Multiband LED epitaxial wafer and method of manufacturing the same

Abstract

The application discloses a multi-waveband LED epitaxial wafer and a preparation method thereof, and relates to the technical field of semiconductors. The multi-waveband LED epitaxial wafer has a multi-quantum well light-emitting layer which is a periodic structure of alternately stacked layers, and each period comprises a pre-well protection layer, a first blue light quantum well layer, a cyan light quantum well layer, a second blue light quantum well layer, a post-well protection layer and a quantum barrier layer which are sequentially stacked; the pre-well protection layer, the first blue light quantum well layer, the cyan light quantum well layer, the second blue light quantum well layer and the post-well protection layer are all InGaN layers; in each period, the In component proportion of the cyan light quantum well layer is greater than the In component proportion of the first blue light quantum well layer and greater than the In component proportion of the second blue light quantum well layer; and the first blue light quantum well layer, the cyan light quantum well layer and the second blue light quantum well layer are all subjected to N2 treatment after being grown. According to the application, a healthy full-spectrum white light LED light source with a high color rendering index can be obtained.

Description

Technical Field

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

[0002] Existing white LED devices typically use blue LED chips to excite a mixture of red and green phosphors to emit white light. However, in the spectral curves of existing full-spectrum white LED light sources, the blue light band exhibits significant fluctuations and poor stability. Furthermore, short-wavelength blue light between 400nm and 450nm poses the greatest threat to the retina. This short-wavelength blue light can penetrate the lens and reach the retina, generating free radicals. These free radicals can cause the death of retinal pigment epithelial cells, leading to a lack of nutrients for photosensitive cells and resulting in irreversible vision damage. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a multi-band LED epitaxial wafer and its preparation method, which generates a full-spectrum white LED light source by exciting red and green mixed phosphors through a multi-band LED chip, thereby realizing a healthy full-spectrum white LED light source with a high color rendering index.

[0004] To address the aforementioned issues, this invention discloses a multi-band LED epitaxial wafer, 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 sequentially stacked on the substrate.

[0005] The multi-quantum-well light-emitting layer is a periodic structure with alternating layers. Each period includes a front-well protective layer, a first blue quantum well layer, a cyan quantum well layer, a second blue quantum well layer, a back-well protective layer, and a quantum barrier layer stacked sequentially.

[0006] The pre-well protective layer, the first blue quantum well layer, the cyan quantum well layer, the second blue quantum well layer, and the post-well protective layer are all InGaN layers;

[0007] In each cycle, the proportion of In component in the cyan quantum well layer is greater than the proportion of In component in the first blue quantum well layer, and also greater than the proportion of In component in the second blue quantum well layer;

[0008] After the first blue quantum well layer, the cyan quantum well layer, and the second blue quantum well layer are grown, they are all subjected to N2 treatment.

[0009] As an improvement to the above technical solution, the conditions for N2 treatment include: intermittent, cyclic N2 introduction, treatment temperature of 700℃~880℃, treatment pressure of 30 torr~390 torr, and treatment time ≥10s.

[0010] As an improvement to the above technical solution, the cycle period for introducing N2 is 5s to 60s, the time for introducing N2 accounts for 20% to 80%, and the number of cycles is 2 to 15.

[0011] As an improvement to the above technical solution, in each cycle, the proportion of In component in the pre-well protective layer increases with the stacking direction, while the proportion of In component in the post-well protective layer decreases with the stacking direction; and / or,

[0012] In each cycle, the proportion of In component in the first blue quantum well layer is not equal to the proportion of In component in the second blue quantum well layer.

[0013] As an improvement to the above technical solution, the number of alternating stacks of the multi-quantum-well light-emitting layers is 3 to 18;

[0014] The in-well protective layer has an In composition ratio of 0~0.18 and a thickness of 0.1nm~1.2nm. The in-well protective layer is a Si-doped in-well protective layer with a Si doping concentration of 1.18×10⁻⁶. 17 cm -3 ~7.56×10 17 cm -3 ;

[0015] The first blue quantum well layer has an In composition ratio of 0.09~0.18 and a thickness of 0.2nm~2nm;

[0016] The In composition of the cyan quantum well layer is 0.18~0.22, and the thickness is 0.2nm~2nm;

[0017] The second blue quantum well layer has an In composition ratio of 0.09~0.18 and a thickness of 0.2nm~2nm;

[0018] The in content of the back-well protective layer is 0~0.18, and the thickness is 0.1nm~1.2nm. The back-well protective layer is a Si-doped back-well protective layer with a Si doping concentration of 1.18×10⁻⁶. 17 cm -3 ~7.56×10 17 cm -3 .

