Epitaxial wafer and preparation method thereof
By cyclically stacking the generated silicon nitride seed layers in the N-type nitride composite layer of the semiconductor epitaxial sheet, the defects and performance reduction problems caused by the high-doped nitride layer are solved, and high-quality crystals and high-efficiency carrier injection is achieved, which improves the luminous brightness and reduces the growth cost.
Patent Information
- Application Number
- CN202311417737.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-30
- Publication Date
- 2025-05-02
AI Technical Summary
The existing semiconductor epitaxial sheets have a highly doped nitride layer during growth, resulting in defects, reduced leakage performance and reduced luminous brightness, and an additional low doped nitride layer is required to match, increasing growth cycle and cost.
The first sub-layer, seed layer and second sub-layer generated by alternately laminating from bottom to top in the N-type nitride composite layer, the seed layer is a silicon nitride layer, and Si atoms are used to provide Si atom diffusion, form carrier gradient differences, and improve carrier injection uniformity.
The crystal quality of the epitaxial sheet is improved, the dislocation defect extension is reduced, the carrier radiation recombination efficiency is improved, the leakage performance is reduced, the luminous brightness is improved, the growth process is simplified, and the cost is reduced.
Smart Images
Figure CN119923039A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor epitaxial technology, and in particular to an epitaxial wafer and its preparation method. Background Art
[0002] With the increasingly widespread application of semiconductor materials, the performance requirements for semiconductor materials and devices are constantly improving. Therefore, research on LED-related processes and structures is crucial for understanding materials and improving device performance and quality. In existing processes, SiNx mask technology is introduced during epitaxial growth. SiNx masks are used to reduce defects in nitride materials and improve crystal quality. However, the introduction of SiNx also causes changes in the strain, electrical, and optical properties of GaN thin films, requiring a matching epitaxial growth process to achieve excellent overall performance.
[0003] In existing processes, the N-type nitride layer in epitaxial wafer structures is typically highly doped. However, this highly doped nitride layer can create defects and leakage channels in the semiconductor layer, reducing the leakage performance of the epitaxial wafer. Furthermore, the highly doped nitride layer results in a high concentration of electrons on the light-emitting layer side, which mismatches with the low concentration of holes in the P-type nitride layer on the other side, reducing the brightness of the epitaxial wafer. To mitigate the impact of the highly doped N-type nitride layer on the light-emitting layer, a low-doped nitride layer is typically placed between the light-emitting layer and the N-type nitride layer. However, this technique does not improve the crystal quality or carrier optimization of the N-type layer itself. Epitaxial growth with a low-doped nitride layer results in a longer growth cycle, reduced growth efficiency, and increased growth costs.
[0004] Therefore, in order to solve these technical problems, we need to propose an effective method to improve these defects. Summary of the Invention
[0005] The purpose of this invention is to provide an epitaxial wafer and its preparation method, which can improve the crystal quality of the epitaxial wafer, reduce the extension of dislocation defects in the N-type nitride composite layer into the light-emitting layer, improve the carrier radiative recombination efficiency, reduce the leakage current performance of the epitaxial wafer, improve the luminescence brightness of the epitaxial wafer, improve the growth efficiency of the epitaxial wafer, and reduce the growth cost of the epitaxial wafer.
[0006] The objective of this invention is achieved through the following technical solution:
[0007] An epitaxial wafer, comprising:
[0008] Substrate;
[0009] An N-type nitride composite layer is located on the substrate. The N-type nitride composite layer includes a first sublayer, a seed layer, and a second sublayer that are cyclically and alternately stacked from bottom to top. The first sublayer and the second sublayer are N-type nitride sublayers. The seed layer is a silicon nitride layer. The Si atoms in the seed layer are used to provide Si atom diffusion to the second sublayer.
[0010] A light-emitting layer is located on the N-type nitride composite layer;
[0011] A P-type nitride layer is located on the light-emitting layer.
[0012] Preferably, the atomic ratio of Si to N in the seed layer is greater than 1;
[0013] Preferably, in the direction of the substrate toward the light-emitting layer, the ratio of Si to N atoms in each seed layer decreases sequentially.
[0014] Preferably, in the direction of the substrate toward the light-emitting layer, the thickness of each seed layer in the N-type nitride composite layer decreases sequentially;
[0015] Preferably, the seed layer has a nanoporous layered structure with a pore size of 10-50 nm.
[0016] Preferably, the thickness of the N-type nitride composite layer is 1–10 μm;
[0017] The thickness of the first sublayer in each layer is 50–500 nm, and the carrier concentration of the first sublayer is greater than that of the second sublayer.
[0018] The thickness of each seed layer is 1–10 nm;
[0019] The thickness of the second sublayer in each layer is 50–100 nm.
[0020] A method for preparing an epitaxial wafer, comprising:
[0021] Provide a substrate;
[0022] An N-type nitride composite layer is grown on the substrate. The N-type nitride composite layer includes a first sublayer, a seed layer, and a second sublayer that are stacked alternately from bottom to top. The first sublayer and the second sublayer are N-type nitride sublayers. The seed layer is a silicon nitride layer. The Si atoms in the seed layer are used to provide Si atom diffusion to the second sublayer.
[0023] A light-emitting layer is grown on the N-type nitride composite layer;
[0024] A P-type nitride layer is grown on the light-emitting layer.
[0025] Preferably, the atomic ratio of Si to N in the seed layer is greater than 1;
[0026] Preferably, in the direction of the substrate toward the light-emitting layer, the ratio of Si to N atoms in each seed layer decreases sequentially.
[0027] Preferably, in the direction of the substrate toward the light-emitting layer, the thickness of each seed layer in the N-type nitride composite layer decreases sequentially; preferably, the seed layer has a nanoporous layered structure, and the pore size of the nanoporous layered structure of the seed layer is 10-50 nm.
[0028] Preferably,
[0029] The growth temperature of the first sublayer is 900–1200℃, the growth pressure of the first sublayer is 50–650 torr, the thickness of each first sublayer is 50–500 nm, and the carrier concentration of the first sublayer is 2 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3 ;
[0030] The growth temperature of the seed layer is 900–1200℃, the growth pressure of the seed layer is 50–650 torr, and the thickness of each seed layer is 1–10 nm.
[0031] The growth temperature of the second sublayer is 900–1200℃, the growth pressure is 50–650 torr, the thickness of each second sublayer is 50–100 nm, and the carrier concentration of the second sublayer is 5 × 10⁻⁶. 16 cm -3 ~8×10 17 cm -3 .
[0032] Preferably, SiH4 and NH3 are introduced during the growth of the seed layer, with a SiH4 flow rate of 10-400 sccm and an NH3 flow rate of 20-100 slm, and the growth time of each seed layer is 60-600 s.
