Plasmonic effect-based micro-led structure and preparation method therefor
Patent Information
- Application Number
- PCT/CN2025/091194
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-27
- Filing Date
- 2025-04-25
- Publication Date
- 2026-10-01
Smart Images
Figure CN2025091194_01102026_PF_FP_ABST
Abstract
Description
micro-LED structure and its fabrication method based on plasmon effect Technical Field
[0001] This invention relates to the field of semiconductor light-emitting technology, and in particular to micro-LED structures based on the plasmon effect and their fabrication methods. Background Technology
[0002] Light-emitting diodes (LEDs) have become the mainstream in the current lighting field due to their significant advantages such as small size, long lifespan, high electro-optical efficiency, good monochromaticity, and environmental friendliness, and are considered to have significant application potential in the future display and lighting fields. Compared with other display technologies, full-color LED displays have advantages such as higher luminous efficiency, higher brightness, higher color saturation, and greater energy efficiency and environmental friendliness. Therefore, developing efficient and smaller micro-LEDs has become a key breakthrough for the refinement and integration of display technology. However, as the size of micro-LED mesa continues to decrease, the proportion of non-radiative recombination in gallium nitride-based LEDs increases, leading to a significant reduction in luminous efficiency. These problems are particularly prominent in red and green micro-LEDs.
[0003] To achieve full-color LED displays, color conversion technology holds promise for solving the problem of low efficiency in red and green light. However, traditional phosphor-based color conversion technology cannot provide sufficient resolution and brightness. This has led to the emergence of nanoscale tunable wavelength quantum dots, offering a development opportunity for the field of micro-LED color conversion. Typically, in quantum dot hybrid devices excited by micro-LEDs, quantum dots are directly spin-coated onto the micro-LED surface, effectively reducing non-radiative recombination losses caused by quantum dot aggregation. However, the color conversion efficiency of quantum dots prepared in this way is not high. This is because, during quantum dot excitation, a P-type semiconductor layer exists between the donor quantum wells and the acceptor quantum dots, resulting in a large coupling distance and low energy transfer efficiency. Furthermore, resonant energy transfer strongly depends on the effective absorption of near-field energy by the acceptor from the energy donor; a significant coupling effect can only be achieved when the distance between the donor and acceptor is maintained at tens of nanometers.
[0004] Traditional plasmon-enhanced structures present the following technical challenges: plasmon enhancement is usually accompanied by light absorption loss in the metal, affecting luminescence efficiency; when quantum dots are directly deposited on the metal surface, nonradiative recombination is significantly enhanced, leading to fluorescence quenching. Summary of the Invention
[0005] In view of this, the purpose of the present invention is to provide a micro-LED structure based on the plasmon effect and a method for its fabrication, so as to at least solve the problem of low luminous efficiency in the prior art.
[0006] The present invention solves the above-mentioned technical problems through the following technical means:
[0007] In a first aspect, embodiments of this application provide a method for fabricating a micro-LED structure based on the plasmon effect, wherein the micro-LED structure is formed on the surface of a p-type GaN layer in a semiconductor, and the fabrication method includes the following steps:
[0008] A SiO2 thin film layer was deposited on the surface of the pretreated P-type GaN layer, and an adhesive was applied to form an imprinting adhesive.
[0009] A nanopore array pattern is formed on an intermediate polymer soft template using thermal embossing technology, and then covered on the surface of the embossing adhesive to form a nanopore array mask.
[0010] Based on the nanopore array mask, the SiO2 thin film layer and the P-type GaN layer were etched by dry etching and wet etching respectively to form a nanopore array;
[0011] After depositing metallic Ag in the nanopores on top of the P-type GaN layer, the material was ground and annealed, and a SiO2 dielectric layer was deposited. Then, using polystyrene spheres as a mask, metallic Ag was deposited on the metallic Ag and SiO2 thin film layers to form a uniformly distributed triangular metallic Ag array.
[0012] A SiO2 layer was deposited on a triangular Ag array, and then a quantum dot solution was spin-coated and cured on the SiO2 layer to form a quantum dot layer.
[0013] In some embodiments, the deposition of a SiO2 thin film on the surface of the pretreated P-type GaN layer and the application of an adhesive to form an imprinting adhesive includes:
[0014] The surface of the P-type GaN layer was cleaned sequentially with acetone, alcohol, and deionized water.
