavelength λ2 is 452nm;

[0103] The proportion of In component in the second InGaN quantum well layer is 0.15, and the growth thickness is 3.4nm; the third GaN sublayer is N-type doped with a doping concentration of 4.5×10 17 / cm 3 , growth thickness H 21 =3.3nm; the Al x2 Ga 1-x2 The N sublayer is an unintentionally doped AlGaN layer, x2 = 0.05, and the growth thickness is H. 22 =1.1nm, the Al w2 In z2 Ga 1-w2-z2 The N sublayer is N-type doped with a doping concentration of 3.5×10 17 / cm 3 , w1=0.08,z1=0.03,growth thickness H 23 =3.2nm; the Al y2 Ga 1-y2 The N sublayer is an unintentionally doped AlGaN layer, y2 = 0.05, and the growth thickness is H 24 =1.1nm, the fourth GaN sublayer is N-type doped with a doping concentration of 4.5×10 17 / cm 3 , growth thickness H 25 =3.3nm;

[0104] The third multi-quantum well layer is a superlattice structure formed by a periodically alternating third InGaN quantum well layer and a third variable barrier height control barrier layer, and the number of periods is 3; wherein the third variable barrier height control barrier layer includes a fifth GaN sublayer, an Al sublayer, and a fifth GaN sublayer sequentially stacked on the third InGaN quantum well layer. x3 Ga 1-x3 N sublayer, Al w3 In z3 Ga 1-w3-z3 N sublayer, Aly3 Ga 1-y3 N sublayer, sixth GaN sublayer; emission wavelength λ3 is 431nm;

[0105] The proportion of In component in the third InGaN quantum well layer is 0.11, and the growth thickness is 3.4nm; the fifth GaN sublayer is N-type doped with a doping concentration of 3.8×10 17 / cm 3 , growth thickness H 31 =3.3nm; the Al x3 Ga 1-x3 The N sublayer is an unintentionally doped AlGaN layer, x3 = 0.05, and the growth thickness is H. 32 =1.1nm, the Al w3 In z3 Ga 1-w3-z3 The N sublayer is N-type doped with a doping concentration of 3×10 17 / cm 3 , w1=0.08,z1=0.03,growth thickness H 33 =3.2nm; the Al y3 Ga 1-y3 The N sublayer is an unintentionally doped AlGaN layer, y3 = 0.05, and the growth thickness is H 34 =1.1nm, the sixth GaN sublayer is N-type doped with a doping concentration of 3.8×10 17 / cm 3 , growth thickness H 35 =3.3nm;

[0106] The fourth final quantum well layer includes a fourth InGaN quantum well layer and a fourth variable barrier height control barrier layer stacked in sequence; wherein the fourth variable barrier height control barrier layer includes a seventh GaN sublayer, an Al sublayer, and a seventh GaN sublayer stacked in sequence on the fourth InGaN quantum well layer. x4 Ga 1-x4 N sublayer, Al w4 In z4 Ga 1-w4-z4 N sublayer, Al y4 Ga 1-y4 N sublayer, eighth GaN sublayer; emission wavelength λ4 is 431nm;

[0107] The proportion of In component in the fourth InGaN quantum well layer is 0.12, and the growth thickness is 3.4nm; the seventh GaN sublayer is N-type doped with a doping concentration of 1×10 19 / cm 3 , growth thickness H 41 =3.3nm; the Al x4 Ga1-x4 The N sublayer is an unintentionally doped AlGaN layer, x4 = 0.05, and the growth thickness is H 42 =1.1nm, the Al w4 In z4 Ga 1-w4-z4 The N sublayer is N-type doped with a doping concentration of 2×10 19 / cm 3 , w1=0.08,z1=0.03,growth thickness H 43 =3.2nm; the Al y4 Ga 1-y4 The N sublayer is an unintentionally doped AlGaN layer, y4 = 0.05, and the growth thickness is H 44 =1.1nm, the eighth GaN sublayer is N-type doped with a doping concentration of 1×10 19 / cm 3 , growth thickness H 45 =3.3nm.

