Deep ultraviolet light emitting diode

Abstract

The invention discloses a deep ultraviolet light emitting diode, and relates to the technical field of semiconductor illumination. The deep ultraviolet light emitting diode comprises an epitaxial structure and a composite function layer, the epitaxial structure further comprises a first step channel and a second step channel which are of a step structure, and the first step channel is arranged to be sunken downwards from the top face of a p-type injection layer to the top face of an n-type injection layer. The second step channel is arranged on one side, far away from the first step channel, of the n-type electrode layer and is recessed downwards from the top surface of the n-type injection layer to the AlN intrinsic layer, the top surface of the p-type injection layer, the surface of the p-type electrode layer, the first step channel and the second step channel. Each composite functional layer comprises at least two adjacent insulating layers with different refractive indexes, and the distance between the bottom surface of the second step channel and the top surface of the substrate layer is any one of 0-10 [mu] m. The deep ultraviolet light-emitting diode provided by the invention has relatively high light output power and device reliability at the same time.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor lighting, and particularly relates to a deep ultraviolet light emitting diode. BACKGROUND

[0002] At present, deep ultraviolet LEDs (Light Emitting Diode) are often used in various household appliances in the form of modules, such as refrigerators, air conditioners, washing machines and the like.

[0003] However, the use environment of household appliances is relatively closed, which causes the actual working temperature of the deep ultraviolet LED to be usually higher than 60 DEG C, and working in a high-temperature environment will cause the reliability of the deep ultraviolet LED chip to be more deteriorated. In addition, due to the physical properties of the light-emitting layer, most of the emitted light in the deep ultraviolet LED is side light, which will cause the light-emitting efficiency of the deep ultraviolet LED to be low, and further affect the light output power of the deep ultraviolet LED.

[0004] Therefore, it is of great significance to design a deep ultraviolet LED which can have both high light output power and high device reliability. SUMMARY

[0005] An object of the application is to provide a deep ultraviolet light emitting diode, which solves the technical problem of low light-emitting efficiency and reliability of the deep ultraviolet light emitting diode in the prior art.

[0006] Another object of the application is to further improve the light output power of the deep ultraviolet light emitting diode.

[0007] According to the object of the application, the application provides a deep ultraviolet light emitting diode, which comprises an epitaxial structure and a composite functional layer, the epitaxial structure comprises a substrate layer, an AlN intrinsic layer, an n-type injection layer, a light-emitting layer and a p-type injection layer which are sequentially arranged from bottom to top, a p-type electrode layer is arranged on the p-type injection layer, and an n-type electrode layer is arranged on the top surface of the n-type injection layer. The epitaxial structure further comprises a first stepped channel and a second stepped channel in a stepped structure, the first stepped channel is arranged to be recessed from the top surface of the p-type injection layer to the top surface of the n-type injection layer, the second stepped channel is arranged on the side of the n-type electrode layer away from the first stepped channel and is recessed from the top surface of the n-type injection layer to the AlN intrinsic layer, and at least one layer of the composite functional layer is arranged in the top surface of the p-type injection layer, the surface of the p-type electrode layer, the first stepped channel and the second stepped channel respectively, each layer of the composite functional layer comprises at least two layers of insulating layers with different refractive indexes between two adjacent layers, and the distance between the bottom surface of the second stepped channel and the top surface of the substrate layer is any value in the range of 0-10 microns.

[0008] Optionally, the p-type electrode layer comprises: a p-type contact electrode above the p-type injection layer; at least one thickened electrode on the surface of the p-type contact electrode, and the p-type contact electrode is provided with the composite functional layer between the p-type contact electrode and the thickened electrode and / or between two adjacent thickened electrodes.

[0009] Optionally, the minimum width of two adjacent second step channels is greater than or equal to 0.2 μm.

[0010] Optionally, the material of the insulating layer is any one of SiO2, Al2O3, TiO2 and Ta2O5.

[0011] Optionally, the insulating layers with different refractive indexes are prepared by the same material through different preparation processes or are composed of different materials.

[0012] Optionally, the preparation process of the insulating layer comprises a plasma enhanced chemical vapor deposition process or an atomic layer deposition process.

[0013] Optionally, the number of layers of the composite functional layer is any one of 2-200.

[0014] Optionally, the bottom surface of the first step channel or the second step channel is any one of a plane, an angle and a circular arc.

[0015] Optionally, the Al component in the n-type injection layer is any one of 20%-90%, and the thickness is any one of 500 nm-4000 nm.

[0016] Optionally, the thickness of the AlN intrinsic layer is any one of 500 nm-4000 nm.

[0017] The first step channel of the present application can refract the lateral light above the p region to the outside, reduce the total reflection in the p-type injection layer, and the second step channel further extends to the AlN intrinsic layer, so that the light of the n-type AlGaN layer to the waveguide region of the AlN intrinsic layer can be directly coupled and extracted, and the refractive index difference of the composite functional layer produces a multi-layer reflection and interference effect on the inner wall, and more deep ultraviolet light is reflected to the light emitting direction, that is, the composite functional layer cooperates with the first step channel and the second step channel to optimize the light emitting path of the deep ultraviolet light emitting diode, thereby significantly improving the light emitting efficiency. Moreover, the double-channel design in the present embodiment effectively reduces the heat accumulation area in the chip body, the composite functional layer improves the interface density and disperses stress, thereby preventing impurities or water vapor from penetrating, improving the structural reliability of the deep ultraviolet light emitting diode under high temperature, and avoiding film cracking in a high temperature environment.

