Multicolor LED monolithic integrated structure and preparation method

Abstract

The present application relates to the field of semiconductor light emitting, in particular to a multi-color LED monolithic integrated structure and a preparation method. The multi-color LED monolithic integrated structure comprises: a substrate, a surface of the substrate comprising at least one undoped nitride layer and at least one N-type nitride buried layer in sequence; and the surface of the substrate comprising a red / green / blue three-color LED structure array epitaxial structure, and the N-type nitride buried layer under at least one of the red / green / blue three-color LED structure array is a porous nitride buried layer. The technical solution solves the technical problems of low In component and strong polarization field of the nitride-based red light LED epitaxy, suppresses / reduces the quantum confinement Stark effect (QSCE), improves the growth quality of the three-color LED, improves the internal quantum efficiency, improves the wavelength stability, display color gamut and color purity; the double-color synchronous epitaxy and single-color separate epitaxy are adopted, the stress accumulation and optical crosstalk bottleneck of the vertical stacked three-color integrated architecture are broken, and the complex process of the traditional multi-color integration is simplified.

Description

Technical Field

[0001] This invention relates to the field of semiconductor light emission, and more particularly to a multi-color LED monolithic integrated structure and its fabrication method. Background Technology

[0002] As a highly efficient optoelectronic device, light-emitting diodes (LEDs) have demonstrated enormous application potential in several cutting-edge technology fields. For example, in lighting, LEDs have become the mainstream choice for green lighting due to their high energy efficiency and long lifespan. In display technology, the rapidly developing Micro-LED display technology, with its high brightness, high contrast, and low power consumption, is widely considered the core direction of next-generation display technology. Furthermore, LEDs play a crucial role in optical communication and optical interconnection, supporting high-speed data transmission and low-latency communication, providing key technological support for 5G and even 6G network infrastructure. However, despite their broad application prospects, the industry still faces a series of technical challenges, one of which is how to achieve efficient three-color monolithic integrated chips and related technologies for full-color display applications. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a multi-color LED monolithic integrated structure and a preparation method, which can effectively solve the problems of complex process and poor light color uniformity of multi-color LED chips in the prior art.

[0004] To address the aforementioned problems, this invention provides a method for fabricating a multi-color LED monolithic integrated structure, comprising the following steps: providing a substrate, the surface of which sequentially includes at least one undoped nitride layer and at least one N-type nitride buried layer; forming multiple regions for growing LED structures by etching; forming porous nitride layers in a portion of the N-type nitride buried layer on the substrate by selective area protection, wherein the stress release effect of the porous nitride layer can improve the incorporation rate of the epitaxial In component; utilizing the stress release effect of the porous nitride, epitaxially growing blue / green or red / green LED structures in the regions for growing LED structures, and separately growing red or blue LED structures to form a red / green / blue tri-color LED array epitaxial structure.

[0005] Optionally, the substrate may further include multiple substrate DBR layers, each corresponding to one of the three colors: red, green, and blue.

[0006] Optionally, the method further includes the following steps: forming a transparent electrode on the surface of the red / green / blue tri-color LED array epitaxial structure; forming a step on the side of the red / green / blue tri-color LED array epitaxial structure; forming a passivation layer and patterning it on the surface of the step; and forming a metal electrode on the surface of the red / green / blue tri-color LED array epitaxial structure to realize monolithic integrated red / green / blue tri-color LEDs.

[0007] Optionally, the following steps may also be included: depositing a surface DBR layer on the transparent electrode surface to form a resonance with the substrate DBR layer, controlling the angle of LED emission to make it smaller, so as to increase the coupling efficiency between the LED and the optical waveguide or optical fiber.

[0008] Optionally, the step of forming the epitaxial structure of the red / green / blue tri-color LED array further includes: selectively protecting the region where blue light is to be formed; etching the N-type nitride buried layer in the region where red and green light are to be formed to form a porous nitride buried layer; selectively protecting the region where red light is to be formed; utilizing the stress release effect of the porous nitride to increase the incorporation rate of the epitaxial component, while epitaxially growing blue / green LED structures, wherein the region where the porous nitride buried layer is formed forms a green LED structure; selectively protecting the region where the blue / green LED structure has already been grown; and epitaxially forming a red LED structure.

[0009] Optionally, before the step of selecting and protecting the area to be formed of blue light, the method further includes: selecting and protecting the areas to be formed of red and green light; etching the N-type nitride buried layer in the area to be formed of blue light to form a porous nitride buried layer, wherein the porosity of the porous nitride buried layer formed in this step is less than the porosity of the porous nitride buried layer formed by etching the N-type nitride buried layer in the area to be formed of red and green light.

