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

Abstract

The invention relates to the technical field of semiconductor devices, in particular to a blue-green dual-waveband LED epitaxial wafer which comprises a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, an electron blocking layer and a P-type semiconductor layer which are sequentially arranged in the epitaxial direction. The multi-quantum well light-emitting layer comprises a non-light-emitting region superlattice layer, a non-light-emitting region quantum well layer, a green light quantum well layer and a blue light quantum well layer which are sequentially, periodically and alternately grown in the epitaxial direction. The backlight source is low in cost, the use of fluorescent powder can be reduced, and the display effect is good.

Description

Technical Field

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

[0002] In the existing technology, LED backlight sources for displays include two types: RGB-LED and white LED. Among them, RGB-LED is formed by packaging three monochromatic LED chips of blue, green and red together, while white LED is formed by combining monochromatic LED chips with phosphors, such as combining a monochromatic blue chip with green and red phosphors, or combining a single blue LED chip with yellow phosphor.

[0003] RGB-LED backlighting offers the best display performance, but it is also the most expensive. White LEDs require phosphors, but different phosphors correspond to significantly different color gamuts, and the uniformity of the phosphor mixed with the adhesive is difficult to control. This results in poor light emission uniformity, inconsistent color tone, easy deviation in color temperature, and poor color rendering. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides a blue-green dual-band LED epitaxial wafer, which has low cost in preparing backlight sources, can reduce the use of phosphors, and has good display effects.

[0005] To address the aforementioned issues, this invention proposes a blue-green dual-band LED epitaxial wafer, comprising a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer arranged sequentially along the epitaxial direction. The multi-quantum-well light-emitting layer includes a non-light-emitting superlattice layer, a non-light-emitting quantum well layer, a green light quantum well layer, and a blue light quantum well layer that are periodically and alternately grown along the epitaxial direction. The non-luminescent superlattice layer comprises a superlattice structure in which a first InGaN layer and a first barrier layer are grown alternately and periodically along the epitaxial direction. The non-light-emitting quantum well layer comprises a superlattice structure of a second InGaN layer and a second barrier layer that are periodically and alternately grown along the epitaxial direction, and the In content of the multiple second InGaN layers increases sequentially along the epitaxial direction. The green quantum well layer comprises a superlattice structure consisting of a green InGaN layer and a third barrier layer that are periodically and alternately grown along the epitaxial direction. The blue quantum well layer comprises a superlattice structure consisting of a blue InGaN layer and a fourth barrier layer that are periodically and alternately grown along the epitaxial direction. Wherein, the In composition content of the second InGaN layer in the first growth cycle of the non-light-emitting region quantum well layer is greater than the In composition content of the first InGaN layer in the non-light-emitting region superlattice layer; The In content of the second InGaN layer in the last growth cycle of the non-luminescent quantum well layer is less than the In content of the green InGaN layer in the green quantum well layer.

[0006] As an improvement to the above technical solution, the growth cycle number of the multi-quantum-well light-emitting layer is 3 to 17; the growth cycle number of the non-light-emitting superlattice layer is 2 to 10; the growth cycle number of the non-light-emitting quantum well layer is 2 to 6; the growth cycle number of the green quantum well layer is 2 to 6; and the growth cycle number of the blue quantum well layer is 2 to 8.

[0007] As an improvement to the above technical solution, the first InGaN layer is made of InGaN material that is intentionally undoped, with an In composition content of X1, 0.002≤X1<0.05, and a growth thickness of 0.1nm~2nm; The first barrier layer includes a first Si-doped GaN layer with a Si doping concentration of 1.28 × 10⁻⁶. 17 / cm³~9.73×10 17 / cm³, with a growth thickness of 0.1nm~2nm; The second InGaN layer is made of intentionally undoped InGaN material with an In content of X2, 0.05≤X2<0.22, and a growth thickness of 2.1nm~4.5nm.

[0008] As an improvement to the above technical solution, the second barrier layer includes a second Si-doped GaN layer one, a second AlGaN layer two, and a second Si-doped GaN layer three; the Si doping concentration of the second Si-doped GaN layer one and the second Si-doped GaN layer three is 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 1.8nm~6.8nm; the second AlGaN layer is not intentionally doped with Si, the Al composition content is Y2, 0.02≤Y2≤0.36, and the growth thickness is 1.0nm~5.8nm.

[0009] As an improvement to the above technical solution, the In content of the second InGaN layer increases linearly along the epitaxial direction; wherein the difference between the maximum and minimum values ​​of the In content of the second InGaN layer is ≤0.1.

[0010] As an improvement to the above technical solution, the green InGaN layer is made of InGaN material that is intentionally undoped, with an In content of X3, 0.22≤X3≤0.28, and a growth thickness of 2.1nm~4.6nm; The third barrier layer includes a third Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm; The blue light InGaN layer is made of intentionally undoped InGaN material with an In content of X4, 0.08≤X4≤0.19, and a growth thickness of 2.1nm~4.8nm; The fourth barrier layer includes a fourth Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm.

