Light-emitting diode epitaxial wafer, method for preparing same, and light-emitting diode

Abstract

The present invention discloses a light-emitting diode epitaxial wafer, a preparation method thereof, and a light-emitting diode, relating to the field of semiconductor optoelectronic devices. The light-emitting diode epitaxial wafer sequentially includes a substrate, a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer; the multi-quantum well layer is a periodic structure, and each period includes a pre-well protection layer, a quantum well layer, a post-well protection layer, and a quantum barrier layer stacked in sequence; the pre-well protection layer sequentially includes In x Ga 1‑x N layer, Al y Ga 1‑y N layer, and In z Ga 1‑z N layer, the quantum well layer is In w Ga 1‑w N layer, the post-well protection layer sequentially includes In α Ga 1‑α N layer, Al β Ga 1‑β N layer, and an undoped GaN layer, the quantum barrier layer is a GaN layer; x < z ≤ w, α ≤ w, y ≥ β; and along the growth direction, z gradually increases and α gradually decreases. Implementing the present invention can improve the light-emitting efficiency of the light-emitting diode.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic devices, and particularly to a light-emitting diode epitaxial wafer, a preparation method thereof, and a light-emitting diode. Background Art

[0002] GaN-based light-emitting diodes are currently the most widely used light-emitting diodes. For the GaN material system, electrons have higher mobility and smaller effective mass compared to holes. At the same time, electrons are more easily activated and have higher concentrations, which leads to extremely mismatched electron-hole concentrations injected into the active region. The quantum wells near the N-type semiconductor layer hardly emit light, while electrons can easily be injected into the active region and even enter the P-type semiconductor layer, causing electron leakage and reducing the light-emitting efficiency. In addition, currently, most GaN-based light-emitting diode epitaxial wafers use InGaN-GaN multi-quantum well layers as the active region. Due to the compressive strain between InGaN and GaN, the overlap of the electron wave function and the hole wave function is reduced, resulting in a decrease in the light-emitting efficiency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a light-emitting diode epitaxial wafer and a preparation method thereof, which can improve the light-emitting efficiency of the light-emitting diode.

[0004] Another technical problem to be solved by the present invention is to provide a light-emitting diode.

[0005] To solve the above problems, the present invention discloses a light-emitting diode epitaxial wafer, which includes a substrate, a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially stacked on the substrate; the multi-quantum well layer is a periodic structure, and each period includes a pre-well protection layer, a quantum well layer, a post-well protection layer, and a quantum barrier layer stacked in sequence;

[0006] Among them, the pre-well protection layer includes an In x Ga 1-x N layer, an Al y Ga 1-y N layer, and an In z Ga 1-z N layer stacked in sequence. The quantum well layer is an In w Ga 1-w N layer. The post-well protection layer includes an In α Ga 1-α N layer, an Al β Ga 1-β N layer, and an undoped GaN layer stacked in sequence. The quantum barrier layer is a GaN layer;

[0007] x < z ≤ w, α ≤ w, y ≥ β; and along the growth direction of the light-emitting diode epitaxial wafer, z gradually increases and α gradually decreases.

[0008] As an improvement of the above technical solution, along the growth direction of the light-emitting diode epitaxial wafer, y gradually increases and β gradually decreases;

[0009] and the maximum value of y is 0.15 and the maximum value of β is 0.12.

[0010] As an improvement of the above technical solution, along the growth direction of the light-emitting diode epitaxial wafer, the Al y Ga 1-y composition in the N layer gradually increases from y1 to y2, and the Al β Ga 1-β composition in the N layer gradually decreases from β1 to β2;

[0011] y2 > β1, y1 > β2;

[0012] The value range of y1 is 0.02 to 0.06, the value range of y2 is 0.06 to 0.15, the value range of β1 is 0.05 to 0.12, and the value range of β2 is 0.01 to 0.06.

[0013] As an improvement of the above technical solution, Si is doped in the In x Ga 1-x N layer, and the doping concentration ≤ 1 × 10 18 cm -3 .

[0014] As an improvement of the above technical solution, the number of periods of the multi-quantum well layer is 5 to 16;

[0015] The In x Ga 1-x N layer has a thickness of 0.1 nm to 0.5 nm, and the value range of x is 0.01 to 0.05;

[0016] The Al y Ga 1-y N layer has a thickness of 0.1 nm to 0.8 nm, and the value range of y is 0.02 to 0.15;

[0017] The In z Ga 1-z N layer has a thickness of 0.2 nm to 1 nm, and the value range of z is 0.02 to 0.4;

[0018] The In w Ga 1-w N layer has a thickness of 1.8 nm to 3.9 nm, and the value range of w is 0.1 to 0.4;

[0019] The In α Ga 1-α layer of N has a thickness of 0.2 nm to 1 nm, and the value range of α is 0.08 to 0.4;

[0020] The Al β Ga 1-β layer of N has a thickness of 0.1 nm to 0.8 nm, and the value range of β is 0.01 to 0.1;

[0021] The undoped GaN layer has a thickness of 0.1 nm to 0.5 nm;

[0022] Si is doped in the quantum barrier layer, and the doping concentration is 2.5×10 17 cm -3 ~8.7×10 17 cm -3 , and the quantum barrier layer has a thickness of 6 nm to 15 nm.

[0023] Correspondingly, the present invention also discloses a method for preparing a light-emitting diode epitaxial wafer for preparing the above-mentioned light-emitting diode epitaxial wafer, which includes:

[0024] Providing a substrate;

[0025] Growing a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer on the substrate in sequence; the multi-quantum well layer is a periodic structure, and each period includes a pre-well protection layer, a quantum well layer, a post-well protection layer, and a quantum barrier layer stacked in sequence;

[0026] Among them, the pre-well protection layer includes In x Ga 1-x N layer, Al y Ga 1-y N layer, and In z Ga 1-z N layer stacked in sequence, the quantum well layer is In w Ga 1-w N layer, the post-well protection layer includes In α Ga 1-α N layer, Al β Ga 1-β N layer, and an undoped GaN layer stacked in sequence, and the quantum barrier layer is a GaN layer;

[0027] x < z ≤ w, α ≤ w, y ≥ β; and along the growth direction of the light-emitting diode epitaxial wafer, z gradually increases and α gradually decreases.

