Epitaxial structure of multi-band LED and preparation method thereof

Abstract

This invention relates to the technical field of light-emitting diodes (LEDs), and discloses an epitaxial structure for a multi-band LED and its fabrication method. The epitaxial structure includes a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well (MBU) light-emitting layer, an electron blocking layer, and a P-type semiconductor layer. The MBU light-emitting layer comprises a first MBU layer, a second MBU layer, a third MBU layer, and a fourth MBU layer stacked sequentially. Each MBU layer includes periodically alternating InGaN quantum well layers and a variable barrier height control layer. The variable barrier height control layer comprises five sub-layers stacked sequentially on the InGaN quantum well layers. The emission wavelength of the first MBU layer is λ1, the second MBU layer is λ2, the third MBU layer is λ3, and the fourth MBU layer is λ4, where λ1 > λ2 > λ3 and λ3 = λ4. Implementing this invention can produce a healthy full-spectrum white LED light source with a high color rendering index, a low proportion of short-wavelength blue light (causing minimal damage to retinal cells), and high luminous efficiency.

Description

Technical Field

[0001] This invention relates to the technical field of light-emitting diodes, and more particularly to an epitaxial structure of a multi-band LED and its fabrication method. Background Technology

[0002] LED light sources boast advantages such as small size, long lifespan, and high efficiency, capable of continuous use for tens of thousands of hours, making them a mainstream choice in the lighting industry. With the continuous expansion of LED light source applications, higher demands are being placed on their luminous characteristics. Among these, expanding the spectral range of LED light sources has become a major direction for improvement, resulting in products known in the industry as full-spectrum white LED light sources. Full spectrum refers to a spectrum that includes ultraviolet, visible, and infrared light, with the proportions of red, green, and blue in the visible light portion approximating sunlight, and a color rendering index close to 100. The spectrum of sunlight can be considered full spectrum.

[0003] Currently, commercially available white LED devices typically use fluorescent adhesive coated on blue LED chips to emit white light. However, in the spectral curves of full-spectrum white LED light sources, the blue light band exhibits significant fluctuations and poor stability. Furthermore, as early as 1966, Nell et al. discovered that blue light exposure can damage retinal cells, leading to decreased or even lost vision. Short-wavelength blue light between 400nm and 450nm poses the greatest threat to the retina. At the 2010 International Optical Society Congress, leading optics experts worldwide unanimously pointed out that short-wavelength blue light possesses extremely high energy, capable of penetrating the lens and reaching the retina. Blue light exposure to the retina generates free radicals, which cause the death of retinal pigment epithelial cells. This cell death leads to a lack of nutrients for photosensitive cells, resulting in irreversible vision damage. To address the shortcomings of current full-spectrum white LED light sources, further optimization and research have been conducted on the structure and process of blue LED chips. The aim is to use multi-band LED chips to excite a red and green mixed phosphor layer to produce a full-spectrum white LED light source that is less damaging to human retinal cells, healthier, and has a high color rendering index that is closer to the solar 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 its preparation method. The multi-band LED chip is used to excite a mixed phosphor layer to generate a full-spectrum white LED light source. The short-wavelength blue light has a small proportion and causes less damage to the retinal cells of the human eye, thereby realizing a healthy full-spectrum white LED light source with a high color rendering index.

[0005] To address the aforementioned technical problems, the first aspect of this invention 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 sequentially stacked, wherein...

[0006] 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 terminal quantum-well layer stacked sequentially. Each of the first multi-quantum-well layer, the second multi-quantum-well layer, the third multi-quantum-well layer, and the fourth terminal quantum-well layer comprises periodically alternating InGaN quantum-well layers and variable barrier height control layers. The variable barrier height control layer comprises five sub-layers stacked sequentially on the InGaN quantum-well layer: a first variable barrier control layer sub-layer, a second variable barrier control layer sub-layer, a third variable barrier control layer sub-layer, a fourth variable barrier control layer sub-layer, and a fifth variable barrier control layer sub-layer.

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

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

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

[0010] As an improvement to the above scheme, the first variable barrier control sublayer is a GaN layer, and the first variable barrier control sublayer is N-type doped or P-type doped; the second variable barrier control sublayer is Al. x Ga 1-x The N-layer, the second variable barrier control sublayer is not intentionally doped; the third variable barrier control sublayer is Al. w In z Ga 1-w-z The third variable barrier control sublayer is N-type doped or P-type doped; the fourth variable barrier control sublayer is Al. y Ga 1-yThe fourth variable barrier control layer sublayer is not intentionally doped; the fifth variable barrier control layer sublayer is a GaN layer, and the fifth variable barrier control layer sublayer is doped with N-type or P-type doping.

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

[0012] The growth thickness of the second variable barrier control layer sublayer is 0.2nm-2nm, the growth temperature of the second variable barrier control layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr.

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

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

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

[0016] As an improvement to the above scheme, the InGaN quantum well layer in the fourth quantum well layer is an InGaN layer that has undergone surface rough annealing treatment. The surface rough annealing treatment includes: after the InGaN layer is grown, a mixture of N2 and H2 gas is intermittently and cyclically introduced into the reaction chamber and stabilized for 5s-50s. The temperature of the surface rough annealing treatment is 820℃-1080℃, the pressure is 50torr-360torr, and the mixing ratio of N2 and H2 is 1:(0.2-3).