[0011] Accordingly, the present invention also provides a method for fabricating a blue-green dual-band LED epitaxial wafer, comprising: Provide a substrate; A buffer layer is grown on the substrate; An N-type semiconductor layer is grown on the buffer layer; A low-temperature stress relief layer is grown on an N-type semiconductor layer; A multi-quantum-well light-emitting layer is grown on a low-temperature stress-relieving layer; An electron blocking layer is grown on a multi-quantum-well light-emitting layer; A P-type semiconductor layer is grown on an electron blocking layer; The multi-quantum-well light-emitting layer includes a non-light-emitting superlattice layer, a non-light-emitting quantum well layer, a green light quantum well layer, and a blue light quantum well layer that are periodically and alternately grown along the epitaxial direction. The non-luminescent superlattice layer comprises a superlattice structure in which a first InGaN layer and a first barrier layer are grown alternately and periodically along the epitaxial direction. The non-light-emitting quantum well layer comprises a superlattice structure of a second InGaN layer and a second barrier layer that are periodically and alternately grown along the epitaxial direction, and the In content of the multiple second InGaN layers increases sequentially along the epitaxial direction. The green quantum well layer comprises a superlattice structure consisting of a green InGaN layer and a third barrier layer that are periodically and alternately grown along the epitaxial direction. The blue quantum well layer comprises a superlattice structure consisting of a blue InGaN layer and a fourth barrier layer that are periodically and alternately grown along the epitaxial direction. Wherein, the In composition content of the second InGaN layer in the first growth cycle of the non-light-emitting region quantum well layer is greater than the In composition content of the first InGaN layer in the non-light-emitting region superlattice layer; The In content of the second InGaN layer in the last growth cycle of the non-luminescent quantum well layer is less than the In content of the green InGaN layer in the green quantum well layer.

[0012] As an improvement to the above technical solution, the growth cycle number of the multi-quantum-well light-emitting layer is 3 to 17; the growth cycle number of the non-light-emitting superlattice layer is 2 to 10; the growth cycle number of the non-light-emitting quantum well layer is 2 to 6; the growth cycle number of the green quantum well layer is 2 to 6; and the growth cycle number of the blue quantum well layer is 2 to 8.

[0013] As an improvement to the above technical solution, the first InGaN layer is made of InGaN material that is intentionally undoped, with an In composition content of X1, 0.002≤X1<0.05, and a growth thickness of 0.1nm~2nm; the growth temperature of the first InGaN layer is 700℃~980℃, and the growth pressure is 30torr~360torr. The first barrier layer includes a first Si-doped GaN layer with a Si doping concentration of 1.28 × 10⁻⁶. 17 / cm³~9.73×10 17 / cm³, with a growth thickness of 0.1nm~2nm; the growth temperature of the first barrier layer is 700℃~980℃, and the growth pressure is 30torr~360torr; The second InGaN layer is made of intentionally undoped InGaN material with an In content of X2, 0.05≤X2<0.22, and a growth thickness of 2.1nm~4.5nm; the growth temperature of the second InGaN layer is 680℃~920℃, and the growth pressure is 30torr~360torr. The second barrier layer comprises a second Si-doped GaN layer one, a second AlGaN layer two, and a second Si-doped GaN layer three; the Si doping concentration of the second Si-doped GaN layer one and the second Si-doped GaN layer three is 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 The growth thickness is 1.8 nm to 6.8 nm. The second AlGaN layer is not intentionally doped with Si, and the Al composition is Y2, 0.02 ≤ Y2 ≤ 0.36, with a growth thickness of 1.0 nm to 5.8 nm. The growth temperature of the second Si-doped GaN layer one, the second AlGaN layer two, and the third Si-doped GaN layer three is 800℃ to 950℃, and the growth pressure is 30 torr to 360 torr.

[0014] As an improvement to the above technical solution, the green InGaN layer is made of intentionally undoped InGaN material, with an In content of X3, 0.22≤X3≤0.28, and a growth thickness of 2.1nm~4.6nm; the growth temperature of the green InGaN layer is 680℃~920℃, and the growth pressure is 30torr~360torr. The third barrier layer includes a third Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm; the growth temperature of the third barrier layer is 800℃~950℃, and the growth pressure is 30torr~360torr; The blue light InGaN layer is made of intentionally undoped InGaN material with an In content of X4, 0.08≤X4≤0.19, and a growth thickness of 2.1nm~4.8nm; the growth temperature of the blue light InGaN layer is 720℃~920℃, and the growth pressure is 30torr~360torr. The fourth barrier layer includes a fourth Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm; the growth temperature of the fourth barrier layer is 800℃~950℃, and the pressure is 30torr~360torr.

[0015] The implementation of this invention has the following beneficial effects: (1) The blue-green dual-band LED epitaxial wafer of the present invention comprises a multi-quantum-well light-emitting layer consisting of a non-light-emitting superlattice layer, a non-light-emitting quantum well layer, a green quantum well layer, and a blue quantum well layer, which are periodically and alternately grown along the epitaxial direction. That is, the multi-quantum-well light-emitting layer can excite two different LED light sources, one in a green band and one in a blue band, thereby reducing the cost of RGB-LED backlight sources and reducing the use of phosphors in white LED backlight sources.

[0016] (2) The In composition of the first InGaN layer in the non-light-emitting region superlattice layer is less than that of the second InGaN layer in the first growth cycle of the non-light-emitting region quantum well layer; the In composition of the second InGaN layer in the last growth cycle of the non-light-emitting region quantum well is less than that of the green InGaN layer. Meanwhile, the In composition of the green InGaN layer is greater than that of the blue InGaN. The multi-quantum-well light-emitting layer designed with the above-mentioned In composition content can effectively reduce the lattice mismatch stress between the quantum well InGaN material and the barrier layer material. The reduction in defects caused by the lattice mismatch stress can significantly improve the quality of the multi-quantum-well layer, which is beneficial for improving the radiative recombination efficiency of the active region, thereby improving the luminous efficacy and yield of the blue-green LED light source. Attached Figure Description

[0017] 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 This is a schematic diagram of the structure of a multi-quantum-well light-emitting layer according to an embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the structure of the second barrier layer in another embodiment of the present invention. Detailed Implementation

[0019] 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.