[0015] SiO2 thin film was deposited on the cleaned P-type GaN layer using plasma-enhanced chemical vapor deposition.
[0016] After spin-coating the imprinting adhesive onto the surface of the SiO2 thin film, it is dried in an environment of 90–110°C for 2–5 minutes to form the imprinting adhesive on the SiO2 thin film.
[0017] In some embodiments, the process of forming a nanopore array pattern on an intermediate polymer soft template using thermal embossing technology, and then covering it onto the surface of the embossing adhesive to form a nanopore array mask, includes:
[0018] A nickel metal template with a nanopore array pattern is placed on the stage of a nanoimprinter, and an intermediate polymer soft template is tightly covered on it. The stage is heated to 145-160°C and pressure is applied to transfer the nanopore array pattern on the nickel metal template to the intermediate polymer soft template.
[0019] An intermediate polymer soft template with a nanopore array pattern is coated onto the surface of the imprinting adhesive. The temperature is set to 90–100℃, and the exposure energy is 100–300 mJ / cm². 2 After UV embossing for 0.5–3 minutes, the mask is removed, thus forming a nanopore array mask.
[0020] In some embodiments, the dry etching operation is as follows:
[0021] Corresponding to the nanopores in the nanopore array mask, the SiO2 thin film layer is first etched, and then the P-type GaN layer below the SiO2 thin film layer is etched. The etching time is 30-90s, the etching temperature is 15-30℃, and the etching depth is 150-250nm. After etching, the film is immersed in BOE solution.
[0022] In some embodiments, the wet etching uses a 1.5–2.5 mol / L KOH solution as the etching solution, the etching temperature is 60–80°C, and the etching time is 30–120 s.
[0023] In some embodiments, the deposition of metallic Ag in the nanopores on top of the P-type GaN layer, followed by grinding and annealing, includes:
[0024] Set the evaporation rate to The evaporation angle is 45° to 60°, and metal Ag is deposited into the nanopores using an electron beam evaporation coating machine.
[0025] Excess Ag metal deposited on the surface of the P-type GaN layer is removed by mechanical polishing or ion beam grinding.
[0026] Anneal at 450–600℃ for 0.5–3 minutes.
[0027] In some embodiments, the polystyrene spheres have a diameter of 200–1000 nm.
[0028] In some embodiments, the thickness of the SiO2 layer is 5–40 nm.
[0029] In some embodiments, the concentration of quantum dots in the quantum dot solution is 8–10 mg / mL, and the quantum dots are InP / ZnS or CdSe / CdS quantum dots.
[0030] Secondly, embodiments of this application also provide a micro-LED structure based on the plasmon effect, which is prepared using the preparation method described in the first aspect above.
[0031] The nanopore array fabrication method employed in this invention utilizes nanoimprinting and wet / dry etching techniques, ensuring array order while significantly reducing surface damage caused by etching. The constructed nanopores can shorten the coupling distance between the metal and multiple quantum wells, and can generate a nanocavity effect, effectively improving luminescence efficiency, color conversion efficiency, and overall photoelectric conversion efficiency. The dual-coupled plasmon nanoarray structure proposed in this invention is constructed using electron beam evaporation coating and polystyrene spheres as templates to prepare a bilayer Ag nanoparticle array. This allows for independent, non-interfering luminescence coupling with both multiple quantum wells and quantum dots, and can be controlled according to the corresponding wavelength. The process is simple, convenient, and easy to characterize. The spin-coating method used to prepare the quantum dot layer offers controllable processing and good uniformity, which helps reduce non-radiative recombination caused by quantum dot aggregation, ultimately improving light extraction efficiency. The spin-coated film exhibits high uniformity, effectively reducing non-radiative recombination caused by quantum dot aggregation and improving photon conversion efficiency. Attached Figure Description
[0032] Figure 1 is a process flow diagram of a method for fabricating a micro-LED structure based on the plasmon effect according to an embodiment of the present invention.
[0033] Figure 2 is a schematic diagram of the micro-LED structure based on the plasmon effect.
[0034] Figure 3 is a scanning electron microscope image of the nanopore array structure with a period of 450 nm, a pore diameter of 200 nm, and a pore depth of 200 nm formed by etching on the top of the P-type GaN layer in Example 1.
