A multi-band light emitting diode epitaxial structure and a preparation method thereof

Abstract

The present application relates to the technical field of semiconductor devices, and particularly relates to a multi-band light emitting diode epitaxial structure and a preparation method thereof.The multi-band light emitting diode epitaxial structure comprises, from bottom to top, 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 four sub-layers, which are stacked from bottom to top as follows: a first long-wave cyan light multi-quantum well layer, a second short-wave cyan light multi-quantum well layer, a third long-wave blue light multi-quantum well layer and a fourth short-wave blue light multi-quantum well layer, and the light emitting wavelengths decrease in turn.Combining the design of the sub-layers of the multi-quantum well light emitting layer, the overall excitation efficiency can be improved through the synergistic effect of the light of each band, full-spectrum white light can be output, the light emitting efficiency is high, the color rendering is good, the stability is better, and the harm to the human eye is small.

Description

Technical Field

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

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

[0003] White light LED devices currently on the market typically utilize fluorescent glue coated on a blue LED chip to produce white light. However, the spectral curve of such full-spectrum white light LED sources exhibits significant fluctuations in the blue wavelength band, resulting in poor stability. Furthermore, as early as 1966, Nell et al. discovered that exposure to blue light can damage retinal cells, leading to decreased vision and even loss. Short-wavelength blue light, with a wavelength between 400 and 450 nanometers, poses the greatest risk 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. Blue light exposure to 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 impairment.

[0004] Therefore, the existing full-spectrum white light LED light sources still need to be optimized. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a multi-band light emitting diode epitaxial structure and a preparation method thereof, and a white light LED light source.

[0006] By targeting the shortcomings of current full-spectrum white light LED light sources, we have further optimized and studied the structure and process of blue light LED chips, hoping 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.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect of the present invention, a multi-band light-emitting diode epitaxial structure is provided, which comprises, from bottom to top, 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.

[0009] The multi-quantum well light-emitting layer comprises a first long-wave cyan multi-quantum well layer, a second short-wave cyan multi-quantum well layer, a third long-wave blue multi-quantum well layer and a fourth short-wave blue multi-quantum well layer, which are sequentially stacked from bottom to top;

[0010] The emission wavelengths of the first long-wave cyan multi-quantum well layer, the second short-wave cyan multi-quantum well layer, the third long-wave blue multi-quantum well layer, and the fourth short-wave blue multi-quantum well layer decrease in sequence;

[0011] The first long-wave cyan multi-quantum well layer, the second short-wave cyan multi-quantum well layer, the third long-wave blue multi-quantum well layer, and the fourth short-wave blue multi-quantum well layer all include four sublayers stacked and grown in sequence from bottom to top: an N-polarity well front insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity well back insertion layer, and a Ga-polarity light-emitting quantum barrier layer.

[0012] In some embodiments, the first long-wave cyan multi-quantum well layer emits light in a wavelength range of 490 nm to 500 nm, the second short-wave cyan multi-quantum well layer emits light in a wavelength range of 480 nm to 490 nm, the third long-wave blue multi-quantum well layer emits light in a wavelength range of 445 nm to 480 nm, and the fourth short-wave blue multi-quantum well layer emits light in a wavelength range of 430 nm to 445 nm.

[0013] In some embodiments, the period range of the alternating growth of the four sublayers in the first long-wave cyan light multi-quantum well layer is: 1~3, the period range of the alternating growth of the four sublayers in the second short-wave cyan light multi-quantum well layer is: 1~3, the period range of the alternating growth of the four sublayers in the third long-wave blue light multi-quantum well layer is: 2~6, and the period range of the alternating growth of the four sublayers in the fourth short-wave blue light multi-quantum well layer is: 2~5.

[0014] In some embodiments, the N-polarity pre-well insertion layer includes an N-polarity low In component InGaN layer, an N-polarity first graded AlGaN layer, and an N-polarity first graded InGaN layer, which are sequentially stacked from bottom to top; wherein the N-polarity low In component InGaN layer is a single layer or multilayer structure of a low In component N-polarity InGaN lowly doped with Si element; the N-polarity first graded AlGaN layer is an N-polarity AlGaN material with an increasing Al component from bottom to top, and the AlGaN material is not intentionally doped; the N-polarity first graded InGaN layer is an N-polarity InGaN material with an increasing In component from bottom to top, and the InGaN material is not intentionally doped,

[0015] The Ga-polarity light-emitting quantum well layer is a single or multilayer structure of Ga-polarity InGaN with a high In content that is not intentionally doped;

[0016] The N-polarity post-well insertion layer comprises an N-polarity second graded InGaN layer, an N-polarity second graded AlGaN layer, and an N-polarity non-doped GaN layer, which are sequentially stacked and grown from bottom to top; wherein the N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In component from bottom to top, and the InGaN material is not intentionally doped; the N-polarity second graded AlGaN layer is an N-polarity AlGaN material with a decreasing Al component from bottom to top, and the AlGaN material is not intentionally doped; the N-polarity non-doped GaN layer is an N-polarity GaN single layer or multilayer structure that is not intentionally doped;

[0017] The Ga-polarity light-emitting quantum barrier layer is a Ga-polarity GaN single layer or multilayer structure low in Si doping;

[0018] The Al component content of the N-polarity first graded AlGaN layer is greater than or equal to the Al component content of the N-polarity second graded AlGaN layer.

[0019] In some embodiments, in the N-polarity front well insertion layer, the In component content of the N-polarity low In component InGaN layer is 0 to 0.03, the growth thickness does not exceed 0.5 nm, and the Si doping concentration is 1.18×10 17 / cm 3 ~6.79×10 17 / cm 3 ; The Al component content in the N-polarity first gradient AlGaN layer is 0.01 ~ 0.16, and the growth thickness does not exceed 0.7nm; the In component content in the N-polarity first gradient InGaN layer is 0~0.21, and the growth thickness does not exceed 0.9nm.

[0020] In some embodiments, in the N-polarity rear well insertion layer, the In component content in the N-polarity second gradient InGaN layer is 0~0.21, and the growth thickness does not exceed 0.9nm; the Al component content in the N-polarity second gradient AlGaN layer is 0~0.12, and the growth thickness does not exceed 0.7nm; the growth thickness of the N-polarity non-doped GaN layer does not exceed 0.5nm.

[0021] In some embodiments, the Al component content of the N-polarity first graded AlGaN layer is 0.01≤X 11 ≤0.05 increasing to 0.06≤X 12 ≤0.16; the Al component content of the N-polarity second graded AlGaN layer is 0.05≤X 21≤0.12 decreasing to 0≤X 22 ≤0.03;X 21 ≤X 12 , X 22 ≤X 11 .

[0022] In some embodiments, in the first long-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer is 0≤Y 11 ≤0.10 increasing to 0.15≤Y 12 ≤0.21, the In component content of the N-polarity second graded InGaN layer is 0.15≤Y 13 ≤0.21 decreasing to 0≤Y 14 ≤0.10;

[0023] In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer is 0≤Y 21 ≤0.09 increasing to 0.13≤Y 22 ≤0.20, the In component content in the N-polarity second graded InGaN layer is 0.13≤Y 23 ≤0.20 decreasing to 0≤Y 24 ≤0.09;

[0024] In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity first gradient InGaN layer is 0≤Y 31 ≤0.08 increasing to 0.11≤Y 32 ≤0.19, the In component content in the N-polarity second graded InGaN layer is 0.11≤Y 33 ≤0.19 decreasing to 0≤Y 34 ≤0.08;

[0025] In the fourth short-wave blue multi-quantum well layer, the In component content in the N-polarity first gradient InGaN layer is 0≤Y 41 ≤0.07 increasing to 0.09≤Y 42 ≤0.13, the In component content in the N-polarity second graded InGaN layer is 0.09≤Y 43 ≤0.13 decreasing to 0≤Y 44 ≤0.07.

[0026] In some embodiments, the In component content of the Ga-polarity light-emitting quantum well layer in the first long-wave cyan light-emitting multi-quantum well layer is 0.20~0.21, and the growth thickness is 2.15nm~4.8nm; the In component content of the Ga-polarity light-emitting quantum well layer in the second short-wave cyan light-emitting multi-quantum well layer is 0.19~0.20, and the growth thickness is 2.15nm~4.8nm; the In component content of the Ga-polarity light-emitting quantum well layer in the third long-wave blue light-emitting multi-quantum well layer is 0.13~0.19, and the growth thickness is 2.15nm~4.8nm; the In component content of the Ga-polarity light-emitting quantum well layer in the fourth short-wave blue light-emitting multi-quantum well layer is 0.10~0.13, and the growth thickness is 2.15nm~4.8nm.

[0027] In some embodiments, the Ga polarity light emitting quantum barrier layer has a growth thickness of 6.5 nm to 13.8 nm, and a Si doping concentration of 2.15×10 17 / cm 3 ~8.79×10 17 / cm 3 .

[0028] The present invention also provides a method for preparing a multi-band light-emitting diode epitaxial structure, comprising:

[0029] Providing a substrate; growing a buffer layer on the substrate; introducing a Si doping source to grow an N-type semiconductor layer on the buffer layer; growing a low-temperature stress release layer on the N-type semiconductor layer; growing a multi-quantum well light-emitting layer on the low-temperature stress release layer; growing an electron blocking layer on the multi-quantum well light-emitting layer; and growing a P-type semiconductor layer on the electron blocking layer.

[0030] The multi-quantum well light-emitting layer comprises a first long-wave cyan multi-quantum well layer, a second short-wave cyan multi-quantum well layer, a third long-wave blue multi-quantum well layer and a fourth short-wave blue multi-quantum well layer, which are stacked and grown in sequence from bottom to top.

[0031] The emission wavelengths of the first long-wave cyan multi-quantum well layer, the second short-wave cyan multi-quantum well layer, the third long-wave blue multi-quantum well layer, and the fourth short-wave blue multi-quantum well layer decrease in sequence;

[0032] The first long-wave cyan multi-quantum well layer, the second short-wave cyan multi-quantum well layer, the third long-wave blue multi-quantum well layer, and the fourth short-wave blue multi-quantum well layer all have four sub-layers that are periodically and alternately grown from bottom to top: an N-polarity well front insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity well back insertion layer, and a Ga-polarity light-emitting quantum barrier layer.

[0033] Before periodically alternating the deposition and growth of the N-polarity pre-well insertion layer and the N-polarity post-well insertion layer, the surface of the epitaxial layer material needs to be subjected to a full NH3 annealing treatment. That is, before periodically alternating the deposition and growth of the N-polarity pre-well insertion layer and the N-polarity post-well insertion layer, NH3 gas needs to be introduced into the reaction chamber, and the reaction chamber needs to be kept in a full NH3 atmosphere for 10-180 seconds. A rough N-polarity surface will be formed on the surface of the epitaxial layer material after the full NH3 annealing treatment, which is conducive to the subsequent growth of the epitaxial material of the N-polarity pre-well insertion layer and the N-polarity post-well insertion layer. At the same time, the rough N-polarity surface can reduce the in-plane total reflection and absorption loss of photons in the quantum well, which is more conducive to light extraction and improves light extraction efficiency.

[0034] In some embodiments, the temperature of the all-NH 3 annealing process is 818° C. to 1080° C., and the pressure is 30 torr to 360 torr.

[0035] In some embodiments, the N-polarity pre-well insertion layer includes an N-polarity low In component InGaN layer, an N-polarity first graded AlGaN layer, and an N-polarity first graded InGaN layer, which are sequentially stacked from bottom to top; wherein the N-polarity low In component InGaN layer is a single layer or multilayer structure of a low In component N-polarity InGaN lowly doped with Si element; the N-polarity first graded AlGaN layer is an N-polarity AlGaN material with an increasing Al component from bottom to top, and the AlGaN material is not intentionally doped; the N-polarity first graded InGaN layer is an N-polarity InGaN material with an increasing In component from bottom to top, and the InGaN material is not intentionally doped,

[0036] The growth temperature of the N-polarity low In content InGaN layer is 750°C-928°C, and the pressure is 30torr-360torr; the growth temperature of the N-polarity first gradient AlGaN layer is 780°C-928°C, and the pressure is 30torr-360torr; the growth temperature of the N-polarity first gradient InGaN layer is 730°C-910°C, and the pressure is 30torr-360torr.

