A micro light emitting diode with an annular light field regulation structure and a preparation method thereof

Abstract

The application discloses a micro light emitting diode with a ring-shaped light field regulation structure and a preparation method, and belongs to the technical field of semiconductor light emitting devices and micro-nano photonic structures. The micro light emitting diode comprises a light emitting mesa formed by a light emitting epitaxial layer stack, wherein the light emitting epitaxial layer stack comprises a p-type gallium nitride layer, a multi-quantum well active layer and an n-type gallium nitride layer arranged in sequence along a light emitting direction; the n-type gallium nitride layer comprises an n-type gallium nitride coupling layer and a ring-shaped positive ridge; the ring-shaped positive ridge is formed by local shallow etching of the n-type gallium nitride layer; the ring-shaped positive ridge is in a single closed aperiodic form; the ring-shaped positive ridge is integrally connected with the n-type gallium nitride coupling layer in a crystal state; the ring-shaped positive ridge divides the n-type gallium nitride coupling layer into an inner ring continuous n-type gallium nitride region and an outer ring continuous n-type gallium nitride region; and the ring-shaped positive ridge is higher than the inner ring continuous n-type gallium nitride region and the outer ring continuous n-type gallium nitride region. According to the application, the light field regulation structure is directly derived from the n-type gallium nitride layer of the device itself, and deposition of a hetero-medium is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor light-emitting devices and micro / nano photonic structures, specifically to a micro light-emitting diode with a ring-shaped light field modulation structure and its fabrication method. Background Technology

[0002] Micro-LEDs, characterized by self-emission, high brightness, fast response, and small pixel size, are important light sources for micro-displays, augmented reality, near-eye displays, and micro-projections. However, as pixel size decreases, the significant refractive index difference between gallium nitride and air, along with the optical constraints of the device's mesa boundaries and emission surfaces, affect light propagation and emission distribution within the device. Therefore, effectively controlling the emitted light to improve near-field distribution or spatial power distribution without significantly increasing pixel volume is a crucial direction for enhancing device performance.

[0003] In existing technologies, a common method for collimating and controlling the emitted light from LEDs is to mount lenses. This method typically involves fixing a pre-fabricated microlens or lens array onto the surface of the LED chip through alignment and mounting processes, outside the light-emitting surface. In addition, existing technologies also utilize ring or micro-ring structures to control the emitted light from Micro-LEDs.

[0004] Patent application CN102341740A discloses an invention patent for a light-emitting unit array, its manufacturing method, and a projection device. This invention forms micro-ring diffraction units on each Micro-LED and creates multiple concentric recessed regions on the Micro-LED surface by etching, thereby constructing a one-dimensional periodic micro-ring grating to collimate the emitted light. This solution demonstrates the technical requirement for micro-ring structures to participate in Micro-LED beam modulation.

[0005] The invention patent CN115084324A discloses a nanoring Micro-LED pixel, array, chip and fabrication method. The Micro-LED pixel is composed of multiple periodically arranged nanoring sub-pixels. Each nanoring sub-pixel includes an n-type gallium nitride upper part, a multicolor quantum well, a p-type layer and a current spreading layer, and a color conversion material is disposed on the inner wall of the ring. The structure etches the sub-pixel mesa containing the active layer into a ring.

[0006] Patent CN111453693A discloses an invention patent for a method of preparing nanorings. It uses patterned photoresist and oxide film to prepare an array of nanoscale ring protrusions and can transfer the pattern to a gallium nitride-based LED wafer. The focus is on the nanoring array and its mask transfer process.

[0007] Patent CN101878568A discloses an invention patent for a quantum ring laser and its manufacturing method. The invention discloses a quantum ring laser in which the ring mesa etching involves an n-type gallium nitride layer, an active layer, and a p-type gallium nitride layer, and exposes the side of the active layer.

