Blue-green dual-band LED epitaxial wafer and preparation method thereof

Abstract

The application discloses a blue-green dual-band LED epitaxial wafer and a preparation method thereof, and relates to the technical field of semiconductors. The epitaxial wafer comprises a substrate, a buffer layer, a first N-type semiconductor layer, a green light multi-quantum well layer, a second N-type semiconductor layer, a low-temperature stress release layer, a blue light multi-quantum well layer, an electron blocking layer and a P-type semiconductor layer which are stacked on the substrate; the green light multi-quantum well layer comprises a green light InGaN quantum well layer and a green light GaN quantum barrier layer; the blue light multi-quantum well layer comprises a blue light InGaN quantum well layer and a blue light GaN quantum barrier layer; the band gap of the green light InGaN quantum well layer is smaller than that of the blue light InGaN quantum well layer; the Si doping concentration of the green light GaN quantum barrier layer is greater than or equal to that of the blue light GaN quantum barrier layer; and the growth temperature of the first N-type semiconductor layer is greater than that of the second N-type semiconductor layer. By adopting the application, the light emitting efficiency of the chip can be improved.

Description

Technical Field

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

[0002] Traditional blue-green dual-band LED chips generally adopt a dual-active-region electroluminescence mode, where both the blue quantum well and the green quantum well are active regions, emitting light simultaneously through current injection. This emission mode simply grows the blue MQW and the green MQW in the same epitaxial structure. Due to the high In content and high defect density in the green MQW, the luminous efficiency is low, and it is very easy to exhibit phenomena such as strong blue light intensity, weak green light intensity, or unstable color with changes in current.

[0003] To address the issues of low luminous efficiency and intensity mismatch between blue and green light in dual-band blue-green LED chips, existing research has improved the structure of the epitaxial wafer. This involves using a blue quantum well to generate blue light through radiative recombination, while the green quantum well converts blue light into green light through photoluminescence. This hybrid electroluminescence and photoluminescence mode improves both blue and green light intensity, resulting in a higher intensity match and improved luminous efficiency to some extent. However, current structural designs for epitaxial wafers using this hybrid electroluminescence and photoluminescence mode are still imperfect and struggle to effectively maximize luminous efficiency. Therefore, further optimization and improvement of the structure of dual-band blue-green LED epitaxial wafers are urgently needed to further enhance the luminous efficiency of these chips. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a blue-green dual-band LED epitaxial wafer that can improve the crystal quality of the epitaxial wafer and enhance the electron-hole matching degree, thereby improving the luminous efficiency of the blue-green dual-band LED chip.

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a blue-green dual-band LED epitaxial wafer, which is used to prepare the above-mentioned blue-green dual-band LED epitaxial wafer.

[0006] To solve the above-mentioned technical problems, the present invention provides a blue-green dual-band LED epitaxial wafer, comprising a substrate and a buffer layer, a first N-type semiconductor layer, a green light multi-quantum well layer, a second N-type semiconductor layer, a low-temperature stress relief layer, a blue light multi-quantum well layer, an electron blocking layer and a P-type semiconductor layer sequentially stacked on the substrate. The green light multi-quantum well layer includes a periodically alternating stacked green light InGaN quantum well layer and a green light GaN quantum barrier layer, and the blue light multi-quantum well layer includes a periodically alternating stacked blue light InGaN quantum well layer and a blue light GaN quantum barrier layer. The bandgap width of the green InGaN quantum well layer is less than the bandgap width of the blue InGaN quantum well layer; The green GaN quantum barrier layer and the blue GaN quantum barrier layer are respectively doped with Si element, and the doping concentration of Si element in the green GaN quantum barrier layer is greater than or equal to the doping concentration of Si element in the blue GaN quantum barrier layer. The growth temperature of the first N-type semiconductor layer is greater than the growth temperature of the second N-type semiconductor layer.

[0007] As an improvement to the above technical solution, the ratio of the Si doping concentration in the green GaN quantum barrier layer to the Si doping concentration in the blue GaN quantum barrier layer is 2 to 30.

[0008] As an improvement to the above technical solution, the difference between the growth temperature of the first N-type semiconductor layer and the growth temperature of the second N-type semiconductor layer is 100℃~350℃.

[0009] As an improvement to the above technical solution, both the first N-type semiconductor layer and the second N-type semiconductor layer are GaN materials doped with Si, and the Si doping concentration of the first N-type semiconductor layer is greater than or equal to the Si doping concentration of the second N-type semiconductor layer. The thickness of the first N-type semiconductor layer is greater than or equal to the thickness of the second N-type semiconductor layer.

[0010] As an improvement to the above technical solution, the proportion of In component in the green InGaN quantum well layer is 0.22~0.28, and the thickness is 2.1nm~4.8nm; The Si doping concentration in the green GaN quantum barrier layer is 3.6 × 10⁻⁶. 17 / cm 3 ~5.6×10 18 / cm 3 The thickness is 5nm~15nm; The blue InGaN quantum well layer has an In content of 0.05~0.19 and a thickness of 2.1nm~4.8nm. The Si doping concentration in the blue GaN quantum barrier layer is 1.8 × 10⁻⁶. 17 / cm 3 ~9.6×10 17 / cm 3 The thickness is 5nm~15nm.