[0018] Further, the present application introduces a multi-layer composite structure composed of a p-type contact electrode, a thickened electrode and a composite functional layer in the p-type electrode layer, the multi-layer composite functional layer synergistically works, not only effectively reduces the contact resistance and thermal resistance of the p-type electrode layer, improves the carrier injection and conduction efficiency, but also enhances the light reflection and emission efficiency, thereby significantly improves the light output power of the deep ultraviolet light emitting diode.

[0019] The above description is only a summary of the technical solutions of the present application. In order to make the technical means of the present application more clearly understood, and to be implemented according to the content of the description, the following will be described in detail with the preferred embodiments of the present application and in conjunction with the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] Some specific embodiments of the present application will be described in detail hereinafter with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference signs in the drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 is a schematic structural diagram of a deep ultraviolet light emitting diode according to an embodiment of the present application; Figure 2 is a schematic top view of a deep ultraviolet light emitting diode according to an embodiment of the present application; Figure 3 is a schematic structural diagram of a composite functional layer according to an embodiment of the present application; Figure 4 is a schematic structural diagram of the position of a composite functional layer according to an embodiment of the present application; Figure 5 is a schematic structural diagram of the position of a composite functional layer according to another embodiment of the present application; Figure 6 is a schematic structural diagram of a deep ultraviolet light emitting diode according to another embodiment of the present application; Figure 7 is a schematic structural diagram of a deep ultraviolet light emitting diode according to still another embodiment of the present application; Figure 8 is a schematic flow chart of a preparation method of a deep ultraviolet light emitting diode according to the present application; Figure 9 is a scanning electron microscope image of a deep ultraviolet light emitting diode according to embodiment 1 of the present application.

[0021] Reference signs: 100 - deep ultraviolet light emitting diode, 10 - epitaxial structure, 20 - composite functional layer, 21 - first insulating layer, 22 - second insulating layer, 11 - substrate layer, 12 - AlN intrinsic layer, 13 - n-type injection layer, 14 - light emitting layer, 15 - p-type injection layer, 16 - first stepped channel, 17 - second stepped channel, 18 - current spreading region, 19 - electron blocking layer, 30 - p-type electrode layer, 40 - n-type electrode layer, 31 - p-type contact electrode, 32 - first thickened electrode, 33 - second thickened electrode, 50 - passivation layer. DETAILED DESCRIPTION

[0022] The specific embodiments of the present application will be further described in details with reference to the drawings and examples. The following examples are used to illustrate the present application but not to limit the scope of the present application.

[0023] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in details with reference to the drawings. It can be understood that the specific embodiments described herein are only used to explain the present application but not to limit the present application. In addition, it should be noted that only the parts related to the present application are shown in the drawings for the convenience of description but not all the structures. All the other embodiments obtained by those skilled in the art without making creative efforts based on the embodiments in the present application are within the scope of protection of the present application.

[0024] The terms "comprising" and "having" and any variations thereof in the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units but can optionally include steps or units not listed or can optionally include other steps or units inherent to these processes, methods, products or devices.

[0025] In this document, reference to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. Those skilled in the art will appreciate that embodiments described herein can be combined with other embodiments.

[0026] Figure 1 is a schematic structural diagram of a deep ultraviolet light emitting diode according to an embodiment of the present application, Figure 2 is a schematic top view of a deep ultraviolet light emitting diode according to an embodiment of the present application, Figure 3 is a schematic structural diagram of a composite functional layer according to an embodiment of the present application, Figure 4This is a schematic structural diagram showing the location of the composite functional layer according to an embodiment of the present invention. Figure 5 This is a schematic structural diagram showing the location of the composite functional layer according to another embodiment of the present invention. Figure 6 This is a schematic structural diagram of a deep ultraviolet light-emitting diode according to another embodiment of the present invention. Figure 7 This is a schematic structural diagram of a deep ultraviolet light-emitting diode according to yet another embodiment of the present invention. Figure 8 This is a schematic flowchart of the fabrication method of the deep ultraviolet light-emitting diode according to the present invention. Figure 9 This is a scanning electron microscope image of a deep ultraviolet light-emitting diode according to Embodiment 1 of the present invention.

[0027] like Figure 1 As shown, the present invention provides a deep ultraviolet light-emitting diode 100, which includes an epitaxial structure 10 and a composite functional layer 20. The epitaxial structure 10 includes a substrate layer 11, an AlN intrinsic layer 12, an n-type injection layer 13, a light-emitting layer 14, and a p-type injection layer 15, which are stacked sequentially from bottom to top. A p-type electrode layer 30 is provided on the p-type injection layer 15, and an n-type electrode layer 40 is provided on the top surface of the n-type injection layer 13. Here, the substrate layer 11 is a sapphire substrate, the n-type injection layer 13 is an n-type AlGaN layer, and the light-emitting layer 14 is an AlGaN multiple quantum well structure.