[0037] In some embodiments, the growth temperature of the Ga-polarity light-emitting quantum well layer in the first long-wave cyan multi-quantum well layer is 725°C~928°C, and the pressure is 50torr-360torr; the growth temperature of the Ga-polarity light-emitting quantum well layer in the second short-wave cyan multi-quantum well layer is 738°C~928°C, and the pressure is 50torr-360torr; the growth temperature of the Ga-polarity light-emitting quantum well layer in the third long-wave blue light multi-quantum well layer is 750°C~928°C, and the pressure is 50torr-360torr; the growth temperature of the Ga-polarity light-emitting quantum well layer in the fourth short-wave blue light multi-quantum well layer is 790°C~928°C, and the pressure is 50torr-360torr.

[0038] In some embodiments, the N-polarity post-well insertion layer includes an N-polarity second graded InGaN layer, an N-polarity second graded AlGaN layer, and an N-polarity non-doped GaN layer, which are sequentially stacked and grown from bottom to top; wherein the N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In component from bottom to top, and the InGaN material is not intentionally doped; the N-polarity second graded AlGaN layer is an N-polarity AlGaN material with a decreasing Al component from bottom to top, and the AlGaN material is not intentionally doped; the N-polarity non-doped GaN layer is an N-polarity GaN single layer or multilayer structure that is not intentionally doped;

[0039] The growth temperature of the N-polarity second graded InGaN layer is 730°C-910°C, and the pressure is 30torr-360torr; the growth temperature of the N-polarity second graded AlGaN layer is 780°C-928°C, and the pressure is 30torr-360torr; the growth temperature of the N-polarity non-doped GaN layer is 800°C~928°C, and the pressure is 30torr-360torr.

[0040] In some embodiments, the growth temperature of the Ga polar luminescent quantum barrier layer is 819° C.-936° C., and the pressure is 30 torr-360 torr.

[0041] The beneficial effects of the present invention are:

[0042] (1) The multi-band light emitting diode epitaxial structure of the present invention has an excitation light source with four bands, which can be used to excite the red and green mixed phosphor layer to produce a full-spectrum white light LED light source. The proportion of short-wave blue light is small, which causes little damage to the retinal cells of the human eye. The full-spectrum white light produced is closer to the sunlight spectrum, thereby realizing a healthy full-spectrum white light LED light source with a high color rendering index.

[0043] (2) The four sub-emission wavelengths of the multi-quantum well light-emitting layer of the light-emitting diode of the present invention decrease in sequence; the multi-quantum well light-emitting layer is usually prepared by low-temperature deposition and growth at 650-935°C. The quality of the deposited epitaxial film material will become worse and worse as the thickness of the deposited epitaxial film increases. The longer the light-emitting wavelength, the higher the In component of the InGaN material of the quantum well, and the greater the mismatch stress caused by the well-barrier mismatch, and the more defects are generated. InGaN materials with high In components have lower growth temperatures, and the defects of the grown epitaxial film increase. Therefore, the growth order of the multi-band multi-quantum well light-emitting layer is designed to preferably deposit and grow long-wave quantum wells first and then deposit and grow short-wave quantum wells. By adopting the structural design of the present invention, it is easier to obtain high-quality multi-band multi-quantum well light-emitting layer materials, thereby improving the radiation recombination efficiency of the active region and further improving the light efficiency of the multi-band LED chip.

[0044] (3) In the epitaxial structure of the light-emitting diode of the present invention, the multi-quantum well layer of the four wavelength bands has four sub-layers that grow alternately and periodically from bottom to top. The arrangement of these four sub-layers utilizes the opposite directions of the polarization electric fields of Ga polar nitride and N polar nitride, which can significantly improve the band bending phenomenon caused by the polarization electric field in the multi-quantum well light-emitting layer, thereby improving the coupling between the electron and hole wave functions in the quantum well, thereby improving the radiation recombination efficiency in the multi-quantum well light-emitting layer and ultimately improving the luminous efficiency of the multi-band LED chip.

[0045] (4) The design of the gradient AlGaN layer and gradient InGaN layer in the epitaxial structure of the present invention is such that the AlGaN material with high barrier and high Al content is used near the InGaN material. This design can improve the energy band barrier difference between the low barrier material InGaN material and the high barrier material AlGaN material in the light-emitting quantum well layer, significantly improve the carrier binding ability of the quantum well, reduce the electron overflow phenomenon in the active region, effectively improve the radiation recombination efficiency in the multi-quantum well light-emitting layer, and ultimately achieve the improvement of the yield and brightness of the multi-band LED chip; at the same time, the AlGaN material with relatively low barrier and low Al content is used away from the InGaN material, and further, the Al content of the AlGaN material is N-polarity. The second gradient AlGaN layer is less than or equal to the first gradient AlGaN layer with N polarity. This design can effectively reduce the blocking effect of the high barrier material AlGaN material on the hole injection of the P-type semiconductor layer, increase the hole concentration injected into the active region from the P-type semiconductor layer, thereby effectively improving the radiation recombination efficiency in the multi-quantum well light-emitting layer, and thus improving the light efficiency of the multi-band LED chip.

[0046] (5) The epitaxial structure of the light-emitting diode of the present invention is subjected to full NH3 annealing treatment on the surface of the epitaxial layer material before the periodic alternating growth of the N-polarity well front insertion layer and the N-polarity well rear insertion layer. The surface of the epitaxial layer material after the full NH3 annealing treatment will form a rough N-polarity surface, which is conducive to the subsequent growth of the epitaxial material of the N-polarity well front insertion layer and the N-polarity well rear insertion layer. At the same time, the rough N-polarity surface can reduce the in-plane total reflection and absorption loss of photons in the quantum well, which is more conducive to light extraction and improves the light extraction efficiency, thereby improving the light efficiency of the multi-band LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Schematic diagram of the epitaxial structure of the multi-band light-emitting diode of the present invention, in which: 100-substrate, 200-buffer layer, 300-N-type semiconductor layer, 400-low-temperature stress release layer, 500-multi-quantum well light-emitting layer, 600-electron blocking layer, 700-P-type semiconductor layer;

[0048] Figure 2 Schematic diagram of the multi-quantum well light-emitting layer structure of the epitaxial structure of the present invention, in which: 500-multi-quantum well light-emitting layer, 510-first long-wave cyan multi-quantum well layer, 520-second short-wave cyan multi-quantum well layer, 530-third long-wave blue multi-quantum well layer, 540-fourth short-wave blue multi-quantum well layer, 511-first N-polarity well front insertion layer, 512-first Ga-polarity light-emitting quantum well layer, 513-first N-polarity well rear insertion layer, 514-first Ga-polarity light-emitting quantum barrier layer, 521-second N-polarity well front insertion layer layer, 522-second Ga polarity light-emitting quantum well layer, 523-second N polarity well rear insertion layer, 524-second Ga polarity light-emitting quantum barrier layer, 531-third N polarity well front insertion layer, 532-third Ga polarity light-emitting quantum well layer, 533-third N polarity well rear insertion layer, 534-third Ga polarity light-emitting quantum barrier layer, 541-fourth N polarity well front insertion layer, 542-fourth Ga polarity light-emitting quantum well layer, 543-fourth N polarity well rear insertion layer, 544-fourth Ga polarity light-emitting quantum barrier layer. DETAILED DESCRIPTION

[0049] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0050] refer to Figure 1-Figure 2 A multi-band light-emitting diode epitaxial structure includes, from bottom to top: 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.

[0051] In this structure, the substrate 100, buffer layer 200, N-type semiconductor layer 300, low-temperature stress relief layer 400, electron blocking layer 600, and P-type semiconductor layer 700 can be arranged according to the existing common white light LED chip epitaxial structure. For example, substrate 100 can be a sapphire substrate, which is currently the most commonly used substrate material. Sapphire substrates have the advantages of mature manufacturing processes, low price, easy cleaning and processing, and good stability at high temperatures. The buffer layer 200 can be a GaN buffer layer, an AlN buffer layer, or a SiN buffer layer. Its main function is to alleviate the lattice mismatch and thermal mismatch between the substrate and the epitaxial layer, thereby improving the crystal quality of the epitaxial layer and enhancing the performance and reliability of the chip. The N-type semiconductor layer 300 is typically a Si-doped N-type GaN layer. The low-temperature stress relief layer 400 can be a low-temperature GaN layer, a low-temperature InGaN layer, etc., to alleviate stress generated during the chip manufacturing process. The electron blocking layer 600 can be an AlGaN layer, an AlInGaN layer, etc., and the P-type semiconductor layer 700 is typically a Mg-doped GaN layer.

[0052] It should be noted that the multi-quantum well light-emitting layer 500 includes four sublayers stacked sequentially from bottom to top: a first long-wavelength cyan multi-quantum well layer 510, a second short-wavelength cyan multi-quantum well layer 520, a third long-wavelength blue multi-quantum well layer 530, and a fourth short-wavelength blue multi-quantum well layer 540. The wavelength of light emitted from the multi-quantum well light-emitting layer 500 is greater in the first long-wavelength cyan multi-quantum well layer 510 than in the second short-wavelength cyan multi-quantum well layer 520, greater than in the third long-wavelength blue multi-quantum well layer 530, and greater than in the fourth short-wavelength blue multi-quantum well layer 540.

[0053] A full-spectrum white light LED light source is produced by stimulating the red and green mixed phosphor layer with four bands of excitation light. Compared with the blue light LED chip with only one band, the short-wave blue light below 450nm accounts for a small proportion and causes less damage to the human retinal cells. The full-spectrum white light produced is closer to the sunlight spectrum, thus realizing a healthy full-spectrum white light LED light source with a high color rendering index. Moreover, the luminous wavelength of each band decreases successively. The multi-quantum well luminescent layer is usually prepared by low-temperature deposition and growth at 650℃-935℃. The quality of the deposited epitaxial thin film material will become worse and worse with the increase of the thickness of the deposited epitaxial film, such as the crystallization quality and surface flatness. The quantum well with a longer luminous wavelength has a relatively higher In component of the InGaN material, and the defects caused by the mismatch stress caused by the well-barrier mismatch increase. The InGaN material with a high In component has a lower growth temperature, and the defects of the grown epitaxial film increase. Therefore, the growth order of the multi-band multi-quantum well luminescent layer is designed to preferably deposit and grow long-wave quantum wells first and then deposit and grow short-wave quantum wells. The structural design of the present invention makes it easier to obtain high-quality multi-band multi-quantum well luminescent layer materials, thereby improving the radiation recombination efficiency of the active area and further improving the light efficiency of the multi-band LED chip.

[0054] The first long-wavelength cyan multi-quantum well layer 510, the second short-wavelength cyan multi-quantum well layer 520, the third long-wavelength blue multi-quantum well layer 530, and the fourth short-wavelength blue multi-quantum well layer 540 all have four sublayers that are periodically grown and alternating from bottom to top: an N-polarity pre-well insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity post-well insertion layer, and a Ga-polarity light-emitting quantum barrier layer. The four sublayers of the first long-wavelength cyan multi-quantum well layer 510 are a first N-polarity pre-well insertion layer 511, a first Ga-polarity light-emitting quantum well layer 512, a first N-polarity post-well insertion layer 513, and a first Ga-polarity light-emitting quantum barrier layer 514. The four sublayers of the second short-wavelength cyan multi-quantum well layer 520 are a second N-polarity pre-well insertion layer 521, a second Ga-polarity light-emitting quantum well layer 522, a second N-polarity post-well insertion layer 523, and a second Ga-polarity light-emitting quantum barrier layer 524. The four sublayers of the third long-wavelength blue multi-quantum well layer 530 are a third N-polarity pre-well insertion layer 531, a third Ga-polarity light-emitting quantum well layer 532, a third N-polarity post-well insertion layer 533, and a third Ga-polarity light-emitting quantum barrier layer 534. The four sublayers of the fourth short-wavelength blue multi-quantum well layer 540 are a fourth N-polarity pre-well insertion layer 541, a fourth Ga-polarity light-emitting quantum well layer 542, a fourth N-polarity post-well insertion layer 543, and a fourth Ga-polarity light-emitting quantum barrier layer 544.

[0055] In this way, the sub-layer arrangement of the multi-quantum well light-emitting layer utilizes the opposite directions of the polarization electric fields of Ga polar nitride and N polar nitride, which can significantly improve the band bending phenomenon caused by the polarization electric field in the multi-quantum well light-emitting layer, thereby improving the coupling between the electron and hole wave functions in the quantum well, so as to improve the radiation recombination efficiency in the multi-quantum well light-emitting layer and ultimately improve the luminous efficiency of the multi-band LED chip.

