Micro-LED structure based on plasmon effect and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor light emitting, in particular to a micro-LED structure based on the plasmon effect and a preparation method thereof, and the preparation method comprises the steps: depositing a SiO2 thin film layer on the surface of a pretreated P-type GaN layer, and forming imprinting glue; forming a nanopore array mask plate on the surface of the imprinting glue; etching the SiO2 thin film layer and the P-type GaN layer by adopting dry etching and wet etching in sequence to form a nanopore array; after metal Ag is deposited in nanopores in the top of the P-type GaN layer, grinding and annealing treatment are carried out, after a SiO2 dielectric layer is deposited, metal Ag continues to be deposited on the metal Ag and the SiO2 thin film layer, and a uniformly-distributed triangular-like metal Ag array is formed; and continuously depositing a SiO2 layer on the triangle-like metal Ag array, and then carrying out spin coating and curing on the SiO2 layer by adopting a quantum dot solution to form a quantum dot layer. According to the invention, the technology of preparing the nanopore array by adopting nanoimprint and dry-wet etching is adopted, so that the orderliness of the array is ensured, the surface damage caused by etching is reduced, the luminous efficiency is improved, the color conversion efficiency is improved, and the overall photoelectric conversion efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor light-emitting technologies, and particularly to a micro-LED structure based on the plasmon effect and a preparation method thereof. Background Art

[0002] Semiconductor light-emitting diodes (LEDs) have become the mainstream in the current lighting field due to their remarkable advantages such as small size, long lifespan, high electro-optical efficiency, good monochromaticity, and environmental friendliness, and are considered to have important 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 more energy-saving and environmental protection. Therefore, the development of efficient and smaller-sized micro-LEDs has also become a key breakthrough point for the refinement and integration of display technologies. However, with the continuous reduction of the current micro-LED mesa size, the proportion of non-radiative recombination in gallium nitride-based LEDs increases, resulting in 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 technologies are expected to solve the problem of low efficiency of red and green light. However, due to the fact that traditional fluorescent powder color conversion technologies cannot provide sufficient resolution and brightness, the emergence of nano-scale tunable emission wavelength quantum dots provides a development opportunity for the micro-LED color conversion field. Generally, in a quantum dot hybrid device excited by a micro-LED, the quantum dots are directly spin-coated on the surface of the micro-LED, effectively reducing the non-radiative recombination loss caused by quantum dot aggregation. However, the color conversion efficiency of the quantum dots prepared by this method is not high because, during the quantum dot excitation process, there is a P-type semiconductor layer between the donor multiple quantum wells and the acceptor quantum dots, resulting in a large coupling distance between the quantum wells and the quantum dots and a low energy transfer efficiency. And resonant energy transfer strongly depends on the effective absorption of the acceptor to the near-field energy of the energy donor. When the distance between the donor and the acceptor is maintained at dozens of nanometers, a significant coupling effect can be produced.

[0004] The following technical difficulties exist in traditional plasmon-enhanced structures: Plasmon enhancement is usually accompanied by optical absorption loss of the metal, affecting the luminous efficiency; when the quantum dots are directly deposited on the metal surface, non-radiative recombination will be significantly enhanced, resulting in 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 preparation method thereof, so as to at least solve the problem of relatively low luminous efficiency existing in the prior art.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] In a first aspect, an embodiment of the present application provides a preparation method of a micro-LED structure based on the plasmonic effect. The micro-LED structure is formed on the surface of the P-type GaN layer of a semiconductor. The preparation method includes the following steps:

[0008] Deposit a SiO2 thin film layer on the surface of the pretreated P-type GaN layer and apply glue to form an imprinting glue.

[0009] Use a hot embossing technique to form a nanohole array pattern on an intermediate polymer soft template, cover it on the surface of the imprinting glue to form a nanohole array mask template.

[0010] Based on the nanohole array mask template, dry etching and wet etching are successively used to etch the SiO2 thin film layer and the P-type GaN layer to form a nanohole array.

[0011] After depositing metallic Ag in the top nanoholes of the P-type GaN layer, perform grinding and annealing treatment, deposit a SiO2 dielectric layer, and then use polystyrene spheres as a mask to continue depositing metallic Ag on the metallic Ag and the SiO2 thin film layer to form a uniformly distributed triangular-like metallic Ag array.

