Blue-green led epitaxial wafer and method of manufacturing the same

Abstract

The present application relates to a kind of blue-green LED epitaxial wafer and its preparation method, and the multiple quantum well light-emitting layer of blue-green LED epitaxial wafer includes gradually changing InGaN layer before well, first blue light InGaN layer, first AlGaInN interface protection layer, green light InGaN layer, second AlGaInN interface protection layer, second blue light InGaN layer, gradually changing InGaN layer after well, quantum barrier layer, and gradually changing InGaN layer before well includes multiple first InGaN layer of sequentially stacked, the In component content of multiple first InGaN layer is sequentially increased along the direction of epitaxy;Gradually changing InGaN layer after well includes multiple second InGaN layer of sequentially stacked, the In component content of multiple second InGaN layer is sequentially decreased along the direction of epitaxy. Wherein, N2 atmosphere heat treatment is needed before depositing first AlGaInN interface protection layer, and before depositing second AlGaInN interface protection layer. The present application can effectively reduce the preparation cost of LED backlight light source, active region has good recombination efficiency, and LED chip light uniformity is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a blue-green LED epitaxial wafer and a preparation method thereof. BACKGROUND

[0002] Light Emitting Diode, abbreviated as LED, as a new energy-saving and environment-friendly light source, has attracted great attention in recent years, and many countries regard semiconductor lighting related to LED as a strategic technology.

[0003] The LED backlight light source applied to the display screen has two kinds of RGB LED and white light LED. Among them, the RGB LED is packaged with three single-color LED chips of blue, green and red, and the white light LED is formed by combining single-color LED chips with fluorescent powder. For example, single-color blue chip is combined with green and red fluorescent powder, or single blue LED chip is combined with yellow fluorescent powder.

[0004] The display effect of RGB three-primary color LED backlight light source is the best, but the cost is higher, and the white light LED needs to use fluorescent powder. However, different fluorescent powder schemes have obvious differences in color gamut, and the uniformity of the mixture of fluorescent powder and glue is also difficult to control, resulting in poor light output uniformity, poor color consistency, easy deviation of color temperature and not ideal color rendering. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art, and provides a blue-green LED epitaxial wafer and a preparation method thereof, which can effectively reduce the preparation cost of the LED backlight light source, the active region has good recombination efficiency, and the light output uniformity of the LED chip is good.

[0006] In order to solve the above problems, the present application provides a blue-green 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 arranged in sequence along the epitaxial direction:

[0007] The multi-quantum well light emitting layer comprises a well front gradual change InGaN layer, a first blue light InGaN layer, a first AlGaInN interface protection layer, a green light InGaN layer, a second AlGaInN interface protection layer, a second blue light InGaN layer, a well back gradual change InGaN layer and a quantum barrier layer which are periodically and alternately grown in sequence along the epitaxial direction;

[0008] The well front gradual change InGaN layer comprises a plurality of first InGaN layers which are stacked in sequence, and the In content of the plurality of first InGaN layers increases in sequence along the epitaxial direction;

[0009] The post-well gradual InGaN layer comprises a plurality of second InGaN layers stacked in sequence, and the In content of the plurality of second InGaN layers gradually decreases along the epitaxial direction in sequence;

[0010] The N2 atmosphere heat treatment is required before depositing the first AlGaInN interface protection layer and before depositing the second AlGaInN interface protection layer.

[0011] As an improvement of the above technical solution, the growth cycle number of the multi-quantum well light-emitting layer is 3-17.

[0012] The first blue light InGaN layer has a light-emitting wavelength of 391-487 nm.

[0013] The green light InGaN layer has a light-emitting wavelength of 511-565 nm.

[0014] The second blue light InGaN layer has a light-emitting wavelength of 391-487 nm.

[0015] As an improvement of the above technical solution, the growth thickness of the pre-well gradual InGaN layer is 0.03-1.0 nm.

[0016] The pre-well gradual InGaN layer is an InGaN material doped with Si elements, the Si doping concentration is 1.12*10 17 / cm³-7.89*10 17 / cm³, the In content is X1, and X1≤0.19.

[0017] The growth thickness of the post-well gradual InGaN layer is 0.03-1.0 nm.

[0018] The post-well gradual InGaN layer is an InGaN material doped with Si elements, the Si doping concentration is 1.12*10 17 / cm³-7.89*10 17 / cm³, the In content is X5, and X5≤0.19.

[0019] As an improvement of the above technical solution, after depositing the first blue light InGaN layer and before depositing the first AlGaInN interface protection layer, the method further comprises: heat treatment in an N2 atmosphere, the treatment time is t1, 8s≤t1≤180s, and the treatment temperature is W1, 810℃≤W1≤1050℃.

[0020] After depositing the green InGaN layer and before depositing the second AlGaInN interface protection layer, further comprising: heat treatment in a N2 atmosphere, a treatment time of t2, 6s≤t2≤150s, and a treatment temperature of W2, 800℃≤W2≤1030℃;

[0021] The growth thickness of the first AlGaInN interface protection layer and the second AlGaInN interface protection layer is 0.01nm~0.3nm; the In component content of the first AlGaInN interface protection layer is X 01 , X 01 ≤0.09, and the Al component content is Y 01 , Y 01 ≤0.09; the In component content of the second AlGaInN interface protection layer is X 02 , X 02 ≤0.09, and the Al component content is Y 02 , Y 02 ≤0.09.

[0022] As an improvement of the above technical solution, t1>t2, and W1>W2.