[0020] See Figure 1 and Figure 2 As shown, this embodiment of the invention provides a blue-green dual-band LED epitaxial wafer, comprising a substrate 100, a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress relief layer 400, a multi-quantum well light-emitting layer 500, an electron blocking layer 600, and a P-type semiconductor layer 700 arranged sequentially along the epitaxial direction.

[0021] Substrate 100 can be made of sapphire, which is currently the most commonly used substrate material. Sapphire substrates have advantages such as mature manufacturing processes, low cost, ease of cleaning and processing, and good stability at high temperatures. Buffer layer 200 can be a GaN buffer layer, AlN buffer layer, or SiN buffer layer, etc. Its main function is to alleviate lattice mismatch and thermal mismatch problems between substrate 100 and the epitaxial layer, thereby improving the crystal quality of the epitaxial layer and enhancing the chip's performance and reliability. N-type semiconductor layer 300 is typically a Si-doped N-type GaN layer. Low-temperature stress relief layer 400 can be a low-temperature GaN layer, low-temperature InGaN layer, etc., used to alleviate stress generated during chip manufacturing. Electron blocking layer 600 can be an AlGaN layer, AlInGaN layer, etc. P-type semiconductor layer 700 is typically a Mg-doped GaN layer.

[0022] The multi-quantum-well light-emitting layer 500 includes a non-light-emitting superlattice layer 510, a non-light-emitting quantum well layer 520, a green quantum well layer 530, and a blue quantum well layer 540 that are periodically and alternately grown along the epitaxial direction, with a period number of 3 to 17; the exemplary period numbers are 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, and 17.

[0023] Specifically, the non-light-emitting superlattice layer 510 includes a superlattice structure of a first InGaN layer 511 and a first barrier layer 512 that are periodically and alternately grown along the epitaxial direction, with a period number of 2 to 10; the period number is exemplarily 2, 3, 4, 5, 6, 7, 8, 9, 10.

[0024] Preferably, the first InGaN layer 511 is made of intentionally undoped InGaN material, with an In content of X1, where 0.002 ≤ X1 < 0.05, and a growth thickness of 0.1 nm to 2 nm; X1 is exemplarily 0.002, 0.009, 0.01, 0.02, 0.03, 0.04, but is not limited thereto. The growth thickness is exemplarily 0.1 nm, 0.3 nm, 0.5 nm, 0.8 nm, 0.9 nm, 1.1 nm, 1.5 nm, 1.7 nm, 2.0 nm, but is not limited thereto.

[0025] The growth temperature of the first InGaN layer 511 is 700℃~980℃, and the growth pressure is 30 torr~360 torr. Examples of growth temperatures include 700℃, 725℃, 750℃, 770℃, 790℃, 810℃, 835℃, 850℃, 890℃, 910℃, 950℃, and 980℃, but are not limited to these. Examples of growth pressures include 30 torr, 50 torr, 70 torr, 90 torr, 100 torr, 120 torr, 150 torr, 170 torr, 190 torr, 250 torr, 280 torr, 310 torr, 350 torr, and 360 torr, but are not limited to these.

[0026] The first barrier layer 512 includes a first Si-doped GaN layer with a Si doping concentration of 1.28 × 10⁻⁶. 17 / cm³~9.73×10 17 / cm³, with a growth thickness of 0.1nm~2nm. An exemplary Si doping concentration is 3.75×10⁻⁶. 17 / cm³, 4.68×10 17 / cm³, 5.11×10 17 / cm³, 6.33×10 17 / cm³, 7.15×10 17 / cm³, but not limited to. Exemplary growth thicknesses are 0.1nm, 0.5nm, 0.7nm, 1.1nm, 1.5nm, and 1.9nm, but not limited to.

[0027] The growth temperature of the first barrier layer 512 is 700℃~980℃, and the growth pressure is 30 torr~360 torr. Examples of growth temperatures include 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, and 980℃, but are not limited to these. Examples of growth pressures include 30 torr, 50 torr, 70 torr, 90 torr, 100 torr, 120 torr, 150 torr, 170 torr, 190 torr, 250 torr, 280 torr, 310 torr, 350 torr, and 360 torr, but are not limited to these.

[0028] Preferably, the non-light-emitting quantum well layer 520 comprises a superlattice structure of a second InGaN layer 521 and a second barrier layer 522 that are periodically and alternately grown along the epitaxial direction, with a period number of 2 to 6, and the In composition content of the multiple layers of the second InGaN layer increases sequentially along the epitaxial direction. Examples of period numbers are 2, 3, 4, 5, and 6.

[0029] The second InGaN layer 521 is made of intentionally undoped InGaN material, with an In content of X2, where 0.05 ≤ X2 < 0.22, and a growth thickness of 2.1 nm to 4.5 nm. Examples of X2 include 0.05, 0.09, 0.1, 0.15, 0.19, and 0.21, but are not limited thereto. Examples of growth thickness include 2.1 nm, 2.3 nm, 2.5 nm, 2.7 nm, 3.5 nm, 3.7 nm, 4.1 nm, 4.3 nm, and 4.5 nm, but are not limited thereto.

[0030] More preferably, the In content of the second InGaN layer increases linearly along the epitaxial direction; wherein the difference between the maximum and minimum In content of the second InGaN layer 521 is ≤0.1. This linearly increasing In content design creates a smooth composition gradient. The difference ≤0.1 ensures the gradual and continuous nature of the composition change, avoiding stress concentration due to lattice mismatch caused by abrupt compositional changes. By controlling the compositional difference within a reasonable range, effective stress buffering is achieved, reducing dislocations and defects caused by drastic compositional changes.