[0010] Optionally, the step of forming the epitaxial structure of the red / green / blue tri-color LED array further includes: selectively protecting the regions where blue and green light are to be formed; etching the N-type nitride buried layer in the region where red light is to be formed to form a porous nitride buried layer; selectively protecting the regions where red and green light are to be formed; epitaxially forming a blue LED structure; selectively protecting the regions where the blue LED structure has already been grown; utilizing the stress release effect of the porous nitride to increase the incorporation rate of the epitaxial component, while epitaxially growing red / green LED structures, wherein the regions where the porous nitride buried layer is formed form the red LED structure.

[0011] Optionally, the selected area protection adopts the method of forming a protective layer on the surface to wrap the protected area, and the protective layer material is SiO2.

[0012] Optionally, the nitride is GaN, AlN, AlGaN, or InGaN.

[0013] Alternatively, porous nitrides can be prepared by depositing metal on the surface and performing anodizing.

[0014] To address the aforementioned issues, this invention provides a multi-color LED monolithic integrated structure, comprising: a substrate, wherein the surface of the substrate sequentially includes at least one undoped nitride layer and at least one N-type nitride buried layer; the surface of the substrate includes an epitaxial structure of a red / green / blue tri-color LED array, wherein the N-type nitride buried layer beneath at least one of the red / green / blue tri-color LED arrays is a porous nitride buried layer.

[0015] Optionally, the substrate may further include multiple substrate DBR layers, each corresponding to one of the three colors: red, green, and blue.

[0016] Optionally, a transparent electrode is also included on the surface of the red / green / blue tri-color LED array epitaxial structure. A surface DBR layer is included on the surface of the transparent electrode, which resonates with the substrate DBR layer to control the angle of LED emission and make it smaller, thereby increasing the coupling efficiency between the LED and the optical waveguide or optical fiber.

[0017] The proposed multi-color LED monolithic integration structure and fabrication method solves the technical challenges of low In composition and strong polarization field in nitride-based red LED epitaxy, suppresses / reduces the quantum confinement Stark effect (QSCE), improves the growth quality of the three-color LEDs, enhances internal quantum efficiency, and improves wavelength stability, display color gamut, and color purity. By employing simultaneous dual-color epitaxy and individual single-color epitaxy, the method overcomes the stress accumulation and optical crosstalk bottlenecks in vertically stacked three-color integration architectures, simplifying the complex processes of traditional multi-color integration. The method utilizes the stress release effect of porous nitride layers to increase the In composition incorporation rate, and combines selective area protection and step-by-step epitaxy to achieve monolithic integration of red, green, and blue LEDs. This method forms a porous nitride buried layer through etching, weakening the quantum confinement Stark effect and solving the technical challenge of low In composition in nitride-based red LED epitaxy, thus improving the growth quality and color uniformity of the three-color LEDs. The simultaneous dual-color epitaxy and individual single-color epitaxy simplify the complex processes of traditional multi-color integration and reduce losses in the packaging stage.

[0018] Furthermore, the resonant cavity structure formed by the substrate and the surface DBR layer can regulate the narrow-angle light emission of the LED, improving its coupling efficiency with optical waveguides and optical fibers, and adapting it to application scenarios such as optical communication and Micro-LED displays. In addition, the process uses a passivation layer to repair etching damage and optimizes electrode fabrication, further improving the luminous efficiency and electrical performance of the LED. It is also compatible with various nitride materials such as GaN and InGaN, as well as Mini / Micro-LED structures, making it widely applicable and providing an efficient and feasible technical solution for the industrialization of full-color LED integrated chips.

[0019] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Appendix Figure 1 The diagram shows the implementation steps of a method for fabricating a multi-color LED monolithic integrated structure according to a specific embodiment of the present invention.

[0022] Appendix Figure 2A To be continued Figure 2H The diagram shown is a process flow chart of the fabrication method of the multi-color LED monolithic integrated structure according to a specific embodiment of the present invention.

[0023] Appendix Figure 3 The diagram shown is a structural schematic of the multi-color LED monolithic integrated structure according to a specific embodiment of the present invention.

[0024] Appendix Figure 4A To be continued Figure 4E The diagram shows the implementation steps of a method for fabricating a multi-color LED monolithic integrated structure according to a specific embodiment of the present invention.

[0025] Appendix Figure 5 The diagram shows the implementation steps of a method for fabricating a multi-color LED monolithic integrated structure according to a specific embodiment of the present invention.

[0026] Appendix Figure 6A To be continued Figure 6H The diagram shown is a process flow chart of the fabrication method of the multi-color LED monolithic integrated structure according to a specific embodiment of the present invention.

[0027] Appendix Figure 7 The diagram shown is a schematic representation of the optional steps in the fabrication method of the multi-color LED monolithic integrated structure according to a specific embodiment of the present invention.

[0028] Appendix Figure 8A and 8B The diagram shown is a process flow chart of optional steps in the fabrication method of the multi-color LED monolithic integrated structure according to a specific embodiment of the present invention.

[0029] Appendix Figure 9The diagram shown is a structural schematic of the multi-color LED monolithic integrated structure according to a specific embodiment of the present invention.