[0023] As an improvement of the above technical solution, the first blue InGaN layer is made of intentionally undoped InGaN material, the In component content of which is X2, 0.05≤X2≤0.19, and the growth thickness is 0.3nm~2.6nm;

[0024] The green InGaN layer is made of intentionally undoped InGaN material, the In component content of which is X3, 0.22≤X3≤0.28, and the growth thickness is 0.3nm~2.6nm;

[0025] The second blue InGaN layer is made of intentionally undoped InGaN material, the In component content of which is X4, 0.05≤X4≤0.19, and the growth thickness is 0.3nm~2.6nm;

[0026] The quantum barrier layer comprises a GaN layer and / or an AlGaN layer, and the growth thickness of the quantum barrier layer is 5nm~16nm;

[0027] The GaN layer is doped with Si element, and the Si doping concentration is 1.6×10 17 / cm³~9.8×10 17 / cm³;

[0028] The Al component content of the AlGaN layer is Y6, Y6≤0.5.

[0029] As the improvement of the above technical scheme, the In content of the first blue light InGaN layer, the green light InGaN layer and the second blue light InGaN layer is X3>X2=X4.

[0030] Correspondingly, the application also provides a preparation method of the blue-green LED epitaxial wafer, comprising the following steps:

[0031] providing a substrate;

[0032] depositing a buffer layer on the substrate;

[0033] depositing an N-type semiconductor layer on the buffer layer;

[0034] depositing a low-temperature stress release layer on the N-type semiconductor layer;

[0035] depositing a multi-quantum well light-emitting layer on the low-temperature stress release layer;

[0036] depositing an electron blocking layer on the multi-quantum well light-emitting layer;

[0037] depositing a P-type semiconductor layer on the electron blocking layer;

[0038] The multi-quantum well light-emitting layer comprises, in sequence along the epitaxial direction, a well-front gradual change InGaN layer, a first blue light InGaN layer, a first AlGaInN interface protection layer, a green light InGaN layer, a second AlGaInN interface protection layer, a second blue light InGaN layer, a well-back gradual change InGaN layer and a quantum barrier layer.

[0039] The well-front gradual change InGaN layer comprises a plurality of first InGaN layers stacked in sequence, and the In content of the plurality of first InGaN layers increases in sequence along the epitaxial direction.

[0040] The well-back gradual change InGaN layer comprises a plurality of second InGaN layers stacked in sequence, and the In content of the plurality of second InGaN layers decreases in sequence along the epitaxial direction.

[0041] Before depositing the first AlGaInN interface protection layer and before depositing the second AlGaInN interface protection layer, N2 atmosphere heat treatment is required.

[0042] As the improvement of the above technical scheme, the growth cycle number of the multi-quantum well light-emitting layer is 3-17.

[0043] The light-emitting wavelength of the first blue light InGaN layer is 391-487 nm.

[0044] The light-emitting wavelength of the green light InGaN layer is 511-565 nm.

[0045] The emission wavelength of the second blue InGaN layer is 391nm~487nm.

[0046] As an improvement to the above technical solution, after depositing the first blue InGaN layer and before depositing the first AlGaInN interface protective layer, the process further includes: heat treatment in an N2 atmosphere, with a treatment time of t1, 8s≤t1≤180s, and a treatment temperature of W1, 810℃≤W1≤1050℃.

[0047] After depositing the green InGaN layer and before depositing the second AlGaInN interface protective layer, the process further includes: heat treatment in N2 atmosphere, with a treatment time of t2, 6s≤t2≤150s, and a treatment temperature of W2, 800℃≤W2≤1030℃.

[0048] The growth thickness of both the first AlGaInN interface protective layer and the second AlGaInN interface protective layer is 0.01 nm to 0.3 nm; the In content of the first AlGaInN interface protective layer is X. 01 X 01 ≤0.09, Al component content is Y 01 Y 01 ≤0.09; The In content of the second AlGaInN interface protective layer is X 02 X 02 ≤0.09, Al component content is Y 02 Y 02 ≤0.09.

[0049] The implementation of this invention has the following beneficial effects:

[0050] (1) The present invention provides a blue-green LED epitaxial wafer, wherein the multi-quantum-well light-emitting layer comprises, sequentially and periodically alternatingly grown along the epitaxial direction, a pre-well gradient InGaN layer, a first blue InGaN layer, a first AlGaInN interface protection layer, a green InGaN layer, a second AlGaInN interface protection layer, a second blue InGaN layer, a post-well gradient InGaN layer, and a quantum barrier layer. A single LED chip can emit blue and green light, thereby reducing the use of phosphors in white LED backlight sources.

[0051] (2) The pre-well gradual change InGaN layer comprises a plurality of first InGaN layers which are sequentially stacked, and the In content of the plurality of first InGaN layers gradually increases along the epitaxial direction; the post-well gradual change InGaN layer comprises a plurality of second InGaN layers which are sequentially stacked, and the In content of the plurality of second InGaN layers gradually decreases along the epitaxial direction. The gradient change of the In content has the advantage of improving the quality of the multi-quantum well light-emitting layer. Further, the In content relationship of the first blue light InGaN layer, the green light InGaN layer and the second blue light InGaN layer is X3>X2=X4. The structure and process design can effectively reduce the lattice mismatch stress between the quantum well InGaN material and the barrier layer material, can significantly improve the quality of the multi-quantum well light-emitting layer, is conducive to improving the radiation recombination efficiency of the active region, and thus improves the luminous efficiency and yield performance of the blue-green LED light source; meanwhile, the lattice mismatch stress between the quantum well InGaN material and the barrier layer material is reduced, the band bending phenomenon of the quantum well InGaN material due to the piezoelectric polarization effect is reduced, the coupling degree between the electron and hole wave functions in the quantum well InGaN material is improved, the radiation recombination efficiency in the multi-quantum well light-emitting layer is improved, and finally the light-emitting efficiency of the blue-green LED chip is improved.

