Light-emitting diode epitaxial wafer with double gradient electron limiting layers and preparation method of light-emitting diode epitaxial wafer

Abstract

The invention discloses a light-emitting diode epitaxial wafer with a double-gradient electron limiting layer and a preparation method of the light-emitting diode epitaxial wafer. According to the epitaxial wafer, an electron limiting layer composed of three n-type AlGaN sub-layers is arranged between an n-type GaN layer and an active layer. The average Al component and Si doping concentration between the sub-layers are increased in a stepped manner, and the Al component and the Si in each sub-layer are increased in a continuous gradient manner along the growth direction. According to the invention, the Al component gradient is utilized to construct an electron deceleration barrier, the electron drift speed is reduced, and the carrier capture probability is improved; the Si concentration gradient is matched to compensate the resistivity rise and the DX center effect caused by the high Al component, the increase of the working voltage is avoided, meanwhile, the structure can induce dislocation bending, and the crystal quality of the epitaxial layer is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic materials and device manufacturing technology, and in particular to a light-emitting diode epitaxial wafer with a dual-gradient electron confinement layer and its preparation method. Background Technology

[0002] Group III nitride semiconductors (GaN, InN, AlN, and their alloys) are core materials for manufacturing short-wavelength light-emitting devices (such as blue, green, and ultraviolet LEDs and lasers). Currently, mainstream commercial GaN-based LED epitaxial wafer structures are typically grown on sapphire, silicon carbide, or silicon substrates. Their basic structure includes: a low-temperature buffer layer, an undoped GaN layer (u-GaN), an n-type GaN layer (n-GaN), an InGaN / GaN multiple quantum well active region (MQW), a p-type AlGaN electron blocking layer (EBL), and a p-type GaN layer (p-GaN).

[0003] Although GaN-based LEDs have achieved large-scale commercialization, their external quantum efficiency (EQE) drops significantly at high current densities, a phenomenon known as "efficiency degradation." Both academia and industry generally agree that low carrier injection efficiency and electron leakage are the key factors causing this problem.

[0004] Specifically, the existing technology has the following main drawbacks: A severe mismatch exists between electron and hole transport characteristics: In GaN materials, electron mobility is typically 400-1000 cm² / (V·s), while hole mobility is typically only 10-20 cm² / (V·s). Under forward bias, electrons are injected into the active region at extremely high speeds, while hole injection is slow. This results in a large number of high-energy electrons leaking into the p-type region without recombinating with holes, thus reducing internal quantum efficiency. Furthermore, the leaked electrons generate Joule heating, accelerating device aging.

[0005] Limitations of traditional electron blocking layers (EBLs): To suppress electron leakage, existing techniques typically introduce p-AlGaN EBLs with high Al content on the p-side (after the active region). However, the large valence band barrier of the EBL also hinders hole injection. Furthermore, the extremely low activation efficiency of Mg in AlGaN leads to high EBL resistivity, increasing the device's operating voltage.

[0006] High dislocation density due to heteroepitaxial growth: A large lattice mismatch (~13.8%) exists between GaN and the sapphire substrate, resulting in a high density of penetrating dislocations in the epitaxial layer. These dislocations penetrate the n-GaN layer into the active region, forming non-radiative recombination centers, which severely reduces luminescence efficiency.