[0028] like Figure 1 As shown, in this embodiment, the epitaxial structure 10 further includes a first stepped channel 16 and a second stepped channel 17 with a stepped structure. The first stepped channel 16 is configured to be recessed downward from the top surface of the p-type injection layer 15 to the top surface of the n-type injection layer 13. The second stepped channel 17 is disposed on the side of the n-type electrode layer 40 away from the first stepped channel 16 and is recessed downward from the top surface of the n-type injection layer 13 to the AlN intrinsic layer 12. At least one composite functional layer 20 is respectively provided in the top surface of the p-type injection layer 15, the surface of the p-type electrode layer 30, the first stepped channel 16, and the second stepped channel 17 (see reference). Figure 2 Each composite functional layer 20 includes at least two insulating layers with different refractive indices on adjacent layers, and the distance between the bottom surface of the second stepped channel 17 and the top surface of the substrate layer 11 is any value between 0 μm and 10 μm. Here, the inner wall of the first stepped channel 16 is also provided with a composite functional layer 20. When the distance between the bottom surface of the second stepped channel 17 and the top surface of the substrate layer 11 is 0 μm, the second stepped channel 17 is in direct contact with the substrate layer 11. The distance between the bottom surface of the second stepped channel 17 and the top surface of the substrate layer 11 can also be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, or any other value between 0 μm and 10 μm. A passivation layer 50 is provided on the p-type electrode layer 30.

[0029] In this embodiment, by providing a first stepped channel 16 and a second stepped channel 17 in a stepped structure in the epitaxial structure 10, and by providing a composite functional layer 20 in the top surface of the p-type injection layer 15, the surface of the p-type electrode layer 30, the first stepped channel 16, and the second stepped channel 17, and by providing a composite functional layer 20 with different refractive indices for adjacent layers of the multilayer insulating layers in the composite functional layer 20, the first stepped channel 16 allows lateral light above the p-region to be refracted to the outside, reducing total internal reflection in the p-type injection layer 15. The second stepped channel 17 further extends to the AlN intrinsic layer 12, allowing light from the waveguide region from the n-type AlGaN layer to the AlN intrinsic layer 12 to be directly coupled and extracted. The refractive index difference of the composite functional layer 20 generates multilayer reflection and interference effects on the inner wall, reflecting more deep ultraviolet light to the light emission direction. In other words, the composite functional layer 20, together with the first stepped channel 16 and the second stepped channel 17, optimizes the light emission path of the deep ultraviolet light-emitting diode 100, thereby significantly improving the light emission efficiency. Furthermore, the dual-channel design in this embodiment effectively reduces the heat accumulation area within the chip, and the composite functional layer 20 improves interface density and disperses stress, thereby preventing impurities or moisture from penetrating and enhancing the structural reliability of the deep ultraviolet light-emitting diode 100 at high temperatures, thus avoiding thin film cracking in high-temperature environments. Here, the number of composite functional layers 20 between the p-type injection layer 15 and the p-type electrode layer 30 can be 1, 2, or more, and the number of composite functional layers 20 in the inner wall of the second stepped channel 17 and on the electrode mesa can be 1, 2, or more.

[0030] In this embodiment, the distance between the bottom surface of the second stepped channel 17 and the top surface of the substrate layer 11 is set to 0μm-10μm. When the distance is 0μm, the second stepped channel 17 is in direct contact with the substrate layer 11, allowing the channel to extend sufficiently to the bottom region of the epitaxial structure 10. This allows it to work synergistically with the composite functional layer 20 disposed on the inner wall of the channel to form a strong refractive index difference interface, enabling multiple reflections and effective light extraction. This significantly reduces the total internal reflection loss in the waveguide region. Simultaneously, the direct contact between the channel and the substrate shortens the heat conduction path, allowing heat to dissipate more quickly through the sapphire substrate, thus improving the chip's thermal stability under high-temperature conditions. When the distance is between 0.5μm and 10μm, a specific optical path difference region is formed between the second stepped channel 17 and the AlN intrinsic layer 12. Under the multilayer refractive modulation effect of the composite functional layer 20, multiple interference and coupling effects are generated, further improving the deep ultraviolet light emission efficiency.

[0031] In this embodiment, the sidewall of the second stepped channel 17 is an inclined structure. The inclined sidewall can increase the light-emitting area and change the light emission direction, reduce the total internal reflection effect, enhance the light extraction efficiency, and improve the etching interface quality and current distribution characteristics.

[0032] like Figure 3As shown, in this embodiment, each composite functional layer 20 includes multiple layers of spaced first insulating layer 21 and second insulating layer 22. The material of the first insulating layer 21 is the same as that of the second insulating layer 22. The refractive index of the first insulating layer 21 is lower than that of the second insulating layer 22, which helps to improve the light propagation path. In particular, it forms light reflection and refraction within the composite functional layer 20. The low refractive index of the first insulating layer 21 can effectively limit the propagation of light, while the high refractive index of the second insulating layer 22 can effectively enhance the reflection of light, so that more light is guided to the output direction of the device and the light loss is reduced.

