A Micro-LED with a collimated metasurface structure and a preparation method thereof

Abstract

The present invention belongs to the field of Micro-LED technology, and relates to a Micro-LED with a collimating metasurface structure and a preparation method thereof; the Micro-LED comprises: a Micro-LED light-emitting structure and a collimating metasurface structure; the collimating metasurface structure is arranged on one side of the light-emitting surface of the Micro-LED light-emitting structure, and is used to collimate and filter the light emitted by the Micro-LED light-emitting structure, so that the angle of the emitted light of the Micro-LED is less than the set angle; wherein the collimating metasurface structure comprises a first dielectric layer and a second dielectric layer, the first dielectric layer is arranged on the Micro-LED light-emitting structure, the first dielectric layer comprises a plurality of first collimating cylinders, and a groove is provided between two adjacent first collimating cylinders; the second dielectric layer is arranged at the bottom of the groove and the top of the first collimating cylinder; the refractive index of the first dielectric layer is less than the refractive index of the second dielectric layer. By adopting this scheme, the intensity and transmittance of the normal incident light can be improved, the intensity and transmittance of the oblique incident light can be reduced, the collimation effect of the light can be achieved, and the luminous efficiency can be improved.

Description

Technical Field

[0001] The present invention relates to the field of Micro-LED technology, and in particular to a Micro-LED with a collimated metasurface structure and a preparation method thereof. Background Art

[0002] Micro Light Emitting Diode (Micro-LED) uses tiny light emitting diodes (LED) as light-emitting elements. Each LED chip is a tiny independent light-emitting unit. By combining different LED chips, high-resolution images are created. It has a broad market in high-end displays, mobile device displays, flexible displays, augmented reality (AR), virtual reality (VR) and wearable devices.

[0003] Although Micro-LED has advantages such as higher brightness, higher contrast, wider color gamut and longer service life compared with traditional liquid crystal display (LCD) and organic light emitting diode (OLED), the light emitted by a simple Micro-LED is similar to a Lambertian radiator, and the spatial distribution of its luminous intensity conforms to the cosine law, that is, the radiation intensity of light beams emitted at different angles will change according to the cosine formula, and the larger the angle, the weaker the luminous intensity of the light beam. Therefore, the light intensity of each display chip in the Micro-LED is different at different emission angles, resulting in uneven light beam intensity of each display chip, which in turn makes the overall light intensity of the entire Micro-LED after combining the uneven intensity light beams emitted by each LED chip may be lower than expected. At the same time, the light beams emitted at different angles cause the Micro-LED beam divergence angle to be larger, resulting in low luminous efficiency of the Micro-LED.

[0004] In summary, existing Micro-LEDs have the problems of large beam divergence and low luminous efficiency. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the problems of large light beam divergence and low luminous efficiency of Micro-LED in the prior art.

[0006] In order to solve the above technical problems, the present application provides a Micro-LED with a collimated metasurface structure, comprising:

[0007] Micro-LED light-emitting structure;

[0008] A collimating metasurface structure, disposed on one side of the light-emitting surface of the Micro-LED light-emitting structure, for collimating and filtering the light emitted by the Micro-LED light-emitting structure so that the angle of the emitted light of the Micro-LED is smaller than a set angle;

[0009] The collimating metasurface structure includes a first dielectric layer and a second dielectric layer, the first dielectric layer is disposed on the Micro-LED light-emitting structure, the first dielectric layer includes a plurality of first collimating columns, and a groove is provided between two adjacent first collimating columns; the second dielectric layer is disposed at the bottom of the groove and the top of the first collimating column;

[0010] The refractive index of the first medium layer is smaller than the refractive index of the second medium layer.

[0011] In the present application, a collimating metasurface structure is provided on one side of a light-emitting surface of the Micro-LED light-emitting structure to collimate and filter the light emitted from the Micro-LED light-emitting structure. Specifically, a first collimating column, a second dielectric layer provided on the surface of the first collimating column, and a second dielectric layer provided between adjacent first collimating columns are designed on the light-emitting surface of the Micro-LED light-emitting structure using materials with different refractive indices, so that a double-layer periodic nanocolumn is formed using the first collimating column and the second dielectric layer, the second dielectric layer located on the surface of the first collimating column and the air form a first equivalent dielectric layer, the first collimating column and the second dielectric layer at the bottom of the groove form a second equivalent dielectric layer, and a quasi-FP cavity structure is formed by the first equivalent dielectric layer and the second equivalent dielectric layer to realize a function similar to a Fabry-Perot resonant cavity, and the Micro-LED light-emitting structure emits light. The normal incident light is incident perpendicular to the first equivalent dielectric layer and the second equivalent dielectric layer, and is reflected multiple times in the two equivalent dielectric layers. Since the direction of the light beam remains unchanged after each reflection, interference enhancement occurs to achieve high transmittance emission. The oblique incident light emitted by the Micro-LED light-emitting structure enters the FP-like cavity structure at a certain angle and is reflected. Since the phase of the light beam changes at each reflection in the two equivalent dielectric layers, the resonance condition of the FP-like cavity structure is destroyed, making it impossible for the FP-like cavity structure to perform interference enhancement on the oblique incident light beam, resulting in the oblique incident light finally being emitted with low transmittance, thereby increasing the intensity and transmittance of the normal incident light, reducing the intensity and transmittance of the oblique incident light, and achieving the collimation effect of light. Moreover, while filtering the oblique incident light, the normal incident light is emitted with high transmittance, thereby improving the luminous efficiency and light output energy of the Micro-LED.

[0012] Preferably, the second dielectric layer comprises a second collimating column and a plurality of third collimating columns, the second collimating column is arranged around the first collimating column, and the third collimating column is arranged on the top of the first collimating column;

[0013] Wherein, the thickness of the second collimating column is the same as the thickness of the third collimating column; and / or

[0014] The refractive index of the first collimating rod is smaller than the refractive index of the second collimating rod and / or the third collimating rod.

[0015] In the present application, the second dielectric layer may include a second collimating column arranged at the bottom of the groove and a third collimating column arranged at the top of the first collimating column. The first collimating column and the second collimating column constitute a first equivalent dielectric layer, and the third collimating column and air constitute a second equivalent dielectric layer to form a double-layer periodic nanocolumn.