[0030] Appendix Figure 10 The diagram shown is a schematic diagram of the substrate structure of the multi-color LED monolithic integrated structure according to a specific embodiment of the present invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Appendix Figure 1 The diagram shown illustrates the implementation steps of a method for fabricating a multi-color LED monolithic integrated structure according to a specific embodiment of the present invention. (See attached diagram.) Figure 1 As shown, the method described in this specific embodiment includes: Step S100, providing a substrate, the surface of which includes an undoped nitride layer, the undoped nitride layer including an N-type buried nitride layer; Step S110, forming multiple regions for growing LED structures by etching; Step S121, selectively protecting regions intended to form blue light; Step S122, etching the N-type buried nitride layer in regions intended to form red and green light to form porous buried nitride layers; Step S123, selectively protecting regions intended to form red light; Step S124, utilizing the stress release effect of porous nitride to increase the incorporation rate of the epitaxial layer, while epitaxially growing blue / green LED structures, wherein regions with porous buried nitride layers are formed. Step S125: Selectively protect the area where the blue / green LED structure has already grown; Step S126: Epitaxially form a red LED structure; Step S131: Form a transparent electrode on the surface of the red / green / blue tri-color LED array epitaxial structure; Step S132: Form a step on the side of the red / green / blue tri-color LED array epitaxial structure; Step S133: Form a passivation layer and pattern it on the surface of the step; Step S134: Form a metal electrode on the surface of the red / green / blue tri-color LED array epitaxial structure to achieve monolithic integrated red / green / blue tri-color LED; Step S140: Deposit a surface DBR layer on the transparent electrode surface to resonate with the substrate DBR layer, control the LED emission angle to make it smaller, and increase the coupling efficiency between the LED and the optical waveguide or optical fiber.

[0033] This specific embodiment uses GaN as an example of a nitride. It should be noted that in other embodiments, any material such as GaN, AlN, AlGaN, or InGaN capable of forming an LED light-emitting structure should be considered an equivalent alternative.

[0034] The LED described in this specific embodiment may include any LED structure commonly found in the art, such as ordinary LED, mini-LED, micro-LED, and nano-LED, with micro-LED being particularly suitable for the solution described in this specific embodiment.

[0035] Appendix Figure 2A As shown, referring to step S100, a substrate 10 is provided, the surface of which sequentially includes at least one undoped nitride layer 101 and at least one N-type buried nitride layer 102. The substrate 10 can be a sapphire or GaN substrate, and the undoped nitride layer 101 (UID-GaN) and the N-type buried nitride layer 102 (n-GaN) are sequentially grown on the substrate surface. Further, as shown in the attached... Figure 10 As shown, the substrate bottom layer can be pre-fabricated with distributed Bragg reflector layers 801, 802, and 803 (DBR) composed of alternating groups of undoped GaN and n-GaN, respectively, to achieve high reflectivity for specific wavelengths of red, green, and blue light, laying the structural foundation for subsequent narrow-angle light emission. Another objective of this design is to address the varying cavity length requirements of multi-wavelength resonant cavity LEDs. Red, green, and blue have inherent differences in cavity length (assuming constant refractive index, L∝λ), with red light having a cavity length (630nm) approximately 40% longer than blue light (450nm). Existing monolithic integration technology struggles to simultaneously meet the cavity length requirements of all three colors on the same epitaxial structure, leading to a mismatch between the resonant cavity's longitudinal mode and the emission peak, affecting color purity and light extraction efficiency. (See attached image.) Figure 2B As shown, referring to step S110, multiple regions 111, 112, and 113 for growing LED structures are formed by etching and segmentation. This step can use ICP dry etching combined with photolithography to etch and segment the substrate, forming multiple array-like micro-mesa regions for independently growing LED structures. The etching depth reaches the UID-GaN layer, precisely controlling the size and spacing of the micro-mesa to form a regular LED array substrate.

[0036] Appendix Figure 2C As shown, referring to step S121, the region 113 where blue light is to be formed is selected for protection. A SiO2 protective layer 120 is deposited on the substrate surface by PECVD or vapor deposition process, and patterning is performed by conventional photolithography and etching processes to achieve selective protection of the region where blue light is to be formed, so that the N-type nitride buried layer in this region is not processed by subsequent processes.

[0037] Appendix Figure 2DAs shown, referring to step S122, the N-type nitride buried layer 102 in the region 111 where red light is to be formed and the region 112 where green light is to be formed are etched to form a porous nitride buried layer 130. This step can employ electrochemical etching or chemical etching processes to etch the unprotected N-type nitride buried layer 102 in the region 111 where red light is to be formed and the region 112 where green light is to be formed. For example, porous nitrides can be prepared by depositing metal on the surface and performing anodizing. After etching, a porous nitride buried layer 130 (NP-GaN) is formed. The porous structure changes the refractive index of the nitride, while providing a stress release mechanism for subsequent epitaxial growth.