[0008] Existing research has demonstrated two points: first, Micro-LEDs have a need for chip-level optical field manipulation; and second, ring-shaped, circumferentially propagating, or micro / nano-patterned structures can participate in optical field control. However, current technologies mostly focus on the fabrication of nanoring arrays, ring electrodes, or making the active region itself into a ring. Therefore, how to provide a chip-level ring-shaped optical field manipulation structure that does not require additional microlenses, does not require the construction of multi-unit periodic metasurfaces, and is compatible with existing gallium nitride fabrication routes, while maintaining the continuity of the multi-quantum-well active layer and the integrity of the device's main electrical structure, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0009] Therefore, the present invention provides a micro light-emitting diode with a ring-shaped light field modulation structure and a method for its fabrication, in order to solve the technical problems existing in the prior art.

[0010] To achieve the above objectives, the present invention provides the following technical solution: According to a first aspect of the present invention, a micro light-emitting diode with a ring-shaped light field modulation structure is provided, having a light-emitting mesa formed by a light-emitting epitaxial stack, wherein the light-emitting epitaxial stack includes a p-type gallium nitride layer, a multi-quantum-well active layer, and an n-type gallium nitride layer arranged sequentially along the light emission direction, the n-type gallium nitride layer including an n-type gallium nitride coupling layer and a ring-shaped positive ridge, the ring-shaped positive ridge being formed by local shallow etching of the n-type gallium nitride layer, the ring-shaped positive ridge having a single closed non-periodic shape, the ring-shaped positive ridge being integrally crystalline connected to the n-type gallium nitride coupling layer, the ring-shaped positive ridge dividing the n-type gallium nitride coupling layer into an inner continuous n-type gallium nitride region and an outer continuous n-type gallium nitride region, the ring-shaped positive ridge being higher than the inner continuous n-type gallium nitride region and the outer continuous n-type gallium nitride region.

[0011] Furthermore, it also includes a supporting substrate, a p-type electrode and bonding layer, a sidewall passivation layer and an n-type electrode. The supporting substrate is provided with a p-type electrode and bonding layer and a light-emitting epitaxial layer stack from bottom to top. The sidewall passivation layer covers the sidewall of the light-emitting epitaxial layer stack, and the n-type electrode is disposed on the light-emitting epitaxial layer stack.

[0012] Furthermore, the p-type electrode and bonding layer are located between the supporting substrate and the p-type gallium nitride layer and are electrically connected to the p-type gallium nitride layer, the n-type electrode is disposed on the plane of the n-type gallium nitride coupling layer and is electrically connected to the n-type gallium nitride coupling layer, and the n-type electrode is separated from the annular positive ridge.

[0013] Furthermore, the light-emitting platform is a circular light-emitting platform, and the annular ridge is a circular annular ridge that is concentrically arranged with the light-emitting platform.

[0014] Furthermore, the radial width w of the annular ridge is 300-500 nm, and the height h of the annular ridge is 250-450 nm.

[0015] Furthermore, the thickness t of the n-type gallium nitride coupling layer is 100-200 nm, and the outer ring spacing g of the continuous n-type gallium nitride region is 200-600 nm.

[0016] According to a second aspect of the present invention, a method for fabricating a micro light-emitting diode with a ring-shaped light field modulation structure is provided, for fabricating the micro light-emitting diode with a ring-shaped light field modulation structure as described in any one of the above claims, comprising the following steps: Step S1: An n-type gallium nitride layer, a multi-quantum-well active layer, and a p-type gallium nitride layer are epitaxially grown sequentially on a growth substrate to obtain an epitaxial wafer; Step S2: Deposit a p-type electrode and bonding layer on the p-type gallium nitride layer of the epitaxial wafer to obtain a wafer with a p-side structure; Step S3: Bond the p-side structure of the wafer to the support substrate. After bonding, a chip with a dual-substrate structure is obtained. Step S4: Flip the chip so that the growth substrate faces upward, and remove the growth substrate, or first thin and then remove the remaining growth substrate until the n-type gallium nitride layer exposes the light surface; Step S5: A mask with a corresponding shape to the annular positive ridge is covered on the n-type gallium nitride layer. The n-type gallium nitride layer that is not covered on the inner and outer sides of the mask is shallowly etched at the same time. After removing the mask, a light-emitting mesa with an annular positive ridge is obtained. Step S6: Deposit a sidewall passivation layer and an n-type electrode on the sidewall and top surface of the light-emitting platform, respectively, to obtain a micro light-emitting diode with a ring-shaped light field modulation structure.