[0016] Preferably, the bottom of the groove contacts the light emitting surface of the Micro-LED light emitting structure.

[0017] Furthermore, in some embodiments, the bottom of the groove directly contacts the light emitting surface of the Micro-LED light emitting structure, and the bottom of the second dielectric layer located at the groove directly contacts the light emitting surface of the Micro-LED light emitting structure, and the entire collimating metasurface structure is composed of a first collimating column and a second dielectric layer.

[0018] Preferably, the first dielectric layer further includes a fourth collimating column, which is disposed between adjacent first collimating columns, and the top of the fourth collimating column contacts the bottom of the groove, and the thickness of the fourth collimating column is smaller than that of the first collimating column.

[0019] In other embodiments, in addition to the first collimating cylinder, the first dielectric layer may also include a fourth collimating cylinder arranged between the first collimating cylinders, the top of the fourth collimating cylinder is in contact with the bottom of the groove, the second dielectric layer is arranged between the first collimating cylinder and the bottom of the groove, the second dielectric layer at the bottom of the groove forms a first equivalent dielectric layer with the first collimating cylinder, the second dielectric layer at the top of the first collimating cylinder forms a second equivalent dielectric layer with the air, and the entire metasurface collimation structure consists of the first collimating cylinder, the second dielectric layer and the fourth collimating cylinder.

[0020] Preferably, the collimating metasurface structure further includes a base layer, which is disposed on a side of a light emitting surface of the Micro-LED light emitting structure, and the first dielectric layer and the second dielectric layer are disposed on a side of the base layer away from the Micro-LED light emitting structure.

[0021] In the present application, a base layer arranged on the light-emitting surface of the Micro-LED light-emitting structure is used to provide a smooth growth plane for the first dielectric layer and the second dielectric layer, so that the FP-like cavity structure composed of the first collimating column and the second dielectric layer is more stable, which can effectively reduce the influence of the external environment such as vibration or temperature on the optical performance of the FP-like cavity, and further improve the collimation effect of the collimating metasurface on the light beam.

[0022] Preferably, the Micro-LED light emitting structure comprises a stacked p-type layer, a multi-quantum well layer and an n-type layer, and the collimating metasurface structure is arranged on a side of the n-type layer away from the multi-quantum well layer;

[0023] The thickness of the first dielectric layer is greater than or equal to the thickness of the second dielectric layer; and / or

[0024] The first collimating column is in the shape of a circular column or a square column; and / or

[0025] The size of the first collimating column is larger than the size of the groove; and / or

[0026] The material of the first dielectric layer includes silicon oxide and photoresist; and / or

[0027] The material of the second dielectric layer includes gallium nitride, titanium oxide, silicon nitride, and silicon; and / or

[0028] The material of the base layer includes silicon dioxide, gallium nitride, and photoresist; and / or

[0029] The wavelength of the emitted light of the Micro-LED is 532-632nm; and / or

[0030] The setting angle is 10° to 40°; and / or

[0031] The transmittance of the output light of the Micro-LED light emitting structure is in the range of 0.8~1.

[0032] In the present application, the thickness of the first collimating cylinder can be greater than or equal to the thickness of the second dielectric layer, so that the second dielectric layer located on the top of the first collimating cylinder can form an equivalent dielectric layer with the air; by limiting the shape of the first collimating cylinder, the size of the first collimating cylinder and the size of the groove, as well as the materials of the first dielectric layer, the second dielectric layer and the substrate layer, the divergence angle of the light beam with a wavelength of 532nm~632nm emitted by the Micro-LED can be limited to the range of 10°~40°, so that the transmittance of the light beam emitted by the Micro-LED light-emitting structure reaches 0.8~1.

[0033] Preferably, when the wavelength of the emitted light of the Micro-LED is 632 nm, the thickness of the first dielectric layer is 100 nm to 386 nm; the thickness of the second dielectric layer is 6.2 nm to 208 nm;

[0034] The diameter or side length of the first collimating column is 170nm~179nm;

[0035] The size ratio of the first collimating column to the groove is 17:8-179:38.

[0036] In the present application, when the wavelength of light emitted by the Micro-LED is 632nm, by limiting the thickness of the first dielectric layer and the second dielectric layer and the size of the first collimating cylinder and the groove, the collimating metasurface structure can constrain the beam divergence angle of the Micro-LED within the range of 10°~40°, while making the transmittance of the normally incident light reach 0.8~1, while filtering the oblique incident light, making the normally incident light emit with high transmittance, thereby improving the luminous efficiency and light output energy of the Micro-LED.

[0037] Preferably, when the wavelength of the emitted light of the Micro-LED is 532 nm, the thickness of the first dielectric layer is 229 nm to 400 nm; the thickness of the second dielectric layer is 80 nm to 227 nm;

[0038] The diameter or side length of the first collimating column is 50nm~100nm;

[0039] The size ratio of the first collimating column to the groove is 2:1-6:1.

[0040] In the present application, when the wavelength of light emitted by the Micro-LED is 532nm, by limiting the thickness of the first dielectric layer and the second dielectric layer and the size of the first collimating cylinder and the groove, the collimating metasurface structure can constrain the beam divergence angle of the Micro-LED within the range of 20°~40°, filter the oblique incident light and achieve a beam collimation effect.

[0041] On the other hand, the present application also provides a method for preparing a Micro-LED having a collimated metasurface structure, comprising:

[0042] Providing a Micro-LED light-emitting structure, and forming a first dielectric layer on a light-emitting surface of the Micro-LED light-emitting structure;

[0043] Etching the first dielectric layer to form a plurality of first collimating columns, wherein a groove is provided between two adjacent first collimating columns;

[0044] forming a second dielectric layer at the bottom of the groove and the top of the first collimating column to obtain the collimating metasurface structure;

[0045] Wherein, the refractive index of the first medium layer is smaller than the refractive index of the second medium layer.