[0017] The third variable barrier control 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, 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 scheme, the first multi-quantum-well layer is a superlattice structure formed by a periodically alternating first InGaN quantum well layer and a first variable barrier height control layer, with a period number of 1-5; wherein, the first variable barrier height control layer includes a first GaN sublayer and an Al 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 multiple quantum well layer is a superlattice structure formed by a periodically alternating second InGaN quantum well layer and a second variable barrier height control layer, with a period number of 2-6; wherein, the second variable barrier height control layer includes a third GaN sublayer and an Al 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;

[0020] The third multiple quantum well layer is a superlattice structure formed by a periodically alternating third InGaN quantum well layer and a third variable barrier height control layer, with a period number of 2-5; wherein, the third variable barrier height control layer includes a fifth GaN sublayer and an Al 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, Al y3 Ga 1-y3 N-sublayer, sixth GaN sublayer;

[0021] The fourth final quantum well layer comprises a fourth InGaN quantum well layer and a fourth variable barrier height control layer stacked sequentially; wherein, the fourth variable barrier height control layer comprises a seventh GaN sublayer and an Al sublayer stacked sequentially 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.

[0022] As an improvement to the above scheme, the first GaN sublayer is N-type doped with a doping concentration of 1.8 × 10⁻⁶. 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 with a doping concentration of 1.3 × 10⁻⁶. 17 / cm 3 ~6.8×10 17 / cm 3 The second GaN sublayer is N-type doped with a doping concentration of 1.8 × 10⁻⁶. 17 / cm 3 ~8.7×10 17 / cm 3 ;

[0023] The third GaN sublayer is N-type doped with a doping concentration of 1.5 × 10⁻⁶. 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 with a doping concentration of 1.1 × 10⁻⁶. 17 / cm 3 ~6.0×10 17 / cm 3 The fourth GaN sublayer is N-type doped with a doping concentration of 1.5 × 10⁻⁶. 17 / cm 3 ~7.6×10 17 / cm 3 ;

[0024] The fifth GaN sublayer is N-type doped with a doping concentration of 1.2 × 10⁻⁶. 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 with a doping concentration of 0.8 × 10⁻⁶. 17 / cm 3 ~5.2×10 17 / cm 3The sixth GaN sublayer is N-type doped with a doping concentration of 1.2 × 10⁻⁶. 17 / cm 3 ~6.5×10 17 / cm 3 ;

[0025] The seventh GaN sublayer is p-type doped with a doping concentration of 1.8 × 10⁻⁶. 18 / cm 3 ~5.6×10 19 / cm 3 The Al w4 In z4 Ga 1-w4-z4 The N-sublayer is p-type doped with a doping concentration of 3.6 × 10⁻⁶. 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 × 10⁻⁶. 18 / cm 3 ~5.6×10 19 / cm 3 .

[0026] As an improvement to the above scheme, 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 scheme, 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 multilayer structures.

[0031] The first InGaN quantum well layer has an In content of 0.16-0.19 and a growth thickness of 2.0 nm-4.7 nm; the second InGaN quantum well layer has an In content of 0.13-0.16 and a growth thickness of 2.0 nm-4.7 nm; the third InGaN quantum well layer has an In content of 0.10-0.13 and a growth thickness of 2.0 nm-4.7 nm; and the fourth InGaN quantum well layer has an In content of 0.10-0.13 and a growth thickness of 2.0 nm-4.7 nm.

[0032] A second aspect of the present invention also provides a method for fabricating the epitaxial structure of the multi-band LED, comprising:

[0033] (1) Provide a substrate;

[0034] (2) A buffer layer is sequentially grown on the substrate;

[0035] (3) An N-type semiconductor layer is grown on the buffer layer;

[0036] (4) A low-temperature stress relief layer is grown on the N-type semiconductor layer;

[0037] (5) A multi-quantum well light-emitting layer is grown on the low-temperature stress relief layer;

[0038] (6) An electron blocking layer is grown on the multi-quantum-well light-emitting layer;

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

[0040] 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 terminal quantum-well layer stacked sequentially. Each of the first multi-quantum-well layer, the second multi-quantum-well layer, the third multi-quantum-well layer, and the fourth terminal quantum-well layer comprises periodically alternating InGaN quantum-well layers and variable-barrier height control layers. The variable-barrier height control layer comprises five sub-layers stacked sequentially on the InGaN quantum-well layer: a first variable-barrier control layer sub-layer, a second variable-barrier control layer sub-layer, a third variable-barrier control layer sub-layer, a fourth variable-barrier control layer sub-layer, and a fifth variable-barrier control layer sub-layer.

[0041] λ1>λ2>λ3, λ3=λ4.

[0042] Implementing this invention has the following beneficial effects:

[0043] The epitaxial structure of the multi-band LED chip in this application is used to form a multi-band LED chip. It generates a full-spectrum white LED light source by exciting a red and green mixed phosphor layer with three wavelength light sources. Compared with a blue LED chip with only one wavelength, it has a smaller proportion of short-wavelength blue light below 450nm, which causes less damage to human retinal cells. Moreover, its excitation light source has three wavelengths, and the generated full-spectrum white light is closer to the solar spectrum, thereby realizing a healthy full-spectrum white 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 quantum-well layer is λ4, where λ1 > λ2 > λ3 and λ3 = λ4. The epitaxial structure of the fabricated multi-band LED chip makes it easier to obtain high-quality multi-band multi-quantum-well emission layers, thereby improving the radiative recombination efficiency of the active region and further enhancing the luminous efficacy of the multi-band LED chip. Attached Figure Description

[0045] Figure 1 : A schematic diagram of the epitaxial structure of a multi-band LED in this invention;

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

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

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

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

[0050] Figure 6 : A schematic diagram of the structure of the fourth variable barrier height control barrier layer in this invention.