[0056] Therefore, the multi-band light-emitting diode epitaxial structure of the present invention, by designing a multi-band multi-quantum well light-emitting layer and combining the design of the sub-layers of each multi-quantum well light-emitting layer, can improve the overall excitation efficiency through the synergistic effect of the excitation light of each band, output full-spectrum white light, which is closer to sunlight, has high luminous efficiency, good color rendering, better stability, and less damage to the human eye.

[0057] In the present invention, the four sublayers of the multi-quantum well light-emitting layer 500: the first long-wave cyan light multi-quantum well layer 510, the second short-wave cyan light multi-quantum well layer 520, the third long-wave blue light multi-quantum well layer 530, and the fourth short-wave blue light multi-quantum well layer 540, have decreasing emission wavelengths. That is, if the emission wavelength of the first long-wave cyan light multi-quantum well layer 510 is λ1, the emission wavelength of the second short-wave cyan light multi-quantum well layer 520 is λ2, the emission wavelength of the third long-wave blue light multi-quantum well layer 530 is λ3, and the emission wavelength of the fourth short-wave blue light multi-quantum well layer 540 is λ4, then λ1>λ2>λ3>λ4.

[0058] In some embodiments, the first long-wave cyan multi-quantum well layer 510 emits light at a wavelength ranging from 490 nm to 500 nm, the second short-wave cyan multi-quantum well layer 520 emits light at a wavelength ranging from 480 nm to 490 nm, the third long-wave blue multi-quantum well layer 530 emits light at a wavelength ranging from 445 nm to 480 nm, and the fourth short-wave blue multi-quantum well layer 540 emits light at a wavelength ranging from 430 nm to 445 nm. By regulating the emission wavelengths of each multi-quantum well layer in the multi-quantum well light-emitting layer 500, the generated full-spectrum white light can be closer to the sunlight spectrum, thereby realizing a healthy full-spectrum white light LED light source with a high color rendering index.

[0059] Exemplarily, the light emission wavelength λ1 of the first long-wavelength cyan multi-quantum well layer 510 is 490 nm, 492 nm, 495 nm, 498 nm or 500 nm, but is not limited thereto.

[0060] Exemplarily, the light emission wavelength λ2 of the second short-wavelength cyan multi-quantum well layer 520 is 480 nm, 482 nm, 485 nm, 488 nm or 490 nm, but is not limited thereto.

[0061] Exemplarily, the third long-wave blue multi-quantum well layer 530 emits an emission wavelength λ3 of 445nm, 448nm, 449nm, 450nm, 452nm, 455nm, 458nm, 460nm, 462nm, 465nm, 468nm, 470nm, 472nm, 475nm, 478nm, or 480nm, but is not limited thereto.

[0062] Exemplarily, the fourth short-wave blue multi-quantum well layer 540 emits an emission wavelength λ4 of 430 nm, 432 nm, 435 nm, 438 nm, 440 nm, 442 nm or 445 nm, but is not limited thereto.

[0063] It can be understood that there is an overlapping area in the emission wavelength value ranges corresponding to the above-mentioned multi-quantum well layers. During preparation, it is only necessary to ensure that the emission wavelengths between the four multi-quantum well layers, namely the first long-wave cyan light multi-quantum well layer 510, the second short-wave cyan light multi-quantum well layer 520, the third long-wave blue light multi-quantum well layer 530, and the fourth short-wave blue light multi-quantum well layer 540, decrease in sequence, that is, λ1>λ2>λ3>λ4.

[0064] In some embodiments, the first long-wave cyan multi-quantum well layer 510 includes four sub-layers that are periodically and alternately grown from bottom to top: a first N-polarity pre-well insertion layer 511, a first Ga-polarity light-emitting quantum well layer 512, a first N-polarity post-well insertion layer 513, and a first Ga-polarity light-emitting quantum barrier layer 514; the second short-wave cyan multi-quantum well layer 520 includes four sub-layers that are periodically and alternately grown from bottom to top: a second N-polarity pre-well insertion layer 521, a second Ga-polarity light-emitting quantum well layer 522, a second N-polarity post-well insertion layer 523, and a second Ga-polarity light-emitting quantum barrier layer 524; The third long-wave blue light multi-quantum well layer 530 includes four sub-layers that are periodically alternately grown from bottom to top: a third N-polarity pre-well insertion layer 531, a third Ga-polarity luminescent quantum well layer 532, a third N-polarity post-well insertion layer 533, and a third Ga-polarity luminescent quantum barrier layer 534; The fourth short-wave blue light multi-quantum well layer 540 includes four sub-layers that are periodically alternately grown from bottom to top: a fourth N-polarity pre-well insertion layer 541, a fourth Ga-polarity luminescent quantum well layer 542, a fourth N-polarity post-well insertion layer 543, and a fourth Ga-polarity luminescent quantum barrier layer 544. In summary, the first long-wavelength cyan multi-quantum well layer 510, the second short-wavelength cyan multi-quantum well layer 520, the third long-wavelength blue multi-quantum well layer 530, and the fourth short-wavelength blue multi-quantum well layer 540 all have four sublayers that are periodically alternatingly grown from bottom to top: an N-polarity pre-well insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity post-well insertion layer, and a Ga-polarity light-emitting quantum barrier layer. The alternating growth period of these four sublayers within the entire multi-quantum well light-emitting layer 500 ranges from 6 to 17. Specifically, the alternating growth period of the four sublayers in the first long-wavelength cyan multi-quantum well layer 510 ranges from 1 to 3, the alternating growth period of the four sublayers in the second short-wavelength cyan multi-quantum well layer 520 ranges from 1 to 3, the alternating growth period of the four sublayers in the third long-wavelength blue multi-quantum well layer 530 ranges from 2 to 6, and the alternating growth period of the four sublayers in the fourth short-wavelength blue multi-quantum well layer 540 ranges from 2 to 5.

[0065] Exemplarily, the periodic range of alternating growth of the four sublayers in the entire multi-quantum well light-emitting layer 500 is: 8, among which the periodic range of alternating growth in the first long-wave cyan light multi-quantum well layer 510 is: 1, the periodic range of alternating growth of the second short-wave cyan light multi-quantum well layer 520 is: 3, the periodic range of alternating growth of the third long-wave blue light multi-quantum well layer 530 is: 2, and the periodic range of alternating growth of the fourth short-wave blue light multi-quantum well layer 540 is: 2.

[0066] Exemplarily, the periodic range of the alternating growth of the four sub-layers in the entire multi-quantum well light-emitting layer 500 is: 11, among which the periodic range of the alternating growth of the first long-wave cyan light multi-quantum well layer 510 is: 2, the periodic range of the alternating growth of the second short-wave cyan light multi-quantum well layer 520 is: 2, the periodic range of the alternating growth of the third long-wave blue light multi-quantum well layer 530 is: 4, and the periodic range of the alternating growth of the fourth short-wave blue light multi-quantum well layer 540 is: 3.

[0067] Exemplarily, the periodic range of the alternating growth of the four sub-layers in the entire multi-quantum well light-emitting layer 500 is: 15, among which the periodic range of the alternating growth of the first long-wave cyan light multi-quantum well layer 510 is: 3, the periodic range of the alternating growth of the second short-wave cyan light multi-quantum well layer 520 is: 1, the periodic range of the alternating growth of the third long-wave blue light multi-quantum well layer 530 is: 6, and the periodic range of the alternating growth of the fourth short-wave blue light multi-quantum well layer 540 is: 5.

[0068] Exemplarily, the periodic range of the alternating growth of the four sub-layers in the entire multi-quantum well light-emitting layer 500 is: 17, among which the periodic range of the alternating growth of the first long-wave cyan light multi-quantum well layer 510 is: 3, the periodic range of the alternating growth of the second short-wave cyan light multi-quantum well layer 520 is: 3, the periodic range of the alternating growth of the third long-wave blue light multi-quantum well layer 530 is: 6, and the periodic range of the alternating growth of the fourth short-wave blue light multi-quantum well layer 540 is: 5.

[0069] It should be noted that the above is only an exemplary description of the alternating growth cycle of the four sub-layers in the first long-wave cyan light multi-quantum well layer 510, the second short-wave cyan light multi-quantum well layer 520, the third long-wave blue light multi-quantum well layer 530, and the fourth short-wave blue light multi-quantum well layer 540, but is not limited to this.

[0070] In some embodiments, the N-polarity pre-well insertion layer, i.e., the first N-polarity pre-well insertion layer 511, the second N-polarity pre-well insertion layer 521, the third N-polarity pre-well insertion layer 531, and the fourth N-polarity pre-well insertion layer 541, all include an N-polarity low In composition InGaN layer, an N-polarity first graded AlGaN layer, and an N-polarity first graded InGaN layer, which are sequentially stacked from bottom to top, wherein the N-polarity low In composition InGaN layer is a single-layer or multi-layer structure of a low In composition N-polarity InGaN lowly doped with Si element; the N-polarity first graded AlGaN layer is an N-polarity AlGaN material with increasing Al composition from bottom to top, and the AlGaN material is not intentionally doped; the N-polarity first graded InGaN layer is an N-polarity InGaN material with increasing In composition from bottom to top, and the InGaN material is not intentionally doped.

[0071] The Ga-polarity light-emitting quantum well layers, i.e., the first Ga-polarity light-emitting quantum well layer 512, the second Ga-polarity light-emitting quantum well layer 522, the third Ga-polarity light-emitting quantum well layer 532, and the fourth Ga-polarity light-emitting quantum well layer 542 are all single-layer or multi-layer structures of high In content Ga-polarity InGaN that are not intentionally doped.

[0072] The N-polarity post-well insertion layer, i.e., the first N-polarity post-well insertion layer 513, the second N-polarity post-well insertion layer 523, the third N-polarity post-well insertion layer 533, and the fourth N-polarity post-well insertion layer 543, all include an N-polarity second graded InGaN layer, an N-polarity second graded AlGaN layer, and an N-polarity undoped GaN layer, which are stacked and grown in sequence from bottom to top. The N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In component from bottom to top, and the InGaN material is not intentionally doped; the N-polarity second graded AlGaN layer is an N-polarity AlGaN material with a decreasing Al component from bottom to top, and the AlGaN material is not intentionally doped; and the N-polarity undoped GaN layer is an N-polarity GaN single-layer or multi-layer structure that is not intentionally doped.

[0073] The Ga-polarity quantum luminescence barrier layers, namely the first Ga-polarity quantum luminescence barrier layer 514 , the second Ga-polarity quantum luminescence barrier layer 524 , the third Ga-polarity quantum luminescence barrier layer 534 , and the fourth Ga-polarity quantum luminescence barrier layer 544 , are all Ga-polarity GaN single-layer or multi-layer structures lowly doped with Si elements.

[0074] In this way, AlGaN materials with high potential barriers and high Al components are used near the InGaN materials. This design can improve the band barrier difference between the low-barrier material InGaN material and the high-barrier material AlGaN material in the light-emitting quantum well layer area, significantly improve the quantum well's ability to bind carriers, reduce the electron overflow phenomenon in the active area, effectively improve the radiation recombination efficiency in the multi-quantum well light-emitting layer, and ultimately achieve the improvement of the yield and brightness of the multi-band LED chip; at the same time, AlGaN materials with relatively low potential barriers and low Al components are used away from the InGaN materials. This design can effectively reduce the blocking effect of the high-barrier material AlGaN material on the hole injection of the P-type semiconductor layer, increase the hole concentration injected from the P-type semiconductor layer 700 to the active area, thereby effectively improving the radiation recombination efficiency in the multi-quantum well light-emitting layer 500, and improving the luminous efficiency of the multi-band LED chip.

[0075] In some preferred embodiments, the Al component content of the N-polarity first graded AlGaN layer is greater than or equal to the Al component content of the N-polarity second graded AlGaN layer, which is more conducive to reducing the blocking effect of the high barrier material AlGaN on hole injection into the P-type semiconductor layer.

[0076] In some embodiments, in the N-polarity pre-well insertion layer, i.e., the first N-polarity pre-well insertion layer 511, the second N-polarity pre-well insertion layer 521, the third N-polarity pre-well insertion layer 531, and the fourth N-polarity pre-well insertion layer 541, the N-polarity low-In-content InGaN layer has an In content of 0 to 0.03, a growth thickness of no more than 0.5 nm, and a Si doping concentration of 1.18×10 17 / cm 3 ~6.79×10 17 / cm 3 ;

[0077] In some embodiments, in the N-polarity pre-well insertion layer, i.e., the first N-polarity pre-well insertion layer 511, the second N-polarity pre-well insertion layer 521, the third N-polarity pre-well insertion layer 531, and the fourth N-polarity pre-well insertion layer 541, the Al component content in the N-polarity first graded AlGaN layer is 0.01~0.16, and the growth thickness does not exceed 0.7nm.