[0038] Appendix Figure 2E As shown, referring to step S123, the selected area 111 to form red light is protected. A new SiO2 selected area protection layer is prepared again through the SiO2 evaporation and patterned photolithography etching process as before, to fully cover and protect the area 111 to form red light, preventing it from participating in the epitaxial growth of the blue / green LED structure.

[0039] Appendix Figure 2F As shown, referring to step S124, the stress-relieving effect of porous nitrides is used to improve the In component incorporation rate of epitaxy, while simultaneously growing a blue LED structure 143 and a green LED structure 142. The region where the porous nitride buried layer is formed forms the green LED structure 142. Epitaxial growth is performed on the substrate treated as described above using epitaxial growth processes such as MOCVD or MBE. The stress-relieving effect of the porous nitride buried layer weakens the quantum confinement Stark effect (QCSE), effectively improving the In component incorporation rate of multiple quantum wells (MQWs) during epitaxy, achieving simultaneous epitaxial growth of blue / green LED structures. The green light-forming region, pre-formed with a porous nitride buried layer, grows into the green LED structure 142 due to efficient In component incorporation, while the blue light-forming region, where no porous structure is formed, grows into the blue LED structure 143.

[0040] Appendix Figure 2G As shown, referring to step S125, a selective protection layer is prepared for the areas where the blue LED structure 143 and the green LED structure 142 have been grown. A SiO2 evaporation and patterning etching process is used again to prepare a selective protection layer, providing full coverage protection for the areas where the grown blue LED structure 143 and the green LED structure 142 have been completed, preventing them from being damaged during the red light epitaxy process.

[0041] Appendix Figure 2HAs shown, referring to step S126, a red LED structure 141 is epitaxially formed. MOCVD or MBE epitaxial growth processes are then used to perform epitaxial growth in the unprotected red light-forming region. Utilizing the stress release of the porous nitride buried layer and the solubilizing effect of the In component, a high-quality InGaN-based red LED structure is epitaxially formed.

[0042] After the above steps are completed, the epitaxial structure fabrication of the red, green, and blue LED array is finished. For a specific implementation of the obtained multi-color LED monolithic integrated structure, please refer to the appendix. Figure 3 As shown, the method includes: a substrate 10, the surface of which includes an undoped nitride layer 101, the undoped nitride layer including an N-type nitride buried layer 102; the substrate surface includes epitaxial structures 141, 142, and 143 of a red / green / blue tri-color LED array, wherein the N-type nitride buried layer beneath at least one of the red / green / blue tri-color LED arrays is a porous nitride buried layer 130. In this specific embodiment, corresponding to the specific implementation of the method, the N-type nitride buried layers beneath the red LED structure 141 and the green LED structure 142 both include a porous nitride buried layer 130.

[0043] The dimensions of the red, green, and blue LED epitaxial structures 141, 142, and 143 can be flexibly and precisely adjusted according to actual application requirements. For example, in a specific design, the epitaxial structure 141 in the red light region can be adjusted into two separate sub-structure units. These two sub-structure units form a centrally symmetrical distribution pattern with the blue and green light regions (i.e., 142 and 143). This symmetrical separation design can effectively optimize the stress state generated during the epitaxial layer growth process and subsequent device operation. Specifically, the separated red light substructures can reduce direct stress transfer and interaction with adjacent blue and green light structures, while the centrally symmetrical layout helps to homogenize the stress distribution across the entire epitaxial wafer, thereby reducing the probability of crystal defects caused by stress concentration and improving the luminous efficiency and long-term reliability of the device.

[0044] It should be noted that any alternative to the above-mentioned scheme, but the essence of the technical concept lies in forming a porous nitride layer by etching a portion of the N-type nitride buried layer on the substrate through selective area protection. The stress release effect of the porous nitride layer can improve the incorporation rate of the epitaxial In component. By utilizing the stress release effect of the porous nitride, blue / green or red / green LED structures can be epitaxially grown simultaneously in the area used for growing LED structures, and red or blue LED structures can be grown separately to form a red / green / blue tri-color LED array epitaxial structure. All such generalized technical solutions should be regarded as equivalent replacements of the above-mentioned technical solutions.

[0045] After the above steps are completed, you can continue with the following steps to obtain a better structure.

[0046] To illustrate the structure more clearly, the following figures are presented in sectional view.

[0047] Appendix Figure 4A As shown, referring to step S131, a transparent electrode 150 is formed on the surface of the red / green / blue tri-color LED array epitaxial structure. The transparent electrode 150 can be deposited on the p-(In)GaN surface of the red / green / blue tri-color LED array epitaxial structure using magnetron sputtering or electron beam evaporation processes. The transparent electrode 150 is made of ITO or a thin metal material to ensure high light transmittance and electrode conductivity. For simplicity, the DBR layer of the substrate is not shown; see Figure 8 for the specific structure.