[0011] As an improvement to the above technical solution, the thickness of the first N-type semiconductor layer is 0.8 μm to 8 μm, and the Si element doping concentration is 3.6 × 10⁻⁶. 18 / cm 3 ~5.8×10 20 / cm 3 The growth temperature is 950℃~1250℃; The thickness of the second N-type semiconductor layer is 0.8 μm to 8 μm, and the Si doping concentration is 3.6 × 10⁻⁶. 18 / cm 3 ~5.8×10 20 / cm 3 The growth temperature is 820℃~1150℃.

[0012] As an improvement to the above technical solution, the low-temperature stress relief layer is provided with a first V-shaped pit penetrating through the low-temperature stress relief layer; The blue light multi-quantum well layer has a second V-shaped pit formed in the corresponding region of the first V-shaped pit; The electron blocking layer has a third V-shaped pit formed in the corresponding area of ​​the second V-shaped pit; The third V-shaped pit is filled by the P-type semiconductor layer.

[0013] As an improvement to the above technical solution, the distribution density of the first V-shaped pit in the low-temperature stress relief layer is 1.0 × 10⁻⁶. 8 / cm 2 ~6.8×10 11 / cm 2 .

[0014] As an improvement to the above technical solution, the low-temperature stress relief layer is a first Si-doped GaN layer, the thickness of which is 10 nm to 500 nm, and the Si doping concentration is 1.2 × 10⁻⁶. 17 / cm 3 ~5.6×10 18 / cm 3 ;or, The low-temperature stress relief layer comprises a periodically alternating first InGaN layer and a second Si-doped GaN layer, with a period number of 2 to 8; the In composition of the first InGaN layer is 0.01 to 0.20, and the thickness is 1 nm to 3 nm; the thickness of the second Si-doped GaN layer is 1 nm to 3 nm, and the Si doping concentration is 1.2 × 10⁻⁶. 17 / cm 3 ~5.6×10 18 / cm 3 .

[0015] As an improvement to the above technical solution, the P-type semiconductor layer is a Mg-doped AlGaInN layer, wherein the proportion of Al component in the Mg-doped AlGaInN layer is 0~0.3%, the proportion of In component is 0~0.3%, the thickness is 20nm~500nm, and the doping concentration of Mg element is 2.5×10⁻⁶. 19 / cm 3 ~5.8×10 20 / cm 3 The growth temperature is 950℃~1050℃.

[0016] Accordingly, the present invention also provides a method for preparing a blue-green dual-band LED epitaxial wafer, which includes the following steps: (1) A buffer layer is grown on the substrate; (2) A first N-type semiconductor layer is grown on the buffer layer; (3) A green light multi-quantum well layer is grown on the first N-type semiconductor layer; (4) A second N-type semiconductor layer is grown on the green light multi-quantum well layer; (5) A low-temperature stress relief layer is grown on the second N-type semiconductor layer; (6) A blue light multi-quantum well layer is grown on the low-temperature stress relief layer; (7) An electron blocking layer is grown on the blue light multi-quantum well layer; (8) A P-type semiconductor layer is grown on the electron blocking layer; The green light multi-quantum well layer includes a periodically alternating stacked green light InGaN quantum well layer and a green light GaN quantum barrier layer, and the blue light multi-quantum well layer includes a periodically alternating stacked blue light InGaN quantum well layer and a blue light GaN quantum barrier layer. The bandgap width of the green InGaN quantum well layer is less than the bandgap width of the blue InGaN quantum well layer; The green GaN quantum barrier layer and the blue GaN quantum barrier layer are respectively doped with Si element, and the doping concentration of Si element in the green GaN quantum barrier layer is greater than or equal to the doping concentration of Si element in the blue GaN quantum barrier layer. The growth temperature of the first N-type semiconductor layer is greater than the growth temperature of the second N-type semiconductor layer.

[0017] Implementing this invention has the following beneficial effects: 1. This invention places a green quantum well layer between a first N-type semiconductor layer and a second N-type semiconductor layer, with the growth temperature of the first N-type semiconductor layer being higher than that of the second N-type semiconductor layer. This allows the second N-type semiconductor layer deposited on top of the green quantum well layer to grow at a relatively lower temperature. This suppresses the precipitation and segregation of In groups within the green quantum well layer during high-temperature growth, thereby reducing structural defects in the green quantum well layer and improving crystal quality, thus enhancing the luminous efficiency of the LED chip. Simultaneously, the high-temperature growth mode of the first N-type semiconductor layer results in a higher surface mobility of precursor atoms in the first N-type semiconductor layer material, making it more inclined towards two-dimensional material growth. This is beneficial for the merging and elimination of defects in the semiconductor material, further improving the luminous efficiency, brightness, and yield of the LED chip.