[0033] Preferably, the SiH4 to NH3 flow rate ratio is greater than 0.0001, and the ratio of the SiH4 to NH3 flow rate ratio when growing the previous seed layer and the SiH4 to NH3 flow rate ratio when growing the next adjacent seed layer is not less than 1.05:1 in the direction of the substrate toward the light-emitting layer.
[0034] Compared with the prior art, the beneficial effects of the present invention include at least:
[0035] The epitaxial wafer and its preparation method of the present invention generate an N-type nitride composite layer by cyclically stacking a first sublayer, a seed layer, and a second sublayer from bottom to top. The seed layer enhances the lateral epitaxial growth of N-type nitride, which not only improves the crystal quality of the epitaxial wafer but also reduces the extension of dislocation defects in the N-type nitride composite layer into the light-emitting layer, thereby improving the carrier radiative recombination efficiency and reducing the leakage current performance of the epitaxial wafer. The Si atoms in each seed layer of the N-type nitride composite layer introduce a carrier gradient difference in the direction from the substrate to the light-emitting layer, improving carrier injection in the N-type nitride composite layer and increasing the uniformity of carrier injection in the light-emitting layer, thereby improving the luminous brightness of the epitaxial wafer. In addition, the change in the concentration gradient of the N-type nitride composite layer in the direction from the substrate to the light-emitting layer is equivalent to realizing a low-doped nitride layer, eliminating the need for an additional low-doped nitride layer, improving the growth efficiency of the epitaxial wafer, and reducing the growth cost of the epitaxial wafer. Attached Figure Description
[0036] Figure 1 This is a cross-sectional structural diagram of an epitaxial wafer according to an embodiment of the present invention.
[0037] Figure 2 This is a cross-sectional structural diagram of another epitaxial wafer according to an embodiment of the present invention.
[0038] Figure 3 This is a schematic flowchart of the method for preparing an epitaxial wafer according to an embodiment of the present invention.
[0039] In the figure: 1. Substrate; 2. N-type nitride composite layer; 21. First sublayer; 22. Seed layer; 23. Second sublayer; 3. Light-emitting layer; 31. Quantum well layer; 32. Quantum barrier layer; 4. P-type nitride layer. Detailed Implementation
[0040] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.
[0041] The terms used to express position and direction in this invention are illustrated with the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this invention.
[0042] Reference Figures 1 to 2The present invention provides an epitaxial wafer, comprising: a substrate 1, an N-type nitride composite layer 2, a light-emitting layer 3, and a P-type nitride layer 4. The N-type nitride composite layer 2 is located on the substrate 1, the light-emitting layer 3 is located on the N-type nitride composite layer 2, and the P-type nitride layer 4 is located on the light-emitting layer 3.
[0043] Specifically, the substrate 1 can be made of materials such as sapphire, silicon, gallium nitride, or silicon carbide. In this embodiment, the substrate 1 is preferably sapphire. The N-type nitride composite layer 2 includes a first sublayer 21, a seed layer 22, and a second sublayer 23, which are cyclically and alternately stacked from bottom to top. The first sublayer 21 and the second sublayer 23 are N-type nitride sublayers, such as N-type GaN layers. The seed layer 22 is preferably a silicon nitride layer. The Si atoms in the seed layer 22 can be used to provide Si atom diffusion to the second sublayer 23, thereby increasing the electron concentration in the second sublayer 23.
[0044] The thickness of the N-type nitride composite layer 2 is 1 to 10 μm, for example, 2 μm, 4 μm, 6 μm, or 8 μm. The number of cycles of the first sublayer 21, the seed layer 22, and the second sublayer 23 can be set according to actual needs.
[0045] The thickness of each first sublayer 21 is 50–500 nm, for example, 100 nm, 200 nm, 250 nm, 300 nm, 400 nm, or 450 nm, and the carrier concentration of the first sublayer 21 is 2 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3 For example, 4×10 18 cm -3 , 8×10 18 cm -3 , 1×10 19 cm -3 , 3×10 19 cm -3 .
[0046] The thickness of each seed layer 22 is 1 to 10 nm, for example, 2 nm, 4 nm, 6 nm, or 8 nm.
[0047] The thickness of each second sublayer 23 is 50–100 nm, for example, 60 nm, 70 nm, 80 nm, or 90 nm, and the carrier concentration of the second sublayer 23 is 5 × 10⁻⁶. 16 cm -3 ~8×10 17 cm -3 For example, 7×10 16 cm -3 9×10 16 cm -3 , 1×1017 cm -3 , 3×10 17 cm -3 , 6×10 17 cm -3 .
[0048] The carrier concentration of the first sublayer 21 is greater than that of the second sublayer 23.
[0049] The seed layer 22 preferably has a nanoporous layered structure with a size of 10-50 nm. The silicon nitride layer exhibits discontinuous film formation characteristics at the micro-nano scale. The seed layer 22 is deposited on the first sub-layer 21. The method for depositing the seed layer 22 on the first sub-layer 21 can employ existing techniques and will not be elaborated here. The seed layer 22 can form a nanoporous layered structure. The second sub-layer 23 fills the nanopores of the nanoporous layered structure of the seed layer 22, and the second sub-layer 23 forms a flat surface with the seed layer 22. The seed layer 22 improves the lateral epitaxial growth of the N-type nitride sub-layer, improves the crystal quality of the N-type nitride sub-layer, reduces the extension of dislocation defects in the N-type nitride composite layer 2 into the light-emitting layer 3, improves the carrier radiative recombination efficiency, and reduces the leakage current performance of the epitaxial wafer.
[0050] The light-emitting layer 3 is preferably made of gallium nitride (GaN) material and is used for carrier recombination luminescence. The light-emitting layer 3 may comprise quantum well layers 31 and quantum barrier layers 32, which are stacked alternately from bottom to top. The number of times the quantum well layers 31 and quantum barrier layers 32 alternate is 2–20, for example, 3, 6, 9, 12, 15, or 18. The thickness of each quantum well layer 31 is 1–6 nm, for example, 2 nm, 3 nm, 4 nm, or 5 nm, and the thickness of each quantum barrier layer 32 is 6–18 nm, for example, 8 nm, 10 nm, 12 nm, 14 nm, or 16 nm.
[0051] The p-type nitride layer 4 is, for example, a p-type GaN layer, and it is grown on the light-emitting layer 3. The thickness of the p-type nitride layer 4 is 50–300 nm, for example, 100 nm, 150 nm, 200 nm, or 250 nm, and the carrier concentration of the p-type nitride layer 4 is 1 × 10⁻⁶. 17 cm -3 ~1×10 19 cm -3 For example, 6×10 17 cm -3 , 1×10 18 cm -3 , 6×10 18 cm -3 , 9×10 18 cm -3 .