[0048] Appendix Figure 4B As shown, referring to step S132, steps are formed on the side of the red / green / blue tri-color LED array epitaxial structure. A dry etching process is used to etch the side of the red / green / blue tri-color LED array epitaxial structure to form stepped steps. After etching, an alkaline solution such as KOH or TMAH is used for wet treatment of the mesa sidewalls to repair the sidewall etching damage caused during the dry etching process, reduce non-radiative recombination caused by sidewall defects, and improve LED luminous efficiency.

[0049] Appendix Figure 4C As shown, referring to step S133, a passivation layer 151 is formed and patterned on the surface of the step. Passivation layer material is deposited on the surface of the step and the LED structure using processes such as ALD and PECVD. The passivation layer is made of materials such as SiO2, SiN, or Al2O3. After forming a high-quality passivation layer, the passivation layer is patterned using photolithography and wet / dry etching processes to remove part of the passivation layer on the transparent electrode and the n-layer surface, reserving contact areas for subsequent metal electrode fabrication.

[0050] Appendix Figure 4D As shown, referring to step S134, metal electrodes 152 are formed on the surface of the red / green / blue tri-color LED array epitaxial structure to achieve monolithic integration of red / green / blue tri-color LEDs. Using electron beam evaporation or magnetron sputtering processes, metal deposition is performed in the reserved contact areas of the patterned red / green / blue tri-color LED array epitaxial structure to form p-type and n-type metal contacts, respectively, thus fabricating metal electrodes and completing the electrical interconnection of the red / green / blue tri-color LEDs, achieving monolithic integration of red / green / blue tri-color LED chips.

[0051] Appendix Figure 4EAs shown, referring to step S140, a surface DBR layer 160 is deposited on the transparent electrode surface to form a resonance with the substrate DBR layer, controlling the LED emission angle to make it smaller, thereby increasing the coupling efficiency between the LED and the optical waveguide or optical fiber. A dielectric DBR is deposited on the surface of the chip ITO transparent electrode, forming a resonant cavity structure with the substrate's underlying DBR, which modulates the LED emission direction, achieving narrow-angle emission and improving the coupling efficiency with the optical waveguide or optical fiber.

[0052] After the above steps are completed, the resulting multi-color LED monolithic integrated structure is preferably further comprising multiple substrate DBR layers, corresponding to red, green, and blue respectively. A transparent electrode is also included on the surface of the red / green / blue LED array epitaxial structure, and a surface DBR layer is included on the surface of the transparent electrode, resonating with the substrate DBR layer to control the LED emission angle and reduce it, thereby increasing the coupling efficiency between the LED and the optical waveguide or optical fiber.

[0053] Appendix Figure 5 The diagram shown illustrates the implementation steps of a method for fabricating a multi-color LED monolithic integrated structure according to a specific embodiment of the present invention. (See attached diagram.) Figure 5 As shown, the method described in this specific embodiment includes: Step S200, providing a substrate, the surface of which includes an undoped nitride layer, the undoped nitride layer including an N-type nitride buried layer; Step S210, forming multiple regions for growing LED structures by etching; Step S221, selectively protecting regions intended to form blue and green light; Step S222, etching the N-type nitride buried layer in the region intended to form red light to form a porous nitride buried layer; Step S223, selectively protecting regions intended to form red and green light; Step S224, epitaxially forming a blue LED structure; Step S225, selectively protecting the region where a blue LED structure has already been grown; Step S226, utilizing the stress release effect of the porous nitride to increase the In component incorporation rate of the epitaxial layer, while epitaxially growing a red / green LED structure, wherein the region where the porous nitride buried layer is formed forms a red LED structure.

[0054] This specific embodiment is also described using GaN. In other specific embodiments, nitride materials such as GaN, AlN, AlGaN, AlInN or InGaN that can form LED light-emitting structures are all considered as equivalent alternatives and are not limited thereto.

[0055] Appendix Figure 6AAs shown, referring to step S200, a substrate 20 is provided. The surface of the substrate 20 includes an undoped nitride layer 201, which includes an N-type buried nitride layer 202. The substrate 20 can be a sapphire substrate or a GaN homogeneous substrate. The bottom layer of the substrate is pre-prepared with a substrate DBR layer formed by alternating stacks of multiple sets of undoped GaN and n-GaN. This substrate DBR layer can achieve high reflectivity for specific wavelengths of red, green, and blue light, respectively, thus constructing a basic resonant structure for subsequent narrow-angle LED light emission. The surface layer of the substrate 20 is sequentially grown to form an undoped nitride layer 201 (UID-GaN), and an N-type buried nitride layer 202 (n-GaN) is embedded in the undoped nitride layer 201, providing structural support for subsequent porous structure fabrication and LED epitaxial growth.