[0051] Figure label:

[0052] 100 - Substrate; 200 - Buffer layer; 300 - N-type semiconductor layer; 400 - Low-temperature stress relief 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 multiple quantum well layer; 521-Second InGaN quantum well layer; 522-Second variable barrier height control 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 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 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 Implementation

[0053] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described in further detail below.

[0054] In the description of this application, it is necessary to understand that the orientation or positional relationship indicated by terms such as "upper", "lower", "top", "bottom", "inner", and "outer" are based on the orientation or positional relationship shown in the accompanying drawings. They are intended only to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the components referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0055] To address the aforementioned problems, the first aspect of this invention provides an epitaxial structure for a multi-band LED. (See attached document.) Figure 1 The system includes a substrate 100, a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress relief layer 400, a multi-quantum well light-emitting layer 500, an electron blocking layer 600, and a P-type semiconductor layer 700, which are stacked sequentially. 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, which are stacked sequentially, with a period number of 6-19.

[0056] Wherein, the emission wavelength of the first quantum well layer 510 is λ1, the emission wavelength of the second quantum well layer 520 is λ2, the emission wavelength of the third quantum well layer 530 is λ3, and the emission wavelength of the fourth 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, such that the first quantum well layer 510 is a long-wavelength blue quantum well layer, the second quantum well layer 520 is a mid-wavelength blue quantum well layer, the third quantum well layer 530 is a short-wavelength blue quantum well layer, and the fourth quantum well layer 540 is a short-wavelength blue quantum well layer.

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

[0058] Furthermore, the band barrier height of the first multi-quantum well layer 510 is φ1, the band barrier height of the second multi-quantum well layer 520 is φ2, the band barrier height of the third multi-quantum well layer 530 is φ3, and the band barrier height of the fourth final quantum well layer 540 is φ4, where φ1 > φ4, φ4 > φ2, and φ2 > φ3, forming a first high-barrier long-wavelength blue light multi-quantum well layer, a second low-barrier mid-wavelength blue light multi-quantum well layer, a third low-barrier short-wavelength blue light multi-quantum well layer, and a fourth mid-barrier short-wavelength blue light final quantum well layer stacked sequentially. The multi-quantum-well emitting layer 500 is typically prepared by low-temperature deposition at 650℃-935℃. As the deposition thickness increases, the crystal quality and surface smoothness of the deposited epitaxial film material deteriorate. In addition, the In content of the InGaN material in the quantum well layer with longer emission wavelength is relatively higher, resulting in greater mismatch stress due to well-barrier mismatch and more defects. Furthermore, the growth temperature of the high-In-content InGaN material is lower, further increasing the defects in the grown epitaxial film. Therefore, the growth sequence of the multi-wavelength multi-quantum-well emitting layer 500 is preferably designed to first deposit and grow long-wavelength quantum wells and then deposit and grow short-wavelength quantum wells. The resulting epitaxial structure of the multi-wavelength LED chip is more likely to obtain a high-quality multi-wavelength multi-quantum-well emitting layer 500, thereby improving the radiative recombination efficiency of the active region and further improving the luminous efficacy of the multi-wavelength 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 quantum well layer 540 each include periodically alternating layers of InGaN quantum well layers and variable barrier height control layers. The variable barrier height control layer includes five sub-layers stacked sequentially on the InGaN quantum well layer: the first variable barrier control layer sub-layer, the second variable barrier control layer sub-layer, the third variable barrier control layer sub-layer, the fourth variable barrier control layer sub-layer, and the fifth variable barrier control layer sub-layer.

[0060] The first variable barrier control sublayer is a GaN layer, and it is doped with either N-type or P-type doping; the second variable barrier control sublayer is an Al layer. x Ga 1-x The N-layer, the second variable barrier control sublayer is not intentionally doped; the third variable barrier control sublayer is Al. w In z Ga 1-w-z The third variable barrier control sublayer is N-type doped or P-type doped; the fourth variable barrier control sublayer is Al. y Ga 1-yThe fourth variable barrier control layer sublayer is not intentionally doped; the fifth variable barrier control layer sublayer is a GaN layer, and the fifth variable barrier control layer sublayer is doped with N-type or P-type doping.

[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, third, and fifth variable barrier control sublayers are N-type doped; in the fourth final quantum well layer 540, the first, third, and fifth variable barrier control sublayers are P-type doped. This allows for the provision of some electrons and holes to the luminescent quantum well region to participate in radiative recombination luminescence, thereby improving the matching degree of electron-hole concentration in the luminescent quantum well region and thus enhancing 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 control layer sublayer is 0.6nm-6nm; the growth thickness of the second variable barrier control layer sublayer is 0.2nm-2nm; the growth thickness of the third variable barrier control layer sublayer is 0.5nm-6nm; the growth thickness of the fourth variable barrier control layer sublayer is 0.2nm-2nm; and the growth thickness of the fifth variable barrier control layer sublayer is 0.6nm-6nm.

