Preparation method of thin film miniature diode and thin film miniature diode

Abstract

The invention discloses a preparation method of a thin film micro-diode and the thin film micro-diode, which are applied to the technical field of micro-diodes, and comprises the following steps: setting a nano patterned substrate; the nano patterned substrate is provided with a top layer part and a bottom layer part based on the arranged nano columns, and the difference value between the energy density of laser irradiated to the top layer part based on the laser lift-off process and the energy density of laser irradiated to the bottom layer part does not exceed 80% of the laser energy density; epitaxially growing a GaN-based LED structure on the surface, provided with the nano columns, of the nano patterned substrate; and irradiating the nano patterned substrate by using laser based on a laser lift-off process, and separating the nano patterned substrate from the GaN-based LED structure. By using the nano patterned substrate, the GaN-based LED structure can have relatively high light emitting efficiency. And the stripping yield in the laser stripping process can be remarkably improved by regulating and controlling the energy density difference of the laser irradiated on the top layer part and the bottom layer part of the nano patterned substrate in the laser stripping process.

Description

Technical Field

[0001] This invention relates to the field of micro diode technology, and in particular to a method for fabricating a thin-film micro diode and a thin-film micro diode. Background Technology

[0002] In recent years, GaN-based Micro-LEDs (Micro Light-Emitting Diodes) have become core components of next-generation display technologies due to their advantages such as high brightness, high efficiency, and long lifespan.

[0003] In existing technologies, the fabrication of thin-film Micro-LEDs typically requires laser lift-off (LLO) to separate the GaN epitaxial layer from the sapphire substrate and transfer it to a silicon-based or other driving backplane. However, the current yield of laser lift-off is very low, only about 30%, which restricts the mass production and application of Micro-LEDs. Therefore, how to provide a high-yield method for fabricating thin-film micro-diodes is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a method for fabricating thin-film microdiodes that can ensure a high yield during laser ablation while also ensuring high light extraction efficiency of the thin-film microdiodes.

[0005] To solve the above-mentioned technical problems, the present invention provides a method for fabricating a thin-film microdiode, comprising:

[0006] A nanopatterned substrate is provided; the nanopatterned substrate is formed with a top layer and a bottom layer based on the provided nanopillars, and the difference between the energy density of the laser irradiated to the top layer and the energy density of the laser irradiated to the bottom layer based on the laser lift-off process does not exceed 80% of the laser energy density;

[0007] GaN-based LED structures are epitaxially grown on the surface of the nanopillars disposed on the nanopatterned substrate.

[0008] The nanopatterned substrate is separated from the GaN-based LED structure by using a laser lift-off process to irradiate the nanopatterned substrate with a laser.

[0009] Optionally, the height of the nanopillar is in the range of 700nm to 900nm, and the difference between the energy density of the laser irradiation on the top layer and the energy density of the laser irradiation on the bottom layer based on the laser ablation process does not exceed 30% of the laser energy density.

[0010] Optionally, the height of the nanopillar is in the range of 750nm to 850nm, the laser energy density irradiated by the laser ablation process is in the range of 400 mJ / cm² to 600 mJ / cm², and the difference between the energy density of the laser irradiated to the top layer and the energy density of the laser irradiated to the bottom layer is no more than 20% of the laser energy density.

[0011] Optionally, the pattern spacing of the nanopatterned substrate ranges from 0.01 μm to 1 μm, and the pattern period of the nanopatterned substrate ranges from 0.01 μm to 3 μm; the shape of the nanopillar includes any of the following:

[0012] Cone, frustum, cylinder, hexagonal pyramid.

[0013] Optionally, the wavelength of the laser is less than 360nm; the optical power of the laser is greater than 100mW.

[0014] Optionally, setting the nanopatterned substrate includes:

[0015] Spin-coating nanoimprint adhesive onto the substrate surface;

[0016] Nanoimprinting is performed on the nanoimprinting adhesive based on a stamp with a target nanopattern;

[0017] Based on reactive ion etching, using nanoimprinting adhesive after nanoimprinting as a mask, the target nanopattern is transferred to the substrate using etching gas to form a nanopattern substrate.