[0007] To address these issues, while some studies have proposed introducing superlattice structures on the n-side to alleviate stress, traditional constant-composition superlattices have limited ability to regulate electron kinetic energy, and frequent interface switching easily introduces interface state defects. Therefore, a novel epitaxial structure design is urgently needed that can actively "decelerate" and "homogenize" electrons on the n-side while simultaneously improving crystal quality. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a light-emitting diode epitaxial wafer with a dual-gradient electron confinement layer and its fabrication method. This method achieves effective electron deceleration and uniform distribution by introducing an electron confinement layer with a specific Al composition and Si doping concentration "dual gradient" after an n-type GaN layer, reducing dislocation density and thus improving the luminous efficiency of the LED while maintaining a low operating voltage.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A light-emitting diode epitaxial wafer with a dual-gradient electron confinement layer, comprising: The substrate, buffer layer, undoped GaN layer, n-type GaN layer, electron confinement layer, active layer, electron blocking layer and p-type GaN layer are stacked sequentially along the growth direction. The electron confinement layer is located between the n-type GaN layer and the active layer, and is composed of a first electron confinement layer, a second electron confinement layer and a third electron confinement layer stacked sequentially. The first electron confinement layer, the second electron confinement layer, and the third electron confinement layer are all Si-doped n-type AlGaN layers; The electron confinement layer has a dual gradient structure in terms of Al composition and Si doping concentration: Regarding Al composition: the average Al composition of the first electron confinement layer, the second electron confinement layer, and the third electron confinement layer increases sequentially; and within each electron confinement layer, the Al composition exhibits a continuous gradient distribution along the direction away from the substrate. Regarding the Si doping concentration: the average Si doping concentration of the first electron confinement layer, the second electron confinement layer and the third electron confinement layer increases sequentially; and within each electron confinement layer, the Si doping concentration is distributed in a continuous gradient increasing direction away from the substrate.

[0010] The Al composition distributions of the first, second, and third electron confinement layers satisfy the following conditions: The first electron confinement layer is wherein the Al composition increases linearly from 0.01~0.02 to 0.03~0.05 from the bottom surface to the top surface of the first electron confinement layer; The second electron confinement layer is wherein the Al composition increases linearly from 0.05~0.06 to 0.08~0.10 from the bottom surface to the top surface of the second electron confinement layer; The third electron confinement layer is wherein the Al composition increases linearly from 0.10~0.12 to 0.14~0.15 from the bottom surface to the top surface of the third electron confinement layer; In this design, the Al composition of the top surface of the first electron confinement layer is smaller than that of the bottom surface of the second electron confinement layer, and the Al composition of the top surface of the second electron confinement layer is smaller than that of the bottom surface of the third electron confinement layer, thereby forming an Al composition step at the interface of adjacent electron confinement layers.

[0011] The Si doping concentration distributions of the first, second, and third electron confinement layers satisfy the following condition: The Si doping concentration of the first electron confinement layer is from 1×10 17 atoms / cm 3 Rising continuously to 5×10 17 atoms / cm 3 ; The Si doping concentration of the second electron confinement layer is from 5 × 10⁻⁶. 17 atoms / cm 3 Rising continuously to 1×10 18 atoms / cm 3 ; The Si doping concentration of the third electron confinement layer is from 1×10⁻⁶. 18 atoms / cm 3 Rising continuously to 5×10 18 atoms / cm 3 .

[0012] The thicknesses of the first electron confinement layer, the second electron confinement layer, and the third electron confinement layer are all between 10 nm and 200 nm.

[0013] The active layer comprises alternating layers of InGaN quantum wells and GaN quantum barriers; The top surface of the third electron confinement layer is in direct contact with the first quantum barrier layer of the active layer; or, an undoped GaN stress relief layer is sandwiched between the third electron confinement layer and the active layer.

[0014] The substrate is a patterned substrate, and a three-dimensional nucleation layer is also included between the substrate and the undoped GaN layer.

[0015] The above-mentioned method for fabricating an epitaxial wafer of a light-emitting diode includes the following steps: A substrate is provided on which a buffer layer, an undoped GaN layer, and an n-type GaN layer are sequentially grown. The electron confinement layer is grown on the n-type GaN layer; An active layer, an electron blocking layer, and a p-type GaN layer are grown on the electron confinement layer; The step of growing the electron confinement layer includes: maintaining a reaction chamber pressure of 50 Torr to 300 Torr, and either linearly increasing the flow rate of trimethylaluminum (TMAl) while keeping the gallium source flow rate constant, or linearly decreasing the gallium source flow rate while keeping the trimethylaluminum (TMAl) flow rate constant, to form a continuous gradient increase of the Al composition. Furthermore, during the growth of the electron confinement layer, the flow rate of silane (SiH4) gas is continuously increased according to a preset linear slope to form a continuous gradient increase in Si doping concentration.

[0016] The atmosphere during the growth of the electron confinement layer includes N2, H2 and NH3, wherein the volumetric flow rate ratio of N2:H2:NH3 is from 1:1:1 to 1:5:10.