[0052] (3) The first AlGaInN interface protection layer is deposited between the first blue light InGaN layer and the green light InGaN layer, and the second AlGaInN interface protection layer is deposited between the green light InGaN layer and the second blue light InGaN layer. The dense AlGaInN thin film material separates the quantum well layer InGaN materials, can reduce the roughness between the interfaces of the quantum well layer InGaN materials, makes the interfaces of the quantum well layer InGaN materials more flat and reduces the defect density of the quantum well layer InGaN materials. Meanwhile, the band gap of the Al atom is higher, the energy band of the interface protection layer AlGaInN material can effectively separate the energy band of the quantum well layer InGaN material, the electron-hole in each quantum well layer InGaN material occurs radiation recombination light emission and does not interfere with each other, and thus the uniformity and light efficiency of the blue-green LED chip are improved. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is a structure schematic diagram of a blue-green LED epitaxial wafer according to an embodiment of the present application;

[0054] Figure 2 is a structure schematic diagram of a multi-quantum well light-emitting layer according to an embodiment of the present application. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings.

[0056] Referring toFigure 1 and Figure 2 As shown in the figure, the embodiment of the present application provides a blue-green LED epitaxial wafer, which comprises, in sequence along the epitaxial direction, a substrate 100, a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress release layer 400, a multi-quantum well light-emitting layer 500, an electron blocking layer 600 and a P-type semiconductor layer 700.

[0057] In the above structure, the substrate 100 can be a sapphire substrate. The sapphire substrate is the most commonly used substrate material at present, and has the advantages of mature preparation process, low price, easy cleaning and processing, and good stability at high temperature. The buffer layer 200 can be a GaN buffer layer, an AlN buffer layer, or a SiN buffer layer, etc. The main function is to relieve the lattice mismatch and thermal mismatch between the substrate 100 and the epitaxial layer, so as to improve the crystal quality of the epitaxial layer and enhance the performance and reliability of the chip. The N-type semiconductor layer 300 can be an N-type GaN layer doped with Si. The low-temperature stress release layer 400 can be a low-temperature GaN layer, a low-temperature InGaN layer, etc., which is used to relieve the stress generated in the chip manufacturing process. The electron blocking layer 600 can be an AlGaN layer, an AlInGaN layer, etc., and the P-type semiconductor layer 700 is usually a Mg-doped GaN layer.

[0058] In order to realize that a single chip can excite blue and green two kinds of waveband light sources, the structure of the multi-quantum well light-emitting layer 500 is improved in the embodiment of the present application.

[0059] Specifically, the multi-quantum well light-emitting layer 500 comprises, in sequence along the epitaxial direction, a well front gradual change InGaN layer 510, a first blue light InGaN layer 520, a first AlGaInN interface protection layer 570, a green light InGaN layer 530, a second AlGaInN interface protection layer 580, a second blue light InGaN layer 540, a well back gradual change InGaN layer 550, and a quantum barrier layer 560, which are periodically and alternately grown. The period number is 3-17. The period number is exemplarily 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17.

[0060] Preferably, the light-emitting wavelength of the first blue light InGaN layer 520 is 391-487 nm.

[0061] The light-emitting wavelength of the green light InGaN layer 530 is 511-565 nm.

[0062] The light-emitting wavelength of the second blue light InGaN layer 540 is 391-487 nm.

[0063] The multi-quantum well light-emitting layer 500 contains a first blue InGaN layer 520, a green InGaN layer 530, and a second blue InGaN layer 540. This means that a single LED chip can emit both blue and green light, thereby reducing the amount of phosphor used in white LED backlight sources.

[0064] Preferably, the pre-well gradient InGaN layer 510 includes multiple layers of first InGaN layers stacked sequentially, wherein the In content of the multiple layers of first InGaN layers increases sequentially along the epitaxial direction.

[0065] The growth thickness of the gradient InGaN layer 510 before the well is 0.03nm to 1.0nm; the exemplary growth thicknesses are 0.03nm, 0.05nm, 0.09nm, 0.1nm, 0.3nm, 0.7nm, and 0.9nm, but are not limited thereto.

[0066] It should be noted that the above-mentioned growth thickness is the overall thickness of the in-well gradient InGaN layer 510, which is the sum of the growth thicknesses of the multiple first InGaN layers.

[0067] Preferably, the gradient InGaN layer 510 before the well is an InGaN material doped with Si, and the Si doping concentration is 1.12 × 10⁻⁶. 17 / cm³~7.89×10 17 / cm³, its In composition content is X1, X1≤0.19. An exemplary Si doping concentration is 1.12×10⁻⁶. 17 / cm³, 1.57×10 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. Examples of X1 are 0.01, 0.05, 0.07, 0.09, 0.10, 0.13, 0.15, 0.19, but not limited to.

[0068] The In composition content of the gradient InGaN layer 510 before the well is X1, which increases linearly along the epitaxial direction and has a maximum value of 0.19.

[0069] The growth temperature of the pre-well graded InGaN layer 510 is 730-925 °C, and the growth pressure is 30-360 torr. The growth temperature is exemplarily 730 °C, 750 °C, 770 °C, 790 °C, 810 °C, 820 °C, 845 °C, 863 °C, 875 °C, 901 °C, 923 °C, but is not limited thereto. The growth pressure is exemplarily 30 torr, 50 torr, 70 torr, 100 torr, 150 torr, 180 torr, 220 torr, 250 torr, 280 torr, 310 torr, 330 torr, 350 torr, 360 torr, but is not limited thereto.

[0070] Preferably, the first blue light InGaN layer 520 is made of intentionally undoped InGaN material with an In content of X2, 0.05≤X2≤0.19, and a growth thickness of 0.3-2.6 nm. X2 is exemplarily 0.05, 0.08, 0.11, 0.15, 0.19, but is not limited thereto. The growth thickness is exemplarily 0.3 nm, 0.5 nm, 0.9 nm, 1.5 nm, 2.1 nm, 2.3 nm, 2.5 nm, 2.6 nm, but is not limited thereto.