[0018] Optionally, epitaxially growing a GaN-based LED structure on the surface of the nanopillars disposed on the nanopatterned substrate includes:

[0019] A GaN nucleation layer is epitaxially grown on the surface of the nanopillars disposed on the nanopatterned substrate.

[0020] An undoped GaN layer is epitaxially grown on the surface of the GaN nucleation layer;

[0021] An N-type GaN layer, a multi-quantum-well active layer, a p-type AlGaN electron blocking layer, and a P-type GaN layer are sequentially epitaxially grown along the thickness direction on the surface of the undoped GaN layer to complete the fabrication of the GaN-based LED structure.

[0022] Optionally, separating the nanopatterned substrate from the GaN-based LED structure by irradiating the nanopatterned substrate with a laser using a laser lift-off process includes:

[0023] The surface of the GaN-based LED structure facing away from the nano-patterned substrate is temporarily bonded to the substrate.

[0024] The nanopatterned substrate is thinned from the surface of the nanopatterned substrate on the side opposite to the GaN-based LED structure, where the substrate is temporarily bonded;

[0025] A laser is used to irradiate the interface between the nanopatterned substrate and the GaN-based LED structure from the side of the thinned nanopatterned substrate facing away from the GaN-based LED structure, thereby separating the nanopatterned substrate from the GaN-based LED structure.

[0026] Optionally, after separating the nanopatterned substrate from the GaN-based LED structure, the method further includes:

[0027] The stripped GaN-based LED structure is transferred to the driver backplane.

[0028] The present invention also provides a thin-film microdiode, comprising a microdiode prepared by the method for preparing a thin-film microdiode as described in any one of the preceding claims.

[0029] The present invention provides a method for fabricating a thin-film micro diode, comprising: setting a nanopatterned substrate; the nanopatterned substrate having a top layer and a bottom layer formed on the set nanopillars, wherein the difference between the energy density of laser irradiation to the top layer and the energy density of laser irradiation to the bottom layer based on a laser lift-off process does not exceed 80% of the laser energy density; epitaxially growing a GaN-based LED structure on the surface of the nanopatterned substrate having nanopillars; and separating the nanopatterned substrate and the GaN-based LED structure by laser irradiation of the nanopatterned substrate based on a laser lift-off process.

[0030] Using a nanopatterned substrate to grow GaN-based LED structures ensures that the light-emitting surface of the GaN-based LED structure has a certain micro-nano structure, resulting in high light extraction efficiency. Furthermore, by controlling the energy density difference between the top and bottom layers of the nanopatterned substrate during laser lift-off, the yield rate of the laser lift-off process can be significantly improved.

[0031] The present invention also provides a thin-film micro diode, which has the same beneficial effects as described above, and will not be described in detail here. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0033] Figure 1A flowchart illustrating a method for fabricating a thin-film microdiode according to an embodiment of the present invention;

[0034] Figure 2 A flowchart illustrating a specific method for fabricating a thin-film microdiode according to an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of laser lift-off of a nanopatterned substrate. Detailed Implementation

[0036] The core of this invention is to provide a method for fabricating thin-film microdiodes. In existing technologies, the yield of laser lift-off is currently very low, only about 30%, which restricts the mass production and application of Micro-LEDs. While using traditional patterned sapphire substrates (PSS) as substrates for fabricating GaN-based LED structures can improve the light extraction efficiency of the LED structure, the uneven distribution of laser energy between the PSS and the GaN-based LED structure during laser lift-off leads to uneven laser energy absorption, resulting in a lift-off yield as low as about 30%, thus restricting the mass production and application of Micro-LEDs. Although planar substrates have a high lift-off yield, the light extraction efficiency of the LED structure is low, affecting the device's light-emitting performance.

[0037] The present invention provides a method for fabricating a thin-film micro diode, comprising: setting a nanopatterned substrate; the nanopatterned substrate having a top layer and a bottom layer formed on the set nanopillars, wherein the difference between the energy density of laser irradiation to the top layer and the energy density of laser irradiation to the bottom layer based on a laser lift-off process does not exceed 80% of the laser energy density; epitaxially growing a GaN-based LED structure on the surface of the nanopatterned substrate having nanopillars; and separating the nanopatterned substrate and the GaN-based LED structure by laser irradiation of the nanopatterned substrate based on a laser lift-off process.