[0017] Analysis of the beneficial effects and physical mechanisms of the present invention: Electronic multi-stage deceleration mechanism: Unlike traditional single potential barriers, the three-layer stepped potential barrier of this invention is like multiple "speed bumps" on a highway. As the Al composition increases with each layer, the bottom energy level of the conduction band gradually rises. When high-speed injected electrons pass through each layer, their kinetic energy is partially converted into potential energy or dissipated through phonon scattering. By the time they reach the active region, the electron velocity has significantly decreased, thereby increasing their capture cross-section in the quantum well and drastically reducing the probability of electrons escaping to the p-region.

[0018] Polarization doping and band smoothing: By employing an Al composition gradient within each sublayer, polarization charges are generated inside the crystal. The built-in electric field generated by these polarization charges can "smooth out" the sharp band bends caused by abrupt changes in the heterojunction, making electron transport smoother and preventing carrier accumulation at the interface, thus achieving a "deceleration without blocking" effect.

[0019] Precise compensation of electrical performance: Typically, increasing the Al content leads to an increase in the resistivity of AlGaN materials (due to increased effective electron mass and deeper donor levels). Furthermore, at high Al contents, Si donors readily form DX centers (deep-level defects), resulting in carrier quenching. This invention innovatively designs a mechanism for a synchronous gradient of Si concentration with Al content. In the third layer, where the Al content is highest, the Si doping concentration reaches an extremely high 5 × 10⁻⁶. 18 atoms / cm -3High concentrations of doping not only compensate for electrons trapped by the DX center, but also significantly reduce the depletion layer width of the barrier, allowing electrons to pass through the high barrier region via thermally assisted tunneling. This limits electron velocity while ensuring that the forward operating voltage (Vf) of the device does not increase, thus maintaining high electro-optical conversion efficiency.

[0020] Suppression of dislocation density: The gradient composition AlGaN layer is essentially a stress-gradient layer. Due to the difference in lattice constants between AlN (a=3.11Å) and GaN (a=3.19Å), the gradient change in Al composition introduces distributed compressive stress within the epitaxial layer. This stress field can generate lateral forces on penetrating dislocations, inducing dislocation lines to bend or merge and annihilate, thereby blocking their extension into the active region and significantly improving the crystal quality of the active region. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view of the layered structure of the epitaxial wafer of the light-emitting diode provided in an embodiment of the present invention.

[0022] Explanation of key component symbols: 100: Patterned substrate 200: Buffer layer 300: Undoped GaN layer 400: n-type GaN layer 500: Electron Confinement Layer 510: First electron confinement layer 520: Second Electron Confinement Layer 530: Third Electron Confinement Layer 600: Active Layer 610: Quantum well layer 620: Quantum Barrier Layer 700: Electron blocking layer 800: p-type GaN layer. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1 As shown, the present invention provides a light-emitting diode epitaxial wafer with a dual-gradient electron confinement layer, which includes, in sequence along the growth direction: a patterned substrate 100, a buffer layer 200, an undoped GaN layer 300, an n-type GaN layer 400, an electron confinement layer 500, an active layer 600, an electron blocking layer 700, and a p-type GaN layer 800.

[0025] The electron confinement layer 500 is located between the n-type GaN layer 400 and the active layer 600, and plays a role in regulating electron kinetic energy, suppressing electron leakage, and filtering dislocations. The electron confinement layer 500 is not a single-component structure, but rather consists of three layers stacked sequentially: a first electron confinement layer 510, a second electron confinement layer 520, and a third electron confinement layer 530. All three layers are Si-doped n-type AlGaN materials, and structurally possess a unique "dual gradient" characteristic: that is, there is an increase in Al composition and Si doping concentration between layers, and simultaneously, within each sublayer, there is a continuous gradient increase in Al composition and Si doping concentration along the growth direction.

[0026] The structural parameters and fabrication process of the epitaxial wafer are illustrated below through a specific fabrication example.