[0033] like Figure 1 As shown, in this embodiment, the epitaxial structure 10 further includes a current spreading layer 18 and an electron blocking layer 19. The current spreading layer 18 is disposed between the n-type injection layer 13 and the light-emitting layer 14, and the electron blocking layer 19 is disposed between the light-emitting layer 14 and the p-type injection layer 15. The introduction of the current spreading layer 18 makes the distribution of electrons in the light-emitting layer 14 more uniform, reducing the current concentration effect, thereby improving the uniformity of light emission and the reliability of the device. Simultaneously, it reduces the series resistance, significantly improving the optical power output of the deep ultraviolet light-emitting diode 100. The electron blocking layer 19 effectively prevents high-energy electrons from overflowing from the light-emitting layer 14 into the p-region, improving the recombination efficiency of electrons and holes in the light-emitting layer 14, thereby improving the internal quantum efficiency and optical output power of the deep ultraviolet light-emitting diode 100. By combining the current spreading layer 18 and the electron blocking layer 19 with the double-stepped channel structure and the composite functional layer 20, multi-dimensional optimization of carrier distribution, current conduction, light extraction path, and thermal stability is achieved, thereby significantly improving the optical output power and reliability of the deep ultraviolet light-emitting diode 100 in high-temperature environments.

[0034] like Figure 4 and Figure 5As shown, in a further embodiment, the p-type electrode layer 30 includes a p-type contact electrode 31 and at least one thickened electrode. The p-type contact electrode 31 is located above the composite functional layer 20, and the thickened electrode is located above the p-type contact electrode 31. The composite functional layer 20 is provided between the p-type contact electrode 31, the thickened electrode, and two adjacent thickened electrodes. In this embodiment, by introducing a multi-layer composite structure consisting of the p-type contact electrode 31, the thickened electrode, and the composite functional layer 20 into the p-type electrode layer 30, the p-type contact electrode 31 achieves low-ohmic contact and uniform current injection, the thickened electrode improves conductivity and heat dissipation performance, and the composite functional layer 20 achieves light reflection and insulation isolation through refractive index differences. The multi-layer composite functional layer 20 works synergistically, effectively reducing the contact resistance and thermal resistance of the p-type electrode layer 30, improving carrier injection and conduction efficiency, and enhancing light reflection and emission efficiency, thereby significantly improving the light output power of the deep ultraviolet light-emitting diode 100. Here, the number of thickened electrode layers can be 1, 2, or 3, or other layers greater than 3. When the number of thickened electrode layers is 1, the top surface of the p-type contact electrode is provided with a first thickened electrode 32 (refer to...). Figure 6 ).

[0035] like Figure 7 As shown, in this embodiment, when the number of thickened electrode layers is two, the p-type electrode layer 30 includes a p-type contact electrode 31, a first thickened electrode 32, and a second thickened electrode 33 distributed sequentially from bottom to top. At least one composite functional layer 20 is provided between the p-type contact electrode 31 and the first thickened electrode 32 and / or between the first thickened electrode 32 and the second thickened electrode 33, so that the interface optical and electrical properties between each electrode layer are controlled in layers. That is, the refractive indices of adjacent insulating layers in the composite functional layer 20 are different, which can form a multi-level optical reflection adjustment interface between the multi-layer metal electrodes, thereby effectively suppressing the light absorption loss of the metal layer and improving the light extraction efficiency of deep ultraviolet light. At the same time, the composite functional layer 20 plays a role in stress buffering and interface smoothing during the upper metal deposition process, avoiding failure problems such as warping and cracking of the thickened electrode when the current density is concentrated during high-temperature annealing or current concentration. The design of the double-layer thickened electrode makes the current distribution more uniform and reduces the current crowding effect, thereby achieving uniform thermal field distribution and improved device stability.

[0036] In a further embodiment, the minimum width of two adjacent second-step channels 17 is greater than or equal to 0.2 μm, ensuring a reasonable spacing distribution between the channels. Appropriate channel spacing effectively avoids problems such as channel morphology collapse and difficulty in removing residual adhesive caused by sidewalls being too close during photolithography and etching, ensuring the integrity of the channel outline and the uniform deposition of the composite functional layer 20. Simultaneously, a spacing of 0.2 μm or more helps improve the uniformity of current spread within the n-type injection layer 13 region, preventing heat accumulation and uneven light emission caused by localized current concentration, and enabling the formation of favorable light scattering channels in the channel array, reducing light absorption loss below the metal electrodes, thereby improving light extraction efficiency.

[0037] In a further embodiment, the insulating layer is made of any one of SiO2, Al2O3, TiO2, and Ta2O5. Different insulating layer materials allow for flexible control of the optical and electrical properties of the composite functional layer 20 within different dielectric constant and refractive index ranges. Specifically, SiO2 has a low refractive index and excellent light transmittance, making it suitable for forming a low-refractive layer and reducing light reflection loss at the interface. Al2O3 combines a moderate refractive index with excellent thermal stability, maintaining the integrity of the interlayer structure under high-temperature operating conditions. TiO2 and Ta2O5 have high refractive indices, enhancing the light reflection effect at the interface. This allows for the control of refractive index differences between the multilayer media, forming an optical interference enhancement structure and improving light extraction efficiency. Here, the refractive index of SiO2 is approximately 1.46, the refractive index of Al2O3 is approximately 1.7, and the refractive indices of TiO2 and Ta2O5 are 2.3-2.5.

[0038] In this embodiment, SiO2, Al2O3, TiO2, and Ta2O5 all possess excellent insulation and chemical stability, effectively preventing leakage current and ion migration between electrodes and improving the long-term reliability of the device. That is, through the selective combination of the refractive indices and dielectric properties of different insulating materials, the deep ultraviolet light-emitting diode 100 achieves a synergistic balance between light extraction efficiency, thermal stability, and insulation protection performance.