[0038] Using a nanopatterned substrate to grow GaN-based LED structures ensures that the light-emitting surface of the GaN-based LED structure has a certain micro-nano structure, resulting in high light extraction efficiency. Furthermore, by controlling the energy density difference between the top and bottom layers of the nanopatterned substrate during laser lift-off, the yield rate of the laser lift-off process can be significantly improved.

[0039] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] Please refer to Figure 1 , Figure 1 This is a flowchart illustrating a method for fabricating a thin-film microdiode according to an embodiment of the present invention.

[0042] See Figure 1 In this embodiment, the method for fabricating a thin-film microdiode includes:

[0043] S101: Set the nano-patterned substrate.

[0044] In this embodiment, the nanopatterned substrate is formed with a top layer and a bottom layer based on the provided nanopillars. The difference between the energy density of the laser irradiated to the top layer and the energy density of the laser irradiated to the bottom layer based on the laser lift-off process does not exceed 80% of the laser energy density.

[0045] In this step, either a new nanopatterned substrate can be prepared or a previously used nanopatterned substrate can be used. The specific details of preparing the nanopatterned substrate will be described in detail in the following examples, and will not be repeated here.

[0046] The nanopatterned substrate prepared in this step has nanopillars formed on at least one side of its surface, and these nanopillars have nanopatterns formed on that side of the substrate. Each nanopillar has a certain height. In this embodiment, the end of the nanopillar furthest from the nanopatterned substrate is called the top end, and the end of the nanopillar closest to the substrate is called the bottom end. The structure formed by the top ends of all the nanopillars in this embodiment is called the top layer, and the structure formed by the bottom ends of all the nanopillars is called the bottom layer.

[0047] During subsequent laser lift-off, the laser typically irradiates the interface between the nanopatterned substrate and the GaN-based LED structure from the surface away from the GaN-based LED structure, i.e., irradiating the aforementioned nanopillars. The laser energy is then distributed between the top and bottom layers. The nanopillar configuration causes a difference in laser energy density between the top and bottom layers. In this embodiment, this difference must be less than or equal to 80% of the laser energy density, ensuring that the energy densities in the top and bottom layers are within a reasonable range. It should be noted that this embodiment does not specify a specific relationship between the laser energy densities in the top and bottom layers; this relationship may vary depending on the nanopillar morphology. This application specifically limits the difference between the laser energy densities in the top and bottom layers. When this difference does not exceed a preset range, the yield of the subsequent laser lift-off process can be effectively improved.

[0048] Laser lift-off involves irradiating the interface between the substrate and the GaN layer with a laser. The laser light is absorbed by the GaN at the interface and vaporizes, generating Ga vapor, thereby separating the substrate from the GaN-based LED structure. In this embodiment, by limiting the difference between the laser energy density in the top layer and the laser energy density in the bottom layer to no more than 80% of the laser energy density, relatively uniform Ga vapor generation at the interface between the substrate and the GaN layer can be ensured, effectively improving the yield of the separation between the substrate and the GaN-based LED structure.

[0049] Specifically, in this embodiment, the height of the nanopillars ranges from 700nm to 900nm. The difference between the energy density of the laser irradiation on the top layer and the energy density of the laser irradiation on the bottom layer, based on the laser lift-off process, does not exceed 30% of the laser energy density. That is, in this embodiment, the height of the nanopillars is specifically limited to around 800nm. This reduces the difference between the energy density of the laser irradiation on the top layer and the energy density of the laser irradiation on the bottom layer to no more than 30% of the laser energy density. This results in a more uniform energy distribution of the laser in the top and bottom layers, leading to more uniform Ga vapor generation and further improving the yield of the separation between the substrate and the GaN-based LED structure.

