Full-color display device and preparation method thereof

Abstract

The invention discloses a full-color display device and a preparation method thereof.The full-color display device comprises a substrate and a periodic pixel unit array located on the substrate, each pixel unit comprises at least three sub-pixel areas, and microstructures corresponding to different dominant crystal faces are formed in the different sub-pixel areas; micro-LED structures are formed on the microstructures of the different dominant crystal faces in an epitaxy mode, so that different sub-pixel areas can emit light of different wavelengths respectively, and therefore full-color light emitting is achieved. According to the invention, crystal face engineering is carried out on the surface of the substrate, so that microstructures corresponding to different dominant crystal faces are formed in different sub-pixel areas, and the different sub-pixel areas can respectively emit light with different wavelengths by utilizing the natural difference of the different crystal faces on In component merging efficiency, so that full-color light emission is realized, the wavelength controllability is good, and the light emitting efficiency is high. The high-difficulty mass transfer process is avoided, the manufacturing cost is greatly reduced, and the production efficiency and the yield are improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic device technology, specifically relating to a full-color display device and its preparation method. Background Technology

[0002] Micro-LED is considered the core of next-generation display technology due to its advantages such as high brightness, high efficiency, and long lifespan. However, achieving full-color display is one of the major technical challenges currently facing Micro-LED. The mainstream technical approaches currently include: 1) Mass transfer technology: Red, green, and blue Micro-LED chips are fabricated separately, and then precisely bonded to the driving substrate using mass transfer technology. This method is extremely technically challenging, with yield, cost, and efficiency being major bottlenecks. 2) Quantum dot color conversion: A blue or ultraviolet Micro-LED array is fabricated, and then a patterned quantum dot color conversion layer is used to convert part of the light into red and green light. This method suffers from problems such as quantum dot photostability, material aging, and optical crosstalk. 3) Single epitaxial layer + local color adjustment: The properties of the active region are changed on a single epitaxial wafer by means of ion implantation or selective thermal annealing. However, this method has complex process control and may damage the material, affecting the luminescence efficiency. Summary of the Invention

[0003] To address the problems in the prior art, the present invention aims to provide a full-color display device and its preparation method.

[0004] To achieve the above objectives and technical effects, the technical solution adopted by this invention is as follows: A full-color display device includes a substrate and a periodic pixel unit array located on the substrate. Each pixel unit includes at least three sub-pixel regions. Microstructures corresponding to different dominant crystal planes are formed in different sub-pixel regions. Micro-LED structures are epitaxially formed on the microstructures of the different dominant crystal planes, so that different sub-pixel regions can emit light of different wavelengths respectively, thereby realizing full-color light emission.

[0005] Furthermore, the three sub-pixel regions mentioned above include a red light sub-pixel region, a green light sub-pixel region, and a blue light sub-pixel region; The In content in the Micro-LED structures corresponding to the aforementioned red, green, and blue photonic pixel regions differs.

[0006] Furthermore, the In content in the Micro-LED structure corresponding to the red photonic pixel region is greater than the In content in the Micro-LED structure corresponding to the green photonic pixel region, which in turn is greater than the In content in the Micro-LED structure corresponding to the blue photonic pixel region.

[0007] Furthermore, the dominant crystal plane of the microstructure in the aforementioned red photonic pixel region is a semi-polar crystal plane; the dominant crystal plane of the microstructure in the aforementioned green photonic pixel region is a high-index crystal plane; and the dominant crystal plane of the microstructure in the aforementioned blue photonic pixel region is a c-plane.

[0008] Furthermore, the crystal plane index corresponding to the above-mentioned semi-polar crystal plane is {11-21} or {10-11}; the crystal plane index corresponding to the above-mentioned high-index crystal plane is {11-22}; and the crystal plane index corresponding to the above-mentioned c-plane is {0001}.

[0009] Furthermore, the aforementioned Micro-LED structure is obtained through a single epitaxial growth process on the aforementioned substrate, and this single epitaxial growth process is fabricated without differentiation for different sub-pixel regions.

[0010] Furthermore, the aforementioned Micro-LED structure includes an n-type GaN layer, a multi-quantum-well active layer, and a p-type GaN layer stacked sequentially, wherein the multi-quantum-well active layers in different sub-pixel regions have different In compositions.

[0011] Furthermore, the aforementioned substrate is a gallium nitride single crystal substrate.

[0012] Furthermore, the aforementioned microstructures include gallium nitride microstructures formed in different sub-pixel regions.

[0013] Furthermore, each pixel unit is provided with an n-type electrode and a p-type electrode; an insulating protective layer is provided at the intervals between each pixel unit and between each sub-pixel region within each pixel unit, as well as on the upper surface, exposing the corresponding n-type electrode and p-type electrode.

[0014] This invention also discloses a method for fabricating a full-color display device, comprising the following steps: S1. Prepare a substrate and define a periodic pixel unit array on its surface, each pixel unit including at least three sub-pixel regions; then open windows in each sub-pixel region to form growth windows; S2. Lateral epitaxial growth is performed within the growth window. By adjusting the epitaxial growth conditions in each sub-pixel region, microstructures with different dominant crystal planes are formed in different sub-pixel regions. S3. A Micro-LED structure is epitaxially grown on a substrate containing microstructures in one step. Based on the difference in In incorporation efficiency during the epitaxial growth of Micro-LED structures on microstructures with different dominant crystal planes, the Micro-LED structures formed in each sub-pixel region have different emission wavelengths; wherein, the above-mentioned one-step epitaxy is a non-differentiated preparation for different sub-pixel regions.