[0035] Figure 4 is a scanning electron microscope image of the second plasmonic Ag nanoparticle layer of the micro-LED structure in Example 1.
[0036] Figure 5 shows the photoluminescence spectra of the micro-LED structure in Example 1 and the control sample.
[0037] Figure 6 shows the quantum dot fluorescence decay curves of the micro-LED structure and the control sample in Example 1. Detailed Implementation
[0038] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0039] The terms "first" and "second," etc., used in the specification and claims herein are used to distinguish different objects, not to describe a specific order of objects. In the description of embodiments of this application, unless otherwise stated, "a plurality of" means two or more, for example, "a plurality of processing units" means two or more processing units, "a plurality of elements" means two or more elements, etc.
[0040] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.
[0041] The micro-LED structure based on the plasmon effect of this application is formed on the surface of a p-type GaN layer in a semiconductor. Referring to Figures 1 and 2, the fabrication method of the micro-LED structure based on the plasmon effect of this application includes the following steps:
[0042] Step S1: Deposit a SiO2 thin film on the surface of the pretreated P-type GaN layer and apply adhesive to form an imprinting adhesive.
[0043] In this step, the surface of the P-type GaN layer is cleaned sequentially with acetone, alcohol, and deionized water; a SiO2 thin film layer is deposited on the cleaned P-type GaN layer using plasma-enhanced chemical vapor deposition; after spin-coating the imprinting adhesive onto the surface of the SiO2 thin film layer, it is dried in an environment of 90–110°C for 2–5 minutes to form the imprinting adhesive on the SiO2 thin film layer.
[0044] Step S2: A nanopore array pattern is formed on the intermediate polymer soft template using thermal embossing technology, and then covered on the surface of the embossing adhesive to form a nanopore array mask.
[0045] In this step, a nickel metal template with a nanopore array pattern is placed on the stage of a nanoimprint emulation machine, and an intermediate polymer soft template is tightly covered on top. The stage is heated to 145–160°C, and pressure is applied to transfer the nanopore array pattern from the nickel metal template to the intermediate polymer soft template. The intermediate polymer soft template with the nanopore array pattern is then placed on the surface of the imprinting adhesive, with the temperature set to 90–100°C and the exposure energy to 100–300 mJ / cm². 2 After UV embossing for 0.5–3 minutes, the mask is removed, thus forming a nanopore array mask.
[0046] Step S3: Based on the nanopore array mask, the SiO2 thin film layer and the P-type GaN layer are etched by dry etching and wet etching respectively to form a nanopore array.
[0047] In this step, the dry etching operation is as follows: corresponding to the nanopores in the nanopore array mask, the SiO2 thin film layer is etched first, followed by etching of the P-type GaN layer below the SiO2 thin film layer. The etching time is 30–90 s, the etching temperature is 15–30 °C, and the etching depth is 150–250 nm. After etching, the layer is immersed in BOE solution. For wet etching, a 1.5–2.5 mol / L KOH solution is used as the etching solution, the etching temperature is 60–80 °C, and the etching time is 30–120 s.
[0048] Dry etching was used to etch the P-type GaN layer to initially form a nanopore structure. Wet etching was then performed to optimize the sidewall smoothness of the nanopores and remove etching residues. The size and depth of the nanopores were controlled by adjusting the etching time and gas flow rate parameters to adapt to the quantum dot luminescence enhancement at different wavelengths.
[0049] Step S4: After depositing metallic Ag in the nanopores on top of the P-type GaN layer, the material is ground and annealed, and a SiO2 dielectric layer is deposited. Then, using polystyrene spheres as a mask, metallic Ag is deposited on the metallic Ag and SiO2 thin film layers to form a uniformly distributed triangular metallic Ag array.
[0050] In this step, the evaporation rate is set to... An evaporation angle of 45°–60° was used to deposit metallic Ag into the nanopores using an electron beam evaporation deposition machine, ensuring uniform Ag filling to the bottom of the nanopores. Excess metallic Ag deposited on the surface of the p-type GaN layer was removed by mechanical polishing or ion beam grinding to further optimize surface finish. Annealing at 450–600℃ for 0.5–3 min improved the grain orientation of the Ag nanostructure and enhanced plasmon resonance characteristics. The diameter of the polystyrene spheres ranged from 200–1000 nm; by controlling the size of the polystyrene spheres, plasmon enhancement of quantum dots at different wavelengths could be achieved.
