Multi-band LED epitaxial structure and preparation method thereof

Abstract

The application discloses a multi-waveband LED epitaxial structure and a preparation method thereof, and relates to the technical field of semiconductors. The multi-waveband LED epitaxial structure is characterized in that the multi-quantum well light-emitting layer comprises a first long-wave blue light multi-quantum well light-emitting layer, a second middle-wave blue light multi-quantum well light-emitting layer, a third short-wave blue light multi-quantum well light-emitting layer and a fourth short-wave blue light multi-quantum well light-emitting layer which are stacked in sequence. The LED chip prepared by using the epitaxial structure can emit three different wavebands of long-wave blue light, middle-wave blue light and short-wave blue light. The excitation light source with the three wavebands of blue light can excite a red-green mixed fluorescent powder layer to generate a full-spectrum white light LED light source. Compared with the blue light LED chip with only one waveband, the short-wave blue light with a wavelength of less than 450 nm accounts for a small proportion, the damage to the human eye retina cells is small, and the healthy full-spectrum white light LED light source with a high color rendering index can be realized.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a multi-band LED epitaxial structure and its fabrication method. Background Technology

[0002] LED light sources have advantages such as small size, long lifespan, and high efficiency, and can be used continuously for up to tens of thousands of hours. LED light sources have become mainstream in the lighting field and are widely used. Currently, white LED devices on the market typically use phosphor coating on blue LED chips to emit white light. The mainstream technical approach is to use blue LED chips to excite a mixed red and green phosphor layer to achieve white light output.

[0003] However, existing white LED devices generally use single-wavelength blue LED chips. The spectral curves of these full-spectrum white LED light sources exhibit significant fluctuations and poor stability in the blue light band, resulting in a low color rendering index (CRI) and difficulty in accurately reproducing the inherent colors of objects. This leads to a discrepancy between the colors perceived by the human eye and the colors of objects under natural light. Furthermore, the single-wavelength blue LED chips used in existing full-spectrum white LED light sources typically emit light at wavelengths between 430nm and 460nm, with a high proportion of short-wavelength blue light below 450nm. This short-wavelength blue light has extremely high energy and can penetrate the lens to reach the retina. Prolonged exposure to this light source can easily damage retinal cells, leading to decreased or even lost vision. Therefore, optimizing the epitaxial structure of blue LED chips to obtain LED chips that minimize damage to retinal cells and achieve a high CRI is of great significance in addressing the shortcomings of current full-spectrum white LED light sources. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a multi-band LED epitaxial structure with three bands of blue light. The LED chip made using the multi-band LED epitaxial structure of the present invention produces full-spectrum white light that is closer to the solar spectrum, has a higher color rendering index, and has a small proportion of short-wavelength blue light, which causes less damage to human retinal cells. This is conducive to realizing a healthy full-spectrum white LED light source with a high color rendering index.

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a multi-band LED epitaxial structure, which can produce a blue LED epitaxial structure with three bands.

[0006] To address the aforementioned technical problems, the present invention provides a multi-band LED epitaxial structure, comprising a substrate and a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer disposed on the substrate.

[0007] The multi-quantum-well light-emitting layer includes a first long-wavelength blue light multi-quantum-well light-emitting layer, a second medium-wavelength blue light multi-quantum-well light-emitting layer, a third short-wavelength blue light multi-quantum-well light-emitting layer, and a fourth short-wavelength blue light quantum-well light-emitting layer, which are sequentially stacked along the epitaxial direction.

[0008] The emission wavelength of the first long-wavelength blue light multi-quantum-well emitting layer is greater than the emission wavelength of the second medium-wavelength blue light multi-quantum-well emitting layer, which is greater than the emission wavelength of the third short-wavelength blue light multi-quantum-well emitting layer, which equals the emission wavelength of the fourth short-wavelength blue light final quantum-well emitting layer.

[0009] The first long-wavelength blue light multi-quantum-well emitting layer, the second medium-wavelength blue light multi-quantum-well emitting layer, the third short-wavelength blue light multi-quantum-well emitting layer, and the fourth short-wavelength blue light final quantum-well emitting layer are all periodic structures formed by alternating stacking of well layers and barrier layers;

[0010] The band gap width of the barrier layer in the first long-wavelength blue light multi-quantum-well emitting layer is greater than the band gap width of the barrier layer in the second medium-wavelength blue light multi-quantum-well emitting layer, which is greater than the band gap width of the barrier layer in the third short-wavelength blue light multi-quantum-well emitting layer and is greater than or equal to the band gap width of the barrier layer in the fourth short-wavelength blue light final quantum-well emitting layer.

[0011] The barrier layer of the fourth short-wavelength blue light quantum well emitting layer is provided with a P-type carrier modulation insertion layer, which is doped with Mg element.

[0012] As an improvement to the above scheme, the well layer of the first long-wavelength blue light multi-quantum-well emitting layer is a first InGaN well layer, the well layer of the second medium-wavelength blue light multi-quantum-well emitting layer is a second InGaN well layer, the well layer of the third short-wavelength blue light multi-quantum-well emitting layer is a third InGaN well layer, and the well layer of the fourth short-wavelength blue light multi-quantum-well emitting layer is a fourth InGaN well layer.

[0013] The proportion of In composition in the first InGaN well layer > the proportion of In composition in the second InGaN well layer > the proportion of In composition in the third InGaN well layer = the proportion of In composition in the fourth InGaN well layer.

[0014] As an improvement to the above scheme, the emission wavelength of the first long-wavelength blue light multi-quantum-well emitting layer is 460nm~480nm;

[0015] The emission wavelength of the second mid-wave blue multi-quantum-well emitting layer is 445nm~460nm;

[0016] The emission wavelength of the third short-wavelength blue light multi-quantum-well emitting layer is 430nm~445nm;

[0017] The emission wavelength of the fourth short-wavelength blue light quantum well emitting layer is 430nm~445nm.

[0018] As an improvement to the above scheme, the In composition ratio of the first InGaN well layer is 0.16~0.19, the growth thickness is 2.03nm~4.87nm, the growth temperature is 750℃~930℃, and the pressure is 50torr~360torr;

[0019] The second InGaN well layer has an In composition ratio of 0.13~0.16, a growth thickness of 2.03nm~4.87nm, a growth temperature of 770℃~930℃, and a pressure of 50torr~360torr;

[0020] The third InGaN well layer has an In composition ratio of 0.10~0.13, a growth thickness of 2.03nm~4.87nm, a growth temperature of 790℃~930℃, and a pressure of 50torr~360torr.

[0021] The fourth InGaN well layer has an In composition ratio of 0.10~0.13, a growth thickness of 2.03nm~4.87nm, a growth temperature of 790℃~930℃, and a pressure of 50torr~360torr.

[0022] As an improvement to the above scheme, a first N-type carrier modulation insertion layer is provided in the barrier layer of the first long-wavelength blue light multi-quantum-well emitting layer. The first N-type carrier modulation insertion layer includes a first AlGaN insertion layer and a first Si-doped GaN insertion layer that are periodically and alternately stacked.

[0023] The barrier layer of the second mid-wave blue light multi-quantum-well emitting layer is provided with a second N-type carrier modulation insertion layer; the second N-type carrier modulation insertion layer includes a periodically alternating second AlGaN insertion layer and a second Si-doped GaN insertion layer;

[0024] The barrier layer of the third short-wavelength blue light multi-quantum-well emitting layer is provided with a third N-type carrier modulation insertion layer; the third N-type carrier modulation insertion layer includes a periodically alternating stacked third AlGaN insertion layer and a third Si-doped GaN insertion layer;

[0025] The proportion of Al component in the first AlGaN insertion layer is greater than that in the second AlGaN insertion layer, which is greater than that in the third AlGaN insertion layer; the growth thickness of the first AlGaN insertion layer is greater than that of the second AlGaN insertion layer, which is greater than that of the third AlGaN insertion layer.

[0026] As an improvement to the above scheme, the P-type carrier control insertion layer includes a front hole injection protection layer, a hole injection control layer and a rear hole injection protection layer stacked sequentially.

[0027] Both the front hole injection protective layer and the rear hole injection protective layer are made of AlGaN material, and the Al composition ratio of the AlGaN material in the front hole injection protective layer and the rear hole injection protective layer is less than the Al composition ratio of the second AlGaN insertion layer; the hole injection control layer is made of AlGaInN material and is doped with Mg element.

[0028] As an improvement to the above scheme, the Al composition ratio of the first AlGaN insertion layer is 0.03~0.30, the growth thickness is 0.6nm~3.0nm, the growth temperature is 818℃~935℃, and the pressure is 50torr~360torr;

[0029] The second AlGaN insertion layer has an Al composition ratio of 0.02~0.21, a growth thickness of 0.5nm~2.7nm, a growth temperature of 818℃~935℃, and a pressure of 50torr~360torr.

[0030] The third AlGaN insertion layer has an Al composition ratio of 0.01~0.15, a growth thickness of 0.3nm~2.2nm, a growth temperature of 818℃~935℃, and a pressure of 50torr~360torr.

[0031] The first, second, and third Si-doped GaN insertion layers are all doped with Si, with Si doping concentrations of 2.58 × 10⁻⁶. 17 / cm 3 ~9.73×10 17 / cm 3 The growth thicknesses ranged from 0.3 nm to 3 nm, the growth temperatures ranged from 818℃ to 935℃, and the pressures ranged from 50 torr to 360 torr.

[0032] Both the front hole injection protective layer and the rear hole injection protective layer are AlGaN materials without intentional doping, with Al composition ratios of 0.01~0.18, growth thicknesses of 0.3nm~2.5nm, growth temperatures of 818℃~935℃, and pressures of 50torr~360torr.

[0033] The hole injection control layer is an AlInGaN material doped with Mg, with an Al content of 0.01~0.15%, an In content of 0.02~0.15%, a thickness of 0.6nm~8.5nm, and a Mg doping concentration of 3.15×10⁻⁶.18 / cm 3 ~8.69×10 19 / cm 3 The growth temperature is 818℃~935℃, and the pressure is 50 torr~360 torr.