[0015] Furthermore, in step S1, the substrate is a gallium nitride single crystal substrate. A periodic pixel unit array is defined on the surface of the substrate by a patterned photoresist layer or mask material layer. Windows are opened in each sub-pixel region by photolithography and etching processes to form growth windows for selective lateral epitaxy.

[0016] Furthermore, the aforementioned growth windows can be strip-shaped, cross-shaped, or dot-matrix-shaped.

[0017] Furthermore, in step S2, gallium nitride-based materials are laterally epitaxially grown within growth windows corresponding to different sub-pixel regions using metal-organic chemical vapor deposition technology to obtain gallium nitride microstructures with different dominant crystal planes.

[0018] Furthermore, in step S2, by adjusting the epitaxial growth conditions within each sub-pixel region, microstructures with corresponding dominant crystal planes are formed in different sub-pixel regions, including: By controlling the epitaxial growth conditions of the red photonic pixel region, a first microstructure with a semi-polar crystal plane as the dominant crystal plane was obtained; By controlling the epitaxial growth conditions of the green photonic pixel region, a second microstructure with a high-index crystal plane as the dominant crystal plane was obtained; By controlling the epitaxial growth conditions of the blue photonic pixel region, a third microstructure with the c-plane as the dominant crystal plane was obtained.

[0019] Furthermore, the crystal plane index corresponding to the above-mentioned semi-polar crystal plane is {11-21} or {10-11}; the crystal plane index corresponding to the above-mentioned high-index crystal plane is {11-22}; and the crystal plane index corresponding to the above-mentioned c-plane is {0001}.

[0020] Furthermore, the In content in the Micro-LED structures corresponding to the red, green, and blue photonic pixel regions differs, with the In content in the red photonic pixel region being greater than that in the green photonic pixel region, which in turn is greater than that in the blue photonic pixel region.

[0021] Furthermore, in step S3, the epitaxial growth of the Micro-LED structure on the substrate containing the microstructure in a single step includes the following steps: An n-type GaN layer, a multi-quantum-well active layer, and a p-type GaN layer are epitaxially grown sequentially on a substrate containing microstructures. The multi-quantum-well active layers in different sub-pixel regions have different In compositions.

[0022] Furthermore, the preparation method further includes step S4: An n-type electrode, a p-type electrode, and an insulating protective layer are formed on the aforementioned Micro-LED structure. The insulating protective layer is located at the intervals between each pixel unit and between each sub-pixel region within each pixel unit, as well as on the upper surface, and exposes the upper surfaces of the corresponding n-type electrode and p-type electrode.

[0023] Compared with the prior art, the beneficial effects of the technical solutions provided by the embodiments of the present invention include at least some or all of the following: (1) The present invention forms a periodic pixel unit array by performing crystal plane engineering at the substrate level. Each pixel unit includes at least three sub-pixel regions. Microstructures corresponding to different dominant crystal planes are formed in different sub-pixel regions. Micro-LED structures are epitaxially formed on the microstructures of different dominant crystal planes. By utilizing the natural difference in the incorporation efficiency of In components by different crystal planes, different sub-pixel regions can emit light of different wavelengths, thereby achieving full-color light emission. The wavelength is well controllable, the method is direct, reliable, and has good repeatability. (2) The present invention enables different sub-pixel regions to be formed on the same substrate at one time, which fundamentally avoids the difficult mass transfer process, greatly reduces manufacturing costs, and improves production efficiency and yield. (3) The active layer of all light-emitting regions in this invention is obtained by high-quality epitaxial growth, which avoids the problems of material stability and light extraction efficiency in quantum dot color conversion technology; (4) The core process used in this invention is based on mature MOCVD and photolithography technology, which is compatible with existing semiconductor manufacturing processes and is easy to scale up. Attached Figure Description

[0024] Figure 1A A top view of the substrate prepared in the fabrication method of a full-color display device according to an embodiment of the present invention; Figure 1B A cross-sectional view of the substrate prepared in the fabrication method of a full-color display device according to an embodiment of the present invention; Figure 2A This is a top view of step S1 of an embodiment of the present invention, in which a periodic pixel unit array is defined on the substrate surface; wherein R, G, and B correspond to the red sub-pixel region, the green sub-pixel region, and the blue sub-pixel region, respectively, and three of them form a pixel unit, and the pixel units are periodically arranged to form a pixel unit array. Figure 2B A substrate with a periodic pixel unit array defined on its surface in an embodiment of the present invention is along... Figure 2A The cross-sectional view along the A-A1 direction in the image shows that the dashed lines represent the boundaries of the patterned regions corresponding to the patterned photoresist layer or mask material layer. Figure 2C A substrate with a periodic pixel unit array defined on its surface in an embodiment of the present invention is along... Figure 2A A cross-sectional view along the C-C1 direction; Figure 3 This is a schematic diagram of the growth window structure in step S1 of an embodiment of the present invention; wherein, (a) is a top view of the growth window, (b) is a cross-sectional view along the A-A1 direction in the top view, and (c) is a cross-sectional view along the C-C1 direction in the top view. Figure 4 This is a schematic diagram of crystal plane control in step S2 of an embodiment of the present invention; wherein, (a) is a top view of crystal plane control in the growth window, (b) is a cross-sectional view along the A-A1 direction of the top view, and (c) is a cross-sectional view along the C-C1 direction of the top view. Figure 5 This is a schematic diagram of the first microstructure, second microstructure and third microstructure obtained by crystal plane control growth in step S2 of an embodiment of the present invention, where the first growth window corresponding to the red photonic pixel region, the second growth window corresponding to the green photonic pixel region and the third growth window corresponding to the blue photonic pixel region are respectively performed. Figure 6A This is a top view of the growth of the Micro-LED structure in step S3 of an embodiment of the present invention; Figure 6B In one embodiment of the present invention, after growing the Micro-LED structure along... Figure 6A Cross-sectional view along the A-A1 direction; Figure 6C In one embodiment of the present invention, after growing the Micro-LED structure along... Figure 6A Cross-sectional view along the C-C1 direction; Figure 7A This is a schematic diagram of step S4 of an embodiment of the present invention, showing the fabrication of the electrode and the insulating passivation layer. Figure 7B In one embodiment of the present invention, after the electrode and insulating passivation layer are fabricated, along... Figure 7A A cross-sectional view along the A-A1 direction; Figure 7C In one embodiment of the present invention, after the electrode and insulating passivation layer are fabricated, along... Figure 7A A cross-sectional view along the C-C1 direction. Detailed Implementation