[0051] Step S5: Continue to deposit a SiO2 layer on the triangular Ag array, and then spin-coat and cure the SiO2 layer with a quantum dot solution to form a quantum dot layer.
[0052] In this step, the thickness of the first SiO2 dielectric layer is 5–15 nm, and the second layer is 5–40 nm, ensuring the uniformity of the SiO2 layer to prevent non-radiative recombination loss caused by direct contact between quantum dots and Ag. The quantum dot concentration in the quantum dot solution is 8–10 mg / mL, and the quantum dots are InP / ZnS or CdSe / CdS quantum dots, dissolved in n-hexane, toluene, or n-octane, ensuring uniform dispersion of the quantum dots. After spin-coating the quantum dot solution, a curing treatment is required. The curing treatment is carried out in an environment of 50–70℃ for 5 minutes to fix the quantum dot layer, reduce surface defects, and use plasma treatment to improve the bonding force between the quantum dot layer and the SiO2 interface, optimizing luminescence stability.
[0053] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.
[0054] The P-type GaN layer in the following embodiments is formed as follows:
[0055] (1) An AlN buffer layer with a thickness of about 15 to 45 nm was grown on a patterned sapphire substrate using metal-organic vapor phase epitaxy.
[0056] (2) An intrinsic GaN layer (2 μm thick), an N-type GaN layer (1 μm thick), an InGaN / GaN multi-quantum-well light-emitting active region (light emission wavelength of about 475 nm) and a P-type GaN layer (500 nm thick) are sequentially grown on the above AlN buffer layer.
[0057] Example 1
[0058] Referring to Figures 1-6, this embodiment provides a method for fabricating a micro-LED structure based on the plasmon effect, which is described in detail below:
[0059] (1) Cleaning and Deposition of Mask Layer: First, the surface of the P-type GaN layer is cleaned with acetone, alcohol and deionized water in sequence. The surface cleanliness will directly affect whether the pattern obtained by imprinting has large-area order. Then, a SiO2 thin film layer is deposited by plasma-enhanced chemical vapor deposition (PECVD).
[0060] (2) Coating: Spin coat a layer of TU2-170 / TU2-60 imprinting adhesive onto the surface of the SiO2 thin film layer in step (1) above. The spin coating conditions are 2000 rpm and the spin coating time is 40 s. Then place it on a hot plate at 90 ℃ and dry for 2 min to form imprinting adhesive.
[0061] (3) Hot imprinting of the intermediate polymer soft template: First, a nickel metal template with a nanopore array pattern is placed on the stage of the nanoimprinting machine, and an intermediate polymer soft template is tightly covered on it; then, the stage is heated to 150℃ (145~160℃), and by applying a certain pressure, the nanopore array pattern on the nickel metal template is transferred to the intermediate polymer soft template, and then cooled for demolding. The nickel metal template used has a nanopore array with a period of 450nm, a pore diameter of 200nm, and a pore depth of 200nm.
[0062] (4) Form a nanopore array mask template by covering the patterned intermediate polymer soft template obtained in step (3) onto the surface of the imprinting adhesive, and expose it at 90°C and an exposure energy of 200 mJ / cm. 2 Under the given conditions, after UV lamp imprinting and curing for 2 minutes, the film was demolded, thus forming a series of imprinted adhesive nanopore array mask templates on the surface of the SiO2 thin film layer.
[0063] (5) Dry etching: First, using imprinting adhesive as a mask, the surface SiO2 layer is etched by inductively coupled plasma etching (ICP). Then, the gas source is switched to continue etching the P-type GaN layer below the SiO2 layer. The etching time is set to 30s, the etching depth is set to 150nm, and the temperature is set to 15℃. Then, the sample is immersed in BOE solution (HF:NH4F=1:6) to remove the residual SiO2 on the surface.
[0064] (6) Wet chemical etching: In order to repair the damage and contamination of the inner wall of the nanopores caused by dry etching as much as possible, and to further deepen the etching depth of the nanopores, the sample was subjected to wet chemical etching with 2 mol / L KOH solution. The solution temperature was set at 60℃ and the etching time was set at 30s. Thus, the Ni metal nanotemplate pattern was successfully transferred to the P-type GaN layer, as shown in Figure 3.