[0071] The growth temperature of the first blue light InGaN layer 520 is 730-880 °C, and the growth pressure is 30-360 torr. The growth temperature is exemplarily 760 °C, 770 °C, 780 °C, 790 °C, 810 °C, 850 °C, 880 °C, but is not limited thereto. The growth pressure is exemplarily 30 torr, 50 torr, 70 torr, 100 torr, 150 torr, 180 torr, 220 torr, 250 torr, 280 torr, 310 torr, 330 torr, 350 torr, 360 torr, but is not limited thereto.

[0072] Preferably, the green light InGaN layer 530 is made of intentionally undoped InGaN material with an In content of X3, 0.22≤X3≤0.28, and a growth thickness of 0.3-2.6 nm. X3 is exemplarily 0.22, 0.25, 0.26, 0.27, 0.28, but is not limited thereto. The growth thickness is exemplarily 0.3 nm, 0.5 nm, 0.9 nm, 1.1 nm, 1.2 nm, 1.5 nm, 1.9 nm, 2.1 nm, 2.3 nm, 2.6 nm, but is not limited thereto.

[0073] The growth temperature of the green InGaN layer 530 is 680-880 °C, and the growth pressure is 30-360 torr. The growth temperature is exemplarily 680 °C, 690 °C, 710 °C, 720 °C, 756 °C, 786 °C, 810 °C, 863 °C, 880 °C, but is not limited thereto. The growth pressure is exemplarily 30 torr, 50 torr, 70 torr, 100 torr, 150 torr, 180 torr, 220 torr, 250 torr, 280 torr, 310 torr, 330 torr, 350 torr, 360 torr, but is not limited thereto.

[0074] Preferably, the second blue InGaN layer 540 is made of intentionally undoped InGaN material with an In content of X4, 0.05≤X4≤0.19, and a growth thickness of 0.3-2.6 nm. X4 is exemplarily 0.05, 0.06, 0.08, 0.11, 0.15, 0.17, 0.19, but is not limited thereto. The growth thickness is exemplarily 0.3 nm, 0.5 nm, 0.7 nm, 0.9 nm, 1.1 nm, 1.3 nm, 1.5 nm, 1.7 nm, 1.9 nm, 2.1 nm, 2.2 nm, 2.5 nm, 2.6 nm, but is not limited thereto.

[0075] The growth temperature of the second blue InGaN layer 540 is 730-880 °C, and the growth pressure is 30-360 torr. The growth temperature is exemplarily 756 °C, 786 °C, 810 °C, 863 °C, 880 °C, but is not limited thereto. The growth pressure is exemplarily 30 torr, 50 torr, 70 torr, 100 torr, 150 torr, 180 torr, 220 torr, 250 torr, 280 torr, 310 torr, 330 torr, 350 torr, 360 torr, but is not limited thereto.

[0076] In addition, N2 atmosphere heat treatment is required before depositing the first AlGaInN interface protection layer 570 and before depositing the second AlGaInN interface protection layer 580.

[0077] Specifically, after depositing the first blue light InGaN layer 520 and before depositing the first AlGaInN interface protection layer 570, further comprising: heat treatment in N2 atmosphere, treatment time t1, 8s≤t1≤180s, treatment temperature W1, 810℃≤W1≤1050℃. t1 is exemplarily 8s, 15s, 30s, 50s, 75s, 100s, 150s, 180s, but is not limited thereto. W1 is exemplarily 810℃, 830℃, 850℃, 880℃, 900℃, 950℃, 980℃, 1000℃, 1050℃, but is not limited thereto.

[0078] After depositing the green light InGaN layer 530 and before depositing the second AlGaInN interface protection layer 580, further comprising: heat treatment in N2 atmosphere, treatment time t2, 6s≤t2≤150s, treatment temperature W2, 800℃≤W2≤1030℃. t2 is exemplarily 6s, 15s, 30s, 50s, 75s, 100s, 150s, but is not limited thereto. W2 is exemplarily 810℃, 830℃, 850℃, 880℃, 900℃, 950℃, 980℃, 1000℃, 1030℃, but is not limited thereto. More preferably, t1>t2, W1>W2.

[0079] The growth thickness of the first AlGaInN interface protection layer 570 and the second AlGaInN interface protection layer 580 is 0.01nm-0.3nm; the In component content of the first AlGaInN interface protection layer 570 is X 01 , X 01 ≤0.09, and the Al component content is Y 01 , Y 01 ≤0.09. X 01 is exemplarily 0.01, 0.03, 0.05, 0.06, 0.07, 0.09, but is not limited thereto. Y 01 is exemplarily 0.01, 0.03, 0.05, 0.09, but is not limited thereto. The In component content of the second AlGaInN interface protection layer 580 is X 02 , X 02 ≤0.09, and the Al component content is Y 02 , Y 02 ≤0.09. X 02 is exemplarily 0.01, 0.03, 0.05, 0.06, 0.07, 0.09, but is not limited thereto. Y 02 is exemplarily 0.01, 0.03, 0.05, 0.09, but is not limited thereto.

[0080] The traditional quantum well layer interface has a large roughness, which affects the flatness of the material interface. The quantum well layer InGaN material has a high defect density. The energy bands between the quantum well layers lack effective isolation, which causes the electron-hole recombination luminescence to interfere with each other.

[0081] After N2 atmosphere heat treatment, the InGaN layer surface crystalline quality poor part and high In component In cluster and other defects can be decomposed, which is beneficial to improve the crystal quality of the material, and at the same time, the surface of the material is micro-rough, which can reduce the in-plane total reflection of photons in the semiconductor material and light absorption loss, and improve the light efficiency.

[0082] The dense AlGaInN thin film material separates the quantum well layer InGaN material, which can reduce the roughness between the quantum well layer InGaN material interfaces, make the quantum well layer InGaN material interface more flat and reduce the defect density of the quantum well layer InGaN material. At the same time, the band gap of Al atom is higher, and the energy band of the interface protection layer AlGaInN material can separate the energy band of the quantum well layer InGaN material, so that the electron-hole recombination luminescence in each quantum well layer InGaN material does not interfere with each other, thereby improving the uniformity and light efficiency of the blue-green LED chip.