[0078] In some embodiments, in the N-polarity pre-well insertion layer, i.e., the first N-polarity pre-well insertion layer 511, the second N-polarity pre-well insertion layer 521, the third N-polarity pre-well insertion layer 531, and the fourth N-polarity pre-well insertion layer 541, the In component content in the N-polarity first graded InGaN layer is 0 ~ 0.21, and the growth thickness does not exceed 0.9 nm.

[0079] In some embodiments, in the N-polarity rear well insertion layer, i.e., the first N-polarity rear well insertion layer 513, the second N-polarity rear well insertion layer 523, the third N-polarity rear well insertion layer 533, and the fourth N-polarity rear well insertion layer 543, the In component content in the N-polarity second graded InGaN layer is 0~0.21, and the growth thickness does not exceed 0.9nm.

[0080] In some embodiments, in the N-polarity post-well insertion layer, i.e., the first N-polarity post-well insertion layer 513, the second N-polarity post-well insertion layer 523, the third N-polarity post-well insertion layer 533, and the fourth N-polarity post-well insertion layer 543, the Al component content in the N-polarity second graded AlGaN layer is 0~0.12, and the growth thickness does not exceed 0.7nm.

[0081] In some embodiments, the growth thickness of the N-polarity non-doped GaN layer in the N-polarity post-well insertion layer, i.e., the first N-polarity post-well insertion layer 513 , the second N-polarity post-well insertion layer 523 , the third N-polarity post-well insertion layer 533 , and the fourth N-polarity post-well insertion layer 543 does not exceed 0.5 nm.

[0082] In some embodiments, the Al content of the N-polarity first graded AlGaN layer is 0.01≤X 11 ≤0.05 increasing to 0.06≤X 12≤0.16; the Al component content of the N-polarity second graded AlGaN layer is 0.05≤X 21 ≤0.12 decreasing to 0≤X 22 ≤0.03;X 21 ≤X 12 , X 22 ≤X 11 .

[0083] Exemplarily, the Al component content of the N-polarity first graded AlGaN layer increases from 0.01 to 0.06, and the Al component content of the N-polarity second graded AlGaN layer decreases from 0.05 to 0.

[0084] For example, the Al content of the first N-polarity graded AlGaN layer increases from 0.03 to 0.12, and the Al content of the second N-polarity graded AlGaN layer decreases from 0.10 to 0.01.

[0085] For example, the Al content of the first N-polarity graded AlGaN layer increases from 0.05 to 0.16, and the Al content of the second N-polarity graded AlGaN layer decreases from 0.12 to 0.03.

[0086] In some embodiments, in the first long-wavelength cyan multi-quantum well layer 510, the In component content in the N-polarity first graded InGaN layer is 0≤Y 11 ≤0.10 increasing to 0.15≤Y 12 ≤0.21, the In component content of the N-polarity second graded InGaN layer is 0.15≤Y 13 ≤0.21 decreasing to 0≤Y 14 ≤0.10.

[0087] For example, in the first long-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.0 to 0.15, and the In component content in the N-polarity second graded InGaN layer decreases from 0.15 to 0.0.

[0088] For example, in the first long-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.1 to 0.16, and the In component content in the N-polarity second graded InGaN layer decreases from 0.16 to 0.1.

[0089] For example, in the first long-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.5 to 0.20, and the In component content in the N-polarity second graded InGaN layer decreases from 0.15 to 0.0.

[0090] In some embodiments, in the second short-wavelength cyan multi-quantum well layer 520, the In component content in the N-polarity first graded InGaN layer is 0≤Y 21 ≤0.09 increasing to 0.13≤Y 22 ≤0.20, the In component content in the N-polarity second graded InGaN layer is 0.13≤Y 23 ≤0.20 decreasing to 0≤Y 24 ≤0.09.

[0091] For example, in the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.09 to 0.20, and the In component content in the N-polarity second graded InGaN layer decreases from 0.20 to 0.09.

[0092] For example, in the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.05 to 0.18, and the In component content in the N-polarity second graded InGaN layer decreases from 0.18 to 0.05.

[0093] For example, in the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0 to 0.13, and the In component content in the N-polarity second graded InGaN layer decreases from 0.13 to 0.00.

[0094] In some embodiments, in the third long-wave blue multi-quantum well layer 530, the In component content in the N-polarity first graded InGaN layer is 0≤Y 31 ≤0.08 increasing to 0.11≤Y 32 ≤0.19, the In component content in the N-polarity second graded InGaN layer is 0.11≤Y 33 ≤0.19 decreasing to 0≤Y 34 ≤0.08.

[0095] Illustratively, in the third long-wave blue multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.08 to 0.19, and the In component content in the N-polarity second graded InGaN layer decreases from 0.19 to 0.08.

[0096] Illustratively, in the third long-wave blue multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0 to 0.11, and the In component content in the N-polarity second graded InGaN layer decreases from 0.11 to 0.

[0097] For example, in the third long-wave blue multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.03 to 0.11, and the In component content in the N-polarity second graded InGaN layer decreases from 0.11 to 0.03.

[0098] In some embodiments, in the fourth short-wave blue multi-quantum well layer 540, the In component content in the N-polarity first graded InGaN layer is 0≤Y 41 ≤0.07 increasing to 0.09≤Y 42 ≤0.13, the In component content in the N-polarity second graded InGaN layer is 0.09≤Y 43 ≤0.13 decreasing to 0≤Y 44 ≤0.07.

[0099] Illustratively, in the fourth short-wave blue multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0 to 0.09, and the In component content in the N-polarity second graded InGaN layer decreases from 0.09 to 0.

[0100] Illustratively, in the fourth short-wave blue multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.04 to 0.13, and the In component content in the N-polarity second graded InGaN layer decreases from 0.13 to 0.04.

[0101] Illustratively, in the fourth short-wave blue multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.07 to 0.11, and the In component content in the N-polarity second graded InGaN layer decreases from 0.11 to 0.07.

[0102] In some embodiments, the first Ga-polarity light-emitting quantum well layer 512 in the first long-wavelength cyan multi-quantum well layer 510 has an In component content of 0.20 to 0.21 and a growth thickness of 2.15 nm to 4.8 nm.

[0103] Illustratively, the In component content of the first Ga-polarity light-emitting quantum well layer 512 in the first long-wavelength cyan multi-quantum well layer 510 is 0.20, 0.202, 0.204, 0.206, 0.208 or 0.21, etc., but is not limited thereto.

[0104] Illustratively, the growth thickness of the first Ga polarity light-emitting quantum well layer 512 in the first long-wave cyan multi-quantum well layer 510 is 2.15nm, 2.45nm, 2.65nm, 2.8nm, 3.0nm, 3.3nm, 3.6nm, 3.8nm, 4.0nm, 4.6nm, or 4.8nm, etc., but is not limited thereto.

[0105] In some embodiments, the second Ga-polarity light-emitting quantum well layer 522 in the second short-wavelength cyan multi-quantum well layer 520 has an In component content of 0.19-0.20 and a growth thickness of 2.15 nm-4.8 nm.

[0106] Illustratively, the In component content of the second Ga-polarity light-emitting quantum well layer 522 in the second short-wavelength cyan multi-quantum well layer 520 is 0.19, 0.192, 0.194, 0.196, 0.198 or 0.20, but is not limited thereto.

[0107] Exemplarily, the growth thickness of the second Ga polarity light-emitting quantum well layer 522 in the second short-wave cyan multi-quantum well layer 520 is 2.15nm, 2.45nm, 2.65nm, 2.8nm, 3.0nm, 3.3nm, 3.6nm, 3.8nm, 4.0nm, 4.6nm, or 4.8nm, but is not limited thereto.

[0108] In some embodiments, the third Ga-polarity light-emitting quantum well layer 532 in the third long-wavelength blue multi-quantum well layer 530 has an In component content of 0.13 to 0.19 and a growth thickness of 2.15 nm to 4.8 nm.

[0109] Illustratively, the In component content of the third Ga-polarity light-emitting quantum well layer 532 in the third long-wavelength blue light multi-quantum well layer 530 is 0.13, 0.14, 0.15, 0.16, 0.17, 0.18 or 0.19, but is not limited thereto.

[0110] Exemplarily, the growth thickness of the third Ga polarity light-emitting quantum well layer 532 in the third long-wave blue light multi-quantum well layer 530 is 2.15nm, 2.45nm, 2.65nm, 2.8nm, 3.0nm, 3.3nm, 3.6nm, 3.8nm, 4.0nm, 4.6nm, or 4.8nm, but is not limited thereto.

[0111] In some embodiments, the fourth Ga-polarity light-emitting quantum well layer 542 in the fourth short-wavelength blue light-emitting multi-quantum well layer 540 has an In component content of 0.10-0.13 and a growth thickness of 2.15 nm-4.8 nm.

[0112] For example, the In component content of the fourth Ga-polarity light-emitting quantum well layer 542 in the fourth short-wavelength blue light multi-quantum well layer 540 is 0.10, 0.105, 0.12, 0.125 or 0.13, but is not limited thereto.

[0113] Illustratively, the growth thickness of the fourth Ga polarity light-emitting quantum well layer 542 in the fourth short-wave blue light multi-quantum well layer 540 is 2.15nm, 2.45nm, 2.65nm, 2.8nm, 3.0nm, 3.3nm, 3.6nm, 3.8nm, 4.0nm, 4.6nm, or 4.8nm, but is not limited thereto.

[0114] In some embodiments, the first Ga-polarity light-emitting quantum barrier layer 514, the second Ga-polarity light-emitting quantum barrier layer 524, the third Ga-polarity light-emitting quantum barrier layer 534, and the fourth Ga-polarity light-emitting quantum barrier layer 544 are all Ga-polarity GaN single-layer or multi-layer structures lowly doped with Si elements, with a growth thickness of 6.5 nm to 13.8 nm and a Si doping concentration of 2.15×10 17 / cm 3 ~8.79×10 17 / cm 3 .

[0115] Illustratively, the growth thickness of the Ga-polarity GaN single layer lowly doped with Si element is 6.5nm, 7.0nm, 7.5nm, 8.0nm, 8.5nm, 9.0nm, 9.5nm, 10.0nm, 11.0nm, 12.0nm, 13.2nm, or 13.8nm, etc., but is not limited thereto.

[0116] For example, the Si doping concentration of the Ga-polar GaN monolayer lowly doped with Si is 2.15×10 17 / cm 3 , 3.15×10 17 / cm 3 , 4.50×10 17 / cm 3 , 5.88×10 17 / cm 3 7.00×10 17 / cm 3 , or 8.79×10 17 / cm 3 etc., but not limited to.

[0117] A method for preparing a multi-band light emitting diode epitaxial structure comprises the following steps:

[0118] A. Select substrate 100;

[0119] B. growing a buffer layer 200 on the substrate 100;

[0120] C. Introducing a Si doping source to grow an N-type semiconductor layer 300 on the buffer layer 200;

[0121] D. growing a low-temperature stress release layer 400 on the N-type semiconductor layer 300;

[0122] E. growing a multi-quantum well light-emitting layer 500 on the low-temperature stress release layer 400;

[0123] F. Growing an electron blocking layer 600 on the multi-quantum well light-emitting layer 500;

[0124] G. Growing a P-type semiconductor layer 700 on the electron blocking layer 600 .