[0027] Example 1

[0028] In this embodiment, the fabrication is carried out in an MOCVD reaction chamber, and the structure of the fabricated light-emitting diode epitaxial wafer is as follows: 1. Substrate and base layer growth: First, a patterned substrate 100 is processed, and a buffer layer 200 is grown on the patterned substrate 100. Subsequently, an undoped GaN layer 300 is grown on the buffer layer 200, followed by an n-type GaN layer 400. The n-type GaN layer 400 provides the main channel for electrons.

[0029] 2. Growth of electron confinement layer 500: After the n-type GaN layer 400 is grown, the reaction chamber conditions are adjusted to grow the electron confinement layer 500. Specifically, the process conditions are controlled as follows: the deposition pressure is maintained at 150 Torr, and the deposition atmosphere consists of N2, H2, and NH3, with a N2:H2:NH3 volumetric flow rate ratio of 1:3:6. Under this environment, three sublayers are grown sequentially: First electron confinement layer 510: It is grown directly on top of an n-type GaN layer 400. This layer is an n-type Al. x Ga 1-x The N-layer was constructed with a thickness controlled at 100 nm. During growth, the Al composition x was linearly increased from 0.01 to 0.03 along the growth direction by linearly increasing the trimethylaluminum (TMAl) flow rate. Simultaneously, the Si doping concentration was linearly increased from 1 × 10⁻⁶ along the growth direction by linearly increasing the silane (SiH₄) flow rate. 17 atoms / cm 3 Continuously linearly increased to 3×10 17 atoms / cm 3 .

[0030] Second electron confinement layer 520: Grows on top of the first electron confinement layer 510. This layer is an n-type Al y Ga 1-y N layer with a thickness controlled to be 100 nm. During growth, the Al composition y linearly increases continuously from 0.05 to 0.08 along the growth direction; the Si doping concentration linearly increases continuously from 5×10 17 atoms / cm 3 to 8×10 17 atoms / cm 3 .

[0031] It should be noted that the Al composition (0.03) on the top surface of the first electron confinement layer 510 is less than the Al composition (0.05) on the bottom surface of the second electron confinement layer 520, thus forming a step in the Al composition at the interface between the two layers.

[0032] Third electron confinement layer 530: Grows on top of the second electron confinement layer 520. This layer is an n-type Al z Ga 1-z N layer with a thickness controlled to be 100 nm. During growth, the Al composition z linearly increases continuously from 0.1 to 0.15 along the growth direction; the Si doping concentration linearly increases continuously from 1×10 18 atoms / cm 3 to 3×10 18 atoms / cm 3 .

[0033] Similarly, the Al composition (0.08) on the top surface of the second electron confinement layer 520 is less than the Al composition (0.1) on the bottom surface of the third electron confinement layer 530, and an Al composition step is also formed at this interface.

[0034] Through the above steps, an electron confinement layer 500 with an increasing Al composition (x < y < z) between layers and a continuous gradient within the layer is constructed. This stepped-up barrier structure is like a multi-level "speed bump", effectively reducing the drift velocity of electrons and increasing the probability of their being captured by the active layer 600; while the synchronously designed Si concentration gradient effectively compensates for the increase in resistivity and the DX center effect caused by the high Al composition, preventing the increase in the operating voltage.

[0035] 3. Light-emitting structure and P-side growth: Subsequently, an active layer 600 is grown on the third electron confinement layer 530. The active layer 600 includes alternating quantum well layers 610 and quantum barrier layers 620. Due to the presence of the electron confinement layer 500, electrons can be injected more uniformly into each quantum well layer 610. Finally, an electron blocking layer 700 and a p-type GaN layer 800 are sequentially grown on the active layer 600 to complete the fabrication of the entire epitaxial wafer.

[0036] In another embodiment, in order to further alleviate stress, a low-temperature u-GaN layer with a thickness of 10-30 nm is first grown on the third electron confinement layer 530 as a stress relief layer before the active layer 600 is grown.

[0037] The epitaxial wafer prepared in this embodiment effectively reduces the dislocation density and improves the crystal quality of the epitaxial layer by introducing the electron confinement layer 500 with the above-mentioned specific structure, and significantly improves the recombination efficiency of charge carriers in the active layer 600, thereby improving the luminous efficiency and electro-optical conversion efficiency of the light-emitting diode.