[0017] Furthermore, during shallow etching in step S5, the etching depth is controlled so that the etching endpoint is located within the n-type gallium nitride layer and does not enter the multi-quantum well active layer.

[0018] Furthermore, after etching in step S5, the n-type gallium nitride layer is divided into an n-type gallium nitride coupling layer and an annular positive ridge, and the thickness t of the n-type gallium nitride coupling layer is 100-200 nm.

[0019] Furthermore, in step S6, the n-type electrode is deposited on the plane of the n-type gallium nitride coupling layer and is separated from the annular positive ridge.

[0020] The present invention has the following advantages: The micro diode provided in this application has a light-emitting mesa formed by a light-emitting epitaxial stack. The light-emitting epitaxial stack includes a p-type gallium nitride layer, a multi-quantum-well active layer, and an n-type gallium nitride layer sequentially arranged along the light-emitting direction. The n-type gallium nitride layer includes an n-type gallium nitride coupling layer and a ring-shaped positive ridge. The ring-shaped positive ridge is formed by local shallow etching of the n-type gallium nitride layer and has a single closed aperiodic shape. The ring-shaped positive ridge is integrally crystalline connected to the n-type gallium nitride coupling layer. The ring-shaped positive ridge divides the n-type gallium nitride coupling layer into an inner continuous n-type gallium nitride region and an outer continuous n-type gallium nitride region. The ring-shaped positive ridge is higher than both the inner and outer continuous n-type gallium nitride regions. This application provides a device structure that retains a single integral crystalline, closed, and aperiodic ring-shaped positive ridge on the continuous n-type gallium nitride coupling layer, while simultaneously retaining the continuous quantum-well active layer, the inner continuous n-type gallium nitride region, and the outer continuous n-type gallium nitride region.

[0021] The optical field modulation structure provided in this application is a ring-shaped positive ridge, which is directly derived from the n-type gallium nitride layer of the device itself, reducing the need for heterogeneous dielectric deposition, alignment, and mounting interfaces. The single non-periodic ring-shaped positive ridge provided in this application is not equivalent to multiple micro-ring diffraction unit arrays, and the structure definition is centralized. The multi-quantum well active layer provided in this application is not etched, and its luminous region remains continuous, which is different from circumferential lasers that make the active region itself into a ring. This avoids direct etching of the multi-quantum well active layer, which helps to reduce the risk of decreased luminous efficiency due to active layer etching damage. The ring-shaped positive ridge provided in this application is separated from the sidewall of the luminous mesa, allowing for separate design of the luminous mesa boundary and the ring-shaped positive ridge structure, while retaining a continuous n-type gallium nitride region outside the ring between them. This provides a certain design space for the luminous mesa size and the ring-shaped positive ridge parameters, which can be synergistically optimized by combining the mesa radius, the centerline radius of the ring-shaped positive ridge, the radial width, and the outer spacing. Attached Figure Description

[0022] To more clearly illustrate the embodiments of the present invention or the technical solutions in 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 merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0023] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0024] Figure 1 This is a schematic cross-sectional view of the miniature diode along the diameter of the mesa provided in Embodiment 1 of the present invention; Figure 2 This is a top view of the miniature diode provided in Embodiment 1 of the present invention; Figure 3 This is a flowchart illustrating the fabrication process of the micro diode provided in Embodiment 2 of the present invention; Figure 4 This is a comparison diagram of the broadband top normalized power proxy quantity of the looped structure and the loopless structure provided in Embodiment 3 of the present invention; Figure 5 This is a consistency comparison chart of two-level grids (30nm and 35nm) provided in Embodiment 4 of the present invention. Figure 6 This is a three-dimensional single-factor size tolerance verification diagram provided in Embodiment 5 of the present invention; In the picture: 1. Supporting substrate; 2. p-type electrode and bonding layer; 3. p-type gallium nitride layer; 4. Multiple quantum well active layer; 5. n-type gallium nitride coupling layer; 6. Ring-shaped positive ridge; 7. Sidewall passivation layer; 8. n-type electrode; 9. Continuous n-type gallium nitride region inside the ring; 10. Continuous n-type gallium nitride region outside the ring. Detailed Implementation