[0065] (7) Preparation of the first plasmonic Ag nanoparticle layer, with the evaporation rate set as follows: With an evaporation angle of 50°, metal Ag was deposited in the nanopores on the top of the P-type GaN layer using an electron beam evaporation coating machine. The residual Ag metal on the surface was removed by grinding with 10,000-grit sandpaper. Then, the layer was rapidly thermally annealed at 500°C for 1 min under a nitrogen atmosphere, and a SiO2 dielectric layer was deposited.
[0066] (8) Preparation of the second plasmonic Ag nanoparticle layer: Using polystyrene spheres with a diameter of 710 nm, a single layer of closely packed polystyrene sphere mask layer is prepared on top of the P-type GaN layer after the above process. Then, metal Ag is deposited using an electron beam evaporation coating machine, and the polystyrene sphere template and residual Ag metal are removed by soaking in tetrahydrofuran solution to form a triangular metal Ag array, as shown in Figure 4.
[0067] (9) Quantum dot layer preparation: After the above process is completed, a 5 nm thick SiO2 layer is deposited by PECVD as an isolation layer between the quantum dots and the metal Ag. Then, the quantum dot layer is prepared by spin coating technology. The quantum dots used are InP / ZnS quantum dots dissolved in n-hexane with a concentration of 8 mg / mL and an emission wavelength of about 650 nm. The spin coating speed is set to 1000 rpm and the spin coating time is 50 s. After spin coating, the layer is kept in an environment of 50-70℃ for 5 min to cure and obtain the quantum dot layer.
[0068] Figures 5 and 6 show the photoluminescence spectra and fluorescence decay curves of the structure described in Example 1 and the comparative sample. QW-QD is the comparative sample with quantum dots directly spin-coated on the surface of an LED epitaxial wafer, and QW-QD-SP is the sample with the structure described in Example 1. As can be seen from Figure 5, the sample with the structure described in Example 1 has a strong emission peak at 648 nm, which is nearly 5.5 times higher than the emission intensity of the comparative sample, indicating a significant improvement in the color conversion of the quantum dots. As can be seen from Figure 6, the fluorescence decay rate of the sample with the structure described in Example 1 changes faster, indicating that the radiative recombination rate is increased, resulting in higher color conversion efficiency of the quantum dots.
[0069] Example 2
[0070] This embodiment provides a method for fabricating a micro-LED structure based on the plasmon effect, which is described in detail below:
[0071] (1) Cleaning and Deposition of Mask Layer: First, the surface of the P-type GaN layer is cleaned with acetone, alcohol and deionized water in sequence. The surface cleanliness will directly affect whether the pattern obtained by imprinting has large-area order. Then, a SiO2 thin film layer is deposited by plasma-enhanced chemical vapor deposition (PECVD).
[0072] (2) Coating: Spin coat a layer of TU2-170 / TU2-60 imprinting adhesive onto the surface of the SiO2 thin film layer in step (1) above. The spin coating conditions are 2000 rpm and the spin coating time is 40 s. Then place it on a hot plate at 90 ℃ and dry for 2 min to form imprinting adhesive.
[0073] (3) Hot imprinting of the intermediate polymer soft template: First, a nickel metal template with a nanopore array pattern is placed on the stage of the nanoimprinting machine, and an intermediate polymer soft template is tightly covered on it; then, the stage is heated to 160°C, and by applying a certain pressure, the nanopore array pattern on the nickel metal template is transferred to the intermediate polymer soft template, and then the template is cooled for demolding. The nickel metal template used has a nanopore array with a period of 400 nm, a pore diameter of 200 nm, and a pore depth of 200 nm.
[0074] (4) Form a nanopore array mask by covering the patterned intermediate polymer soft template obtained in step (3) onto the surface of the imprinting adhesive and exposing it at 100°C with an exposure energy of 300 mJ / cm. 2 Under the given conditions, after UV lamp imprinting and curing for 2 minutes, the film was demolded, thus forming a series of imprinted adhesive nanopore array mask templates on the surface of the SiO2 thin film layer.