[0028] As an improvement of the above technical solution, the In x Ga 1-xAfter the growth of the N layer is completed, anneal it in the first mixed gas to roughen its surface;

[0029] The annealing temperature is 800 °C to 1050 °C, and the annealing pressure is 30 torr to 360 torr; the first mixed gas is a mixed gas of N 2 and H 2 , and the volume ratio of N 2 and H 2 is 1:0.13 to 1:8.2.

[0030] As an improvement to the above technical solution, after the growth of the In α Ga 1-α N layer is completed, anneal it in the second mixed gas to improve its crystallization degree;

[0031] The annealing temperature is 800 °C to 1050 °C, and the annealing pressure is 30 torr to 360 torr; the second mixed gas is a mixed gas of N 2 and NH 3 , and the volume ratio of N 2 and NH 3 is 1:0.2 to 1:5.6.

[0032] As an improvement to the above technical solution, the growth temperature of the In x Ga 1-x N layer is 750 °C to 920 °C, and the growth pressure is 30 torr to 360 torr;

[0033] The growth temperature of the Al y Ga 1-y N layer is 780 °C to 920 °C, and the growth pressure is 30 torr to 360 torr;

[0034] The growth temperature of the In z Ga 1-z N layer is 680 °C to 890 °C, and the growth pressure is 30 torr to 360 torr;

[0035] The growth temperature of the In w Ga 1-w N layer is 665 °C to 820 °C, and the growth pressure is 30 torr to 360 torr;

[0036] The growth temperature of the In α Ga 1-α N layer is 680 °C to 890 °C, and the growth pressure is 30 torr to 360 torr;

[0037] The growth temperature of the Al β Ga 1-βThe growth temperature of the N layer is 780 °C to 920 °C, and the growth pressure is 30 torr to 360 torr;

[0038] The growth temperature of the undoped GaN layer is 800 °C to 920 °C, and the growth pressure is 30 torr to 360 torr;

[0039] The growth temperature of the quantum barrier layer is 816 °C to 935 °C, and the growth pressure is 30 torr to 360 torr.

[0040] Correspondingly, the present invention also discloses a light-emitting diode, which includes the above-mentioned light-emitting diode epitaxial wafer.

[0041] Implementing the present invention has the following beneficial effects:

[0042] In the light-emitting diode epitaxial wafer in an embodiment of the present invention, the multiple quantum well layer is a periodic structure, and each period includes a pre-well protection layer, a quantum well layer, a post-well protection layer, and a quantum barrier layer stacked in sequence; wherein, the pre-well protection layer includes In x Ga 1-x N layer, Al y Ga 1-y N layer, and In z Ga 1-z N layer, the quantum well layer is In w Ga 1-w N layer, the post-well protection layer includes In α Ga 1-α N layer, Al β Ga 1-β N layer, and an undoped GaN layer, the quantum barrier layer is a GaN layer; x < z ≤ w, α ≤ w, y ≥ β; and along the growth direction of the light-emitting diode epitaxial wafer, z gradually increases, and α gradually decreases. Based on the above-mentioned light-emitting diode epitaxial wafer, firstly, on both sides of the quantum well layer, an In z Ga 1-z N layer with gradually increasing In composition and an In α Ga 1-α N layer with gradually decreasing In composition are respectively arranged, which can effectively reduce the lattice mismatch between the quantum well layer (In w Ga 1-w N layer) and the quantum barrier layer (GaN layer), weaken the compressive strain, improve the radiative recombination efficiency, and improve the light-emitting efficiency. Secondly, by setting Al y Ga 1-y N layer and Al β Ga 1-β N layer on both sides of the quantum well layer, the carrier confinement effect can be improved, the electron overflow phenomenon can be significantly reduced, and the light-emitting efficiency can be improved. Moreover, by controlling y ≥ β, the Al β Ga1-β The N-layer functions as a hole barrier, enhancing the hole concentration in the quantum well layer and improving the radiative recombination efficiency. Thirdly, the In in the pre-well protective layer x Ga 1-x The proportion of In component in the N-layer is relatively small (x < z ≤ w), which further optimizes the transition from the quantum barrier layer to the quantum well layer and weakens the compressive strain. In summary, the multiple quantum well layer in this embodiment can significantly reduce electron overflow, increase the effective hole concentration, weaken the compressive strain, thereby effectively improving the radiative recombination efficiency and the luminescence efficiency. Description of the Drawings

[0043] Figure 1 is a schematic structural diagram of a light-emitting diode epitaxial wafer in an embodiment of the present invention;

[0044] Figure 2 is a flowchart of a method for manufacturing a light-emitting diode epitaxial wafer in an embodiment of the present invention.

[0045] 100 is a substrate, 200 is a buffer layer, 300 is an intrinsic GaN layer, 400 is an N-type GaN layer, 500 is a multiple quantum well layer, 510 is a pre-well protective layer, 511 is In x Ga 1-x N layer, 512 is an Al y Ga 1-y N layer, 513 is In z Ga 1-z N layer, 520 is a quantum well layer, 530 is a post-well protective layer, 531 is In α Ga 1-α N layer, 532 is an Al β Ga 1-β N layer, 533 is an undoped GaN layer, 540 is a quantum barrier layer, 600 is an electron blocking layer, 700 is a P-type GaN layer. Detailed Embodiments

[0046] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below.