[0034] As an improvement to the above scheme, the barrier layer of the first long-wavelength blue light-emitting multi-quantum-well emitting layer is a first barrier layer, which further includes several first GaN layers. The first N-type carrier modulation insertion layer is interposed between the several first GaN layers. The first GaN layers are doped with Si, and the Si doping concentration is 1.9 × 10⁻⁶. 17 / cm 3 ~8.5×10 17 / cm 3 The growth thickness was 5.6 nm to 13.8 nm, the growth temperature was 818 °C to 935 °C, and the pressure was 50 torr to 360 torr.

[0035] The barrier layer of the second mid-wave blue light multi-quantum-well emitting layer is a second barrier layer, which further includes several second GaN layers. The second N-type carrier modulation insertion layer is interposed between the several second GaN layers. The second GaN layers are doped with Si, and the Si doping concentration is 1.5 × 10⁻⁶. 17 / cm 3 ~7.3×10 17 / cm 3 The growth thickness was 5.6 nm to 13.8 nm, the growth temperature was 818 °C to 935 °C, and the pressure was 50 torr to 360 torr.

[0036] The barrier layer of the third short-wavelength blue light-emitting multi-quantum-well emitting layer is a third barrier layer, which further includes several third GaN layers. The third N-type carrier modulation insertion layer is interposed between the several third GaN layers. The third GaN layers are doped with Si, and the Si doping concentration is 1.2 × 10⁻⁶. 17 / cm 3 ~6.1×10 17 / cm 3 The growth thickness was 5.6 nm to 13.8 nm, the growth temperature was 818 °C to 935 °C, and the pressure was 50 torr to 360 torr.

[0037] The barrier layer of the fourth short-wavelength blue light-emitting quantum well is a fourth barrier layer, which also includes several fourth GaN layers. The P-type carrier modulation insertion layer is inserted between the several fourth GaN layers. The growth thickness of the fourth GaN layer is 5.6 nm to 13.8 nm, the growth temperature is 818 °C to 935 °C, and the pressure is 50 torr to 360 torr.

[0038] Accordingly, the present invention also provides a method for fabricating a multi-band LED epitaxial structure, comprising:

[0039] Select a substrate;

[0040] A buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer are sequentially deposited on the substrate.

[0041] The multi-quantum-well light-emitting layer includes a first long-wavelength blue light multi-quantum-well light-emitting layer, a second medium-wavelength blue light multi-quantum-well light-emitting layer, a third short-wavelength blue light multi-quantum-well light-emitting layer, and a fourth short-wavelength blue light quantum-well light-emitting layer, which are sequentially stacked along the epitaxial direction.

[0042] The emission wavelength of the first long-wavelength blue light multi-quantum-well emitting layer is greater than the emission wavelength of the second medium-wavelength blue light multi-quantum-well emitting layer, which is greater than the emission wavelength of the third short-wavelength blue light multi-quantum-well emitting layer, which equals the emission wavelength of the fourth short-wavelength blue light final quantum-well emitting layer.

[0043] The first long-wavelength blue light multi-quantum-well emitting layer, the second medium-wavelength blue light multi-quantum-well emitting layer, the third short-wavelength blue light multi-quantum-well emitting layer, and the fourth short-wavelength blue light final quantum-well emitting layer are all periodic structures formed by alternating stacking of well layers and barrier layers;

[0044] The band gap width of the barrier layer in the first long-wavelength blue light multi-quantum-well emitting layer is greater than the band gap width of the barrier layer in the second medium-wavelength blue light multi-quantum-well emitting layer, which is greater than the band gap width of the barrier layer in the third short-wavelength blue light multi-quantum-well emitting layer and is greater than or equal to the band gap width of the barrier layer in the fourth short-wavelength blue light final quantum-well emitting layer.

[0045] The barrier layer of the fourth short-wavelength blue light quantum well emitting layer is provided with a P-type carrier modulation insertion layer, which is doped with Mg element.

[0046] As an improvement to the above scheme, the P-type carrier control insertion layer includes a front hole injection protection layer, a hole injection control layer and a rear hole injection protection layer stacked sequentially.

[0047] Both the front hole injection protective layer and the rear hole injection protective layer are made of AlGaN material, and the hole injection control layer is made of AlGaInN material and is doped with Mg element.

[0048] After the deposition of the fourth short-wavelength blue light quantum well emitting layer and the hole injection control layer is completed, surface roughening annealing treatment is required. The surface roughening annealing treatment temperature is 830℃~1080℃ and the pressure is 30 torr~500 torr.

[0049] Implementing this invention has the following beneficial effects:

[0050] Based on the above structural design of the LED epitaxial structure, the LED chip made using the epitaxial structure of this invention can emit three different wavelengths of blue light: long-wave blue light, medium-wave blue light, and short-wave blue light. By exciting the red and green mixed phosphor layer with the excitation light source with three wavelengths of blue light, a full-spectrum white LED light source can be generated. Compared with blue LED chips with only one wavelength, the proportion of short-wave blue light below 450nm is small, which causes less damage to human retinal cells. Moreover, since its excitation light source has three wavelengths, the full-spectrum white light generated is closer to the solar spectrum and has a higher color rendering index, thus realizing a healthy full-spectrum white LED light source with a high color rendering index.

[0051] Secondly, the emission wavelengths of each multi-quantum-well emissive layer are set as follows: the emission wavelength of the first long-wavelength blue multi-quantum-well emissive layer is greater than that of the second medium-wavelength blue multi-quantum-well emissive layer, which is greater than that of the third short-wavelength blue multi-quantum-well emissive layer, and equal to that of the fourth short-wavelength blue multi-quantum-well emissive layer. Therefore, the growth sequence of the multi-quantum-well emissive layers is designed to first deposit and grow long-wavelength quantum wells, and then deposit and grow short-wavelength quantum wells. Using the multi-band LED chip prepared by this invention, it is easier to obtain high-quality multi-band multi-quantum-well emissive layers, thereby improving the radiative recombination efficiency of the active region and further improving the luminous efficacy of the multi-band LED chip.

[0052] Furthermore, based on the fact that the bandgap width of the barrier layer in the first long-wavelength blue multi-quantum-well emitting layer is greater than the bandgap width of the barrier layer in the second medium-wavelength blue multi-quantum-well emitting layer, and the bandgap width of the barrier layer in the third short-wavelength blue multi-quantum-well emitting layer is greater than or equal to the bandgap width of the barrier layer in the fourth short-wavelength blue final quantum-well emitting layer, this structural design allows the energy band design of the barrier layer of the multi-quantum-well emitting layer of the present invention to use a low-bandgap barrier material near the P-type semiconductor layer and a high-bandgap barrier material near the N-type semiconductor layer. The low-bandgap barrier material can effectively reduce the blocking effect of the quantum barrier material on hole injection in the P-type semiconductor layer, increase the hole concentration injected from the P-type semiconductor layer into the active region, and allow the quantum wells near the N-type semiconductor layer to also participate in light emission, significantly improving the matching degree of electron-hole concentration in the multi-quantum-well emitting layer and improving the brightness and luminous efficacy of the multi-band LED chip. Meanwhile, the high bandgap barrier material can confine electrons in front of the first long-wavelength blue light multi-quantum-well emitting layer and the second medium-wavelength blue light multi-quantum-well emitting layer, thereby blocking electrons and reducing their migration speed. This effectively prevents electron overflow and prevents electrons from being injected into the P-type semiconductor layer, thus preventing electron leakage and improving the yield and other performance of multi-band LED chips.

[0053] Furthermore, the barrier layer of the fourth short-wavelength blue light-emitting quantum well emissive layer is provided with a P-type carrier modulation insertion layer, which is doped with Mg. The P-type carrier modulation insertion layer can provide some holes to the multi-quantum-well emissive layer to participate in radiative recombination luminescence, further improving the brightness and luminous efficacy of the multi-band LED epitaxial structure. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the multi-band LED epitaxial structure of the present invention;

[0055] Figure 2 This is a schematic diagram of the multi-quantum-well light-emitting layer in the multi-band LED epitaxial structure of the present invention;

[0056] Figure 3 This is a schematic diagram of the structure of the first barrier layer in the multi-quantum well light-emitting layer of the present invention;

[0057] Figure 4 This is a schematic diagram of the structure of the second barrier layer in the multi-quantum well light-emitting layer of the present invention;

[0058] Figure 5 This is a schematic diagram of the structure of the third barrier layer in the multi-quantum-well light-emitting layer of the present invention;

[0059] Figure 6 This is a schematic diagram of the fourth barrier layer structure in the multi-quantum well light-emitting layer of the present invention;

[0060] The structure includes: substrate 1, buffer layer 2, N-type semiconductor layer 3, low-temperature stress relief layer 4, multi-quantum well light-emitting layer 5, electron blocking layer 6, P-type semiconductor layer 7, first long-wavelength blue light multi-quantum well light-emitting layer 51, second medium-wavelength blue light multi-quantum well light-emitting layer 52, third short-wavelength blue light multi-quantum well light-emitting layer 53, fourth short-wavelength blue light quantum well light-emitting layer 54, first InGaN well layer 511, first barrier layer 512, second InGaN well layer 521, second barrier layer 522, third InGaN well layer 531, third barrier layer 532, fourth InGaN well layer 541, fourth barrier layer 542, first N-type carrier modulation insertion layer 5121, and first GaN layer 5. 122, First AlGaN insertion layer 51211, First Si-doped GaN insertion layer 51212, Second N-type carrier control insertion layer 5221, Second GaN layer 5222, Second AlGaN insertion layer 52211, Second Si-doped GaN insertion layer 52212, Third N-type carrier control insertion layer 5321, Third GaN layer 5322, Third AlGaN insertion layer 53211, Third Si-doped GaN insertion layer 53212, P-type carrier control insertion layer 5421, Fourth GaN layer 5422, Front hole injection protection layer 54211, Hole injection control layer 54212, and Back hole injection protection layer 54213. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0062] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Raw materials whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0063] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0064] See Figures 1 to 6 As shown, this embodiment provides a multi-band LED epitaxial structure, including a substrate 1 and a buffer layer 2, an N-type semiconductor layer 3, a low-temperature stress relief layer 4, a multi-quantum well light-emitting layer 5, an electron blocking layer 6, and a P-type semiconductor layer 7 disposed on the substrate.