[0018] 2. By controlling the bandgap of the green InGaN quantum well layer to be less than that of the blue InGaN quantum well layer, the green InGaN quantum well layer with a low bandgap can store some electrons, which can reduce the electron migration rate. At the same time, the doping concentration of Si element in the green GaN quantum barrier layer is greater than or equal to the doping concentration of Si element in the blue GaN quantum barrier layer. The two work together to regulate the distribution of electrons in the blue multi-quantum well layer and improve the electron-hole matching degree in the blue multi-quantum well layer, thereby further improving the luminous efficiency of the LED chip. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a blue-green dual-band LED epitaxial wafer according to an embodiment of the present invention; Figure 2 yes Figure 1 The diagram shows the structure of the green multi-quantum-well layer in the blue-green dual-band LED epitaxial wafer. Figure 3 yes Figure 1 The diagram shows the structure of the blue light multi-quantum well layer in the blue-green dual-band LED epitaxial wafer. Figure 4 This is a schematic diagram of the structure of a blue-green dual-band LED epitaxial wafer according to another embodiment of the present invention; The structure includes a substrate 100, a buffer layer 200, a first N-type semiconductor layer 300, a green light multi-quantum well layer 400, a second N-type semiconductor layer 500, a low-temperature stress relief layer 600, a blue light multi-quantum well layer 700, an electron blocking layer 800, a P-type semiconductor layer 900, a green light InGaN quantum well layer 410, a green light GaN quantum barrier layer 420, a blue light InGaN quantum well layer 710, a blue light GaN quantum barrier layer 720, a first V-shaped pit 610, a second V-shaped pit 730, and a third V-shaped pit 810. Detailed Implementation

[0020] 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.

[0021] 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.

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0023] See Figures 1 to 2 As shown, the present invention provides a blue-green dual-band LED epitaxial wafer, comprising a substrate 100 and a buffer layer 200, a first N-type semiconductor layer 300, a green light multi-quantum well layer 400, a second N-type semiconductor layer 500, a low-temperature stress relief layer 600, a blue light multi-quantum well layer 700, an electron blocking layer 800 and a P-type semiconductor layer 900 sequentially stacked on the substrate 100; The green light multi-quantum well layer 400 includes a periodically alternating stacked green light InGaN quantum well layer 410 and a green light GaN quantum barrier layer 420, and the blue light multi-quantum well layer 700 includes a periodically alternating stacked blue light InGaN quantum well layer 710 and a blue light GaN quantum barrier layer 720. The bandgap of the green InGaN quantum well layer 410 is less than the bandgap of the blue InGaN quantum well layer 710; The green GaN quantum barrier layer 420 and the blue GaN quantum barrier layer 720 are respectively doped with Si element, and the doping concentration of Si element in the green GaN quantum barrier layer 420 is greater than or equal to the doping concentration of Si element in the blue GaN quantum barrier layer 720. The growth temperature of the first N-type semiconductor layer 300 is greater than the growth temperature of the second N-type semiconductor layer 500.

[0024] The blue-green dual-band LED epitaxial wafer of the present invention comprises a substrate 100, a buffer layer 200, a first N-type semiconductor layer 300, a green quantum well layer 400, a second N-type semiconductor layer 500, a low-temperature stress relief layer 600, a blue quantum well layer 700, an electron blocking layer 800, and a P-type semiconductor layer 900 stacked sequentially. When a forward voltage is applied to an LED chip fabricated using the blue-green dual-band LED epitaxial wafer of the present invention, electrons and holes will undergo radiative recombination in the blue quantum well layer 700 to generate blue light, thereby achieving electroluminescence. Part of the blue light generated by the blue quantum well layer 700 will pass through the green quantum well layer 400, which receives the excitation of the blue light and converts it into green light through photoluminescence. This design approach combines electroluminescence and photoluminescence to enable a single LED chip to emit both blue and green light waves. Applying this LED chip to LED backlight sources for displays can reduce the cost of RGB-LED backlight sources and decrease the amount of phosphor used in white LED backlight sources. Furthermore, compared to traditional blue-green dual-band LED chips where both the blue multi-quantum well layer 700 and the green multi-quantum well layer 400 employ electroluminescence, this invention further improves the luminous efficiency of the LED chip and simultaneously stabilizes the green light intensity while improving the blue light intensity, thus enhancing the stability and matching of dual-band emission.

[0025] Further explanation: By placing a green multi-quantum-well layer 400 between a first N-type semiconductor layer 300 and a second N-type semiconductor layer 500, and with the growth temperature of the first N-type semiconductor layer 300 being higher than that of the second N-type semiconductor layer 500, the luminous efficiency of the blue-green dual-band LED epitaxial wafer can be improved. Specifically, the second N-type semiconductor layer 500, deposited on the green multi-quantum-well layer 400, adopts a relatively low growth temperature, which can suppress the precipitation and segregation of In groups within the green multi-quantum-well layer 400 during high-temperature growth, preventing damage to the interface structure and degradation of the crystal quality, thereby preventing a decrease in luminous efficiency and brightness. Simultaneously, the first N-type semiconductor layer 300 adopts a high-temperature growth mode. Under high-temperature growth conditions, the surface mobility of semiconductor precursor atoms is higher, favoring two-dimensional material growth, which is beneficial for the merging and elimination of defects in the semiconductor material. This results in a first N-type semiconductor layer 300 with higher crystal quality and a smoother surface, which is beneficial for improving the luminous efficiency, brightness, and yield of the LED chip.

[0026] Furthermore, the green multi-quantum well layer 400 in this invention includes periodically alternating layers of green InGaN quantum well layer 410 and green GaN quantum barrier layer 420. The bandgap of the green InGaN quantum well layer 410 is less than the bandgap of the blue InGaN quantum well layer 710. The low bandgap of the green InGaN quantum well layer 410 can store some electrons, thereby reducing the electron migration rate. At the same time, the Si doping concentration in the green GaN quantum barrier layer 420 is greater than or equal to the Si doping concentration in the blue GaN quantum barrier layer 720. The combination of these two elements can regulate the electron distribution in the blue multi-quantum well layer 700 and improve the electron-hole matching degree in the blue multi-quantum well layer 700, thereby improving the overall luminous efficiency of the LED chip.