[0125] The multi-quantum well light-emitting layer 500 includes four sub-layers stacked from bottom to top: a first long-wave cyan multi-quantum well layer 510, a second short-wave cyan multi-quantum well layer 520, a third long-wave blue multi-quantum well layer 530, and a fourth short-wave blue multi-quantum well layer 540; the emission wavelengths of the first long-wave cyan multi-quantum well layer 510, the second short-wave cyan multi-quantum well layer 520, the third long-wave blue multi-quantum well layer 530, and the fourth short-wave blue multi-quantum well layer 540 decrease in sequence; the first long-wave cyan multi-quantum well layer 510 includes four sub-layers periodically grown alternately from bottom to top: a first N-polarity well front insertion layer 511, a first Ga-polarity light-emitting quantum well layer 512, a first N-polarity well back insertion layer 513, and a first Ga-polarity light-emitting quantum barrier layer 514; the second short-wave cyan multi-quantum well layer 520 includes a first N-polarity well front insertion layer 511, a first Ga-polarity light-emitting quantum well layer 512, a first N-polarity well back insertion layer 513, and a first Ga-polarity light-emitting quantum barrier layer 514. The third long-wave blue multi-quantum well layer 530 includes four sub-layers periodically grown alternately from bottom to top: a second N-polarity pre-well insertion layer 521, a second Ga-polarity light-emitting quantum well layer 522, a second N-polarity post-well insertion layer 523, and a second Ga-polarity light-emitting quantum barrier layer 524. The third long-wave blue multi-quantum well layer 530 includes four sub-layers periodically grown alternately from bottom to top: a third N-polarity pre-well insertion layer 531, a third Ga-polarity light-emitting quantum well layer 532, a third N-polarity post-well insertion layer 533, and a third Ga-polarity light-emitting quantum barrier layer 534. The fourth short-wave blue multi-quantum well layer 540 includes four sub-layers periodically grown alternately from bottom to top: a fourth N-polarity pre-well insertion layer 541, a fourth Ga-polarity light-emitting quantum well layer 542, a fourth N-polarity post-well insertion layer 543, and a fourth Ga-polarity light-emitting quantum barrier layer 544. That is, the first long-wave cyan multi-quantum well layer 510, the second short-wave cyan multi-quantum well layer 520, the third long-wave blue multi-quantum well layer 530, and the fourth short-wave blue multi-quantum well layer 540 all have four sub-layers that grow periodically and alternately from bottom to top: an N-polarity well front insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity well back insertion layer, and a Ga-polarity light-emitting quantum barrier layer. Before periodically alternatingly depositing and growing the first N-polarity front well insertion layer 511, the second N-polarity front well insertion layer 521, the third N-polarity front well insertion layer 531, and the fourth N-polarity front well insertion layer 541, as well as the first N-polarity rear well insertion layer 513, the second N-polarity rear well insertion layer 523, the third N-polarity rear well insertion layer 533, and the fourth N-polarity rear well insertion layer 543, the surface of the epitaxial layer material needs to be subjected to a full NH3 annealing treatment. The surface of the epitaxial layer material that has undergone the full NH3 annealing treatment will form a rough N-polarity surface, which is beneficial to the subsequent growth of the epitaxial material. At the same time, the rough N-polarity surface can reduce the in-plane total reflection and absorption loss of photons in the quantum well, which is more conducive to light extraction, thereby improving light extraction efficiency and improving the luminous efficiency of the multi-band LED chip.

[0126] In a preferred embodiment, the temperature of the all-NH3 annealing treatment is 818°C to 1080°C, and the pressure is 30 torr to 360 torr, and the reaction chamber can be kept in the all-NH3 atmosphere for 10-180 seconds.

[0127] In some embodiments, the N-polarity front well insertion layer, i.e., the first N-polarity front well insertion layer 511, the second N-polarity front well insertion layer 521, the third N-polarity front well insertion layer 531, and the fourth N-polarity front well insertion layer 541, all include an N-polarity low In composition InGaN layer, an N-polarity first graded AlGaN layer, and an N-polarity first graded InGaN layer, which are sequentially stacked from bottom to top; wherein the N-polarity low In composition InGaN layer is a low In composition N-polarity InGaN single layer or multilayer structure lowly doped with Si element, and the growth temperature is 750°C~92°C. 8℃, and the pressure is 30torr-360torr; the N-polarity first graded AlGaN layer is an N-polarity AlGaN material with an increasing Al component from bottom to top, and the AlGaN material is not intentionally doped, the growth temperature is 780℃-928℃, and the pressure is 30torr-360torr; the N-polarity first graded InGaN layer is an N-polarity InGaN material with an increasing In component from bottom to top, and the InGaN material is not intentionally doped, the growth temperature is 730℃-910℃, and the pressure is 30torr-360torr.

[0128] In some embodiments, the growth temperature of the first Ga-polarity light-emitting quantum well layer 512 in the first long-wave cyan multi-quantum well layer 510 is 725°C~928°C, and the pressure is 50torr-360torr; the growth temperature of the second Ga-polarity light-emitting quantum well layer 522 in the second short-wave cyan multi-quantum well layer 520 is 738°C~928°C, and the pressure is 50torr-360torr; the growth temperature of the third Ga-polarity light-emitting quantum well layer 532 in the third long-wave blue light multi-quantum well layer 530 is 750°C~928°C, and the pressure is 50torr-360torr; the growth temperature of the fourth Ga-polarity light-emitting quantum well layer 542 in the fourth short-wave blue light multi-quantum well layer 540 is 790°C~928°C, and the pressure is 50torr-360torr.

[0129] Illustratively, the growth temperature of the first Ga polarity light-emitting quantum well layer 512 in the first long-wave cyan multi-quantum well layer 510 is 725°C, 750°C, 770°C, 790°C, 800°C, 820°C, 850°C, 880°C, 900°C, 910°C or 928°C, etc., but is not limited thereto.

[0130] Illustratively, the growth pressure of the first Ga polarity light-emitting quantum well layer 512 in the first long-wave cyan multi-quantum well layer 510 is 50 torr, 60 torr, 90 torr, 120 torr, 150 torr, 180 torr, 210 torr, 250 torr, 300 torr, 330 torr, or 360 torr, etc., but is not limited thereto.

[0131] Illustratively, the growth temperature of the second Ga polarity light-emitting quantum well layer 522 in the second short-wave cyan multi-quantum well layer 520 is 738°C, 750°C, 770°C, 790°C, 800°C, 820°C, 850°C, 880°C, 900°C, 910°C or 928°C, etc., but is not limited thereto.

[0132] Exemplarily, the growth pressure of the second Ga polarity light-emitting quantum well layer 522 in the second short-wave cyan multi-quantum well layer 520 is 50torr, 60torr, 90torr, 120torr, 150torr, 180torr, 210torr, 250torr, 300torr, 330torr, or 360torr, but is not limited thereto.

[0133] Illustratively, the growth temperature of the third Ga polarity light-emitting quantum well layer 532 in the third long-wave blue light multi-quantum well layer 530 is 750°C, 770°C, 790°C, 800°C, 820°C, 850°C, 880°C, 900°C, 910°C or 928°C, etc., but is not limited thereto.

[0134] Illustratively, the growth pressure of the third Ga polarity light-emitting quantum well layer 532 in the third long-wave blue light multi-quantum well layer 530 is 50 torr, 60 torr, 90 torr, 120 torr, 150 torr, 180 torr, 210 torr, 250 torr, 300 torr, 330 torr, or 360 torr, etc., but is not limited thereto.

[0135] Illustratively, the growth temperature of the fourth Ga polarity light-emitting quantum well layer 542 in the fourth shortwave blue multi-quantum well layer 540 is 790°C, 800°C, 820°C, 850°C, 880°C, 900°C, 910°C or 928°C, etc., but is not limited thereto.

[0136] Illustratively, the growth pressure of the fourth Ga polarity light-emitting quantum well layer 542 in the fourth short-wave blue light multi-quantum well layer 540 is 50 torr, 60 torr, 90 torr, 120 torr, 150 torr, 180 torr, 210 torr, 250 torr, 300 torr, 330 torr, or 360 torr, etc., but is not limited thereto.

[0137] In some embodiments, the N-polarity post-well insertion layer, i.e., the first N-polarity post-well insertion layer 513, the second N-polarity post-well insertion layer 523, the third N-polarity post-well insertion layer 533, and the fourth N-polarity post-well insertion layer 543, all include an N-polarity second graded InGaN layer, an N-polarity second graded AlGaN layer, and an N-polarity non-doped GaN layer, which are sequentially stacked and grown from bottom to top; wherein the N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In component from bottom to top, and the InGaN material is not intentionally doped; the growth The temperature is 730°C-910°C, and the pressure is 30 torr-360 torr. The N-polarity second graded AlGaN layer is an N-polarity AlGaN material with decreasing Al composition from bottom to top, and the AlGaN material is not intentionally doped. The growth temperature is 780°C-928°C, and the pressure is 30 torr-360 torr. The N-polarity undoped GaN layer is an N-polarity GaN single layer or multilayer structure that is not intentionally doped. The growth temperature is 800°C-928°C, and the pressure is 30 torr-360 torr.

[0138] In some embodiments, the growth temperature of the Ga-polarity light-emitting quantum barrier layer, i.e., the first Ga-polarity light-emitting quantum barrier layer 514 , the second Ga-polarity light-emitting quantum barrier layer 524 , the third Ga-polarity light-emitting quantum barrier layer 534 , and the fourth Ga-polarity light-emitting quantum barrier layer 544 , is 819° C.-936° C., and the pressure is 30 torr-360 torr.

[0139] Illustratively, the first Ga polarity light-emitting quantum barrier layer 514, the second Ga polarity light-emitting quantum barrier layer 524, the third Ga polarity light-emitting quantum barrier layer 534, and the fourth Ga polarity light-emitting quantum barrier layer 544 are 820°C, 850°C, 875°C, 900°C, 910°C, 925°C, 930°C, or 936°C, etc., but are not limited thereto.

[0140] Exemplarily, the growth pressure of the first Ga polarity light-emitting quantum barrier layer 514, the second Ga polarity light-emitting quantum barrier layer 524, the third Ga polarity light-emitting quantum barrier layer 534, and the fourth Ga polarity light-emitting quantum barrier layer 544 is 30 torr, 60 torr, 90 torr, 120 torr, 150 torr, 180 torr, 210 torr, 250 torr, 300 torr, 330 torr, or 360 torr, but is not limited thereto.

[0141] The technical solution of the present invention is further described below with reference to specific embodiments and comparative examples.

[0142] Example 1

[0143] A multi-band light-emitting diode epitaxial structure, comprising, from bottom to top, 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.

[0144] The substrate is a sapphire substrate, the buffer layer is a GaN buffer layer, the N-type semiconductor layer is a Si-doped N-type GaN layer, the low-temperature stress release layer is a low-temperature GaN layer, the electron blocking layer is an AlGaN layer, and the P-type semiconductor layer is a Mg-doped GaN layer.

[0145] The multi-quantum well light-emitting layer includes four sub-layers stacked and grown in sequence from bottom to top: a first long-wave cyan multi-quantum well layer, a second short-wave cyan multi-quantum well layer, a third long-wave blue multi-quantum well layer, and a fourth short-wave blue multi-quantum well layer;

[0146] The first long-wave cyan multi-quantum well layer emits a wavelength λ1 of 490 nm, the second short-wave cyan multi-quantum well layer emits a wavelength λ2 of 480 nm, the third long-wave blue multi-quantum well layer emits a wavelength λ3 of 445 nm, and the fourth short-wave blue multi-quantum well layer emits a wavelength λ4 of 430 nm.

[0147] The first long-wave cyan light multi-quantum well layer, the second short-wave cyan light multi-quantum well layer, the third long-wave blue light multi-quantum well layer, and the fourth short-wave blue light multi-quantum well layer all include four sub-layers stacked and grown in sequence from bottom to top: an N-polarity well front insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity well rear insertion layer, and a Ga-polarity light-emitting quantum barrier layer. The four sub-layers have a period of alternating growth of 12 in the entire multi-quantum well light-emitting layer, wherein the period of alternating growth of the four sub-layers in the first long-wave cyan light multi-quantum well layer is 2, the period of alternating growth of the four sub-layers in the second short-wave cyan light multi-quantum well layer is 2, the period of alternating growth of the four sub-layers in the third long-wave blue light multi-quantum well layer is 4, and the period of alternating growth of the four sub-layers in the fourth short-wave blue light multi-quantum well layer is 4.

[0148] The N-polarity well front insertion layer includes an N-polarity low-In content InGaN layer, an N-polarity first graded AlGaN layer, and an N-polarity first graded InGaN layer, which are sequentially stacked from bottom to top;

[0149] The N-polarity low-In component InGaN layer is a low-In component N-polarity InGaN single layer or multilayer structure with low Si doping; the In component content is 0, the growth thickness is 0.3nm, and the Si doping concentration is 1.18×10 17 / cm 3 ;

[0150] The N-polarity first graded AlGaN layer is an N-polarity AlGaN material with an Al component increasing from bottom to top, and the AlGaN material is not intentionally doped, and the Al component content is X 110.01 increments to X 12 0.06, growth thickness 0.3nm;

[0151] The first N-polarity graded InGaN layer is an N-polarity InGaN material with an increasing In content from bottom to top, and the InGaN material is not intentionally doped, and has a growth thickness of 0.5 nm.

[0152] In the first long-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.10 to 0.15.