[0063] Furthermore, the Al in the third multiple quantum well layer 530 x Ga 1-x The Al composition of the N layer is less than that of the Al in the second quantum well layer 520. x Ga 1-x The Al composition percentage in the N-layer, and the Al content in the second multiple quantum well layer 520 x Ga 1- x The proportion of Al component in the N layer is less than that in the fourth final quantum well layer 540. x Ga 1-x The Al composition percentage in the N-layer, and the Al content in the fourth final quantum well layer 540 x Ga 1-x The Al component content of the N layer is less than that of the Al component in the first multi-quantum-well layer 510. x Ga 1-x The Al composition percentage in the N-layer, and the Al content in the third multiple quantum well layer 530 y Ga 1-y The Al composition of the N layer is less than that of the Al in the second quantum well layer 520. y Ga 1-yThe Al composition percentage in the N-layer, and the Al content in the second multiple quantum well layer 520 y Ga 1-y The proportion of Al component in the N layer is less than that in the fourth final quantum well layer 540. y Ga 1-y The Al composition percentage in the N-layer, and the Al content in the fourth final quantum well layer 540 y Ga 1-y The Al component content of the N layer is less than that of the Al component in the first multi-quantum-well layer 510. y Ga 1-y The proportion of Al composition in the N layer is such that φ1 > φ4, φ4 > φ2, and φ2 > φ3. This forms a multilayer structure in the variable barrier height control barrier layer of the multi-quantum well light-emitting layer 500, in which a high barrier layer, a low barrier layer, and a medium barrier layer are stacked sequentially. The barrier layer design of this structure and process can effectively confine the charge carrier electrons and holes in the region of the multi-quantum well light-emitting layer 500, thereby improving the matching degree of electron and hole concentration in the light-emitting quantum well region and improving the luminous efficiency of the multi-band LED chip.

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

[0065] This invention controls the band barrier height and resistance value of the multi-quantum-well light-emitting layer 500 by adjusting the variable barrier height, material composition ratio, material doping type, and doping concentration in the barrier layer. This allows for the control of the current expansion performance of the epitaxial structure and improves the hole injection efficiency of the P-type semiconductor material. Ultimately, this achieves the goal of controlling the electron-hole concentration distribution in the multi-quantum-well light-emitting layer 500, thereby improving the luminous efficacy of multi-band LED chips.

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

[0067] For example, 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 surface roughening annealing treatment temperature 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 cyclical introduction of the mixed gas of N2 and H2 and stabilization for 5s-50s means that after each gas introduction, the introduction is paused and the conditions inside the chamber are kept unchanged for a duration of 5s-50s.

[0068] Furthermore, the third variable barrier control 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 poor crystal quality parts and high In content In clusters on the material surface, which is beneficial to improving the crystal quality of the AlInGaN layer. At the same time, the rough material surface can reduce the in-plane total internal reflection and light absorption loss of photons in the semiconductor material, improve the light extraction efficiency, and further improve the luminous efficacy of multi-band LED chips.

[0069] For example, the third variable barrier control 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 includes: after the AlInGaN layer has grown, intermittently and cyclically introducing a mixed gas of N2 and H2 into the reaction chamber and stabilizing it for 10s-100s. The surface roughening annealing treatment temperature is 820℃-1080℃, the pressure is 50 torr-360 torr, and the mixing ratio of N2 and H2 is 1:(0.5-6). It can be understood that the intermittently and cyclically introducing the mixed gas of N2 and H2 and stabilizing it for 10s-100s means that after each gas introduction, the introduction is paused and the conditions inside the chamber remain unchanged for a duration of 10s-100s.

[0070] For some specific implementation methods, please refer to Figures 2-6 The first multi-quantum-well layer 510 is a superlattice structure formed by a periodically alternating first InGaN quantum well layer 511 and a first variable barrier height control layer 512, with a period number of 1-5; wherein, the first variable barrier height control layer 512 includes a first GaN sublayer 5121 and an Al sublayer 5121 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, second GaN sublayer 5125.

[0071] The second multiple quantum well layer 520 is a superlattice structure of a periodically alternating second InGaN quantum well layer 521 and a second variable barrier height control layer 522, with a period number of 2-6; wherein, the second variable barrier height control layer 522 includes a third GaN sublayer 5221 and an Al sublayer 5221 sequentially stacked 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, fourth GaN sublayer 5225.

[0072] The third multi-quantum well layer 530 is a superlattice structure consisting of a periodically alternating third InGaN quantum well layer 531 and a third variable barrier height control layer 532, with a period number of 2-5; wherein, the third variable barrier height control layer 532 comprises a fifth GaN sublayer 5321 and an Al sublayer 5321 sequentially stacked on the third InGaN quantum well layer 531. 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, sixth GaN sublayer 5325.

[0073] The fourth quantum well layer 540 is a superlattice structure consisting of a periodically alternating fourth InGaN quantum well layer 541 and a fourth variable barrier height control layer 542, with a period number of 1-3; wherein, the fourth variable barrier height control layer 542 comprises a seventh GaN sublayer 5421 and an Al sublayer 5421 sequentially stacked on the fourth InGaN quantum well layer 541. 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, eighth GaN sublayer 5425.