[0083] Preferably, the growth thickness of the InGaN layer 550 is 0.03nm-1.0nm. The growth thickness is exemplarily 0.03nm, 0.05nm, 0.07nm, 0.15nm, 0.27nm, 0.34nm, 0.77nm, 0.85nm, 0.96nm, but is not limited thereto.

[0084] It should be noted that the above growth thickness is the overall thickness of the InGaN layer 550, that is, the sum of the growth thicknesses of the plurality of second InGaN layers.

[0085] The InGaN layer 550 is an InGaN material doped with Si elements, and the Si doping concentration is 1.12×10 17 / cm³-7.89×10 17 / cm³, and the In component content is X5, X5≤0.19. The Si doping concentration is exemplarily 1.12×10 17 / cm³, 1.58×10 17 / cm³, 1.96×10 17 / cm³, 2.63×10 17 / cm³, 2.96×10 17 / cm³, 3.67×10 17 / cm³, 4.69×10 17 / cm³, 5.39×1017 / cm3, 6.33 x 1019 / cm3 17 / cm3, 7.68 x 1019 / cm3 17 / cm3, but not limited to this.

[0086] Preferably, the In composition content of the well-after graded InGaN layer 550 is X5, X5 decreases linearly along the epitaxial direction, and the maximum value can be 0.19.

[0087] The growth temperature of the well-after graded InGaN layer 550 is 730-925℃, and the growth pressure is 30-360torr. The growth temperature is exemplarily 730℃, 740℃, 750℃, 780℃, 790℃, 805℃, 845℃, 880℃, 890℃, 905℃, 925℃, but not limited to this. The growth pressure is exemplarily 30torr, 50torr, 70torr, 100torr, 150torr, 180torr, 220torr, 250torr, 280torr, 310torr, 330torr, 350torr, 360torr, but not limited to this.

[0088] In the conventional quantum well structure, there is a significant difference in lattice constant between the InGaN material and the GaN / AlGaN barrier layer, which causes a high density of dislocation defects at the interface, reducing the light-emitting efficiency. Stress-induced piezoelectric polarization will cause the quantum well band to tilt, weaken the electron-hole wave function overlap, and reduce the radiation recombination probability.

[0089] The In composition content of the well-before graded InGaN layer 510 and the well-after graded InGaN layer 550 is a gradient design, the In composition content changes linearly along the epitaxial direction, forming a "low-high-low" In composition content transition structure, gradually buffering the lattice mismatch between InGaN and the barrier layer, allowing stress to be dispersed and released in the multilayer structure, significantly reducing the threading dislocation density. By adjusting the band slope through the graded layer, the band bending caused by piezoelectric polarization is offset, making the quantum well band tend to be flat. The gradually changing band formed by the graded layer can serve as a carrier transport channel, promoting the injection of electrons and holes into the quantum well active region, and reducing non-radiative recombination loss.

[0090] In particular, the In composition content relationship of the first blue light InGaN layer 520, the green light InGaN layer 530, and the second blue light InGaN layer 540 is X3>X2=X4.

[0091] The structure and process design can reduce the lattice mismatch stress between the quantum well InGaN material and the barrier layer material, significantly improve the quality of the multi-quantum well light emitting layer 500, and be beneficial to improve the radiation recombination efficiency of the active region, thereby improving the light efficiency, yield and other performances of the blue-green LED light source; at the same time, the lattice mismatch stress between the quantum well InGaN material and the barrier layer material is reduced, the band bending phenomenon of the quantum well InGaN material due to the piezoelectric polarization effect is reduced, thereby improving the coupling degree between the electron and hole wave functions in the quantum well InGaN material, to improve the radiation recombination efficiency in the multi-quantum well light emitting layer 500 and finally improve the light emitting efficiency of the blue-green LED chip.

[0092] The application further provides a preparation method of a blue-green LED epitaxial wafer, comprising the following steps:

[0093] providing a substrate 100;

[0094] depositing a buffer layer 200 on the substrate 100;

[0095] depositing an N-type semiconductor layer 300 on the buffer layer 200;

[0096] depositing a low-temperature stress release layer 400 on the N-type semiconductor layer 300;

[0097] depositing a multi-quantum well light emitting layer 500 on the low-temperature stress release layer 400;

[0098] depositing an electron blocking layer 600 on the multi-quantum well light emitting layer 500;

[0099] depositing a P-type semiconductor layer 700 on the electron blocking layer 600;

[0100] The multi-quantum well light emitting layer 500 comprises, in sequence along the epitaxial direction, a well-front gradual change InGaN layer 510, a first blue light InGaN layer 520, a first AlGaInN interface protection layer 570, a green light InGaN layer 530, a second AlGaInN interface protection layer 580, a second blue light InGaN layer 540, a well-back gradual change InGaN layer 550 and a quantum barrier layer 560, which are periodically and alternately grown;

[0101] The well-front gradual change InGaN layer 510 comprises a plurality of first InGaN layers which are sequentially stacked, and the In component content of the plurality of first InGaN layers sequentially increases along the epitaxial direction;

[0102] The well-back gradual change InGaN layer 550 comprises a plurality of second InGaN layers which are sequentially stacked, and the In component content of the plurality of second InGaN layers sequentially decreases along the epitaxial direction;

[0103] The N2 atmosphere heat treatment is needed before depositing the first AlGaInN interface protection layer 570 and before depositing the second AlGaInN interface protection layer 580.

[0104] Embodiment 1

[0105] The blue-green LED epitaxial wafer provided by the embodiment of the application comprises, in sequence along an epitaxial direction, 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.