[0031] The growth temperature of the second InGaN layer 521 is 680℃~920℃, and the growth pressure is 30 torr~360 torr. Examples of growth temperatures include 700℃, 750℃, 800℃, 850℃, 900℃, and 920℃, but are not limited to these. Examples of growth pressures include 30 torr, 50 torr, 70 torr, 90 torr, 100 torr, 120 torr, 150 torr, 170 torr, 190 torr, 250 torr, 280 torr, 310 torr, 350 torr, and 360 torr, but are not limited to these.

[0032] In one embodiment of the present invention, the second barrier layer 522 includes a first Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, growth thickness of 5nm~15nm, growth temperature of 800℃-950℃, pressure of 30torr-360torr.

[0033] In another preferred embodiment of the invention, see Figure 3 As shown, the second barrier layer 522 includes a second Si-doped GaN layer 522a, a second AlGaN layer 522c, and a third Si-doped GaN layer 522c; the Si doping concentration of the second Si-doped GaN layer 522a and the third Si-doped GaN layer 522c is 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 1.8nm~6.8nm. An exemplary Si doping concentration is 1.8×10⁻⁶. 17 / cm³, 2.56×10 17 / cm³, 3.54×10 17 / cm³, 4.36×10 17 / cm³, 5.18×10 17 / cm³, 5.95×10 17 / cm³, 6.77×10 17 / cm³, 7.13×10 17 / cm³, 7.56×10 17 / cm³, 7.86×10 17 / cm³, but not limited to. Exemplary growth thicknesses are 2.1nm, 2.3nm, 2.5nm, 2.7nm, 3.5nm, 3.7nm, 4.1nm, 4.3nm, 4.5nm, 5.1nm, 5.7nm, 6.3nm, and 6.8nm, but not limited to.

[0034] The second AlGaN layer 522b is not intentionally doped with Si, and the Al composition is Y2, 0.02≤Y2≤0.36, with a growth thickness of 1.0nm~5.8nm. Examples of Y2 values ​​are 0.02, 0.09, 0.11, 0.17, 0.21, 0.25, 0.29, 0.31, 0.35, and 0.36, but are not limited to these. Examples of growth thickness are 2.1nm, 2.3nm, 2.5nm, 2.7nm, 3.5nm, 3.7nm, 4.1nm, 4.3nm, 4.5nm, 5.1nm, and 5.7nm, but are not limited to these. The growth temperature of the second Si-doped GaN layer 522a, the second AlGaN layer 522b, and the second Si-doped GaN layer 522c are all 800℃~950℃, and the growth pressure is all 30torr~360torr. Examples of growth temperatures include 800℃, 850℃, 870℃, 910℃, 930℃, and 950℃, but are not limited to these. Examples of growth pressures include 30 torr, 50 torr, 70 torr, 90 torr, 100 torr, 120 torr, 150 torr, 170 torr, 190 torr, 250 torr, 280 torr, 310 torr, 350 torr, and 360 torr, but are not limited to these.

[0035] Specifically, the green quantum well layer 530 comprises a superlattice structure consisting of a green InGaN layer 531 and a third barrier layer 532 that are periodically and alternately grown along the epitaxial direction, with a period number of 2 to 6. Examples of such periods are 2, 3, 4, 5, and 6.

[0036] Preferably, the green InGaN layer 531 is made of intentionally undoped InGaN material, with an In content of X3, where 0.22 ≤ X3 ≤ 0.28, and a growth thickness of 2.1 nm to 4.6 nm. Examples of X3 include 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, and 0.28, but are not limited thereto. Examples of growth thickness include 2.1 nm, 2.5 nm, 2.7 nm, 2.9 nm, 3.1 nm, 3.3 nm, 3.7 nm, 3.9 nm, 4.1 nm, 4.3 nm, 4.5 nm, and 4.6 nm, but are not limited thereto.

[0037] The growth temperature of the green InGaN layer 531 is 680℃~920℃, and the growth pressure is 30 torr~360 torr. Examples of growth temperatures include 680℃, 710℃, 750℃, 770℃, 790℃, 810℃, 850℃, 870℃, 890℃, 910℃, and 920℃, but are not limited to these. Examples of growth pressures include 30 torr, 50 torr, 70 torr, 90 torr, 100 torr, 120 torr, 150 torr, 170 torr, 190 torr, 250 torr, 280 torr, 310 torr, 350 torr, and 360 torr, but are not limited to these.

[0038] The third barrier layer 532 includes a third Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm. An exemplary Si doping concentration is 1.8×10⁻⁶. 17 / cm³, 2.56×10 17 / cm³, 3.54×10 17 / cm³, 4.36×10 17 / cm³, 5.18×10 17 / cm³, 5.95×10 17 / cm³, 6.77×10 17 / cm³, 7.13×10 17 / cm³, 7.56×10 17 / cm³, 7.86×10 17 / cm³, but not limited to. Exemplary growth thicknesses are 5nm, 7nm, 8nm, 9nm, 11nm, 13nm, 14nm, and 15nm, but not limited to.

[0039] The growth temperature of the third barrier layer 532 is 800℃~950℃, and the growth pressure is 30 torr~360 torr. Examples of growth temperatures include 800℃, 830℃, 850℃, 890℃, 910℃, 920℃, 930℃, and 950℃, but are not limited to these. Examples of growth pressures include 30 torr, 50 torr, 70 torr, 90 torr, 100 torr, 120 torr, 150 torr, 170 torr, 190 torr, 250 torr, 280 torr, 310 torr, 350 torr, and 360 torr, but are not limited to these.