[0075] (5) Dry etching: First, using imprinting adhesive as a mask, the surface SiO2 layer is etched by inductively coupled plasma etching (ICP). Then, the gas source is switched to continue etching the P-type GaN layer below the SiO2 layer. The etching time is set to 60s, the etching depth is set to 200nm, and the temperature is set to 25℃. Then, the sample is immersed in BOE solution (HF:NH4F=1:6) to remove the residual SiO2 on the surface.
[0076] (6) Wet chemical etching: In order to repair the damage and contamination of the inner wall of the nanopores caused by dry etching as much as possible, and to further deepen the etching depth of the nanopores, the sample was subjected to wet chemical etching treatment with 1.5 mol / L KOH solution. The solution temperature was set at 70℃ and the etching time was set at 90s. Thus, the Ni metal nanotemplate pattern was successfully transferred to the P-type GaN layer.
[0077] (7) Preparation of the first plasmonic Ag nanoparticle layer, with the evaporation rate set as follows: (The evaporation angle is 45°. Using an electron beam evaporation coating machine, metallic Ag is deposited in the nanopores on the top of the P-type GaN layer. The residual Ag metal on the surface is removed by polishing with 10,000-grit sandpaper. Then, the surface is rapidly annealed at 450°C for 0.5 min in a nitrogen atmosphere, and a SiO2 dielectric layer is deposited.)
[0078] (8) Preparation of the second plasmonic Ag nanoparticle layer: Using polystyrene spheres with a diameter of 500 nm, a single layer of tightly packed polystyrene sphere mask layer is prepared on top of the P-type GaN layer after the above process. Then, metal Ag is deposited using an electron beam evaporation coating machine, and the polystyrene sphere template and residual Ag metal are removed by soaking in tetrahydrofuran solution to form a triangular metal Ag array.
[0079] (9) Quantum dot layer preparation: After the above process, a 12nm thick SiO2 layer is deposited using PECVD as an isolation layer between the quantum dots and the metallic Ag. The quantum dots used are InP / ZnS quantum dots dissolved in n-hexane at a concentration of 9mg / mL. A double-layer spin-coating technique is used to prepare the quantum dot layer to improve the uniformity and stability of the quantum dots, as detailed below:
[0080] First layer spin coating: InP / ZnS quantum dots (n-hexane solution, concentration 9 mg / mL), spin coating speed 1200 rpm, spin coating time 40 s, low temperature curing (80℃, 3 min).
[0081] The second layer is spin-coated with the same concentration of quantum dot solution at a spin speed of 1000 rpm for 40 seconds. Finally, vacuum annealing (100℃, 5 min) is performed to improve the density of the quantum dots and cure them to obtain the quantum dot layer.
[0082] Performance comparison and results:
[0083] Photoluminescence spectroscopy analysis: The emission peak intensity of the quantum dots at 650 nm was increased by 15% compared with Example 1; the color conversion efficiency (CCE) of the quantum dots was increased by about 12%, from 75% in Example 1 to 87% in this example; the fluorescence decay time of the quantum dots was shortened by about 8%, indicating that the coupling effect between the quantum dots and plasmons was enhanced and the nonradiative recombination was reduced.
[0084] Micro-LED Application Optimization: Due to the improved uniformity of the quantum dot layer, the color consistency of micro-LED pixels is better. Optical simulation results show that the structure of Example 2 uses a two-layer spin coating technique to prepare the quantum dot layer. First, the density of the quantum dot layer is improved by using a higher rotation speed (1200 rpm) and low temperature curing (80°C, 3 min). The subsequent second spin coating further distributes the quantum dots evenly. The optimization of the second Ag nanoparticle array can improve the light extraction efficiency by about 18% and reduce the power loss by about 10% compared with Example 1.
[0085] Example 3
[0086] In this embodiment, metal-organic vapor phase epitaxy (MOCVD) is used to grow a 30 nm thick AlN buffer layer on a patterned sapphire substrate. An intrinsic GaN layer, an N-type GaN layer, a multi-quantum-well light-emitting active region (emission wavelength 470 nm), and a P-type GaN layer are then grown sequentially.
[0087] This embodiment provides a method for fabricating a micro-LED structure based on the plasmon effect, which is described in detail below:
[0088] (1) Cleaning and Deposition of Mask Layer: First, the surface of the P-type GaN layer is cleaned with acetone, alcohol and deionized water in sequence. The surface cleanliness will directly affect whether the pattern obtained by imprinting has large-area order. Then, a SiO2 thin film layer with a thickness of 50nm is deposited by plasma-enhanced chemical vapor deposition (PECVD).