[0025] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0026] Example 1 like Figure 1-2As shown, a micro light-emitting diode with a ring-shaped light field modulation structure is provided. It has a light-emitting mesa formed by a light-emitting epitaxial stack. The light-emitting epitaxial stack includes a p-type gallium nitride layer 3, a multi-quantum-well active layer 4, and an n-type gallium nitride layer sequentially arranged along the light emission direction. The n-type gallium nitride layer includes an n-type gallium nitride coupling layer 5 and a ring-shaped positive ridge 6. The ring-shaped positive ridge 6 is formed by local shallow etching of the n-type gallium nitride layer and has a single closed aperiodic shape. The ring-shaped positive ridge 6 is integrally crystalline connected to the n-type gallium nitride coupling layer 5. The ring-shaped positive ridge 6 divides the n-type gallium nitride coupling layer 5 into an inner continuous n-type gallium nitride region 9 and an outer continuous n-type gallium nitride region 10. The ring-shaped positive ridge 6 is higher than the inner continuous n-type gallium nitride region 9 and the outer continuous n-type gallium nitride region 10. The light-emitting mesa is circular, and the ring-shaped positive ridge 6 is a circular ring-shaped positive ridge concentrically arranged with the light-emitting mesa.

[0027] The multi-quantum-well active layer 4 is formed by alternating multiple quantum well layers and barrier layers, and is a light-emitting active layer that generates radiative recombination after carrier injection; in this embodiment, an InGaN / GaN multi-quantum-well structure with alternating InGaN quantum well layers and GaN barrier layers is adopted.

[0028] The annular ridge 6 refers to the top surface of the annular region protruding in the light-emitting direction relative to the upper surface of its adjacent n-type gallium nitride regions, and the annular ridge 6 is not flush with its adjacent n-type gallium nitride regions. Integrated crystalline connection means that the annular ridge 6 and the underlying n-type gallium nitride coupling layer 5 are continuously formed from the same n-type gallium nitride layer, without any heterogeneous material interfaces created by separate deposition or bonding. Non-periodic means that multiple concentric repeating rings for forming diffraction gratings are not provided in a single pixel. The continuous n-type gallium nitride region 10 outside the ring separates the annular ridge 6 from the sidewall of the light-emitting mesa, distinguishing the annular ridge 6 from the mesa edge itself. The annular ridge 6 is not a metal electrode, an annular modified region formed by ion implantation, or a separately mounted dielectric optical element. The annular ridge 6 is configured to couple with at least a portion of the optical field in the n-type gallium nitride coupling layer 5 to change the near-field distribution or spatial distribution of optical power on the emission side of the micro-LED.

[0029] It also includes a supporting substrate 1, a p-type electrode and bonding layer 2, a sidewall passivation layer 7, and an n-type electrode 8. The supporting substrate 1 is provided with, from bottom to top, a p-type electrode and bonding layer 2 and a light-emitting epitaxial layer stack. The sidewall passivation layer 7 covers the sidewalls of the light-emitting epitaxial layer stack, and the n-type electrode 8 is disposed on the light-emitting epitaxial layer stack. The p-type electrode and bonding layer 2 is located between the supporting substrate 1 and the p-type gallium nitride layer 3 and is electrically connected to the p-type gallium nitride layer 3. The n-type electrode 8 is disposed on the plane of the n-type gallium nitride coupling layer 5 and is electrically connected to the n-type gallium nitride coupling layer 5, and the n-type electrode 8 is separated from the annular ridge 6. The n-type electrode 8 can also be disposed in other areas that satisfy the electrical connection but do not cover the annular ridge 6.