[0027] In one embodiment, the ratio of the Si doping concentration in the green GaN quantum barrier layer 420 to the Si doping concentration in the blue GaN quantum barrier layer 720 is 2 to 30, which is beneficial to further improve the luminous efficiency of the LED chip.

[0028] For example, the ratio of the Si doping concentration in the green GaN quantum barrier layer 420 to the Si doping concentration in the blue GaN quantum barrier layer 720 includes, but is not limited to, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or any two of the above values ​​as endpoints within a range.

[0029] More preferably, the ratio of the Si doping concentration in the green GaN quantum barrier layer 420 to the Si doping concentration in the blue GaN quantum barrier layer 720 is 5 to 15.

[0030] In one embodiment, the In content of the green InGaN quantum well layer 410 is 0.22~0.28, the thickness is 2.1nm~4.8nm, the growth temperature is 680℃~930℃, and the growth pressure is 30torr~360torr. Specifically, the In content of the green InGaN quantum well layer 410 is exemplarily 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, or 0.28, but is not limited thereto. The thickness of the green InGaN quantum well layer 410 is exemplarily 2.1nm, 2.3nm, 2.5nm, 2.8nm, 3nm, 3.3nm, 3.5nm, 3.8nm, 4nm, 4.3nm, 4.5nm, or 4.8nm, but is not limited thereto.

[0031] In one embodiment, the Si doping concentration in the green GaN quantum barrier layer 420 is 3.6 × 10⁻⁶. 17 / cm 3 ~5.6×10 18 / cm 3 The thickness is 5nm~15nm, the growth temperature is 800℃~1050℃, and the growth pressure is 30torr~360torr. For example, the Si doping concentration in the green GaN quantum barrier layer 420 is 3.6×10⁻⁶. 17 / cm 3 5×10 17 / cm 3 7.5×10 17 / cm 3 1×10 18 / cm 3 2.5×10 18 / cm 3 3×10 18 / cm 3 5×10 18 / cm 3 Or 5.6×10 18 / cm 3 However, it is not limited to this. For example, the thickness of the green GaN quantum barrier layer 420 is 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm or 15nm, but is not limited to this.

[0032] In one embodiment, the proportion of In component in the blue InGaN quantum well layer 710 is 0.05~0.19, the thickness is 2.1nm~4.8nm, the growth temperature is 720℃~930℃, and the growth pressure is 30torr~360torr. Specifically, the proportion of In component in the blue InGaN quantum well layer 710 is exemplarily 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, but is not limited thereto. For example, the thickness of the blue InGaN quantum well layer 710 is 2.1nm, 2.3nm, 2.5nm, 2.8nm, 3nm, 3.3nm, 3.5nm, 3.8nm, 4nm, 4.3nm, 4.5nm or 4.8nm, but is not limited thereto.

[0033] In one embodiment, the Si doping concentration in the blue GaN quantum barrier layer 720 is 1.8 × 10⁻⁶. 17 / cm 3 ~9.6×10 17 / cm3 The thickness is 5nm~15nm, the growth temperature is 780℃~950℃, and the growth pressure is 30torr~360torr. Specifically, in this embodiment, the Si doping concentration in the blue GaN quantum barrier layer 720 can be determined based on the ratio of the Si doping concentration in the green GaN quantum barrier layer and the blue GaN quantum barrier layer, as well as the specific value of the Si doping concentration in the green GaN quantum barrier layer. The thickness of the blue GaN quantum barrier layer 720 is exemplarily 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, or 15nm, but is not limited to these.

[0034] The above optimization settings are conducive to further improving the overall luminous efficiency of LED chips.

[0035] It should be noted that in this embodiment, the In composition ratio of the green InGaN quantum well layer 410 is greater than that of the blue InGaN quantum well layer 710. Since the band gap is inversely proportional to the In composition ratio, that is, the larger the In composition ratio, the smaller the band gap, the green InGaN quantum well layer 410 has a smaller band gap than the blue InGaN quantum well layer 710. This allows the green InGaN quantum well layer 410 with a smaller band gap to store some electrons, thereby reducing the electron migration rate and improving the matching degree between electrons and holes in the active region.

[0036] In one embodiment, the number of alternating growth cycles of the green InGaN quantum well layer 410 and the green GaN quantum barrier layer 420 in the green multi-quantum well layer 400 is 2 to 15, exemplarily 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, but not limited thereto; the number of alternating growth cycles of the blue InGaN quantum well layer 710 and the blue GaN quantum barrier layer 720 in the blue multi-quantum well layer 700 is 2 to 15, exemplarily 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, but not limited thereto.

[0037] In one embodiment, the difference between the growth temperature of the first N-type semiconductor layer 300 and the growth temperature of the second N-type semiconductor layer 500 is 100°C to 350°C, which is beneficial to further improve the luminous efficiency of the LED chip.

[0038] For example, the difference between the growth temperature of the first N-type semiconductor layer 300 and the growth temperature of the second N-type semiconductor layer 500 includes, but is not limited to, 100°C, 120°C, 140°C, 150°C, 160°C, 180°C, 200°C, 220°C, 240°C, 250°C, 260°C, 280°C, 300°C, 320°C, 350°C, or any two of the above point values ​​as endpoint values.

[0039] More preferably, the difference between the growth temperature of the first N-type semiconductor layer 300 and the growth temperature of the second N-type semiconductor layer 500 is 120°C to 270°C.