[0052] Thus, an N-type nitride composite layer 2 is generated by cyclically stacking the first sublayer 21, seed layer 22, and second sublayer 23 from bottom to top. Seed layer 22 enhances the lateral epitaxial growth of the N-type nitride sublayer, which not only improves the crystal quality of the epitaxial wafer but also reduces the extension of dislocation defects in the N-type nitride composite layer 2 into the light-emitting layer 3, thereby improving the carrier radiative recombination efficiency and reducing the leakage current performance of the epitaxial wafer. The Si atoms in each seed layer 22 of the N-type nitride composite layer 2 can increase the electron concentration in the N-type nitride composite layer 2, which is equivalent to realizing a low-doped nitride layer without the need for an additional low-doped nitride layer. This improves the carrier injection in the N-type nitride composite layer 2 and enhances the carrier injection uniformity in the light-emitting layer 3, thereby improving the luminous brightness of the epitaxial wafer, while also improving the growth efficiency of the epitaxial wafer and reducing the growth cost of the epitaxial wafer.
[0053] In one specific embodiment, the atomic ratio of Si to N in the seed layer 22 is preferably greater than 1. In the direction from the substrate 1 to the light-emitting layer 3, the atomic ratio of Si to N in each seed layer 22 of the N-type nitride composite layer 2 decreases sequentially. As the atomic ratio of Si to N in the seed layer 22 decreases, the diffusion ability of Si atoms weakens, and the carrier concentration of the second sublayer 23 also decreases. In the direction from the substrate 1 to the light-emitting layer 3, the carrier concentration of the second sublayer 23 gradually decreases. The electron concentration in the N-type nitride composite layer 2 can be increased or decreased by increasing or decreasing the atomic ratio of Si to N in the seed layer 22.
[0054] In the direction from the substrate 1 toward the light-emitting layer 3, the thickness of each seed layer 22 in the N-type nitride composite layer 2 decreases sequentially, so that the ratio of Si to N atoms in each seed layer 22 in the N-type nitride composite layer 2 decreases sequentially. Alternatively, in the direction from the substrate 1 toward the light-emitting layer 3, by adjusting the Si flow rate, the ratio of Si to N atoms in each seed layer 22 in the N-type nitride composite layer 2 decreases sequentially.
[0055] In the direction from the substrate 1 toward the light-emitting layer 3, the ratio of Si to N atoms in each seed layer 22 of the N-type nitride composite layer 2 decreases sequentially, which has the following advantages:
[0056] On the one hand, a decreasing Si atom diffusion supply capability is formed in the direction of substrate 1 toward light-emitting layer 3, and a carrier concentration gradient is formed in the N-type nitride composite layer 2 in the direction of substrate 1 toward light-emitting layer 3, which improves the uniformity of carrier injection and enhances the capacitance effect of the epitaxial wafer, thereby improving the brightness and ESD performance of the epitaxial wafer.
[0057] On the other hand, the mask gradient difference in the seed layer 22 along the direction from the substrate 1 to the light-emitting layer 3 ensures sufficient stress release in the N-type nitride composite layer 2 along this direction. Because a thicker seed layer 22 results in greater mask coverage, a larger lateral epitaxial growth region, and a smaller window region, different stress regions can more easily achieve similar stress states through interaction. This leads to a more uniform stress distribution and less stress involvement in the N-type nitride composite layer 2. Therefore, the stress in the N-type nitride composite layer 2 closer to the substrate 1 is fully released, providing a low-stress growth template for the N-type nitride composite layer 2. Due to the difference in lattice constant between the substrate 1 and the N-type nitride composite layer 2, the stress generated during the growth process of the N-type nitride composite layer 2 is greater closer to the surface of the substrate 1. If the stress cannot be fully released, large stress will form inside the N-type nitride composite layer 2, affecting the performance of the epitaxial wafer. Therefore, more stress release is needed closer to the substrate 1.
[0058] Furthermore, the masking gradient difference of the seed layer 22 in the direction from the substrate 1 to the light-emitting layer 3 enhances the lateral epitaxial growth of the N-type nitride composite layer 2 closer to the substrate 1, improves the crystal quality of the N-type nitride composite layer 2, reduces the extension of dislocation defects in the N-type nitride composite layer 2 into the light-emitting layer 3, improves the carrier radiative recombination efficiency, and reduces the leakage performance of the LED epitaxial wafer. On the other hand, the masking capability of the N-type nitride composite layer 2 further away from the substrate 1 decreases, improving the surface flatness and obtaining a smooth surface of the N-type nitride composite layer 2, providing a growth template for the light-emitting layer 3, improving the thickness uniformity of the light-emitting layer 3, thereby improving the compositional uniformity and wavelength uniformity of the light-emitting layer 3.
[0059] It should be noted that, in the direction from the substrate 1 to the light-emitting layer 3, the ratio of Si to N atoms in each seed layer 22 of the N-type nitride composite layer 2 decreases sequentially. This does not only refer to the ratio of Si to N atoms in each seed layer 22, but also to the fact that the ratio of Si to N atoms in the seed layer 22 tends to decrease in the direction from the substrate 1 to the light-emitting layer 3.
[0060] Reference Figure 3 The present invention also provides a method for preparing an epitaxial wafer, comprising steps S1-S4.
[0061] Step S1: Provide a substrate 1.
[0062] Step S2: Grow an N-type nitride composite layer 2 on substrate 1.
[0063] Specifically, the N-type nitride composite layer 2 includes a first sublayer 21, a seed layer 22, and a second sublayer 23, which are stacked alternately from bottom to top. The thickness of the N-type nitride composite layer 2 is 1–10 μm, for example, 2 μm, 4 μm, 6 μm, or 8 μm. The number of cycles of the first sublayer 21, seed layer 22, and second sublayer 23 can be set according to actual needs. The first sublayer 21 and the second sublayer 23 are N-type nitride sublayers. The carrier concentration of the first sublayer 21 is greater than that of the second sublayer 23. The seed layer 22 is a silicon nitride layer, and the Si atoms in the seed layer 22 can be used to provide Si atom diffusion to the second sublayer 23. The atomic ratio of Si to N in the seed layer 22 is preferably greater than 1, for example, 1.3, 1.5, 1.8, 2.0, or 2.3. In the direction from the substrate 1 toward the light-emitting layer 3, the atomic ratio of Si to N in each seed layer 22 decreases sequentially. The seed layer 22 preferably has a nanoporous layered structure with a size of 10-50 nm.
[0064] Step S2 includes steps S21-S23.