[0065] The multi-quantum-well light-emitting layer 5 includes a first long-wavelength blue light multi-quantum-well light-emitting layer 51, a second medium-wavelength blue light multi-quantum-well light-emitting layer 52, a third short-wavelength blue light multi-quantum-well light-emitting layer 53, and a fourth short-wavelength blue light final quantum-well light-emitting layer 54, which are stacked sequentially along the epitaxial direction.

[0066] The emission wavelength of the first long-wavelength blue light multi-quantum-well emitting layer 51 is greater than that of the second medium-wavelength blue light multi-quantum-well emitting layer 52, which is greater than that of the third short-wavelength blue light multi-quantum-well emitting layer 53, which equals the emission wavelength of the fourth short-wavelength blue light multi-quantum-well emitting layer 54.

[0067] The first long-wavelength blue light multi-quantum-well emitting layer 51, the second mid-wavelength blue light multi-quantum-well emitting layer 52, the third short-wavelength blue light multi-quantum-well emitting layer 53, and the fourth short-wavelength blue light final quantum-well emitting layer 54 are all periodic structures formed by alternating stacked well layers and barrier layers; preferably, they are all superlattice structures of sequentially periodically alternating InGaN quantum-well layers and GaN quantum-barrier layers; preferably, the number of alternating growth cycles of the first long-wavelength blue light multi-quantum-well emitting layer 51 is 2 to 5, the number of alternating growth cycles of the second mid-wavelength blue light multi-quantum-well emitting layer 52 is 2 to 6, the number of alternating growth cycles of the third short-wavelength blue light multi-quantum-well emitting layer 53 is 2 to 5, and the number of alternating growth cycles of the fourth short-wavelength blue light final quantum-well emitting layer 54 is 1.

[0068] The bandgap width of the barrier layer in the first long-wavelength blue light multi-quantum-well emitting layer 51 is greater than the bandgap width of the barrier layer in the second medium-wavelength blue light multi-quantum-well emitting layer 52, which is greater than the bandgap width of the barrier layer in the third short-wavelength blue light multi-quantum-well emitting layer 53, which is greater than or equal to the bandgap width of the barrier layer in the fourth short-wavelength blue light final quantum-well emitting layer 54.

[0069] The fourth short-wavelength blue light-emitting quantum well light-emitting layer 54 has a P-type carrier modulation insertion layer 5421 in its barrier layer, and the P-type carrier modulation insertion layer 5421 is doped with Mg. The P-type carrier modulation insertion layer 5421 can provide some holes to the multi-quantum well light-emitting layer 5 to participate in radiative recombination luminescence, further improving the brightness and luminous efficacy of the multi-band LED epitaxial structure.

[0070] Based on the above structural design of the LED epitaxial structure, the LED chip fabricated using the epitaxial structure of this invention can emit three different wavelengths of blue light: long-wavelength blue light, medium-wavelength blue light, and short-wavelength blue light. By exciting the red and green mixed phosphor layer with the excitation light source of the three wavelengths of blue light, a full-spectrum white LED light source can be generated. Compared with blue LED chips with only one wavelength, the proportion of short-wavelength blue light below 450nm is small, which causes less damage to human retinal cells. Moreover, since its excitation light source has three wavelengths, the full-spectrum white light generated is closer to the solar spectrum and has a higher color rendering index, thereby realizing a healthy full-spectrum white LED light source with a high color rendering index.

[0071] It is worth noting that the emission wavelengths of each multi-quantum-well emitting layer are set as follows: the emission wavelength of the first long-wavelength blue multi-quantum-well emitting layer 51 is greater than that of the second medium-wavelength blue multi-quantum-well emitting layer 52, which is greater than that of the third short-wavelength blue multi-quantum-well emitting layer 53, which is equal to that of the fourth short-wavelength blue multi-quantum-well emitting layer 54. The reason for this structural setting is that the multi-quantum-well emitting layer 5 is typically prepared by low-temperature deposition growth at 650℃~935℃. The quality of the deposited epitaxial film material deteriorates with increasing thickness, resulting in poorer crystal quality and surface smoothness. Furthermore, quantum wells with longer emission wavelengths have relatively higher In content in their InGaN material, leading to increased defects due to mismatch stress caused by well-barrier mismatch. Additionally, high-In-content InGaN materials require lower growth temperatures, further increasing defects in the grown epitaxial film. Therefore, the growth sequence of the multi-quantum-well light-emitting layer 5 is designed to first deposit and grow long-wavelength quantum wells and then deposit and grow short-wavelength quantum wells. Using the multi-band LED chip prepared by this invention, it is easier to obtain a high-quality multi-band multi-quantum-well light-emitting layer 5, thereby improving the radiative recombination efficiency of the active region and further improving the luminous efficacy of the multi-band LED chip.

[0072] Further explanation: Based on the fact that the bandgap width of the barrier layer in the first long-wavelength blue light multi-quantum-well emitting layer 51 is greater than the bandgap width of the barrier layer in the second medium-wavelength blue light multi-quantum-well emitting layer 52, and the bandgap width of the barrier layer in the third short-wavelength blue light multi-quantum-well emitting layer 53 is greater than or equal to the bandgap width of the barrier layer in the fourth short-wavelength blue light multi-quantum-well emitting layer 54, this structural design allows the energy band design of the barrier layer of the multi-quantum-well emitting layer 5 of the present invention to use a low-bandgap barrier layer material near the P-type semiconductor layer 7 and a high-bandgap barrier layer material near the N-type semiconductor layer 3. The low-bandgap barrier layer material can effectively reduce the blocking effect of the quantum barrier layer material on hole injection in the P-type semiconductor layer 7, increase the hole concentration injected into the active region from the P-type semiconductor layer 7, and allow the quantum wells near the N-type semiconductor layer 3 to also participate in light emission, significantly improving the matching degree of electron-hole concentration in the multi-quantum-well emitting layer 5, and improving the brightness and luminous efficacy of the multi-band LED chip. Meanwhile, the high bandgap barrier material can confine electrons in front of the first long-wavelength blue light multi-quantum well light-emitting layer 51 and the second medium-wavelength blue light multi-quantum well light-emitting layer 52, thereby blocking electrons and reducing their migration rate. This effectively prevents electron overflow and prevents electrons from being injected into the P-type semiconductor layer 7 to cause electron leakage, thus improving the yield and other performance of multi-band LED chips.

[0073] This invention optimizes and improves the LED epitaxial structure. The multi-band LED epitaxial structure of this invention can generate blue light in three bands: long-wave, medium-wave, and short-wave. Using this epitaxial structure, multi-band LED chips can be fabricated. The multi-band LED chips can be used to excite a red and green mixed phosphor layer to generate a full-spectrum white LED light source. The proportion of short-wave blue light is small, which causes less damage to human retinal cells and is closer to the solar spectrum, thus realizing a healthy full-spectrum white LED light source with a high color rendering index.

[0074] In one embodiment, the well layer of the first long-wavelength blue light multi-quantum-well emitting layer 51 is a first InGaN well layer 511, the well layer of the second mid-wavelength blue light multi-quantum-well emitting layer 52 is a second InGaN well layer 521, the well layer of the third short-wavelength blue light multi-quantum-well emitting layer 53 is a third InGaN well layer 531, and the well layer of the fourth short-wavelength blue light multi-quantum-well emitting layer 54 is a fourth InGaN well layer 541; preferably, the first InGaN well layer 511, the second InGaN well layer 521, the third InGaN well layer 531, and the fourth InGaN well layer 541 are all single-layer or multi-layer InGaN structures without intentional doping;

[0075] The In composition percentage of the first InGaN well layer 511 > the In composition percentage of the second InGaN well layer 521 > the In composition percentage of the third InGaN well layer 531 = the In composition percentage of the fourth InGaN well layer 541. Based on the above design of the epitaxial structure, the LED chip fabricated using the epitaxial structure of this invention has three wavelength bands for its excitation light source: long-wavelength blue light, medium-wavelength blue light, and short-wavelength blue light.

[0076] In one embodiment, the emission wavelength (λ1) of the first long-wavelength blue light multi-quantum-well emitting layer 51 is 460nm~480nm; λ1 is exemplary to be 460nm, 462nm, 465nm, 468nm, 470nm, 473nm, 475nm, 478nm or 480nm, but is not limited thereto;

[0077] The emission wavelength (λ2) of the second mid-wave blue multi-quantum well light-emitting layer 52 is 445nm~460nm; λ1 is exemplary 445nm, 448nm, 450nm, 452nm, 455nm, 458nm or 460nm, but is not limited thereto;

[0078] The emission wavelength (λ3) of the third short-wavelength blue light multi-quantum-well emitting layer 53 is 430nm~445nm; λ3 is exemplarily 430nm, 433nm, 435nm, 437nm, 440nm, 442nm or 445nm, but is not limited thereto;

[0079] The emission wavelength (λ4) of the fourth short-wavelength blue light quantum well light-emitting layer 54 is 430nm~445nm. λ4 is exemplarily 430nm, 433nm, 435nm, 437nm, 440nm, 442nm or 445nm, but is not limited thereto.

[0080] In the multi-band LED epitaxial structure of this invention, λ1>λ2>λ3=λ4. Using the multi-band LED epitaxial structure of this invention, multi-band LED chips can be fabricated. The excitation light source has three wavelengths. By using a blue light excitation light source with three wavelengths to excite a red and green mixed phosphor layer, a full-spectrum white LED light source is generated. Compared with a blue light LED chip with only one wavelength, the proportion of short-wavelength blue light below 450nm is small, which causes less damage to human retinal cells. Moreover, since the excitation light source has three wavelengths, the generated full-spectrum white light is closer to the solar spectrum, thereby realizing a healthy full-spectrum white LED light source with a high color rendering index.