[0019] As an improvement to the above technical solution, the quantum barrier layer is a Si-doped AlGaN layer with an Al composition ratio of 0~0.5%, a thickness of 5nm~15nm, and a Si doping concentration of 1.67×10⁻⁶. 17 cm -3 ~8.79×10 17 cm -3 .

[0020] Accordingly, the present invention also discloses a method for preparing a multi-band LED epitaxial wafer, which includes the following steps:

[0021] A substrate is provided on which 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 grown.

[0022] The multi-quantum-well light-emitting layer is a periodic structure with alternating layers. Each period includes a front-well protective layer, a first blue quantum well layer, a cyan quantum well layer, a second blue quantum well layer, a back-well protective layer, and a quantum barrier layer stacked sequentially.

[0023] The pre-well protective layer, the first blue quantum well layer, the cyan quantum well layer, the second blue quantum well layer, and the post-well protective layer are all InGaN layers;

[0024] In each cycle, the proportion of In component in the cyan quantum well layer is greater than the proportion of In component in the first blue quantum well layer, and also greater than the proportion of In component in the second blue quantum well layer;

[0025] After the first blue quantum well layer, the cyan quantum well layer, and the second blue quantum well layer are grown, they are all subjected to N2 treatment.

[0026] As an improvement to the above technical solution, the growth temperature of the pre-well protective layer is 730℃~925℃, and the growth pressure is 30 torr~390 torr;

[0027] The growth temperature of the first blue quantum well layer is 730℃~880℃, and the growth pressure is 30 torr~390 torr;

[0028] The growth temperature of the cyan quantum well layer is 700℃~850℃, and the growth pressure is 30 torr~390 torr.

[0029] The growth temperature of the second blue quantum well layer is 730℃~880℃, and the growth pressure is 30 torr~390 torr;

[0030] The growth temperature of the post-well protective layer is 730℃~925℃, and the growth pressure is 30 torr~390 torr;

[0031] The growth temperature of the quantum barrier layer is 750℃~980℃, and the growth pressure is 30 torr~390 torr.

[0032] As an improvement to the above technical solution, after the first blue quantum well layer, the cyan quantum well layer and the second blue quantum well layer are grown, N2 is intermittently and cyclically introduced for N2 treatment. The treatment temperature is 700℃~880℃, the treatment pressure is 30 torr~390 torr, and the treatment time is ≥10s.

[0033] As an improvement to the above technical solution, the cycle period for introducing N2 is 5s to 60s, the time for introducing N2 accounts for 20% to 80%, and the number of cycles is 2 to 15.

[0034] Implementing this invention has the following beneficial effects:

[0035] 1. The multi-band LED epitaxial wafer provided by this invention excites red and green mixed phosphors to generate a full-spectrum white LED light source by using a cyan excitation source and two blue excitation sources. Compared with a blue excitation source with only one wavelength, it has a smaller proportion of short-wavelength blue light below 450nm, which causes less damage to human retinal cells. Moreover, its excitation source has three wavelengths, and 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.

[0036] 2. The multi-band LED epitaxial wafer provided by the present invention has a first blue quantum well layer with low In content, a cyan quantum well layer with high In content, and a second blue quantum well layer with low In content. The In content of the InGaN material increases first and then decreases, which can effectively reduce the lattice mismatch stress between the quantum well InGaN material and the quantum barrier layer material, which is beneficial to improving the radiative recombination efficiency of the multi-quantum well light-emitting layer, thereby improving the luminous efficacy and yield of the multi-band LED chip.