[0046] Preferably, forming a first dielectric layer on the light emitting surface of the Micro-LED light emitting structure, and etching the first dielectric layer to form a plurality of first collimating columns comprises:

[0047] forming a base layer on the light emitting surface of the Micro-LED light emitting structure;

[0048] Forming the first dielectric layer on a surface of the substrate layer away from the Micro-LED light-emitting structure;

[0049] The first dielectric layer is exposed and developed by using a double-beam holographic exposure method to form the plurality of first collimating columns.

[0050] In the present application, a base layer is first formed on the light-emitting surface of the Micro-LED light-emitting structure, which can provide a smooth growth plane for the first dielectric layer and the second dielectric layer, so that the FP-like cavity structure composed of the first collimating column and the second dielectric layer is more stable, which can effectively reduce the influence of the external environment such as vibration or temperature on the optical performance of the FP-like cavity, and further improve the collimation effect of the collimating metasurface structure on the light beam; the first collimating column can be formed by exposing and developing the first dielectric layer using a double-beam holographic exposure method, without the need to design a separate mask, which can not only reduce production costs, but also save preparation time and improve production efficiency.

[0051] Compared with the prior art, this application has the following beneficial effects:

[0052] The present application forms a first dielectric layer on the light-emitting surface of the Micro-LED light-emitting structure; etches the first dielectric layer to form a plurality of first collimating columns, with a groove between two adjacent first collimating columns; forms a second dielectric layer with a refractive index greater than that of the first dielectric layer at the bottom of the groove and the top of the first collimating column, thereby forming a high-low refractive index dielectric layer. The present solution uses materials with different refractive indices to design a first collimating column, a second dielectric layer disposed on the surface of the first collimating column, and a second dielectric layer disposed between adjacent first collimating columns on the light-emitting surface of the Micro-LED light-emitting structure, thereby forming a double-layer periodic nanocolumn using the first collimating column and the second dielectric layer. The second dielectric layer located on the surface of the first collimating column and the air form a first equivalent dielectric layer, and the first collimating column and the second dielectric layer at the bottom of the groove form a second equivalent dielectric layer. A quasi-FP cavity structure is formed by the first equivalent dielectric layer and the second equivalent dielectric layer to realize a function similar to a Fabry-Perot resonant cavity. The normal incident light emitted from the Micro-LED surface is perpendicular to the first equivalent dielectric layer and the second equivalent dielectric layer. The oblique incident light emitted from the Micro-LED surface enters the FP-like cavity structure at a certain angle and reflects. Since the phase of the light beam changes at each reflection in the two equivalent dielectric layers, the resonance condition of the FP-like cavity structure is destroyed, making it impossible for the FP-like cavity structure to perform interference enhancement on the oblique incident light beam, resulting in the oblique incident light finally being emitted with low transmittance, thereby increasing the intensity and transmittance of the normal incident light and reducing the intensity and transmittance of the oblique incident light, which not only reduces the beam divergence angle and achieves the beam collimation effect, but also improves the top light output efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0054] Figure 1 A schematic diagram of the light beam of Micro-LED provided for this application;

[0055] Figure 2 A schematic diagram of the first structure of a Micro-LED with a collimated metasurface structure provided in this application;

[0056] Figure 3 A schematic diagram of the three-dimensional structure of a Micro-LED with a collimated metasurface structure provided in this application;

[0057] Figure 4 A second structural schematic diagram of a Micro-LED with a collimated metasurface structure provided in this application;

[0058] Figure 5 Schematic diagram of the FP-like cavity structure provided for this application;

[0059] Figure 6 A third structural schematic diagram of a Micro-LED with a collimated metasurface structure provided in this application;

[0060] Figure 7 A fourth structural schematic diagram of a Micro-LED with a collimated metasurface structure provided in this application;

[0061] Figure 8 A flow chart for preparing a Micro-LED with a collimated metasurface structure provided in this application; wherein: Figure 8 (a) is a schematic diagram of preparing the first dielectric layer on the Micro-LED light-emitting structure. Figure 8 (b) in Figure 8 Schematic diagram of preparing the first collimating column on the structure shown in (a). Figure 8 (c) in Figure 8 Schematic diagram of preparing a second dielectric layer on the structure shown in (b);

[0062] Fig. 9 The flowchart of preparing the first dielectric layer on the Micro-LED light-emitting structure provided in this application; wherein, Fig. 9 (a) is a schematic diagram of preparing a substrate layer on a Micro-LED light-emitting structure. Fig. 9 (b) in Fig. 9 Schematic diagram of preparing the first dielectric layer on the structure shown in (a); Fig. 9 (c) in Fig. 9 A schematic diagram of forming a first collimating column on the structure shown in (b);

[0063] Fig.10 A schematic diagram of a light beam transmittance curve obtained by simulating the aligned metasurface structure provided in Example 1;

[0064] Fig.11 A schematic diagram of a light beam transmittance curve obtained by simulating the aligned metasurface structure provided in Example 2;

[0065] Fig.12 A schematic diagram of a light beam transmittance curve obtained by simulating the aligned metasurface structure provided in Example 3;

[0066] Fig.13 A schematic diagram of a light beam transmittance curve obtained by simulating the aligned metasurface structure provided in Example 4;

[0067] Fig.14 A schematic diagram of a light beam transmittance curve obtained by simulating the aligned metasurface structure provided in Example 5;

[0068] Fig.15 A schematic diagram of a light beam transmittance curve obtained by simulating the aligned metasurface structure provided in Example 6;

[0069] Fig.16 A schematic diagram of the side electric field strength obtained by simulating the aligned metasurface structure provided in Example 6;

[0070] Explanation of the reference numerals in the specification: 1. Micro-LED light-emitting structure; 11. p-type layer; 12. Multi-quantum well layer; 13. n-type layer; 2. Collimated metasurface structure; 21. First dielectric layer; 211. First collimated column; 212. Fourth collimated column; 213. Groove; 22. Second dielectric layer; 221. Second collimated column; 222. Third collimated column; 23. Base layer. DETAILED DESCRIPTION

[0071] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0072] See also Figure 1 , Figure 1 The schematic diagram of the light beam of Micro-LED provided for this application shows that the light-emitting surface of Micro-LED can be regarded as countless light-emitting points integrated on a plane. Each light-emitting point will emit normal light perpendicular to the light-emitting surface and oblique light with a certain angle to the light-emitting surface. The angle of the oblique light is the light beam divergence angle. In order to improve the characteristics of Micro-LED, it is necessary to reduce the transmittance of the oblique light as much as possible, increase the transmittance of the normal light, and reduce the light beam divergence angle.