[0106] The multi-quantum well light-emitting layer comprises, in sequence along the epitaxial direction, a well-front gradual-change InGaN layer, a first blue-light InGaN layer, a first AlGaInN interface protection layer, a green-light InGaN layer, a second AlGaInN interface protection layer, a second blue-light InGaN layer, a well-back gradual-change InGaN layer and a quantum barrier layer, and the period number is 10.

[0107] The well-front gradual-change InGaN layer comprises a plurality of first InGaN layers stacked in sequence, and the In component content of the plurality of first InGaN layers increases in sequence along the epitaxial direction; and the well-back gradual-change InGaN layer comprises a plurality of second InGaN layers stacked in sequence, and the In component content of the plurality of second InGaN layers decreases in sequence along the epitaxial direction.

[0108] The well-front gradual-change InGaN layer is an InGaN material doped with Si elements, the Si doping concentration is 4.5×10 17 / cm³, the In component content is X1, X1 linearly increases from 0.05 to 0.10 along the epitaxial direction, the growth temperature is 830℃, the growth pressure is 250torr, and the growth thickness is 0.5nm.

[0109] The first blue-light InGaN layer is made of intentionally undoped InGaN material, the In component content is X2, X2=0.11, the growth thickness is 1.3nm, the growth temperature is 800℃, and the growth pressure is 250torr.

[0110] The growth thickness of the first AlGaInN interface protection layer is 0.15nm, the In component content is X 01 , X 01 =0.05, the Al component content is Y 01 , Y 01 =0.05; the growth temperature of the first AlGaInN interface protection layer is 780℃, and the growth pressure is 250torr.

[0111] The green InGaN layer is made of intentionally undoped InGaN material, the In component content is X3, X3=0.25, the growth thickness is 1.3nm, the growth temperature is 770℃, and the growth pressure is 250torr.

[0112] The growth thickness of the second AlGaInN interface protection layer is 0.15nm, the In component content is X 02 , X 02 =0.05, and the Al component content is Y 02 , Y 02 =0.05; the growth temperature of the second AlGaInN interface protection layer is 780℃, and the growth pressure is 250torr.

[0113] The second blue InGaN layer is made of intentionally undoped InGaN material, the In component content is X4, X4=0.11, the growth thickness is 1.3nm, the growth temperature is 800℃, and the growth pressure is 250torr.

[0114] The post-well graded InGaN layer is made of InGaN material doped with Si element, the Si doping concentration is 4.5×10 17 / cm³, the In component content is X5, X5 linearly decreases from 0.10 to 0.05 along the epitaxial direction, the growth temperature is 830℃, the growth pressure is 250torr, and the growth thickness is 0.5nm.

[0115] The quantum barrier layer includes a GaN layer and an AlGaN layer, and the growth thickness of the quantum barrier layer is 10nm.

[0116] The GaN layer is doped with Si element, and the Si doping concentration is 4.9×10 17 / cm³.

[0117] The Al component content of the AlGaN layer is Y6, Y6=0.25.

[0118] The growth temperature of the quantum barrier layer is 880℃, and the growth pressure is 250torr.

[0119] After depositing the first blue InGaN layer, before depositing the first AlGaInN interface protection layer, further comprising: heat treatment in N2 atmosphere, the treatment time is t1=90s, and the treatment temperature is W1=950℃.

[0120] After depositing the green InGaN layer, before depositing the second AlGaInN interface protection layer, further comprising: heat treatment in N2 atmosphere, the treatment time is t2=75s, and the treatment temperature is W2=880℃.

[0121] The preparation method is as follows:

[0122] A substrate is provided;

[0123] A buffer layer is deposited on the substrate;

[0124] An N-type semiconductor layer is deposited on the buffer layer;

[0125] A low-temperature stress release layer is deposited on the N-type semiconductor layer;

[0126] A multi-quantum well light-emitting layer is deposited on the low-temperature stress release layer;

[0127] An electron blocking layer is deposited on the multi-quantum well light-emitting layer;

[0128] A P-type semiconductor layer is deposited on the electron blocking layer.

[0129] Example 2

[0130] The difference between this example and Example 1 is that the In component content of the well-preceding graded InGaN layer is X1, and X1 linearly increases from 0.08 to 0.18 along the epitaxial direction; the In component content of the well-following graded InGaN layer is X5, and X5 linearly decreases from 0.15 to 0.05 along the epitaxial direction.

[0131] Example 3

[0132] The difference between this example and Example 1 is that the In component content of the well-preceding graded InGaN layer is X1, and X1 linearly increases from 0.01 to 0.03 along the epitaxial direction; the In component content of the well-following graded InGaN layer is X5, and X5 linearly decreases from 0.07 to 0.05 along the epitaxial direction.

[0133] Example 4

[0134] The difference between this example and Example 1 is that the growth thickness of the well-preceding graded InGaN layer is 0.9 nm; and the growth thickness of the well-following graded InGaN layer is 0.7 nm.

[0135] Example 5

[0136] The difference between this example and Example 1 is that the growth thickness of the well-preceding graded InGaN layer is 0.1 nm; and the growth thickness of the well-following graded InGaN layer is 0.3 nm.

[0137] Example 6

[0138] The difference between this example and Example 1 is that the In component content of the first blue quantum well layer is X2, and X2 = 0.05; the In component content of the green quantum well layer is X3, and X3 = 0.22; and the In component content of the second blue quantum well layer is X4, and X4 = 0.19.

[0139] Example 7

[0140] The difference between this example and Example 1 is that the In composition content of the first blue light quantum well layer is X2, X2=0.19; the In composition content of the green light quantum well layer is X3, X3=0.28; and the In composition content of the second blue light quantum well layer is X4, X4=0.05.

[0141] Example 8

[0142] The difference between this example and Example 1 is that the In composition content of the first AlGaInN interface protection layer is X 01 , X 01 =0.01; the Al composition content is Y 01 , Y 01 =0.01; and the growth thickness is 0.01 nm. The In composition content of the second AlGaInN interface protection layer is X 02 , X 02 =0.09; the Al composition content is Y 02 , Y 02 =0.09; and the growth thickness is 0.3 nm.