[0050] Specifically, in this embodiment, the height of the nanopillars ranges from 750 nm to 850 nm, and the laser energy density irradiated by the laser lift-off process ranges from 400 mJ / cm² to 600 mJ / cm². The difference between the energy density of the laser irradiated on the top layer and the energy density irradiated on the bottom layer does not exceed 20% of the laser energy density. In this embodiment, by further reducing the height range of the nanopillars and limiting the energy density of the laser irradiated by the laser lift-off process to approximately 500 mJ / cm² (400 mJ / cm² to 600 mJ / cm²), the difference between the energy density of the laser irradiated on the top layer and the energy density irradiated on the bottom layer can be further reduced, ensuring that the difference does not exceed 20% of the laser energy density. This further improves the yield of the separation between the substrate and the GaN-based LED structure.

[0051] It should be noted that in this embodiment, the height of the nanopillars in the patterned substrate is kept at around 800 nm, rather than being reduced indefinitely. The purpose is to ensure that the surface of the separated GaN-based LED structure has a certain degree of nanopatterning, thereby improving the light extraction efficiency of the GaN-based LED structure. Setting the height of the nanopillars in the patterned substrate to around 800 nm improves the light extraction efficiency by approximately 45% compared to using a flat substrate to fabricate a GaN-based LED structure, i.e., compared to a GaN-based LED structure with a flat light-emitting surface.

[0052] In this embodiment, the pattern spacing of the nanopatterned substrate ranges from 0.01 μm to 1 μm, and the pattern period of the nanopatterned substrate ranges from 0.01 μm to 3 μm. The shape of the nanopillars includes any one of the following: cone, frustum, cylinder, or hexagonal pyramid. By configuring the nanopillar array formed by multiple nanopillars in the above-mentioned nanopatterned substrate into the above structure, the light extraction efficiency of the GaN-based LED structure can be improved while ensuring a relatively uniform distribution of laser energy density.

[0053] S102: GaN-based LED structures are epitaxially grown on the surface of a nanopatterned substrate with nanopillars.

[0054] In this step, GaN-based LED structures are epitaxially grown on the surface of a nanopatterned substrate with nanopillars. This allows the light-emitting surface of the GaN-based LED structure to form a micro / nano structure corresponding to the nanopattern of the nanopatterned substrate, thereby increasing the light extraction efficiency of the GaN-based LED structure. The specific epitaxial growth process will be described in detail in the following embodiments and will not be repeated here.

[0055] S103: Based on laser lift-off process, a nanopatterned substrate is separated from the GaN-based LED structure by laser irradiation.

[0056] In this step, a laser is used to irradiate the interface between the nanopatterned substrate and the GaN-based LED structure from the surface of the nanopatterned substrate away from the GaN-based LED structure. This surface is typically planar to minimize laser energy loss. The laser beam ultimately strikes the interface where the nanopillars contact the GaN-based LED structure. The laser beam is absorbed by the GaN at the interface, causing it to vaporize and generate Ga vapor, thus separating the substrate from the GaN-based LED structure. After the laser beam acts on the nanopillar array, its energy distribution becomes dispersed, with some energy concentrated in the top layer and some in the bottom layer of the nanopatterned substrate, resulting in a difference in laser energy density between these two regions. In this embodiment, the difference between the energy density of the laser irradiating the top layer and the bottom layer is controlled to achieve a more uniform energy distribution, thereby generating Ga vapor more evenly and further improving the yield of the separation between the substrate and the GaN-based LED structure.

[0057] In this embodiment, the wavelength of the laser used in the above-mentioned laser ablation process is usually less than 360 nm, and it is preferably a laser emitted by a KrF excimer laser with a wavelength of 248 nm; the optical power of the laser is greater than 100 mW, and the laser energy density is set to 400 mJ / cm² to 500 mJ / cm².

[0058] This embodiment provides a method for fabricating a thin-film microdiode. Using a nanopatterned substrate to grow a GaN-based LED structure ensures that the light-emitting surface of the GaN-based LED structure has a certain micro / nano structure, resulting in high light extraction efficiency. Furthermore, by controlling the energy density difference between the top and bottom layers of the nanopatterned substrate during laser lift-off, the yield rate of the laser lift-off process can be significantly improved.