[0108] Accordingly, this embodiment further provides a method for preparing the epitaxial structure of the multi-band LED, comprising:

[0109] (1) providing a substrate;

[0110] (2) sequentially growing a buffer layer on the substrate;

[0111] (3) growing an N-type semiconductor layer on the buffer layer;

[0112] (4) growing a low-temperature stress release layer on the N-type semiconductor layer;

[0113] (5) growing a multi-quantum well light-emitting layer on the low-temperature stress release layer, wherein the multi-quantum well light-emitting layer includes a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer, and a fourth final quantum well layer stacked in sequence;

[0114] (6) growing an electron blocking layer on the multi-quantum well light-emitting layer;

[0115] (7) growing a P-type semiconductor layer on the electron blocking layer;

[0116] The growth temperature of the first InGaN quantum well layer is 840°C and the growth pressure is 200 torr; the growth temperature of the first GaN sublayer is 880°C and the growth pressure is 200 torr; the Al x1 Ga 1-x1 The growth temperature of the N sublayer is 880°C and the growth pressure is 200 torr; the Al w1 In z1 Ga 1-w1-z1The growth temperature of the N sublayer is 880°C and the growth pressure is 200 torr; the Al y1 Ga 1-y1 The growth temperature of the N sublayer is 880°C and the growth pressure is 200 torr; the growth temperature of the second GaN sublayer is 880°C and the growth pressure is 200 torr;

[0117] The growth temperature of the second InGaN quantum well layer is 850°C and the growth pressure is 200 torr; the growth temperature of the third GaN sublayer is 880°C and the growth pressure is 200 torr; the Al x2 Ga 1-x2 The growth temperature of the N sublayer is 880°C and the growth pressure is 200 torr; the Al w2 In z2 Ga 1-w2-z2 The growth temperature of the N sublayer is 880°C and the growth pressure is 200 torr; the Al y2 Ga 1-y2 The growth temperature of the N sublayer is 880° C. and the growth pressure is 200 torr; the growth temperature of the fourth GaN sublayer is 880° C. and the growth pressure is 200 torr;

[0118] The growth temperature of the third InGaN quantum well layer is 860°C and the growth pressure is 200 torr; the growth temperature of the fifth GaN sublayer is 880°C and the growth pressure is 200 torr; the Al x3 Ga 1-x3 The growth temperature of the N sublayer is 880°C and the growth pressure is 200 torr; the Al w3 In z3 Ga 1-w3-z3 The growth temperature of the N sublayer is 880°C and the growth pressure is 200 torr; the Al y3 Ga 1-y3 The growth temperature of the N sublayer is 880° C. and the growth pressure is 200 torr; the growth temperature of the sixth GaN sublayer is 880° C. and the growth pressure is 200 torr;

[0119] The growth temperature of the fourth InGaN quantum well layer is 860°C and the growth pressure is 200 torr; the growth temperature of the seventh GaN sublayer is 880°C and the growth pressure is 200 torr; the Al x4 Ga 1-x4 The growth temperature of the N sublayer is 880°C and the growth pressure is 200 torr; the Al w4 In z4 Ga 1-w4-z4 The growth temperature of the N sublayer is 880°C and the growth pressure is 200 torr; the Aly4 Ga 1-y4 The growth temperature of the N sublayer is 880° C., and the growth pressure is 200 torr; the growth temperature of the eighth GaN sublayer is 880° C., and the growth pressure is 200 torr.