[0143] Example 9

[0144] The difference between this example and Example 1 is that the In composition content of the first AlGaInN interface protection layer is X 01 , X 01 =0.09; the Al composition content is Y 01 , Y 01 =0.09; and the growth thickness is 0.3 nm. The In composition content of the second AlGaInN interface protection layer is X 02 , X 02 =0.01; the Al composition content is Y 02 , Y 02 =0.01; and the growth thickness is 0.01 nm.

[0145] Example 10

[0146] The difference between this example and Example 1 is that after depositing the first blue light InGaN layer, before depositing the first AlGaInN interface protection layer, it further includes: heat treatment in N2 atmosphere, the treatment time is t1=50s, and the treatment temperature is W1=820℃. After depositing the green light InGaN layer, before depositing the second AlGaInN interface protection layer, it further includes: heat treatment in N2 atmosphere, the treatment time is t2=150s, and the treatment temperature is W2=980℃.

[0147] Comparative Example 1

[0148] The difference between the present comparative example and Example 1 is that no pre-well graded InGaN layer and post-well graded InGaN layer are provided.

[0149] Comparative Example 2

[0150] The difference between the present comparative example and Example 1 is that no first AlGaInN interface protection layer and second AlGaInN interface protection layer are provided.

[0151] Comparative Example 3

[0152] An LED epitaxial wafer is provided, comprising a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multiple quantum well light-emitting layer, an electron blocking layer and a P-type semiconductor layer which are sequentially stacked along an epitaxial direction;

[0153] The multiple quantum well light-emitting layer is a periodic structure of InGaN multiple quantum well layers and GaN quantum barrier layers, and the number of stacking periods is 8. In a single period, the In content of the InGaN quantum well layer is 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.

[0154] Comparative Example 4

[0155] The difference between the present comparative example and Example 1 is that no N2 atmosphere heat treatment is performed before depositing the first AlGaInN interface protection layer and before depositing the second AlGaInN interface protection layer.

[0156] The epitaxial wafers obtained in the examples and comparative examples are made into 20 μm x 20 μm LED chips, and tested under a working current density of 20 A / cm 2 The light efficiency improvement, WD STD (nm) and twin crystal (002) arcsec, (102) arcsec, color rendering index obtained by XRD testing of the epitaxial wafer of the tested chips are calculated based on Comparative Example 3.

[0157] It should be noted that the arcsec (002) data can represent screw dislocations, and the arcsec (102) data can represent mixed dislocations of screw dislocations 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 standard deviation of wavelength. The smaller the standard deviation, the more concentrated the chip parameter distribution and the more stable the manufacturing process.

[0158] 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.

[0159] Evaluation criteria:

[0160] Ra≥80: Good color rendering, meeting general lighting needs;

[0161] Ra≥95: Excellent color rendering, close to the effect of natural light;

[0162] Ra<70: Poor color rendering, which may lead to color distortion.

[0163] 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 how well a light source reproduces the true colors of an object.

[0164] Evaluation criteria:

[0165] Rf≥80: Good fidelity;

[0166] Rf≥95: Excellent fidelity;

[0167] Rf<70: Insufficient fidelity, obvious color distortion.

[0168] The test results are as follows:

[0169]

[0170] The test results above show that the multi-quantum-well light-emitting layer of the present invention comprises a first blue InGaN layer, a green InGaN layer, and a second blue InGaN layer, capable of emitting blue and green light bands. The gradient InGaN layer before and after the well, combined with the In composition content relationship of X3>X2=X4, effectively reduces the lattice mismatch stress between the quantum well InGaN material and the barrier layer material, significantly improving the quality of the multi-quantum-well light-emitting layer. This is beneficial for increasing the radiative recombination efficiency of the active region, thereby improving the luminous efficacy and yield of blue-green LED light sources.

[0171] A first AlGaInN interface protective layer is deposited between the first blue InGaN layer and the green InGaN layer, and a second AlGaInN interface protective layer is deposited between the green InGaN layer and the second blue InGaN layer. The energy bands of the AlGaInN interface protective layers can separate the energy bands of the quantum well layer InGaN material, so that the radiative recombination of electrons and holes in each quantum well layer InGaN material does not interfere with each other, thereby improving the uniformity and luminous efficiency of the blue-green LED chip.

[0172] The InGaN layer surface crystalline quality poor part and high In component In cluster and other defects can be decomposed by N2 atmosphere heat treatment, which is beneficial to improve the crystal quality of the material, and the material surface is micro-rough, which can reduce the in-plane total reflection of photons in the semiconductor material and light absorption loss, and improve the light efficiency.

[0173] The above is the preferred embodiment of the present application, it should be pointed out that, for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements also regarded as the protection scope of the present application.

Claims

1. A blue-green 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 gradient InGaN layer in front of the well, a first blue InGaN layer, a first AlGaInN interface protection layer, a green InGaN layer, a second AlGaInN interface protection layer, a second blue InGaN layer, a gradient InGaN layer behind the well, and a quantum barrier layer, which are grown alternately and periodically along the epitaxial direction. The pre-well gradient InGaN layer comprises multiple layers of first InGaN layers stacked sequentially, and the In composition content of the multiple layers of first InGaN layers increases sequentially along the epitaxial direction. The post-well gradient InGaN layer comprises multiple layers of second InGaN layers stacked sequentially, wherein the In content of the multiple layers of second InGaN layers decreases sequentially along the epitaxial direction. Specifically, N2 atmosphere heat treatment is required before depositing the first AlGaInN interface protective layer and before depositing the second AlGaInN interface protective layer.