[0025] The present invention will now be described in detail so that its advantages and features can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0026] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0027] As shown in Figure 1- Figure 7C As shown, this embodiment of the invention discloses a full-color display device, including a substrate 1 and a periodic pixel unit array located on the substrate 1. Each pixel unit 10 includes at least three sub-pixel regions. Microstructures corresponding to different dominant crystal planes are formed in different sub-pixel regions. Micro-LED structures are epitaxially formed on the microstructures of different dominant crystal planes, so that different sub-pixel regions can emit light of different wavelengths respectively, thereby realizing full-color light emission.

[0028] In some embodiments, substrate 1 is a gallium nitride (GaN) single crystal substrate.

[0029] In some implementations, a periodic pixel unit array is defined on the surface of the substrate 1 by a patterned photoresist layer or mask material layer 2.

[0030] In some implementations, refer to Figures 2A-2C , Figure 3 (a)~(c) Figure 4 (a)~(c) and Figure 5 As shown, the three sub-pixel regions include a red (R) sub-pixel region, a green (G) sub-pixel region, and a blue (B) sub-pixel region. A first microstructure 111 is formed within a first growth window 101 in the red sub-pixel region, a second microstructure 112 is formed within a second growth window 102 in the green sub-pixel region, and a third microstructure 113 is formed within a third growth window 103 in the blue sub-pixel region. The dominant crystal plane of the first microstructure 111 is a semi-polar crystal plane; the dominant crystal plane of the second microstructure 112 is a high-index crystal plane; and the dominant crystal plane of the third microstructure 113 is a c-plane.

[0031] In some embodiments, the microstructure includes gallium nitride (GaN) microstructures formed in different sub-pixel regions. By setting a GaN single-crystal substrate, GaN microstructures with different dominant crystal planes are formed in sub-pixel regions of different colors on the GaN single-crystal substrate. Subsequently, a Micro-LED structure can be epitaxially grown on the substrate with GaN microstructures with different dominant crystal planes under the same growth conditions. This not only ensures the difference in the incorporation efficiency of the In component in different sub-pixel regions of the subsequently epitaxially grown Micro-LED structure, realizing the corresponding red, green, or blue light emission of red, green, or blue light in red, green, and blue sub-pixel regions, but also the homogeneous epitaxy has better lattice matching, resulting in a lower dislocation density in the one-time epitaxial Micro-LED structure, improving the growth quality of the epitaxial layer, thereby achieving high-efficiency and high-quality fabrication of full-color display devices without the need for mass transfer or wavelength conversion.

[0032] In some implementations, the In content in the Micro-LED structure corresponding to the red photonic pixel region, green photonic pixel region, and blue photonic pixel region is different.

[0033] In some specific implementations, the In content in the Micro-LED structure corresponding to the red photonic pixel region is greater than the In content in the Micro-LED structure corresponding to the green photonic pixel region, which in turn is greater than the In content in the Micro-LED structure corresponding to the blue photonic pixel region.

[0034] In some embodiments, the present invention sets the crystal plane index of the dominant semi-polar crystal plane corresponding to the red photonic pixel region to {11-21} or {10-11}, the crystal plane index of the dominant high-index crystal plane corresponding to the green photonic pixel region to {11-22}, and the crystal plane index of the c-plane to {0001}. Under the same conditions, when fabricating various epitaxial layers in a Micro-LED structure, among the three crystal plane orientations, the semi-polar {11-21} / {10-11} plane has the lowest interface barrier potential energy, followed by the high-index {11-22} plane, and the c-plane {0001} plane has the highest. Correspondingly, the In component (e.g., the In component in the multi-quantum-well active layer 4) diffuses more easily to the {11-21} or {10-11} plane and is less likely to accumulate on the {0001} plane (requiring more diffusion). The concentration of In components in the {11-22} plane is between that in the {11-21} / {10-11} plane and the {0001} plane, thus spontaneously generating structures with spatially distributed concentration differences. This means that the In component concentration varies in different sub-pixel regions within a Micro-LED structure grown epitaxially under the same process conditions due to differences in microstructure guidance. Furthermore, based on the microstructure's structural pattern, distribution density, and distribution state (uniformity), it is possible to promote refined and differentiated control of the distribution concentration and emission wavelength (specifically, whether the wavelength belongs to the red light band (e.g., 620nm~760nm), green light band (e.g., 490nm~580nm), or blue light band (e.g., 400nm~460nm), with the specific wavelength capable of fine-tuning within the band) in full-color display devices. For example, it is possible to control 620nm red light, 530nm green light, and 460nm blue light.