[0038] Testing and Verification: The prepared epitaxial wafer was processed to form a 15μm×30μm LED chip.

[0039] XRD test: The FWHM curves of the (002) and (102) surfaces are 92 arcsec and 168 arcsec, respectively, which are better than the 114 / 196 arcsec of the conventional structure, proving that the gradient ECL effectively filters out dislocations.

[0040] Photoelectric performance: At an injection current of 150 mA, the light output power (LOP) of Example 1 was increased by 3% compared to the control without ECL; the operating voltage (Vf) increased by only 0.1%, which was almost negligible. This confirms the voltage compensation effect of Si gradient doping and the effect of electron deceleration on improving optical efficiency.

[0041] To further verify the universality and effectiveness of the dual-gradient electron confinement layer proposed in this invention under different structural parameters, and to explore the effects of layer thickness, Al composition gradient and Si doping concentration on device performance, the inventors designed and prepared multiple sets of experimental samples (conditions 1 to 5) based on the preparation process of Example 1, while keeping the basic growth conditions such as reaction chamber pressure, growth temperature and atmosphere ratio (N2:H2:NH3) consistent, by adjusting the growth time and source flow rate ratio.

[0042] Meanwhile, to visually demonstrate the beneficial effects of the technical solution of this invention, a set of comparative examples (conventional structures) was also set up in this experiment. After growing the n-type GaN layer, the comparative examples did not grow the dual-gradient electron confinement layer of this invention, but directly grew the active layer, and the structure and growth process of the remaining layers were consistent with those of Example 1.

[0043] The specific parameter adjustment instructions for each experimental group are as follows: Condition 1: The specific parameters corresponding to Embodiment 1 above are used as the basic reference group for this invention.

[0044] Conditions 2 and 3: These mainly examine the effect of thickness variation. While keeping the Al composition and Si doping concentration gradient constant, the thicknesses of the first, second, and third electron confinement layers are reduced (condition 2) and increased (condition 3), respectively, to verify the effect of thickness on dislocation filtering and voltage.

[0045] Conditions 4 and 5 primarily examine the influence of the Al composition gradient range. While maintaining a constant layer thickness, the initial and final Al composition values ​​for each sublayer were fine-tuned to verify the impact of different barrier height gradients on electron blocking efficiency and brightness.

[0046] The specific structural parameters and corresponding test results (including XRD half-width, forward voltage variation and brightness variation) of each experimental group are shown in Table 1.

[0047] Table 1: Comparison of device performance under different electron confinement layer structural parameters Conditional Experiment Thickness of the first / second / third electron confinement layer (nm) First / Second / Third Electron Confinement Layer Al Components <![CDATA[First / Second / Third electron confinement layer Si doping concentration (atoms / cm 3 )]]> XRD 002 (arcsec) XRD 102 (arcsec) Voltage Condition 1 100 / 100 / 100 0.01 rises to 0.03 / 0.05 rises to 0.08 / 0.1 rises to 0.15 <![CDATA[1×10 17 Increase to 3×10 17 / 5×10 17 Increase to 8×10 17 / 1×10 18 Increase to 3×10 18 ]]> 92 168 Up 0.1% Condition 2 50 / 65 / 65 0.01 rises to 0.03 / 0.05 rises to 0.08 / 0.1 rises to 0.15 <![CDATA[1×10 17 Increase to 3×10 17 / 5×10 17 Increase to 8×10 17 / 1×10 18 Increase to 3×10 18 ]]> 105 175 - Condition 3 130 / 130 / 130 0.01 rises to 0.03 / 0.05 rises to 0.08 / 0.1 rises to 0.15 <![CDATA[1×10 17 Increase to 3×10 17 / 5×10 17 Increase to 8×10 17 / 1×10 18 Increase to 3×10 18 ]]> 87 159 Up 0.2% Condition 4 100 / 100 / 100 0.01 rises to 0.04 / 0.05 rises to 0.09 / 0.1 rises to 0.14 <![CDATA[1×10 17 Increase to 3×10 17 / 5×10 17 Increase to 8×10 17 / 1×10 18 Increase to 3×10 18 ]]> 89 163 Up 0.3% Condition 5 100 / 100 / 100 0.02 rises to 0.03 / 0.06 rises to 0.08 / 0.12 rises to 0.15 <![CDATA[1×10 17 Increase to 3×10 17 / 5×10 17 Increase to 8×10 17 / 1×10 18 Increase to 3×10 18 ]]> 91 165 Up 0.2% Comparative Example (Conventional Structure) - - - 114 196 - Table 1 Results Analysis: 1. Significant improvement in crystal quality (XRD data analysis): By comparing the half-width at half maximum (FWHM) data of the rocking curves of the X-ray diffraction (XRD) examples (conditions 1 to 5) with those of the comparative example (conventional structure), it can be found that after introducing the dual gradient electron confinement layer of the present invention, the FWHM of both the (002) and (102) planes is significantly reduced.