[0073] See also Figure 2 , Figure 2 A schematic cross-sectional structure diagram of a Micro-LED with a collimated metasurface structure provided in this application, Figure 3 This is a schematic diagram of the three-dimensional structure of a Micro-LED with a collimated metasurface structure provided in the present application. The Micro-LED with a collimated metasurface structure includes: a Micro-LED light-emitting structure 1 and a collimated metasurface structure 2.

[0074] The collimating metasurface structure 2 is disposed on one side of the light-emitting surface of the Micro-LED light-emitting structure 1. The collimating metasurface structure 2 is used to collimate and filter the light emitted by the Micro-LED light-emitting structure 1 so that the angle of the Micro-LED light emitted is less than a set angle. Specifically, the set angle is 10° to 40°, for example, the set angle can be 10°, 15°, 20°, 25°, 30°, 35° or 40°.

[0075] Among them, the collimating metasurface structure 2 includes a first dielectric layer 21 and a second dielectric layer 22. The first dielectric layer 21 is arranged on the Micro-LED light-emitting structure 1. The first dielectric layer 21 includes a plurality of first collimating cylinders 211, and a groove is provided between two adjacent first collimating cylinders 211; the second dielectric layer 22 is arranged at the bottom of the groove and the top of the first collimating cylinder 211, and the refractive index of the first dielectric layer 21 is less than the refractive index of the second dielectric layer 22.

[0076] Furthermore, the thickness of the first dielectric layer 21 is greater than or equal to the thickness of the second dielectric layer 22 .

[0077] Furthermore, the material of the first dielectric layer 21 includes silicon oxide and photoresist; the material of the second dielectric layer 22 includes gallium nitride, titanium oxide, silicon nitride, and silicon.

[0078] Further, the shape of the first collimating column 211 is a circular column or a square column; and / or the size of the first collimating column 211 is larger than the size of the groove.

[0079] The present embodiment does not limit the shapes of the first collimating cylinder 211 and the groove. For example, the shape of the groove may be a cylinder, a truncated cone, or a cubic column. The shape of the first collimating cylinder 211 may be a cylinder or a cubic column, and the shape of its side cross-sectional view may be a rectangle. When the shapes of the first collimating cylinder 211 and the groove are cylinders, the dimensions of the first collimating cylinder 211 and the groove are the dimensions of the cross section, that is, the diameter of the cylinder; when the first collimating cylinder 211 and the groove are cubic columns, the dimensions of the first collimating cylinder 211 and the groove refer to the side length of the cross section.

[0080] In a specific embodiment, Figure 4 As shown, the Micro-LED light emitting structure 1 includes a stacked p-type layer 11 , a multi-quantum well layer 12 , and an n-type layer 13 , and the collimating metasurface structure 2 is arranged on a side of the n-type layer 13 away from the multi-quantum well layer 12 .

[0081] In a specific embodiment, Figure 2 As shown, the second dielectric layer 22 includes a second collimating column 221 and a plurality of third collimating columns 222 . The second collimating column 221 is disposed around the first collimating column 211 , and the third collimating column 222 is disposed on the top of the first collimating column 211 .

[0082] Further, the thickness of the second collimating column 221 is the same as the thickness of the third collimating column 222 .

[0083] Further, the refractive index of the first collimating cylinder 211 is smaller than that of the second collimating cylinder 221 ; or, the refractive index of the first collimating cylinder 211 is smaller than that of the third collimating cylinder 222 , or the refractive index of the first collimating cylinder 211 is smaller than that of both the second collimating cylinder 221 and the third collimating cylinder 222 .

[0084] Furthermore, if Figure 5 As shown, the first collimating cylinder 211, the second collimating cylinder 221 and the third collimating cylinder 222 form a FP-like cavity structure, and a plurality of periodically arranged FP-like cavity structures form a collimating metasurface structure; represents the thickness of the first collimating column 211, that is, the thickness of the first dielectric layer 21; represents the thickness of the second collimating cylinder 221 and the third collimating cylinder 222; represents the size of the first collimating cylinder 211; Represents the size of a single FP-like cavity structure.

[0085] The collimation effect of the collimating metasurface structure can be changed by changing the size of the FP-like cavity structure. In some embodiments, the size of the FP-like cavity structure can be optimized using a particle swarm algorithm. First, the wavelength of the output light of the Micro-LED is set, and every two degrees from 0° to 90° is set as an incident light angle to be simulated, and an objective function is constructed based on the transmittance of the super-collimating surface structure at each incident light angle to be simulated. For example, ,in, , , , , They represent the transmittance when the incident light angles to be simulated are 0°, 2°, 4°, 6° and 8° respectively. represents the sum of the transmittances of all incident light angles to be simulated, It indicates the ratio of the transmittance of light with an incident angle within 8° to the transmittance of light with all angles.

[0086] Will , , and Set it as the optimized independent variable and set the value range of each variable. By adjusting the value of each variable, the size of the FP-like cavity structure is continuously changed. Then, the time-domain finite difference method is used to simulate the transmittance of the collimating metasurface structure at each incident light to be simulated when the FP-like cavity structure has different sizes, so as to obtain the target size that makes the objective function closest to the ideal value within the value range of each variable, thereby obtaining the FP-like cavity structure size with the best wavelength collimation filtering effect on the output light of Micro-LED.

[0087] Further, in one embodiment, if Figure 2 As shown, the bottom of the groove contacts the light emitting surface of the Micro-LED light emitting structure 1 .

[0088] In another embodiment, Figure 6 As shown, the first dielectric layer 21 further includes a fourth collimating column 212 , which is disposed between adjacent first collimating columns 211 , and the top of the fourth collimating column 212 contacts the bottom of the groove, and the thickness of the fourth collimating column 212 is less than that of the first collimating column 211 .

[0089] In a specific embodiment, Figure 7 As shown, the collimating metasurface structure 2 further includes a base layer 23 , which is disposed on the light emitting surface side of the Micro-LED light emitting structure 1 , and the first dielectric layer 21 and the second dielectric layer 22 are disposed on the side of the base layer 23 away from the Micro-LED light emitting structure 1 .