[0039] In a further embodiment, insulating layers with different refractive indices are obtained by using the same material but different fabrication processes or are composed of different materials. In this embodiment, by using the same material but different fabrication processes to form insulating layers with different refractive indices, precise control of the optical performance of the composite functional layer 20 can be achieved while ensuring material system compatibility and interface stability. This not only avoids the interfacial stress and thermal expansion mismatch problems caused by alternating deposition of multiple materials, improving interlayer bonding strength and thermal stability, but also effectively reduces interfacial scattering loss and defect recombination probability, and improves the emission directionality of light and the overall optical output power of the device.

[0040] In a further embodiment, the fabrication process of the insulating layer includes plasma-enhanced chemical vapor deposition or atomic layer deposition, which can significantly improve the film uniformity and interface quality of the composite functional layer 20, thereby significantly improving the structural controllability, compactness and optical uniformity of the insulating layer, and further enhancing the ability of the composite functional layer 20 to adjust the light reflection and refraction paths, and improving the light extraction efficiency and long-term reliability of the deep ultraviolet light-emitting diode 100.

[0041] In a further embodiment, the number of composite functional layers 20 is any value from 2 to 200, that is, the number of composite functional layers 20 can be 2, 3, 5, 10, 20, 30, 50, 70, 80, 90, 100, 150, or 200, or any other value from 2 to 200. In this embodiment, when the number of composite functional layers 20 is 2-10, lower fabrication complexity and stress accumulation can be achieved, which helps maintain the integrity of the device structure and interface stability. When the number of layers is 50-200, a Bragg reflection structure with high reflectivity and multiple light interference can be formed. The periodic changes between layers with different refractive indices significantly enhance the light reflection and extraction efficiency, effectively reduce internal total internal reflection loss, and improve the light extraction rate and optical power. At the same time, the multilayer composite functional layers 20 can also play a role in stress buffering and heat diffusion, reducing the risk of interface cracks and film peeling under high temperature environments, thereby improving the thermal stability and lifespan of the deep ultraviolet light-emitting diode 100. Therefore, the setting of this layer range takes into account both process feasibility and optical performance optimization, so that the composite functional layer 20 can form a synergistic effect between light reflection enhancement, thermal stress adjustment and structural reliability.

[0042] In a further embodiment, the bottom surface of the first stepped channel 16 or the second stepped channel 17 can be any one of a planar, angular, or arc-shaped surface. In this embodiment, by introducing a multi-morphological selectable structure of planar, angular, or arc-shaped bottom morphology in the channel bottom design, a synergistic effect is formed with the refractive index regulation of the composite functional layer 20 and the stepped deep channel design, which not only improves the light extraction efficiency and light emission uniformity, but also takes into account the thermal management performance and process adaptability of the device.

[0043] In this embodiment, when the bottom surface of the channel is planar, it provides a regular reflective interface, allowing incident light to be reflected along a fixed angle, which helps improve the consistency of the output light direction and the uniformity of the device beam. When the bottom surface of the channel is angular, the multi-angle refractive interface at the bottom can change the light propagation path, allowing some laterally propagating light to be reflected and extracted again, further reducing the total internal reflection loss on the sidewalls and improving the light extraction efficiency in the waveguide region. When the bottom surface of the channel is arc-shaped, the light undergoes multi-angle diffuse reflection and refraction superposition at the arc surface, which can achieve uniform light scattering, avoid heat accumulation caused by local light intensity concentration, and improve the current distribution at the bottom of the channel, reducing local stress concentration.

[0044] In a further embodiment, the Al composition in the n-type injection layer 13 is any value between 20% and 90%, that is, the Al composition can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%, or any other value between 20% and 90%. The thickness is any value between 500nm and 4000nm, that is, 500nm, 1000nm, 1500nm, 2000nm, 2500nm, 3000nm, 3500nm, or 4000nm, or any other value between 500nm and 4000nm. In this embodiment, the setting of the Al composition and thickness range not only ensures the bandgap matching of the material and the effective injection of charge carriers, but also works together with the refractive index distribution of the stepped channel and the composite functional layer 20 to achieve a synergistic technical effect of high light extraction efficiency, low thermal resistance, and excellent optical output stability.

[0045] In this embodiment, with the increase of Al content, the bandgap of the n-type AlGaN layer increases, which can effectively suppress nonradiative recombination of charge carriers outside the emitting layer 14 and reduce interface recombination loss. At the same time, the higher Al content improves the transmittance of the material in the deep ultraviolet band, which helps the light to be efficiently extracted from the waveguide region. Combined with the structural design of the second-step channel 17, it can further reduce sidewall total internal reflection and improve light extraction efficiency. On the other hand, by appropriately controlling the thickness of the n-type injection layer 13 in the range of 500nm-4000nm, a balance can be achieved between charge carrier transport and optical mode control: a thinner structure can reduce device resistance and growth stress, while a thicker structure can enhance the light confinement and reflection path modulation, so that the deep ultraviolet light emitted by the emitting layer 14 can form multiple reflections and interferences between the composite functional layer 20 and the AlN intrinsic layer 12.