[0040] The blue quantum well layer 540 comprises a superlattice structure consisting of a blue InGaN layer 541 and a fourth barrier layer 542 that are periodically and alternately grown along the epitaxial direction, with a period number of 2 to 8. Examples of period numbers are 2, 3, 4, 5, 6, 7, and 8.

[0041] The blue InGaN layer 541 is made of intentionally undoped InGaN material with an In content of X4, where 0.08 ≤ X4 ≤ 0.19, and a growth thickness of 2.1 nm to 4.8 nm. Examples of X4 include 0.08, 0.11, 0.13, 0.15, 0.17, 0.18, and 0.19, but are not limited to these. Examples of growth thickness include 2.1 nm, 2.3 nm, 2.7 nm, 2.9 nm, 3.2 nm, 3.4 nm, 3.7 nm, 3.9 nm, 4.3 nm, 4.5 nm, and 4.8 nm, but are not limited to these.

[0042] The growth temperature of the blue InGaN layer 541 is 720℃~920℃, and the growth pressure is 30 torr~360 torr. Examples of growth temperatures include 720℃, 750℃, 780℃, 810℃, 850℃, 870℃, 910℃, and 920℃, but are not limited to these. Examples of growth pressures include 30 torr, 50 torr, 70 torr, 90 torr, 100 torr, 120 torr, 150 torr, 170 torr, 190 torr, 250 torr, 280 torr, 310 torr, 350 torr, and 360 torr, but are not limited to these.

[0043] The fourth barrier layer 542 includes a fourth Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm. An exemplary Si doping concentration is 1.8×10⁻⁶. 17 / cm³, 2.56×10 17 / cm³, 3.54×10 17 / cm³, 4.36×10 17 / cm³, 5.18×10 17 / cm³, 5.95×10 17 / cm³, 6.77×10 17 / cm³, 7.13×10 17 / cm³, 7.56×10 17 / cm³, 7.86×10 17 / cm³, but not limited to. Exemplary growth thicknesses are 5nm, 7nm, 8nm, 9nm, 11nm, 13nm, 14nm, and 15nm, but not limited to.

[0044] The growth temperature of the fourth barrier layer 542 is 800℃~950℃, and the pressure is 30 torr~360 torr. Examples of growth temperatures include 800℃, 810℃, 830℃, 870℃, 890℃, 915℃, 930℃, and 950℃, but are not limited to these. Examples of growth pressures include 30 torr, 50 torr, 70 torr, 90 torr, 100 torr, 120 torr, 150 torr, 170 torr, 190 torr, 250 torr, 280 torr, 310 torr, 350 torr, and 360 torr, but are not limited to these.

[0045] Wherein, the In content of the second InGaN layer 521 of the first growth cycle of the non-light-emitting quantum well layer 520 is greater than the In content of the first InGaN layer 511 of the non-light-emitting superlattice layer 510. The In content of the second InGaN layer 521 in the last growth cycle of the non-light-emitting quantum well layer 520 is less than the In content of the green InGaN layer 531 of the green quantum well layer 530.

[0046] The first cycle features a high-In design, meaning the overall In content of the non-luminescent quantum well layer 520 is higher than that of the non-luminescent superlattice layer 510. This establishes a stress transition band, mitigating the lattice mismatch impact between the superlattice layer and the quantum well layer, and reducing the interface dislocation density. The final cycle features a low-In design, meaning the In content of the second InGaN layer 521 in the last growth cycle is lower than that of the green-light InGaN layer 531. This prevents the non-luminescent region from absorbing radiation photons from the green-light quantum well 530, and also prevents carrier leakage into the non-luminescent region.

[0047] Accordingly, the present invention also provides a method for fabricating a blue-green dual-band LED epitaxial wafer, comprising: Provide a substrate 100; A buffer layer 200 is grown on the substrate 100; An N-type semiconductor layer 300 is grown on the buffer layer 200; A low-temperature stress relief layer 400 is grown on the N-type semiconductor layer 300; A multi-quantum-well light-emitting layer 500 is grown on a low-temperature stress-relieving layer 400; An electron blocking layer 600 is grown on the multi-quantum-well light-emitting layer 500; A P-type semiconductor layer 700 is grown on an electron blocking layer 600; The multi-quantum-well light-emitting layer 500 includes a non-light-emitting superlattice layer 510, a non-light-emitting quantum well layer 520, a green quantum well layer 530, and a blue quantum well layer 540 that are periodically and alternately grown along the epitaxial direction. The non-light-emitting region superlattice layer 510 includes a superlattice structure of a first InGaN layer 511 and a first barrier layer 512 that are periodically and alternately grown along the epitaxial direction. The non-light-emitting quantum well layer 520 includes a superlattice structure of a second InGaN layer 521 and a second barrier layer 522 that are periodically and alternately grown along the epitaxial direction, and the In content of the multiple layers of the second InGaN layer 521 increases sequentially along the epitaxial direction. The green quantum well layer 530 includes a superlattice structure consisting of a green InGaN layer 531 and a third barrier layer 532 that are periodically and alternately grown along the epitaxial direction. The blue quantum well layer 540 includes a superlattice structure consisting of a blue InGaN layer 541 and a fourth barrier layer 542 that are periodically and alternately grown along the epitaxial direction. Wherein, the In content of the second InGaN layer 521 of the first growth cycle of the non-light-emitting quantum well layer 520 is greater than the In content of the first InGaN layer 511 of the non-light-emitting superlattice layer 510. The In content of the second InGaN layer 521 in the last growth cycle of the non-light-emitting quantum well layer 520 is less than the In content of the green InGaN layer 531 of the green quantum well layer 530.