[0012] Continue to deposit a SiO2 layer on the triangular-like metallic Ag array, and then use a quantum dot solution to spin-coat and cure on the SiO2 layer to form a quantum dot layer.

[0013] In some embodiments, depositing a SiO2 thin film layer on the surface of the pretreated P-type GaN layer and applying glue to form an imprinting glue includes:

[0014] Clean the surface of the P-type GaN layer successively with acetone, alcohol, and deionized water.

[0015] Deposit a SiO2 thin film layer on the cleaned P-type GaN layer by plasma-enhanced chemical vapor deposition.

[0016] After spin-coating the imprinting glue on the surface of the SiO2 thin film layer, place it in an environment of 90 - 110 °C and dry for 2 - 5 min, thereby forming the imprinting glue on the SiO2 thin film layer.

[0017] In some embodiments, using a hot embossing technique to form a nanohole array pattern on an intermediate polymer soft template, cover it on the surface of the imprinting glue to form a nanohole array mask template includes:

[0018] Place a nickel metal template with a nanohole array pattern on the nanoimprinting machine stage, closely cover the intermediate polymer soft template on it, heat the stage to 145 - 160 °C, and apply pressure to transfer the nanohole array pattern on the nickel metal template to the intermediate polymer soft template.

[0019] Cover the surface of the imprinting resist with an intermediate polymer soft template having a nanohole array pattern, set the temperature to 90 - 100 °C, and the exposure energy to 100 - 300 mJ / cm 2 , perform ultraviolet nanoimprint lithography for 0.5 - 3 min, and then demold to form a nanohole array mask template.

[0020] In some embodiments, the dry etching operation is as follows:

[0021] Corresponding to the nanoholes in the nanohole array mask template, first etch the SiO2 thin film layer, and then continue to etch 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 the etching is completed, soak it 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, depositing metal Ag in the nanoholes at the top of the P-type GaN layer and performing polishing and annealing treatment includes:

[0024] Set the evaporation rate to The evaporation angle is 45° - 60°, and use an electron beam evaporation coating machine to deposit metal Ag into the nanoholes;

[0025] Use mechanical polishing or ion beam grinding to remove the excessive metal Ag deposited on the surface of the P-type GaN layer;

[0026] Anneal at a temperature of 450 - 600 °C for 0.5 - 3 min.

[0027] In some embodiments, the diameter of the polystyrene spheres is 200 - 1000 nm.

[0028] In some embodiments, the thickness of the SiO2 layer is 5 - 40 nm.

[0029] In some embodiments, 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.

[0030] In a second aspect, the embodiments of the present application further provide a micro-LED structure based on the plasmonic effect, which is prepared by using the preparation method described in the first aspect above.

[0031] In the preparation method of the present invention, the nanoimprinting and dry-wet etching techniques for preparing nanohole arrays are adopted, which not only ensure the orderliness of the arrays but also greatly reduce the surface damage caused by etching. The constructed nanoholes can be used to shorten the coupling distance between metal and multiple quantum wells, and can generate a nano-cavity effect, effectively improving the light-emitting efficiency, enhancing the color conversion efficiency, and promoting the overall optoelectronic conversion efficiency. The dual-coupling plasmonic nanoarray structure proposed by the present invention is fabricated by preparing a double-layer Ag nanoparticle array based on electron beam evaporation coating and polystyrene spheres as templates, which can achieve non-interfering light-emitting coupling with multiple quantum wells and quantum dots respectively, and can be regulated according to the corresponding wavelengths. The process is simple, the operation is convenient, and it is easy to characterize. The quantum dot layer is prepared by spin coating, with controllable process and good uniformity, which is beneficial to reducing the non-radiative recombination caused by quantum dot aggregation, and finally improving the light extraction efficiency. The spin-coated film has high uniformity, effectively reducing the non-radiative recombination caused by quantum dot aggregation and improving the photon conversion efficiency. Description of the Drawings

[0032] Figure 1 FIG. is a process flow chart of a preparation method of a micro-LED structure based on the plasmonic effect provided by an embodiment of the present invention.