[0089] (2) Coating: Spin coat a layer of TU2-170 / TU2-60 imprinting adhesive onto the surface of the SiO2 thin film layer in step (1) above. The spin coating conditions are 2000 rpm and the spin coating time is 40 s. Then place it on a hot plate at 110℃ and dry for 3 min to form imprinting adhesive.
[0090] (3) Hot imprinting of intermediate polymer soft template: First, a nickel metal template with a nanopore array pattern is placed on the stage of a nanoimprinting machine, and an intermediate polymer soft template is tightly covered on it; then, the stage is heated to 145°C, and by applying a certain pressure, the nanopore array pattern on the nickel metal template is transferred to the intermediate polymer soft template, and then the template is cooled for demolding. The nickel metal template used has a nanopore array with a period of 400 nm, a pore diameter of 180 nm, and a pore depth of 180 nm.
[0091] (4) Form a nanopore array mask by covering the patterned intermediate polymer soft template obtained in step (3) onto the surface of the imprinting adhesive and exposing it at 100°C with an exposure energy of 300 mJ / cm. 2 Under the given conditions, after UV lamp imprinting and curing for 3 minutes, the film was demolded, thus forming a series of imprinted adhesive nanopore array mask templates on the surface of the SiO2 thin film layer.
[0092] (5) Dry etching: First, using imprinting adhesive as a mask, the surface SiO2 layer is etched by inductively coupled plasma etching (ICP). Then, the gas source is switched to continue etching the P-type GaN layer below the SiO2 layer. The etching time is set to 90s, the etching depth is set to 250nm, and the temperature is set to 30℃. Then, the sample is immersed in BOE solution (HF:NH4F=1:6) to remove the residual SiO2 on the surface.
[0093] (6) Wet chemical etching: In order to repair the damage and contamination of the inner wall of the nanopores caused by dry etching as much as possible, and to further deepen the etching depth of the nanopores, the sample was subjected to wet chemical etching with 2 mol / L KOH solution. The solution temperature was set to 80℃ and the etching time was set to 120s. Thus, the Ni metal nanotemplate pattern was successfully transferred to the P-type GaN layer.
[0094] (7) Preparation of plasmonic Ag nanoparticle layers, with the evaporation rate set as follows: The evaporation angle is 45°. Using an electron beam evaporation coating machine, a single layer of metallic Ag is deposited on top of the P-type GaN layer. The residual Ag metal on the surface is removed by polishing with 10,000-grit sandpaper. Then, it is rapidly annealed at 450°C for 1 min in a nitrogen atmosphere.
[0095] (8) Quantum dot layer preparation: After the above process is completed, a SiO2 layer with a thickness of 40 nm is deposited by PECVD as an isolation layer between quantum dots and metal Ag. Then, a quantum dot layer is prepared by spin coating technology. The quantum dots used are CdSe / ZnS quantum dots dissolved in n-hexane with a concentration of 10 mg / mL. The spin coating speed is set to 1200 rpm and the spin coating time is 50 s. After spin coating, the layer is placed in an environment of 50-70℃ for 5 min to cure and obtain the quantum dot layer.
[0096] In this embodiment, only a single-layer plasmon structure was used. Compared with Example 1, the quantum dot color conversion efficiency decreased by approximately 16.3%, indicating that the bilayer plasmon structure can more effectively enhance optical field coupling and improve fluorescence efficiency. The increase in quantum dot fluorescence intensity decreased (1.8 times → 1.3 times), indicating that the bilayer plasmon structure can further optimize light extraction efficiency. Due to the absence of a bilayer nanostructure, the quantum dot fluorescence lifetime was extended (4.1 ns → 3.2 ns → 4.1 ns), indicating a weaker plasmonic coupling enhancement effect and lower energy transfer efficiency.
[0097] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.