[0037] 3. In the process of growing the first blue quantum well layer, the cyan quantum well layer and the second blue quantum well layer, the present invention adopts an intermittent well layer growth process. That is, after the growth of the first blue quantum well layer, the cyan quantum well layer and the second blue quantum well layer are completed, N2 is intermittently and cyclically introduced into the reaction chamber to provide sufficient time for surface atomic migration and form a step flow mode. This can reduce the interface roughness of the InGaN material in the quantum well layer, making the interface of the InGaN material in the quantum well layer smoother. At the same time, it can reduce the defect density of the InGaN material in the quantum well layer, thereby improving the luminous uniformity and luminous efficiency of the multi-band LED chip. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of the multi-band LED epitaxial wafer provided in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of the multi-quantum well light-emitting layer of the multi-band LED epitaxial wafer provided in an embodiment of the present invention;

[0040] Figure 3 This is a flowchart of the method for preparing a multi-band LED epitaxial wafer according to an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0042] like Figure 1 and Figure 2 As shown, the present invention provides a multi-band LED epitaxial wafer, including a substrate 100, and a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress relief layer 400, a multi-quantum well light-emitting layer 500, an electron blocking layer 600 and a P-type semiconductor layer 700 sequentially stacked on the substrate 100.

[0043] The multi-quantum-well light-emitting layer 500 is a periodically stacked structure, with each period comprising a pre-well protective layer 510, a first blue quantum well layer 520, a cyan quantum well layer 530, a second blue quantum well layer 540, a post-well protective layer 550, and a quantum barrier layer 560 stacked sequentially. The multi-band LED epitaxial wafer provided by this invention excites red and green mixed phosphors to generate a full-spectrum white LED light source through a cyan excitation source and two blue excitation sources. Compared to a blue excitation source with only one wavelength, it has a smaller proportion of short-wavelength blue light below 450nm, resulting in less damage to human retinal cells. Furthermore, its excitation source has three wavelengths, producing full-spectrum white light that is closer to the solar spectrum, thus achieving a healthy full-spectrum white LED light source with a high color rendering index.

[0044] Specifically, the pre-well protective layer 510, the first blue quantum well layer 520, the cyan quantum well layer 530, the second blue quantum well layer 540, and the post-well protective layer 550 are all InGaN layers. In each cycle, the In composition ratio of the cyan quantum well layer 530 is greater than that of the first blue quantum well layer 520 and greater than that of the second blue quantum well layer 540. The multi-band LED epitaxial wafer provided by this invention has a first blue quantum well layer 520 with low In content, a cyan quantum well layer 530 with high In content, and a second blue quantum well layer 540 with low In content. The In content of the InGaN material is first increased and then decreased, which can effectively reduce the lattice mismatch stress between the InGaN material in the quantum well layer and the quantum barrier layer 560. The reduction of defects caused by the lattice mismatch stress can significantly improve the quality of the multi-quantum well light-emitting layer 500, which is beneficial to improving the radiative recombination efficiency of the active region, thereby improving the luminous efficacy and yield of the multi-band LED chip. At the same time, the reduction of the lattice mismatch stress between the InGaN material in the quantum well layer and the quantum barrier layer 560 can also reduce the band bending phenomenon caused by the piezoelectric polarization effect in the InGaN material in the quantum well layer, thereby improving the coupling degree between the electron and hole wave functions in the InGaN material in the quantum well layer, improving the radiative recombination efficiency in the multi-quantum well light-emitting layer 500, and ultimately improving the luminous efficacy of the multi-band LED chip.

[0045] After the first blue quantum well layer 520, the cyan quantum well layer 530 and the second blue quantum well layer 540 are grown, they are all subjected to N2 treatment.

[0046] In one embodiment, the N2 treatment conditions include: intermittent, cyclic N2 introduction, a treatment temperature of 700℃~880℃, a treatment pressure of 30 torr~390 torr, and a treatment time ≥10s. In the growth of the first blue quantum well layer 520, the cyan quantum well layer 530, and the second blue quantum well layer 540 of the InGaN material, this invention employs an intermittent well layer growth process. Specifically, after the growth of the first blue quantum well layer 520, the cyan quantum well layer 530, and the second blue quantum well layer 540, N2 is intermittently and cyclically introduced into the reaction chamber. This provides sufficient time for surface atomic migration, forming a stepped flow mode, which reduces the interface roughness of the InGaN quantum well layer material, making the interface of the InGaN quantum well layer material smoother. Simultaneously, it reduces the defect density of the InGaN quantum well layer material, thereby improving the luminous uniformity and luminous efficiency of the multi-band LED chip.