[0056] Appendix Figure 6B As shown, referring to step S210, multiple regions 211, 212, and 213 for growing LED structures are formed through etching. Region 211 is the region to be formed for red light, region 212 is the region to be formed for green light, and region 213 is the region to be formed for blue light. This step uses ICP dry etching combined with high-precision photolithography to pattern and etch the substrate 20. The etching depth is accurate down to the undoped nitride layer 201. By adjusting the etching parameters, the size, spacing, and sidewall perpendicularity of each micro-mesa region are precisely controlled to form an array of independent LED structure growth micro-mesa, constructing a regular LED array substrate and ensuring the independence and consistency of subsequent three-color LED structure growth.

[0057] As shown in Figure 6C, referring to step S221, the regions 213 and 212 intended to form blue light and green light are selected for protection. A SiO2 protective layer 220 is uniformly deposited on the substrate 20 and the surface of each micro-mesa using PECVD or electron beam evaporation. The patterning design is completed using conventional photolithography processes such as photoresist coating, exposure, and development. Then, a dry etching process is used to remove the SiO2 layer in the unprotected areas, leaving only the SiO2 protective layer 220 on the surfaces of the regions intended to form blue and green light. This achieves full-coverage protection of these two regions, completely isolating the N-type nitride buried layer 202 within these areas from subsequent etching processes and preventing it from being etched and modified.

[0058] Appendix Figure 6DAs shown, referring to step S222, the N-type nitride buried layer 202 in the region 211 where red light is to be formed is etched to form a porous nitride buried layer 230. This step targets the region 211 where red light is to be formed, which is not covered by the SiO2 protective layer 220. A porous nitride is prepared using a process of surface metal deposition followed by anodic oxidation. Alternatively, electrochemical etching or chemical etching can be used to complete the etching. After etching, a porous nitride buried layer 230 (NP-GaN) is formed at the N-type nitride buried layer position in the region 211 where red light is to be formed. This porous structure can change the refractive index of the nitride substrate and simultaneously construct stress relief channels, providing structural conditions for increasing the In composition incorporation rate during subsequent epitaxial growth.

[0059] As shown in Figure 6E, referring to step S223, the selected protection areas 211 and 212, which are intended to form red light, are protected. After the porous nitride buried layer 230 is prepared, the same SiO2 evaporation, photolithography, and etching processes as in step S221 are used again to prepare a new SiO2 selected protection layer 221, which fully covers and protects the areas 211 and 212, which are intended to form red light. This isolates these two areas from the subsequent blue LED epitaxial growth process, preventing the epitaxial material from growing irregularly in these areas and ensuring the directional growth of the blue LED structure.

[0060] As shown in Figure 6F, referring to step S224, a blue LED structure 243 is epitaxially formed. Using MOCVD or MBE epitaxial growth processes, directional epitaxial growth is performed in the blue light-forming region 213, which is not protected by the SiO2 protective layer 221. The core structures, including an n-type GaN layer, a multi-quantum-well emitting layer, and a p-type GaN layer, are grown sequentially to prepare a high-quality blue LED structure 243. During the epitaxial process, the growth temperature, reactive gas flow rate, and growth rate are precisely controlled to ensure the crystal quality and luminous performance of the blue LED structure. After epitaxy, all SiO2 protective layers on the surface are removed.

[0061] Appendix Figure 6G As shown, referring to step S225, the area where the blue LED structure 243 has already grown is selected for protection. A protective layer is deposited again on the substrate and the surface of each array region using the SiO2 evaporation process. Combined with photolithography and etching processes, patterning is completed to prepare the SiO2 selected area protection layer 222, which provides full coverage protection for the grown blue LED structure 243, preventing it from being eroded by plasma and reactive gases during the subsequent epitaxial growth of red and green LEDs, and avoiding damage to the crystal quality and electrical performance of the blue LED structure.

[0062] As shown in Figure 6H, referring to step S226, the stress release effect of porous nitride is used to improve the incorporation rate of the In component in the epitaxial layer, and red LED structure 241 and green LED structure 242 are epitaxially grown. In this process, the region 211 where the porous nitride buried layer 230 is formed forms the red LED structure 241. Continuing with MOCVD or MBE epitaxial growth processes, epitaxial growth is simultaneously performed in the red light-forming region 211 and the green light-forming region 212, which are not protected by the SiO2 protective layer 222. During the epitaxial process, the porous nitride buried layer 230 beneath the red light-forming region 211 plays a stress-relieving role, effectively weakening the quantum confinement Stark effect (QCSE) and significantly increasing the In composition incorporation rate during the multiple quantum well (MQW) growth process, meeting the high In composition requirement of red LEDs, thereby growing a red LED structure 241 in this region. The green light-forming region 212, relying on the structural support of the conventional nitride buried layer, grows a green LED structure 242 under matched epitaxial parameters, ultimately completing the fabrication of the red, green, and blue LED array epitaxial structure on the same substrate.