[0153] In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0 to 0.130;

[0154] In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0 to 0.11;

[0155] In the fourth short-wave blue light multi-quantum well layer, the In component content in the N-polarity first gradient InGaN layer increases gradually from 0 to 0.09.

[0156] The Ga-polarity light-emitting quantum well layer is a high-In content Ga-polarity InGaN single-layer structure that is not intentionally doped;

[0157] The Ga polar luminescent quantum well layer in the first long-wavelength cyan multi-quantum well layer has an In component content of 0.20 and a growth thickness of 2.15 nm.

[0158] The Ga polar luminescent quantum well layer in the second short-wavelength cyan multi-quantum well layer has an In component content of 0.19 and a growth thickness of 2.15 nm.

[0159] The Ga-polarity luminescent quantum well layer in the third long-wavelength blue multi-quantum well layer has an In component content of 0.13 and a growth thickness of 2.15 nm.

[0160] The In component content of the Ga-polarity luminescent quantum well layer in the fourth short-wave blue light multi-quantum well layer is 0.10, and the growth thickness is 2.15 nm.

[0161] The N-polarity well rear insertion layer includes an N-polarity second graded InGaN layer, an N-polarity second graded AlGaN layer and an N-polarity non-doped GaN layer which are sequentially stacked from bottom to top;

[0162] The N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In content from bottom to top, and the InGaN material is not intentionally doped; the growth thickness is 0.5 nm;

[0163] In the first long-wavelength cyan multi-quantum well layer, the In component content of the N-polarity second graded InGaN layer decreases from 0.1 to 0;

[0164] In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity second graded InGaN layer decreases from 0.130 to 0;

[0165] In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity second graded InGaN layer decreases from 0.110 to 0;

[0166] In the fourth short-wave blue multi-quantum well layer, the In component content in the N-polarity second graded InGaN layer decreases from 0.09 to 0;

[0167] The N-polarity second graded AlGaN layer is an N-polarity AlGaN material with an Al content decreasing from bottom to top, and the AlGaN material is not intentionally doped; the growth thickness is 0.3 nm;

[0168] The Al content of the N-polarity second graded AlGaN layer is determined by X 21 0.05 decrements to X 22 0;

[0169] The N-polarity non-doped GaN layer is an N-polarity GaN single layer structure that is not intentionally doped, and has a growth thickness of 0.3 nm.

[0170] The Ga-polarity luminescent quantum barrier layer is a Ga-polarity GaN multilayer structure with low Si doping; the growth thickness is 6.5nm, and the Si doping concentration is 2.15×10 17 / cm 3 .

[0171] The method for preparing the light-emitting diode epitaxial structure comprises the following steps:

[0172] Select a sapphire substrate;

[0173] On a sapphire substrate, a GaN buffer layer, a Si-doped N-type GaN layer, a low-temperature GaN stress release layer, a multi-quantum well light-emitting layer, an AlGaN electron barrier layer, and a Mg-doped GaN layer are sequentially deposited. The multi-quantum well light-emitting layer is achieved by periodically alternating the deposition of four sub-layers: a first long-wave cyan multi-quantum well layer, a second short-wave cyan multi-quantum well layer, a third long-wave blue multi-quantum well layer, and a fourth short-wave blue multi-quantum well layer. The four multi-quantum well layers of different wavelengths are further achieved by periodically alternating the deposition of an N-polarity pre-well insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity post-well insertion layer, and a Ga-polarity light-emitting quantum barrier layer.

[0174] Among them, the growth temperature of the N-polarity low In content InGaN layer of the N-polarity front well insertion layer is 750℃ and the pressure is 30torr; the growth temperature of the N-polarity first graded AlGaN layer is 780℃ and the pressure is 30torr; the growth temperature of the N-polarity first graded InGaN layer is 730℃ and the pressure is 30torr.

[0175] The growth temperature of the Ga-polarity luminescent quantum well layer in the first long-wave cyan multi-quantum well layer is 725°C, and the pressure is 50 torr; the growth temperature of the Ga-polarity luminescent quantum well layer in the second short-wave cyan multi-quantum well layer is 738°C, and the pressure is 50 torr; the growth temperature of the Ga-polarity luminescent quantum well layer in the third long-wave blue multi-quantum well layer is 750°C, and the pressure is 50 torr; the growth temperature of the Ga-polarity luminescent quantum well layer in the fourth short-wave blue multi-quantum well layer is 790°C, and the pressure is 50 torr.

[0176] The N-polarity second graded InGaN layer of the N-polarity well rear insertion layer is grown at a temperature of 730°C and a pressure of 30 Torr; the N-polarity second graded AlGaN layer is grown at a temperature of 780°C and a pressure of 30 Torr; and the N-polarity undoped GaN layer is grown at a temperature of 800°C and a pressure of 30 Torr.

[0177] The growth temperature of the Ga polar luminescent quantum barrier layer is 819°C and the pressure is 30 torr.

[0178] Before periodically alternating the deposition and growth of the N-polarity well front insertion layer and the N-polarity well rear insertion layer, the surface of the epitaxial layer material is subjected to a full NH3 annealing treatment at a temperature of 818°C and a pressure of 30 torr, and the reaction chamber is kept in a full NH3 atmosphere for 180 seconds.

[0179] Example 2

[0180] A multi-band light-emitting diode epitaxial structure, comprising, from bottom to top, 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.

[0181] The substrate is a sapphire substrate, the buffer layer is a GaN buffer layer, the N-type semiconductor layer is a Si-doped N-type GaN layer, the low-temperature stress release layer is a low-temperature GaN layer, the electron blocking layer is an AlGaN layer, and the P-type semiconductor layer is a Mg-doped GaN layer.

[0182] The multi-quantum well light-emitting layer includes four sub-layers stacked and grown in sequence from bottom to top: a first long-wave cyan multi-quantum well layer, a second short-wave cyan multi-quantum well layer, a third long-wave blue multi-quantum well layer, and a fourth short-wave blue multi-quantum well layer;

[0183] The first long-wave cyan multi-quantum well layer emits a wavelength λ1 of 495 nm, the second short-wave cyan multi-quantum well layer emits a wavelength λ2 of 485 nm, the third long-wave blue multi-quantum well layer emits a wavelength λ3 of 460 nm, and the fourth short-wave blue multi-quantum well layer emits a wavelength λ4 of 440 nm.

[0184] The first long-wave cyan light multi-quantum well layer, the second short-wave cyan light multi-quantum well layer, the third long-wave blue light multi-quantum well layer, and the fourth short-wave blue light multi-quantum well layer all include four sub-layers stacked and grown in sequence from bottom to top: an N-polarity well front insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity well rear insertion layer, and a Ga-polarity light-emitting quantum barrier layer. The four sub-layers have a period of alternating growth of 12 in the entire multi-quantum well light-emitting layer, wherein the period of alternating growth of the four sub-layers in the first long-wave cyan light multi-quantum well layer is 2, the period of alternating growth of the four sub-layers in the second short-wave cyan light multi-quantum well layer is 2, the period of alternating growth of the four sub-layers in the third long-wave blue light multi-quantum well layer is 4, and the period of alternating growth of the four sub-layers in the fourth short-wave blue light multi-quantum well layer is 4.

[0185] The N-polarity well front insertion layer includes an N-polarity low-In content InGaN layer, an N-polarity first graded AlGaN layer, and an N-polarity first graded InGaN layer, which are sequentially stacked from bottom to top;

[0186] The N-polarity low-In component InGaN layer is a multilayer structure of low-In component N-polarity InGaN doped with Si. The In component content is 0.03, the growth thickness is 0.5 nm, and the Si doping concentration is 6.18×10 17 / cm 3 ;

[0187] The N-polarity first graded AlGaN layer is an N-polarity AlGaN material with an Al component increasing from bottom to top, and the AlGaN material is not intentionally doped, and the Al component content is X 11 0.05 increments to X 12 0.16, growth thickness 0.3nm;

[0188] The first N-polarity graded InGaN layer is an N-polarity InGaN material with an increasing In content from bottom to top, and the InGaN material is not intentionally doped, with a growth thickness of 0.7 nm;

[0189] In the first long-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.10 to 0.21.

[0190] In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.09 to 0.20.

[0191] In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity first gradient InGaN layer increases from 0.08 to 0.19.

[0192] In the fourth short-wave blue light multi-quantum well layer, the In component content in the N-polarity first gradient InGaN layer increases from 0.07 to 0.13.

[0193] The Ga-polarity light-emitting quantum well layer is a single or multilayer structure of Ga-polarity InGaN with a high In content that is not intentionally doped;

[0194] The Ga polar luminescent quantum well layer in the first long-wavelength cyan multi-quantum well layer has an In component content of 0.21 and a growth thickness of 4.8 nm.

[0195] The Ga polar luminescent quantum well layer in the second short-wavelength cyan multi-quantum well layer has an In component content of 0.20 and a growth thickness of 4.8 nm.

[0196] The Ga-polarity luminescent quantum well layer in the third long-wavelength blue multi-quantum well layer has an In component content of 0.19 and a growth thickness of 4.8 nm.

[0197] The In component content of the Ga-polarity luminescent quantum well layer in the fourth short-wave blue light multi-quantum well layer is 0.13, and the growth thickness is 4.8 nm.

[0198] The N-polarity well rear insertion layer comprises a multilayer structure of an N-polarity second graded InGaN layer, an N-polarity second graded AlGaN layer and an N-polarity non-doped GaN layer which are sequentially stacked and grown from bottom to top.

[0199] The N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In content from bottom to top, and the InGaN material is not intentionally doped; the growth thickness is 0.7 nm;

[0200] In the first long-wavelength cyan multi-quantum well layer, the In component content of the N-polarity second graded InGaN layer decreases from 0.21 to 0.10;

[0201] In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity second graded InGaN layer decreases from 0.20 to 0.09;

[0202] In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity second graded InGaN layer decreases from 0.19 to 0.08;

[0203] In the fourth short-wave blue multi-quantum well layer, the In component content in the N-polarity second graded InGaN layer decreases from 0.13 to 0.07;

[0204] The N-polarity second graded AlGaN layer is an N-polarity AlGaN material with an Al content decreasing from bottom to top, and the AlGaN material is not intentionally doped; the growth thickness is 0.5 nm;

[0205] The Al content of the N-polarity second graded AlGaN layer is determined by X 21 0.12 decrements to X 22 0.03;

[0206] The N-polarity non-doped GaN layer is an N-polarity GaN single layer or multilayer structure that is not intentionally doped; the growth thickness is 0.3 nm.

[0207] The Ga-polarity luminescent quantum barrier layer is a Ga-polarity GaN single layer or multilayer structure with low Si doping; the growth thickness is 10.8nm, and the Si doping concentration is 8.15×10 17 / cm 3 .

[0208] The method for preparing the light-emitting diode epitaxial structure comprises the following steps:

[0209] Select a sapphire substrate;

[0210] A GaN buffer layer, a Si-doped N-type GaN layer, a low-temperature GaN stress release layer, a multi-quantum well light-emitting layer, an AlGaN electron blocking layer, and a Mg-doped GaN layer are sequentially deposited and grown on a sapphire substrate.

[0211] The multi-quantum well light-emitting layer is achieved by periodically alternating the deposition of four sub-layers: a first long-wavelength cyan multi-quantum well layer, a second short-wavelength cyan multi-quantum well layer, a third long-wavelength blue multi-quantum well layer, and a fourth short-wavelength blue multi-quantum well layer. The four multi-quantum well layers of different wavelengths are further achieved by periodically alternating the deposition of an N-polarity pre-well insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity post-well insertion layer, and a Ga-polarity light-emitting quantum barrier layer.

[0212] Among them, the growth temperature of the N-polarity low In content InGaN layer of the N-polarity front well insertion layer is 850℃ and the pressure is 160torr; the growth temperature of the N-polarity first graded AlGaN layer is 850℃ and the pressure is 160torr; the growth temperature of the N-polarity first graded InGaN layer is 850℃ and the pressure is 160torr.

[0213] The growth temperature of the Ga-polarity luminescent quantum well layer in the first long-wave cyan multi-quantum well layer is 850°C, and the pressure is 160 torr; the growth temperature of the Ga-polarity luminescent quantum well layer in the second short-wave cyan multi-quantum well layer is 850°C, and the pressure is 160 torr; the growth temperature of the Ga-polarity luminescent quantum well layer in the third long-wave blue multi-quantum well layer is 850°C, and the pressure is 160 torr; the growth temperature of the Ga-polarity luminescent quantum well layer in the fourth short-wave blue multi-quantum well layer is 850°C, and the pressure is 160 torr.