[0065] Step S21: During the growth of the first sublayer 21, the carrier concentration of the first sublayer 21 is 2 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3 For example, 4×10 18 cm -3 , 8×10 18 cm -3 , 1×10 19 cm -3 , 3×10 19 cm -3 The growth temperature of the first sublayer 21 is 900–1200℃, for example, 950℃, 1000℃, 1050℃, 1100℃, or 1150℃. The growth pressure of the first sublayer 21 is 50–650 torr, for example, 100 torr, 200 torr, 300 torr, 400 torr, 500 torr, or 600 torr. The thickness of each first sublayer 21 is 50–500 nm, for example, 100 nm, 200 nm, 300 nm, or 400 nm.
[0066] Step S22: When growing seed layer 22, SiH4 and NH3 are introduced. The SiH4 flow rate is 100-400 sccm, for example, 150 sccm, 200 sccm, 250 sccm, 300 sccm, or 350 sccm. The NH3 flow rate is 20-100 slm, for example, 30 slm, 50 slm, 70 slm, or 90 slm. The growth time of each seed layer 22 is 60-600 s, for example, 100 s, 200 s, 300 s, 400 s, or 500 s.
[0067] As a preferred embodiment, the SiH4 to NH3 flow ratio is greater than 0.0001, and can be less than 0.02. In the direction from the substrate 1 towards the light-emitting layer 3, the ratio of the SiH4 to NH3 flow ratio during the growth of the previous seed layer 22 to the ratio during the growth of the next adjacent seed layer 22 is not less than 1.05:1. The Si to N atom ratio in each seed layer 22 of the N-type nitride composite layer 2 can be controlled by changing the SiH4 to NH3 flow ratio, and the thickness of each seed layer 22 can also be changed. Alternatively, the Si to N atom ratio in each seed layer 22 of the N-type nitride composite layer 2 can be controlled by changing the growth time of the seed layer 22, and the thickness of each seed layer 22 can also be changed.
[0068] The ratio of Si to N atoms in each seed layer 22 of the N-type nitride composite layer 2 is controlled by changing the SiH4 to NH3 flow rate ratio. Specifically, when growing the seed layer 22, the SiH4 to NH3 flow rate ratio in the growth environment is greater than 0.0001. In the direction from the substrate 1 to the light-emitting layer 3, the ratio of the SiH4 to NH3 flow rate ratio when growing the previous seed layer 22 and the ratio of the SiH4 to NH3 flow rate ratio when growing the next adjacent seed layer 22 is not less than 1.05:1. The growth time is 60s to 600s, for example, 100s, 200s, 300s, 400s, and 500s. The growth temperature of the seed layer 22 is 900–1200℃, for example 950℃, 1000℃, 1050℃, 1100℃, 1150℃. The growth pressure of the seed layer 22 is 50–650 torr, for example 100 torr, 200 torr, 300 torr, 400 torr, 500 torr, 600 torr. The thickness of each seed layer 22 is 1–10 nm, for example 2 nm, 4 nm, 6 nm, 8 nm. In the direction from the substrate 1 to the light-emitting layer 3, the thickness of each seed layer 22 in the N-type nitride composite layer 2 decreases sequentially.
[0069] Under specific NH3 flow rate conditions, the thickness of seed layer 22 is positively correlated with the SiH4 flow rate. By setting the SiH4 flow rate to decrease in the direction from substrate 1 to light-emitting layer 3, the thickness of seed layer 22 is reduced. At the same time, the SiH4 to NH3 flow rate ratio is set to ensure Si-rich process growth, which can achieve a decrease in the number of Si atoms in each seed layer 22. This results in a decrease in the Si atom diffusion supply capacity in the direction from substrate 1 to light-emitting layer 3. The N-type nitride composite layer 2 forms a carrier concentration gradient in the direction from substrate 1 to light-emitting layer 3, which improves the carrier injection uniformity and enhances the capacitance effect of the epitaxial wafer, thereby improving the brightness and ESD performance of the epitaxial wafer.
[0070] The growth time of the seed layer 22 is changed to control the ratio of Si to N atoms in each seed layer 22 in the N-type nitride composite layer 2. Specifically, when growing the seed layer 22, the SiH4 to NH3 flow rate ratio in the growth environment is greater than 0.0001, and the growth time is 60s to 600s, for example, 100s, 200s, 300s, 400s, and 500s. In the direction from the substrate 1 to the light-emitting layer 3, the growth time of the previous seed layer 22 and the next adjacent seed layer 22 decreases sequentially. The growth temperature of the seed layer 22 is 900–1200℃, for example 950℃, 1000℃, 1050℃, 1100℃, 1150℃. The growth pressure of the seed layer 22 is 50–650 torr, for example 100 torr, 200 torr, 300 torr, 400 torr, 500 torr, 600 torr. The thickness of each seed layer 22 is 1–10 nm, for example 2 nm, 4 nm, 6 nm, 8 nm. In the direction from the substrate 1 to the light-emitting layer 3, the thickness of each seed layer 22 in the N-type nitride composite layer 2 decreases sequentially.
[0071] Step S23: During the growth of the second sublayer 23, the carrier concentration of the second sublayer 23 is 5 × 10⁻⁶. 16 cm -3 ~8×10 17 cm -3 For example, 7×10 16 cm -3 , 9×10 16 cm -3 , 1×10 17 cm -3 , 3×10 17 cm -3 , 6×10 17 cm -3The growth temperature of the second sublayer 23 is 900–1200℃, for example 950℃, 1000℃, 1050℃, 1100℃, 1150℃. The growth pressure of the second sublayer 23 is 50–650 torr, for example 100 torr, 200 torr, 300 torr, 400 torr, 500 torr, 600 torr. The thickness of each second sublayer 23 is 50–100 nm, for example 60 nm, 70 nm, 80 nm, 90 nm.
[0072] Step S3: Grow a light-emitting layer 3 on the N-type nitride composite layer 2.
[0073] During the growth of the light-emitting layer 3, the light-emitting layer 3 comprises quantum well layers 31 and quantum barrier layers 32, which are stacked alternately from bottom to top. The number of times the quantum well layers 31 and quantum barrier layers 32 alternate is 2 to 20, for example, 3, 6, 9, 12, 15, or 18. The growth temperature of the quantum well layers 31 is 700 to 1150°C, for example, 800°C, 900°C, 1000°C, or 1100°C. The growth pressure of the quantum well layers 31 is 100 to 500 torr, for example, 150 torr, 200 torr, 300 torr, 350 torr, 400 torr, or 450 torr. The thickness of each quantum well layer 31 is 1 to 6 nm, for example, 2 nm, 3 nm, 4 nm, or 5 nm. The growth temperature of the quantum barrier layer 32 is 750–1200℃, for example, 800℃, 900℃, 1000℃, 1100℃. The growth pressure of the quantum barrier layer 32 is 100–500 torr, for example, 150 torr, 200 torr, 300 torr, 350 torr, 400 torr, 450 torr. The thickness of each quantum barrier layer 32 is 6–18 nm, for example, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm.