[0081] In one embodiment, the In composition ratio of the first InGaN well layer 511 is 0.16~0.19, the growth thickness is 2.03nm~4.87nm, the growth temperature is 750℃~930℃, and the pressure is 50torr~360torr. Specifically, the In composition ratio of the first InGaN well layer 511 is, for example, 0.16, 0.17, 0.18, or 0.19; the growth thickness is, for example, 2.03 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 4.6 nm, or 4.87 nm; the growth temperature is, for example, 750°C, 780°C, 795°C, 800°C, 805°C, 810°C, 815°C, 820°C, 825°C, or 930°C; and the pressure is, for example, 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but is not limited thereto.

[0082] In one embodiment, the In composition ratio of the second InGaN well layer 521 is 0.13~0.16, the growth thickness is 2.03nm~4.87nm, the growth temperature is 770℃~930℃, and the pressure is 50torr~360torr. Specifically, the In composition ratio of the second InGaN well layer 521 is, for example, 0.13, 0.14, 0.15, or 0.16; the growth thickness is, for example, 2.03 nm, 2.5 nm, 3 nm, 3.5 nm, 3.55 nm, 4 nm, 4.5 nm, 4.6 nm, or 4.87 nm; the growth temperature is, for example, 770°C, 795°C, 800°C, 805°C, 810°C, 815°C, 820°C, 825°C, 850°C, or 930°C; and the pressure is, for example, 50 torr, 100 torr, 110 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but is not limited thereto.

[0083] In one embodiment, the In composition ratio of the third InGaN well layer 531 is 0.10~0.13, the growth thickness is 2.03nm~4.87nm, the growth temperature is 790℃~930℃, and the pressure is 50torr~360torr. Specifically, the In composition ratio of the third InGaN well layer 531 is, for example, 0.10, 0.101, 0.12, or 0.13; the growth thickness is, for example, 2.03 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 4.6 nm, or 4.87 nm; the growth temperature is, for example, 790°C, 800°C, 805°C, 810°C, 815°C, 820°C, 825°C, 850°C, or 930°C; and the pressure is, for example, 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but is not limited thereto.

[0084] In one embodiment, the fourth InGaN well layer 541 has an In composition ratio of 0.10~0.13, a growth thickness of 2.03nm~4.87nm, a growth temperature of 790℃~930℃, and a pressure of 50torr~360torr. Specifically, the In composition ratio of the fourth InGaN well layer 541 is, for example, 0.10, 0.101, 0.12, or 0.13; the growth thickness is, for example, 2.03 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 4.6 nm, or 4.87 nm; the growth temperature is, for example, 790°C, 800°C, 805°C, 810°C, 815°C, 820°C, 825°C, 850°C, or 930°C; and the pressure is, for example, 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but is not limited thereto.

[0085] In one embodiment, a first N-type carrier modulation insertion layer 5121 is provided in the barrier layer of the first long-wavelength blue light multi-quantum well light-emitting layer 51. The first N-type carrier modulation insertion layer 5121 includes a first AlGaN insertion layer 51211 and a first Si-doped GaN insertion layer 51212 that are periodically and alternately stacked.

[0086] The barrier layer of the second mid-wave blue light multi-quantum well light-emitting layer 52 is provided with a second N-type carrier modulation insertion layer 5221; the second N-type carrier modulation insertion layer 5221 includes a periodically alternating second AlGaN insertion layer 52211 and a second Si-doped GaN insertion layer 52212.

[0087] The barrier layer of the third short-wavelength blue light multi-quantum well light-emitting layer 53 is provided with a third N-type carrier modulation insertion layer 5321; the third N-type carrier modulation insertion layer 5321 includes a periodically alternating stacked third AlGaN insertion layer 53211 and a third Si-doped GaN insertion layer 53212.

[0088] The Al composition ratio of the first AlGaN insertion layer 51211 is greater than that of the second AlGaN insertion layer 52211, which is greater than that of the third AlGaN insertion layer 53211; the growth thickness of the first AlGaN insertion layer 51211 is greater than that of the second AlGaN insertion layer 52211, which is greater than that of the third AlGaN insertion layer 53211.

[0089] In one embodiment, the P-type carrier control insertion layer 5421 includes a front hole injection protection layer 54211, a hole injection control layer 54212 and a rear hole injection protection layer 54213 stacked sequentially.

[0090] Both the front hole injection protective layer 54211 and the rear hole injection protective layer 54213 are made of AlGaN material, and the Al composition ratio of the AlGaN material in the front hole injection protective layer 54211 and the rear hole injection protective layer 54213 is less than the Al composition ratio of the second AlGaN insertion layer 52211; the hole injection control layer 54212 is made of AlGaInN material and is doped with Mg element.

[0091] Based on the structural design of the first N-type carrier control insertion layer 5121, the second N-type carrier control insertion layer 5221, the third N-type carrier control insertion layer 5321, and the P-type carrier control insertion layer 5421, the energy band of the barrier material of the multi-quantum-well light-emitting layer 5 of this invention is designed such that the AlGaN barrier material with a low bandgap and low Al content is used near the P-type semiconductor layer 7, and the AlGaN barrier material with a high bandgap and high Al content is used near the N-type semiconductor layer 3. The low bandgap barrier material (the AlGaN material in the third N-type carrier control insertion layer 5321 and the P-type carrier control insertion layer 5421) can effectively reduce the blocking effect of the quantum barrier material on hole injection in the P-type semiconductor layer 7, increase the hole concentration injected into the active region from the P-type semiconductor layer 7, and allow the quantum wells near the N-type semiconductor layer 3 to also participate in light emission, significantly improving the matching degree of electron and hole concentrations in the multi-quantum-well light-emitting layer 5, and improving the brightness and luminous efficacy of the multi-band LED chip. Meanwhile, the high bandgap barrier material (AlGaN material in the first N-type carrier control insertion layer 5121 and the second N-type carrier control insertion layer 5221) can bind electrons in front of the AlGaN material in the first N-type carrier control insertion layer 5121 and the second N-type carrier control insertion layer 5221, thereby blocking electrons and reducing their mobility. This effectively prevents electrons from overflowing and being injected into the P-type semiconductor layer 7, thus preventing electron leakage and improving the yield and other performance of multi-band LED chips.

[0092] Further explanation: the first N-type carrier control insertion layer 5121, the second N-type carrier control insertion layer 5221, and the third N-type carrier control insertion layer 5321 are all AlGaN / GaN superlattice structure materials. The first Si-doped GaN insertion layer 51212, the second Si-doped GaN insertion layer 52212, and the third Si-doped GaN insertion layer 53212 are doped with Si elements. The P-type carrier control insertion layer 5421 includes three sublayers stacked sequentially: a front hole injection protection layer 54211, a hole injection control layer 54212, and a rear hole injection protection layer 54213. The hole injection control layer 54212 is made of AlGaInN material and doped with Mg elements. It can provide some holes to the multi-quantum well light-emitting layer 5 to participate in radiative recombination luminescence, thereby improving the brightness and luminous efficiency of the multi-band LED chip. This invention achieves the control of the band barrier height and current spread performance of the barrier material in the multi-quantum-well light-emitting layer 5 by adjusting the material composition ratio and doping type in the first N-type carrier control insertion layer 5121, the second N-type carrier control insertion layer 5221, the third N-type carrier control insertion layer 5321, and the P-type carrier control insertion layer 5421. This results in the control of the electron-hole concentration distribution in the multi-quantum-well light-emitting layer 5 and the improvement of the hole injection efficiency of the P-type semiconductor layer 7, thereby improving the luminous efficacy of the multi-band LED chip.

[0093] Preferably, the number of cycles in which the first N-type carrier control insertion layer 5121, the second N-type carrier control insertion layer 5221, and the third N-type carrier control insertion layer 5321 are alternately grown is 2 to 10, and exemplarily 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0094] In one embodiment, the Al composition ratio of the first AlGaN insertion layer 51211 is 0.03~0.30, the growth thickness is 0.6nm~3.0nm, the growth temperature is 818℃~935℃, and the pressure is 50torr~360torr. Specifically, the Al composition ratio of the first AlGaN insertion layer 51211 is exemplarily 0.03, 0.05, 0.08, 0.09, 0.1, 0.13, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, or 0.30, and the growth thickness is exemplarily 0.6nm or 0.8nm. The growth wavelengths are 0.9nm, 1nm, 1.2nm, 1.5nm, 2nm, 2.2nm, 2.5nm, 2.8nm, or 3.0nm, with exemplary growth temperatures of 818°C, 830°C, 850°C, 880°C, 900°C, or 935°C, and exemplary pressures of 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but are not limited thereto.

[0095] The second AlGaN insertion layer 52211 has an Al composition ratio of 0.02~0.21, a growth thickness of 0.5nm~2.7nm, a growth temperature of 818℃~935℃, and a pressure of 50 torr~360 torr. Specifically, the Al composition ratio of the second AlGaN insertion layer 52211 is exemplarily 0.02, 0.03, 0.05, 0.08, 0.09, 0.1, 0.13, 0.15, 0.18, 0.2, or 0.21, and the growth thickness is exemplarily 0.5nm, 0.6nm, 0.8nm, or 0.21. The growth wavelengths are 0.9nm, 1nm, 1.2nm, 1.5nm, 2nm, 2.2nm, 2.5nm, or 2.7nm, with exemplary growth temperatures of 818°C, 830°C, 850°C, 880°C, 900°C, or 935°C, and exemplary pressures of 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but are not limited thereto.

[0096] The third AlGaN insertion layer 53211 has an Al composition ratio of 0.01~0.15, a growth thickness of 0.3nm~2.2nm, a growth temperature of 818℃~935℃, and a pressure of 50 torr~360 torr; specifically, the Al composition ratio of the third AlGaN insertion layer 53211 is exemplarily 0.01, 0.02, 0.03, 0.05, 0.08, 0.09, 0.1, 0.13, or 0.15, and the growth thickness is exemplarily 0.3nm, 0.5nm, 0.6nm, or 0.8nm. The growth wavelengths are 0.9 nm, 1 nm, 1.2 nm, 1.5 nm, 2 nm, or 2.2 nm, with exemplary growth temperatures of 818°C, 830°C, 850°C, 880°C, 900°C, or 935°C, and exemplary pressures of 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but not limited thereto.