[0063] Continue to refer to the appendix Figure 7 The diagram shown illustrates supplementary steps of a specific embodiment of the present invention. Before the implementation of the above-mentioned reference step S121 or reference step S221, i.e., before the selected area protection step, the method may further include: step S301, selecting and protecting the areas intended to form red and green light; and step S302, etching the N-type nitride buried layer in the area intended to form blue light to form a porous nitride buried layer. The porosity of the porous nitride buried layer formed in this step is less than the porosity of the porous nitride buried layer formed by etching the N-type nitride buried layer in the area intended to form red and green light.

[0064] Appendix Figure 8A As shown, referring to step S301, the selected area 311, which is intended to form red light, and the area 312, which is intended to form green light, are protected. The method and materials for selected area protection are described above.

[0065] Appendix Figure 8B As shown, referring to step S302, the N-type nitride buried layer in the region 313 where blue light is to be formed is etched to form a porous nitride buried layer 330. The porosity of the porous nitride buried layer formed in this step is less than the porosity of the porous nitride buried layers 130 and 230 formed by etching the N-type nitride buried layers in the regions where red and green light are to be formed.

[0066] Increasing porosity in all regions to form a porous structure allows for stress modulation through porous materials, effectively suppressing the quantum confinement Stark effect (QSCE). Specifically, the introduction of a porous structure provides a release channel for stress caused by lattice mismatch, reduces the built-in electric field in the active quantum well, and thus mitigates the adverse effects of QSCE on carrier recombination efficiency and emission wavelength. The pore size can be adjusted through process control, such as etching time, anodizing voltage, or oxide concentration. When using etching, extending the etching time usually results in a more complete etching reaction, leading to larger pore sizes; conversely, shortening the etching time results in smaller pores. For anodizing, higher voltage increases the electric field strength, promoting oxidation and pore expansion, potentially forming larger pores; while lower voltage may result in smaller pore sizes. Changes in oxide concentration also affect the reaction rate and product dissolution rate; higher oxide concentrations may accelerate pore formation and growth, increasing pore sizes, while lower concentrations may result in smaller pores. The porosity of the porous nitride buried layer formed in this step is lower than that of the porous nitride buried layers 130 and 230 formed by the subsequent etching of the N-type nitride buried layer in the regions where red and green light are to be generated. When the porosity of the porous structure decreases, the quantum well In incorporation rate decreases, thereby affecting the emission wavelength. Therefore, by controlling the porosity, the emission wavelength of the LED can be adjusted within a certain range, achieving the purpose of controlling the LED wavelength.

[0067] After the above steps are completed, the epitaxial growth of red, green, and blue LED arrays on a monolithic substrate is achieved through a combination of selective area protection and porous nitride buried layer modification. In the two multi-color LED monolithic integration fabrication schemes, this scheme differs slightly in the protection and growth sequence from the previous scheme, but both employ the technical concept of using selective area protection combined with porous nitride buried layer modification to regulate the In composition to achieve monolithic integration.

[0068] For a specific implementation of the obtained multi-color LED monolithic integrated structure, please refer to the appendix. Figure 9 As shown, the system includes: a substrate 20, the surface of which includes an undoped nitride layer 201, the undoped nitride layer including an N-type nitride buried layer 202; the substrate surface includes epitaxial structures 241, 242, and 243 of a red / green / blue tri-color LED array, wherein the N-type nitride buried layer beneath at least one of the red / green / blue tri-color LED arrays is a porous nitride buried layer 230. In this specific embodiment, corresponding to the specific implementation of the method, only the N-type nitride buried layer beneath the red LED structure 241 is a porous nitride buried layer 230.

[0069] Therefore, any three-color LED fabrication scheme that is based on the core concept of this invention, prepares a porous nitride layer in a partial area through selective protection, and utilizes its stress release effect to increase the incorporation rate of the In component, thereby achieving simultaneous epitaxy of two colors and separate epitaxy of a single color, is considered an equivalent alternative to this invention and falls within the protection scope of this invention.

[0070] After the above steps are completed, in order to obtain a better structure, the transparent electrode and DBR growth steps can be carried out as in the previous specific implementation method, which will not be repeated here.

[0071] It should be noted that references to "an embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," etc., in the specification indicate that the described embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure, or characteristic is described in connection with an embodiment, whether explicitly described or not, implementing such a feature, structure, or characteristic in conjunction with other embodiments is within the knowledge of those skilled in the art.