[0074] Step S4: Grow a P-type nitride layer 4 on the light-emitting layer 3.
[0075] When growing the p-type nitride layer 4, the growth temperature is 900–1200℃, for example, 950℃, 1000℃, 1050℃, 1100℃, and 1150℃; the growth pressure is 100–600 torr, for example, 200 torr, 300 torr, 400 torr, and 500 torr; the thickness of the p-type nitride layer 4 is 50–300 nm, for example, 100 nm, 150 nm, 200 nm, and 250 nm; and the carrier concentration of the p-type nitride layer 4 is 1 × 10⁻⁶. 17 cm -3 ~1×10 19 cm -3 For example, 6×1017 cm -3 , 1×10 18 cm -3 , 6×10 18 cm -3 9×10 18 cm -3 .
[0076] The present invention will be described in detail below with reference to embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.
[0077] In the following embodiments and comparative examples, the first sublayer 21 is an N-type GaN first sublayer 21, the second sublayer 23 is an N-type GaN second sublayer 23, the N-type nitride composite layer 2 is an N-type GaN composite layer, the seed layer 22 is a silicon nitride layer, the quantum well layer 31 is an InGaN quantum well layer 31, the quantum barrier layer 32 is a GaN quantum barrier layer 32, and the P-type nitride layer 4 is a P-type GaN layer, as an example.
[0078] Example 1
[0079] The preparation method of epitaxial wafers includes the following steps.
[0080] 1) Provide a sapphire substrate 1.
[0081] 2) On substrate 1, N-type GaN first sublayer 21, seed layer 22 and N-type GaN second sublayer 23 are cyclically stacked from bottom to top, and the cyclical alternation steps S21, S22 and S23 are repeated 10 times to obtain a 3.7 μm N-type GaN composite layer.
[0082] Step S21: Under conditions of 1000℃ and 200 torr, grow an N-type GaN first sublayer 21 on substrate 1. The carrier concentration of the N-type GaN first sublayer 21 is 4 × 10⁻⁶. 18 cm -3 The thickness of the first sublayer 21 of the N-type GaN is 300 nm.
[0083] Step S22: Under the conditions of temperature 1000℃ and pressure 200 torr, a seed layer 22 is grown on the first sublayer 21 of N-type GaN. The seed layer 22 is a silicon nitride layer. The growth time is 300s, the SiH4 flow rate is 320sccm, and the NH3 flow rate is 20slm.
[0084] Step S23: Under conditions of 1000℃ and 200 torr, grow an N-type GaN second sublayer 23 on the seed layer 22. The carrier concentration of the N-type GaN second sublayer 23 is 9 × 10⁻⁶. 16 cm -3The thickness of the second sublayer 23 of the N-type GaN is 70 nm.
[0085] In step S22, the initial SiH4 flow rate is 320 sccm, and the NH3 flow rate is 20 slm. During the cycle, the SiH4 flow rate is successively decreased, resulting in a SiH4 to NH3 flow rate ratio of 0.016, 0.014, 0.011, 0.010, 0.008, 0.006, 0.005, 0.004, 0.003, and 0.002. Under specific NH3 flow rate conditions, the thickness of the seed layer 22 is related to the SiH4 flow rate. By setting the SiH4 flow rate to decrease sequentially... The seed layer 22 is reduced in the direction from the substrate 1 toward the light-emitting layer 3. At the same time, the Si-rich process growth is ensured by setting the SiH4 to NH3 flow ratio. This allows for a decrease in the number of Si atoms in each seed layer 22, thereby creating a decrease in the Si atom diffusion supply capacity in the direction from the substrate 1 toward the light-emitting layer 3. The N-type GaN composite layer forms a carrier concentration gradient in the direction from the substrate 1 toward the light-emitting layer 3, improving the uniformity of carrier injection and enhancing the capacitance effect of the epitaxial wafer, thus improving the brightness and ESD performance of the epitaxial wafer.
[0086] 3) An InGaN quantum well layer 31 and a GaN quantum barrier layer 32 are cyclically stacked on the N-type GaN composite layer from bottom to top, with the number of cycles being 10, to obtain the light-emitting layer 3.
[0087] An InGaN quantum well layer 31 with a thickness of 4 nm was grown on an N-type GaN composite layer under conditions of 1000℃ and 300 torr.
[0088] A GaN quantum barrier layer 32 with a thickness of 12 nm was grown on an InGaN quantum well layer 31 under conditions of 1000℃ and 300 torr.
[0089] 4) A P-type GaN layer was grown on the light-emitting layer 3 at a temperature of 1000℃ and a pressure of 300 torr. The carrier concentration of the P-type GaN layer was 1×10⁻⁶. 18 cm -3 The thickness of the P-type GaN layer is 200 nm.
[0090] Comparative Example 1
[0091] 1) Provide a sapphire substrate 1.
[0092] 2) On substrate 1, N-type GaN first sublayer 21, seed layer 22 and N-type GaN second sublayer 23 are cyclically stacked from bottom to top, and the cyclical alternation steps S21, S22 and S23 are repeated 10 times to obtain a 3.7 μm N-type GaN composite layer.
[0093] Step S21: Under conditions of 1000℃ and 200 torr, an N-type GaN first sublayer 21 is grown on substrate 1. The carrier concentration of the N-type GaN first sublayer 21 is 4 × 10⁻⁶. 18 cm -3 The thickness of the first sublayer 21 of the N-type GaN is 300 nm.
[0094] Step S22: Under the conditions of temperature 1000℃ and pressure 200 torr, a seed layer 22 is grown on the first sublayer 21 of N-type GaN. The seed layer 22 is a silicon nitride layer. The growth time is 300s, the SiH4 flow rate is 320sccm, and the NH3 flow rate is 20slm.
[0095] Step S23: Under conditions of 1000℃ and 200 torr, grow an N-type GaN second sublayer 23 on the seed layer 22. The carrier concentration of the N-type GaN second sublayer 23 is 9 × 10⁻⁶. 16 cm -3 The thickness of the second sublayer 23 of the N-type GaN is 70 nm.
[0096] 3) An InGaN quantum well layer 31 and a GaN quantum barrier layer 32 are cyclically stacked on the N-type GaN composite layer from bottom to top, with the number of cyclical alternations being 10, to obtain the light-emitting layer 3.