[0059] The specific details of the method for fabricating a thin-film microdiode provided by the present invention will be described in detail in the following embodiments.

[0060] Example 2

[0061] Please refer to Figure 2 as well as Figure 3 , Figure 2 A flowchart illustrating a specific method for fabricating a thin-film microdiode according to an embodiment of the present invention; Figure 3 This is a schematic diagram of laser lift-off of a nanopatterned substrate.

[0062] See Figure 2 In this embodiment, the method for fabricating a thin-film microdiode includes:

[0063] S201: Spin-coating nanoimprint adhesive onto the substrate surface.

[0064] The substrate used in this step can be a sapphire substrate without nanopillars. Of course, in this embodiment, the specific material of the substrate is not specifically limited and depends on the specific situation.

[0065] Before this step, the substrate usually needs to be cleaned. Specifically, the substrate can be cleaned using a standard cleaning process, such as the RCA (Radio Corporation of America) cleaning method, to remove contaminants and oxides from the substrate surface, and then dried with high-purity nitrogen.

[0066] In this step, a layer of nanoimprint adhesive will be spin-coated onto the surface of the substrate. The nanoimprint adhesive can be PMMA (polymethyl methacrylate), but in this embodiment, the specific material of the nanoimprint adhesive is not specifically limited and depends on the specific circumstances. It is necessary to ensure that the spin-coated nanoimprint adhesive has a uniform thickness in this step.

[0067] S202: Nanoimprint the nanoimprint adhesive based on a stamp with the target nanopattern.

[0068] In this step, a pre-prepared stamp with the target nanopattern is used for nanoimprinting. The pattern on the stamp can be a periodically arranged array of nanoconical shapes, with a pitch of 1.0 μm, a diameter of approximately 0.8 μm, and a height of 0.8 μm. The target nanopattern in the stamp corresponds to the nanopattern on the subsequently prepared nanopatterned substrate.

[0069] S203: Based on reactive ion etching process, using nanoimprint adhesive after nanoimprinting as a mask, the target nanopattern is transferred to the substrate using etching gas to form a nanopattern substrate.

[0070] In this step, reactive ion etching (RIE) technology can be used, with the nanoimprinted resist as a mask. Specifically, a Cl2 / BCl3-based etching gas can be used to precisely transfer the pattern of the nanoimprinted resist onto the substrate. By strictly controlling the ratio, power, and time of the etching gas, it can be ensured that the final pattern height on the substrate is 0.8±0.1μm, with smooth and steep sidewalls, thus completing the fabrication of the nanopatterned substrate.

[0071] Following this step, residual nanoimprint adhesive on the substrate surface can be removed using methods such as oxygen plasma to obtain a clean nano-patterned Sapphire Substrate (NPSS).

[0072] S204: GaN nucleation layer is epitaxially grown on the surface of a nanopatterned substrate with nanopillars.

[0073] In this embodiment, all film layers in the GaN-based LED structure are grown using a Metal-Organic Chemical Vapor Deposition (MOCVD) device. Prior to this step, the nanopatterned substrate typically needs to be annealed, specifically at a high temperature of approximately 1100°C under a hydrogen atmosphere. In this step, a GaN nucleation layer is epitaxially grown on the surface of the nanopatterned substrate at a low temperature of approximately 500°C. This GaN nucleation layer provides a high density and uniform distribution of nucleation sites for the subsequent fabrication of the GaN-based LED structure. The interface specifically irradiated by the laser in the subsequent laser lift-off process is the interface between this GaN nucleation layer and the nanopatterned substrate.

[0074] S205: An undoped GaN layer is epitaxially grown on the surface of a GaN nucleation layer.

[0075] In this step, an undoped GaN layer (u-GaN) of about 3 μm thickness needs to be grown at the temperature of S204.

[0076] S206: An N-type GaN layer, a multi-quantum-well active layer, a P-type AlGaN electron blocking layer, and a P-type GaN layer are sequentially epitaxially grown along the thickness direction on the surface of an undoped GaN layer to complete the fabrication of the GaN-based LED structure.