[0033] Figure 2 FIG. is a schematic structural diagram of a micro-LED structure based on the plasmonic effect.

[0034] Figure 3 FIG. is a scanning electron microscope image of a nanohole array structure with a period of 450 nm, a pore diameter of 200 nm, and a pore depth of 200 nm etched on the top of the P-type GaN layer in Example 1.

[0035] Figure 4 FIG. is a scanning electron microscope image of the second plasmonic Ag nanoparticle layer of the micro-LED structure in Example 1.

[0036] Figure 5 FIG. is a photoluminescence spectrum of the micro-LED structure and the control sample in Example 1.

[0037] Figure 6 FIG. is a quantum dot fluorescence decay curve of the micro-LED structure and the control sample in Example 1. Detailed Embodiments

[0038] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Apparently, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0039] The terms "first" and "second" in the description and claims of this document are used to distinguish different objects, rather than to describe a specific order of objects. In the description of the embodiments of this application, unless otherwise stated, the meaning of "a plurality of" refers to two or more. For example, a plurality of processing units refers to two or more processing units, and a plurality of elements refers to two or more elements.

[0040] In the embodiments of this application, words such as "exemplary" or "for example" are used to represent examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0041] The micro-LED structure based on the plasmonic effect of this application is formed on the surface of the P-type GaN layer of the semiconductor. Please refer to Figure 1 and Figure 2 , the preparation method of the micro-LED structure based on the plasmonic effect of this application includes the following steps:

[0042] Step S1: Deposit a SiO2 thin film layer on the surface of the pretreated P-type GaN layer and apply glue to form an imprinting glue.

[0043] In this step, the surface of the P-type GaN layer is cleaned successively with acetone, alcohol, and deionized water; a SiO2 thin film layer is deposited on the cleaned P-type GaN layer by plasma-enhanced chemical vapor deposition; after spin-coating the imprinting glue on the surface of the SiO2 thin film layer, it is placed in an environment of 90-110°C and dried for 2-5 minutes, that is, an imprinting glue is formed on the SiO2 thin film layer.

[0044] Step S2: Use a hot embossing technique to form a nanohole array pattern on an intermediate polymer soft template, and cover it on the surface of the imprinting glue to form a nanohole array mask template.

[0045] In this step, place the nickel metal template with a nanohole array pattern on the nanoimprinting machine stage, tightly cover an intermediate polymer soft template thereon, heat the stage to 145 - 160 °C, and apply pressure to transfer the nanohole array pattern on the nickel metal template to the intermediate polymer soft template; cover the intermediate polymer soft template with the nanohole array pattern on the surface of the imprinting resist, set the temperature to 90 - 100 °C, the exposure energy to 100 - 300 mJ / cm 2 , perform ultraviolet light imprinting treatment for 0.5 - 3 min, and demold to form a nanohole array mask template.

[0046] Step S3: Based on the nanohole array mask template, use dry etching and wet etching successively to etch the SiO2 thin film layer and the P-type GaN layer to form a nanohole array.

[0047] In this step, the dry etching operation is as follows: corresponding to the nanoholes in the nanohole array mask template, first etch the SiO2 thin film layer, and then continue to etch 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 is completed, soak it in BOE solution. The wet etching uses a 1.5 - 2.5 mol / L KOH solution as the etching solution for wet etching, the etching temperature is 60 - 80 °C, and the etching time is 30 - 120 s.

[0048] Use dry etching to etch the P-type GaN layer to initially form a nanohole structure, and then perform wet etching to optimize the sidewall smoothness of the nanoholes and remove etching residues. Control the nanohole size and depth by adjusting the etching time and gas flow parameters to adapt to the light emission enhancement of quantum dots with different wavelengths.

[0049] Step S4: After depositing metal Ag in the nanoholes at the top of the P-type GaN layer, perform grinding and annealing treatment, and deposit a layer of SiO2 dielectric layer. Then use polystyrene spheres as a mask and continue to deposit metal Ag on the metal Ag and the SiO2 thin film layer to form a uniformly distributed triangular-like metal Ag array.