Claims
1. A method for fabricating a micro-LED structure based on the plasmon effect, characterized in that, The micro-LED structure is formed on the surface of a p-type GaN layer in a semiconductor, and the fabrication method includes the following steps: A SiO2 thin film layer was deposited on the surface of the pretreated P-type GaN layer, and an adhesive was applied to form an imprinting adhesive. A nanopore array pattern is formed on an intermediate polymer soft template using thermal embossing technology, and then covered on the surface of the embossing adhesive to form a nanopore array mask. Based on the nanopore array mask, the SiO2 thin film layer and the P-type GaN layer were etched by dry etching and wet etching respectively to form a nanopore array; After depositing metallic Ag in the nanopores on top of the P-type GaN layer, the material is ground and annealed, and a first SiO2 dielectric layer is deposited. Then, using polystyrene spheres as a mask, metallic Ag is deposited on the metallic Ag and SiO2 thin film layers to form a uniformly distributed triangular metallic Ag array. A second SiO2 layer was deposited on a triangular Ag array, and then a quantum dot solution was spin-coated and cured on the SiO2 layer to form a quantum dot layer.
2. The method for fabricating a micro-LED structure based on the plasmon effect according to claim 1, characterized in that, The process of depositing a SiO2 thin film on the surface of a pretreated P-type GaN layer and applying an adhesive to form an imprinting adhesive includes: The surface of the P-type GaN layer was cleaned sequentially with acetone, alcohol, and deionized water. SiO2 thin film was deposited on the cleaned P-type GaN layer using plasma-enhanced chemical vapor deposition. After spin-coating the imprinting adhesive onto the surface of the SiO2 thin film, it is dried in an environment of 90–110°C for 2–5 minutes to form the imprinting adhesive on the SiO2 thin film.
3. The method for fabricating a micro-LED structure based on the plasmon effect according to claim 1, characterized in that, The process involves forming a nanopore array pattern on an intermediate polymer soft template using thermal embossing technology, and then covering the surface of the embossing adhesive to form a nanopore array mask, including: A nickel metal template with a nanopore array pattern is placed on the stage of a nanoimprinter, and an intermediate polymer soft template is tightly covered on it. The stage is heated to 145-160°C and pressure is applied to transfer the nanopore array pattern on the nickel metal template to the intermediate polymer soft template. An intermediate polymer soft template with a nanopore array pattern is coated onto the surface of the imprinting adhesive. The temperature is set to 90–100℃, and the exposure energy is 100–300 mJ / cm². 2 After UV embossing for 0.5–3 minutes, the mask is removed, thus forming a nanopore array mask.
4. The method for fabricating a micro-LED structure based on the plasmon effect according to claim 1, characterized in that, The dry etching operation is as follows: Corresponding to the nanopores in the nanopore array mask, the SiO2 thin film layer is first etched, and then the P-type GaN layer below the SiO2 thin film layer is etched. The etching time is 30-90s, the etching temperature is 15-30℃, and the etching depth is 150-250nm. After etching, the residual SiO2 is removed by immersion in BOE solution.
5. The method for fabricating a micro-LED structure based on the plasmon effect according to claim 4, characterized in that, The wet etching process uses a 1.5–2.5 mol / L KOH solution as the etching solution, with an etching temperature of 60–80°C and an etching time of 30–120 s.
6. The method for fabricating a micro-LED structure based on the plasmon effect according to claim 1, characterized in that, The deposition of metallic Ag in the nanopores at the top of the P-type GaN layer, followed by grinding and annealing, includes: Set the evaporation rate to The evaporation angle is 45° to 60°, and metal Ag is deposited into the nanopores using an electron beam evaporation coating machine. Excess Ag metal deposited on the surface of the P-type GaN layer is removed by mechanical polishing or ion beam grinding. Anneal at 450–600℃ for 0.5–3 minutes.
7. The method for fabricating a micro-LED structure based on the plasmon effect according to claim 1, characterized in that, The polystyrene spheres have a diameter of 200–1000 nm.
8. The method for fabricating a micro-LED structure based on the plasmon effect according to claim 1, characterized in that, The thickness of the first SiO2 dielectric layer is 5–15 nm, and the thickness of the second layer is 5–40 nm.
9. The method for fabricating a micro-LED structure based on the plasmon effect according to claim 1, characterized in that, The concentration of quantum dots in the quantum dot solution is 8–10 mg / mL, and the quantum dots are InP / ZnS or CdSe / CdS quantum dots.
10. A micro-LED structure based on the plasmon effect, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.