[0030] The difference between the outer radius and the inner radius of the annular ridge 6 is defined as the radial width w, which is 300–500 nm. The vertical distance between the top surface of the annular ridge 6 and the upper surface of the n-type gallium nitride coupling layer 5 is defined as the height h of the annular ridge 6, which is 250–450 nm. The vertical distance between the light-emitting side surface of the multi-quantum-well active layer 4 and the upper surface of the n-type gallium nitride coupling layer 5 is defined as the thickness t of the n-type gallium nitride coupling layer 5, which is 100–200 nm. The shortest distance measured radially along the circular light-emitting platform between the outer edge of the annular ridge 6 and the outer wall of the light-emitting platform is defined as the outer ring spacing g of the continuous n-type gallium nitride region 10, which is 200–600 nm.

[0031] Specifically, in this embodiment, the radius Rm of the circular light-emitting mesa is 3.5 μm, and the radius Rc of the centerline of the annular ridge 6 is 3.0 μm. The centerline radius Rc is the distance from the center of the mesa to the midpoint of the radial width of the annular ridge 6, excluding the radial width w itself. The radial width w of the annular ridge 6 is 400 nm, the inner radius of the annular ridge 6 is Rc - w / 2 = 2.8 μm, the outer radius is Rc + w / 2 = 3.2 μm, and the outer spacing g is Rm - (Rc + w / 2) = 300 nm. The height h of the annular ridge 6 is 350 nm, and the thickness t of the n-type gallium nitride coupling layer 5 is 150 nm. Therefore, the total thickness t + h of the n-type gallium nitride layer at the location of the annular ridge 6 is 500 nm. The total thickness of the multi-quantum-well active layer 4 is set to 60 nm in the simulation equivalent model and is continuous across the entire lateral range of the light-emitting mesa.

[0032] The annular positive ridge 6 and its adjacent continuous n-type gallium nitride coupling layer 5 can redistribute part of the optical field near the annular region. The physical mechanism may involve circumferential propagation, interference, and circumferential constraint similar to the whispering corridor pattern.

[0033] Example 2 A method for fabricating a micro light-emitting diode with a ring-shaped light field modulation structure, comprising the following steps: Step S1: An n-type gallium nitride layer, a multi-quantum-well active layer, and a p-type gallium nitride layer are epitaxially grown sequentially on a growth substrate to obtain an epitaxial wafer; Step S2: Deposit a p-type electrode and bonding layer on the p-type gallium nitride layer of the epitaxial wafer to obtain a wafer with a p-side structure; Step S3: Bond the p-side structure of the wafer to the support substrate. After bonding, a chip with a dual-substrate structure is obtained. Step S4: Flip the chip so that the growth substrate is facing up, and remove the growth substrate, or thin it first and then remove the remaining growth substrate until the n-type gallium nitride layer exposes the light surface. Step S5: A mask with a corresponding shape of a ring-shaped positive ridge is covered on the n-type gallium nitride layer. The n-type gallium nitride layer that is not covered on the inner and outer sides of the mask is shallowly etched at the same time. After removing the mask, a light-emitting mesa with a ring-shaped positive ridge is obtained. Step S6: Deposit a sidewall passivation layer and an n-type electrode on the sidewall and top surface of the light-emitting platform, respectively, to obtain a micro light-emitting diode with a ring-shaped light field modulation structure.

[0034] During shallow etching in step S5, the etching depth is controlled so that the etching endpoint is located within the n-type gallium nitride layer and does not enter the multi-quantum well active layer.

[0035] After etching in step S5, the n-type gallium nitride layer is divided into an n-type gallium nitride coupling layer and a ring-shaped positive ridge. The thickness t of the n-type gallium nitride coupling layer is 100-200 nm.

[0036] In step S6, the n-type electrode is deposited on the plane of the n-type gallium nitride coupling layer and is separated from the annular positive ridge.