[0120] Example 2

[0121] This embodiment provides an epitaxial structure of a multi-band LED, which is basically the same as that of the first embodiment, except that:

[0122] The seventh GaN sublayer is P-type doped with a doping concentration of 1×10 19 / cm 3 , growth thickness H 41 =3.3nm; the Al w4 In z4 Ga 1-w4-z4 The N sublayer is doped with P-type, with a doping concentration of 2×10 19 / cm 3 , w1=0.08,z1=0.03,growth thickness H 43 =3.2nm; the eighth GaN sublayer is P-type doped with a doping concentration of 1×10 19 / cm 3 , growth thickness H 45 =3.3nm.

[0123] Example 3

[0124] This embodiment provides an epitaxial structure of a multi-band LED, which is basically the same as that of embodiment 2, except that:

[0125] x1=0.15, x2=0.07, x3=0.05, x4=0.09, y1=0.15, y2=0.06, y3=0.03, y4=0.08.

[0126] Example 4

[0127] This embodiment provides an epitaxial structure of a multi-band LED, which is basically the same as that of embodiment 3, except that:

[0128] w1=0.2, z1=0.01; w2=0.05, z2=0.03; w3=0.05, z3=0.03; w4=0.05, z4=0.08.

[0129] Example 5

[0130] This embodiment provides an epitaxial structure of a multi-band LED, which is basically the same as that of embodiment 4, except that:

[0131] The fourth InGaN quantum well layer is an InGaN layer that has undergone surface roughening annealing treatment. The surface roughening annealing treatment includes: after the growth of the fourth InGaN quantum well layer is completed, a mixed gas of N2 and H2 is intermittently and cyclically introduced into the reaction chamber and stabilized for 25 seconds. The temperature of the surface roughening annealing treatment is 900°C, the pressure is 210 torr, and the mixing ratio of N2 and H2 is 1:1.5.

[0132] Example 6

[0133] This embodiment provides an epitaxial structure of a multi-band LED, which is basically the same as that of Embodiment 5, except that:

[0134] The Al w4 In z4 Ga 1-w4-z4 The N sub-layer is an AlInGaN layer that has undergone surface roughening annealing treatment, and the surface roughening annealing treatment includes: w4 In z4 Ga 1-w4-z4 After the growth of the N sublayer is completed, a mixed gas of N2 and H2 is intermittently and cyclically introduced into the reaction chamber and stabilized for 50 seconds. The temperature of the surface roughening annealing treatment is 950°C, the pressure is 210 torr, and the mixing ratio of N2 and H2 is 1:3.

[0135] Comparative Example 1

[0136] This comparative example provides an epitaxial structure of a multi-band LED, which is basically the same as that of Example 1, except that:

[0137] The multi-quantum well light-emitting layer includes a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer, and a fourth multi-quantum well layer stacked in sequence, and the light-emitting wavelength is 452 nm.

[0138] The light-emitting diode epitaxial wafers prepared in Examples 1 to 6 and Comparative Example 1 were prepared into 10 mil × 24 mil chips using the same chip process conditions. 300 LED chips were extracted from each example and tested at a current of 120 mA. Compared with the LED chip prepared in Comparative Example 1, the improvement rate of luminous efficiency of each example was calculated. The specific test results are shown in Table 1.

[0139] Table 1 Test results of examples and comparative examples

[0140] Luminous efficiency improvement rate / % Color rendering index Example 1 0.77 87 Example 2 0.93 88 Example 3 1.03 88 Example 4 1.32 90 Example 5 1.58 90 Example 6 1.79 92 Comparative Example 1 — 79

[0141] From the above results, it can be seen that after the epitaxial structure of the multi-band LED in this application forms an LED chip, a full-spectrum white light LED light source is generated by exciting the red and green mixed phosphor layer with three-band light sources. The generated full-spectrum white light is closer to the sunlight spectrum, thereby realizing a healthy full-spectrum white light LED light source with a high color rendering index, and can also improve the luminous efficiency of the multi-band LED chip.