[0097] An InGaN quantum well layer 31 with a thickness of 4 nm was grown on an N-type GaN composite layer under conditions of 1000℃ and 300 torr.
[0098] A GaN quantum barrier layer 32 with a thickness of 12 nm was grown on an InGaN quantum well layer 31 under conditions of 1000℃ and 300 torr.
[0099] 4) A P-type GaN layer was grown on the light-emitting layer 3 at a temperature of 1000℃ and a pressure of 300 torr. The carrier concentration of the P-type GaN layer was 1×10⁻⁶. 18 cm -3 The thickness of the P-type GaN layer is 200 nm.
[0100] Comparative Example 2
[0101] 1) Provide a sapphire substrate 1.
[0102] 2) On substrate 1, N-type GaN first sublayer 21 and N-type GaN second sublayer 23 are cyclically stacked from bottom to top, and the cyclical alternation steps S21 and S23 are repeated 10 times to obtain a 3.7μm N-type GaN composite layer.
[0103] Step S21: Under conditions of 1000℃ and 200 torr, grow an N-type GaN first sublayer 21 on substrate 1. The carrier concentration of the N-type GaN first sublayer 21 is 4 × 10⁻⁶. 18 cm -3 The thickness of the first sublayer 21 of the N-type GaN is 300 nm.
[0104] Step S23: Under conditions of 1000℃ and 200 torr, grow an N-type GaN second sublayer 23 on the seed layer 22. The carrier concentration of the N-type GaN second sublayer 23 is 9 × 10⁻⁶. 16 cm -3 The thickness of the second sublayer 23 of the N-type GaN is 70 nm.
[0105] 3) An InGaN quantum well layer 31 and a GaN quantum barrier layer 32 are cyclically stacked on the N-type GaN composite layer from bottom to top, with the number of cycles being 10, to obtain the light-emitting layer 3.
[0106] An InGaN quantum well layer 31 with a thickness of 4 nm was grown on an N-type GaN composite layer under conditions of 1000℃ and 300 torr.
[0107] A GaN quantum barrier layer 32 with a thickness of 12 nm was grown on an InGaN quantum well layer 31 under conditions of 1000℃ and 300 torr.
[0108] 4) A P-type GaN layer was grown on the light-emitting layer 3 at a temperature of 1000℃ and a pressure of 300 torr. The carrier concentration of the P-type GaN layer was 1×10⁻⁶. 18 cm -3 The thickness of the P-type GaN layer is 200 nm.
[0109] Comparative Example 3
[0110] 1) Provide a sapphire substrate 1.
[0111] 2) An N-type GaN first sublayer 21 is formed on substrate 1 to obtain a 3.7 μm GaN first sublayer 21.
[0112] An N-type GaN first sublayer 21 was grown on substrate 1 at a temperature of 1000℃ and a pressure of 200 torr. The carrier concentration of the N-type GaN first sublayer 21 was 4 × 10⁻⁶. 18 cm -3 .
[0113] 3) On the first sub-layer 21 of GaN, an InGaN quantum well layer 31 and a GaN quantum barrier layer 32 are cyclically stacked from bottom to top, with the number of cyclical alternations being 10, to obtain the light-emitting layer 3.
[0114] An InGaN quantum well layer 31 with a thickness of 4 nm was grown on the first sublayer 21 of GaN under conditions of 1000℃ and 300 torr.
[0115] A GaN quantum barrier layer 32 with a thickness of 12 nm was grown on an InGaN quantum well layer 31 under conditions of 1000℃ and 300 torr.
[0116] 4) A P-type GaN layer was grown on the light-emitting layer 3 at a temperature of 1000℃ and a pressure of 300 torr. The carrier concentration of the P-type GaN layer was 1×10⁻⁶. 18 cm -3 The thickness of the P-type GaN layer is 200 nm.
[0117] Comparative Example 4
[0118] 1) Provide a sapphire substrate 1.
[0119] 2) An N-type GaN second sublayer 23 is formed on substrate 1 to obtain a 3.7 μm GaN second sublayer 23.
[0120] Under conditions of 1000℃ and 200 torr, an N-type GaN second sublayer 23 was grown on the seed layer 22, with a carrier concentration of 9 × 10⁻⁶. 16 cm -3 .
[0121] 3) On the second sub-layer 23 of GaN, an InGaN quantum well layer 31 and a GaN quantum barrier layer 32 are cyclically stacked from bottom to top, with the number of cycles being 10, to obtain the light-emitting layer 3.
[0122] An InGaN quantum well layer 31 with a thickness of 4 nm was grown on the second sublayer 23 of GaN under conditions of 1000℃ and 300 torr.
[0123] A GaN quantum barrier layer 32 with a thickness of 12 nm was grown on an InGaN quantum well layer 31 under conditions of 1000℃ and 300 torr.
[0124] 4) A P-type nitride layer 4 was grown on the light-emitting layer 3 at a temperature of 1000℃ and a pressure of 300 torr. The carrier concentration of the P-type nitride layer 4 was 1×10⁻⁶.18 cm -3 The thickness of the P-type nitride layer 4 is 200 nm.
[0125] Comparative Example 5
[0126] 1) Provide a sapphire substrate 1.
[0127] 2) On substrate 1, N-type GaN first sublayer 21, seed layer 22 and N-type GaN second sublayer 23 are cyclically stacked from bottom to top, and the cyclical alternation steps S21, S22 and S23 are repeated 10 times to obtain a 3.7 μm N-type GaN composite layer.
[0128] Step S21: Under conditions of 1000℃ and 200 torr, an N-type GaN first sublayer 21 is grown on substrate 1. The carrier concentration of the N-type GaN first sublayer 21 is 4 × 10⁻⁶. 18 cm -3 The thickness of the first sublayer 21 of the N-type GaN is 300 nm.
[0129] Step S22: Under the conditions of temperature 1000℃ and pressure 200 torr, a seed layer 22 is grown on the first sublayer 21 of N-type GaN. The seed layer 22 is a silicon nitride layer, with a SiH4 flow rate of 320 sccm and an NH3 flow rate of 20 slm.
[0130] Step S23: Under conditions of 1000℃ and 200 torr, grow an N-type GaN second sublayer 23 on the seed layer 22. The carrier concentration of the N-type GaN second sublayer 23 is 9 × 10⁻⁶. 16 cm -3 The thickness of the second sublayer 23 of the N-type GaN is 70 nm.
[0131] In step S22, the growth time of each seed layer 22 is successively reduced to 550s, 500s, 450s, 400s, 350s, 300s, 250s, 200s, 150s, and 100s.