[0214] The N-polarity second graded InGaN layer of the N-polarity well rear insertion layer is grown at a temperature of 850°C and a pressure of 160 torr; the N-polarity second graded AlGaN layer is grown at a temperature of 850°C and a pressure of 160 torr; and the N-polarity undoped GaN layer is grown at a temperature of 850°C and a pressure of 160 torr.

[0215] The growth temperature of the Ga polar luminescent quantum barrier layer is 870°C and the pressure is 160 torr.

[0216] Before periodically alternating the deposition and growth of the N-polarity well front insertion layer and the N-polarity well rear insertion layer, the surface of the epitaxial layer material is subjected to a full NH3 annealing treatment. The annealing temperature is 900°C and the pressure is 160 Torr, and the reaction chamber is kept in a full NH3 atmosphere for 30 seconds.

[0217] Example 3

[0218] A multi-band light-emitting diode epitaxial structure, comprising, from bottom to top, 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.

[0219] The substrate is a sapphire substrate, the buffer layer is a GaN buffer layer, the N-type semiconductor layer is a Si-doped N-type GaN layer, the low-temperature stress release layer is a low-temperature GaN layer, the electron blocking layer is an AlGaN layer, and the P-type semiconductor layer is a Mg-doped GaN layer.

[0220] The multi-quantum well light-emitting layer includes four sub-layers stacked and grown in sequence from bottom to top: a first long-wave cyan multi-quantum well layer, a second short-wave cyan multi-quantum well layer, a third long-wave blue multi-quantum well layer, and a fourth short-wave blue multi-quantum well layer;

[0221] The first long-wave cyan multi-quantum well layer has an emission wavelength λ1 of 500nm, the second short-wave cyan multi-quantum well layer has an emission wavelength λ2 of 490nm, the third long-wave blue multi-quantum well layer has an emission wavelength λ3 of 480nm, and the fourth short-wave blue multi-quantum well layer has an emission wavelength λ4 of 445nm.

[0222] The first long-wave cyan light multi-quantum well layer, the second short-wave cyan light multi-quantum well layer, the third long-wave blue light multi-quantum well layer, and the fourth short-wave blue light multi-quantum well layer all include four sub-layers stacked and grown in sequence from bottom to top: an N-polarity well front insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity well rear insertion layer, and a Ga-polarity light-emitting quantum barrier layer. The four sub-layers have a period of alternating growth of 12 in the entire multi-quantum well light-emitting layer, wherein the period of alternating growth of the four sub-layers in the first long-wave cyan light multi-quantum well layer is 2, the period of alternating growth of the four sub-layers in the second short-wave cyan light multi-quantum well layer is 2, the period of alternating growth of the four sub-layers in the third long-wave blue light multi-quantum well layer is 4, and the period of alternating growth of the four sub-layers in the fourth short-wave blue light multi-quantum well layer is 4.

[0223] The N-polarity well front insertion layer comprises an N-polarity low-In content InGaN layer, an N-polarity first graded AlGaN layer and an N-polarity first graded InGaN layer which are sequentially stacked and grown from bottom to top.

[0224] The N-polarity low-In component InGaN layer is a low-In component N-polarity InGaN single layer or multilayer structure with low Si doping; the In component content is 0.02, the growth thickness is 0.5 nm, and the Si doping concentration is 6.79×10 17 / cm 3 ;

[0225] The N-polarity first graded AlGaN layer is an N-polarity AlGaN material with an Al component increasing from bottom to top, and the AlGaN material is not intentionally doped, and the Al component content is X 11 0.03 increments to X 12 0.11, growth thickness 0.7nm;

[0226] The first N-polarity graded InGaN layer is an N-polarity InGaN material with an increasing In content from bottom to top, and the InGaN material is not intentionally doped, with a growth thickness of 0.9 nm;

[0227] In the first long-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.05 to 0.18.

[0228] In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.05 to 0.18;

[0229] In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer increases from 0.05 to 0.15;

[0230] In the fourth short-wave blue light multi-quantum well layer, the In component content in the N-polarity first gradient InGaN layer increases gradually from 0.03 to 0.11.

[0231] The Ga-polarity light-emitting quantum well layer is a single or multilayer structure of Ga-polarity InGaN with a high In content that is not intentionally doped;

[0232] The Ga polar luminescent quantum well layer in the first long-wavelength cyan multi-quantum well layer has an In component content of 0.20 and a growth thickness of 3.5 nm.

[0233] The Ga polar luminescent quantum well layer in the second short-wavelength cyan multi-quantum well layer has an In component content of 0.20 and a growth thickness of 3.5 nm.

[0234] The Ga-polarity luminescent quantum well layer in the third long-wavelength blue multi-quantum well layer has an In component content of 0.16 and a growth thickness of 3.5 nm.

[0235] The In component content of the Ga-polarity luminescent quantum well layer in the fourth short-wave blue light multi-quantum well layer is 0.12, and the growth thickness is 3.5 nm.

[0236] The N-polarity well rear insertion layer comprises an N-polarity second graded InGaN layer, an N-polarity second graded AlGaN layer and an N-polarity non-doped GaN layer which are sequentially stacked and grown from bottom to top.

[0237] The N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In content from bottom to top, and the InGaN material is not intentionally doped; the growth thickness is 0.9 nm;

[0238] In the first long-wavelength cyan multi-quantum well layer, the In component content of the N-polarity second graded InGaN layer decreases from 0.18 to 0.05;

[0239] In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity second graded InGaN layer decreases from 0.17 to 0.05;

[0240] In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity second graded InGaN layer decreases from 0.15 to 0.04;

[0241] In the fourth short-wave blue light multi-quantum well layer, the In component content in the N-polarity second graded InGaN layer decreases gradually from 0.11 to 0.04.

[0242] The N-polarity second graded AlGaN layer is an N-polarity AlGaN material with Al content decreasing from bottom to top, and the AlGaN material is not intentionally doped; the growth thickness is 0.7nm; the Al content of the N-polarity second graded AlGaN layer is X 21 0.10 decrements to X 22 0.02.

[0243] The N-polarity non-doped GaN layer is an N-polarity GaN single layer or multilayer structure that is not intentionally doped; the growth thickness does not exceed 0.5 nm.

[0244] The Ga-polarity luminescent quantum barrier layer is a Ga-polarity GaN single layer or multilayer structure with low Si doping; the growth thickness is 13.8nm, and the Si doping concentration is 8.79×10 17 / cm 3 .

[0245] The method for preparing the light-emitting diode epitaxial structure comprises the following steps:

[0246] Select a sapphire substrate;

[0247] 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 are sequentially deposited on the substrate.

[0248] The multi-quantum well light-emitting layer is achieved by periodically alternating the deposition of four sub-layers: a first long-wavelength cyan multi-quantum well layer, a second short-wavelength cyan multi-quantum well layer, a third long-wavelength blue multi-quantum well layer, and a fourth short-wavelength blue multi-quantum well layer. The four multi-quantum well layers of different wavelengths are further achieved by periodically alternating the deposition of an N-polarity pre-well insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity post-well insertion layer, and a Ga-polarity light-emitting quantum barrier layer.

[0249] Before periodically alternating the deposition and growth of the N-polarity well front insertion layer and the N-polarity well rear insertion layer, the surface of the epitaxial layer material is subjected to a full NH3 annealing treatment. The annealing temperature is 1080°C and the pressure is 360 torr, and the reaction chamber is kept in a full NH3 atmosphere for 30 seconds.

[0250] The growth temperature of the N-polarity low In content InGaN layer of the N-polarity front well insertion layer is 928°C and the pressure is 360torr; the growth temperature of the N-polarity first graded AlGaN layer is 928°C and the pressure is 360torr; the growth temperature of the N-polarity first graded InGaN layer is 928°C and the pressure is 360torr.

[0251] The growth temperature of the Ga-polar luminescent quantum well layer in the first long-wave cyan multi-quantum well layer is 928°C, and the pressure is 360 torr; the growth temperature of the Ga-polar luminescent quantum well layer in the second short-wave cyan multi-quantum well layer is 928°C, and the pressure is 360 torr; the growth temperature of the Ga-polar luminescent quantum well layer in the third long-wave blue light multi-quantum well layer is 928°C, and the pressure is 360 torr; the growth temperature of the Ga-polar luminescent quantum well layer in the fourth short-wave blue light multi-quantum well layer is 928°C, and the pressure is 360 torr.

[0252] The N-polarity second graded InGaN layer of the N-polarity well rear insertion layer has a growth temperature of 910°C and a pressure of 360 torr; the N-polarity second graded AlGaN layer has a growth temperature of 928°C and a pressure of 360 torr; and the N-polarity undoped GaN layer has a growth temperature of 928°C and a pressure of 360 torr.

[0253] The growth temperature of the Ga polar luminescent quantum barrier layer is 936°C and the pressure is 360 torr.

[0254] Comparative Example 1

[0255] Referring to Example 1, the difference between this comparative example and Example 1 is that the N-polarity first graded AlGaN layer is an N-polarity AlGaN material with an Al component increasing from bottom to top, and the AlGaN material is not intentionally doped, and the Al component content is X 11 0.01 increments to X 12 0.06, growth thickness 0.3nm;

[0256] The N-polarity second graded AlGaN layer is an N-polarity AlGaN material with an Al content decreasing from bottom to top, and the AlGaN material is not intentionally doped; the growth thickness is 0.3 nm;

[0257] The Al content of the N-polarity second graded AlGaN layer is determined by X 21 0.08 decrements to X 22 0.01.

[0258] That is X 21 >X 12 , X 22 =X 11 .

[0259] Comparative Example 2

[0260] Referring to Example 1, the difference between this comparative example and Example 1 is that the graded AlGaN layer or the graded InGaN layer in the N-polarity well front insertion layer and the N-polarity well rear insertion layer are replaced by non-graded layers with the same average concentration. Specifically,

[0261] The N-polarity well front insertion layer includes an N-polarity low In content InGaN layer / an N-polarity first AlGaN layer / an N-polarity first InGaN layer which are sequentially stacked from bottom to top;

[0262] The N-polarity low-In content InGaN layer is the same as that in Example 1;

[0263] The first N-polarity AlGaN layer is an N-polarity AlGaN material with a uniformly distributed Al component, and the AlGaN material is not intentionally doped, with an Al component content of 0.035 and a growth thickness of 0.3 nm;

[0264] The first N-polarity InGaN layer is an N-polarity InGaN material with a uniformly distributed In component, and the InGaN material is not intentionally doped, with a growth thickness of 0.5 nm;

[0265] In the first long-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first InGaN layer is 0.125,

[0266] In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first InGaN layer is 0.065;

[0267] In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity first InGaN layer is 0.05;

[0268] In the fourth short-wave blue light multi-quantum well layer, the In component content in the N-polarity first gradient InGaN layer is 0.045.

[0269] The N-polarity well rear insertion layer includes an N-polarity second InGaN layer / an N-polarity second AlGaN layer / an N-polarity non-doped GaN layer stacked and grown in sequence from bottom to top;

[0270] The N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In content from bottom to top, and the InGaN material is not intentionally doped; the growth thickness is 0.5 nm;

[0271] In the first long-wavelength cyan multi-quantum well layer, the In component content of the N-polarity second InGaN layer is 0.05;

[0272] In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity second InGaN layer is 0.065;

[0273] In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity second InGaN layer is 0.05;

[0274] In the fourth short-wave blue multi-quantum well layer, the In component content in the N-polarity second InGaN layer is 0.045;

[0275] The N-polarity second AlGaN layer is an N-polarity AlGaN material with decreasing Al content from bottom to top, and the AlGaN material is not intentionally doped; the growth thickness is 0.3 nm; the Al content of the N-polarity second AlGaN layer is 0.025;

[0276] The N-polarity non-doped GaN layer is the same as that in Example 1.

[0277] Comparative Example 3

[0278] The difference from Example 1 is that the first long-wavelength cyan multi-quantum well layer is not provided, and the period of alternating growth of the four sub-layers in the second short-wavelength cyan multi-quantum well layer is 4.

[0279] Comparative Example 4

[0280] The difference from Example 1 is that the first long-wave cyan multi-quantum well layer and the second short-wave cyan multi-quantum well layer are not provided, the period of alternating growth of the four sub-layers in the third long-wave blue light multi-quantum well layer is 6, and the period of alternating growth of the four sub-layers in the fourth short-wave blue light multi-quantum well layer is 6.