[0050] In this step, set the evaporation rate to The evaporation angle is 45° - 60°. Use an electron beam evaporation coating machine to deposit metal Ag into the nanoholes to ensure that the metal Ag is uniformly filled to the bottom of the nanoholes; use mechanical polishing or ion beam grinding to remove the excessive metal Ag deposited on the surface of the P-type GaN layer to further optimize the surface finish; perform annealing treatment at a temperature of 450 - 600 °C for 0.5 - 3 min to improve the grain orientation of the Ag nanostructure and enhance the plasmon resonance characteristics. The diameter of the polystyrene spheres is 200 - 1000 nm, and the size of the polystyrene spheres is adjusted to achieve plasmon enhancement of quantum dots with different wavelengths.

[0051] Step S5: Continuously deposit a SiO2 layer on the triangular-like metal Ag array, and then spin-coat and cure a quantum dot solution on the SiO2 layer 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 to ensure the uniformity of the SiO2 layer and prevent non-radiative recombination loss caused by direct contact between the quantum dots and Ag. The quantum dot concentration in the quantum dot solution is 8 - 10 mg / mL. The quantum dots are InP / ZnS or CdSe / CdS quantum dots, dissolved in n-hexane, toluene or n-octane, and the dispersion uniformity of the quantum dots needs to be ensured. After spin-coating the quantum dot solution, curing treatment is required. The curing treatment is carried out in an environment of 50 - 70 °C for 5 min to fix the quantum dot layer, reduce surface defects, and plasma treatment is selected to improve the bonding force between the quantum dot layer and the SiO2 interface and optimize the luminescence stability.

[0053] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific embodiments.

[0054] The P-type GaN layer in the following examples is formed as follows:

[0055] (1) Using metalorganic chemical vapor deposition technology, grow an AlN buffer layer with a thickness of about 15 - 45 nm on the patterned sapphire substrate surface;

[0056] (2) Sequentially grow an intrinsic GaN layer (thickness 2 μm), an N-type GaN layer (thickness 1 μm), an InGaN / GaN multiple quantum well light-emitting active region (emission wavelength around 475 nm) and a P-type GaN layer (thickness 500 nm) on the above AlN buffer layer.

[0057] Example 1

[0058] Refer to Figures 1 - 6 , this example provides a preparation method of a micro-LED structure based on the plasmon effect, which is specifically described as follows:

[0059] (1) Clean and deposit a mask layer. First, clean the surface of the P-type GaN layer with acetone, alcohol, and deionized water in sequence. Its surface cleanliness will directly affect whether the pattern obtained by imprinting has large-area orderliness; then deposit a SiO2 thin film layer by plasma-enhanced chemical vapor deposition (PECVD).

[0060] (2) Coating: Spin-coat a layer of TU2-170 / TU2-60 imprinting resist on the surface of the SiO2 thin film layer in the above step (1). The spin-coating conditions are 2000 rpm and a spin-coating time of 40 s. Then place it on a hot plate at 90 °C and dry it for 2 min to form an imprinting resist.

[0061] (3) Thermal nanoimprinting of the intermediate polymer soft template: First, place the nickel metal template with a nanohole array pattern on the nanoimprinting machine stage and closely cover the intermediate polymer soft template on it. Then heat the stage to 150 °C (145 - 160 °C), and transfer the nanohole array pattern on the nickel metal template to the intermediate polymer soft template by applying a certain pressure, and then cool down to demold. The nickel metal template used has a nanohole array with a period of 450 nm, a hole diameter of 200 nm, and a hole depth of 200 nm.

[0062] (4) Formation of the nanohole array mask template: Cover the patterned intermediate polymer soft template obtained in step (3) on the surface of the imprinting resist. Under the conditions of 90 °C and an exposure energy of 200 mJ / cm 2 , after ultraviolet lamp imprinting and curing for 2 min, demold. Thus, a series of imprinting resist nanohole array mask templates are formed on the surface of the SiO2 thin film layer.