[0077] The thickness of the aforementioned N-type GaN layer (n-GaN) is approximately 2 μm, and it can specifically be a Si-doped GaN layer with a doping concentration of approximately [missing information]. The aforementioned multiple quantum well (MQW) active layer can specifically consist of five periods of InGaN / GaN quantum well structures, where the InGaN well layer thickness is approximately 2.5 nm and the GaN barrier layer thickness is approximately 12 nm. The aforementioned p-type AlGaN electron blocking layer is used to block electron diffusion, and the p-type GaN layer (p-GaN) is mainly used as a heavily doped contact layer. Specifically, it can be a Mg-doped GaN layer. The total thickness of the p-type AlGaN electron blocking layer and the p-type GaN layer is approximately 200 nm.

[0078] Thanks to the low and uniform pattern height of NPSS, the GaN-based LED structure crystal grown in this embodiment has high quality, and the internal stress can be effectively controlled with minimal warpage.

[0079] S207: Temporarily bond the surface of the GaN-based LED structure on the side facing away from the nano-patterned substrate to the substrate.

[0080] In this step, the surface of the GaN-based LED structure facing away from the nanopatterned substrate needs to be temporarily bonded to the substrate. This temporary bonding can be achieved using UV-curable adhesive, and the substrate can be a temporary silicon carrier substrate.

[0081] S208: Thinning of the nanopatterned substrate from the surface of the temporary bonded substrate facing away from the GaN-based LED structure.

[0082] In order to facilitate the laser penetration of the substrate and its action on the interface between the substrate and the GaN-based LED structure, the nano-patterned substrate needs to be thinned in this step. Specifically, the back side of the substrate can be mechanically ground and polished to reduce the substrate thickness to about 100 μm, thereby reducing the laser energy required for subsequent LLO.

[0083] S209: Use a laser to irradiate the interface between the nanopatterned substrate and the GaN-based LED structure from the side of the thinned nanopatterned substrate facing away from the GaN-based LED structure, thereby separating the nanopatterned substrate from the GaN-based LED structure.

[0084] See Figure 3 In this step, a KrF excimer laser with a wavelength of 248 nm can be used to emit laser light, with the laser energy density set to 400 mJ / cm²-500 mJ / cm², illuminating the interface between the substrate and GaN through the back side of the substrate. The laser light is absorbed by the GaN at the interface and vaporized, generating Ga vapor, thereby achieving separation.

[0085] In this embodiment, because the NPSS pattern height is only about 0.8 μm, the laser can penetrate more uniformly and act on the entire interface between the substrate and GaN, avoiding the shading effect and uneven energy density caused by excessive pattern height. The laser lift-off yield achieved in this embodiment is consistently above 96%.

[0086] S210: Transfer the stripped GaN-based LED structure to the driver backplane.

[0087] In this step, the thin-film GaN-based LED structure, peeled off and attached to the temporary bonding substrate, needs to be immersed in a solvent to remove bonding adhesives such as UV-curable adhesive, releasing the independent thin-film GaN-based LED structure. Subsequently, the GaN-based LED structure is precisely bonded to the final silicon-based CMOS driver backplane or TFT driver backplane using mass transfer technology, completing subsequent standard chip fabrication processes such as electrode preparation, passivation, and dicing.

[0088] It should be noted that the NPSS stripped in this embodiment can be reused for epitaxial growth of GaN-based LED structures after cleaning and surface treatment, thereby further reducing costs.

[0089] The method for fabricating a thin-film microdiode provided in this embodiment improves the laser lift-off yield to over 95%. Due to the photon scattering effect of the NPSS nanostructure, the light extraction efficiency of the device is improved by approximately 45% compared to planar substrate devices. As a result, under the same injection current, the device brightness is significantly improved, and the forward voltage does not degrade, achieving a balance between high brightness and low power consumption.

[0090] Example 3

[0091] The present invention also provides a thin-film microdiode, which comprises a thin-film microdiode fabricated by the fabrication method of a thin-film microdiode provided in any of the above embodiments. The specific details of the fabrication method of this thin-film microdiode have been described in detail in the above embodiments and will not be repeated here.