[0090] Furthermore, the material of the base layer 23 includes silicon dioxide, gallium nitride, silicon oxide, and photoresist.

[0091] The base layer 23 is used to provide a smooth growth plane for the first dielectric layer 21 and the second dielectric layer 22, so that the FP-like cavity structure composed of the first collimating column 211 and the second dielectric layer 22 is more stable, which can effectively reduce the influence of the external environment such as vibration or temperature on the optical performance of the FP-like cavity, and further improve the collimation effect of the collimating metasurface structure 2 on the light beam.

[0092] In other specific embodiments, the wavelength of the output light of the Micro-LED is 532-632 nm; for example, the wavelength of the output light of the Micro-LED can be 532 nm, 580 nm, 600 nm, or 632 nm.

[0093] Furthermore, the transmittance of the output light of the Micro-LED light emitting structure 1 is in the range of 0.8~1.

[0094] In one embodiment, when the wavelength of the output light of the Micro-LED is 632nm, the thickness of the first dielectric layer 21 is 100nm~386nm; the thickness of the second dielectric layer 22 is 6.2nm~208nm; the diameter or side length of the first collimating column 211 is 170nm~179nm; the size ratio of the first collimating column 211 to the groove is 17:8~179:38.

[0095] When the wavelength of light emitted by the Micro-LED is 632nm, by limiting the thickness of the first dielectric layer 21 and the second dielectric layer 22 and the size of the first collimating cylinder 211 and the groove, the collimating metasurface structure 2 can constrain the light beam divergence angle of the Micro-LED within the range of 10°~40°, and at the same time make the transmittance of the normally incident light reach 0.8~1, while filtering the oblique incident light, the normally incident light is emitted with high transmittance, thereby improving the luminous efficiency and light output energy of the Micro-LED.

[0096] In another embodiment, when the wavelength of the output light of the Micro-LED is 532nm, the thickness of the first dielectric layer 21 is 229nm~400nm; the thickness of the second dielectric layer 22 is 80nm~227nm; the diameter or side length of the first collimating column 211 is 50nm~100nm; the size ratio of the first collimating column 211 to the groove is 2:1~6:1.

[0097] When the wavelength of the light emitted by the Micro-LED is 532nm, by limiting the thickness of the first dielectric layer 21 and the second dielectric layer 22 and the size of the first collimating cylinder 211 and the groove, the collimating metasurface structure 2 can constrain the beam divergence angle of the Micro-LED within the range of 20°~40°, filter the oblique incident light and achieve a beam collimation effect.

[0098] See also Figure 8 , Figure 8 A flowchart of a method for preparing a Micro-LED having a collimated metasurface structure provided in the present application, the method comprising the following steps:

[0099] S10: providing a Micro-LED light emitting structure 1, and forming a first dielectric layer 21 on the light emitting surface of the Micro-LED light emitting structure 1, such as Figure 8 As shown in (a) in .

[0100] S20: Etching the first dielectric layer 21 to form a plurality of first collimating columns 211, wherein a groove 213 is provided between two adjacent first collimating columns 211, such as Figure 8 As shown in (b) in .

[0101] S30: forming a second dielectric layer 22 at the bottom of the groove 213 and the top of the first collimating column 211 to obtain a collimating metasurface structure 2, such as Figure 8 As shown in (c) in .

[0102] The refractive index of the first dielectric layer 21 is less than the refractive index of the second dielectric layer 22. Optionally, the material of the second dielectric layer 22 is one of gallium nitride, titanium oxide, silicon nitride and silicon.

[0103] In a specific implementation, the second dielectric layer 22 is formed on the bottom of the groove 213 and the top of the first collimating column 211 by using a vacuum magnetron sputtering method.

[0104] In a specific embodiment, Fig. 9 The figure shows a preparation flow chart of forming a first dielectric layer on the light emitting surface of the Micro-LED light emitting structure, etching the first dielectric layer, and forming a plurality of first collimating columns, which specifically includes:

[0105] S21: forming a base layer 23 on the light emitting surface of the Micro-LED light emitting structure 1, such as Fig. 9 As shown in (a) in .

[0106] The material of the base layer 23 is one of silicon dioxide, gallium nitride, and photoresist; by first forming the base layer 23 on the light-emitting surface of the Micro-LED light-emitting structure 1, a smooth growth surface is provided for the FP-like cavity structure, which can make the FP-like cavity structure more stable.

[0107] S22: forming a first dielectric layer 21 on a surface of the substrate layer 23 away from the Micro-LED light emitting structure 1, such as Fig. 9 As shown in (b) in .

[0108] The material of the first dielectric layer 21 is one of silicon oxide and photoresist.

[0109] In a specific embodiment, the material of the first dielectric layer 21 is photoresist, which is spin-coated on the base layer 23 using a spin-coating machine, and the structure with the photoresist is placed on a hot plate for pre-baking to stabilize the photoresist, thereby forming the first dielectric layer 21 .

[0110] S23: Expose and develop the first dielectric layer 21 using a double-beam holographic exposure method to form a plurality of first collimating columns 211, such as Fig. 9 As shown in (c) in .

[0111] The first collimating pillars 211 have a thickness of about 230 nm, a width of about 150 nm, a spacing of about 25 nm, and a period of 200 nm.