[0142] The above disclosure is only a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. An epitaxial structure of a multi-band LED, characterized in that: The invention comprises a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, an electron blocking layer and a P-type semiconductor layer stacked in sequence, wherein: The multi-quantum well light-emitting layer includes a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer, and a fourth final quantum well layer stacked in sequence; the first multi-quantum well layer, the second multi-quantum well layer, the third multi-quantum well layer, and the fourth final quantum well layer all include periodically alternately stacked InGaN quantum well layers and variable barrier height control barrier layers, and the variable barrier height control barrier layer includes five sublayers stacked in sequence on the InGaN quantum well layer: a first variable barrier control barrier layer sublayer, a second variable barrier control barrier layer sublayer, a third variable barrier control barrier layer sublayer, a fourth variable barrier control barrier layer sublayer, and a fifth variable barrier control barrier layer sublayer; The emission wavelength of the first multi-quantum well layer is λ1, the emission wavelength of the second multi-quantum well layer is λ2, the emission wavelength of the third multi-quantum well layer is λ3, and the emission wavelength of the fourth final quantum well layer is λ4, λ1>λ2>λ3, λ3=λ4.

2. The epitaxial structure of the multi-band LED according to claim 1, wherein: The energy band barrier height of the first multi-quantum well layer is φ1, the energy band barrier height of the second multi-quantum well layer is φ2, the energy band barrier height of the third multi-quantum well layer is φ3, and the energy band barrier height of the fourth final quantum well layer is φ4, φ1>φ4, φ4>φ2, φ2>φ3; The λ1 is 460nm-480nm, the λ2 is 445nm-460nm, the λ3 is 430nm-445nm, and the λ4 is 430nm-445nm.

3. The epitaxial structure of the multi-band LED according to claim 1, wherein: The first variable barrier regulating barrier layer sublayer is a GaN layer, and the first variable barrier regulating barrier layer sublayer is N-type doped or P-type doped; the second variable barrier regulating barrier layer sublayer is Al x Ga 1-x N layer, the second variable barrier regulating barrier layer sublayer is not intentionally doped; the third variable barrier regulating barrier layer sublayer is Al w In z Ga 1-w-z N layer, the third variable barrier regulating barrier layer sublayer is N-type doped or P-type doped; the fourth variable barrier regulating barrier layer sublayer is Al y Ga 1-y N layer, the fourth variable barrier regulating barrier layer sublayer is not intentionally doped; The fifth variable potential barrier regulating barrier layer sublayer is a GaN layer, and the fifth variable potential barrier regulating barrier layer sublayer is N-type doped or P-type doped.

4. The epitaxial structure of the multi-band LED according to claim 1, wherein: The growth thickness of the first variable barrier regulating barrier layer sublayer is 0.6nm-6nm, the growth temperature of the first variable barrier regulating barrier layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr; The second variable barrier regulates the growth thickness of the barrier layer sublayer to be 0.2nm-2nm, the growth temperature of the second variable barrier regulates the growth of the barrier layer sublayer to be 825℃-938℃, and the growth pressure to be 50torr-360torr; The thickness of the third variable barrier regulating barrier layer sublayer is 0.5nm-6nm, the growth temperature of the third variable barrier regulating barrier layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr; The growth thickness of the fourth variable barrier regulating barrier layer sublayer is 0.2nm-2nm, the growth temperature of the fourth variable barrier regulating barrier layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr; The growth thickness of the fifth variable barrier regulating barrier layer sublayer is 0.6nm-6nm, the growth temperature of the fifth variable barrier regulating barrier layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr.