[0063] (5) Dry etching: First, use the imprinting resist as a mask template and etch the surface SiO2 layer by inductively coupled plasma etching (ICP). Then switch the gas source and continue to etch the P-type GaN layer below the SiO2 layer. The etching time is set to 30 s, the etching depth is set to 150 nm, and the temperature is set to 15 °C. Then immerse the sample in a 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 on the inner wall of the nanopores caused by dry etching as much as possible and further deepen the etching depth of the nanopores, use a 2 mol / L KOH solution to perform wet chemical etching treatment on the sample. The solution temperature is set to 60 °C and the etching time is set to 30 s. Thus, the Ni metal nano-template pattern is successfully transferred to the P-type GaN layer, as Figure 3 shown.

[0065] (7) Preparation of the first layer of plasmonic Ag nanoparticles: Set the evaporation rate to and the evaporation angle to 50°. Use an electron beam evaporation coating machine to deposit metal Ag in the nanopores at the top of the P-type GaN layer. Use a ten-thousand-mesh sandpaper to grind and remove the residual Ag metal on the surface. Then, under a nitrogen atmosphere, perform rapid thermal annealing at 500 °C for 1 min and deposit a layer of SiO2 dielectric layer.

[0066] (8) Preparation of the second - layer plasmonic Ag nanoparticle layer. Polystyrene spheres with a diameter of 710 nm are used to prepare a monolayer of closely - arranged polystyrene sphere mask layer on the top of the P - type GaN layer after the above process. Then, metal Ag is deposited using an electron - beam evaporation coater, and the polystyrene sphere template and the remaining Ag metal are removed by soaking in a tetrahydrofuran solution to form a triangular - like metal Ag array, as Figure 4 shown.

[0067] (9) Preparation of the quantum dot layer. After the above process is completed, a 5 - nm - thick SiO2 layer is deposited using PECVD as an isolation layer between the quantum dots and the metal Ag. Then, the quantum dot layer is prepared using the spin - coating technique. The quantum dots used are InP / ZnS quantum dots dissolved in n - hexane with a concentration of 8 mg / mL, a luminescence wavelength of about 650 nm. The spin - coating speed is set to 1000 rpm, the spin - coating time is 50 s, and after spin - coating, it is placed in an environment of 50 - 70 °C for 5 min to be cured to obtain the quantum dot layer.

[0068] As Figure 5 、 6 shown are the photoluminescence spectra and the fluorescence decay curves of the quantum dots 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 the LED epitaxial wafer, and QW - QD - SP is the sample of the structure described in Example 1. Figure 5 It can be seen that the sample of the structure described in Example 1 has a strong emission peak at 648 nm, and the emission intensity is increased by nearly 5.5 times compared with the comparative sample, and the quantum dot color conversion has been greatly improved; Figure 6 It can be seen that the fluorescence decay rate of the sample of the structure described in Example 1 changes faster, indicating that the radiative recombination rate increases, promoting a higher color conversion efficiency of the quantum dots.

[0069] Example 2

[0070] This example provides a preparation method of a micro - LED structure based on the plasmonic effect, which is specifically described as follows:

[0071] (1) Cleaning and depositing the mask layer. First, the surface of the P - type GaN layer is cleaned successively with acetone, alcohol, and deionized water. Its surface cleanliness will directly affect whether the patterns obtained by imprinting have large - area orderliness. Then, a SiO2 thin - film layer is deposited using plasma - enhanced chemical vapor deposition (PECVD).

[0072] (2) Coating the glue. A layer of TU2 - 170 / TU2 - 60 imprinting glue is spin - coated on the surface of the SiO2 thin - film layer in step (1). The spin - coating conditions are 2000 rpm and a spin - coating time of 40 s, and then it is placed on a 90 °C hot plate and dried for 2 min to form the imprinting glue.

[0073] (3) Hot embossing of the intermediate polymer soft template: first, place the nickel metal template with the nanopore array pattern on the stage of the nanoimprinter, and tightly cover the intermediate polymer soft template on it; then heat the stage to 160°C, apply a certain pressure, transfer the nanopore array pattern on the nickel metal template to the intermediate polymer soft template, and cool it down for demolding. The nickel metal template used has a nanopore array with a period of 400nm, a hole diameter of 200nm, and a hole depth of 200nm.