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

[0075] Preferably, the Al x3 Ga 1-x3 The Al component percentage of N sublayer 5322 is less than that of Al. x2 Ga 1-x2 The Al composition ratio of the N sublayer 5222 is x2, wherein the Al x2 Ga 1-x2 The Al component percentage (x2) of the N sublayer 5222 is less than that of Al. x4 Ga 1-x4The Al composition of the N sublayer 5422 is x4, and the Al x4 Ga 1-x4 The Al component percentage of N sublayer 5422 x4 is less than that of Al. x1 Ga 1-x1 The Al composition ratio of the N sublayer 5122 is x1, i.e., x3 < x2 < x4 < x1, where Al y3 Ga 1-y3 The Al component percentage y3 in the N sublayer 5324 is less than that in the Al y2 Ga 1- y2 The Al composition percentage y2 of the N sublayer 5224, wherein Al y2 Ga 1-y2 The Al component percentage y2 of the N sublayer 5224 is less than that of the Al y4 Ga 1-y4 The Al composition percentage of the N sublayer 5424 is y4, wherein the Al y4 Ga 1-y4 The Al component percentage y4 in the N sublayer 5424 is less than that in the Al y1 Ga 1-y1 The proportion of Al component in the N sublayer 5124 is y1, i.e., y3 < y2 < y4 < y1.

[0076] For example, 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 percentage w1 of the N sublayer 5123 is greater than that of the Al w2 In z2 Ga 1-w2- z2 The Al composition percentage w2 of the N sublayer 5223, wherein Al w1 In z1 Ga 1-w1-z1 The Al component percentage w1 of the N sublayer 5123 is greater than that of the Al w3 In z3 Ga 1-w3-z3 The Al component ratio of the N sublayer 5323 is w3, i.e., w1 > w2, w1 > w3, the Al w4 In z4 Ga 1-w4-z4 The In composition ratio z4 of the N sublayer 5423 is greater than that of the Al. w2 In z2 Ga1-w2-z2 The In composition percentage z2 of the N sublayer 5223, the Al w4 In z4 Ga 1-w4-z4 The In composition ratio z4 of the N sublayer 5423 is greater than that of the Al. w3 In z3 Ga 1-w3-z3 The proportion of In component in the N sublayer 5323 is z3, i.e., 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-sublayer 5323 is an AlInGaN layer with low Al and low In composition. 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] For example, 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 The wavelength range is 0.6nm-6nm, and the Al... x1 Ga 1-x1 The growth thickness H of the N sublayer 5122 12 The wavelength is 0.2nm-2nm, and the Al w1 In z1 Ga 1-w1-z1 The growth thickness H of the N sublayer 5123 13 The wavelength range is 0.5nm-6nm, and 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 The range is 0.6nm-6nm.

[0080] Preferably, in the second multiple quantum well layer 520, the growth thickness H of the third GaN sublayer 5221 is...21 The wavelength range is 0.6nm-6nm, and the Al... x2 Ga 1-x2 The growth thickness H of the N sublayer 5222 22 The wavelength is 0.2nm-2nm, and the Al w2 In z2 Ga 1-w2-z2 The growth thickness H of the N sublayer 5223 23 The wavelength range is 0.5nm-6nm, and 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 The range 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 The wavelength range is 0.6nm-6nm, and the Al... x3 Ga 1-x3 The growth thickness H of the N sublayer 5322 32 The wavelength is 0.2nm-2nm, and the Al w3 In z3 Ga 1-w3-z3 The growth thickness H of the N sublayer 5323 33 The wavelength range is 0.5nm-6nm, and 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 The range 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 The wavelength range is 0.6nm-6nm, and the Al... x4 Ga 1-x4 The growth thickness H of the N sublayer 5422 42 The wavelength is 0.2nm-2nm, and the Al w4 In z4 Ga 1-w4-z4 The growth thickness H of the N sublayer 5423 43 The wavelength range is 0.5nm-6nm, and 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 The range is 0.6nm-6nm.

[0083] Understandable, i.e., H 11 H 21 H 31 H 41 They can be equal or unequal, H 12 H 22 H 32 H 44 They can be equal or unequal, H 13 H 23 H 33 H 43 They can be equal or unequal, H 14 H 24 H 34 H 44 They can be equal or unequal, H 15 H 25 H 35 H 45 They can be equal or unequal.

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

[0085] (1) Provide a substrate 100;

[0086] (2) A buffer layer 200 is sequentially grown on the substrate 100;

[0087] (3) An N-type semiconductor layer 300 is grown on the buffer layer 200;

[0088] (4) A low-temperature stress relief layer 400 is grown on the N-type semiconductor layer 300;

[0089] (5) A multi-quantum-well light-emitting layer 500 is grown on the low-temperature stress-relieving layer 400. 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 sequentially. 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 each include periodically alternating InGaN quantum-well layers and variable barrier height control layers. The variable barrier height control layer includes five sub-layers stacked sequentially on the InGaN quantum-well layer: a first variable barrier control layer sub-layer, a second variable barrier control layer sub-layer, a third variable barrier control layer sub-layer, a fourth variable barrier control layer sub-layer, and a fifth variable barrier control layer sub-layer; λ1 > λ2 > λ3, λ3 = λ4.