[0040] In one embodiment, the first N-type semiconductor layer 300 is a GaN material doped with Si, and the thickness of the first N-type semiconductor layer 300 is 0.8 μm to 8 μm, exemplarily 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm, but not limited thereto; the Si doping concentration in the first N-type semiconductor layer 300 is 3.6 × 10⁻⁶. 18 / cm 3 ~5.8×10 20 / cm 3 For example, it is 3.6 × 10 18 / cm 3 5×10 18 / cm 3 8.5×10 18 / cm 3 1×10 19 / cm 3 3×10 19 / cm 3 5×10 19 / cm 3 8.5×10 19 / cm 3 1×10 20 / cm 3 5×10 20 / cm 3 Or 5.8×10 20 / cm 3However, it is not limited to this; the growth temperature of the first N-type semiconductor layer 300 is 950℃~1250℃, exemplarily 950℃, 980℃, 1000℃, 1020℃, 1050℃, 1080℃, 1100℃, 1120℃, 1180℃, 1200℃, 1220℃ or 1250℃, but not limited to this; the growth pressure of the first N-type semiconductor layer 300 is 30 torr~360 torr, exemplarily 30 torr, 50 torr, 100 torr, 130 torr, 150 torr, 180 torr, 200 torr, 230 torr, 250 torr, 280 torr, 300 torr, 330 torr or 360 torr, but not limited to this.

[0041] The second N-type semiconductor layer 500 is a GaN material doped with Si. The thickness of the second N-type semiconductor layer 500 is 0.8 μm to 8 μm, exemplarily 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm, but not limited thereto; the Si doping concentration in the second N-type semiconductor layer 500 is 3.6 × 10⁻⁶. 18 / cm 3 ~5.8×10 20 / cm 3 For example, it is 3.6 × 10 18 / cm 3 5×10 18 / cm 3 8.5×10 18 / cm 3 1×10 19 / cm 3 3×10 19 / cm 3 5×10 19 / cm 3 8.5×10 19 / cm 3 1×10 20 / cm 3 3×10 20 / cm 3 5×10 20 / cm 3 Or 5.8×10 20 / cm 3 However, it is not limited to this; the growth temperature of the second N-type semiconductor layer 500 is 820℃~1150℃, and the growth pressure is 30 torr~360 torr.

[0042] The above optimization settings are conducive to further reducing defects in epitaxial wafers, improving the crystal quality of epitaxial wafers, and thus further improving the luminous efficiency of LED chips.

[0043] Preferably, the thickness of the first N-type semiconductor layer 300 is greater than or equal to the thickness of the second N-type semiconductor layer 500, and the Si doping concentration of the first N-type semiconductor layer 300 is greater than or equal to the Si doping concentration of the second N-type semiconductor layer 500. The relatively higher thickness and Si doping concentration of the first N-type semiconductor layer 300 can further improve the uniformity of electron concentration distribution in the blue light multi-quantum well layer, further improve radiative recombination efficiency, and thus further improve the luminous efficiency of the LED chip.

[0044] In one embodiment, the low-temperature stress relief layer 600 is provided with a first V-shaped pit 610 penetrating the low-temperature stress relief layer 600; The blue light multi-quantum well layer 700 has a second V-shaped pit 730 formed in the corresponding region of the first V-shaped pit 610; The electron blocking layer 800 has a third V-shaped pit 810 formed in the corresponding area of ​​the second V-shaped pit 730; The third V-shaped pit 810 is filled by the P-type semiconductor layer 900.

[0045] In this embodiment, a V-shaped pit is contained between the low-temperature stress relief layer 600 and the P-type semiconductor layer 900. The low-temperature stress relief layer 600 is an open V-shaped pit layer, and the P-type semiconductor layer 900 is a V-shaped pit merging layer. Through the above structural improvement, dislocations can be shielded and hole transport can be improved, thereby reducing the probability of carrier recombination near dislocations and improving hole injection efficiency, thereby further improving the luminous efficiency of the blue-green dual-band LED epitaxial wafer.

[0046] In one embodiment, the distribution density of the first V-shaped pits 610 in the low-temperature stress relief layer 600 is 1.0 × 10⁻⁶. 8 / cm 2 ~6.8×10 11 / cm 2 This is beneficial for further improving the luminous efficiency of blue-green dual-band LED epitaxial wafers. For example, the distribution density of the first V-shaped pits 610 in the low-temperature stress relief layer 600 is 1.0 × 10⁻⁶. 8 / cm 2 5×10 8 / cm 2 8×10 8 / cm 2 1×10 9 / cm 2 5×10 9 / cm 2 8×109 / cm 2 9×10 9 / cm 2 1×10 10 / cm 2 5×10 10 / cm 2 8×10 10 / cm 2 9×10 10 / cm 2 1×10 11 / cm 2 5×10 11 / cm 2 Or 6.8×10 11 / cm 2 However, it is not limited to this.

[0047] It should be noted that by controlling parameters such as growth temperature, growth pressure, growth rate, or growth time during the growth process of the low-temperature stress relief layer 600, a first V-shaped pit 610 with a predetermined distribution density can be formed in the low-temperature stress relief layer 600, thereby correspondingly forming a second V-shaped pit 730 and a third V-shaped pit 810 in the subsequently grown blue light multi-quantum well layer 700 and electron blocking layer 800. Optionally, the distribution density of the V-shaped pits can be increased by reducing the growth temperature and / or reducing the growth pressure.