[0048] Comparative results: The (002) / (102) FWHM of the comparative example is 114 / 196 arcsec, while that of condition 1 using the preferred parameters of this invention is reduced to 92 / 168 arcsec. This indicates that the stress field introduced by the gradient Al composition effectively induces the bending and merging of dislocations, significantly reduces the dislocation density penetrating to the active region, and improves the crystal quality of the epitaxial layer.

[0049] Effect of thickness: Comparing condition 2 (thinner, 50-65nm) and condition 3 (thicker, 130nm), it can be seen that the dislocation filtering effect is enhanced with the increase of electron confinement layer thickness (condition 3 has the lowest FWHM, at 87 / 159 arcsec). However, an excessively thin confinement layer (condition 2) has insufficient force modulation, resulting in a smaller improvement in crystal quality (105 / 175 arcsec).

[0050] 2. Enhanced luminous efficiency and electron blocking ability (luminance data analysis): All samples using the structure of this invention exhibited superior luminous efficacy (LOP) compared to the comparative examples.

[0051] Electron deceleration mechanism: Condition 1 showed a 3% increase in brightness compared to the comparative example, verifying that the step-increasing Al composition barrier effectively reduced the electron drift velocity, increased the electron capture probability in the quantum well, and reduced electron leakage.

[0052] Composition optimization: Compared with condition 4, when the Al composition is appropriately increased (e.g., to 0.04 on the top surface of the first layer and 0.09 on the second layer), the barrier height increases, the electron confinement capability is further enhanced, and the brightness improvement reaches a maximum of 3.5%. However, if the Al composition is too high or too low (e.g., in condition 2, the barrier effect time is short due to the thin layer), the brightness improvement will be limited (+1.8%).

[0053] 3. Effective control of operating voltage (voltage data analysis): Introducing a high Al composition layer typically increases the series resistance of the device, thereby increasing the forward operating voltage (Vf). However, the data in Table 1 shows that the voltage rise in the embodiments of this invention is extremely small (only 0.1%~0.3%), essentially remaining at a level comparable to the comparative example.

[0054] Si gradient compensation effect: This fully demonstrates the success of the strategy designed in this invention, which involves "Si doping concentration increasing synchronously with Al composition." High concentrations of Si doping (up to 3 × 10¹) 8 The (atoms / cm³) effectively compensates for the increased resistivity caused by the high Al composition and suppresses the DX center effect, ensuring that electrical performance is not sacrificed while improving brightness.

[0055] Overall balance: Although condition 3 has the best crystal quality, the voltage rises slightly to 0.2% due to the increased total thickness; in condition 4, the voltage rises to 0.3% due to the higher Al content. Considering the balance of crystal quality, brightness, and voltage, condition 1 (100 nm thickness, moderate Al content and doping) exhibits the best overall performance.

[0056] In summary, the dual-gradient electron confinement layer of the present invention, through the synergistic design of structural parameters, simultaneously improves crystal quality and enhances luminous efficiency without increasing the operating voltage.

[0057] This invention successfully solves two major challenges in GaN-based LEDs: electron leakage and crystal quality, by introducing a three-layer electron confinement layer with a "dual gradient" of Al composition and Si doping concentration on the n-side. This method offers good process compatibility, requires no complex equipment modifications, and has extremely high industrial application value.