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

[0091] (7) A P-type semiconductor layer 700 is grown 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℃-929℃, and the growth pressure is 50 torr-360 torr; the growth temperature of the first GaN sublayer 5121 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the Al x1 Ga 1-x1 The growth temperature of the N sublayer 5122 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the Al w1 In z1 Ga 1-w1-z1 The growth temperature of the N sublayer 5123 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the Al y1 Ga 1-y1 The growth temperature of the N sublayer 5124 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the growth temperature of the second GaN sublayer 5125 is 825℃-938℃, and the growth pressure is 50 torr-360 torr.

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

[0094] Preferably, in the third multiple quantum well layer 530, the growth temperature of the third InGaN quantum well layer 531 is 790℃-929℃, and the growth pressure is 50 torr-360 torr; the growth temperature of the fifth GaN sublayer 5321 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the Al x3 Ga 1-x3 The growth temperature of the N sublayer 5322 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the Al w3 In z3 Ga 1-w3-z3 The growth temperature of the N sublayer 5323 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the Al y3 Ga 1-y3 The growth temperature of the N sublayer 5324 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the growth temperature of the sixth GaN sublayer 5325 is 825℃-938℃, 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℃-929℃, and the growth pressure is 50 torr-360 torr; the growth temperature of the seventh GaN sublayer 5421 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the Al x4 Ga 1-x4 The growth temperature of the N sublayer 5422 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the Al w4 In z4 Ga 1-w4-z4 The growth temperature of the N sublayer 5423 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the Al y4 Ga 1-y4 The growth temperature of the N sublayer 5424 is 825℃-938℃, and the growth pressure is 50 torr-360 torr; the growth temperature of the eighth GaN sublayer 5425 is 825℃-938℃, and the growth pressure is 50 torr-360 torr.

[0096] It is 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 relief layer 400, the electron blocking layer 600, and the P-type semiconductor layer 700 are all grown using existing processes and materials, and will not be further described in this embodiment.

[0097] The present invention will be further described below with reference to 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 sequentially. 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 quantum-well layer stacked sequentially.

[0100] The first multi-quantum-well layer is a superlattice structure formed by periodically alternating first InGaN quantum well layers and a first variable-barrier height control layer, with a period number of 3; wherein, the first variable-barrier height control layer includes a first GaN sublayer and an Al 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 content 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 × 10⁻⁶. 17 / cm 3 Growth thickness H 11 =3.3nm; the Al x1 Ga 1-x1 The N-sublayer is an unintentionally doped AlGaN layer with x1 = 0.05 and a growth thickness 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 × 10⁻⁶. 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 with y1 = 0.05 and a growth thickness 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 multiple quantum well layer is a superlattice structure formed by a periodically alternating second InGaN quantum well layer and a second variable barrier height control layer, with a period number of 4; wherein, the second variable barrier height control layer includes a third GaN sublayer and an Al 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 second InGaN quantum well layer has an In content of 0.15% and a growth thickness of 3.4 nm; the third GaN sublayer is N-type doped with a doping concentration of 4.5 × 10⁻⁶. 17 / cm 3 Growth thickness H 21 =3.3nm; the Al x2 Ga 1-x2 The N-sublayer is an unintentionally doped AlGaN layer with x2 = 0.05 and a growth thickness 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 × 10⁻⁶. 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 with y² = 0.05 and a growth thickness H. 24 =1.1nm, the fourth GaN sublayer is N-type doped with a doping concentration of 4.5×10⁻⁶. 17 / cm 3 Growth thickness H 25 =3.3nm;

[0104] The third multiple quantum well layer is a superlattice structure formed by a periodically alternating third InGaN quantum well layer and a third variable barrier height control layer, with a period number of 3; wherein, the third variable barrier height control layer includes a fifth GaN sublayer and an Al 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 431 nm;

[0105] The third InGaN quantum well layer has an In content of 0.11 and a growth thickness of 3.4 nm; the fifth GaN sublayer is N-type doped with a doping concentration of 3.8 × 10⁻⁶. 17 / cm 3 Growth thickness H 31 =3.3nm; the Al x3 Ga 1-x3 The N-sublayer is an unintentionally doped AlGaN layer with x3 = 0.05 and a growth thickness 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 × 10⁻⁶. 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 with y3 = 0.05 and a growth thickness H. 34 =1.1nm, the sixth GaN sublayer is N-type doped with a doping concentration of 3.8×10⁻⁶. 17 / cm 3 Growth thickness H 35 =3.3nm;

[0106] The fourth final quantum well layer comprises a fourth InGaN quantum well layer and a fourth variable barrier height control layer stacked sequentially; wherein, the fourth variable barrier height control layer comprises a seventh GaN sublayer and an Al sublayer stacked sequentially 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 fourth InGaN quantum well layer has an In content of 0.12 and a growth thickness of 3.4 nm; the seventh GaN sublayer is N-type doped with a doping concentration of 1 × 10⁻⁶. 19 / cm 3 Growth thickness H 41 =3.3nm; the Al x4 Ga1-x4 The N-sublayer is an unintentionally doped AlGaN layer with x4 = 0.05 and a growth thickness 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 × 10⁻⁶. 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 with y4 = 0.05 and a growth thickness H. 44 =1.1nm, the eighth GaN sublayer is N-type doped with a doping concentration of 1×10⁻⁶. 19 / cm 3 Growth thickness H 45 =3.3nm.