[0046] In a further embodiment, the thickness of the AlN intrinsic layer 12 is any value between 500nm and 4000nm, that is, the thickness of the AlN intrinsic layer 12 can be 500nm, 1000nm, 1500nm, 2000nm, 2500nm, 3000nm, 3500nm, or 4000nm, or any other value between 500nm and 4000nm. In this embodiment, by adjusting the thickness of the AlN intrinsic layer 12 within this thickness range, the carrier transport path and interface barrier height in the epitaxial structure 10 can be optimized while suppressing stress accumulation and lattice mismatch defects. It also works synergistically with the n-type injection layer 13, stepped channels, and other structures to achieve a balance between stress control, electrical isolation, and carrier modulation, thereby optimizing device performance and structural stability.

[0047] In this embodiment, when the thickness is between 500nm and 1500nm, it helps to reduce the overall stress and interface defect density, and improve the lattice matching with the underlying substrate or buffer layer. When the thickness is between 2500nm and 4000nm, it can enhance electrical isolation and breakdown voltage performance, reduce interface recombination effects, and improve the reliability and output stability of the device.

[0048] like Figure 8 As shown, in this embodiment, the fabrication method of the deep ultraviolet light-emitting diode 100 includes the following steps: Step S100: Using MOCVD (Metal-Organic Chemical Vapor Deposition) process, an epitaxial structure 10 is epitaxially grown. The epitaxial structure 10 includes a substrate layer 11, an AlN intrinsic layer 12, an n-type implantation layer 13, a light-emitting layer 14 and a p-type implantation layer 15 arranged sequentially from bottom to top. Step S200: Clean the surface of the epitaxial structure 10, and use photolithography and etching processes to etch and prepare the first stepped channel 16 in the light-emitting layer 14 and the p-type injection layer 15; Step S300: The second stepped channel 17 is fabricated by etching the AlN intrinsic layer 12 and the n-type implantation layer 13 using photolithography and etching processes; Step S400: The n-type electrode layer 40 and the p-type electrode layer 30 are sequentially prepared using photolithography, deposition and etching processes; Step S500: Sequentially deposit a composite functional layer 20 and a passivation layer 50 between the p-type implantation layer 15 and the p-type electrode layer 30, on the inner walls of the first stepped channel 16 and the second stepped channel 17, and on the electrode mesa (refer to...). Figure 9 ), and a deep ultraviolet light-emitting diode 100 was prepared.

[0049] In this embodiment, the fabrication method of the deep ultraviolet light-emitting diode 100 firstly uses MOCVD process to epitaxially grow an epitaxial structure 10. The epitaxial structure 10 includes a substrate layer 11, an AlN intrinsic layer 12, an n-type implantation layer 13, a light-emitting layer 14, and a p-type implantation layer 15 arranged sequentially from bottom to top. Then, the surface of the epitaxial structure 10 is cleaned, and a first stepped channel 16 is etched in the light-emitting layer 14 and the p-type implantation layer 15 using photolithography and etching processes. A second stepped channel 17 is fabricated by etching the AlN intrinsic layer 12 and the n-type implantation layer 13 using photolithography and etching processes. An n-type electrode layer 40 and a p-type electrode layer 30 are then sequentially fabricated using photolithography, deposition, and etching processes. Finally, a composite functional layer 20 and a passivation layer are sequentially deposited between the p-type implantation layer 15 and the p-type electrode layer 30, on the inner walls of the first stepped channel 16 and the second stepped channel 17, and on the electrode mesa surface to fabricate a deep ultraviolet light-emitting diode 100. Here, the n-type implantation layer 13 is an n-type AlGaN layer, and the p-type implantation layer 15 is a p-type AlGaN layer.

[0050] In this embodiment, the deep ultraviolet light-emitting diode 100 further includes an AlN low-temperature buffer layer located between the substrate layer 11 and the AlN intrinsic layer 12. The growth temperature of the AlN low-temperature buffer layer is any value between 400℃ and 800℃, and the thickness is any value between 10nm and 50nm. That is, the growth temperature can be 400℃, 500℃, 600℃, 700℃ or 800℃, or any other value between 400℃ and 800℃, and the thickness can be 10nm, 20nm, 30nm, 40nm or 50nm, or any other value between 10nm and 50nm. By growing the AlN low-temperature buffer layer at a lower temperature, the stress accumulation and lattice distortion caused by thermal mismatch in the initial epitaxial stage can be effectively reduced, so that the AlN intrinsic layer 12 has higher crystal quality and lower dislocation density when grown on it. At the same time, an appropriate buffer layer thickness can provide good lattice transition and interface flatness, and avoid the increase in thermal resistance and interface carrier scattering caused by excessive thickness. The buffer layer works synergistically with the subsequent AlN intrinsic layer 12 and n-type injection layer 13 to significantly improve the stress distribution and interface quality of the epitaxial structure 10, thereby enhancing the internal quantum efficiency, light output power and device stability of the deep ultraviolet light-emitting diode 100.

[0051] In this embodiment, the growth temperature of the AlN intrinsic layer 12 is any value within the range of 1200℃-1400℃, that is, the growth temperature can be 1200℃, 1250℃, 1300℃, 1350℃, or 1400℃, or any other value within the range of 1200℃-1400℃. By controlling the growth temperature of the AlN intrinsic layer 12 within the range of 1200℃-1400℃, the crystal quality and interface integrity of the epitaxial crystal can be significantly improved. A higher growth temperature helps to enhance the surface migration ability of Al and N atoms, promote the orderly arrangement of grains and the densification of the epitaxial layer, thereby reducing dislocation density and interface roughness. At the same time, this temperature range forms a reasonable thermal gradient match with the growth temperature of the underlying AlN low-temperature buffer layer, which can effectively alleviate the risk of cracking caused by stress concentration and thermal mismatch. Through this temperature control strategy, the AlN intrinsic layer 12 maintains high crystal quality while ensuring lattice continuity and interfacial bonding strength with the n-type injection layer 13, thereby synergistically improving the carrier injection efficiency and light output performance of the deep ultraviolet light-emitting diode 100.