5. The epitaxial structure of the multi-band LED according to claim 1 or 3, wherein: The InGaN quantum well layer in the fourth final quantum well layer is an InGaN layer that has undergone surface roughening annealing treatment, wherein the surface roughening annealing treatment comprises: after the growth of the InGaN layer is completed, intermittently and cyclically introducing a mixed gas of N2 and H2 into the reaction chamber and stabilizing it for 5s-50s, wherein the surface roughening annealing treatment is performed at a temperature of 820°C-1080°C, a pressure of 50torr-360torr, and a mixing ratio of N2 to H2 of 1:(0.2-3); The third variable barrier control barrier layer sublayer in the fourth final quantum well layer is an AlInGaN layer that has undergone surface roughening annealing treatment. The surface roughening annealing treatment includes: after the growth of the AlInGaN layer is completed, intermittently and cyclically introducing a mixed gas of N2 and H2 into the reaction chamber and stabilizing it for 10s-100s. The temperature of the surface roughening annealing treatment is 820℃-1080℃, the pressure is 50torr-360torr, and the mixing ratio of N2 and H2 is 1:(0.5-6).

6. The epitaxial structure of the multi-band LED according to claim 1 or 3, wherein: The first multi-quantum well layer is a superlattice structure formed by a first InGaN quantum well layer and a first variable barrier height control barrier layer grown periodically and alternately, and the number of periods is 1-5; wherein the first variable barrier height control barrier layer includes a first GaN sublayer, an Al sublayer, and a GaN sublayer sequentially stacked on the first InGaN quantum well layer. x1 Ga 1-x1 N sublayer, Al w1 In z1 Ga 1-w1-z1 N sublayer, Al y1 Ga 1-y1 N sublayer, second GaN sublayer; The second multi-quantum well layer is a superlattice structure formed by a second InGaN quantum well layer and a second variable barrier height control barrier layer grown periodically and alternately, with a period number of 2-6; wherein the second variable barrier height control barrier layer includes a third GaN sublayer, an Al sublayer, and a plurality of other sublayers sequentially stacked on the second InGaN quantum well layer. x2 Ga 1-x2 N sublayer, Al w2 In z2 Ga 1-w2-z2 N sublayer, Al y2 Ga 1-y2 N sublayer, fourth GaN sublayer; The third multi-quantum well layer is a superlattice structure formed by a third InGaN quantum well layer and a third variable barrier height control barrier layer grown periodically and alternately, with a period number of 2-5; wherein the third variable barrier height control barrier layer includes a fifth GaN sublayer, an Al sublayer, and a plurality of other sublayers sequentially stacked on the third InGaN quantum well layer. x3 Ga 1-x3 N sublayer, Al w3 In z3 Ga 1-w3-z3 N sublayer, Al y3 Ga 1-y3 N sublayer, sixth GaN sublayer; The fourth final quantum well layer includes a fourth InGaN quantum well layer and a fourth variable barrier height control barrier layer stacked in sequence; wherein the fourth variable barrier height control barrier layer includes a seventh GaN sublayer, an Al sublayer, and a seventh GaN sublayer stacked in sequence on the fourth InGaN quantum well layer. x4 Ga 1-x4 N sublayer, Al w4 In z4 Ga 1-w4-z4 N sublayer, Al y4 Ga 1-y4 N sub-layer, and eighth GaN sub-layer.

7. The epitaxial structure of the multi-band LED according to claim 6, wherein: The first GaN sublayer is N-type doped, and the doping concentration of the N-type doping is 1.8×10 17 / cm 3 ~8.7×10 17 / cm 3 ; The Al w1 In z1 Ga 1-w1-z1 The N sublayer is N-type doped, and the doping concentration of N-type doping is 1.3×10 17 / cm 3 ~6.8×10 17 / cm 3 The second GaN sublayer is N-type doped, and the doping concentration of N-type doping is 1.8×10 17 / cm 3 ~8.7×10 17 / cm 3 ; The third GaN sublayer is N-type doped, and the doping concentration of the N-type doping is 1.5×10 17 / cm 3 ~7.6×10 17 / cm 3 ; The Al w2 In z2 Ga 1-w2-z2 The N sublayer is N-type doped, and the doping concentration of N-type doping is 1.1×10 17 / cm 3 ~6.0×10 17 / cm 3 The fourth GaN sublayer is N-type doped, and the doping concentration of N-type doping is 1.5×10 17 / cm 3 ~7.6×10 17 / cm 3 ; The fifth GaN sublayer is N-type doped, and the doping concentration of the N-type doping is 1.2×10 17 / cm 3 ~6.5×10 17 / cm 3 ; The Al w3 In z3 Ga 1-w3-z3 The N sublayer is N-type doped, and the doping concentration of N-type doping is 0.8×10 17 / cm 3 ~5.2×10 17 / cm 3 The sixth GaN sublayer is N-type doped, and the doping concentration of N-type doping is 1.2×10 17 / cm 3 ~6.5×10 17 / cm 3 ; The seventh GaN sublayer is P-type doped, and the doping concentration of the P-type doping is 1.8×10 18 / cm 3 ~5.6×10 19 / cm 3 ; The Al w4 In z4 Ga 1-w4-z4 The N sublayer is doped with P-type, and the doping concentration of N-type is 3.6×10 18 / cm 3 ~7.8×10 19 / cm 3 The eighth GaN sublayer is P-type doped and the N-type doping concentration is 1.8×10 18 / cm 3 ~5.6×10 19 / cm 3 .