[0047] In a preferred embodiment, the N2 introduction cycle is 5s to 60s, the N2 introduction time accounts for 20% to 80% of the total time, and the number of cycles is 2 to 15. The intermittent well layer growth process, combined with the sequentially stacked structure of the pre-well protective layer 510, the first blue quantum well layer 520, the cyan quantum well layer 530, the second blue quantum well layer 540, and the post-well protective layer 550, can improve the growth quality while adjusting the emission wavelength.

[0048] In one embodiment, in each cycle, the In composition percentage of the pre-well protective layer 510 increases with the stacking direction, while the In composition percentage of the post-well protective layer 550 decreases with the stacking direction. This increasing In composition percentage of the pre-well protective layer 510 and decreasing In composition percentage of the post-well protective layer 550 can further reduce the lattice mismatch stress between the InGaN quantum well layer and the quantum barrier layer 560.

[0049] In one embodiment, the In composition percentage of the first blue quantum well layer 520 is not equal to that of the second blue quantum well layer 540 in each cycle. It is understood that the In composition percentage of the first blue quantum well layer 520 can be greater than or less than that of the second blue quantum well layer 540, so that the excitation light source of the multi-band LED epitaxial wafer provided in this embodiment of the invention has three bands, and the generated full-spectrum white light is closer to the solar spectrum, thereby improving the color rendering index of the white LED light source.

[0050] In one embodiment, the number of alternating stacked cycles of the multi-quantum well light-emitting layers 500 is 3 to 18, exemplarily 5, 8, 10, 12, 14 or 16, but not limited thereto.

[0051] The In composition ratio of the pre-well protective layer 510 is 0~0.18, exemplarily 0.01, 0.05, 0.1, 0.12, 0.14, or 0.16, but not limited thereto; the thickness is 0.1nm~1.2nm, exemplarily 0.2nm, 0.4nm, 0.5nm, 0.6nm, 0.8nm, or 1nm, but not limited thereto. The pre-well protective layer 510 is a Si-doped pre-well protective layer with a Si doping concentration of 1.18 × 10⁻⁶. 17 cm -3 ~7.56×10 17 cm -3 An example is 2×10 17 cm -3 3×10 17 cm -3 4×10 17 cm -3 5×10 17 cm -36×10 17 cm -3 Or 7×10 17 cm -3 However, it is not limited to this.

[0052] The first blue quantum well layer 520 has an In content of 0.09 to 0.18, exemplarily 0.1, 0.12, 0.14, 0.15, 0.16, or 0.17, but is not limited thereto. Its thickness is 0.2 nm to 2 nm, exemplarily 0.5 nm, 0.8 nm, 1 nm, 1.2 nm, 1.4 nm, or 1.8 nm, but is not limited thereto. The first blue quantum well layer 520 uses InGaN material with a constant In content. The InGaN material is not intentionally doped, and the wavelength of radiative recombination emission of the InGaN material is in the blue light band.

[0053] The In composition of the cyan quantum well layer 530 is 0.18~0.22, exemplarily 0.182, 0.185, 0.19, 0.195, 0.2, or 0.21, but not limited thereto; the thickness is 0.2nm~2nm, exemplarily 0.5nm, 0.8nm, 1nm, 1.2nm, 1.4nm, or 1.8nm, but not limited thereto. The cyan quantum well layer 530 uses InGaN material with a constant In composition, the InGaN material is not intentionally doped, and the wavelength of radiative recombination emission of the InGaN material is in the cyan band.

[0054] The second blue quantum well layer 540 has an In composition ratio of 0.09~0.18, exemplarily 0.1, 0.12, 0.14, 0.15, 0.16 or 0.17, but is not limited thereto; and a thickness of 0.2nm~2nm, exemplarily 0.5nm, 0.8nm, 1nm, 1.2nm, 1.4nm or 1.8nm, but is not limited thereto. The second blue quantum well layer 540 uses InGaN material with a constant In composition, the InGaN material is not intentionally doped, and the wavelength of radiative recombination emission of the InGaN material is in the blue light band.