[0035] Understandably, in Figure 5 Although the examples of microstructures include cones and prisms, other types of regular or even irregular microstructures (such as cylinders, frustums, prisms, pyramids, etc.) can also be used. Any differentiated microstructures that produce differences in In diffusion efficiency within pixel regions corresponding to different luminous colors are considered cases not listed in the embodiments of this invention.

[0036] In some embodiments, the Micro-LED structure is obtained by epitaxy on substrate 1 in a single step, wherein the single epitaxy is fabricated without differentiation for different sub-pixel regions.

[0037] In some implementations, refer to Figures 6A-6CAs shown, the Micro-LED structure includes an n-type GaN layer 3, a multi-quantum-well active layer 4, and a p-type GaN layer 5 stacked sequentially. The multi-quantum-well active layers in different sub-pixel regions have different In compositions. The multi-quantum-well active layer 4 is guided to have different In composition incorporation efficiencies by controlling parameters such as temperature, the ratio of nitrogen to gallium source (V / III ratio), and pressure. The detailed principle is as follows: a) Reaction chamber pressure Low / atmospheric pressure: Facilitates lateral diffusion of reactants (such as NH3 and Ga sources), giving them a greater chance to reach the suspended lateral growth front. This promotes lateral growth and facilitates the formation of trapezoidal structures with smooth {11-22} slopes. The quality of the lateral epitaxial region is higher. High pressure: gas phase diffusion is suppressed, reactants are consumed more in the vertical direction, lateral growth is suppressed and vertical growth is promoted, and it is easy to form a mesa structure dominated by c-plane {0001}, and even the lateral growth surface may disappear. b) V / III ratio High V / III ratio: Nitrogen-rich conditions. More nitrogen atoms are adsorbed, tending to stably bind on the c-plane {0001} with the lowest surface energy, thus promoting vertical growth on the c-plane while relatively inhibiting lateral growth. The morphology tends towards steep mesa-like surfaces. Low V / III ratio: Gallium-rich conditions. Gallium droplets may form, but more importantly, low nitrogen conditions increase the relative stability of nonpolar surfaces (e.g., m-plane, a-plane) and semipolar surfaces (e.g., {11-22}), promoting lateral growth. Laterally expanding trapezoidal structures are easily formed, with significant lateral growth surfaces (typically {11-22} surfaces). c) Growth temperature High temperature: Increases surface mobility and the desorption rate of reactants. Increased mobility facilitates the reach of reactants to lower energy crystal planes, usually bringing growth closer to thermodynamic equilibrium, promoting lateral growth, and forming clear crystallographic planes (such as {11-22} or {1-101}). Low temperature: insufficient surface migration, growth is controlled by kinetics, reactants combine wherever they come into contact with the surface, resulting in weakened isotropic growth and inhibited lateral growth, which easily leads to rough or irregular morphology.

[0038] In some implementations, refer to Figures 7A-7C As shown, each pixel unit is also provided with an n-type electrode 6 and a p-type electrode 7; an insulating protective layer 8 is also provided between each pixel unit and between each sub-pixel region within each pixel unit, as well as on the upper surface, exposing the corresponding n-type electrode 6 and p-type electrode 7.

[0039] The present invention also discloses a method for preparing a full-color display device, comprising the following steps: S1~S3.

[0040] S1. Substrate preparation and patterning: Preparation Figures 1A-1B The substrate 1 shown is provided, and a periodic pixel unit array is defined on the surface of the substrate 1. Each pixel unit 10 includes at least three sub-pixel regions, for example, the three sub-pixel regions include a red light (R) sub-pixel region, a green light (G) sub-pixel region, and a blue light (B) sub-pixel region, as shown. Figures 2A-2C As shown. In some embodiments, each pixel unit is a square with a side length of 5 micrometers. A window is then created within each sub-pixel region to form a growth window. For example... Figure 3 As shown in (a) to (c), a first growth window 101 is formed in the red (R) sub-pixel region, a second growth window 102 is formed in the green (G) sub-pixel region, and a third growth window 103 is formed in the blue (B) sub-pixel region. For example, it can be formed by regional etching of a patterned photoresist layer or mask material layer 2. The length of the first growth window 101 (along the C-C1 corresponding direction) is, for example, 2 micrometers, and the width (perpendicular to the C-C1 corresponding direction) is 1 micrometer; the length of the second growth window 102 is, for example, 2 micrometers, and the width is 1 micrometer; the length of the third growth window 103 is, for example, 4 micrometers, and the width is 1 micrometer.

[0041] S2, Selective lateral epitaxy and crystal plane manipulation: Lateral epitaxial growth is performed within the growth window. By controlling the epitaxial growth conditions in each sub-pixel region, microstructures with different dominant crystal planes are formed in different sub-pixel regions, such as... Figure 4 (a)~(c) and Figure 5 As shown; for example, a first microstructure 111 is formed in a first growth window 101 in the red photonic pixel region, a second microstructure 112 is formed in a second growth window 102 in the green photonic pixel region, and a third microstructure 113 is formed in a third growth window 103 in the blue photonic pixel region. The dominant crystal plane of the first microstructure 111 is a semi-polar crystal plane. The dominant crystal plane of the second microstructure 112 is a high-index crystal plane; and the dominant crystal plane of the third microstructure 113 is a c-plane.