[0074] (4) forming a nanopore array mask, covering the surface of the imprinted adhesive with the patterned intermediate polymer soft template obtained in step (3), and performing an exposure reaction at 100° C. and an exposure energy of 300 mJ / cm 2 Under the above conditions, the UV lamp was used for imprint curing for 2 minutes and then demolding was performed. Thus, a series of imprint glue nanopore array masks were formed on the surface of the SiO2 film layer.

[0075] (5) Dry etching: First, use the imprinted resin as a mask and use inductively coupled plasma etching (ICP) to etch the surface SiO2 layer. Then switch the gas source and continue to etch the P-type GaN layer under the SiO2 layer. The etching time is set to 60s, the etching depth is set to 200nm, and the temperature is set to 25°C. Then, the sample is immersed in a 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 nanopore caused by dry etching as much as possible and further deepen the etching depth of the nanopore, the sample was treated with wet chemical etching using a 1.5 mol / L KOH solution. The solution temperature was set at 70 °C and the etching time was set at 90 s. At this point, the Ni metal nanotemplate pattern was successfully transferred to the P-type GaN layer.

[0077] (7) Preparation of the first plasmon Ag nanoparticle layer, setting the evaporation rate to (, the evaporation angle is 45°, and an electron beam evaporation coating machine is used to deposit metal Ag in the nanopores on the top of the P-type GaN layer. The residual Ag metal on the surface is removed by grinding with 10,000-grit sandpaper, and then rapid thermal annealing is performed at 450°C for 0.5 min in a nitrogen atmosphere, and a SiO2 dielectric layer is deposited.

[0078] (8) The second layer of plasmon Ag nanoparticle layer is prepared by using polystyrene balls with a diameter of 500 nm. A single layer of tightly arranged polystyrene ball mask layer is prepared on the top of the P-type GaN layer after the above process is completed. Then, metal Ag is deposited using an electron beam evaporation coating machine, and the polystyrene ball template and residual Ag metal are removed by immersion in a tetrahydrofuran solution to form a triangular metal Ag array.

[0079] (9) Preparation of quantum dot layer: After the above process is completed, continue to deposit a SiO2 layer with a thickness of 12 nm by PECVD as the isolation layer between the quantum dots and metallic Ag. The quantum dots used are InP / ZnS quantum dots dissolved in n-hexane with a concentration of 9 mg / mL. A double-layer spin-coating technique is adopted to prepare the quantum dot layer to improve the uniformity and stability of the quantum dots, specifically as follows:

[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 °C, 3 min).

[0081] Second-layer spin-coating: Quantum dot solution with the same concentration, spin-coating speed 1000 rpm, spin-coating time 40 s. Finally, vacuum annealing treatment (100 °C, 5 min) is carried out to improve the compactness of the quantum dots, and the quantum dot layer is obtained after curing.

[0082] Performance comparison and results:

[0083] Photoluminescence spectrum analysis: The intensity of the emission peak of the quantum dots at 650 nm is 15% higher than that in Example 1; the color conversion efficiency (CCE) of the quantum dots is increased by about 12%. The CCE in Example 1 is 75%, and it reaches 87% in this example; the fluorescence decay time of the quantum dots is shortened by about 8%, indicating that the coupling effect between the quantum dots and the plasmons is enhanced and the non-radiative recombination is reduced.

[0084] Optimization of micro-LED application: Due to the improved uniformity of the quantum dot layer, the color consistency of the micro-LED pixels is better; the optical simulation results show that the structure in Example 2 uses a double-layer spin-coating technique to prepare the quantum dot layer. First, the compactness of the quantum dot layer is improved by a higher spin-coating speed (1200 rpm) and low-temperature curing (80 °C, 3 min). The subsequent second-layer spin-coating further distributes the quantum dots evenly. With the optimization of the second-layer Ag nanoparticle array, the light extraction efficiency can be increased by about 18% compared with Example 1, and the power loss can be reduced by about 10%.

[0085] Example 3

[0086] In this example, a 30-nm-thick AlN buffer layer is grown on the patterned sapphire substrate surface by metalorganic chemical vapor deposition (MOCVD) technology. 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 grown in sequence.