[0097] The first Si-doped GaN insertion layer 51212, the second Si-doped GaN insertion layer 52212, and the third Si-doped GaN insertion layer 53212 are all doped with Si, with Si doping concentrations of 2.58 × 10⁻⁶. 17 / cm 3 ~9.73×10 17 / cm 3 The growth thicknesses range from 0.3 nm to 3 nm, the growth temperatures range from 818 °C to 935 °C, and the pressures range from 50 torr to 360 torr. Specifically, the Si doping concentrations of the first Si-doped GaN insertion layer 51212, the second Si-doped GaN insertion layer 52212, and the third Si-doped GaN insertion layer 53212 are, for example, 2.58 × 10⁻⁶. 17 / cm 3 3×10 17 / cm 3 3.5×10 17 / cm 3 4×10 17 / cm 3 4.5×10 17 / cm 3 5×10 17 / cm 3 5.5×10 17 / cm 3 6×10 17 / cm 3 6.5×10 17 / cm 3 7×1017 / cm 3 7.5×10 17 / cm 3 8×10 17 / cm 3 9×10 17 / cm 3 Or 9.73×10 17 / cm 3 The growth thickness is 0.3nm, 0.6nm, 0.8nm, 0.9nm, 1nm, 1.2nm, 1.5nm, 2nm, 2.2nm, 2.5nm, 2.8nm or 3.0nm, respectively; the growth temperature is 818℃, 830℃, 850℃, 880℃, 900℃ or 935℃, respectively; and the pressure is 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr or 360 torr, respectively, but is not limited thereto.

[0098] Both the pre-hole injection protective layer 54211 and the post-hole injection protective layer 54213 are undoped AlGaN materials with Al composition ratios of 0.01~0.18, growth thicknesses of 0.3nm~2.5nm, growth temperatures of 818℃~935℃, and pressures of 50 torr~360 torr. Specifically, the Al composition ratios in the pre-hole injection protective layer 54211 and the post-hole injection protective layer 54213 are exemplarily 0.01, 0.02, 0.03, 0.05, 0.08, 0.09, 0.1, 0.13, 0.15, or 0.18, and the growth thicknesses are... Examples of growth wavelengths are 0.3nm, 0.5nm, 0.8nm, 1nm, 1.3nm, 1.5nm, 1.8nm, 2nm, 2.3nm, or 2.5nm, respectively; examples of growth temperatures are 818℃, 830℃, 850℃, 880℃, 900℃, or 935℃, respectively; and examples of pressures are 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, respectively, but are not limited thereto.

[0099] The hole injection control layer 54212 is an AlInGaN material doped with Mg, with an Al content of 0.01~0.15%, an In content of 0.02~0.15%, a thickness of 0.6nm~8.5nm, and a Mg doping concentration of 3.15×10⁻⁶.18 / cm 3 ~8.69×10 19 / cm 3 The growth temperature is 818℃~935℃, and the pressure is 50 torr~360 torr. Specifically, the Al component ratio in the hole injection control layer 54212 is exemplarily 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, or 0.15; the In component ratio is exemplarily 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, or 0.15; and the Mg doping concentration is exemplarily 3.15 × 10⁻⁶. 18 / cm 3 5×10 18 / cm 3 8×10 18 / cm 3 1×10 19 / cm 3 3×10 19 / cm 3 6.8×10 19 / cm 3 Or 8.69×10 19 / cm 3 The growth temperatures are 818℃, 830℃, 850℃, 880℃, 900℃, and 935℃, respectively, and the pressures are 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, respectively, but are not limited thereto.

[0100] In one embodiment, the barrier layer of the first long-wavelength blue light-emitting multi-quantum-well emitting layer 51 is a first barrier layer 512, and the first barrier layer 512 further includes several first GaN layers 5122. The first N-type carrier modulation insertion layer 5121 is inserted between the several first GaN layers 5122. The first GaN layers 5122 are doped with Si element, and the Si doping concentration is 1.9 × 10⁻⁶. 17 / cm 3 ~8.5×10 17 / cm 3The growth thickness is 5.6 nm to 13.8 nm, the growth temperature is 818 °C to 935 °C, and the pressure is 50 torr to 360 torr. Specifically, the growth thickness of the first GaN layer 5122 is exemplarily 5.6 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, or 13.8 nm, and the Si doping concentration is exemplarily 1.9 × 10⁻⁶. 17 / cm 3 2.5×10 17 / cm 3 3×10 17 / cm 3 3.5×10 17 / cm 3 4×10 17 / cm 3 4.5×10 17 / cm 3 5×10 17 / cm 3 6×10 17 / cm 3 7×10 17 / cm 3 8×10 17 / cm 3 Or 8.5×10 17 / cm 3 The growth temperature is exemplarily 818℃, 830℃, 850℃, 880℃, 900℃, 935℃, and the pressure is exemplarily 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but is not limited thereto.

[0101] In one embodiment, the first GaN layer 5122 has two layers, and the first N-type carrier modulation insertion layer 5121 is disposed between the two first GaN layers 5122.

[0102] The barrier layer of the second mid-wave blue light multi-quantum well emitting layer 52 is a second barrier layer 522. The second barrier layer 522 further includes several second GaN layers 5222. The second N-type carrier modulation insertion layer 5221 is inserted between the several second GaN layers 5222. The second GaN layers 5222 are doped with Si element, and the Si doping concentration is 1.5 × 10⁻⁶. 17 / cm 3 ~7.3×10 17 / cm 3The growth thickness is 5.6 nm to 13.8 nm, the growth temperature is 818 °C to 935 °C, and the pressure is 50 torr to 360 torr. Specifically, the growth thickness of the second GaN layer 5222 is exemplarily 5.6 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, or 13.8 nm, and the Si doping concentration is exemplarily 1.5 × 10⁻⁶. 17 / cm 3 1.9×10 17 / cm 3 2.5×10 17 / cm 3 3×10 17 / cm 3 3.5×10 17 / cm 3 3.8×10 17 / cm 3 4×10 17 / cm 3 4.5×10 17 / cm 3 5×10 17 / cm 3 5.5×10 17 / cm 3 6×10 17 / cm 3 7×10 17 / cm 3 Or 7.3×10 17 / cm 3 The growth temperature is exemplarily 818℃, 830℃, 850℃, 880℃, 900℃, 935℃, and the pressure is exemplarily 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but is not limited thereto.

[0103] In one embodiment, the second GaN layer 5222 has two layers, and the second N-type carrier modulation insertion layer 5221 is disposed between the two first GaN layers 5122.

[0104] The barrier layer of the third short-wavelength blue light-emitting multi-quantum-well emitting layer 53 is a third barrier layer 532, which further includes several third GaN layers 5322. The third N-type carrier modulation insertion layer 5321 is inserted between the several third GaN layers 5322. The third GaN layers 5322 are doped with Si, and the Si doping concentration is 1.2 × 10⁻⁶. 17 / cm 3 ~6.1×10 17 / cm 3 The growth thickness is 5.6 nm to 13.8 nm, the growth temperature is 818 °C to 935 °C, and the pressure is 50 torr to 360 torr. Specifically, the growth thickness of the third GaN layer 5322 is exemplarily 5.6 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, or 13.8 nm, and the Si doping concentration is exemplarily 1.2 × 10⁻⁶. 17 / cm 3 1.5×10 17 / cm 3 1.9×10 17 / cm 3 2.5×10 17 / cm 3 3×10 17 / cm 3 3.5×10 17 / cm 3 3.8×10 17 / cm 3 4×10 17 / cm 3 4.5×10 17 / cm 3 5×10 17 / cm 3 5.5×10 17 / cm 3 6×10 17 / cm 3 6.1×10 17 / cm 3 The growth temperature is exemplarily 818℃, 830℃, 850℃, 880℃, 900℃, 935℃, and the pressure is exemplarily 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr, or 360 torr, but is not limited thereto.

[0105] In one embodiment, the third GaN layer 5322 has two layers, and the third N-type carrier modulation insertion layer 5321 is disposed between the two third GaN layers 5322.

[0106] The barrier layer of the fourth short-wavelength blue light-emitting quantum well emitting layer 54 is a fourth barrier layer 542. The fourth barrier layer 542 further includes several fourth GaN layers 5422. The P-type carrier modulation insertion layer 5421 is inserted between the several fourth GaN layers 5422. The fourth GaN layers 5422 are not intentionally doped. The growth thickness of the fourth GaN layers 5422 is 5.6 nm to 13.8 nm, the growth temperature is 818 °C to 935 °C, and the pressure is 50 torr to 360 torr. Specifically, the growth thickness of the fourth GaN layer 5422 is exemplarily 5.6nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm or 13.8nm, the growth temperature is exemplarily 818℃, 830℃, 850℃, 880℃, 900℃ or 935℃, and the pressure is exemplarily 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 230 torr, 250 torr, 270 torr, 300 torr, 320 torr or 360 torr, but is not limited thereto.

[0107] In one embodiment, the fourth GaN layer 5422 has two layers, and the P-type carrier modulation insertion layer 5421 is disposed between the two fourth GaN layers 5422.

[0108] Preferably, the Si doping concentration of the first GaN layer 5122 is greater than or equal to the Si doping concentration of the third GaN layer 5322, so as to further improve the luminous efficacy of the LED chip.

[0109] Accordingly, this embodiment also provides a method for fabricating a multi-band LED epitaxial structure, including:

[0110] Substrate 1 is selected;

[0111] A buffer layer 2, an N-type semiconductor layer 3, a low-temperature stress relief layer 4, a multi-quantum well light-emitting layer 5, an electron blocking layer 6, and a P-type semiconductor layer 7 are sequentially deposited on substrate 1.

[0112] The multi-quantum-well light-emitting layer 5 includes a first long-wavelength blue light multi-quantum-well light-emitting layer 51, a second medium-wavelength blue light multi-quantum-well light-emitting layer 52, a third short-wavelength blue light multi-quantum-well light-emitting layer 53, and a fourth short-wavelength blue light final quantum-well light-emitting layer 54, which are stacked sequentially along the epitaxial direction.

[0113] The emission wavelength of the first long-wavelength blue light multi-quantum-well emitting layer 51 is greater than that of the second medium-wavelength blue light multi-quantum-well emitting layer 52, which is greater than that of the third short-wavelength blue light multi-quantum-well emitting layer 53, which equals the emission wavelength of the fourth short-wavelength blue light multi-quantum-well emitting layer 54.