[0042] S3, Micro-LED structure epitaxy: Micro-LED structures are epitaxially grown in a single operation on a substrate 1 containing microstructures. Due to differences in In incorporation efficiency during the epitaxial growth of Micro-LED structures on microstructures with different dominant crystal planes, the Micro-LED structures formed in each sub-pixel region have different emission wavelengths. The aforementioned single epitaxial growth is a uniform fabrication process for different sub-pixel regions. Figures 6A-6C As shown.

[0043] The above preparation method may further include step S4: An n-type electrode 6, a p-type electrode 7, and an insulating protective layer 8 are formed on a Micro-LED structure. The insulating protective layer 8 is located at the intervals between each pixel unit and between each sub-pixel region within each pixel unit, as well as on its upper surface, exposing the upper surfaces of the corresponding n-type electrode 6 and p-type electrode 7, ultimately forming a full-color display device, such as... Figures 7A-7C As shown.

[0044] In step S1, substrate 1 is a GaN single crystal substrate. A periodic pixel unit array is defined on the surface of substrate 1 by a patterned photoresist layer or mask material layer 2. Through photolithography and etching processes, windows are opened in each sub-pixel region to form growth windows for selective lateral epitaxy. The growth windows are strip-shaped, cross-shaped, or dot-matrix-shaped.

[0045] In step S2, gallium nitride-based materials are laterally epitaxially grown in growth windows corresponding to different sub-pixel regions using metal-organic chemical vapor deposition (MOCVD) technology to obtain gallium nitride microstructures with different dominant crystal planes.

[0046] In step S2, by adjusting the epitaxial growth conditions in each sub-pixel region, including but not limited to: growth temperature, reaction chamber pressure, and III / V group source gas flow rate ratio, microstructures with different dominant crystal planes are formed in different sub-pixel regions, such as... Figure 4 (a)~(c) and Figure 5 As shown, it includes: By controlling the epitaxial growth conditions of the red photonic pixel region, a first microstructure 111 with a semi-polar crystal plane as the dominant crystal plane was obtained; the crystal plane index corresponding to the semi-polar crystal plane is {11-21} or {10-11}; the In composition of this crystal plane has the highest incorporation efficiency, which is beneficial for growing long-wavelength red light active regions; By adjusting the epitaxial growth conditions of the green photonic pixel region, a second microstructure 112 with a high-index crystal plane as the dominant crystal plane was obtained; the crystal plane index corresponding to the high-index crystal plane is {11-22}; the In composition incorporation efficiency of this crystal plane is moderate, which is conducive to the growth of the green light active region; By adjusting the epitaxial growth conditions of the blue photonic pixel region, a third microstructure 113 with the c-plane as the dominant crystal plane was obtained; the crystal plane index corresponding to the c-plane is {0001}; the In composition of this crystal plane has the lowest incorporation efficiency, which is conducive to the growth of short-wavelength blue light active regions.

[0047] In step S3, a Micro-LED structure is epitaxially grown on substrate 1 containing the microstructure in a single step, such as... Figures 6A-6C As shown, it includes the following steps: On a substrate 1 containing microstructures, Micro-LED structures are formed in red, green, and blue photonic pixel regions under the same growth conditions. Each Micro-LED structure comprises an n-type GaN layer 3, a multi-quantum-well active layer 4, and a p-type GaN layer 5, sequentially epitaxially grown in a single MOCVD operation. The In content in the Micro-LED structures corresponding to the red, green, and blue photonic pixel regions differs, specifically: the In content in the red photonic pixel region is greater than that in the green photonic pixel region, which in turn is greater than that in the blue photonic pixel region. Because the multi-quantum-well active layers are grown on microstructures with different dominant crystal planes, the natural incorporation efficiency of In varies in different regions. Therefore, after a single epitaxial growth, the multi-quantum-wells in the red, green, and blue photonic pixel regions spontaneously emit different emission wavelengths, corresponding to red, green, and blue light, respectively.

[0048] Example 1 As shown in Figure 1-7C, a full-color display device includes a substrate 1, which is a gallium nitride (GaN) single crystal substrate. A periodic pixel unit array is defined on the surface of the substrate 1 by a patterned photoresist layer 2. Each pixel unit 10 includes three sub-pixel regions. Microstructures corresponding to different dominant crystal planes are formed in different sub-pixel regions. Micro-LED structures are epitaxially formed on the microstructures of different dominant crystal planes, so that different sub-pixel regions can emit light of different wavelengths, thereby realizing full-color light emission.

[0049] Reference Figures 2A-2C , Figure 3 (a)~(c) Figure 4 (a)~(c) and Figure 5 As shown, the three sub-pixel regions include a red (R) sub-pixel region, a green (G) sub-pixel region, and a blue (B) sub-pixel region. A first microstructure 111 is formed within a first growth window 101 in the red sub-pixel region, a second microstructure 112 is formed within a second growth window 102 in the green sub-pixel region, and a third microstructure 113 is formed within a third growth window 103 in the blue sub-pixel region. The dominant crystal plane of the first microstructure 111 is a semi-polar crystal plane; the dominant crystal plane of the second microstructure 112 is a high-index crystal plane; and the dominant crystal plane of the third microstructure 113 is a c-plane.