[0037] like Figure 3 The image shown is a cross-sectional view obtained along the diameter of the light-emitting mesa during the diode fabrication process. Figure 3 (a) is a structural diagram of the support substrate, p-type electrode and bonding layer, p-type gallium nitride layer, multi-quantum well active layer and n-type gallium nitride layer left after the growth substrate is removed. The n-type gallium nitride layer exposes the light surface. Figure 3 (b) To form a hard mask or photoresist mask on the exposed n-type gallium nitride (GaN) layer surface, the mask covers a single closed, non-periodic annular region with a ring-shaped positive ridge. Two rectangular cross-sections on the left and right sides of the GaN layer are cross-sectional views of the mask; they are continuous in the top view and constitute the same mask. The middle region of the two rectangular cross-sections is the uncovered area within the ring, and the outer regions of the two rectangular cross-sections are the uncovered area outside the ring. Inductively coupled plasma etching (ICP-CPE) or other anisotropic etching methods suitable for GaN are used to simultaneously perform shallow etching on the two uncovered areas of the GaN layer, while preserving the annular region covered by the mask. The etching depth is controlled so that the etching endpoint is located within the GaN layer and retains a 100–200 nm thick GaN coupling layer, without entering the multi-quantum-well active layer. Figure 3 (c) After etching, the mask is removed, and the mask-covered area is retained as a ring-shaped positive ridge higher than the adjacent inner and outer surfaces; the inner etched area forms a continuous n-type gallium nitride region inside the ring, and the outer etched area forms a continuous n-type gallium nitride region outside the ring. The three are still connected by the continuous n-type gallium nitride coupling layer below. Figure 3 (d) To deposit an n-type electrode on the light-emitting platform forming the annular positive ridge, a sidewall passivation layer is deposited on the sidewall of the platform. The n-type electrode is separated from the annular positive ridge in a planar position to reduce the occlusion of the annular optical region.

[0038] The key to this process is not adding an external material ring to the Micro-LED surface, but rather selectively thinning the original n-type gallium nitride layer to create a ring-shaped ridge from the unetched single closed ring region. The etched ring-shaped ridges are still interconnected through the continuous n-type gallium nitride coupling layer beneath them, which is not etched through. This maintains the material and electrical continuity of the n-type gallium nitride layer and avoids etching the multi-quantum-well active layer into a ring.

[0039] Example 3 A three-dimensional finite-difference time-domain (FDTD) method was used to establish a comparison model with and without a ring. The baseline structure adopted the dimensions described in Example 1. In the equivalent refractive index model, the refractive indices of the p-type gallium nitride layer, the multi-quantum-well active layer, the n-type gallium nitride layer, the supporting substrate, and the device background medium were set to 2.42, 2.55, 2.45, 1.78, and 1.00, respectively. The simulation region had a lateral dimension of 8.0 μm × 8.0 μm, and all boundaries were perfectly matched layer boundaries. The multi-quantum-well active layer and the ring region used a local mesh with a lateral dimension of 35 nm and a vertical dimension of 15 nm, and a broadband model with a lateral dimension of 30 nm and a vertical dimension of 15 nm was used for consistent recalculation. The light source was an electric dipole located within the multi-quantum-well active layer and tangentially polarized along the ring; the broadband calculation range was 442–458 nm. The top power monitoring surface was located 0.72 μm above the device and had a size of 7.2 μm × 7.2 μm. The top normalized power proxy is the normalized amount of the transmitted power of the monitoring surface relative to the power of the light source. All ring-shaped structures and the ringless control models use the same boundary conditions, light source, monitor position, simulation time, and normalization method, only changing whether or not a ring-shaped positive ridge is set.

[0040] Using a local mesh with a horizontal dimension of 35 nm and a vertical dimension of 15 nm, single-frequency baseline calculations were performed at a wavelength of 450.8 nm. The results showed that the ratio of the normalized power surrogate at the top of the ringed structure to the non-ringed control structure was 1.550, the energy share ratio of the ringed region was 1.157, and the ratio of the local maximum field value was 0.717. These results indicate that the change caused by the ringed positive ridge represents a redistribution of the spatial optical field, rather than a simultaneous enhancement of all local field quantities. Figure 4 As shown, when recalculating the broadband with and without loops using a mesh broadband model with a horizontal dimension of 30 nm and a vertical dimension of 15 nm, the ratio of the top normalized power surrogate at a wavelength of 450.8 nm is 1.487, verifying the above conclusion. Based on this result, subsequent broadband and tolerance verifications use the top power surrogate as a comparison indicator, and do not consider the local maximum field value as an achieved beneficial effect.