[0047] Referring to Figure 1 , the present invention discloses a light-emitting diode epitaxial wafer, which includes a substrate 100, a buffer layer 200, an intrinsic GaN layer 300, an N-type GaN layer 400, a multiple quantum well layer 500, an electron blocking layer 600, and a P-type GaN layer 700 that are sequentially stacked on the substrate 100. Among them, the multiple quantum well layer 500 is a periodic structure, and each period includes a pre-well protective layer 510, a quantum well layer 520, a post-well protective layer 530, and a quantum barrier layer 540 that are sequentially stacked; among them, the pre-well protective layer 510 includes In x Ga 1-xN-layer 511, Al y Ga 1-y N-layer 512 and In z Ga 1-z N-layer 513, the quantum well layer 520 is In w Ga 1-w N-layer, the post-well protection layer 530 includes successively stacked In α Ga 1-α N-layer 531, Al β Ga 1-β N-layer 532 and undoped GaN layer 533, the quantum barrier layer 540 is a GaN layer; x < z ≤ w, α ≤ w, y ≥ β; and along the growth direction of the light-emitting diode epitaxial wafer, z gradually increases and α gradually decreases. Based on the above-mentioned light-emitting diode epitaxial wafer, firstly, on both sides of the quantum well layer 520, In z Ga 1-z N-layer 513 with gradually increasing In composition and In α Ga 1-α N-layer 531 with gradually decreasing In composition are provided, which can effectively reduce the lattice mismatch between the quantum well layer 520 (In w Ga 1-w N-layer) and the quantum barrier layer 540 (GaN layer), weaken the compressive strain, and are beneficial to improving the radiative recombination efficiency and the light-emitting efficiency. Secondly, by setting Al y Ga 1-y N-layer 512 and Al β Ga 1-β N-layer 532 on both sides of the quantum well layer 520, the carrier confinement effect can be improved, the electron overflow phenomenon can be significantly reduced, and the light-emitting efficiency can be improved. Moreover, by controlling y ≥ β, the blocking effect of the Al β Ga 1-β N-layer 532 on holes can be weakened, the hole concentration in the quantum well layer 520 can be increased, and the radiative recombination efficiency can be improved. Thirdly, the proportion of the In composition in the In x Ga 1-x N-layer 511 in the pre-well protection layer 510 is relatively small (x < z ≤ w), which further optimizes the transition from the quantum barrier layer 540 to the quantum well layer 520 and weakens the compressive strain. In summary, the multiple quantum well layer 500 in this embodiment can significantly reduce electron overflow, increase the effective hole concentration, weaken the compressive strain, and thus effectively improve the radiative recombination efficiency and the light-emitting efficiency.

[0048] Specifically, in some embodiments, the number of periods of the multiple quantum well layer 500 is 5 to 20, exemplarily 7, 9, 11, 13, 15 or 17, but not limited thereto. Preferably it is 5 to 16.

[0049] Specifically, in some embodiments, In xGa 1-x The thickness of the InGaN layer 511 is 0.1 nm to 0.8 nm, exemplarily 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm or 0.7 nm, but not limited thereto; preferably 0.1 nm to 0.5 nm. In x Ga 1-x The proportion of In component (i.e., x) in the InGaN layer 511 is 0.01 to 0.08, exemplarily 0.02, 0.03, 0.04, 0.05, 0.06 or 0.07, but not limited thereto. Preferably 0.01 to 0.05.

[0050] Specifically, in some embodiments, Al y Ga 1-y The thickness of the AlGaN layer 512 is 0.1 nm to 1 nm, exemplarily 0.2 nm, 0.4 nm, 0.6 nm, 0.8 nm or 0.9 nm, but not limited thereto. Preferably 0.1 nm to 0.8 nm. Al y Ga 1-y The proportion of Al component (i.e., y) in the AlGaN layer 512 is 0.02 to 0.2, exemplarily 0.04, 0.06, 0.08, 0.1, 0.12, 0.14 or 0.16, but not limited thereto. Preferably 0.02 to 0.15. It should be noted that here, the proportion of Al component in the AlGaN layer 512 is the average proportion of Al component in the whole layer. y Ga 1-y The proportion of Al component in the AlGaN layer 512 is the average proportion of Al component in the whole layer.

[0051] Specifically, in some embodiments, In z Ga 1-z The thickness of the InGaN layer 513 is 0.2 nm to 1.5 nm, exemplarily 0.4 nm, 0.6 nm, 0.8 nm, 1 nm, 1.2 nm or 1.4 nm, but not limited thereto. Preferably 0.2 nm to 1 nm. In z Ga 1-z The proportion of In component (i.e., z) in the InGaN layer 513 is 0.02 to 0.4, exemplarily 0.04, 0.08, 0.12, 0.25, 0.34 or 0.45, but not limited thereto. It should be noted that here, the proportion of In component in the InGaN layer 513 is the average proportion of In component in the whole layer. z Ga 1-z The proportion of In component in the InGaN layer 513 is the average proportion of In component in the whole layer.

[0052] Specifically, in some embodiments, In w Ga 1-w The thickness of the InGaN layer is 1.8 nm to 5 nm, exemplarily 2 nm, 2.4 nm, 3 nm, 3.5 nm, 4 nm or 4.8 nm, but not limited thereto; preferably 1.8 nm to 3.9 nm. Inw Ga 1-w The proportion of In component in the GaN layer (i.e., w) is 0.1 to 0.45, exemplarily 0.15, 0.2, 0.25, 0.3 or 0.35, but not limited thereto. Preferably it is 0.1 to 0.4.