[0050] The microstructure includes gallium nitride (GaN) microstructures formed in different sub-pixel regions. By setting a GaN single-crystal substrate, GaN microstructures with different dominant crystal planes are formed in sub-pixel regions of different colors on the GaN single-crystal substrate. Subsequently, a Micro-LED structure can be epitaxially grown on the substrate with GaN microstructures with different dominant crystal planes under the same growth conditions. This not only ensures the difference in the incorporation efficiency of the In component in different sub-pixel regions of the subsequently epitaxially grown Micro-LED structure, realizing the corresponding red, green, and blue light emission of red, green, or blue light in red, green, and blue sub-pixel regions, but also the homogeneous epitaxy has good lattice matching, resulting in a lower dislocation density in the one-time epitaxial Micro-LED structure, improving the growth quality of the epitaxial layer, thereby achieving high-efficiency and high-quality fabrication of full-color display devices without the need for mass transfer or wavelength conversion.

[0051] The In content in the Micro-LED structure corresponding to the red, green, and blue photonic pixel regions differs. Specifically, the In content in the Micro-LED structure corresponding to the red photonic pixel region is greater than that in the Micro-LED structure corresponding to the green photonic pixel region, which in turn is greater than that in the Micro-LED structure corresponding to the blue photonic pixel region.

[0052] In this embodiment, by setting the crystal plane index of the dominant semi-polar crystal plane corresponding to the red photonic pixel region to {11-21}, the crystal plane index of the dominant high-index crystal plane corresponding to the green photonic pixel region to {11-22}, and the crystal plane index of the c-plane to {0001}, when fabricating various epitaxial layers in the Micro-LED structure under the same conditions, among the three crystal plane orientations, the semi-polar plane {11-21} has the smallest interface barrier potential energy, followed by the high-index crystal plane {11-22}, and the c-plane {0001} has the largest. Correspondingly, the In composition (e.g., the In composition in the multi-quantum-well active layer 4) is more likely to be oriented towards... Diffusion occurs on the {11-21} plane, making it difficult to accumulate on the {0001} plane (requiring more diffusion energy). The accumulation degree on the {11-22} plane falls between that of the {11-21} and {0001} planes, thus spontaneously generating structures with spatially varying concentrations. This means that within the same epitaxially grown Micro-LED structure, differences in microstructure guidance within different sub-pixel regions result in variations in In component concentration. Furthermore, the structural pattern, distribution density, and distribution state (uniformity) of the microstructure can facilitate refined and differentiated control of the distribution concentration and emission wavelength of full-color display devices. For example, it is possible to control 620nm red light, 530nm green light, and 460nm blue light.

[0053] Understandably, in Figure 5Although the examples of microstructures include cones and prisms, other types of regular or even irregular microstructures (such as cylinders, frustums, prisms, pyramids, etc.) can also be used. Any differentiated microstructures that produce differences in In diffusion efficiency within pixel regions corresponding to different luminous colors are considered cases not listed in this embodiment.

[0054] The Micro-LED structure in this embodiment is obtained by epitaxy on substrate 1 in a single step, wherein the single epitaxy is fabricated without differentiation for different sub-pixel regions.

[0055] Reference Figures 6A-6C As shown, the Micro-LED structure includes an n-type GaN layer 3, a multi-quantum-well active layer 4, and a p-type GaN layer 5 stacked sequentially. The multi-quantum-well active layers in different sub-pixel regions have different In compositions. The multi-quantum-well active layer 4 is guided to have different In composition incorporation efficiencies by controlling parameters such as temperature, the ratio of nitrogen to gallium source (V / III ratio), and pressure. The detailed principle is as follows: a) Reaction chamber pressure Low / atmospheric pressure: Facilitates lateral diffusion of reactants (such as NH3 and Ga sources), giving them a greater chance to reach the suspended lateral growth front. This promotes lateral growth and facilitates the formation of trapezoidal structures with smooth {11-22} slopes. The quality of the lateral epitaxial region is higher. High pressure: gas phase diffusion is suppressed, reactants are consumed more in the vertical direction, lateral growth is suppressed and vertical growth is promoted, and it is easy to form a mesa structure dominated by c-plane {0001}, and even the lateral growth surface may disappear. b) V / III ratio High V / III ratio: Nitrogen-rich conditions. More nitrogen atoms are adsorbed, tending to stably bind on the c-plane {0001} with the lowest surface energy, thus promoting vertical growth on the c-plane while relatively inhibiting lateral growth. The morphology tends towards steep mesa-like surfaces. Low V / III ratio: Gallium-rich conditions. Gallium droplets may form, but more importantly, low nitrogen conditions increase the relative stability of nonpolar surfaces (e.g., m-plane, a-plane) and semipolar surfaces (e.g., {11-22}), promoting lateral growth. Laterally expanding trapezoidal structures are easily formed, with significant lateral growth surfaces (typically {11-22} surfaces). c) Growth temperature High temperature: Increases surface mobility and the desorption rate of reactants. Increased mobility facilitates the reach of reactants to lower energy crystal planes, usually bringing growth closer to thermodynamic equilibrium, promoting lateral growth, and forming clear crystallographic planes (e.g., {11-22}). Low temperature: insufficient surface migration, growth is controlled by kinetics, reactants combine wherever they come into contact with the surface, resulting in weakened isotropic growth and inhibited lateral growth, which easily leads to rough or irregular morphology.

[0056] Reference Figures 7A-7C As shown, each pixel unit is also provided with an n-type electrode 6 and a p-type electrode 7; an insulating protective layer 8 is also provided between each pixel unit and between each sub-pixel region within each pixel unit, as well as on the upper surface, exposing the corresponding n-type electrode 6 and p-type electrode 7.

[0057] A method for fabricating a full-color display device includes the following steps: S1~S4.