[0112] In this embodiment, dielectric materials with different refractive indices are used to design a first collimating column, a second dielectric layer arranged on the surface of the first collimating column, and a second dielectric layer arranged between adjacent first collimating columns on the light-emitting surface of the Micro-LED light-emitting structure, so that the first collimating column and the second dielectric layer are used to form a double-layer periodic nanocolumn, the second dielectric layer located on the surface of the first collimating column and the air form a first equivalent dielectric layer, the first collimating column and the second dielectric layer at the bottom of the groove form a second equivalent dielectric layer, and a quasi-FP cavity structure is formed by the first equivalent dielectric layer and the second equivalent dielectric layer to achieve a function similar to a Fabry-Perot resonant cavity. The normal incident light emitted from the surface of the Micro-LED is perpendicular to the first equivalent dielectric layer and the second equivalent dielectric layer, and is reflected multiple times in the two equivalent dielectric layers. Due to the direction of the light beam after each reflection, the FP cavity structure is similar to the Fabry-Perot resonant cavity. The direction remains unchanged, thereby interference enhancement occurs to achieve high transmittance emission, and the oblique incident light emitted from the Micro-LED surface enters the FP-like cavity structure at a certain angle and reflects. Since the phase of the light beam changes each time it is reflected in the two equivalent dielectric layers, the resonance condition of the FP-like cavity structure is destroyed, making it impossible for the FP-like cavity structure to perform interference enhancement on the oblique incident light beam, causing the oblique incident light to eventually be emitted with low transmittance, thereby increasing the intensity and transmittance of the normal incident light, reducing the intensity and transmittance of the oblique incident light, achieving the collimation effect of light, and being able to achieve focused imaging function in a quasi-two-dimensional plane at the sub-wavelength level, which can greatly reduce the weight and volume of the imaging system, and has the advantage of integration; in addition, the material of the collimating metasurface structure can be flexibly selected according to the Micro-LEDs of different powers to increase its transmittance.

[0113] The above-mentioned FP-like cavity structure can achieve high intensity and high transmittance for normally incident light, and low transmittance for obliquely incident light. The preparation difficulty is much lower than that of traditional nanocolumn metasurfaces. Compared with traditional multi-layer DBR collimation structures, the preparation difficulty and cost of the double-layer structure are greatly reduced.

[0114] The technical solution of the present application is described in more detail below in combination with a plurality of embodiments, but it should be understood that the following embodiments are only for explaining and illustrating the technical solution and do not limit the scope of the present application. Example 1

[0115] This embodiment provides a simulation method for a collimating metasurface structure, which uses a finite difference time domain method (FDTD) method to simulate the filtering and collimating effect of the collimating metasurface structure, and specifically includes the following steps:

[0116] S1: Provide a Micro-LED light emitting structure with a wavelength of 632nm.

[0117] S2: Disposing a first dielectric layer on a surface of a light emitting surface of the Micro-LED light emitting structure.

[0118] The first dielectric layer is a photoresist layer with a thickness of 100nm; the first dielectric layer includes a plurality of first collimating columns with a size of 170nm, and there are grooves with a size of 40nm between adjacent first collimating columns; the size of a single FP-like cavity structure is 250nm; the shapes of the first collimating columns and the grooves are both cubic columns.

[0119] S3: forming a second dielectric layer on the top of the first collimating column and the bottom of the groove to obtain a collimating metasurface structure.

[0120] The material of the second dielectric layer is silicon, and the thickness is 6.2 nm.

[0121] S4: Adjust the angle at which the light emitted from the Micro-LED light-emitting structure enters the collimating metasurface structure, and use FDTD to simulate the collimating effect of the collimating metasurface structure to obtain Fig.10 The transmittance curve is shown.

[0122] from Fig.10 It can be seen that when a light beam with an incident angle of less than 40° enters the collimating metasurface structure, its transmittance is close to 1; and after the light beam with an incident angle greater than 40° enters the collimating metasurface structure, the transmittance quickly drops to 0, indicating that the collimating metasurface structure provided in this embodiment can filter out light beams with incident angles greater than 40° emitted from the Micro-LED light-emitting structure for a Micro-LED light-emitting structure with a wavelength of 632nm, thereby achieving a collimating effect. Example 2

[0123] This embodiment provides a simulation method for a collimating metasurface structure, which uses an FDTD method to simulate the filtering and collimating effect of the collimating metasurface structure, and specifically includes the following steps:

[0124] S1: Provide a Micro-LED light emitting structure with a wavelength of 632nm.

[0125] S2: Disposing a first dielectric layer on a surface of a light emitting surface of the Micro-LED light emitting structure.

[0126] The first dielectric layer is a photoresist layer with a thickness of 386nm; the first dielectric layer includes a plurality of first collimating columns with a size of 179nm, and there are grooves with a size of 38nm between adjacent first collimating columns; the size of a single FP-like cavity structure is 255nm; the shapes of the first collimating columns and the grooves are both cubic columns.

[0127] S3: forming a second dielectric layer on the top of the first collimating column and the bottom of the groove to obtain a collimating metasurface structure.

[0128] The material of the second dielectric layer is silicon, and the thickness is 208 nm.

[0129] S4: Adjust the angle at which the light emitted from the Micro-LED light-emitting structure enters the collimating metasurface structure, and use FDTD to simulate the collimating effect of the collimating metasurface structure to obtain Fig.11 The transmittance curve is shown.

[0130] from Fig.11 It can be seen that when a light beam with an incident angle of less than 10° enters the collimating metasurface structure, its transmittance is roughly between 0.1 and 0.8; and after the light beam with an incident angle greater than 10° enters the collimating metasurface structure, the transmittance quickly drops to 0, indicating that the collimating metasurface structure provided in this embodiment can filter out light beams with incident angles greater than 10° emitted from the Micro-LED light-emitting structure for a Micro-LED light-emitting structure with a wavelength of 632nm, thereby achieving a collimating effect. Example 3

[0131] This embodiment provides a simulation method for a collimating metasurface structure, which uses an FDTD method to simulate the filtering and collimating effect of the collimating metasurface structure, and specifically includes the following steps:

[0132] S1: Provide a Micro-LED light-emitting structure with a wavelength of 532nm.

[0133] S2: Disposing a first dielectric layer on a surface of a light emitting surface of the Micro-LED light emitting structure.

[0134] The first dielectric layer is a photoresist layer with a thickness of 229nm; the first dielectric layer includes a plurality of first collimating columns with a size of 150nm, and there are grooves with a size of 25nm between adjacent first collimating columns; the size of a single FP-like cavity structure is 200nm; the shapes of the first collimating columns and the grooves are both cubic columns.

[0135] S3: forming a second dielectric layer on the top of the first collimating column and the bottom of the groove to obtain a collimating metasurface structure.

[0136] The material of the second dielectric layer is silicon, and the thickness is 227 nm.