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

[0109] (1) Provide a substrate;

[0110] (2) A buffer layer is sequentially grown on the substrate;

[0111] (3) An N-type semiconductor layer is grown on the buffer layer;

[0112] (4) A low-temperature stress relief layer is grown on the N-type semiconductor layer;

[0113] (5) A multi-quantum well light-emitting layer is grown on the low-temperature stress relief layer, wherein 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 quantum well layer stacked sequentially.

[0114] (6) An electron blocking layer is grown on the multi-quantum-well light-emitting layer;

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

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

[0117] The second InGaN quantum well layer was grown at a temperature of 850°C and a growth pressure of 200 torr; the third GaN sublayer was grown at a temperature of 880°C and a growth pressure of 200 torr; the Al... x2 Ga 1-x2 The growth temperature of the N sublayer is 880℃, 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℃, and the growth pressure is 200 torr; the Al y2 Ga 1-y2 The growth temperature of the N sublayer is 880℃, and the growth pressure is 200 torr; the growth temperature of the fourth GaN sublayer is 880℃, and the growth pressure is 200 torr.

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

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

[0120] Example 2

[0121] This embodiment provides an epitaxial structure for a multi-band LED, which is basically the same as that in Embodiment 1, except that:

[0122] The seventh GaN sublayer is p-type doped with a doping concentration of 1×10⁻⁶. 19 / cm 3 Growth thickness H 41 =3.3nm; the Al w4 In z4 Ga 1-w4-z4 The N-sublayer is p-type doped with a doping concentration of 2 × 10⁻⁶. 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 1×10⁻⁶. 19 / cm 3 Growth thickness H 45 =3.3nm.

[0123] Example 3

[0124] This embodiment provides an epitaxial structure for a multi-band LED, which is basically the same as that in 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 for a multi-band LED, which is basically the same as that in 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 for a multi-band LED, which is basically the same as that in Embodiment 4, except that:

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

[0132] Example 6

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

[0134] The Al w4 In z4 Ga 1-w4-z4 The N-sublayer is an AlInGaN layer that has undergone surface roughening annealing treatment. The surface roughening annealing treatment includes: [details of the surface roughening annealing process]. w4 In z4 Ga 1-w4-z4 After the N sublayer is grown, a mixture of N2 and H2 gas is intermittently and circulated into the reaction chamber and stabilized for 50 seconds. The surface roughening annealing treatment is carried out at a temperature of 950°C and a pressure of 210 torr, with a N2 to H2 mixing ratio of 1:3.

[0135] Comparative Example 1

[0136] This comparative example provides an epitaxial structure for a multi-band LED, which is basically the same as that in 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, all with a light emission wavelength of 452 nm.

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

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

[0140] 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] As can be seen from the above results, after the epitaxial structure of the multi-band LED in this application forms an LED chip, a full-spectrum white LED light source is generated by exciting the red and green mixed phosphor layer with three wavelength light sources. The generated full-spectrum white light is closer to the solar spectrum, thereby realizing a healthy full-spectrum white LED light source with a high color rendering index, and also improving the luminous efficiency of the multi-band LED chip.

[0142] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. An epitaxial structure for a multi-band LED, characterized in that, It includes 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, which are stacked sequentially. 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 terminal quantum-well layer stacked sequentially. Each of the first multi-quantum-well layer, the second multi-quantum-well layer, the third multi-quantum-well layer, and the fourth terminal quantum-well layer comprises periodically alternating InGaN quantum-well layers and variable barrier height control layers. The variable barrier height control layer comprises five sub-layers stacked sequentially on the InGaN quantum-well layer: a first variable barrier control layer sub-layer, a second variable barrier control layer sub-layer, a third variable barrier control layer sub-layer, a fourth variable barrier control layer sub-layer, and a fifth variable barrier control layer sub-layer. The emission wavelength of the first quantum well layer is λ1, the emission wavelength of the second quantum well layer is λ2, the emission wavelength of the third quantum well layer is λ3, and the emission wavelength of the fourth quantum well layer is λ4, where λ1 > λ2 > λ3 and λ3 = λ4. The band barrier height of the first quantum well layer is φ1, the band barrier height of the second quantum well layer is φ2, the band barrier height of the third quantum well layer is φ3, and the band barrier height of the fourth quantum well layer is φ4, where φ1 > φ4, φ4 > φ2, and φ2 > φ3. The λ1 is 460nm-480nm, the λ2 is 445nm-460nm, the λ3 is 430nm-445nm, and the λ4 is 430nm-445nm. The first variable barrier control layer sublayer is a GaN layer; the second variable barrier control layer sublayer is an Al layer. x Ga 1-x The N-layer, the second variable barrier control sublayer is not intentionally doped; the third variable barrier control sublayer is Al. w In z Ga 1-w-z N layers; the fourth variable potential barrier control layer sublayer is Al. y Ga 1-y The N-layer, the fourth variable barrier control layer sublayer is not intentionally doped; the fifth variable barrier control layer sublayer is a GaN layer; in the first, second, and third multiple quantum well layers, the first, third, and fifth variable barrier control layer sublayers are N-type doped; in the fourth final quantum well layer, the first, third, and fifth variable barrier control layer sublayers are P-type doped.