[0087] This example provides a preparation method for a micro-LED structure based on the plasmon effect, which is specifically described as follows:

[0088] (1) Clean and deposit the mask layer. First, clean the surface of the P-type GaN layer successively with acetone, alcohol, and deionized water. Its surface cleanliness will directly affect whether the patterns obtained by imprinting have large-area orderliness. Then, deposit a 50-nm-thick SiO2 thin film layer by plasma-enhanced chemical vapor deposition (PECVD).

[0089] (2) Spin-coat the glue. Spin-coat a layer of TU2-170 / TU2-60 imprinting glue on the surface of the SiO2 thin film layer in the above step (1). The spin-coating conditions are 2000 rpm and a spin-coating time of 40 s. Then, place it on a hot plate at 110 °C and dry it for 3 min to form the imprinting glue.

[0090] (3) Thermal nanoimprinting of the intermediate polymer soft template. First, place the nickel metal template with a nanohole array pattern on the nanoimprinting stage, and closely cover the intermediate polymer soft template on it. Then, heat the stage to 145 °C, and transfer the nanohole array pattern on the nickel metal template to the intermediate polymer soft template by applying a certain pressure, and then cool down to demold. The nickel metal template used has a nanohole array with a period of 400 nm, a pore diameter of 180 nm, and a pore depth of 180 nm.

[0091] (4) Form a nanohole array mask template. Cover the patterned intermediate polymer soft template obtained in step (3) on the surface of the imprinting glue. Under the conditions of 100 °C and an exposure energy of 300 mJ / cm 2 , after ultraviolet lamp imprinting and curing for 3 min, demold. Thus, a series of imprinting glue nanohole array mask templates are formed on the surface of the SiO2 thin film layer.

[0092] (5) Dry etching: First, use the imprinting glue as a mask template, and etch the surface SiO2 layer by inductively coupled plasma etching (ICP). Then, switch the gas source and continue to etch the P-type GaN layer below the SiO2 layer. The etching time is set to 90 s, the etching depth is set to 250 nm, and the temperature is set to 30 °C. Then, immerse the sample in a 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 pollution on the inner wall of the nanoholes caused by dry etching as much as possible and further deepen the etching depth of the nanoholes, use a 2-mol / L KOH solution to perform wet chemical etching treatment on the sample. The solution temperature is set to 80 °C, and the etching time is set to 120 s. Thus, the Ni metal nano-template pattern is successfully transferred to the P-type GaN layer.

[0094] (7) Preparation of the plasmonic Ag nanoparticle layer, set the evaporation rate to The evaporation angle is 45°. Using an electron beam evaporation coating machine, a single layer of metallic Ag is deposited on the top of the P-type GaN layer. The residual Ag metal on the surface is removed by grinding with 10,000-mesh sandpaper. Then, in a nitrogen atmosphere, rapid thermal annealing is carried out at 450 °C for 1 min.

[0095] (8) Preparation of the quantum dot layer. After the above process is completed, a SiO2 layer with a thickness of 40 nm is continuously deposited by PECVD as an isolation layer between the quantum dots and the metallic Ag. Then, the quantum dot layer is prepared by spin coating. 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 at 1200 rpm, and the spin coating time is 50 s. After spin coating, it is placed in an environment of 50 - 70 °C and maintained for 5 min to obtain a cured quantum dot layer by solidification.

[0096] In this embodiment, only a single-layer plasmonic structure is adopted. Compared with Embodiment 1, the quantum dot color conversion efficiency is reduced by about 16.3%, indicating that the double-layer plasmonic structure can more effectively enhance the light field coupling and improve the fluorescence efficiency. The enhancement amplitude of the quantum dot fluorescence emission intensity decreases (1.8 times → 1.3 times), indicating that the double-layer plasmonic structure can further optimize the light extraction efficiency. Since the double-layer nanostructure is not adopted, the quantum dot fluorescence lifetime is prolonged (4.1 ns → 3.2 ns, 3.2 ns → 4.1 ns), indicating that the plasma coupling enhancement effect is weak and the energy transfer efficiency is low.

[0097] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention. The technologies, shapes, and structures not described in detail in the present invention are all well-known technologies.