[0048] The technical solution of the present invention will be further described below with reference to specific embodiments and comparative examples.

[0049] Example 1 This embodiment provides a blue-green dual-band LED epitaxial wafer, comprising a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer arranged sequentially along the epitaxial direction.

[0050] The multi-quantum-well light-emitting layer includes a non-light-emitting superlattice layer, a non-light-emitting quantum well layer, a green quantum well layer, and a blue quantum well layer that are grown alternately and periodically along the epitaxial direction, with a period number of 10. The non-luminescent superlattice layer comprises a superlattice structure consisting of a first InGaN layer and a first barrier layer that are periodically and alternately grown along the epitaxial direction, with a period number of 6. The first InGaN layer is made of intentionally undoped InGaN material with an In content of X1=0.025, a growth thickness of 1nm, a growth temperature of 840℃, and a growth pressure of 250 torr. The first barrier layer includes a first Si-doped GaN layer with a Si doping concentration of 4.65 × 10⁻⁶. 17 / cm³, growth thickness of 1nm, growth temperature of 840℃, growth pressure of 250torr; The non-light-emitting quantum well layer comprises a superlattice structure of a second InGaN layer and a second barrier layer that are periodically and alternately grown along the epitaxial direction, with a period number of 4; The second InGaN layer is made of intentionally undoped InGaN material. The In content of the multilayer second InGaN layer is X2, which linearly increases from 0.05 to 0.11 along the epitaxial direction. The growth thickness is 3.3 nm, the growth temperature is 800 °C, and the growth pressure is 250 torr. The second barrier layer includes a second Si-doped GaN layer with a Si doping concentration of 5.7 × 10⁻⁶. 17 / cm³, growth thickness of 10nm, growth temperature of 875℃, growth pressure of 250torr; The green quantum well layer comprises a superlattice structure consisting of a green InGaN layer and a third barrier layer that are periodically and alternately grown along the epitaxial direction, with a period number of 4. The green InGaN layer is made of intentionally undoped InGaN material with an In content of X3=0.25, a growth thickness of 3.3nm, a growth temperature of 800℃, and a growth pressure of 250 torr. The third barrier layer includes a third Si-doped GaN layer with a Si doping concentration of 5.7 × 10⁻⁶. 17 / cm³, growth thickness of 10nm, growth temperature of 875℃, growth pressure of 250torr; The blue quantum well layer comprises a superlattice structure consisting of a blue InGaN layer and a fourth barrier layer that are periodically and alternately grown along the epitaxial direction, with a period number of 5. The blue light InGaN layer is made of intentionally undoped InGaN material with an In content of X4=0.14, a growth thickness of 3.4nm, a growth temperature of 820℃, and a growth pressure of 250 torr. The fourth barrier layer includes a fourth Si-doped GaN layer with a Si doping concentration of 5.7 × 10⁻⁶. 17 / cm³, growth thickness of 5nm~15nm, growth temperature of 875℃, pressure of 250torr.

[0051] Example 2 The difference between this embodiment and Embodiment 1 is that: The second InGaN layer is made of intentionally undoped InGaN material. The In content of the multilayer second InGaN layer is X2, which increases from 0.05 to 0.18 along the epitaxial direction. The growth thickness is 3.3 nm, the growth temperature is 800 °C, and the growth pressure is 250 torr.

[0052] Example 3 The difference between this embodiment and Embodiment 1 is that: The second InGaN layer is made of intentionally undoped InGaN material. The In content of the multilayer second InGaN layer is X2, which increases from 0.05 to 0.21 along the epitaxial direction. The growth thickness is 3.3 nm, the growth temperature is 800 °C, and the growth pressure is 250 torr.

[0053] Example 4 The difference between this embodiment and Embodiment 1 is that: The second barrier layer comprises a second Si-doped GaN layer one, a second AlGaN layer two, and a second Si-doped GaN layer three; the Si doping concentration of the second Si-doped GaN layer one and the second Si-doped GaN layer three is 5.7 × 10⁻⁶. 17 The growth thickness is 4.3 nm, with an average density of 1 / cm³. The second AlGaN layer is undoped with Si, has an Al content of Y2=0.3, and a growth thickness of 4.5 nm. The growth temperature of the second Si-doped GaN layer one, the second AlGaN layer two, and the third Si-doped GaN layer three is 875℃, and the growth pressure is 250 torr.

[0054] Comparative Example 1 An LED epitaxial wafer is provided, comprising a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer sequentially stacked along the epitaxial direction; The multi-quantum-well light-emitting layer has a periodic structure of alternating InGaN multi-quantum-well layers and GaN quantum barrier layers, with a stacking period of 8. Within a single period, the InGaN quantum well layer has an In composition of 0.17, and the thickness of the InGaN quantum well layer is 3.4 nm; the thickness of the GaN quantum barrier layer is 13 nm.

[0055] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: No non-luminescent superlattice layer or non-luminescent quantum well layer is set.

[0056] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: No non-luminescent superlattice layer is set.

[0057] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: No non-light-emitting quantum well layer is set.

[0058] Comparative Example 5 The difference between this comparative example and Example 1 is as follows: The first InGaN layer is made of intentionally undoped InGaN material with an In content of X1=0.1. The second InGaN layer is made of intentionally undoped InGaN material, and the In composition content of the multilayer second InGaN layer increases from 0.05 to 0.28 along the epitaxial direction by X2.

[0059] The epitaxial wafers obtained in the examples and comparative examples were fabricated into 20μm×20μm LED chips, and subjected to 20A / cm 2 The chip's luminous efficacy improvement, WD STD (nm) and epitaxial wafer XRD test results were obtained under the working current density. The luminous efficacy improvement was calculated based on Comparative Example 1.