[0055] The in content of the back-well protective layer 550 is 0~0.18, exemplarily 0.01, 0.05, 0.1, 0.12, 0.14, or 0.16, but not limited thereto; the thickness is 0.1nm~1.2nm, exemplarily 0.2nm, 0.4nm, 0.5nm, 0.6nm, 0.8nm, or 1nm, but not limited thereto. The back-well protective layer 550 is a Si-doped back-well protective layer with a Si doping concentration of 1.18 × 10⁻⁶. 17 cm -3 ~7.56×10 17 cm -3An example is 2×10 17 cm -3 3×10 17 cm -3 4×10 17 cm -3 5×10 17 cm -3 6×10 17 cm -3 Or 7×10 17 cm -3 However, it is not limited to this.

[0056] Optionally, the quantum barrier layer 560 is a Si-doped AlGaN layer with an Al content of 0-0.5%. That is, the quantum barrier layer 560 can be a single-layer or multi-layer structure. The material of the quantum barrier layer 560 can be GaN and / or AlGaN, with a thickness of 5 nm-15 nm and a Si doping concentration of 1.67 × 10⁻⁶. 17 cm -3 ~8.79×10 17 cm -3 .

[0057] Besides the multi-quantum-well light-emitting layer 500, the other features of the layered structure of the present invention are as follows:

[0058] The substrate 100 can be one of a sapphire substrate, a SiO2 sapphire composite substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, or a zinc oxide substrate. In one embodiment, the substrate 100 is selected as a sapphire substrate.

[0059] The buffer layer 200 can be an AlN buffer layer and / or an AlGaN buffer layer. In one embodiment, the buffer layer 200 is an AlN buffer layer with a thickness of 20 nm to 200 nm.

[0060] The N-type semiconductor layer 300 includes an undoped GaN layer and an N-type GaN layer. The thickness of the undoped GaN layer is 1 μm to 5 μm, and the thickness of the N-type GaN layer is 2 μm to 3 μm. The Si doping concentration is 1 × 10⁻⁶. 19 cm -3 ~5×10 19 cm -3 .

[0061] The low-temperature stress relief layer 400 may include periodically alternating layers of InGaN and GaN stress relief layers, with 2 to 10 alternating growth cycles. The InGaN stress relief layer has a thickness of 1 nm to 3 nm, and the GaN stress relief layer has a thickness of 15 nm to 30 nm. The growth temperature of the low-temperature stress relief layer 400 is 800℃ to 900℃.

[0062] The electron blocking layer 600 can be an AlGaN electron blocking layer with a thickness of 10nm~100nm and an Al composition ratio of 0.4~0.8%.

[0063] The P-type semiconductor layer 700 can be a P-type GaN layer with a thickness of 10nm~50nm and a Mg doping concentration of 1×10⁻⁶. 19 cm -3 ~5×10 20 cm -3 .

[0064] Correspondingly, such as Figure 3 As shown, the present invention also discloses a method for preparing a multi-band LED epitaxial wafer, which includes the following steps:

[0065] S1. Provide a substrate 100.

[0066] In one embodiment, the substrate 100 is selected as a sapphire substrate.

[0067] S2. A buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress relief layer 400, a multi-quantum well light-emitting layer 500, an electron blocking layer 600, and a P-type semiconductor layer 700 are sequentially grown on the substrate 100.

[0068] It is understandable that layered structures can be grown by MOCVD, MBE, PVD, or VPE, but are not limited to these methods.

[0069] In one embodiment, the fabrication of the multi-quantum-well light-emitting layer 500 includes: growing a pre-well protective layer 510, a first blue quantum well layer 520, a cyan quantum well layer 530, a second blue quantum well layer 540, and a post-well protective layer 550 using MOCVD; growing a quantum barrier layer 560 using MOCVD; and repeatedly stacking and periodically growing the pre-well protective layer 510, the first blue quantum well layer 520, the cyan quantum well layer 530, the second blue quantum well layer 540, the post-well protective layer 550, and the quantum barrier layer 560.

[0070] Specifically, it includes the following steps:

[0071] S21, protective layer 510 in front of growth trap.

[0072] A protective layer 510 is used in front of the MOCVD growth trap. The temperature of the reaction chamber is controlled at 730℃~925℃ and the pressure is controlled at 30 torr~390 torr. In source, N source, Ga source and Si source are introduced.