[0053] Specifically, in some embodiments, In α Ga 1-α The thickness of the InGaN layer 531 is 0.2 nm to 1.5 nm, exemplarily 0.4 nm, 0.6 nm, 0.8 nm, 1.2 nm or 1.4 nm, but not limited thereto. Preferably it is 0.2 nm to 1 nm. In α Ga 1-α The proportion of In component in the InGaN layer 531 (i.e., α) is 0.05 to 0.4, exemplarily 0.08, 0.14, 0.22, 0.31 or 0.38, but not limited thereto. Preferably it is 0.08 to 0.4. It should be noted that here, the proportion of In component in the InGaN layer 531 is the average proportion of In component in the whole layer. α Ga 1-α The proportion of In component in the InGaN layer 531 is the average proportion of In component in the whole layer.

[0054] Specifically, in some embodiments, Al β Ga 1-β The thickness of the AlGaN layer 532 is 0.1 nm to 1 nm, exemplarily 0.2 nm, 0.4 nm, 0.6 nm, 0.8 nm or 0.9 nm, but not limited thereto. Preferably it is 0.1 nm to 0.8 nm. Al β Ga 1-β The proportion of Al component in the AlGaN layer 532 (i.e., β) is 0.01 to 0.15, exemplarily 0.02, 0.04, 0.06, 0.08, 0.1, 0.12 or 0.14, but not limited thereto. Preferably it is 0.01 to 0.1. It should be noted that here, the proportion of Al component in the AlGaN layer 532 is the average proportion of Al component in the whole layer. β Ga 1-β The proportion of Al component in the AlGaN layer 532 is the average proportion of Al component in the whole layer.

[0055] Specifically, in some embodiments, the thickness of the undoped GaN layer 533 is 0.1 nm to 0.8 nm, exemplarily 0.2 nm, 0.4 nm, 0.6 nm or 0.7 nm. Preferably it is 0.1 nm to 0.5 nm.

[0056] Specifically, in some embodiments, the thickness of the quantum barrier layer 540 is 5 nm to 15 nm, exemplarily 6 nm, 7.5 nm, 9 nm, 10.5 nm, 12 nm or 13.5 nm, but not limited thereto. Preferably it is 6 nm to 15 nm.

[0057] Preferably, in some embodiments, Si is doped in the quantum barrier layer 540, and the doping concentration is 2.5×10 17 cm -3 ~8.7×10 17 cm -3 。

[0058] Preferably, in some embodiments, along the growth direction of the light-emitting diode epitaxial wafer, the In z Ga 1-z N layer 513, the In composition (i.e., z) increases from 0.02 to 0.06 and then increases to 0.08 to 0.4, and the In α Ga 1-α N layer 531, the In composition (i.e., α) decreases from 0.08 to 0.4 and then decreases to 0.01 to 0.05. Based on the above composition control, the compressive strain can be further weakened and the light-emitting efficiency can be improved.

[0059] Preferably, in some embodiments, Si is doped in the In x Ga 1-x N layer 511, and its doping concentration ≤ 1×10 18 cm -3 , based on this embodiment, the drift velocity of electrons can be further reduced and the light-emitting efficiency can be improved. More specifically, the doping concentration of Si in the In x Ga 1-x N layer 511 is 1.2×10 17 cm -3 ~6.5×10 17 cm -3 。

[0060] Preferably, in some embodiments, along the growth direction of the light-emitting diode epitaxial wafer, the Al y Ga 1-y N layer 512, the Al composition (i.e., y) gradually increases, and the Al β Ga 1-β N layer 532, the Al composition (i.e., β) gradually decreases, and the maximum value of y is 0.15, and the maximum value of β is 0.12. Based on the above embodiment, the piezoelectric polarization can be further weakened, the polarization electric field intensity can be reduced, the overlap rate of the electron and hole wave functions can be increased, and the light-emitting efficiency can be improved.

[0061] More preferably, in some embodiments, along the growth direction of the light-emitting diode epitaxial wafer, the Al y Ga 1-y N layer 512, the Al composition increases from y1 to y2, and the Al β Ga 1-βIn the N-layer 532, the Al component gradually decreases from β1 to β2; y2 > β1, y1 > β2; the value range of y1 is 0.02 to 0.06, the value range of y2 is 0.06 to 0.15, the value range of β1 is 0.05 to 0.12, and the value range of β2 is 0.01 to 0.06.

[0062] Specifically, in some embodiments, the substrate 100 is a sapphire substrate, a silicon substrate, or a carbide substrate, but is not limited thereto.

[0063] Specifically, in some embodiments, the buffer layer 200 is an AlN layer or an AlGaN layer, but is not limited thereto. The thickness of the buffer layer 200 is 20 nm to 80 nm.

[0064] Specifically, in some embodiments, the thickness of the intrinsic GaN layer 300 is 1 μm to 3 μm.

[0065] Specifically, in some embodiments, the N-type doping (Si) concentration in the N-type GaN layer 400 is 5×10 18 cm -3 ~5×10 19 cm -3 , and the thickness is 1 μm to 5 μm.

[0066] Specifically, in some embodiments, the electron blocking layer 600 is an AlInGaN layer or an AlGaN layer, but is not limited thereto. Preferably, it is an AlInGaN layer, the proportion of the Al component is 0.01 to 0.1, the proportion of the In component is 0.01 to 0.2, and the thickness is 10 nm to 50 nm.

[0067] Specifically, in some embodiments, in some embodiments, the thickness of the P-type GaN layer 700 is 50 nm to 200 nm, and its Mg doping concentration is 1×10 19 cm -3 ~5×10 20 cm -3 .