[0137] S4: Adjust the angle at which the light emitted from the Micro-LED light-emitting structure enters the collimating metasurface structure, and use FDTD to simulate the collimating effect of the collimating metasurface structure to obtain Fig.12 The transmittance curve is shown.

[0138] from Fig.12It can be seen that when a light beam with an incident angle of less than 20° enters the collimating metasurface structure, its transmittance is roughly between 0.3 and 0.4; and after the light beam with an incident angle greater than 20° enters the collimating metasurface structure, the transmittance quickly drops to 0, indicating that the collimating metasurface structure provided in this embodiment can filter out the light beam with an incident angle greater than 20° emitted from the Micro-LED light-emitting structure for a Micro-LED light-emitting structure with a wavelength of 532nm, thereby achieving a collimation effect. Example 4

[0139] This embodiment provides a simulation method for a collimating metasurface structure, which uses an FDTD method to simulate the filtering and collimating effect of the collimating metasurface structure, and specifically includes the following steps:

[0140] S1: Provide a Micro-LED light-emitting structure with a wavelength of 532nm.

[0141] S2: Disposing a first dielectric layer on a surface of a light emitting surface of the Micro-LED light emitting structure.

[0142] The first dielectric layer is a photoresist layer with a thickness of 400nm; the first dielectric layer includes a plurality of first collimating columns with a size of 50nm, and there are grooves with a size of 25nm between adjacent first collimating columns; the size of a single FP-like cavity structure is 100nm; the shapes of the first collimating columns and the grooves are both cubic columns.

[0143] S3: forming a second dielectric layer on the top of the first collimating column and the bottom of the groove to obtain a collimating metasurface structure.

[0144] The material of the second dielectric layer is silicon, and the thickness is 80 nm.

[0145] S4: Adjust the angle at which the light emitted from the Micro-LED light-emitting structure enters the collimating metasurface structure, and use FDTD to simulate the collimating effect of the collimating metasurface structure to obtain Fig.13 The transmittance curve is shown.

[0146] from Fig.13 It can be seen that when a light beam with an incident angle of less than 40° enters the collimating metasurface structure, its transmittance is between 0.6 and 0.9; and after the light beam with an incident angle greater than 40° enters the collimating metasurface structure, the transmittance quickly drops to 0, indicating that the collimating metasurface structure provided in this embodiment can filter out light beams with incident angles greater than 40° emitted from the Micro-LED light-emitting structure for a Micro-LED light-emitting structure with a wavelength of 532nm, thereby achieving a collimating effect. Example 5

[0147] This embodiment provides a simulation method for a collimating metasurface structure, which uses an FDTD method to simulate the filtering and collimating effect of the collimating metasurface structure, and specifically includes the following steps:

[0148] S1: Provide a Micro-LED light-emitting structure with a wavelength of 532nm.

[0149] S2: A base layer is disposed on the surface of the light emitting surface of the Micro-LED light emitting structure.

[0150] The material of the base layer is silicon oxide.

[0151] S3: Disposing a first dielectric layer on a side of the substrate layer away from the light emitting surface of the Micro-LED light emitting structure.

[0152] The first dielectric layer is a photoresist layer with a thickness of 400 nm; the first dielectric layer includes a plurality of first collimating columns with a size of 50 nm, and grooves with a size of 25 nm are provided between adjacent first collimating columns; the shapes of the first collimating columns and the grooves are both cubic columns.

[0153] S4: forming a second dielectric layer on the top of the first collimating column and the bottom of the groove to obtain a collimating metasurface structure.

[0154] The material of the second dielectric layer is silicon, and the thickness is 80 nm.

[0155] S5: Adjust the angle at which the light emitted from the Micro-LED light-emitting structure enters the collimating metasurface structure, and use FDTD to simulate the collimating effect of the collimating metasurface structure to obtain Fig.14 The transmittance curve is shown.

[0156] from Fig.14 It can be seen that after the base layer is set on the light emitting surface side of the Micro-LED light emitting structure, the transmittance is close to 0 after the light beam with an incident angle greater than 35° enters the collimating metasurface structure, indicating that the collimating metasurface structure provided in this embodiment can filter out the light beam with an incident angle greater than 35° emitted from the Micro-LED light emitting structure for the Micro-LED light emitting structure with a wavelength of 532nm, thereby achieving a collimating effect. Example 6

[0157] This embodiment provides a simulation method for a collimating metasurface structure, which uses an FDTD method to simulate the filtering and collimating effect of the collimating metasurface structure, and specifically includes the following steps:

[0158] S1: Provide a Micro-LED light-emitting structure with a wavelength of 532nm.

[0159] S2: A base layer is disposed on the surface of the light emitting surface of the Micro-LED light emitting structure.

[0160] The material of the base layer is gallium nitride.

[0161] S3: Disposing a first dielectric layer on a side of the substrate layer away from the light emitting surface of the Micro-LED light emitting structure.

[0162] The first dielectric layer is a photoresist layer with a thickness of 400 nm; the first dielectric layer includes a plurality of first collimating columns with a size of 50 nm, and grooves with a size of 25 nm are provided between adjacent first collimating columns; the shapes of the first collimating columns and the grooves are both cubic columns.

[0163] S4: forming a second dielectric layer on the top of the first collimating column and the bottom of the groove to obtain a collimating metasurface structure.

[0164] The material of the second dielectric layer is silicon, and the thickness is 80 nm.

[0165] S5: Adjust the angle at which the light emitted from the Micro-LED light-emitting structure enters the collimating metasurface structure, and use FDTD to simulate the collimating effect of the collimating metasurface structure to obtain Fig.15 The transmittance curve is shown.

[0166] from Fig.15 It can be seen that after the base layer is set on the light emitting surface side of the Micro-LED light emitting structure, the transmittance is close to 0 after the light beam with an incident angle greater than 20° enters the collimating metasurface structure, indicating that the collimating metasurface structure provided in this embodiment can filter out the light beam with an incident angle greater than 20° emitted from the Micro-LED light emitting structure for the Micro-LED light emitting structure with a wavelength of 532nm, thereby achieving a collimating effect.