[0114] The first long-wavelength blue light multi-quantum-well emitting layer 51, the second medium-wavelength blue light multi-quantum-well emitting layer 52, the third short-wavelength blue light multi-quantum-well emitting layer 53, and the fourth short-wavelength blue light final quantum-well emitting layer 54 are all periodic structures formed by alternating stacking of well layers and barrier layers.

[0115] The bandgap width of the barrier layer in the first long-wavelength blue light multi-quantum-well emitting layer 51 is greater than the bandgap width of the barrier layer in the second medium-wavelength blue light multi-quantum-well emitting layer 52, which is greater than the bandgap width of the barrier layer in the third short-wavelength blue light multi-quantum-well emitting layer 53, which is greater than or equal to the bandgap width of the barrier layer in the fourth short-wavelength blue light final quantum-well emitting layer 54.

[0116] The fourth short-wavelength blue light quantum well light-emitting layer 54 has a P-type carrier modulation insertion layer 5421 in its barrier layer, and the P-type carrier modulation insertion layer 5421 is doped with Mg element.

[0117] This embodiment further optimizes and studies the structure and process of blue LED chips, enabling the fabrication of multi-band LED epitaxial structures, thereby obtaining multi-band LED chips. By using the multi-band LED chips of this embodiment to excite the red and green mixed phosphor layer, a full-spectrum white LED light source that causes less damage to human retinal cells, is healthier, has a high color rendering index, and is closer to the solar spectrum can be generated.

[0118] In one embodiment, the P-type carrier control insertion layer 5421 includes a front hole injection protection layer 54211, a hole injection control layer 54212 and a rear hole injection protection layer 54213 stacked sequentially.

[0119] Both the front hole injection protective layer 54211 and the rear hole injection protective layer 54213 are made of AlGaN material, and the hole injection control layer 54212 is made of AlGaInN material and is doped with Mg element.

[0120] After the deposition of the fourth short-wavelength blue light-emitting quantum well emitting layer 54 and the hole injection control layer 54212, surface roughening annealing is required. This involves intermittently and cyclically introducing a N2 / H2 mixed gas into the reaction chamber and stabilizing it for 5-96 seconds. The surface roughening annealing temperature is 830℃-1080℃, the pressure is 30 torr-500 torr, and the N2 / H2 mixed gas ratio (volume ratio) is 1:0.2-1:5. After surface roughening annealing, defects such as poor crystal quality and high-In-content In clusters on the material surface will be decomposed, which is beneficial to improving the crystal quality of the material. Simultaneously, the roughened material surface reduces in-plane total internal reflection and light absorption loss in the semiconductor material, improving light extraction efficiency and thus enhancing the luminous efficacy of multi-band LED chips.

[0121] Specifically, the surface roughening annealing temperature is exemplarily 830℃, 850℃, 880℃, 900℃, 950℃, 980℃, 1000℃, 1020℃, 1050℃, or 1080℃; the pressure is exemplarily 30 torr, 50 torr, 80 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 250 torr, or 280 torr. rr, 300 torr, 350 torr, 380 torr, 400 torr, 420 torr, 450 torr, 480 torr, 500 torr; the ratio (volume ratio) of N2 / H2 mixed gas is exemplarily 1:0.2, 1:0.5, 1:0.8, 1:1, 1:1.5, 1:1.8, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, but is not limited thereto.

[0122] Accordingly, this embodiment also provides a multi-band LED chip, which is prepared by using existing chip technology and conditions to fabricate the multi-band LED epitaxial structure described above.

[0123] Accordingly, this embodiment also provides a white LED light source, including a red-green mixed phosphor layer and the above-mentioned multi-band LED chip, wherein the red-green mixed phosphor layer includes red phosphor and green phosphor.

[0124] Understandably, red phosphor refers to phosphor that emits red light when excited, while green phosphor refers to phosphor that emits green light when excited.

[0125] For example, the red phosphor may be at least one of nitride red phosphor, oxynitride red phosphor, or fluoride red phosphor, such as CaAlSiN3:Eu 2+ Sr2Si5N8:Eu 2+ K2SiF6:Mn 4+ .

[0126] For example, the green phosphor may be at least one of silicate green phosphor, oxynitride green phosphor, or garnet-structured green phosphor, such as β-SiAlON:Eu 2+ Lu3Al5O 12 :Ce 3+ .

[0127] The multi-band LED chip of this invention can emit light in various wavelengths, including long-wave blue light, medium-wave blue light, and short-wave blue light. The synergistic effect of these different wavelengths can excite red and green phosphors, resulting in a full-spectrum white LED light source with a higher color rendering index, better stability, less damage to the human eye, and high luminous efficiency. The generated full-spectrum white light is closer to the solar spectrum, thus realizing a healthy full-spectrum white LED light source with a high color rendering index.

[0128] The technical solution of the present invention will be further described below through embodiments and comparative examples.

[0129] Example 1

[0130] This embodiment provides a multi-band LED epitaxial structure, including a substrate 1 and a buffer layer 2, an N-type semiconductor layer 3, a low-temperature stress relief layer 4, a multi-quantum well light-emitting layer 5, an electron blocking layer 6, and a P-type semiconductor layer 7 disposed on the substrate.

[0131] The multi-quantum-well light-emitting layer 5 includes a first long-wavelength blue light multi-quantum-well light-emitting layer 51, a second medium-wavelength blue light multi-quantum-well light-emitting layer 52, a third short-wavelength blue light multi-quantum-well light-emitting layer 53, and a fourth short-wavelength blue light final quantum-well light-emitting layer 54, which are stacked sequentially along the epitaxial direction.

[0132] The emission wavelength λ1 of the first long-wavelength blue light multi-quantum-well emitting layer 51 is greater than the emission wavelength λ2 of the second medium-wavelength blue light multi-quantum-well emitting layer 52, which is greater than the emission wavelength λ3 of the third short-wavelength blue light multi-quantum-well emitting layer 53. The emission wavelength λ4 of the fourth short-wavelength blue light final quantum-well emitting layer 54 is also greater than the emission wavelength λ4 of the third short-wavelength blue light final quantum-well emitting layer 54. In this embodiment, λ1 is 475nm, λ2 is 458nm, λ3 is 440nm, and λ4 is 440nm.

[0133] The first long-wavelength blue light multi-quantum-well emitting layer 51, the second medium-wavelength blue light multi-quantum-well emitting layer 52, the third short-wavelength blue light multi-quantum-well emitting layer 53, and the fourth short-wavelength blue light final-quantum-well emitting layer 54 are all periodic structures formed by alternating stacked well layers and barrier layers; the first long-wavelength blue light multi-quantum-well emitting layer 51 has 4 alternating growth periods, the second medium-wavelength blue light multi-quantum-well emitting layer 52 has 4 alternating growth periods, the third short-wavelength blue light multi-quantum-well emitting layer 53 has 3 alternating growth periods, and the fourth short-wavelength blue light final-quantum-well emitting layer 54 has 1 alternating growth period.

[0134] The first long-wavelength blue light multi-quantum-well emitting layer 51 has a first InGaN well layer 511, the second mid-wavelength blue light multi-quantum-well emitting layer 52 has a second InGaN well layer 521, the third short-wavelength blue light multi-quantum-well emitting layer 53 has a third InGaN well layer 531, and the fourth short-wavelength blue light multi-quantum-well emitting layer 54 has a fourth InGaN well layer 541; the In composition percentage of the first InGaN well layer 511 > the In composition percentage of the second InGaN well layer 521 > the In composition percentage of the third InGaN well layer 531 = the In composition percentage of the fourth InGaN well layer 541; in this embodiment, the first InGaN well layer 541 has an InGaN well layer 541. The first InGaN well layer 511 has an In content of 0.18%, a growth thickness of 3 nm, a growth temperature of 795 °C, and a pressure of 150 torr; the second InGaN well layer 521 has an In content of 0.16%, a growth thickness of 3.55 nm, a growth temperature of 820 °C, and a pressure of 110 torr; the third InGaN well layer 531 has an In content of 0.13%, a growth thickness of 3 nm, a growth temperature of 850 °C, and a pressure of 180 torr; and the fourth InGaN well layer 541 has an In content of 0.13%, a growth thickness of 3 nm, a growth temperature of 850 °C, and a pressure of 180 torr.

[0135] The barrier layer of the first long-wavelength blue light-emitting multi-quantum-well emitting layer 51 is a first barrier layer 512. The first barrier layer 512 has two first GaN layers 5122, and the first GaN layers 5122 are doped with Si element, with a Si doping concentration of 8.5 × 10⁻⁶. 17 / cm 3 The growth thickness is 10 nm, the growth temperature is 880 °C, and the pressure is 180 torr; a first N-type carrier control insertion layer 5121 is provided between the two first GaN layers 5122. The first N-type carrier control insertion layer 5121 includes a periodically alternating first AlGaN insertion layer 51211 and a first Si-doped GaN insertion layer 51212, with a period number of 3.

[0136] The barrier layer of the second mid-wave blue light-emitting multi-quantum-well emitting layer 52 is a second barrier layer 522, which has two second GaN layers 5222. The second GaN layers 5222 are doped with Si element, and the Si doping concentration is 7.3 × 10⁻⁶. 17 / cm 3 The growth thickness is 10 nm, the growth temperature is 880 °C, and the pressure is 150 torr; a second N-type carrier control insertion layer 5221 is provided between the two second GaN layers 5222. The second N-type carrier control insertion layer 5221 includes a periodically alternating second AlGaN insertion layer 52211 and a second Si-doped GaN insertion layer 52212, with a period number of 3.