[0060] It should be noted that arcsec(002) data can characterize screw dislocations, while arcsec(102) data can characterize mixed dislocations of screw and edge dislocations. The smaller the value of arcsec(002) or arcsec(102), the lower the dislocation density and the better the crystal quality. WD STD mainly reflects the wavelength standard deviation. The smaller the standard deviation, the more concentrated the chip parameter distribution and the more stable the manufacturing process.

[0061] It should be noted that the color rendering index (CRI) is a metric established by the International Commission on Illumination (ICI) to evaluate the color rendering performance of light sources. It measures the ability of a light source to reproduce the colors of objects. Its core principle is to quantify color rendering performance by comparing the color difference between the tested light source and a standard color sample under a reference light source.

[0062] Evaluation criteria: Ra≥80: Good color rendering, meeting general lighting needs; Ra≥95: Excellent color rendering, close to the effect of natural light; Ra<70: Poor color rendering, which may lead to color distortion.

[0063] The fidelity index is a light source color quality evaluation index proposed by the Illuminating Engineering Society of North America in the TM-30-15 standard. It is specifically used to evaluate the degree to which a light source reproduces the true colors of an object.

[0064] Evaluation criteria: Rf≥80: Good fidelity; Rf≥95: Excellent fidelity; Rf<70: Insufficient fidelity, obvious color distortion.

[0065] The test results are as follows:

[0066] The test results above show that the multi-quantum-well light-emitting layer of the present invention includes a non-light-emitting superlattice layer, a non-light-emitting quantum well layer, a green quantum well layer, and a blue quantum well layer, which are periodically and alternately grown along the epitaxial direction. That is, this multi-quantum-well light-emitting layer can excite two different LED light sources, one in a green wavelength band and the other in a blue wavelength band, thereby reducing the cost of RGB-LED backlight sources and reducing the use of phosphors in white LED backlight sources.

[0067] In this invention, the In content of the non-emitting superlattice layer, non-emitting quantum well layer, green quantum well layer, and blue quantum well layer exhibits a trend of first increasing and then decreasing. This effectively reduces the lattice mismatch stress between the quantum well InGaN material and the barrier layer material, thereby reducing defects caused by lattice mismatch stress and significantly improving the quality of the multiple quantum well layers. This is beneficial for improving the radiative recombination efficiency of the active region, thus enhancing the luminous efficacy and yield of blue-green LED light sources.

[0068] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A blue-green dual-band LED epitaxial wafer, comprising a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer sequentially disposed along the epitaxial direction, characterized in that: The multi-quantum-well light-emitting layer includes a non-light-emitting superlattice layer, a non-light-emitting quantum well layer, a green light quantum well layer, and a blue light quantum well layer that are periodically and alternately grown along the epitaxial direction. The non-luminescent superlattice layer comprises a superlattice structure in which a first InGaN layer and a first barrier layer are grown alternately and periodically along the epitaxial direction. The non-light-emitting quantum well layer comprises a superlattice structure of a second InGaN layer and a second barrier layer that are periodically and alternately grown along the epitaxial direction, and the In content of the multiple second InGaN layers increases sequentially along the epitaxial direction. The green quantum well layer comprises a superlattice structure consisting of a green InGaN layer and a third barrier layer that are periodically and alternately grown along the epitaxial direction. The blue quantum well layer comprises a superlattice structure consisting of a blue InGaN layer and a fourth barrier layer that are periodically and alternately grown along the epitaxial direction. Wherein, the In composition content of the second InGaN layer in the first growth cycle of the non-light-emitting region quantum well layer is greater than the In composition content of the first InGaN layer in the non-light-emitting region superlattice layer; The In content of the second InGaN layer in the last growth cycle of the non-luminescent quantum well layer is less than the In content of the green InGaN layer in the green quantum well layer.

2. The blue-green dual-band LED epitaxial wafer as described in claim 1, characterized in that, The growth cycle number of the multi-quantum-well light-emitting layer is 3 to 17; the growth cycle number of the non-light-emitting superlattice layer is 2 to 10; the growth cycle number of the non-light-emitting quantum well layer is 2 to 6; the growth cycle number of the green quantum well layer is 2 to 6; and the growth cycle number of the blue quantum well layer is 2 to 8.

3. The blue-green dual-band LED epitaxial wafer as described in claim 1, characterized in that, The first InGaN layer is made of intentionally undoped InGaN material, with an In content of X1, 0.002≤X1<0.05, and a growth thickness of 0.1nm~2nm; The first barrier layer includes a first Si-doped GaN layer with a Si doping concentration of 1.28 × 10⁻⁶. 17 / cm³~9.73×10 17 / cm³, with a growth thickness of 0.1nm~2nm; The second InGaN layer is made of intentionally undoped InGaN material with an In content of X2, 0.05≤X2<0.22, and a growth thickness of 2.1nm~4.5nm.

4. The blue-green dual-band LED epitaxial wafer as described in claim 3, characterized in that, The second barrier layer comprises a second Si-doped GaN layer one, a second AlGaN layer two, and a second Si-doped GaN layer three; the Si doping concentration of the second Si-doped GaN layer one and the second Si-doped GaN layer three is 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 1.8nm~6.8nm; the second AlGaN layer is not intentionally doped with Si, the Al composition content is Y2, 0.02≤Y2≤0.36, and the growth thickness is 1.0nm~5.8nm.

5. The blue-green dual-band LED epitaxial wafer as described in claim 1, characterized in that, The In content of the second InGaN layer increases linearly along the epitaxial direction; wherein the difference between the maximum and minimum values ​​of the In content of the second InGaN layer is ≤0.