[0048] Preferably, the first V-shaped pits 610 are evenly distributed in the low-temperature stress relief layer 600 and are of the same size.

[0049] In one embodiment, the low-temperature stress relief layer 600 is a first Si-doped GaN layer, the thickness of which is 10 nm to 500 nm, and the Si doping concentration is 1.2 × 10⁻⁶. 17 / cm 3 ~5.6×10 18 / cm 3 The growth temperature is 800℃~1000℃, and the pressure is 30 torr~360 torr; Alternatively, the low-temperature stress relief layer 600 comprises a periodically alternating first InGaN layer and a second Si-doped GaN layer, with a period number of 2 to 8; the first InGaN layer has an In content of 0.01 to 0.20, a thickness of 1 nm to 3 nm, a growth temperature of 760°C to 960°C, and a pressure of 30 torr to 360 torr; the second Si-doped GaN layer has a thickness of 1 nm to 3 nm and a Si doping concentration of 1.2 × 10⁻⁶. 17 / cm 3 ~5.6×10 18 / cm 3 The growth temperature is 800℃~1000℃, and the pressure is 30 torr~360 torr.

[0050] Preferably, the growth temperature of the P-type semiconductor layer 900 is greater than or equal to the growth temperature of the low-temperature stress relief layer 600, the blue light multi-quantum well layer 700, and the electron blocking layer 800, respectively. That is, the P-type semiconductor layer 900 adopts high-temperature growth conditions, so that the P-type semiconductor layer 900 can completely fill the third V-shaped pit 810 and form a complete surface.

[0051] In one embodiment, the P-type semiconductor layer 900 is a Mg-doped AlGaInN layer, wherein the Al content in the Mg-doped AlGaInN layer is 0~0.3%, the In content is 0~0.3%, the thickness is 20nm~500nm, and the Mg doping concentration is 2.5×10⁻⁶. 19 / cm 3 ~5.8×10 20 / cm 3 The growth temperature is 950℃~1050℃, and the pressure is 30 torr~360 torr.

[0052] Accordingly, this embodiment also provides a method for preparing a blue-green dual-band LED epitaxial wafer, which includes the following steps: (1) A buffer layer 200 is grown on the substrate 100; (2) A first N-type semiconductor layer 300 is grown on the buffer layer 200; (3) A green light multi-quantum well layer 400 is grown on the first N-type semiconductor layer 300; (4) A second N-type semiconductor layer 500 is grown on the green light multi-quantum well layer 400; (5) A low-temperature stress relief layer 600 is grown on the second N-type semiconductor layer 500; (6) A blue light multi-quantum well layer 700 is grown on the low-temperature stress relief layer 600; (7) An electron blocking layer 800 is grown on the blue light multi-quantum well layer 700; (8) A P-type semiconductor layer 900 is grown on the electron blocking layer 800; The green light multi-quantum well layer 400 includes a periodically alternating stacked green light InGaN quantum well layer 410 and a green light GaN quantum barrier layer 420, and the blue light multi-quantum well layer 700 includes a periodically alternating stacked blue light InGaN quantum well layer 710 and a blue light GaN quantum barrier layer 720. The bandgap of the green InGaN quantum well layer 410 is less than the bandgap of the blue InGaN quantum well layer 710; The green GaN quantum barrier layer 420 and the blue GaN quantum barrier layer 720 are respectively doped with Si element, and the doping concentration of Si element in the green GaN quantum barrier layer 420 is greater than or equal to the doping concentration of Si element in the blue GaN quantum barrier layer 720. The growth temperature of the first N-type semiconductor layer 300 is greater than the growth temperature of the second N-type semiconductor layer 500.

[0053] The technical solution of the present invention will be further described below through embodiments and comparative examples.

[0054] Example 1 This embodiment provides a blue-green dual-band LED epitaxial wafer, including a substrate and a buffer layer, a first N-type semiconductor layer, a green light multi-quantum well layer, a second N-type semiconductor layer, a low-temperature stress relief layer, a blue light multi-quantum well layer, an electron blocking layer and a P-type semiconductor layer sequentially stacked on the substrate. The green light multi-quantum well layer consists of periodically alternating layers of green InGaN quantum well layers and green GaN quantum barrier layers, with a period number of 8; the blue light multi-quantum well layer consists of periodically alternating layers of blue InGaN quantum well layers and blue GaN quantum barrier layers, with a period number of 8. In the green InGaN quantum well layer, the In content is 0.22% and the thickness is 3 nm; in the green GaN quantum barrier layer, the Si doping concentration is 7.5 × 10⁻⁶. 17 / cm 3 The thickness is 9nm; The In composition of the blue InGaN quantum well layer is 0.08%, and the thickness is 3 nm; the Si doping concentration of the blue GaN quantum barrier layer is 7.5 × 10⁻⁶. 17 / cm 3 The thickness is 9nm.