[0058] S1. Substrate preparation and patterning: Preparation Figures 1A-1B The 2-inch GaN single-crystal substrate 1 shown is etched using photolithography and inductively coupled plasma (ICP). A patterned photoresist layer 2 is used to define a periodic pixel unit array on the surface of substrate 1, with a period of 10 μm. Each pixel unit 10 includes three sub-pixel regions: a red (R) sub-pixel region, a green (G) sub-pixel region, and a blue (B) sub-pixel region. Figures 2A-2C As shown; each pixel unit is a square with a side length of 5 micrometers. Then, windows are created within each sub-pixel region to form strip-shaped growth windows with a width of 1 μm. (See figure) Figure 3 As shown in (a) to (c), a first growth window 101 is formed in the red light (R) sub-pixel region, a second growth window 102 is formed in the green light (G) sub-pixel region, and a third growth window 103 is formed in the blue light (B) sub-pixel region. These windows can be formed by regional etching of the patterned photoresist layer 2. The length of the first growth window 101 (along the C-C1 corresponding direction) is 2 micrometers and the width (perpendicular to the C-C1 corresponding direction) is 1 micrometer. The length of the second growth window 102 is 2 micrometers and the width is 1 micrometer. The length of the third growth window 103 is 4 micrometers and the width is 1 micrometer.

[0059] S2, Selective lateral epitaxy and crystal plane manipulation: The patterned substrate 1 obtained in step S1 is placed in an MOCVD reaction chamber. Lateral epitaxial growth of gallium nitride-based materials is performed within growth windows corresponding to different sub-pixel regions using metal-organic chemical vapor deposition (MOCVD). By controlling the epitaxial growth conditions in each sub-pixel region, gallium nitride microstructures with corresponding dominant crystal planes are formed in different sub-pixel regions, such as... Figure 4 (a)~(c) and Figure 5As shown, a first microstructure 111 is formed within a first growth window 101 in the red photonic pixel region, a second microstructure 112 is formed within a second growth window 102 in the green photonic pixel region, and a third microstructure 113 is formed within a third growth window 103 in the blue photonic pixel region. The dominant crystal plane of the first microstructure 111 is a semi-polar crystal plane. The dominant crystal plane of the second microstructure 112 is a high-index crystal plane; and the dominant crystal plane of the third microstructure 113 is a c-plane.

[0060] S3, Micro-LED structure epitaxy: In the same reaction chamber, on a substrate 1 containing microstructures, under the same growth conditions, Micro-LED structures were epitaxially grown in red, green, and blue sub-pixel regions in a single operation. Due to the difference in In incorporation efficiency during the epitaxial growth of Micro-LED structures on microstructures with different dominant crystal planes, the Micro-LED structures formed in each sub-pixel region have different emission wavelengths. The aforementioned single epitaxy is a uniform fabrication for different sub-pixel regions. Figures 6A-6C As shown, the Micro-LED structure includes an n-type GaN layer 3, a multi-quantum-well active layer 4, and a p-type GaN layer 5, which are sequentially epitaxially grown in a single MOCVD process. The In content in the Micro-LED structures corresponding to the red, green, and blue photonic pixel regions differs, with the In content in the red photonic pixel region being greater than that in the green photonic pixel region, which in turn is greater than that in the blue photonic pixel region. Since the active layers of multiple quantum wells are grown on microstructures with different dominant crystal planes, the natural incorporation efficiency of the In composition varies in different regions. Therefore, after one epitaxial growth, the multiple quantum wells in the red, green, and blue photonic pixel regions spontaneously emit different emission wavelengths, corresponding to red, green, and blue light, respectively. Under the same epitaxial conditions, the In composition of the multiple quantum wells in the R region is the highest, with an emission wavelength of about 620 nm (red light), followed by the G region with a wavelength of about 530 nm (green light), and the B region has the lowest wavelength of about 460 nm (blue light).

[0061] S4. An n-type electrode 6, a p-type electrode 7, and an insulating protective layer 8 are formed on the Micro-LED structure. The insulating protective layer 8 is located at the intervals between each pixel unit and between each sub-pixel region within each pixel unit, as well as on its upper surface, exposing the upper surfaces of the corresponding n-type electrode 6 and p-type electrode 7, ultimately forming a full-color display device, such as... Figures 7A-7C As shown.

[0062] In step S2, by adjusting the epitaxial growth conditions in each sub-pixel region, including but not limited to: growth temperature, reaction chamber pressure, and III / V group source gas flow rate ratio, microstructures with different dominant crystal planes are formed in different sub-pixel regions, such as... Figure 4 (a)~(c) and Figure 5 As shown, it includes: By controlling the epitaxial growth conditions of the red photonic pixel region, a first microstructure 111 with a semi-polar crystal plane as the dominant crystal plane was obtained; the crystal plane index corresponding to the semi-polar crystal plane is {11-21}; the In composition of this crystal plane has the highest incorporation efficiency, which is beneficial for growing long-wavelength red light active regions; By adjusting the epitaxial growth conditions of the green photonic pixel region, a second microstructure 112 with a high-index crystal plane as the dominant crystal plane was obtained; the crystal plane index corresponding to the high-index crystal plane is {11-22}; the In composition incorporation efficiency of this crystal plane is moderate, which is conducive to the growth of the green light active region; By adjusting the epitaxial growth conditions of the blue photonic pixel region, a third microstructure 113 with the c-plane as the dominant crystal plane was obtained; the crystal plane index corresponding to the c-plane is {0001}; the In composition of this crystal plane has the lowest incorporation efficiency, which is conducive to the growth of short-wavelength blue light active regions.