[0068] Correspondingly, referring to Figure 2 , the present invention further provides a method for preparing a light-emitting diode epitaxial wafer for preparing the above-mentioned light-emitting diode epitaxial wafer, which specifically includes the following steps:

[0069] S1: Provide a substrate;

[0070] S2: Sequentially grow a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer on the substrate;

[0071] Among them, the multiple quantum well layer 500 is a periodic structure, and each period includes a pre-well protection layer 510, a quantum well layer 520, a post-well protection layer 530, and a quantum barrier layer 540 that are stacked in sequence; among them, the pre-well protection layer 510 includes an In x Ga 1-x N layer 511, an Al y Ga 1-y N layer 512, and an In z Ga 1-z N layer 513 that are stacked in sequence. The quantum well layer 520 is an In w Ga 1-w N layer. The post-well protection layer 530 includes an In α Ga 1-α N layer 531, an Al β Ga 1-β N layer 532, and an undoped GaN layer 533. The quantum barrier layer 540 is a GaN layer; x < z ≤ w, α ≤ w, y ≥ β; and along the growth direction of the light-emitting diode epitaxial wafer, z gradually increases and α gradually decreases. Based on the above light-emitting diode epitaxial wafer, firstly, on both sides of the quantum well layer 520, an In z Ga 1-z N layer 513 with a gradually increasing In composition and an In α Ga 1-α N layer 531 with a gradually decreasing In composition are respectively arranged. This can effectively reduce the lattice mismatch between the quantum well layer 520 (In w Ga 1-w N layer) and the quantum barrier layer 540 (GaN layer), weaken the compressive strain, and is beneficial to improving the radiative recombination efficiency and the light-emitting efficiency. Secondly, by arranging Al y Ga 1-y N layer 512 and Al β Ga 1-β N layer 532 on both sides of the quantum well layer 520, the carrier confinement effect can be improved, the electron overflow phenomenon can be significantly reduced, and the light-emitting efficiency can be improved. Moreover, by controlling y ≥ β, the blocking effect of the Al β Ga 1-β N layer 532 on holes can be weakened, the hole concentration in the quantum well layer 520 can be increased, and the radiative recombination efficiency can be improved. Thirdly, the proportion of the In component in the In x Ga 1-x N layer 511 in the pre-well protection layer 510 is relatively small (x < z ≤ w), which further optimizes the transition from the quantum barrier layer 540 to the quantum well layer 520 and weakens the compressive strain. In summary, the multiple quantum well layer 500 in this embodiment can significantly reduce electron overflow, increase the effective hole concentration, weaken the compressive strain, and thus effectively improve the radiative recombination efficiency and the light-emitting efficiency.

[0072] Specifically, in some embodiments, step S2 includes:

[0073] S21: Growing a buffer layer on a substrate;

[0074] Specifically, the buffer layer can be grown by PVD, MOCVD, MBE or VPE, but is not limited thereto.

[0075] Preferably, in some embodiments, an AlN layer is grown by PVD as the buffer layer.

[0076] S22: Growing an intrinsic GaN layer on the buffer layer;

[0077] Specifically, the intrinsic GaN layer can be grown by PVD, MOCVD, MBE or VPE, but is not limited thereto.

[0078] Preferably, in some embodiments, the intrinsic GaN layer is grown by MOCVD. The growth temperature is 1100°C to 1150°C, and the growth pressure is 100 torr to 500 torr.

[0079] S23: Growing an N-type GaN layer on the intrinsic GaN layer;

[0080] Specifically, the N-type GaN layer can be grown by MOCVD, MBE or VPE, but is not limited thereto.

[0081] Preferably, in an embodiment of the present invention, the N-type GaN layer is grown by MOCVD; the growth temperature is 1100°C to 1150°C, and the growth pressure is 100 torr to 500 torr.

[0082] S24: Growing a multi-quantum well layer on the N-type GaN layer;

[0083] Specifically, in some embodiments, a pre-well protection layer, a quantum well layer, a post-well protection layer and a quantum barrier layer are periodically grown by MOCVD until a multi-quantum well layer is obtained.

[0084] Specifically, In x Ga 1-x N layer has a growth temperature of 750°C to 920°C and a growth pressure of 30 torr to 360 torr; Al y Ga 1-y N layer has a growth temperature of 780°C to 920°C and a growth pressure of 30 torr to 360 torr; In z Ga 1-z N layer has a growth temperature of 680°C to 890°C and a growth pressure of 30 torr to 360 torr; In w Ga 1-wThe growth temperature of the N layer is 665℃~820℃, and the growth pressure is 30torr~360torr; In α Ga 1-α The growth temperature of the N layer is 680℃~890℃, and the growth pressure is 30torr~360torr; the Al β Ga 1-β The growth temperature of the N layer is 780℃~920℃, and the growth pressure is 30torr~360torr; the growth temperature of the undoped GaN layer is 800℃~920℃, and the growth pressure is 30torr~360torr; the growth temperature of the quantum barrier layer is 816℃~935℃, and the growth pressure is 30torr~360torr.

[0085] Preferably, in some embodiments, In x Ga 1-x After the N layer is grown, annealing is performed in the first mixed gas at a temperature of 800°C to 1050°C and a pressure of 30 torr to 360 torr. The first mixed gas is N 2 and H 2 Mixed gas, N 2 and H 2 The volume ratio is 1:0.13~1:8.2. After the above annealing treatment, defects such as In clusters with high In components can be decomposed, which is beneficial to improving the crystal quality of each layer grown subsequently. At the same time, a rough material surface is formed, which can reduce the in-plane total reflection and light absorption loss of photons in semiconductor materials, improve light extraction efficiency, and further improve luminous efficiency.

[0086] Preferably, in some embodiments, In α Ga 1-α After the N layer is grown, annealing is performed in the second mixed gas. The annealing temperature is 800℃~1050℃ and the annealing pressure is 30torr~360torr. The second mixed gas is N 2 and NH 3 Mixed gas, N 2 and NH 3 The volume ratio is 1:0.2~1:5.6. Through the above annealing procedure, the material with poor surface crystallization quality can be decomposed, and the clusters with high In components can be redistributed and then recrystallized, thereby improving the crystal quality and further improving the luminous efficiency.