[0055] In this embodiment, the Si doping concentration in the green GaN quantum barrier layer is equal to the Si doping concentration in the blue GaN quantum barrier layer. Meanwhile, since the proportion of In in the green InGaN quantum well layer is greater than that in the blue InGaN quantum well layer, the band gap of the green InGaN quantum well layer is less than that of the blue InGaN quantum well layer. The first N-type semiconductor layer is made of Si-doped GaN material, with a thickness of 2 μm and a Si doping concentration of 8.5 × 10⁻⁶. 18 / cm 3The growth temperature is 1020℃; the second N-type semiconductor layer is a Si-doped GaN material with a thickness of 2μm and a Si doping concentration of 8.5×10⁻⁶. 18 / cm 3 The growth temperature is 900℃; In this embodiment, the growth temperature of the first N-type semiconductor layer is greater than that of the second N-type semiconductor layer, and the difference between the growth temperature of the first N-type semiconductor layer and the growth temperature of the second N-type semiconductor layer is 120°C.

[0056] Example 2 This embodiment provides a blue-green dual-band LED epitaxial wafer, which is basically the same as that in Embodiment 1, except that: In Example 2, the Si doping concentration in the green GaN quantum barrier layer is 2.5 × 10⁻⁶. 18 / cm 3 The Si doping concentration in the blue GaN quantum barrier layer is 5.0 × 10⁻⁶. 17 / cm 3 That is, in Example 2, the doping concentration of Si element in the green GaN quantum barrier layer is greater than that in the blue GaN quantum barrier layer, and the ratio of the doping concentration of Si element in the green GaN quantum barrier layer to that in the blue GaN quantum barrier layer is 5. Meanwhile, in Example 2, the growth temperature of the first N-type semiconductor layer is 1150°C and the growth temperature of the second N-type semiconductor layer is 880°C, that is, the difference between the growth temperature of the first N-type semiconductor layer and the growth temperature of the second N-type semiconductor layer is 270°C.

[0057] Example 3 This embodiment provides a blue-green dual-band LED epitaxial wafer, which is basically the same as that in Embodiment 2, except that: In Example 3, the low-temperature stress relief layer has a first V-shaped pit penetrating through it. A second V-shaped pit is formed in the corresponding region of the first V-shaped pit in the blue light multi-quantum well layer. A third V-shaped pit is formed in the corresponding region of the second V-shaped pit in the electron blocking layer. The third V-shaped pit is filled by a P-type semiconductor layer. The distribution density of the first V-shaped pit in the low-temperature stress relief layer is 9.0 × 10⁻⁶. 9 / cm 2 .

[0058] Example 4 This embodiment provides a blue-green dual-band LED epitaxial wafer, which is basically the same as that in Embodiment 3, except that: In Example 4, the thickness of the first N-type semiconductor layer is 6 μm, and the Si doping concentration is 1 × 10⁻⁶. 20 / cm 3The thickness of the second N-type semiconductor layer is 3 μm, and the Si doping concentration is 5 × 10⁻⁶. 18 / cm 3 That is, in Example 4, the thickness of the first N-type semiconductor layer is greater than or equal to the thickness of the second N-type semiconductor layer, and the Si doping concentration of the first N-type semiconductor layer is greater than or equal to the Si doping concentration of the second N-type semiconductor layer.

[0059] Comparative Example 1 This comparative example provides a blue-green dual-band LED epitaxial wafer. The difference between this comparative example and Example 1 is that: In Comparative Example 1, the Si doping concentration in the green GaN quantum barrier layer is 1.8 × 10⁻⁶. 17 / cm 3 The Si doping concentration in the blue GaN quantum barrier layer is 5.0 × 10⁻⁶. 17 / cm 3 That is, in Comparative Example 1, the doping concentration of Si element in the green GaN quantum barrier layer is < the doping concentration of Si element in the blue GaN quantum barrier layer. Meanwhile, in Comparative Example 1, the growth temperature of the first N-type semiconductor layer is 900℃, and the growth temperature of the second N-type semiconductor layer is 900℃, that is, the growth temperature of the first N-type semiconductor layer and the growth temperature of the second N-type semiconductor layer are equal.

[0060] Performance testing: The blue-green dual-band LED epitaxial wafers obtained in Examples 1 to 4 and Comparative Example 1 were fabricated into LED chips using the same chip process conditions. Their luminous efficiency was tested, and the luminous efficiency improvement rate of each example was calculated based on Comparative Example 1.

[0061] Specifically, the test results are shown in Table 1 below: Table 1 Performance Test Results

[0062] As can be seen from the experimental data in Table 1, the present invention can improve the luminous efficiency of LED chips by improving the structure of the blue-green dual-band LED epitaxial wafer. Compared with Comparative Example 1, the luminous efficiency improvement rate of Examples 1 to 4 reaches 1.65% to 2.35%.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A blue-green dual-band LED epitaxial wafer, characterized in that, It includes a substrate and a buffer layer, a first N-type semiconductor layer, a green light multi-quantum well layer, a second N-type semiconductor layer, a low-temperature stress relief layer, a blue light multi-quantum well layer, an electron blocking layer and a P-type semiconductor layer, which are sequentially stacked on the substrate. The green light multi-quantum well layer includes a periodically alternating stacked green light InGaN quantum well layer and a green light GaN quantum barrier layer, and the blue light multi-quantum well layer includes a periodically alternating stacked blue light InGaN quantum well layer and a blue light GaN quantum barrier layer. The bandgap width of the green InGaN quantum well layer is less than the bandgap width of the blue InGaN quantum well layer; The green GaN quantum barrier layer and the blue GaN quantum barrier layer are respectively doped with Si element, and the doping concentration of Si element in the green GaN quantum barrier layer is greater than or equal to the doping concentration of Si element in the blue GaN quantum barrier layer. The growth temperature of the first N-type semiconductor layer is greater than the growth temperature of the second N-type semiconductor layer.