Claims

1. Preparation method of a micro-LED structure based on the plasmonic effect, characterized in that, The micro-LED structure is formed on the surface of the P-type GaN layer of the semiconductor. The preparation method includes the following steps: Deposit a SiO2 thin film layer on the surface of the pretreated P-type GaN layer and apply glue to form an imprinting glue. Use hot embossing technology to form a nanohole array pattern on the intermediate polymer soft template, cover it on the surface of the imprinting glue to form a nanohole array mask template. Based on the nanohole array mask template, etch the SiO2 thin film layer and the P-type GaN layer successively by dry etching and wet etching to form a nanohole array. After depositing metal Ag in the top nanoholes of the P-type GaN layer, perform grinding and annealing treatment, deposit the first layer of SiO2 dielectric layer, and then use polystyrene spheres as a mask to continue depositing metal Ag on the metal Ag and the SiO2 thin film layer to form a uniformly distributed triangular-like metal Ag array. Continue to deposit the second layer of SiO2 layer on the triangular-like metal Ag array, and then spin-coat and cure a quantum dot solution on the SiO2 layer to form a quantum dot layer.

2. The preparation method of the micro-LED structure based on the plasmon effect according to claim 1, characterized in that, The step of depositing a SiO2 thin film layer on the surface of the pretreated P-type GaN layer and applying glue to form an imprinting glue includes: Clean the surface of the P-type GaN layer successively with acetone, alcohol, and deionized water. Deposit a SiO2 thin film layer on the cleaned P-type GaN layer by plasma-enhanced chemical vapor deposition. After spin-coating the imprinting glue on the surface of the SiO2 thin film layer, place it in an environment of 90-110 °C and dry for 2-5 min, that is, form an imprinting glue on the SiO2 thin film layer.

3. The preparation method of the micro-LED structure based on the plasmon effect according to claim 1, wherein The step of using hot embossing technology to form a nanohole array pattern on the intermediate polymer soft template, cover it on the surface of the imprinting glue to form a nanohole array mask template includes: Place the nickel metal template with a nanohole array pattern on the nanoimprinting machine stage, closely cover the intermediate polymer soft template on it, heat the stage to 145-160 °C, and apply pressure to transfer the nanohole array pattern on the nickel metal template to the intermediate polymer soft template. Cover the surface of the imprinting resist with an intermediate polymer soft template having a nanohole array pattern, set the temperature to 90-100 °C, and the exposure energy to 100-300 mJ / cm 2 , perform ultraviolet imprinting treatment for 0.5-3 min, and demold to form a nanohole array mask template.

4. The preparation method of the micro-LED structure based on the plasmon effect according to claim 1, wherein The dry etching operation is as follows: Corresponding to the nanoholes in the nanohole array mask template, first etch the SiO2 thin film layer, and then continue to etch 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, soak it in BOE solution to remove the residual SiO2.

5. The preparation method of the micro-LED structure based on the plasmon effect according to claim 4, characterized in that, The wet etching uses a 1.5-2.5 mol / L KOH solution as the etching solution for wet etching, the etching temperature is 60-80 °C, and the etching time is 30-120 s.

6. The preparation method of the micro-LED structure based on the plasmonic effect according to claim 1, wherein, The step of depositing metal Ag in the top nanoholes of the P-type GaN layer, grinding and annealing treatment includes: Set the evaporation rate to The evaporation angle is 45° to 60°, and using an electron beam evaporation coating machine, deposit metallic Ag into the nanopores; Use mechanical polishing or ion beam grinding to remove the excessive metal Ag deposited on the surface of the P-type GaN layer. Anneal at a temperature of 450-600 °C for 0.5-3 min.

7. The preparation method of the micro-LED structure based on the plasmon effect according to claim 1, characterized in that, The diameter of the polystyrene spheres is 200-1000 nm.

8. The preparation method of the micro-LED structure based on the plasmonic effect according to claim 1, characterized in that, The thickness of the first layer of SiO2 dielectric layer is 5-15 nm, and the second layer is 5-40 nm.

9. The preparation method of the micro-LED structure based on the plasmonic 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. The micro-LED structure based on the plasmonic effect is characterized in that, It is prepared by using the preparation method described in any one of claims 1-9.

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