[0087] S25: growing an electron blocking layer on the multi-quantum well layer;

[0088] Specifically, an AlInGaN layer or an AlGaN layer may be grown by MOCVD, MBE, or VPE as the electron blocking layer, but is not limited thereto.

[0089] Preferably, in some embodiments, the AlInGaN layer is grown by MOCVD as an electron blocking layer, with a growth temperature of 900 °C to 1000 °C and a growth pressure of 100 torr to 300 torr.

[0090] S26: Grow a P-type GaN layer on the electron blocking layer;

[0091] Specifically, the P-type GaN layer can be grown by MOCVD, MBE or VPE, but is not limited thereto.

[0092] Preferably, in some embodiments, the P-type GaN layer is grown by MOCVD, with a growth temperature of 900 °C to 1000 °C and a growth pressure of 100 torr to 500 torr.

[0093] Correspondingly, the present invention also discloses a light-emitting diode, which includes the above-mentioned light-emitting diode epitaxial wafer. The light-emitting diode epitaxial wafer includes a substrate 100, a buffer layer 200, an intrinsic GaN layer 300, an N-type GaN layer 400, a multi-quantum well layer 500, an electron blocking layer 600, and a P-type GaN layer 700 that are sequentially stacked on the substrate 100. Among them, the multi-quantum well layer 500 is a periodic structure, and each period includes a pre-well protection layer 510, a quantum well layer 520, a post-well protection layer 530, and a quantum barrier layer 540 that are sequentially stacked; among them, the pre-well protection layer 510 includes an In x Ga 1-x N layer 511, an Al y Ga 1-y N layer 512, and an In z Ga 1-z N layer 513. The quantum well layer 520 is an In w Ga 1-w N layer. The post-well protection layer 530 includes an In α Ga 1-α N layer 531, an Al β Ga 1-β N layer 532, and an undoped GaN layer 533. The quantum barrier layer 540 is a GaN layer; x < z ≤ w, α ≤ w, y ≥ β; and along the growth direction of the light-emitting diode epitaxial wafer, z gradually increases, and α gradually decreases. Based on the above-mentioned light-emitting diode epitaxial wafer, on the one hand, InGaN layers with gradually increasing In composition are respectively arranged on both sides of the quantum well layer 520, namely In z Ga 1-z N layer 513 and InGaN layers with gradually decreasing In composition, namely In α Ga 1-αThe N-layer 531 can effectively reduce the lattice mismatch between the quantum well layer 520 (InGaN layer) and the quantum barrier layer 540 (GaN layer), weaken the compressive strain, which is beneficial to improving the radiative recombination efficiency and the light-emitting efficiency. Second, by setting Al on both sides of the quantum well layer 520 y Ga 1-y the N-layer 512 and Al β Ga 1-β the N-layer 532 can enhance the carrier confinement effect, significantly reduce the electron overflow phenomenon, and improve the light-emitting efficiency. Moreover, by controlling β < y, the blocking effect on holes can be weakened, the hole concentration in the quantum well layer 520 can be increased, and the radiative recombination efficiency can be improved. Third, the In in the pre-well protection layer 510 x Ga 1-x the N-layer 511 has a relatively small In component ratio (x < z ≤ w), which further optimizes the transition from the quantum barrier layer 540 to the quantum well layer 520 and weakens the compressive strain. In summary, the multi-quantum well layer 500 in this embodiment can significantly reduce electron overflow, increase the effective hole concentration, weaken the compressive strain, and thus effectively improve the radiative recombination efficiency of the multi-quantum well layer 500 and the light-emitting efficiency.

[0094] The following further illustrates the present invention with specific embodiments:

[0095] Embodiment 1

[0096] This embodiment provides a light-emitting diode epitaxial wafer, which includes a substrate, a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer that are sequentially stacked on the substrate.

[0097] Among them, the substrate is a sapphire substrate, the buffer layer is an AlN layer with a thickness of 50 nm. The thickness of the intrinsic GaN layer is 2.5 μm. The doping element of the N-type GaN layer is Si, and the doping concentration is 6×10 18 cm -3 , and its thickness is 3 μm.

[0098] Among them, the multi-quantum well layer is a periodic structure with 10 periods. Each period includes a pre-well protection layer, a quantum well layer, a post-well protection layer, and a quantum barrier layer that are sequentially stacked; the pre-well protection layer includes In x Ga 1-x the N-layer (x = 0.03), Al y Ga 1-y the N-layer and In z Ga 1-z the N-layer. The thickness of the In x Ga 1-x the N-layer is 0.4 nm. The thickness of the Al y Ga 1-yThe thickness of the N layer is 0.5 nm, the proportion (y) of its Al component is 0.1, and it remains constant. In z Ga 1-z The thickness of the N layer is 0.8 nm. Along the growth direction of the light-emitting diode epitaxial wafer, In z Ga 1-z The proportion of the In component in the N layer increases from 0.04 to 0.18. The quantum well layer is In w Ga 1-w N layer (w = 0.2), and its thickness is 3 nm. The post-well protection layer includes sequentially stacked In α Ga 1-α N layer, Al β Ga 1-β N layer and an undoped GaN layer. The thickness of the In α Ga 1-α N layer is 0.8 nm. Along the growth direction of the light-emitting diode epitaxial wafer, In α Ga 1-α The proportion of the In component in the N layer decreases from 0.15 to 0.03. The thickness of the Al β Ga 1-β N layer is 0.5 nm, the proportion (β) of its Al component is 0.08, and it remains constant. The thickness of the undoped GaN layer is 0.4 nm. The quantum barrier layer is a GaN layer with a thickness of 10 nm and a Si doping concentration of 3.8×10 17 cm -3 。

[0099] Among them, the electron blocking layer is an AlInGaN layer with an Al component proportion of 0.03, an In component proportion of 0.08, and a thickness of 30 nm. The thickness of the P-type GaN layer 700 is 180 nm, and its Mg doping concentration is 3×10 20 cm -3 。

[0100] In this embodiment, the method for preparing the light-emitting diode epitaxial wafer includes the following steps:

[0101] (1) Provide a substrate;

[0102] (2) Grow a buffer layer on the substrate;

[0103] Among them, grow an AlN layer by PVD as the buffer layer;

[0104] (3) Grow an intrinsic GaN layer on the buffer layer;

[0105] Among them, grow an intrinsic GaN layer by MOCVD, with a growth temperature of 1120 °C and a growth pressure of 200 torr.