[0052] In this embodiment, the growth temperature of the n-type AlGaN layer is any value between 800℃ and 1200℃, that is, the growth temperature can be 800℃, 900℃, 1000℃, 1100℃, or 1200℃, or any other value between 800℃ and 1200℃. By flexibly controlling the growth temperature of the n-type AlGaN layer within the range of 800℃ to 1200℃, the n-type AlGaN layer can possess both high crystal integrity and excellent conductivity, and form good thermal compatibility with the high-temperature growth process of the upper AlN intrinsic layer 12, avoiding stress accumulation and interface cracking, and achieving synergistic optimization of low defects, high carrier injection, and excellent electro-optical conversion efficiency of the device.

[0053] In this embodiment, the growth temperature of the light-emitting layer 14 is any value between 700℃ and 1100℃, that is, the growth temperature can be 700℃, 800℃, 900℃, 1000℃, or 1100℃, or any other value between 700℃ and 1100℃. By flexibly adjusting the growth temperature within the range of 700℃ to 1100℃, the compositional uniformity and interface quality of the quantum well can be taken into account simultaneously. Furthermore, it forms a synergistic effect of stress matching and carrier confinement with the upper and lower electrode layers, barrier layer, and buffer layer, thereby significantly improving the external quantum efficiency and luminous stability of the deep ultraviolet light-emitting diode 100.

[0054] In this embodiment, an electron blocking layer 19 is further provided between the light-emitting layer 14 and the p-type injection layer 15. The growth temperature of the electron blocking layer 19 is any value between 700℃ and 1100℃, that is, the growth temperature can be 700℃, 800℃, 900℃, 1000℃ or 1100℃, or any value between 700℃ and 1100℃. By flexibly controlling the growth temperature within the range of 700℃-1100℃, an excellent band alignment relationship can be formed between the electron blocking layer 19, the light-emitting layer 14, and the p-type injection layer 15, thereby effectively suppressing electron overflow from the light-emitting layer 14, improving hole injection efficiency, and forming a synergistic effect with the carrier transport of the p-type injection layer 15, significantly improving the internal quantum efficiency and luminous output power of the deep ultraviolet light-emitting diode 100.

[0055] In step S200, the surface of the epitaxial structure 10 is cleaned using the UVC band. Specifically, under UVC band light irradiation, acetone and isopropanol are used for ultrasonic cleaning for 5 minutes each to remove organic matter from the surface of the epitaxial structure 10. Then, it is rinsed with deionized water for 5 minutes and spun dry.

[0056] In step S200, a second stepped channel 17 is formed by using positive photoresist as a mask and ICP (Inductively Coupled Plasma) etching.

[0057] In step S300, positive photoresist is used as a mask, and the distance between the mask and the sample is adjusted so that the photoresist has a certain angle on the mesa. The mesa structure is etched using a mixed atmosphere of BCl3 and Cl2 with a medium plasma. The second stepped channel 17 with a spacing of 0 μm to 10 μm between the bottom surface of the AlN intrinsic layer 12 and the top surface of the substrate layer 11 is etched.

[0058] The technical solution of this application will be further described below with reference to specific embodiments.

[0059] Example 1 Deep ultraviolet light-emitting diode 100 includes an epitaxial structure 10 and a composite functional layer 20. The epitaxial structure 10 includes a substrate layer 11, an AlN intrinsic layer 12, an n-type injection layer 13, a current spreading layer 18, a light-emitting layer 14, an electron blocking layer 19, and a p-type injection layer 15, which are stacked sequentially from bottom to top. A p-type electrode layer 30 is provided on the p-type injection layer 15, and an n-type electrode layer 40 is provided on the top surface of the n-type injection layer 13. The first stepped channel 16 of the epitaxial structure 10 is configured to be recessed downward from the top surface of the p-type injection layer 15 to the n-type injection layer 40. On the top surface of the implantation layer 13, the second stepped channel 17 is disposed on the side of the n-type electrode layer 40 away from the first stepped channel 16 and recessed downward from the top surface of the n-type implantation layer 13 to the AlN intrinsic layer 12. A composite functional layer 20 is respectively provided on the top surface of the p-type implantation layer 15, the surface of the p-type electrode layer 30, the first stepped channel 16 and the second stepped channel 17. Each composite functional layer 20 includes two insulating layers with different refractive indices on adjacent layers, and the distance between the bottom surface of the second stepped channel 17 and the top surface of the substrate layer 11 is 2 μm.

[0060] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the deep ultraviolet light-emitting diode 100 does not have a composite functional layer 20.

[0061] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the epitaxial structure 10 of the deep ultraviolet light-emitting diode 100 does not have a second stepped channel 17.

[0062] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the deep ultraviolet light-emitting diode 100 does not have a composite functional layer 20 and the epitaxial structure 10 does not have a second stepped channel 17.