1.

6. The blue-green dual-band LED epitaxial wafer as described in claim 1 or 5, characterized in that, The green InGaN layer is made of intentionally undoped InGaN material with an In content of X3, 0.22≤X3≤0.28, and a growth thickness of 2.1nm~4.6nm. The third barrier layer includes a third Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm; The blue light InGaN layer is made of intentionally undoped InGaN material with an In content of X4, 0.08≤X4≤0.19, and a growth thickness of 2.1nm~4.8nm; The fourth barrier layer includes a fourth Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm.

7. A method for fabricating a blue-green dual-band LED epitaxial wafer as described in any one of claims 1 to 6, characterized in that, include: Provide a substrate; A buffer layer is grown on the substrate; An N-type semiconductor layer is grown on the buffer layer; A low-temperature stress relief layer is grown on an N-type semiconductor layer; A multi-quantum-well light-emitting layer is grown on a low-temperature stress-relieving layer; An electron blocking layer is grown on a multi-quantum-well light-emitting layer; A P-type semiconductor layer is grown on an electron blocking layer; The multi-quantum-well light-emitting layer includes a non-light-emitting superlattice layer, a non-light-emitting quantum well layer, a green light quantum well layer, and a blue light quantum well layer that are periodically and alternately grown along the epitaxial direction. The non-luminescent superlattice layer comprises a superlattice structure in which a first InGaN layer and a first barrier layer are grown alternately and periodically along the epitaxial direction. The non-light-emitting quantum well layer comprises a superlattice structure of a second InGaN layer and a second barrier layer that are periodically and alternately grown along the epitaxial direction, and the In content of the multiple second InGaN layers increases sequentially along the epitaxial direction. The green quantum well layer comprises a superlattice structure consisting of a green InGaN layer and a third barrier layer that are periodically and alternately grown along the epitaxial direction. The blue quantum well layer comprises a superlattice structure consisting of a blue InGaN layer and a fourth barrier layer that are periodically and alternately grown along the epitaxial direction. Wherein, the In composition content of the second InGaN layer in the first growth cycle of the non-light-emitting region quantum well layer is greater than the In composition content of the first InGaN layer in the non-light-emitting region superlattice layer; The In content of the second InGaN layer in the last growth cycle of the non-luminescent quantum well layer is less than the In content of the green InGaN layer in the green quantum well layer.

8. The method for preparing a blue-green dual-band LED epitaxial wafer as described in claim 7, characterized in that, The growth cycle number of the multi-quantum-well light-emitting layer is 3 to 17; the growth cycle number of the non-light-emitting superlattice layer is 2 to 10; the growth cycle number of the non-light-emitting quantum well layer is 2 to 6; the growth cycle number of the green quantum well layer is 2 to 6; and the growth cycle number of the blue quantum well layer is 2 to 8.

9. The method for preparing a blue-green dual-band LED epitaxial wafer as described in claim 7, characterized in that, The first InGaN layer is made of intentionally undoped InGaN material, with an In content of X1, 0.002≤X1<0.05, and a growth thickness of 0.1nm~2nm; the growth temperature of the first InGaN layer is 700℃~980℃, and the growth pressure is 30torr~360torr. The first barrier layer includes a first Si-doped GaN layer with a Si doping concentration of 1.28 × 10⁻⁶. 17 / cm³~9.73×10 17 / cm³, with a growth thickness of 0.1nm~2nm; the growth temperature of the first barrier layer is 700℃~980℃, and the growth pressure is 30torr~360torr; The second InGaN layer is made of intentionally undoped InGaN material with an In content of X2, 0.05≤X2<0.22, and a growth thickness of 2.1nm~4.5nm; the growth temperature of the second InGaN layer is 680℃~920℃, and the growth pressure is 30torr~360torr. The second barrier layer comprises a second Si-doped GaN layer one, a second AlGaN layer two, and a second Si-doped GaN layer three; the Si doping concentration of the second Si-doped GaN layer one and the second Si-doped GaN layer three is 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 The growth thickness is 1.8 nm to 6.8 nm. The second AlGaN layer is not intentionally doped with Si, and the Al composition is Y2, 0.02 ≤ Y2 ≤ 0.36, with a growth thickness of 1.0 nm to 5.8 nm. The growth temperature of the second Si-doped GaN layer one, the second AlGaN layer two, and the third Si-doped GaN layer three is 800℃ to 950℃, and the growth pressure is 30 torr to 360 torr.

10. The method for preparing a blue-green dual-band LED epitaxial wafer as described in claim 7, characterized in that, The green InGaN layer is made of intentionally undoped InGaN material with an In content of X3, 0.22≤X3≤0.28, and a growth thickness of 2.1nm~4.6nm; the growth temperature of the green InGaN layer is 680℃~920℃, and the growth pressure is 30torr~360torr. The third barrier layer includes a third Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm; the growth temperature of the third barrier layer is 800℃~950℃, and the growth pressure is 30torr~360torr; The blue light InGaN layer is made of intentionally undoped InGaN material with an In content of X4, 0.08≤X4≤0.19, and a growth thickness of 2.1nm~4.8nm; the growth temperature of the blue light InGaN layer is 720℃~920℃, and the growth pressure is 30torr~360torr. The fourth barrier layer includes a fourth Si-doped GaN layer with a Si doping concentration of 1.8 × 10⁻⁶. 17 / cm³~9.6×10 17 / cm³, with a growth thickness of 5nm~15nm; the growth temperature of the fourth barrier layer is 800℃~950℃, and the pressure is 30torr~360torr.

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