[0137] The barrier layer of the third short-wavelength blue light-emitting multi-quantum-well emitting layer 53 is a third barrier layer 532. The third barrier layer 532 has two third GaN layers 5322, and the third GaN layers 5322 are doped with Si element, with a Si doping concentration of 6.1 × 10⁻⁶. 17 / cm 3 The growth thickness is 10 nm, the growth temperature is 860 °C, and the pressure is 150 torr; a third N-type carrier control insertion layer 5321 is provided between the two third GaN layers 5322. The third N-type carrier control insertion layer 5321 includes a periodically alternating stacked third AlGaN insertion layer 53211 and a third Si-doped GaN insertion layer 53212, with a period number of 3;

[0138] The Al composition percentage of the first AlGaN insertion layer 51211 is greater than that of the second AlGaN insertion layer 52211, which is greater than that of the third AlGaN insertion layer 53211; the growth thickness of the first AlGaN insertion layer 51211 is greater than that of the second AlGaN insertion layer 52211, which is greater than that of the third AlGaN insertion layer 53211; in this embodiment, the Al composition percentage of the first AlGaN insertion layer 51211 is 0.18, the growth thickness is 2 nm, the growth temperature is 850 °C, and the pressure is 180 torr; the Al composition percentage of the second AlGaN insertion layer 52211 is 0.15, the growth thickness is 1.8 nm, the growth temperature is 850 °C, and the pressure is 150 torr; the Al composition percentage of the third AlGaN insertion layer 53211 is 0.13, the growth thickness is 1.7 nm, the growth temperature is 880 °C, and the pressure is 180 torr;

[0139] The first Si-doped GaN insertion layer 51212, the second Si-doped GaN insertion layer 52212, and the third Si-doped GaN insertion layer 53212 are all doped with Si, with a Si doping concentration of 5.5 × 10⁻⁶. 17 / cm 3 The growth thickness was 2 nm, the growth temperature was 850℃, and the pressure was 180 torr.

[0140] The barrier layer of the fourth short-wavelength blue light quantum well emitting layer 54 is a fourth barrier layer 542. The fourth barrier layer 542 has two fourth GaN layers 5422. The fourth GaN layers 5422 are not intentionally doped, have a growth thickness of 10 nm, a growth temperature of 850 °C, and a pressure of 150 torr. A P-type carrier control insertion layer 5421 is provided between the two fourth GaN layers 5422. The P-type carrier control insertion layer 5421 includes a front hole injection protection layer 54211, a hole injection control layer 54212, and a rear hole injection protection layer 54213 stacked in sequence.

[0141] Both the pre-hole injection protective layer 54211 and the post-hole injection protective layer 54213 are made of undoped AlGaN material. The Al content of the AlGaN material in both layers is less than that in the second AlGaN insertion layer 52211. In this embodiment, the Al content of both the pre-hole injection protective layer 54211 and the post-hole injection protective layer 54213 is 0.13, the growth thickness is 1 nm, the growth temperature is 880 °C, and the pressure is 180 torr. The hole injection control layer 54212 is made of AlGaInN material and doped with Mg. The Al content of the hole injection control layer 54212 is 0.11, the In content is 0.10, the thickness is 5 nm, and the Mg doping concentration is 6.8 × 10⁻⁶. 19 / cm 3 The growth temperature is 880℃ and the pressure is 180 torr.

[0142] The fabrication method of the multi-band LED epitaxial structure in this embodiment includes the following steps:

[0143] (1) Select substrate 1;

[0144] (2) A buffer layer 2, an N-type semiconductor layer 3, a low-temperature stress relief layer 4, a multi-quantum well light-emitting layer 5, an electron blocking layer 6 and a P-type semiconductor layer 7 are sequentially deposited on substrate 1;

[0145] After the deposition of the fourth short-wavelength blue light-emitting quantum well emitting layer 54 (i.e., the fourth InGaN well layer 541) and the hole injection control layer 54212, a surface roughening annealing treatment is required. This involves intermittently and cyclically introducing a N2 / H2 mixed gas into the reaction chamber and stabilizing it for 50 seconds. The surface roughening annealing treatment temperature is 920℃, the pressure is 200 torr, and the ratio of the N2 / H2 mixed gas is 1:2.

[0146] Example 2

[0147] This embodiment provides a multi-band LED epitaxial structure, which is basically the same as that in Embodiment 1, except that: in Embodiment 2, the Al composition ratio of the first AlGaN insertion layer 51211 is 0.25, the growth thickness is 2.5 nm, the growth temperature is 880 °C, and the pressure is 220 torr; the Al composition ratio of the second AlGaN insertion layer 52211 is 0.20, the growth thickness is 2.2 nm, the growth temperature is 850 °C, and the pressure is 180 torr; the Al composition ratio of the third AlGaN insertion layer 53211 is 0.1, the growth thickness is 1.5 nm, the growth temperature is 850 °C, and the pressure is 150 torr; the Al composition ratio of the front hole injection protective layer 54211 is 0.1, the growth thickness is 1 nm, the growth temperature is 850 °C, and the pressure is 150 torr; the Al composition ratio of the rear hole injection protective layer 54213 is 0.08, the growth thickness is 0.8 nm, the growth temperature is 850 °C, and the pressure is 150 torr.

[0148] Example 3

[0149] This embodiment provides a multi-band LED epitaxial structure, which is basically the same as that in Embodiment 1, except that:

[0150] In Example 3, the first InGaN well layer 511 has an In composition ratio of 0.17, a growth thickness of 3.5 nm, a growth temperature of 805 °C, and a pressure of 150 torr; the second InGaN well layer 521 has an In composition ratio of 0.15, a growth thickness of 3.5 nm, a growth temperature of 835 °C, and a pressure of 110 torr; the third InGaN well layer 531 has an In composition ratio of 0.11, a growth thickness of 2.5 nm, a growth temperature of 865 °C, and a pressure of 150 torr; and the fourth InGaN well layer 541 has an In composition ratio of 0.11, a growth thickness of 2.5 nm, a growth temperature of 865 °C, and a pressure of 150 torr.

[0151] The first GaN layer (5122) has a growth thickness of 13.8 nm and a Si doping concentration of 5.5 × 10⁻⁶. 17 / cm 3 The second GaN layer (5222) has a growth thickness of 8 nm and a Si doping concentration of 4.5 × 10⁻⁶. 17 / cm 3 The third GaN layer (5322) has a growth thickness of 9 nm and a Si doping concentration of 3.8 × 10⁻⁶. 17 / cm 3 The fourth GaN layer, 5422, has a growth thickness of 8 nm.

[0152] The first long-wavelength blue light multi-quantum-well emitting layer 51 has an emission wavelength λ1 of 470 nm, the second medium-wavelength blue light multi-quantum-well emitting layer 52 has an emission wavelength λ2 of 452 nm, the third short-wavelength blue light multi-quantum-well emitting layer 53 has an emission wavelength λ3 of 435 nm, and the fourth short-wavelength blue light multi-quantum-well emitting layer 54 has an emission wavelength λ4 of 435 nm.

[0153] Comparative Example 1

[0154] This comparative example provides an LED epitaxial structure. The difference between this comparative example and Example 1 is that the multi-quantum well light-emitting layer of this comparative example is only provided with a third short-wavelength blue multi-quantum well light-emitting layer, and the number of alternating growth cycles of the third short-wavelength blue multi-quantum well light-emitting layer is 12.

[0155] Comparative Example 2

[0156] This comparative example provides a multi-band LED epitaxial structure, which is basically the same as that in Example 1. The difference is that the Al composition ratio and growth thickness of the first AlGaN insertion layer, the second AlGaN insertion layer, the third AlGaN insertion layer, the front hole injection protection layer and the rear hole injection protection layer in Comparative Example 2 are all the same, with the Al composition ratio being 0.25 and the growth thickness being 2.5 nm.

[0157] Comparative Example 3

[0158] This comparative example provides a multi-band LED epitaxial structure, which is basically the same as that of Example 1, except that: in Comparative Example 3, a fourth short-wavelength blue light quantum well emitting layer 54, a third short-wavelength blue light quantum well emitting layer 53, a second medium-wavelength blue light quantum well emitting layer 52, and a first long-wavelength blue light quantum well emitting layer 51 are sequentially deposited on the surface of the low-temperature stress relief layer 4. That is, the multi-quantum well emitting layer 5 includes the fourth short-wavelength blue light quantum well emitting layer 54, the third short-wavelength blue light quantum well emitting layer 53, the second medium-wavelength blue light quantum well emitting layer 52, and the first long-wavelength blue light quantum well emitting layer 51, which are sequentially stacked along the epitaxial direction; and after the well layer (i.e., the fourth InGaN well layer) of the fourth short-wavelength blue light quantum well emitting layer and the hole injection control layer are deposited, Comparative Example 3 does not perform surface roughening annealing treatment.

[0159] The electrical parameters of Examples 1 to 3 and Comparative Examples 1 to 3 were tested, and the luminous efficiency improvement rate of the remaining experimental groups relative to Comparative Example 1 was calculated. The color rendering performance of each experimental group was also tested. The test results are as follows:

[0160]

[0161] Experimental results show that, compared with Comparative Examples 1 to 3, Examples 1 to 3 using the multi-quantum-well emitting layer design of the present invention have higher color rendering performance and luminous efficiency.