[0092] Since the thin-film microdiode provided in this embodiment of the invention is specifically fabricated based on the fabrication method of the thin-film microdiode provided in the above embodiment, the thin-film microdiode has a higher yield and thus can have a lower cost.

[0093] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0094] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0095] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0096] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0097] The foregoing has provided a detailed description of the fabrication method and the thin-film microdiode provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A method for fabricating a thin-film microdiode, characterized in that, include: A nanopatterned substrate is provided; the nanopatterned substrate is formed with a top layer and a bottom layer based on the provided nanopillars, and the difference between the energy density of the laser irradiated to the top layer and the energy density of the laser irradiated to the bottom layer based on the laser lift-off process does not exceed 80% of the laser energy density; GaN-based LED structures are epitaxially grown on the surface of the nanopillars disposed on the nanopatterned substrate. The nanopatterned substrate is separated from the GaN-based LED structure by using a laser lift-off process to irradiate the nanopatterned substrate with a laser.

2. The method according to claim 1, characterized in that, The height of the nanopillars ranges from 700 nm to 900 nm, and the difference between the energy density of the laser irradiation on the top layer and the energy density of the laser irradiation on the bottom layer based on the laser ablation process does not exceed 30% of the laser energy density.

3. The method according to claim 2, characterized in that, The height of the nanopillars ranges from 750 nm to 850 nm, the laser energy density irradiated by the laser ablation process ranges from 400 mJ / cm² to 600 mJ / cm², and the difference between the energy density of the laser irradiated to the top layer and the energy density of the laser irradiated to the bottom layer does not exceed 20% of the laser energy density.

4. The method according to claim 3, characterized in that, The pattern spacing of the nanopatterned substrate ranges from 0.01 μm to 1 μm, and the pattern period of the nanopatterned substrate ranges from 0.01 μm to 3 μm; the shape of the nanopillar includes any of the following: Cone, frustum, cylinder, hexagonal pyramid.

5. The method according to claim 3, characterized in that, The wavelength of the laser is less than 360nm; the optical power of the laser is greater than 100mW.

6. The method according to claim 1, characterized in that, Setting up a nano-patterned substrate includes: Spin-coating nanoimprint adhesive onto the substrate surface; Nanoimprinting is performed on the nanoimprinting adhesive based on a stamp with a target nanopattern; Based on reactive ion etching, using nanoimprinting adhesive after nanoimprinting as a mask, the target nanopattern is transferred to the substrate using etching gas to form a nanopattern substrate.

7. The method according to claim 1, characterized in that, The epitaxial growth of GaN-based LED structures on the surface of the nanopillars disposed on the nanopatterned substrate includes: A GaN nucleation layer is epitaxially grown on the surface of the nanopillars disposed on the nanopatterned substrate. An undoped GaN layer is epitaxially grown on the surface of the GaN nucleation layer; An N-type GaN layer, a multi-quantum-well active layer, a p-type AlGaN electron blocking layer, and a P-type GaN layer are sequentially epitaxially grown along the thickness direction on the surface of the undoped GaN layer to complete the fabrication of the GaN-based LED structure.

8. The method according to claim 1, characterized in that, Separating the nanopatterned substrate from the GaN-based LED structure using a laser lift-off process involves: The surface of the GaN-based LED structure facing away from the nano-patterned substrate is temporarily bonded to the substrate. The nanopatterned substrate is thinned from the surface of the nanopatterned substrate on the side opposite to the GaN-based LED structure, where the substrate is temporarily bonded; A laser is used to irradiate the interface between the nanopatterned substrate and the GaN-based LED structure from the side of the thinned nanopatterned substrate facing away from the GaN-based LED structure, thereby separating the nanopatterned substrate from the GaN-based LED structure.

9. The method according to claim 1, characterized in that, After separating the nanopatterned substrate from the GaN-based LED structure, the process further includes: The stripped GaN-based LED structure is transferred to the driver backplane.

10. A thin-film micro diode, characterized in that, This includes microdiodes prepared by the method for preparing thin-film microdiodes as described in any one of claims 1 to 9.

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