[0072] It should be noted that the terms "comprising" and "having," and their variations, used in this invention document are intended to cover non-exclusive inclusion. The terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence, unless explicitly indicated by the context. It should be understood that such data used interchangeably where appropriate. Furthermore, embodiments and features within embodiments of this invention can be combined with each other unless otherwise specified. In addition, descriptions of well-known components and technologies have been omitted in the above description to avoid unnecessarily obscuring the concepts of this invention. In the various embodiments described above, each embodiment focuses on the differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0073] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a multi-color LED monolithic integrated structure, characterized in that, Includes the following steps: A substrate is provided, wherein the surface of the substrate sequentially includes at least one undoped nitride layer and at least one N-type nitride buried layer; Multiple regions for growing LED structures are formed by etching and segmentation. By selective area protection, a porous nitride layer is formed by etching a portion of the N-type nitride buried layer on the substrate. The stress relief effect of the porous nitride layer can improve the incorporation rate of the epitaxial In composition. By utilizing the stress-relieving effect of porous nitrides, blue / green or red / green LED structures are epitaxially grown in the region used for growing LED structures, and red or blue LED structures are grown separately to form a red / green / blue tricolor LED array epitaxial structure.

2. The method according to claim 1, characterized in that, The substrate also includes multiple substrate DBR layers, corresponding to the three colors of red, green and blue, respectively.

3. The method according to claim 1, characterized in that, It also includes the following steps: A transparent electrode is formed on the surface of the epitaxial structure of the red / green / blue tri-color LED array; Steps are formed on the side of the epitaxial structure of the red / green / blue LED array; A passivation layer is formed and patterned on the surface of the step; Metal electrodes are formed on the surface of the epitaxial structure of the red / green / blue tri-color LED array to achieve monolithic integration of red / green / blue tri-color LEDs.

4. The method according to claim 3, characterized in that, It also includes the following steps: A surface DBR layer is deposited on the transparent electrode surface to resonate with the substrate DBR layer, thereby controlling the angle of LED emission and making it smaller to increase the coupling efficiency between the LED and the optical waveguide or optical fiber.

5. The method according to claim 1, characterized in that, The steps for forming the epitaxial structure of the red / green / blue tri-color LED array further include: Select areas are protected to prevent the formation of blue light. The N-type nitride buried layer in the region where red and green light are to be generated is etched to form a porous nitride buried layer; The constituency protects the area where red light is expected to be generated; The stress-relieving effect of porous nitrides is used to improve the incorporation rate of In components in epitaxy, while blue / green LED structures are epitaxially grown, in which the region where the porous nitride buried layer is formed forms the green LED structure. Select areas to protect where blue / green LED structures have already been grown; The epitaxial layer forms a red LED structure.

6. The method according to claim 1, characterized in that, The steps for forming the epitaxial structure of the red / green / blue tri-color LED array further include: The constituency protects areas where blue and green light are expected to be generated. The N-type nitride buried layer in the region where red light is to be generated is etched to form a porous nitride buried layer; The constituency protects areas where red and green light are expected to be generated. The blue LED structure is formed through epitaxy. Select areas to protect where blue LED structures have already been grown; The stress-releasing effect of porous nitrides is used to improve the incorporation rate of In components in epitaxy, while red / green LED structures are epitaxially grown. The regions where porous nitride buried layers are formed form red LED structures.

7. The method according to claim 5 or 6, characterized in that, Before the aforementioned steps are performed, the following are also included: The constituency protects areas where red and green light are expected to be generated. The N-type nitride buried layer in the region where blue light is to be formed is etched to form a porous nitride buried layer. The porosity of the porous nitride buried layer formed in this step is less than the porosity of the porous nitride buried layers formed by etching the N-type nitride buried layers in the regions where red and green light are to be formed.

8. The method according to claim 5 or 6, characterized in that, The selected area protection adopts the method of forming a protective layer on the surface to wrap the protected area, and the material of the protective layer is SiO2.

9. The method according to claim 1, characterized in that, The nitride is GaN, AlN, AlGaN, InAlN, or InGaN.

10. The method according to claim 1, characterized in that, Porous nitrides were prepared by depositing metal on the surface and then performing anodizing.

11. A multi-color LED monolithic integrated structure, characterized in that, include: The substrate, wherein the surface of the substrate sequentially comprises at least one undoped nitride layer and at least one N-type nitride buried layer; The substrate surface includes an epitaxial structure of a red / green / blue tri-color LED array, and the N-type nitride buried layer below at least one of the red / green / blue tri-color LED array is a porous nitride buried layer.

12. The multi-color LED monolithic integrated structure according to claim 11, characterized in that, The substrate also includes multiple substrate DBR layers, corresponding to the three colors of red, green and blue, respectively.

13. The multi-color LED monolithic integrated structure according to claim 12, characterized in that, The surface of the red / green / blue tri-color LED array epitaxial structure also includes a transparent electrode, and the surface of the transparent electrode includes a surface DBR layer, which resonates with the substrate DBR layer to control the angle of LED emission and make it smaller, thereby increasing the coupling efficiency between the LED and the optical waveguide or optical fiber.

14. The multi-color LED monolithic integrated structure according to claim 11, characterized in that, The N-type nitride buried layers beneath the three structures in the red / green / blue tri-color LED structure array are all porous nitride buried layers.

Images