[0063] Scanning electron microscopy (SEM) was performed on the deep ultraviolet light-emitting diode 100 of Example 1, and the results were as follows: Figure 9 The scanning electron microscope image shown.

[0064] like Figure 9 As shown, the composite functional layer 20 is located above the p-type electrode layer 30, and the second stepped channel 17 has a recessed structure facing the substrate layer 11. This structural feature is consistent with... Figure 1 The schematic structure shown Figure 1 This demonstrates that the deep ultraviolet light-emitting diode 100 device in this embodiment was successfully constructed and achieved the design requirements. Furthermore, the three-dimensional structure in the scanning electron microscope image verifies the precise stacking of the epitaxial layers, the control of the channel depth, and the configuration of the composite functional layer 20, thereby ensuring the optimized performance of the device in terms of optical and electrical properties.

[0065] Next, the luminous efficiency and reliability of the deep ultraviolet light-emitting diodes 100 of Example 1 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1.

[0066]

[0067] As shown in Table 1, the optical power of Example 1 is significantly higher than that of all comparative groups, indicating that the inclusion of the composite functional layer 20 and the design of the second stepped channel 17 in Example 1 effectively improves light extraction efficiency, reduces total internal reflection and light loss, and enhances light output. Comparative Examples 1 and 2 show a decrease compared to Example 1, indicating that adjusting the structure alone—i.e., omitting the composite functional layer 20 or the second stepped channel 17—has a certain negative impact on optical power. Furthermore, Example 1 exhibits a 92% retention rate after 3000 hours of aging at 60°C, significantly higher than Comparative Examples 1-3, indicating that the design of the composite functional layer 20 and the second stepped channel 17 significantly improves the device's reliability and better withstands degradation and performance decline under long-term high-temperature operating conditions. Moreover, the retention rates of the comparative groups are lower, especially Comparative Example 1, which lacks the composite functional layer 20 and is therefore more susceptible to thermal damage or stress during prolonged use, leading to a decrease in light output.

[0068] In summary, the composite functional layer 20, through refractive index modulation and effective optical isolation, can improve light extraction efficiency, reduce total internal reflection, and enhance the thermal stability and reliability of the device, resulting in Example 1 exhibiting higher optical power and aging retention compared to other comparative groups. Furthermore, the second-stepped channel 17 effectively reduces total internal reflection between the n-type injection layer 13 and the AlN intrinsic layer 12, while optimizing the light guiding path, thereby improving light extraction efficiency.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A deep ultraviolet light-emitting diode, characterized in that, The deep ultraviolet light-emitting diode includes an epitaxial structure and a composite functional layer. The epitaxial structure includes a substrate layer, an AlN intrinsic layer, an n-type injection layer, a light-emitting layer, and a p-type injection layer arranged sequentially from bottom to top. A p-type electrode layer is provided on the p-type injection layer, and an n-type electrode layer is provided on the top surface of the n-type injection layer. The epitaxial structure further includes a first stepped channel and a second stepped channel with a stepped structure. The first stepped channel is configured to be recessed from the top surface of the p-type implanted layer to the top surface of the n-type implanted layer. The second stepped channel is disposed on the side of the n-type electrode layer away from the first stepped channel and is recessed from the top surface of the n-type implanted layer to the AlN intrinsic layer. At least one layer of the composite functional layer is respectively provided on the top surface of the p-type implanted layer, the surface of the p-type electrode layer, the first stepped channel, and the second stepped channel. Each layer of the composite functional layer includes at least two insulating layers with different refractive indices on adjacent layers. The distance between the bottom surface of the second stepped channel and the top surface of the substrate layer is any value between 0 μm and 10 μm.

2. The deep ultraviolet light-emitting diode according to claim 1, characterized in that, The p-type electrode layer includes: p-type contact electrode, located above the p-type injection layer; At least one thickened electrode is located on the surface of the p-type contact electrode, and the composite functional layer is provided between the p-type contact electrode and the thickened electrode and / or two adjacent thickened electrodes.

3. The deep ultraviolet light-emitting diode according to claim 2, characterized in that, The minimum width of two adjacent second-step channels is greater than or equal to 0.2 μm.

4. The deep ultraviolet light-emitting diode according to claim 3, characterized in that, The insulating layer is made of any one of SiO2, Al2O3, TiO2, and Ta2O5.

5. The deep ultraviolet light-emitting diode according to claim 4, characterized in that, The insulating layers with different refractive indices are obtained by using the same material but different manufacturing processes or are composed of different materials.

6. The deep ultraviolet light-emitting diode according to claim 5, characterized in that, The preparation process of the insulating layer includes plasma-enhanced chemical vapor deposition or atomic layer deposition.

7. The deep ultraviolet light-emitting diode according to any one of claims 1-6, characterized in that, The number of layers in the composite functional layer is any value between 2 and 200.

8. The deep ultraviolet light-emitting diode according to claim 7, characterized in that, The bottom surface of the first or second stepped channel can be any one of a plane, an angle, or a circular arc.

9. The deep ultraviolet light-emitting diode according to claim 8, characterized in that, The Al composition in the n-type implanted layer is any value between 20% and 90%, and the thickness is any value between 500nm and 4000nm.

10. The deep ultraviolet light-emitting diode according to claim 9, characterized in that, The thickness of the intrinsic AlN layer is any value between 500nm and 4000nm.

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