[0167] Furthermore, if Fig.16 The figure shows a schematic diagram of the side electric field intensity obtained by simulating the collimating metasurface structure provided in Example 6. It can be seen from the figure that after the normal incident light enters the collimating metasurface structure, it will be concentrated in the second medium layer with a high refractive index to achieve energy concentration. The concentrated light waves have high energy and interfere and superpose with each other, thereby achieving high-intensity emission of light; while the oblique incident light enters the collimating metasurface structure at a certain angle and is reflected. Since the phase of the light beam changes each time it is reflected in the two equivalent medium layers, the resonance condition of the FP-like cavity structure is destroyed, making it impossible for the FP-like cavity structure to interfere and enhance the oblique incident light beam, resulting in the oblique incident light finally being emitted with low transmittance, indicating that the collimating metasurface structure provided in this embodiment can effectively improve the intensity and transmittance of the normal incident light, reduce the intensity and transmittance of the oblique incident light, and achieve the collimation effect of light.

[0168] In addition, by comparing Example 4 and Example 5, it can be seen that setting a substrate layer on the Micro-LED light-emitting structure to provide a smooth growth surface for the FP-like cavity structure can make the FP-like cavity structure more stable, thereby effectively reducing the influence of external environment such as vibration or temperature on the optical performance of the FP-like cavity, and further improving the collimation effect of the collimating metasurface on the light beam; by comparing Example 5 and Example 6, it can be seen that when gallium nitride is used as the material of the substrate layer, the collimating metasurface structure has a better light beam collimation effect.

[0169] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A Micro-LED with a collimated metasurface structure, characterized in that: include: Micro-LED light-emitting structure; A collimating metasurface structure, disposed on one side of the light-emitting surface of the Micro-LED light-emitting structure, for collimating and filtering the light emitted by the Micro-LED light-emitting structure so that the angle of the emitted light of the Micro-LED is less than a set angle; wherein the set angle is 10° to 40°; The collimating metasurface structure includes a first dielectric layer and a second dielectric layer, the first dielectric layer is disposed on the Micro-LED light-emitting structure, the first dielectric layer includes a plurality of first collimating columns, and a groove is provided between two adjacent first collimating columns; the second dielectric layer is disposed at the bottom of the groove and the top of the first collimating column; The refractive index of the first medium layer is smaller than the refractive index of the second medium layer; The second dielectric layer includes a second collimating column and a plurality of third collimating columns, the second collimating column is arranged around the first collimating column, and the third collimating column is arranged on the top of the first collimating column; Wherein, the thickness of the second collimating column is the same as the thickness of the third collimating column; The refractive index of the first collimating rod is smaller than the refractive index of the second collimating rod and / or the third collimating rod.

2. The Micro-LED with a collimated metasurface structure according to claim 1, characterized in that: The bottom of the groove contacts the light emitting surface of the Micro-LED light emitting structure.

3. The Micro-LED with a collimated metasurface structure according to claim 1, characterized in that: The first dielectric layer further includes a fourth collimating column, which is disposed between adjacent first collimating columns, and the top of the fourth collimating column contacts the bottom of the groove, and the thickness of the fourth collimating column is smaller than the thickness of the first collimating column.

4. The Micro-LED with a collimated metasurface structure according to claim 1, characterized in that: The collimating metasurface structure also includes a base layer, which is arranged on a side of the light emitting surface of the Micro-LED light emitting structure, and the first medium layer and the second medium layer are arranged on a side of the base layer away from the Micro-LED light emitting structure.

5. The Micro-LED with a collimated metasurface structure according to claim 4, characterized in that: The Micro-LED light-emitting structure comprises a stacked p-type layer, a multi-quantum well layer and an n-type layer, and the collimated metasurface structure is arranged on a side of the n-type layer away from the multi-quantum well layer; The thickness of the first dielectric layer is greater than or equal to the thickness of the second dielectric layer; and / or The first collimating column is in the shape of a circular column or a square column; and / or The size of the first collimating column is larger than the size of the groove; and / or The material of the first dielectric layer includes silicon oxide or photoresist; and / or The material of the second dielectric layer includes gallium nitride, titanium oxide, silicon nitride or silicon; and / or The material of the base layer includes silicon dioxide, gallium nitride or photoresist; and / or The wavelength of the emitted light of the Micro-LED is 532-632nm; and / or The transmittance of the output light of the Micro-LED light emitting structure is in the range of 0.8~1.

6. The Micro-LED with a collimated metasurface structure according to claim 1, characterized in that: When the wavelength of the emitted light of the Micro-LED is 632 nm, the thickness of the first dielectric layer is 100 nm to 386 nm; the thickness of the second dielectric layer is 6.2 nm to 208 nm; The diameter or side length of the first collimating column is 170nm~179nm; The size ratio of the first collimating column to the groove is 17:8-179:

38.

7. The Micro-LED with a collimated metasurface structure according to claim 1, characterized in that: When the wavelength of the emitted light of the Micro-LED is 532 nm, the thickness of the first dielectric layer is 229 nm to 400 nm; the thickness of the second dielectric layer is 80 nm to 227 nm; The diameter or side length of the first collimating column is 50nm~100nm; The size ratio of the first collimating column to the groove is 2:1-6:

1.

8. A method for preparing a Micro-LED having a collimated metasurface structure according to any one of claims 1 to 7, characterized in that: include: Providing a Micro-LED light-emitting structure, and forming a first dielectric layer on a light-emitting surface of the Micro-LED light-emitting structure; Etching the first dielectric layer to form a plurality of first collimating columns, wherein a groove is provided between two adjacent first collimating columns; forming a second dielectric layer at the bottom of the groove and the top of the first collimating column to obtain the collimating metasurface structure; Wherein, the refractive index of the first medium layer is smaller than the refractive index of the second medium layer.

9. The method for preparing a Micro-LED having a collimated metasurface structure according to claim 8, characterized in that: Forming a first dielectric layer on the light-emitting surface of the Micro-LED light-emitting structure, and etching the first dielectric layer to form a plurality of first collimating columns comprises: forming a base layer on the light emitting surface of the Micro-LED light emitting structure; Forming the first dielectric layer on a surface of the substrate layer away from the Micro-LED light-emitting structure; The first dielectric layer is exposed and developed by using a double-beam holographic exposure method to form the plurality of first collimating columns.

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