[0041] Example 4 Employing grid consistency verification, such as Figure 5As shown, consistency comparisons were performed using two mesh levels: 30nm and 35nm. A three-dimensional broadband comparison was conducted using 81 wavelength points within the wavelength range of 442–458nm. With the 35nm mesh, the cyclic / acyclic power surrogate ratio for all 81 wavelength points was no less than the preset threshold of 1.20, and the cyclic / acyclic power surrogate ratio at wavelength 450.8nm was 1.535. When recalculated using the 30nm mesh, the cyclic / acyclic power surrogate ratio for all 81 wavelength points was still no less than the preset threshold of 1.20, and the cyclic / acyclic power surrogate ratio at wavelength 450.8nm was 1.487, a change of -3.18% compared to the 35nm mesh. These results indicate that the conclusions are consistent under the given model, wavelength band, and both mesh conditions.

[0042] In this embodiment, the “top normalized power proxy” is a comparison index under the specified monitoring plane, normalization method, and simulation boundary, and is not equivalent to the external quantum efficiency, wall insertion efficiency, or total light output efficiency of the integral hemisphere of the complete device.

[0043] Example 5 Three-dimensional single-factor dimensional tolerance verification was adopted, such as Figure 6 As shown, at a wavelength of 450.8 nm, with a reference structure, the radial width w, height h, thickness t of the n-type gallium nitride coupling layer, and outer ring spacing g of the annular ridge were varied. Specifically, when changing the radial width w, the centerline radius Rc of the annular ridge was adjusted accordingly to maintain the outer ring spacing g at 300 nm; when changing the outer ring spacing g, the centerline radius Rc was adjusted accordingly to obtain the corresponding outer ring spacing; when changing the height h or thickness t, the remaining geometric parameters adopted the reference values ​​of the reference structure. In all tolerance cases, the radial position of the electric dipole was fixed at 3.0 μm from the center of the emitting mesa. The measured top power surcharge ratios with and without rings were as follows: 1.212 for w=300nm, 1.567 for w=500nm; 1.492 for h=250nm, 1.905 for h=450nm; 2.034 for t=100nm, 1.795 for t=200nm; 1.492 for g=200nm, 1.392 for g=400nm, 1.204 for g=500nm, and 1.476 for g=600nm.

[0044] The results show that the ratios for all cases within the validated range are higher than the preset threshold of 1.10. In particular, the cases with an outer ring spacing g of 500 nm and 600 nm still maintain results greater than 1.10.

[0045] The above simulations demonstrate that the structure exhibits calculable optical field modulation and a certain geometric tolerance. Actual devices can be further optimized based on emission wavelength, mesa size, material refractive index, contact layout, and fabrication capabilities, and further far-field, spectral, electrical, thermal, and reliability tests can be conducted.

[0046] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A miniature light-emitting diode with a ring-shaped light field modulation structure, characterized in that, The device has a light-emitting mesa formed by a light-emitting epitaxial stack, wherein the light-emitting epitaxial stack includes a p-type gallium nitride layer, a multi-quantum-well active layer, and an n-type gallium nitride layer arranged sequentially along the light emission direction. The n-type gallium nitride layer includes an n-type gallium nitride coupling layer and an annular positive ridge. The annular positive ridge is formed by local shallow etching of the n-type gallium nitride layer. The annular positive ridge has a single closed non-periodic shape. The annular positive ridge is integrally crystalline connected to the n-type gallium nitride coupling layer. The annular positive ridge divides the n-type gallium nitride coupling layer into an inner continuous n-type gallium nitride region and an outer continuous n-type gallium nitride region. The annular positive ridge is higher than the inner continuous n-type gallium nitride region and the outer continuous n-type gallium nitride region.