8. The epitaxial structure of the multi-band LED according to claim 6, wherein: x3<x2<x4<x1, y3<y2<y4<y1; w1>w2, w2=w3=w4, z4>z3, z3>z1, z3=z2; 0.03≤x1≤0.18, 0.03≤y1≤0.18; 0.01≤x2≤0.12, 0.01≤y2≤0.12; 0≤x3≤0.10, 0≤y3≤0.10; 0.02≤x4≤0.15, 0.02≤y4≤0.15; 0.03≤w1≤0.36, 0≤z1≤0.03; 0≤w2≤0.10, 0≤z2≤0.05; 0≤w3≤0.10, 0≤z3≤0.05; 0≤w4≤0.10, 0.03≤z4≤0.

12.

9. The epitaxial structure of the multi-band LED according to claim 6, wherein: The first InGaN quantum well layer, the second InGaN quantum well layer, the third InGaN quantum well layer, and the fourth InGaN quantum well layer are all unintentionally doped InGaN single-layer structures or InGaN multi-layer structures; The proportion of In component in the first InGaN quantum well layer is 0.16-0.19, and the growth thickness is 2.0nm-4.7nm; the proportion of In component in the second InGaN quantum well layer is 0.13-0.16, and the growth thickness is 2.0nm-4.7nm; the proportion of In component in the third InGaN quantum well layer is 0.10-0.13, and the growth thickness is 2.0nm-4.7nm; the proportion of In component in the fourth InGaN quantum well layer is 0.10-0.13, and the growth thickness is 2.0nm-4.7nm.

10. A method for preparing an epitaxial structure of a multi-band LED according to any one of claims 1 to 9, characterized in that: include: (1) providing a substrate; (2) sequentially growing a buffer layer on the substrate; (3) growing an N-type semiconductor layer on the buffer layer; (4) growing a low-temperature stress release layer on the N-type semiconductor layer; (5) growing a multi-quantum well light-emitting layer on the low-temperature stress release layer; (6) growing an electron blocking layer on the multi-quantum well light-emitting layer; (7) growing a P-type semiconductor layer on the electron blocking layer; The multi-quantum well light-emitting layer includes a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer, and a fourth final quantum well layer stacked in sequence; the first multi-quantum well layer, the second multi-quantum well layer, the third multi-quantum well layer, and the fourth final quantum well layer all include periodically alternately stacked InGaN quantum well layers and variable barrier height control barrier layers, and the variable barrier height control barrier layer includes five sublayers stacked in sequence on the InGaN quantum well layer: a first variable barrier control barrier layer sublayer, a second variable barrier control barrier layer sublayer, a third variable barrier control barrier layer sublayer, a fourth variable barrier control barrier layer sublayer, and a fifth variable barrier control barrier layer sublayer; λ1>λ2>λ3, λ3=λ4.

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