[0106] (4) Grow an N-type GaN layer on the intrinsic GaN layer;

[0107] Among them, the N-type GaN layer is grown by MOCVD, and its growth temperature is 1140 °C and the growth pressure is 300 torr.

[0108] (5) Grow a multi-quantum well layer on the N-type GaN layer;

[0109] Specifically, grow a pre-well protection layer, a quantum well layer, a post-well protection layer, and a quantum barrier layer periodically by MOCVD until a multi-quantum well layer is obtained.

[0110] In x Ga 1-x The growth temperature of the N layer is 820 °C and the growth pressure is 200 torr; Al y Ga 1-y The growth temperature of the N layer is 910 °C and the growth pressure is 200 torr; In z Ga 1-z The growth temperature of the N layer is 790 °C and the growth pressure is 200 torr; In w Ga 1-w The growth temperature of the N layer is 770 °C and the growth pressure is 200 torr; In α Ga 1-α The growth temperature of the N layer is 800 °C and the growth pressure is 200 torr; Al β Ga 1-β The growth temperature of the N layer is 900 °C and the growth pressure is 200 torr; the growth temperature of the undoped GaN layer is 880 °C and the growth pressure is 200 torr; the growth temperature of the quantum barrier layer is 890 °C and the growth pressure is 30 torr to 360 torr.

[0111] (6) Grow an electron blocking layer on the multi-quantum well layer;

[0112] Specifically, grow an AlInGaN layer by MOCVD as the electron blocking layer, and its growth temperature is 930 °C and the growth pressure is 150 torr.

[0113] (7) Grow a P-type GaN layer on the electron blocking layer;

[0114] Specifically, grow a P-type GaN layer by MOCVD, and its growth temperature is 940 °C and the growth pressure is 400 torr.

[0115] Example 2

[0116] This example provides a light-emitting diode epitaxial wafer, and the difference from Example 1 is:

[0117] Along the growth direction of the light-emitting diode epitaxial wafer, Al y Ga 1-y In the Al β Ga 1-β N layer, the Al composition gradually increases from 0.03 to 0.11, and in the Al

[0118] Al composition in the GaN layer gradually decreases from 0.1 to 0.02.

[0119] Example 3

[0120] This example provides a light-emitting diode epitaxial wafer, which is different from that of Example 2 in that:

[0121] In x Ga 1-x Si is doped in the N layer, and the doping concentration is 5.5×10 17 cm -3 .

[0122] The rest are the same as those in Example 2.

[0123] Example 4

[0124] This example provides a light-emitting diode epitaxial wafer, which is different from that of Example 3 in that:

[0125] In x Ga 1-x After the growth of the InGaN layer is completed, annealing is performed in the first mixed gas, the annealing temperature is 950 °C, and the annealing pressure is 200 torr; the first mixed gas is a mixed gas of N 2 and H 2 , and the volume ratio of N 2 and H 2 is 1:5.

[0126] The rest are the same as those in Example 3.

[0127] Example 5

[0128] This example provides a light-emitting diode epitaxial wafer, which is different from that of Example 4 in that:

[0129] In α Ga 1-α After the growth of the InGaN layer is completed, annealing is performed in the second mixed gas, the annealing temperature is 840 °C, and the annealing pressure is 200 torr; the second mixed gas is a mixed gas of N 2 and NH 3 , and the volume ratio of N 2 and NH 3 is 1:1.5.

[0130] The rest are the same as those in Example 4.

[0131] Comparative Example 1

[0132] This comparative example provides a light-emitting diode epitaxial wafer, which is different from Example 1 in that:

[0133] The multi-quantum well layer does not include a pre-well protection layer and a post-well protection layer.

[0134] The rest are the same as those in Example 1.

[0135] Comparative Example 2

[0136] This comparative example provides a light-emitting diode epitaxial wafer, which is different from Example 1 in that:

[0137] The multi-quantum well layer does not include a pre-well protection layer.

[0138] The rest are the same as those in Example 1.

[0139] Comparative Example 3

[0140] This comparative example provides a light-emitting diode epitaxial wafer, which is different from Example 1 in that:

[0141] The multi-quantum well layer does not include a post-well protection layer.

[0142] The rest are the same as those in Example 1.

[0143] Comparative Example 4

[0144] This comparative example provides a light-emitting diode epitaxial wafer, which is different from Example 1 in that:

[0145] The pre-well protection layer does not include an In z Ga 1-z N layer, and the post-well protection layer does not include an In α Ga 1-α N layer.

[0146] The rest are the same as those in Example 1.

[0147] Comparative Example 5

[0148] This comparative example provides a light-emitting diode epitaxial wafer, which is different from Example 1 in that:

[0149] In z Ga 1-z The proportion of In component in the In

[0150] In α Ga 1-α GaN layer is 0.14 and remains constant;

[0151] The proportion of In component in the In

[0152] The light-emitting diode epitaxial wafers obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were made into chips of 10 mil × 24 mil, and their brightness at 200 mA was tested. Based on the data of Comparative Example 1, the brightness improvement rate was calculated.