2. The micro light-emitting diode with a ring-shaped light field modulation structure as described in claim 1, characterized in that, It also includes a supporting substrate, a p-type electrode and bonding layer, a sidewall passivation layer and an n-type electrode. The supporting substrate is provided with a p-type electrode and bonding layer and a light-emitting epitaxial layer stack from bottom to top. The sidewall passivation layer covers the sidewall of the light-emitting epitaxial layer stack, and the n-type electrode is disposed on the light-emitting epitaxial layer stack.

3. The micro light-emitting diode with a ring-shaped light field modulation structure as described in claim 2, characterized in that, The p-type electrode and bonding layer are located between the supporting substrate and the p-type gallium nitride layer and are electrically connected to the p-type gallium nitride layer. The n-type electrode is disposed on the plane of the n-type gallium nitride coupling layer and is electrically connected to the n-type gallium nitride coupling layer. The n-type electrode is separated from the annular positive ridge.

4. The micro light-emitting diode with a ring-shaped light field modulation structure as described in claim 1, characterized in that, The light-emitting platform is a circular light-emitting platform, and the annular ridge is a circular annular ridge that is concentrically arranged with the light-emitting platform.

5. The micro light-emitting diode with a ring-shaped light field modulation structure as described in claim 1, characterized in that, The radial width w of the annular ridge is 300-500 nm, and the height h of the annular ridge is 250-450 nm.

6. The micro light-emitting diode with a ring-shaped light field modulation structure as described in claim 1, characterized in that, The thickness t of the n-type gallium nitride coupling layer is 100-200 nm, and the outer ring spacing g of the continuous n-type gallium nitride region is 200-600 nm.

7. A method for fabricating a micro light-emitting diode with a ring-shaped light field modulation structure, used to fabricate a micro light-emitting diode with a ring-shaped light field modulation structure as described in any one of claims 1-6, characterized in that, Includes the following steps: Step S1: An n-type gallium nitride layer, a multi-quantum-well active layer, and a p-type gallium nitride layer are epitaxially grown sequentially on a growth substrate to obtain an epitaxial wafer; Step S2: Deposit a p-type electrode and bonding layer on the p-type gallium nitride layer of the epitaxial wafer to obtain a wafer with a p-side structure; Step S3: Bond the p-side structure of the wafer to the support substrate. After bonding, a chip with a dual-substrate structure is obtained. Step S4: Flip the chip so that the growth substrate faces upward, and remove the growth substrate, or first thin and then remove the remaining growth substrate until the n-type gallium nitride layer exposes the light surface; Step S5: A mask with a corresponding shape to the annular positive ridge is covered on the n-type gallium nitride layer. The n-type gallium nitride layer that is not covered on the inner and outer sides of the mask is shallowly etched at the same time. After removing the mask, a light-emitting mesa with an annular positive ridge is obtained. Step S6: Deposit a sidewall passivation layer and an n-type electrode on the sidewall and top surface of the light-emitting platform, respectively, to obtain a micro light-emitting diode with a ring-shaped light field modulation structure.

8. The method for fabricating a micro light-emitting diode with a ring-shaped light field modulation structure as described in claim 7, characterized in that, During shallow etching in step S5, the etching depth is controlled so that the etching endpoint is located within the n-type gallium nitride layer and does not enter the multi-quantum well active layer.

9. The method for fabricating a micro light-emitting diode with a ring-shaped light field modulation structure as described in claim 7, characterized in that, After being etched in step S5, the n-type gallium nitride layer is divided into an n-type gallium nitride coupling layer and an annular positive ridge. The thickness t of the n-type gallium nitride coupling layer is 100-200 nm.

10. The method for fabricating a micro light-emitting diode with a ring-shaped light field modulation structure as described in claim 9, characterized in that, In step S6, the n-type electrode is deposited on the plane of the n-type gallium nitride coupling layer and is separated from the annular positive ridge.

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