[0073] S22, grow the first blue quantum well layer 520.

[0074] The first blue quantum well layer 520 was grown using MOCVD, with the temperature of the reaction chamber controlled at 730℃~880℃ and the pressure at 30 torr~390 torr, and In source, N source and Ga source were introduced.

[0075] In a preferred embodiment, after the first blue quantum well layer 520 is grown, N2 is intermittently and cyclically introduced for N2 treatment. The treatment temperature is 700℃~880℃, the treatment pressure is 30 torr~390 torr, and the treatment time is ≥10s.

[0076] Even better, the N2 purging cycle is 5s~60s, the N2 purging time accounts for 20%~80% of the total time, and the number of cycles is 2~15.

[0077] S23, grow a cyan quantum well layer 530.

[0078] The cyan quantum well layer 530 was grown by MOCVD, and the temperature of the reaction chamber was controlled at 700℃~850℃ and the pressure at 30 torr~390 torr. In source, N source and Ga source were introduced.

[0079] In a preferred embodiment, after the cyan quantum well layer 530 is grown, N2 is intermittently and cyclically introduced for N2 treatment. The treatment temperature is 700℃~880℃, the treatment pressure is 30 torr~390 torr, and the treatment time is ≥10s.

[0080] Even better, the N2 purging cycle is 5s~60s, the N2 purging time accounts for 20%~80% of the total time, and the number of cycles is 2~15.

[0081] S24, grow the second blue quantum well layer 540.

[0082] The second blue quantum well layer 540 was grown using MOCVD. The temperature of the reaction chamber was controlled at 730℃~880℃ and the pressure at 30 torr~390 torr. In source, N source and Ga source were introduced.

[0083] In a preferred embodiment, after the second blue quantum well layer 540 is grown, N2 is intermittently and cyclically introduced for N2 treatment. The treatment temperature is 700℃~880℃, the treatment pressure is 30 torr~390 torr, and the treatment time is ≥10s.

[0084] Even better, the N2 purging cycle is 5s~60s, the N2 purging time accounts for 20%~80% of the total time, and the number of cycles is 2~15.

[0085] S25, protective layer 550 behind growth trap.

[0086] A 550 protective layer was used after the MOCVD growth trap. The temperature of the reaction chamber was controlled at 730℃~925℃ and the pressure at 30 torr~390 torr. In source, N source, Ga source and Si source were introduced.

[0087] S26, grow quantum barrier layer 560.

[0088] The quantum barrier layer 560 was grown using MOCVD, with the temperature of the reaction chamber controlled at 750℃~980℃ and the pressure at 30 torr~390 torr, and Al source, N source, Ga source and Si source were introduced.

[0089] S27, a pre-well protective layer 510, a first blue quantum well layer 520, a cyan quantum well layer 530, a second blue quantum well layer 540, a post-well protective layer 550, and a quantum barrier layer 560 are repeatedly stacked and periodically grown.

[0090] The present invention will be further described below with reference to specific embodiments:

[0091] Example 1

[0092] This embodiment provides a multi-band LED epitaxial wafer, including 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 sequentially stacked on the substrate.

[0093] The multi-quantum-well light-emitting layer is a periodic structure with alternating layers. Each period includes a front-well protective layer, a first blue quantum well layer, a cyan quantum well layer, a second blue quantum well layer, a back-well protective layer, and a quantum barrier layer stacked sequentially. The number of alternating stacked periods is 10.

[0094] The in-well protective layer has an In composition of 0.05% and a thickness of 1 nm. It is a Si-doped in-well protective layer with a Si doping concentration of 5 × 10⁻⁶. 17 cm -3 .

[0095] The first blue quantum well layer has an In composition ratio of 0.12 and a thickness of 1 nm.

[0096] The In composition of the cyan quantum well layer is 0.21, and the thickness is 1 nm.

[0097] The second blue quantum well layer has an In composition ratio of 0.16 and a thickness of 1 nm.

[0098] The in content of the back-well protective layer is 0.05%, and the thickness is 1 nm. The back-well protective layer is Si-doped with a Si doping concentration of 5 × 10⁻⁶. 17 cm -3 .