2. The blue-green 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 emission wavelength of the first blue InGaN layer is 391nm~487nm; The green InGaN layer emits light at a wavelength of 511 nm to 565 nm. The emission wavelength of the second blue InGaN layer is 391nm~487nm.

3. The blue-green LED epitaxial wafer as described in claim 1, characterized in that, The growth thickness of the gradient InGaN layer before the well is 0.03 nm to 1.0 nm; The gradient InGaN layer before the well is an InGaN material doped with Si, and the Si doping concentration is 1.12 × 10⁻⁶. 17 / cm³~7.89×10 17 / cm³, the content of its In component is X1, X1≤0.19; The thickness of the gradient InGaN layer behind the well is 0.03 nm to 1.0 nm. The gradient InGaN layer behind the well is an InGaN material doped with Si, with a Si doping concentration of 1.12 × 10⁻⁶. 17 / cm³~7.89×10 17 / cm³, its In component content is X5, X5≤0.

19.

4. The blue-green LED epitaxial wafer as described in claim 1, characterized in that, After depositing the first blue InGaN layer and before depositing the first AlGaInN interface protective layer, the process further includes: heat treatment in an N2 atmosphere for a treatment time of t1, 8s≤t1≤180s, and a treatment temperature of W1, 810℃≤W1≤1050℃. After depositing the green InGaN layer and before depositing the second AlGaInN interface protective layer, the process further includes: heat treatment in N2 atmosphere, with a treatment time of t2, 6s≤t2≤150s, and a treatment temperature of W2, 800℃≤W2≤1030℃. The growth thickness of both the first AlGaInN interface protective layer and the second AlGaInN interface protective layer is 0.01 nm to 0.3 nm; the In content of the first AlGaInN interface protective layer is X. 01 X 01 ≤0.09, Al component content is Y 01 Y 01 ≤0.09; The In content of the second AlGaInN interface protective layer is X 02 X 02 ≤0.09, Al component content is Y 02 Y 02 ≤0.

09.

5. The blue-green LED epitaxial wafer as described in claim 4, characterized in that, t1>t2, W1>W2.

6. The blue-green LED epitaxial wafer as described in claim 1, characterized in that, The first blue light InGaN layer is made of intentionally undoped InGaN material, with an In content of X2, 0.05≤X2≤0.19, and a growth thickness of 0.3nm~2.6nm; 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 0.3nm~2.6nm; The second blue light InGaN layer is made of intentionally undoped InGaN material, with an In content of X4, 0.05≤X4≤0.19, and a growth thickness of 0.3nm~2.6nm; The quantum barrier layer includes a GaN layer and / or an AlGaN layer, and the growth thickness of the quantum barrier layer is 5nm~16nm. The GaN layer is doped with Si, and the Si doping concentration is 1.6 × 10⁻⁶. 17 / cm³~9.8×10 17 / cm³; The Al component content of the AlGaN layer is Y6, where Y6≤0.

5.

7. The blue-green LED epitaxial wafer as described in claim 6, characterized in that, The In component content relationship between the first blue light InGaN layer, the green light InGaN layer, and the second blue light InGaN layer is X3>X2=X4.

8. The method for preparing a blue-green LED epitaxial wafer according to any one of claims 1 to 7, characterized in that, Includes the following steps: Provide a substrate; A buffer layer is deposited on the substrate; An N-type semiconductor layer is deposited on the buffer layer; A low-temperature stress relief layer is deposited on the N-type semiconductor layer; A multi-quantum-well light-emitting layer is deposited on the low-temperature stress-relieving layer; An electron blocking layer is deposited on the multi-quantum-well light-emitting layer; A P-type semiconductor layer is deposited on the electron blocking layer; The multi-quantum-well light-emitting layer includes a gradient InGaN layer in front of the well, a first blue InGaN layer, a first AlGaInN interface protection layer, a green InGaN layer, a second AlGaInN interface protection layer, a second blue InGaN layer, a gradient InGaN layer behind the well, and a quantum barrier layer, which are grown alternately and periodically along the epitaxial direction. The pre-well gradient InGaN layer comprises multiple layers of first InGaN layers stacked sequentially, and the In composition content of the multiple layers of first InGaN layers increases sequentially along the epitaxial direction. The post-well gradient InGaN layer comprises multiple layers of second InGaN layers stacked sequentially, wherein the In content of the multiple layers of second InGaN layers decreases sequentially along the epitaxial direction. Specifically, N2 atmosphere heat treatment is required before depositing the first AlGaInN interface protective layer and before depositing the second AlGaInN interface protective layer.

9. The method for preparing a blue-green LED epitaxial wafer as described in claim 8, characterized in that, The growth cycle number of the multi-quantum-well light-emitting layer is 3 to 17; The emission wavelength of the first blue InGaN layer is 391nm~487nm; The green InGaN layer emits light at a wavelength of 511 nm to 565 nm. The emission wavelength of the second blue InGaN layer is 391nm~487nm.

10. The method for preparing a blue-green LED epitaxial wafer as described in claim 8, characterized in that, After depositing the first blue InGaN layer and before depositing the first AlGaInN interface protective layer, the process further includes: heat treatment in an N2 atmosphere for a treatment time of t1, 8s≤t1≤180s, and a treatment temperature of W1, 810℃≤W1≤1050℃. After depositing the green InGaN layer and before depositing the second AlGaInN interface protective layer, the process further includes: heat treatment in N2 atmosphere, with a treatment time of t2, 6s≤t2≤150s, and a treatment temperature of W2, 800℃≤W2≤1030℃. The growth thickness of both the first AlGaInN interface protective layer and the second AlGaInN interface protective layer is 0.01 nm to 0.3 nm; the In content of the first AlGaInN interface protective layer is X. 01 X 01 ≤0.09, Al component content is Y 01 Y 01 ≤0.09; The In content of the second AlGaInN interface protective layer is X 02 X 02 ≤0.09, Al component content is Y 02 Y 02 ≤0.09.

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