[0132] 3) An InGaN quantum well layer 31 and a GaN quantum barrier layer 32 are cyclically stacked on the N-type GaN composite layer from bottom to top, with the number of cyclical alternations being 10, to obtain the light-emitting layer 3.
[0133] An InGaN quantum well layer 31 with a thickness of 4 nm was grown on an N-type GaN composite layer under conditions of 1000℃ and 300 torr.
[0134] A GaN quantum barrier layer 32 with a thickness of 12 nm was grown on an InGaN quantum well layer 31 under conditions of 1000℃ and 300 torr.
[0135] 4) A P-type GaN layer was grown on the light-emitting layer 3 at a temperature of 1000℃ and a pressure of 300 torr. The carrier concentration of the P-type GaN layer was 1×10⁻⁶. 18 cm -3 The thickness of the P-type GaN layer is 200 nm.
[0136] Comparative Example 6
[0137] 1) Provide a sapphire substrate 1.
[0138] 2) On substrate 1, N-type GaN first sublayer 21, seed layer 22 and N-type GaN second sublayer 23 are cyclically stacked from bottom to top, and the cyclical alternation steps S21, S22 and S23 are repeated 10 times to obtain a 3.7 μm N-type GaN composite layer.
[0139] Step S21: Under conditions of 1000℃ and 200 torr, an N-type GaN first sublayer 21 is grown on substrate 1. The carrier concentration of the N-type GaN first sublayer 21 is 4 × 10⁻⁶. 18 cm -3 The thickness of the first sublayer 21 of the N-type GaN is 300 nm.
[0140] Step S22: Under the conditions of temperature 1000℃ and pressure 200 torr, a seed layer 22 is grown on the first sublayer 21 of N-type GaN. The seed layer 22 is a silicon nitride layer. The growth time is 300s, the SiH4 flow rate is 5sccm, and the NH3 flow rate is 100slm.
[0141] Step S23: Under conditions of 1000℃ and 200 torr, grow an N-type GaN second sublayer 23 on the seed layer 22. The carrier concentration of the N-type GaN second sublayer 23 is 9 × 10⁻⁶. 16 cm -3 The thickness of the second sublayer 23 of the N-type GaN is 70 nm.
[0142] 3) An InGaN quantum well layer 31 and a GaN quantum barrier layer 32 are cyclically stacked on the N-type GaN composite layer from bottom to top, with the number of cyclical alternations being 10, to obtain the light-emitting layer 3.
[0143] An InGaN quantum well layer 31 with a thickness of 4 nm was grown on an N-type GaN composite layer under conditions of 1000℃ and 300 torr.
[0144] A GaN quantum barrier layer 32 with a thickness of 12 nm was grown on an InGaN quantum well layer 31 under conditions of 1000℃ and 300 torr.
[0145] 4) A P-type GaN layer was grown on the light-emitting layer 3 at a temperature of 1000℃ and a pressure of 300 torr. The carrier concentration of the P-type GaN layer was 1×10⁻⁶. 18 cm -3 The thickness of the P-type GaN layer is 200 nm.
[0146] Comparative Example 7
[0147] 1) Provide a sapphire substrate 1.
[0148] 2) On substrate 1, N-type GaN first sublayer 21, seed layer 22 and N-type GaN second sublayer 23 are cyclically stacked from bottom to top, and the cyclical alternation steps S21, S22 and S23 are repeated 10 times to obtain a 3.7 μm N-type GaN composite layer.
[0149] Step S21: Under conditions of 1000℃ and 200 torr, an N-type GaN first sublayer 21 is grown on substrate 1. The carrier concentration of the N-type GaN first sublayer 21 is 4 × 10⁻⁶. 18 cm -3 The thickness of the first sublayer 21 of the N-type GaN is 300 nm.
[0150] Step S22: Under the conditions of temperature 1000℃ and pressure 200 torr, a seed layer 22 is grown on the first sublayer 21 of N-type GaN. The seed layer 22 is a silicon nitride layer. The growth time is 300s, the SiH4 flow rate is 500sccm, and the NH3 flow rate is 20slm.
[0151] Step S23: Under conditions of 1000℃ and 200 torr, grow an N-type GaN second sublayer 23 on the seed layer 22. The carrier concentration of the N-type GaN second sublayer 23 is 9 × 10⁻⁶. 16 cm -3 The thickness of the second sublayer 23 of the N-type GaN is 70 nm.
[0152] 3) An InGaN quantum well layer 31 and a GaN quantum barrier layer 32 are cyclically stacked on the N-type GaN composite layer from bottom to top, with the number of cyclical alternations being 10, to obtain the light-emitting layer 3.
[0153] An InGaN quantum well layer 31 with a thickness of 4 nm was grown on an N-type GaN composite layer under conditions of 1000℃ and 300 torr.
[0154] A GaN quantum barrier layer 32 with a thickness of 12 nm was grown on an InGaN quantum well layer 31 under conditions of 1000℃ and 300 torr.
[0155] 4) A P-type GaN layer was grown on the light-emitting layer 3 at a temperature of 1000℃ and a pressure of 300 torr. The carrier concentration of the P-type GaN layer was 1×10⁻⁶. 18 cm -3 The thickness of the P-type GaN layer is 200 nm.
[0156] Test results: Epitaxial wafers were prepared using Examples 1 and Comparative Examples 1-7. The brightness, voltage, and leakage current performance of epitaxial wafers with the same emission wavelength (450±0.5nm) were tested, as shown in Table 1.
[0157] Table 1
[0158]
[0159] in conclusion:
[0160] 1) As can be seen from the table above, Example 1 has higher brightness, lower voltage and excellent leakage performance. By comparing Comparative Example 1 and Example 1, although the leakage yield of Comparative Example 1 is comparable to that of Example 1, Comparative Example 1 has lower brightness and higher voltage. This indicates that although the fixed SiH4:NH3 ratio in the comparative example enhances the lateral epitaxial growth of N-type nitride and improves the crystal quality of the epitaxial wafer, it also reduces the leakage performance of the epitaxial wafer. However, Comparative Example 1 does not improve the carrier injection in the N-type nitride composite layer 2 or improve the carrier injection uniformity in the light-emitting layer 3.
[0161] 2) By comparing Example 1 and Comparative Example 5, although Comparative Example 5 also has relatively good leakage current performance, it indicates that the seed layer 22 enhances the lateral epitaxial growth of N-type nitride to a certain extent, improves the crystal quality of the epitaxial wafer, and reduces the leakage current performance of the epitaxial wafer. Although the brightness and voltage performance of Comparative Example 5 are improved compared with Comparative Example 1, it still has low brightness and high voltage compared with Example 1. This indicates that by reducing the seed layer 22 time in Comparative Example 5, the carrier injection in the N-type nitride composite layer can be improved, but the effect is not obvious.