[0099] The quantum barrier layer is a Si-doped AlGaN layer with an Al content of 0.2% and a Si doping concentration of 5 × 10⁻⁶. 17 cm -3 The thickness is 10nm.

[0100] After the first blue quantum well layer, the cyan quantum well layer, and the second blue quantum well layer were grown, N2 was intermittently and cyclically introduced. The processing temperature was 800℃, the processing pressure was 120 torr, the processing time was 10s, the N2 introduction cycle was 5s, the N2 introduction time accounted for 80% of the total time, and the number of cycles was 2.

[0101] Example 2

[0102] This embodiment provides a multi-band LED epitaxial wafer, which differs from Embodiment 1 in that, after the first blue quantum well layer, the cyan quantum well layer, and the second blue quantum well layer are grown, N2 is intermittently and cyclically introduced. The processing temperature is 800℃, the processing pressure is 120 torr, the processing time is 900s, the N2 introduction cycle is 60s, the N2 introduction time accounts for 20% of the total time, and the number of cycles is 15.

[0103] Everything else is the same as in Example 1.

[0104] Example 3

[0105] This embodiment provides a multi-band LED epitaxial wafer, which differs from Embodiment 1 in that, after the first blue quantum well layer, the cyan quantum well layer, and the second blue quantum well layer are grown, N2 is intermittently and cyclically introduced. The processing temperature is 800℃, the processing pressure is 120 torr, the processing time is 200s, the N2 introduction cycle is 20s, the N2 introduction time accounts for 60% of the total time, and the number of cycles is 10.

[0106] Everything else is the same as in Example 1.

[0107] Example 4

[0108] This embodiment provides a multi-band LED epitaxial wafer, which differs from Embodiment 1 in that, in each cycle, the proportion of In component in the pre-well protective layer increases from 0.01 to 0.08 with the stacking direction.

[0109] Everything else is the same as in Example 1.

[0110] Example 5

[0111] This embodiment provides a multi-band LED epitaxial wafer, which differs from Embodiment 4 in that, in each cycle, the proportion of In component in the back-well protective layer decreases from 0.08 to 0.01 with the stacking direction.

[0112] Everything else is the same as in Example 4.

[0113] Comparative Example 1

[0114] This comparative example provides an LED epitaxial wafer, which differs from Example 1 in that each period of the multi-quantum-well light-emitting layer includes an InGaN quantum well layer and an AlGaN quantum barrier layer. The InGaN quantum well layer has an In composition ratio of 0.2% and a thickness of 5 nm. The AlGaN quantum barrier layer is a Si-doped AlGaN layer with an Al composition ratio of 0.2% and a Si doping concentration of 5 × 10⁻⁶. 17 cm -3 The thickness is 10nm.

[0115] Everything else is the same as in Example 1.

[0116] The luminous efficiency and color rendering index of the LED epitaxial wafers prepared in Examples 1-5 and Comparative Example 1 were tested, and the improvement rate of luminous efficiency of Examples 1-5 compared with Comparative Example 1 was calculated. The specific results are as follows:

[0117]

[0118] The above description is a preferred embodiment of the invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A multi-band LED epitaxial wafer, characterized in that, It includes 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 sequentially stacked on the substrate; The multi-quantum-well light-emitting layer is a periodic structure with alternating layers. Each period includes a front-well protective layer, a first blue quantum well layer, a cyan quantum well layer, a second blue quantum well layer, a back-well protective layer, and a quantum barrier layer stacked sequentially. The pre-well protective layer, the first blue quantum well layer, the cyan quantum well layer, the second blue quantum well layer, and the post-well protective layer are all InGaN layers; In each cycle, the proportion of In component in the cyan quantum well layer is greater than the proportion of In component in the first blue quantum well layer, and also greater than the proportion of In component in the second blue quantum well layer; After the first blue quantum well layer, the cyan quantum well layer, and the second blue quantum well layer are grown, they are all treated with N2. The conditions for N2 treatment include: intermittent, cyclic N2 introduction, treatment temperature of 700℃~880℃, treatment pressure of 30 torr~390 torr, and treatment time ≥10s; In each cycle, the proportion of In component in the pre-well protective layer increases with the stacking direction, while the proportion of In component in the post-well protective layer decreases with the stacking direction.