Claims

1. A light-emitting diode epitaxial wafer with a dual-gradient electron confinement layer, characterized in that, include: The substrate, buffer layer, undoped GaN layer, n-type GaN layer, electron confinement layer, active layer, electron blocking layer and p-type GaN layer are stacked sequentially along the growth direction. The electron confinement layer is located between the n-type GaN layer and the active layer, and is composed of a first electron confinement layer, a second electron confinement layer and a third electron confinement layer stacked sequentially. The first electron confinement layer, the second electron confinement layer, and the third electron confinement layer are all Si-doped n-type AlGaN layers; The electron confinement layer is characterized by having a dual gradient structure of Al composition and Si doping concentration. Regarding Al composition: the average Al composition of the first electron confinement layer, the second electron confinement layer, and the third electron confinement layer increases sequentially; and within each electron confinement layer, the Al composition exhibits a continuous gradient distribution along the direction away from the substrate. Regarding the Si doping concentration: the average Si doping concentration of the first electron confinement layer, the second electron confinement layer and the third electron confinement layer increases sequentially; and within each electron confinement layer, the Si doping concentration is distributed in a continuous gradient increasing direction away from the substrate.

2. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The Al composition distributions of the first, second, and third electron confinement layers satisfy the following conditions: The first electron confinement layer is wherein the Al composition increases linearly from 0.01~0.02 to 0.03~0.05 from the bottom surface to the top surface of the first electron confinement layer; The second electron confinement layer is wherein the Al composition increases linearly from 0.05~0.06 to 0.08~0.10 from the bottom surface to the top surface of the second electron confinement layer; The third electron confinement layer is wherein the Al composition increases linearly from 0.10~0.12 to 0.14~0.15 from the bottom surface to the top surface of the third electron confinement layer; In this design, the Al composition of the top surface of the first electron confinement layer is smaller than that of the bottom surface of the second electron confinement layer, and the Al composition of the top surface of the second electron confinement layer is smaller than that of the bottom surface of the third electron confinement layer, thereby forming an Al composition step at the interface of adjacent electron confinement layers.

3. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The Si doping concentration distributions of the first, second, and third electron confinement layers satisfy the following condition: The Si doping concentration of the first electron confinement layer is from 1×10 17 atoms / cm 3 Rising continuously to 5×10 17 atoms / cm 3 ; The Si doping concentration of the second electron confinement layer is from 5 × 10⁻⁶. 17 atoms / cm 3 Rising continuously to 1×10 18 atoms / cm 3 ; The Si doping concentration of the third electron confinement layer is from 1×10⁻⁶. 18 atoms / cm 3 Rising continuously to 5×10 18 atoms / cm 3 .

4. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The thicknesses of the first electron confinement layer, the second electron confinement layer, and the third electron confinement layer are all between 10 nm and 200 nm.

5. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The active layer comprises alternating layers of InGaN quantum wells and GaN quantum barriers; The top surface of the third electron confinement layer is in direct contact with the first quantum barrier layer of the active layer; or, an undoped GaN stress relief layer is sandwiched between the third electron confinement layer and the active layer.

6. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The substrate is a patterned substrate, and a three-dimensional nucleation layer is also included between the substrate and the undoped GaN layer.

7. A method for fabricating a light-emitting diode epitaxial wafer as described in any one of claims 1 to 6, characterized in that, Includes the following steps: A substrate is provided on which a buffer layer, an undoped GaN layer, and an n-type GaN layer are sequentially grown. The electron confinement layer is grown on the n-type GaN layer; An active layer, an electron blocking layer, and a p-type GaN layer are grown on the electron confinement layer; The step of growing the electron confinement layer includes: maintaining a reaction chamber pressure of 50 Torr to 300 Torr, and linearly increasing the flow rate of trimethylaluminum (TMAl) while keeping the gallium source flow rate constant to form a continuous gradient increase of Al composition. Furthermore, during the growth of the electron confinement layer, the flow rate of silane (SiH4) gas is continuously increased according to a preset linear slope to form a continuous gradient increase in Si doping concentration.

8. The preparation method according to claim 7, characterized in that, The atmosphere during the growth of the electron confinement layer includes N2, H2 and NH3, wherein the volumetric flow rate ratio of N2:H2:NH3 is from 1:1:1 to 1:5:10.

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