[0162] 3) By comparing Example 1 and Comparative Example 6, the SiH4 to NH3 flow ratio of Comparative Example 6 is too small, and the seed layer 22 cannot fully utilize the Si atom diffusion supply, so the brightness is low, the voltage is high, and the leakage current yield is also worse.
[0163] 4) By comparing Example 1 and Comparative Example 7, the SiH4 to NH3 flow ratio of Comparative Example 7 is too large. While the seed layer 22 provides Si atom diffusion supply, too many Si atoms are formed as dopants at the interface of the seed layer 22, forming dislocation nucleation points and dislocation extension, so the brightness and leakage current performance deteriorate.
[0164] 5) By comparing Example 1 and Comparative Example 2, Comparative Example 2, without seed layer 22, showed worse brightness, leakage current, and voltage compared to Example 1. This indicates that without seed layer 22, the lateral epitaxial growth of N-type nitride cannot be enhanced, resulting in a decrease in the crystal quality of the epitaxial wafer. Moreover, it does not improve the carrier injection in the N-type nitride composite layer 2.
[0165] 6) By comparing Example 1 and Comparative Example 3, although Comparative Example 3 can obtain relatively low voltage performance, its brightness and leakage performance are poor, indicating that the crystal quality of the epitaxial wafer in Comparative Example 3 is poor and the light-emitting layer has a high number of non-radiative coincidence centers.
[0166] 7) By comparing Example 1 and Comparative Example 4, the brightness, leakage current and voltage of Example 1 are worse than those of Example 1, indicating that the crystal quality of the epitaxial wafer in Comparative Example 4 is poor and the light-emitting layer has a high number of non-radiative coincidence centers.
[0167] In summary, the seed layer 22 of this invention enhances the lateral epitaxial growth of N-type nitrides, which not only improves the crystal quality of the epitaxial wafer but also reduces the extension of dislocation defects in the N-type nitride composite layer 2 into the light-emitting layer 3, thereby improving the carrier radiative recombination efficiency and reducing the leakage current performance of the epitaxial wafer. The Si atoms in each seed layer 22 of the N-type nitride composite layer 2 can increase the electron concentration in the N-type nitride composite layer 2, which is equivalent to realizing a low-doped nitride layer without the need for an additional low-doped nitride layer. This improves the carrier injection in the N-type nitride composite layer 2 and enhances the carrier injection uniformity in the light-emitting layer 3, thereby improving the luminous brightness of the epitaxial wafer.
[0168] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the invention without departing from the principles and spirit of the invention, and all such changes should fall within the protection scope of the claims of the present invention.
Claims
1. An epitaxial wafer, characterized in that: include: substrate; An N-type nitride composite layer, located on the substrate, the N-type nitride composite layer comprises a first sublayer, a seed layer, and a second sublayer generated by cyclically and alternately stacking from bottom to top, the first sublayer and the second sublayer are N-type nitride sublayers, the seed layer is a silicon nitride layer, and Si atoms in the seed layer are used to provide Si atom diffusion for the second sublayer; A light-emitting layer, located on the N-type nitride composite layer; The P-type nitride layer is located on the light-emitting layer.
2. An epitaxial wafer as claimed in claim 1, characterized in that: The atomic ratio of Si to N in the seed layer is greater than 1; Preferably, in the direction from the substrate to the light-emitting layer, the ratio of Si to N atoms in each seed layer decreases successively.
3. An epitaxial wafer as claimed in claim 2, characterized in that: In the direction from the substrate to the light-emitting layer, the thickness of each seed layer in the N-type nitride composite layer decreases in sequence; Preferably, the seed layer has a nanoporous layered structure, and the pore size of the nanoporous layered structure of the seed layer is 10-50 nm.
4. An epitaxial wafer as claimed in claim 1, characterized in that: The thickness of the N-type nitride composite layer is 1 to 10 μm; The thickness of each first sublayer is 50-500 nm, and the carrier concentration of the first sublayer is greater than the carrier concentration of the second sublayer; The thickness of each seed layer is 1 to 10 nm; The thickness of each second sublayer is 50-100 nm.
5. A method for preparing an epitaxial wafer, characterized in that: include: providing a substrate; Growing an N-type nitride composite layer on the substrate, the N-type nitride composite layer comprising a first sublayer, a seed layer, and a second sublayer generated by cyclically and alternately stacking from bottom to top, the first sublayer and the second sublayer being N-type nitride sublayers, the seed layer being a silicon nitride layer, and Si atoms in the seed layer being used to provide Si atom diffusion for the second sublayer; Growing a light-emitting layer on the N-type nitride composite layer; A P-type nitride layer is grown on the light emitting layer.
6. The method for preparing an epitaxial wafer according to claim 5, characterized in that: The atomic ratio of Si to N in the seed layer is greater than 1; Preferably, in the direction from the substrate to the light-emitting layer, the ratio of Si to N atoms in each seed layer decreases successively.
7. The method for preparing an epitaxial wafer according to claim 5, characterized in that: In the direction from the substrate to the light-emitting layer, the thickness of each seed layer in the N-type nitride composite layer decreases successively; preferably, the seed layer has a nanoporous layered structure, and the pore size of the nanoporous layered structure of the seed layer is 10-50nm.
8. The method for preparing an epitaxial wafer according to claim 5, characterized in that: The growth temperature of the first sublayer is 900-1200° C., the growth pressure of the first sublayer is 50-650 torr, the thickness of each first sublayer is 50-500 nm, and the carrier concentration of the first sublayer is 2×10 18 cm -3 ~5×10 19 cm -3 ; The growth temperature of the seed layer is 900-1200° C., the growth pressure of the seed layer is 50-650 torr, and the thickness of each seed layer is 1-10 nm; The growth temperature of the second sublayer is 900-1200° C., the growth pressure of the second sublayer is 50-650 torr, the thickness of each second sublayer is 50-100 nm, and the carrier concentration of the second sublayer is 5×10 16 cm -3 ~8×10 17 cm -3 .
9. The method for preparing an epitaxial wafer according to claim 5, characterized in that: When growing the seed layer, SiH4 and NH3 are introduced, the flow rate of SiH4 is 10-400 sccm, the flow rate of NH3 is 20-100 slm, and the growth time of each seed layer is 60s-600s.
10. The method for preparing an epitaxial wafer according to claim 9, characterized in that: The flow ratio of SiH4 to NH3 is greater than 0.0001, and in the direction from the substrate toward the light-emitting layer, the ratio of the flow ratio of SiH4 to NH3 when growing the previous seed layer and the flow ratio of SiH4 to NH3 when growing the next adjacent seed layer is not less than 1.05:1.