[0162] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A multi-band LED epitaxial structure, characterized in that, The substrate and the buffer layer, the N-type semiconductor layer, the low-temperature stress release layer, the multi-quantum well light-emitting layer, the electron blocking layer, and the P-type semiconductor layer arranged on the substrate; The multi-quantum well light-emitting layer comprises a first long-wave blue light multi-quantum well light-emitting layer, a second middle-wave blue light multi-quantum well light-emitting layer, a third short-wave blue light multi-quantum well light-emitting layer, and a fourth short-wave blue light multi-quantum well light-emitting layer which are sequentially stacked along the epitaxial direction; The light-emitting wavelength of the first long-wave blue light multi-quantum well light-emitting layer > the light-emitting wavelength of the second middle-wave blue light multi-quantum well light-emitting layer > the light-emitting wavelength of the third short-wave blue light multi-quantum well light-emitting layer = the light-emitting wavelength of the fourth short-wave blue light multi-quantum well light-emitting layer; The first long-wave blue light multi-quantum well light-emitting layer, the second middle-wave blue light multi-quantum well light-emitting layer, the third short-wave blue light multi-quantum well light-emitting layer, and the fourth short-wave blue light multi-quantum well light-emitting layer all have a periodic structure formed by alternately stacking well layers and barrier layers; The band gap of the barrier layer in the first long-wave blue light multi-quantum well light-emitting layer > the band gap of the barrier layer in the second middle-wave blue light multi-quantum well light-emitting layer > the band gap of the barrier layer in the third short-wave blue light multi-quantum well light-emitting layer ≥ the band gap of the barrier layer in the fourth short-wave blue light multi-quantum well light-emitting layer; The barrier layer in the fourth short-wave blue light multi-quantum well light-emitting layer is provided with a P-type carrier regulation insertion layer, and the P-type carrier regulation insertion layer is doped with Mg elements; The barrier layer in the first long-wave blue light multi-quantum well light-emitting layer is provided with a first N-type carrier regulation insertion layer, and the first N-type carrier regulation insertion layer comprises periodically and alternately stacked first AlGaN insertion layers and first Si-doped GaN insertion layers; The barrier layer in the second middle-wave blue light multi-quantum well light-emitting layer is provided with a second N-type carrier regulation insertion layer, and the second N-type carrier regulation insertion layer comprises periodically and alternately stacked second AlGaN insertion layers and second Si-doped GaN insertion layers; The barrier layer in the third short-wave blue light multi-quantum well light-emitting layer is provided with a third N-type carrier regulation insertion layer, and the third N-type carrier regulation insertion layer comprises periodically and alternately stacked third AlGaN insertion layers and third Si-doped GaN insertion layers; The Al component proportion of the first AlGaN insertion layer > the Al component proportion of the second AlGaN insertion layer > the Al component proportion of the third AlGaN insertion layer, and the growth thickness of the first AlGaN insertion layer > the growth thickness of the second AlGaN insertion layer > the growth thickness of the third AlGaN insertion layer; The P-type carrier regulation insertion layer comprises a front hole injection protection layer, a hole injection regulation layer, and a rear hole injection protection layer which are sequentially stacked; The front hole injection protection layer and the rear hole injection protection layer both adopt AlGaN materials, and the Al component proportion of the AlGaN materials in the front hole injection protection layer and the rear hole injection protection layer is less than the Al component proportion of the second AlGaN insertion layer; the hole injection regulation layer adopts AlGaInN material and is doped with Mg elements. The Al component ratio of the first AlGaN insertion layer is 0.03-0.30, the growth thickness is 0.6-3.0 nm, the growth temperature is 818-935 DEG C, and the pressure is 50-360 torr; The Al component ratio of the second AlGaN insertion layer is 0.02-0.21, the growth thickness is 0.5-2.7 nm, the growth temperature is 818-935 DEG C, and the pressure is 50-360 torr; The Al component ratio of the third AlGaN insertion layer is 0.01-0.15, the growth thickness is 0.3-2.2 nm, the growth temperature is 818-935 DEG C, and the pressure is 50-360 torr; The first Si-doped GaN interlayer, the second Si-doped GaN interlayer and the third Si-doped GaN interlayer are all doped with Si elements, and the Si doping concentrations are 2.58*10 17 / cm 3 , 9.73*10 17 / cm 3 , respectively, the growth thicknesses are 0.3nm-3nm, respectively, the growth temperatures are 818℃-935℃, respectively, and the pressures are 50torr-360torr, respectively. The Al component ratio of the first AlGaN insertion layer is 0.03-0.30, the growth thickness is 0.6-3.0 nm, the growth temperature is 818-935 DEG C, and the pressure is 50-360 torr; The hole injection regulation layer is AlInGaN material doped with Mg element, the Al component ratio is 0.01-0.15, the In component ratio is 0.02-0.15, the thickness is 0.6-8.5nm, the Mg doping concentration is 3.15x10 18 / cm 3 -8.69x10 19 / cm 3 , the growth temperature is 818-935℃, and the pressure is 50-360torr.

2. The multi-band LED epitaxial structure of claim 1, wherein, The well layer of the first long-wave blue light multi-quantum well light-emitting layer is a first InGaN well layer, the well layer of the second middle-wave blue light multi-quantum well light-emitting layer is a second InGaN well layer, the well layer of the third short-wave blue light multi-quantum well light-emitting layer is a third InGaN well layer, and the well layer of the fourth short-wave blue light multi-quantum well light-emitting layer is a fourth InGaN well layer; The In component ratio of the first InGaN well layer > the In component ratio of the second InGaN well layer > the In component ratio of the third InGaN well layer = the In component ratio of the fourth InGaN well layer.

3. The multi-band LED epitaxial structure of claim 1, wherein, The light-emitting wavelength of the first long-wave blue light multi-quantum well light-emitting layer is 460-480 nm; The light-emitting wavelength of the second middle-wave blue light multi-quantum well light-emitting layer is 445-460 nm; The light-emitting wavelength of the third short-wave blue light multi-quantum well light-emitting layer is 430-445 nm; The light-emitting wavelength of the fourth short-wave blue light multi-quantum well light-emitting layer is 430-445 nm.

4. The multi-band LED epitaxial structure of claim 2, wherein, The In component ratio of the first InGaN well layer is 0.16-0.19, the growth thickness is 2.03-4.87 nm, the growth temperature is 750-930 DEG C, and the pressure is 50-360 torr; The In component ratio of the second InGaN well layer is 0.13-0.16, the growth thickness is 2.03-4.87 nm, the growth temperature is 770-930 DEG C, and the pressure is 50-360 torr; The In component ratio of the third InGaN well layer is 0.10-0.13, the growth thickness is 2.03-4.87 nm, the growth temperature is 790-930 DEG C, and the pressure is 50-360 torr; The In content of the fourth InGaN well layer is 0.10-0.13, the growth thickness is 2.03 nm-4.87 nm, the growth temperature is 790 DEG C-930 DEG C, and the pressure is 50 torr-360 torr.

5. The multiband LED epitaxial structure of claim 1, wherein, The barrier layer of the first long-wave blue light multi-quantum well light-emitting layer is a first barrier layer, the first barrier layer further comprises a plurality of first GaN layers, and the first N-type carrier regulation insertion layer is arranged between the plurality of first GaN layers; the first GaN layer is doped with Si elements, the Si doping concentration is 1.9*10 17 / cm 3 ~8.5*10 17 / cm 3 , the growth thickness is 5.6nm~13.8nm, the growth temperature is 818℃~935℃, and the pressure is 50torr~360torr; The barrier layer of the second middle-wave blue light multi-quantum well light-emitting layer is a second barrier layer, and the second barrier layer further comprises a plurality of second GaN layers, and a second N-type carrier regulation insertion layer is arranged between the plurality of second GaN layers; the second GaN layer is doped with Si elements, the Si doping concentration is 1.5*10 17 / cm 3 ~7.3*10 17 / cm 3 , the growth thickness is 5.6nm~13.8nm, the growth temperature is 818℃~935℃, and the pressure is 50torr~360torr; The barrier layer of the third short-wave blue light multi-quantum well light-emitting layer is a third barrier layer, and the third barrier layer further comprises a plurality of third GaN layers, and a third N-type carrier regulation insertion layer is arranged between the plurality of third GaN layers; the third GaN layer is doped with Si elements, the Si doping concentration is 1.2*10 17 / cm 3 ~6.1*10 17 / cm 3 , the growth thickness is 5.6nm~13.8nm, the growth temperature is 818℃~935℃, and the pressure is 50torr~360torr; The barrier layer of the fourth short-wave blue light sub-quantum well light-emitting layer is a fourth barrier layer, the fourth barrier layer further comprises a plurality of fourth GaN layers, a P-type carrier regulation insertion layer is arranged between the plurality of fourth GaN layers, the growth thickness of the fourth GaN layer is 5.6 nm-13.8 nm, the growth temperature is 818 DEG C-935 DEG C, and the pressure is 50 torr-360 torr.

6. A method for fabricating a multi-band LED epitaxial structure, characterized in that, A multi-band LED epitaxial structure according to any one of claims 1-5 is prepared, comprising: selecting a substrate; depositing 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 on the substrate in sequence; the multi-quantum well light-emitting layer comprises a first long-wave blue light multi-quantum well light-emitting layer, a second middle-wave blue light multi-quantum well light-emitting layer, a third short-wave blue light multi-quantum well light-emitting layer and a fourth short-wave blue light sub-quantum well light-emitting layer which are stacked in the epitaxial direction in sequence; the light-emitting wavelength of the first long-wave blue light multi-quantum well light-emitting layer > the light-emitting wavelength of the second middle-wave blue light multi-quantum well light-emitting layer > the light-emitting wavelength of the third short-wave blue light multi-quantum well light-emitting layer = the light-emitting wavelength of the fourth short-wave blue light sub-quantum well light-emitting layer; the first long-wave blue light multi-quantum well light-emitting layer, the second middle-wave blue light multi-quantum well light-emitting layer, the third short-wave blue light multi-quantum well light-emitting layer and the fourth short-wave blue light sub-quantum well light-emitting layer all are periodic structures formed by alternately stacking well layers and barrier layers; the band gap of the barrier layer in the first long-wave blue light multi-quantum well light-emitting layer > the band gap of the barrier layer in the second middle-wave blue light multi-quantum well light-emitting layer > the band gap of the barrier layer in the third short-wave blue light multi-quantum well light-emitting layer ≥ the band gap of the barrier layer in the fourth short-wave blue light sub-quantum well light-emitting layer; a P-type carrier regulation insertion layer is arranged in the barrier layer of the fourth short-wave blue light sub-quantum well light-emitting layer, and the P-type carrier regulation insertion layer is doped with Mg elements.

7. The method of claim 6, wherein the method further comprises: the P-type carrier regulation insertion layer comprises a front hole injection protection layer, a hole injection regulation layer and a rear hole injection protection layer which are stacked in sequence; the front hole injection protection layer and the rear hole injection protection layer are both made of AlGaN material, and the hole injection regulation layer is made of AlGaInN material and doped with Mg elements; after the deposition of the well layer of the fourth short-wave blue light sub-quantum well light-emitting layer and the hole injection regulation layer is completed, surface roughening annealing treatment is required, the temperature of the surface roughening annealing treatment is 830 DEG C-1080 DEG C, and the pressure is 30 torr-500 torr.

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