[0281] The electrical parameters of the above embodiments and comparative examples were tested, and the luminous efficiency improvement rate of the remaining experimental groups relative to comparative example 4 was calculated, and the color rendering performance of each experimental group was tested. The test results are as follows: Specifically, the performance test results are shown in Table 1 below.

[0282] Table 1 Test results of examples and comparative examples

[0283]

[0284] The technical features of the above-described embodiments can be combined in any combination. To simplify the description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent of this invention shall be based on the attached claims.

Claims

1. A multi-band light-emitting diode epitaxial structure, characterized in that: From bottom to top, it includes: substrate, buffer layer, N-type semiconductor layer, low-temperature stress release layer, multi-quantum well light-emitting layer, electron blocking layer, and P-type semiconductor layer; The multi-quantum well light-emitting layer comprises a first long-wave cyan multi-quantum well layer, a second short-wave cyan multi-quantum well layer, a third long-wave blue multi-quantum well layer and a fourth short-wave blue multi-quantum well layer, which are sequentially stacked from bottom to top; The emission wavelengths of the first long-wave cyan multi-quantum well layer, the second short-wave cyan multi-quantum well layer, the third long-wave blue multi-quantum well layer, and the fourth short-wave blue multi-quantum well layer decrease in sequence; The first long-wave cyan multi-quantum well layer, the second short-wave cyan multi-quantum well layer, the third long-wave blue multi-quantum well layer, and the fourth short-wave blue multi-quantum well layer each include four sub-layers stacked and grown sequentially from bottom to top: an N-polarity pre-well insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity post-well insertion layer, and a Ga-polarity light-emitting quantum barrier layer; The N-polarity pre-well insertion layer includes an N-polarity low-In composition InGaN layer, an N-polarity first graded AlGaN layer, and an N-polarity first graded InGaN layer, which are sequentially stacked from bottom to top; wherein the N-polarity low-In composition InGaN layer is a single-layer or multi-layer structure of a low-In composition N-polarity InGaN low-doped with Si element; the N-polarity first graded AlGaN layer is an N-polarity AlGaN material with an increasing Al composition from bottom to top, and the AlGaN material is not intentionally doped; the N-polarity first graded InGaN layer is an N-polarity InGaN material with an increasing In composition from bottom to top, and the InGaN material is not intentionally doped; The Ga-polarity light-emitting quantum well layer is a single or multilayer structure of Ga-polarity InGaN with a high In content that is not intentionally doped; The N-polarity post-well insertion layer comprises an N-polarity second graded InGaN layer, an N-polarity second graded AlGaN layer, and an N-polarity non-doped GaN layer, which are sequentially stacked and grown from bottom to top; wherein the N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In component from bottom to top, and the InGaN material is not intentionally doped; the N-polarity second graded AlGaN layer is an N-polarity AlGaN material with a decreasing Al component from bottom to top, and the AlGaN material is not intentionally doped; the N-polarity non-doped GaN layer is an N-polarity GaN single layer or multilayer structure that is not intentionally doped; The Ga-polarity light-emitting quantum barrier layer is a Ga-polarity GaN single layer or multilayer structure low in Si doping; The Al component content of the N-polarity first graded AlGaN layer is greater than or equal to the Al component content of the N-polarity second graded AlGaN layer; The N-polarity low-In component InGaN layer has an In component content of 0 to 0.03, a growth thickness of no more than 0.5 nm, and a Si doping concentration of 1.18×10 17 / cm 3 ~6.79×10 17 / cm 3 ; The Ga polar light-emitting quantum well layer in the first long-wavelength cyan multi-quantum well layer has an In component content of 0.20 to 0.21 and a growth thickness of 2.15 nm to 4.8 nm; The growth thickness of the Ga polar luminescent quantum barrier layer is 6.5nm~13.8nm, and the Si doping concentration is 2.15×10 17 / cm 3 ~8.79×10 17 / cm 3 .

2. The multi-band light emitting diode epitaxial structure according to claim 1, characterized in that: The first long-wavelength cyan multi-quantum well layer emits light in the wavelength range of 490nm to 500nm. The second short-wavelength cyan multi-quantum well layer emits light in the wavelength range of 480nm to 490nm. The third long-wave blue multi-quantum well layer emits light at a wavelength ranging from 445 nm to 480 nm. The fourth short-wave blue light multi-quantum well layer emits light at a wavelength ranging from 430 nm to 445 nm.

3. The multi-band light emitting diode epitaxial structure according to claim 1, wherein: The period range of the alternating growth of the four sublayers in the first long-wave cyan light multi-quantum well layer is: 1~3, the period range of the alternating growth of the four sublayers in the second short-wave cyan light multi-quantum well layer is: 1~3, the period range of the alternating growth of the four sublayers in the third long-wave blue light multi-quantum well layer is: 2~6, and the period range of the alternating growth of the four sublayers in the fourth short-wave blue light multi-quantum well layer is: 2~5.

4. The multi-band light emitting diode epitaxial structure according to claim 1, wherein: The N-polarity well front insertion layer, The Al component content in the N-polarity first graded AlGaN layer is 0.01 to 0.16, and the growth thickness does not exceed 0.7 nm; The In component content of the N-polarity first graded InGaN layer is 0-0.21, and the growth thickness does not exceed 0.9 nm; The N-polarity well is inserted into the rear layer, The In component content of the N-polarity second graded InGaN layer is 0-0.21, and the growth thickness does not exceed 0.9 nm; The Al component content of the N-polarity second graded AlGaN layer is 0-0.12, and the growth thickness does not exceed 0.7 nm; The growth thickness of the N-polarity non-doped GaN layer does not exceed 0.5 nm.

5. The multi-band light emitting diode epitaxial structure according to claim 4, characterized in that: The Al component content of the N-polarity first graded AlGaN layer is 0.01≤X 11 ≤0.05 increasing to 0.06≤X 12 ≤0.16; The Al component content of the N-polarity second graded AlGaN layer is 0.05≤X 21 ≤0.12 decreasing to 0≤X 22 ≤0.03; X 21 ≤X 12 ,X 22 ≤X 11 。 6. The multi-band light emitting diode epitaxial structure according to claim 4, characterized in that: In the first long-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer is 0≤Y 11 ≤0.10 increasing to 0.15≤Y 12 ≤0.21, the In component content of the N-polarity second graded InGaN layer is 0.15≤Y 13 ≤0.21 decreasing to 0≤Y 14 ≤0.10; In the second short-wavelength cyan multi-quantum well layer, the In component content in the N-polarity first graded InGaN layer is 0≤Y 21 ≤0.09 increasing to 0.13≤Y 22 ≤0.20, the In component content in the N-polarity second graded InGaN layer is 0.13≤Y 23 ≤0.20 decreasing to 0≤Y 24 ≤0.09; In the third long-wave blue multi-quantum well layer, the In component content in the N-polarity first gradient InGaN layer is 0≤Y 31 ≤0.08 increasing to 0.11≤Y 32 ≤0.19, the In component content in the N-polarity second graded InGaN layer is 0.11≤Y 33 ≤0.19 decreasing to 0≤Y 34 ≤0.08; In the fourth short-wave blue multi-quantum well layer, the In component content in the N-polarity first gradient InGaN layer is 0≤Y 41 ≤0.07 increasing to 0.09≤Y 42 ≤0.13, the In component content in the N-polarity second graded InGaN layer is 0.09≤Y 43 ≤0.13 decreasing to 0≤Y 44 ≤0.

07.

7. The multi-band light emitting diode epitaxial structure according to claim 1, wherein: The Ga polar light-emitting quantum well layer in the second short-wavelength cyan multi-quantum well layer has an In component content of 0.19 to 0.20 and a growth thickness of 2.15 nm to 4.8 nm; The Ga polarity luminescent quantum well layer in the third long-wave blue light multi-quantum well layer has an In component content of 0.13 to 0.19 and a growth thickness of 2.15 nm to 4.8 nm; The In component content of the Ga polarity luminescent quantum well layer in the fourth short-wave blue light multi-quantum well layer is 0.10-0.13, and the growth thickness is 2.15nm-4.8nm.

8. A method for preparing a multi-band light-emitting diode epitaxial structure, characterized in that: The method for preparing the multi-band light-emitting diode epitaxial structure according to any one of claims 1 to 7 comprises the following steps: A. Select substrate; B. growing a buffer layer on the substrate; C. Introduce a Si doping source to grow an N-type semiconductor layer on the buffer layer; D. growing a low-temperature stress release layer on the N-type semiconductor layer; E. growing a multi-quantum well light-emitting layer on the low-temperature stress release layer; F. growing an electron blocking layer on the multi-quantum well light-emitting layer; G. growing a P-type semiconductor layer on the electron blocking layer; The multi-quantum well light-emitting layer comprises a first long-wave cyan multi-quantum well layer, a second short-wave cyan multi-quantum well layer, a third long-wave blue multi-quantum well layer and a fourth short-wave blue multi-quantum well layer, which are sequentially stacked from bottom to top; The emission wavelengths of the first long-wave cyan multi-quantum well layer, the second short-wave cyan multi-quantum well layer, the third long-wave blue multi-quantum well layer, and the fourth short-wave blue multi-quantum well layer decrease in sequence; The first long-wave cyan multi-quantum well layer, the second short-wave cyan multi-quantum well layer, the third long-wave blue multi-quantum well layer, and the fourth short-wave blue multi-quantum well layer each include four sub-layers periodically grown alternately from bottom to top: an N-polarity well front insertion layer, a Ga-polarity light-emitting quantum well layer, an N-polarity well back insertion layer, and a Ga-polarity light-emitting quantum barrier layer. Before the N-polarity well front insertion layer and the N-polarity well rear insertion layer are periodically and alternately grown, a full NH 3 annealing treatment is required for the surface of the epitaxial layer material.

9. The preparation method according to claim 8, characterized in that The N-polarity well front insertion layer includes an N-polarity low In component InGaN layer, an N-polarity first graded AlGaN layer and an N-polarity first graded InGaN layer, which are sequentially stacked from bottom to top; wherein the N-polarity low In component InGaN layer is a single layer or multilayer structure of a low In component N-polarity InGaN lowly doped with Si element; the N-polarity first graded AlGaN layer is an N-polarity AlGaN material with an increasing Al component from bottom to top, and the AlGaN material is not intentionally doped; the N-polarity first graded InGaN layer is an N-polarity InGaN material with an increasing In component from bottom to top, and the InGaN material is not intentionally doped, The growth temperature of the N-polarity low In content InGaN layer is 750°C-928°C, and the pressure is 30torr-360torr; the growth temperature of the N-polarity first graded AlGaN layer is 780°C-928°C, and the pressure is 30torr-360torr; the growth temperature of the N-polarity first graded InGaN layer is 730°C-910°C, and the pressure is 30torr-360torr; The growth temperature of the Ga polarity light-emitting quantum well layer in the first long-wave cyan multi-quantum well layer is 725° C. to 928° C., and the pressure is 50 torr to 360 torr; the growth temperature of the Ga polarity light-emitting quantum well layer in the second short-wave cyan multi-quantum well layer is 738° C. to 928° C., and the pressure is 50 torr to 360 torr; the growth temperature of the Ga polarity light-emitting quantum well layer in the third long-wave blue multi-quantum well layer is 750° C. to 928° C., and the pressure is 50 torr to 360 torr; the growth temperature of the Ga polarity light-emitting quantum well layer in the fourth short-wave blue multi-quantum well layer is 790° C. to 928° C., and the pressure is 50 torr to 360 torr; The N-polarity post-well insertion layer comprises an N-polarity second graded InGaN layer, an N-polarity second graded AlGaN layer, and an N-polarity non-doped GaN layer, which are sequentially stacked and grown from bottom to top; wherein the N-polarity second graded InGaN layer is an N-polarity InGaN material with a decreasing In component from bottom to top, and the InGaN material is not intentionally doped; the N-polarity second graded AlGaN layer is an N-polarity AlGaN material with a decreasing Al component from bottom to top, and the AlGaN material is not intentionally doped; the N-polarity non-doped GaN layer is an N-polarity GaN single layer or multilayer structure that is not intentionally doped; The growth temperature of the N-polarity second graded InGaN layer is 730°C-910°C, and the pressure is 30torr-360torr; the growth temperature of the N-polarity second graded AlGaN layer is 780°C-928°C, and the pressure is 30torr-360torr; the growth temperature of the N-polarity undoped GaN layer is 800°C-928°C, and the pressure is 30torr-360torr; The growth temperature of the Ga polar luminescent quantum barrier layer is 819° C.-936° C., and the pressure is 30 torr-360 torr.

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