2. The blue-green dual-band LED epitaxial wafer according to claim 1, characterized in that, The ratio of the Si doping concentration in the green GaN quantum barrier layer to the Si doping concentration in the blue GaN quantum barrier layer is 2 to 30.

3. The blue-green dual-band LED epitaxial wafer according to claim 1, characterized in that, The difference between the growth temperature of the first N-type semiconductor layer and the growth temperature of the second N-type semiconductor layer is 100℃~350℃.

4. The blue-green dual-band LED epitaxial wafer according to claim 3, characterized in that, Both the first N-type semiconductor layer and the second N-type semiconductor layer are GaN materials doped with Si, and the Si doping concentration of the first N-type semiconductor layer is greater than or equal to the Si doping concentration of the second N-type semiconductor layer. The thickness of the first N-type semiconductor layer is greater than or equal to the thickness of the second N-type semiconductor layer.

5. The blue-green dual-band LED epitaxial wafer according to claim 2, characterized in that, The green InGaN quantum well layer has an In content of 0.22-0.28 and a thickness of 2.1 nm-4.8 nm. The Si doping concentration in the green GaN quantum barrier layer is 3.6 × 10⁻⁶. 17 / cm 3 ~5.6×10 18 / cm 3 The thickness is 5nm~15nm; The blue InGaN quantum well layer has an In content of 0.05~0.19 and a thickness of 2.1nm~4.8nm. The Si doping concentration in the blue GaN quantum barrier layer is 1.8 × 10⁻⁶. 17 / cm 3 ~9.6×10 17 / cm 3 The thickness is 5nm~15nm.

6. The blue-green dual-band LED epitaxial wafer according to claim 4, characterized in that, The thickness of the first N-type semiconductor layer is 0.8 μm to 8 μm, and the Si doping concentration is 3.6 × 10⁻⁶. 18 / cm 3 ~5.8×10 20 / cm 3 The growth temperature is 950℃~1250℃; The thickness of the second N-type semiconductor layer is 0.8 μm to 8 μm, and the Si doping concentration is 3.6 × 10⁻⁶. 18 / cm 3 ~5.8×10 20 / cm 3 The growth temperature is 820℃~1150℃.

7. The blue-green dual-band LED epitaxial wafer according to claim 1, characterized in that, The low-temperature stress relief layer is provided with a first V-shaped pit that penetrates the low-temperature stress relief layer; The blue light multi-quantum well layer has a second V-shaped pit formed in the corresponding region of the first V-shaped pit; The electron blocking layer has a third V-shaped pit formed in the corresponding area of ​​the second V-shaped pit; The third V-shaped pit is filled by the P-type semiconductor layer.

8. The blue-green dual-band LED epitaxial wafer according to claim 1, characterized in that, The low-temperature stress relief layer is a first Si-doped GaN layer with a thickness of 10 nm to 500 nm and a Si doping concentration of 1.2 × 10⁻⁶. 17 / cm 3 ~5.6×10 18 / cm 3 ; or, The low-temperature stress relief layer comprises a periodically alternating first InGaN layer and a second Si-doped GaN layer, with a period number of 2 to 8; the In composition of the first InGaN layer is 0.01 to 0.20, and the thickness is 1 nm to 3 nm; the thickness of the second Si-doped GaN layer is 1 nm to 3 nm, and the Si doping concentration is 1.2 × 10⁻⁶. 17 / cm 3 ~5.6×10 18 / cm 3 .

9. The blue-green dual-band LED epitaxial wafer according to claim 1, characterized in that, The p-type semiconductor layer is a Mg-doped AlGaInN layer, wherein the Al content and In content are both 0-0.3%, the thickness is 20 nm-500 nm, and the Mg doping concentration is 2.5 × 10⁻⁶. 19 / cm 3 ~5.8×10 20 / cm 3 The growth temperature is 950℃~1050℃.

10. A method for fabricating a blue-green dual-band LED epitaxial wafer, characterized in that, The method for preparing the blue-green dual-band LED epitaxial wafer according to any one of claims 1-9 comprises the following steps: (1) A buffer layer is grown on the substrate; (2) A first N-type semiconductor layer is grown on the buffer layer; (3) A green light multi-quantum well layer is grown on the first N-type semiconductor layer; (4) A second N-type semiconductor layer is grown on the green light multi-quantum well layer; (5) A low-temperature stress relief layer is grown on the second N-type semiconductor layer; (6) A blue light multi-quantum well layer is grown on the low-temperature stress relief layer; (7) An electron blocking layer is grown on the blue light multi-quantum well layer; (8) A P-type semiconductor layer is grown on the electron blocking layer; The green light multi-quantum well layer includes a periodically alternating stacked green light InGaN quantum well layer and a green light GaN quantum barrier layer, and the blue light multi-quantum well layer includes a periodically alternating stacked blue light InGaN quantum well layer and a blue light GaN quantum barrier layer. The bandgap width of the green InGaN quantum well layer is less than the bandgap width of the blue InGaN quantum well layer; The green GaN quantum barrier layer and the blue GaN quantum barrier layer are respectively doped with Si element, and the doping concentration of Si element in the green GaN quantum barrier layer is greater than or equal to the doping concentration of Si element in the blue GaN quantum barrier layer. The growth temperature of the first N-type semiconductor layer is greater than the growth temperature of the second N-type semiconductor layer.

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