2. The epitaxial structure of a multi-band LED as described in claim 1, characterized in that, The growth thickness of the first variable barrier control layer sublayer is 0.6nm-6nm, the growth temperature of the first variable barrier control layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr. The growth thickness of the second variable barrier control layer sublayer is 0.2nm-2nm, the growth temperature of the second variable barrier control layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr. The growth thickness of the third variable barrier control layer sublayer is 0.5nm-6nm, the growth temperature of the third variable barrier control layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr. The growth thickness of the fourth variable barrier control layer sublayer is 0.2nm-2nm, the growth temperature of the fourth variable barrier control layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr. The growth thickness of the fifth variable barrier control layer sublayer is 0.6nm-6nm, the growth temperature of the fifth variable barrier control layer sublayer is 825℃-938℃, and the growth pressure is 50torr-360torr.

3. The epitaxial structure of a multi-band LED as described in claim 1, characterized in that, The InGaN quantum well layer in the fourth quantum well layer is an InGaN layer that has undergone surface roughening annealing. The surface roughening annealing process includes: after the InGaN layer has grown, intermittently and cyclically introducing a mixture of N2 and H2 into the reaction chamber and stabilizing it for 5s-50s. The temperature of the surface roughening annealing process is 820℃-1080℃, the pressure is 50torr-360torr, and the mixing ratio of N2 and H2 is 1:(0.2-3). The third variable barrier control 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, 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).

4. The epitaxial structure of a multi-band LED as described in claim 1, characterized in that, The first multi-quantum-well layer is a superlattice structure formed by periodically alternating first InGaN quantum well layers and a first variable-barrier height control layer, with a period number of 1-5; wherein, the first variable-barrier height control layer includes a first GaN sublayer and an Al 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 multiple quantum well layer is a superlattice structure formed by a periodically alternating second InGaN quantum well layer and a second variable barrier height control layer, with a period number of 2-6; wherein, the second variable barrier height control layer includes a third GaN sublayer and an Al 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; The third multiple quantum well layer is a superlattice structure formed by a periodically alternating third InGaN quantum well layer and a third variable barrier height control layer, with a period number of 2-5; wherein, the third variable barrier height control layer includes a fifth GaN sublayer and an Al 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, Al y3 Ga 1-y3 N-sublayer, sixth GaN sublayer; The fourth final quantum well layer comprises a fourth InGaN quantum well layer and a fourth variable barrier height control layer stacked sequentially; wherein, the fourth variable barrier height control layer comprises a seventh GaN sublayer and an Al sublayer stacked sequentially 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.

5. The epitaxial structure of a multi-band LED as described in claim 4, characterized in that, The first GaN sublayer is N-type doped with a doping concentration of 1.8 × 10⁻⁶. 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 with a doping concentration of 1.3 × 10⁻⁶. 17 / cm 3 ~6.8×10 17 / cm 3 The second GaN sublayer is N-type doped with a doping concentration of 1.8 × 10⁻⁶. 17 / cm 3 ~8.7×10 17 / cm 3 ; The third GaN sublayer is N-type doped with a doping concentration of 1.5 × 10⁻⁶. 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 with a doping concentration of 1.1 × 10⁻⁶. 17 / cm 3 ~6.0×10 17 / cm 3 The fourth GaN sublayer is N-type doped with a doping concentration of 1.5 × 10⁻⁶. 17 / cm 3 ~7.6×10 17 / cm 3 ; The fifth GaN sublayer is N-type doped with a doping concentration of 1.2 × 10⁻⁶. 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 with a doping concentration of 0.8 × 10⁻⁶. 17 / cm 3 ~5.2×10 17 / cm 3 The sixth GaN sublayer is N-type doped with a doping concentration of 1.2 × 10⁻⁶. 17 / cm 3 ~6.5×10 17 / cm 3 ; The seventh GaN sublayer is p-type doped with a p-type doping concentration of 1.8 × 10⁻⁶. 18 / cm 3 ~5.6×10 19 / cm 3 The Al w4 In z4 Ga 1-w4-z4 The N-sublayer is p-type doped with a p-type doping concentration of 3.6 × 10⁻⁶. 18 / cm 3 ~7.8×10 19 / cm 3 The eighth GaN sublayer is p-type doped with a p-type doping concentration of 1.8 × 10⁻⁶. 18 / cm 3 ~5.6×10 19 / cm 3 .

6. The epitaxial structure of a multi-band LED as described in claim 4, characterized in that, 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.

7. The epitaxial structure of a multi-band LED as described in claim 4, characterized in that, 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 multilayer structures. The first InGaN quantum well layer has an In content of 0.16-0.19 and a growth thickness of 2.0 nm-4.7 nm; the second InGaN quantum well layer has an In content of 0.13-0.16 and a growth thickness of 2.0 nm-4.7 nm; the third InGaN quantum well layer has an In content of 0.10-0.13 and a growth thickness of 2.0 nm-4.7 nm; and the fourth InGaN quantum well layer has an In content of 0.10-0.13 and a growth thickness of 2.0 nm-4.7 nm.

8. A method for fabricating an epitaxial structure of a multi-band LED as described in any one of claims 1-7, characterized in that, include: (1) Provide a substrate; (2) A buffer layer is sequentially grown on the substrate; (3) An N-type semiconductor layer is grown on the buffer layer; (4) A low-temperature stress relief layer is grown on the N-type semiconductor layer; (5) A multi-quantum-well light-emitting layer is grown on the low-temperature stress-relieving layer; (6) An electron blocking layer is grown on the multi-quantum-well light-emitting layer; (7) A P-type semiconductor layer is grown on the electron blocking layer.

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