2. The multi-band LED epitaxial wafer as described in claim 1, characterized in that, The cycle time for introducing N2 is 5s to 60s, the time spent introducing N2 is 20% to 80%, and the number of cycles is 2 to 15.

3. The multi-band LED epitaxial wafer as described in claim 1, characterized in that, In each cycle, the proportion of In component in the first blue quantum well layer is not equal to the proportion of In component in the second blue quantum well layer.

4. The multi-band LED epitaxial wafer as described in claim 1, characterized in that, The number of alternating stacks of the multi-quantum-well light-emitting layers is 3 to 18; The in-well protective layer has an In composition ratio of 0~0.18 and a thickness of 0.1nm~1.2nm. The in-well protective layer is a Si-doped in-well protective layer with a Si doping concentration of 1.18×10⁻⁶. 17 cm -3 ~7.56×10 17 cm -3 ; The first blue quantum well layer has an In composition ratio of 0.09~0.18 and a thickness of 0.2nm~2nm; The In composition of the cyan quantum well layer is 0.18~0.22, and the thickness is 0.2nm~2nm; The second blue quantum well layer has an In composition ratio of 0.09~0.18 and a thickness of 0.2nm~2nm; The in content of the back-well protective layer is 0~0.18, and the thickness is 0.1nm~1.2nm. The back-well protective layer is a Si-doped back-well protective layer with a Si doping concentration of 1.18×10⁻⁶. 17 cm -3 ~7.56×10 17 cm -3 .

5. The multi-band LED epitaxial wafer as described in claim 1, characterized in that, The quantum barrier layer is a Si-doped AlGaN layer with an Al content of 0-0.5%, a thickness of 5 nm-15 nm, and a Si doping concentration of 1.67 × 10⁻⁶. 17 cm -3 ~8.79×10 17 cm -3 .

6. A method for fabricating a multi-band LED epitaxial wafer, used to fabricate the multi-band LED epitaxial wafer as described in any one of claims 1 to 5, characterized in that, Includes the following steps: A substrate is provided on which 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 grown. The multi-quantum-well light-emitting layer is a periodic structure with alternating layers. Each period includes a front-well protective layer, a first blue quantum well layer, a cyan quantum well layer, a second blue quantum well layer, a back-well protective layer, and a quantum barrier layer stacked sequentially. The pre-well protective layer, the first blue quantum well layer, the cyan quantum well layer, the second blue quantum well layer, and the post-well protective layer are all InGaN layers; In each cycle, the proportion of In component in the cyan quantum well layer is greater than the proportion of In component in the first blue quantum well layer, and also greater than the proportion of In component in the second blue quantum well layer; After the first blue quantum well layer, the cyan quantum well layer, and the second blue quantum well layer are grown, they are all subjected to N2 treatment.

7. The method for preparing a multi-band LED epitaxial wafer as described in claim 6, characterized in that, The growth temperature of the pre-well protective layer is 730℃~925℃, and the growth pressure is 30 torr~390 torr. The growth temperature of the first blue quantum well layer is 730℃~880℃, and the growth pressure is 30 torr~390 torr; The growth temperature of the cyan quantum well layer is 700℃~850℃, and the growth pressure is 30 torr~390 torr. The growth temperature of the second blue quantum well layer is 730℃~880℃, and the growth pressure is 30 torr~390 torr; The growth temperature of the post-well protective layer is 730℃~925℃, and the growth pressure is 30 torr~390 torr; The growth temperature of the quantum barrier layer is 750℃~980℃, and the growth pressure is 30 torr~390 torr.

8. The method for preparing a multi-band LED epitaxial wafer as described in claim 6, characterized in that, After the first blue quantum well layer, the cyan quantum well layer, and the second blue quantum well layer are grown, N2 is introduced intermittently and cyclically for N2 treatment. The treatment temperature is 700℃~880℃, the treatment pressure is 30 torr~390 torr, and the treatment time is ≥10s.

9. The method for preparing a multi-band LED epitaxial wafer as described in claim 8, characterized in that, The cycle time for introducing N2 is 5s to 60s, the time spent introducing N2 is 20% to 80%, and the number of cycles is 2 to 15.

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