[0153] Specifically, the brightness improvement rate = (the brightness of each example / comparative example - the brightness of Comparative Example 1) / the brightness of Comparative Example 1. The specific results are shown in the following table:

[0154]

[0155] The above are the preferred embodiments of the invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A light emitting diode epitaxial wafer, characterized in that: It comprises a substrate, a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer and a P-type GaN layer stacked in sequence on the substrate; the multi-quantum well layer is a periodic structure, and each period comprises a pre-well protection layer, a quantum well layer, a post-well protection layer and a quantum barrier layer stacked in sequence; The pre-well protection layer includes In x Ga 1-x N layer, Al y Ga 1-y N layer and In z Ga 1-z N layer, the quantum well layer is In w Ga 1-w N layer, the well back protection layer includes In α Ga 1-α N layer, Al β Ga 1-β N layer and non-doped GaN layer, the quantum barrier layer is a GaN layer; x<z≤w, α≤w, y≥β; and along the growth direction of the light emitting diode epitaxial wafer, z gradually increases and α gradually decreases.

2. The light emitting diode epitaxial wafer according to claim 1, characterized in that: Along the growth direction of the LED epitaxial wafer, y gradually increases and β gradually decreases; The maximum value of y is 0.15, and the maximum value of β is 0.

12.

3. The light emitting diode epitaxial wafer according to claim 1 or 2, characterized in that: Along the growth direction of the LED epitaxial wafer, the Al y Ga 1-y The Al component in the N layer gradually increases from y1 to y2. β Ga 1-β The Al component in the N layer gradually decreases from β1 to β2; y2>β1,y1>β2; The value range of y1 is 0.02~0.06, the value range of y2 is 0.06~0.15, the value range of β1 is 0.05~0.12, and the value range of β2 is 0.01~0.

06.

4. The light emitting diode epitaxial wafer according to claim 1, characterized in that: In x Ga 1-x The N layer is doped with Si, and the doping concentration is ≤1×10 18 cm -3 .

5. The light emitting diode epitaxial wafer according to claim 1, characterized in that: The period number of the multi-quantum well layer is 5 to 16; In x Ga 1-x The thickness of the N layer is 0.1nm~0.5nm, and the value of x ranges from 0.01~0.05; The Al y Ga 1-y The thickness of the N layer is 0.1nm~0.8nm, and the value of y ranges from 0.02~0.15; In z Ga 1-z The thickness of the N layer is 0.2nm~1nm, and the value of z ranges from 0.02~0.4; In w Ga 1-w The thickness of the N layer is 1.8nm~3.9nm, and the value of w ranges from 0.1 to 0.4; In α Ga 1-α The thickness of the N layer is 0.2nm~1nm, and the value range of α is 0.08~0.4; The Al β Ga 1-β The thickness of the N layer is 0.1nm~0.8nm, and the value range of β is 0.01~0.1; The thickness of the non-doped GaN layer is 0.1 nm to 0.5 nm; The quantum barrier layer is doped with Si, and its doping concentration is 2.5×10 17 cm -3 ~8.7×10 17 cm -3 , the thickness of the quantum barrier layer is 6nm~15nm.

6. A method for preparing a light emitting diode epitaxial wafer, for preparing the light emitting diode epitaxial wafer according to any one of claims 1 to 5, characterized in that: include: providing a substrate; A buffer layer, an intrinsic GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer and a P-type GaN layer are sequentially grown on the substrate; the multi-quantum well layer is a periodic structure, and each period includes a pre-well protection layer, a quantum well layer, a post-well protection layer and a quantum barrier layer stacked in sequence; The pre-well protection layer includes In x Ga 1-x N layer, Al y Ga 1-y N layer and In z Ga 1-z N layer, the quantum well layer is In w Ga 1-w N layer, the well back protection layer includes In α Ga 1-α N layer, Al β Ga 1-β N layer and non-doped GaN layer, the quantum barrier layer is a GaN layer; x<z≤w, α≤w, y≥β; and along the growth direction of the light emitting diode epitaxial wafer, z gradually increases and α gradually decreases.

7. The method for preparing a light emitting diode epitaxial wafer according to claim 6, characterized in that: In x Ga 1-x After the N layer is grown, annealing is performed in the first mixed gas to roughen its surface; The annealing temperature is 800° C. to 1050° C., and the annealing pressure is 30 torr to 360 torr; the first mixed gas is a mixed gas of N2 and H2, and the volume ratio of N2 to H2 is 1:0.13 to 1:8.

2.

8. The method for preparing a light emitting diode epitaxial wafer according to claim 6 or 7, characterized in that: In α Ga 1-α After the N layer is grown, it is annealed in the second mixed gas to improve its crystallization degree; The annealing temperature is 800° C. to 1050° C., and the annealing pressure is 30 torr to 360 torr; the second mixed gas is a mixed gas of N2 and NH3, and the volume ratio of N2 to NH3 is 1:0.2 to 1:5.

6.

9. The method for preparing a light emitting diode epitaxial wafer according to claim 6, characterized in that: In x Ga 1-x The growth temperature of the N layer is 750℃~920℃, and the growth pressure is 30torr~360torr; The Al y Ga 1-y The growth temperature of the N layer is 780℃~920℃, and the growth pressure is 30torr~360torr; In z Ga 1-z The growth temperature of the N layer is 680℃~890℃, and the growth pressure is 30torr~360torr; In w Ga 1-w The growth temperature of the N layer is 665℃~820℃, and the growth pressure is 30torr~360torr; In α Ga 1-α The growth temperature of the N layer is 680℃~890℃, and the growth pressure is 30torr~360torr; The Al β Ga 1-β The growth temperature of the N layer is 780℃~920℃, and the growth pressure is 30torr~360torr; The growth temperature of the non-doped GaN layer is 800° C. to 920° C., and the growth pressure is 30 torr to 360 torr; The growth temperature of the quantum barrier layer is 816° C. to 935° C., and the growth pressure is 30 torr to 360 torr.

10. A light emitting diode, characterized in that: It comprises the light emitting diode epitaxial wafer as described in any one of claims 1 to 5.

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