[0063] In step S2, no mask is needed for region B, as the surface of region B is the same as the surface of the GaN single-crystal substrate. For region G, the temperature is increased to 1100℃, the pressure is decreased to 200 mbar, and the flow rates of (trimethylindium)TMIn and NH3 are appropriately adjusted to guide lateral epitaxy to primarily expose the {11-22} high-index facets. For region R, the temperature is decreased to 1000℃, the pressure is increased to 600 mbar, and a higher flow rate of TMI / TMGa (trimethylgallium) is used to promote the formation of a {11-21} semi-polar crystal facet.

[0064] Any parts or structures not specifically described in this invention can be made using existing technologies or products, and will not be elaborated upon here.

[0065] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A full color display device, characterized by comprising: The substrate and the periodic pixel unit array located on the substrate are included, each pixel unit includes at least three sub-pixel regions, different sub-pixel regions are formed with microstructures corresponding to different dominant crystal faces, and the microstructures of the different dominant crystal faces are epitaxially formed with Micro-LED structures, so that different sub-pixel regions can emit light of different wavelengths respectively, thereby realizing full-color light emission.

2. The full-color display device according to claim 1, wherein The three sub-pixel regions include a red light sub-pixel region, a green light sub-pixel region and a blue light sub-pixel region; The In content in the Micro-LED structures corresponding to the red light sub-pixel region, the green light sub-pixel region and the blue light sub-pixel region is different; Preferably, the In content in the Micro-LED structure corresponding to the red light sub-pixel region > the In content in the Micro-LED structure corresponding to the green light sub-pixel region > the In content in the Micro-LED structure corresponding to the blue light sub-pixel region.

3. The full color display device according to any one of claims 1-2, wherein, The dominant crystal face of the microstructure of the red light sub-pixel region is a semi-polar crystal face; the dominant crystal face of the microstructure of the green light sub-pixel region is a high-index crystal face; and the dominant crystal face of the microstructure of the blue light sub-pixel region is a c face; preferably, the crystal face index corresponding to the semi-polar crystal face is {11-21} or {10-11}; the crystal face index corresponding to the high-index crystal face is {11-22}; and the crystal face index corresponding to the c face is {0001}.

4. The full color display device according to any one of claims 1 to 2, wherein, The Micro-LED structure is obtained by one-time epitaxy on the substrate, and the one-time epitaxy is prepared without differentiation for different sub-pixel regions; Preferably, the Micro-LED structure includes an n-type GaN layer, a multi-quantum well active layer and a p-type GaN layer which are stacked in sequence, wherein the multi-quantum well active layers of different sub-pixel regions have different In contents.

5. The full-color display device according to claim 1, wherein The substrate is a gallium nitride single crystal substrate; Preferably, the microstructure includes a gallium nitride microstructure formed in different sub-pixel regions.

6. The full-color display device according to claim 1, wherein Each pixel unit is further provided with an n-type electrode and a p-type electrode; the intervals between each sub-pixel region in each pixel unit and between each pixel unit and the upper surface are further provided with an insulating protective layer and expose the corresponding n-type electrode and p-type electrode.

7. A method for fabricating a full-color display device, characterized by comprising: The method includes the following steps: S1, a substrate is prepared, and a periodic pixel unit array is defined on the surface thereof, each pixel unit includes at least three sub-pixel regions; then a window is opened in each sub-pixel region to form a growth window; S2, lateral epitaxial growth is performed in the growth window, and by adjusting the epitaxial growth conditions in each sub-pixel region, microstructures corresponding to different dominant crystal faces are formed in different sub-pixel regions; S3, a Micro-LED structure is epitaxially grown on the substrate containing the microstructures, and based on the difference in In incorporation efficiency during epitaxial growth of the Micro-LED structure on the microstructures of different dominant crystal faces, the Micro-LED structures formed in each sub-pixel region have different light emitting wavelengths; wherein the one-time epitaxy is prepared without differentiation for different sub-pixel regions.

8. The preparation method according to claim 7, characterized in that, In step S1, the substrate is a gallium nitride single crystal substrate, a periodic pixel unit array is defined on the surface of the substrate by a patterned photoresist layer or a mask material layer, and a growth window for selective lateral epitaxy is formed by a photoetching and etching process in each sub-pixel region; Preferably, the growth window is in the shape of a strip, a cross or a dot array.

9. The preparation method according to claim 7, characterized in that, In step S2, lateral epitaxial growth of gallium nitride-based materials is performed in the growth window corresponding to each sub-pixel region by a metal organic chemical vapor deposition technique, and gallium nitride microstructures with different dominant crystal faces are obtained; Preferably, the epitaxial growth conditions in each sub-pixel region are adjusted to form microstructures with different dominant crystal faces in different sub-pixel regions, including: The epitaxial growth conditions of the red sub-pixel region are adjusted to obtain a first microstructure with a semi-polar crystal face as the dominant crystal face; The epitaxial growth conditions of the green sub-pixel region are adjusted to obtain a second microstructure with a high-index crystal face as the dominant crystal face; The epitaxial growth conditions of the blue sub-pixel region are adjusted to obtain a third microstructure with a c face as the dominant crystal face; Preferably, the crystal face index corresponding to the semi-polar crystal face is {11-21} or {10-11}, the crystal face index corresponding to the high-index crystal face is {11-22}, and the crystal face index corresponding to the c face is {0001}.

10. The preparation method according to claim 7, characterized in that, In step S3, the content of In component in the Micro-LED structure corresponding to the red sub-pixel region is greater than that in the Micro-LED structure corresponding to the green sub-pixel region, which is greater than that in the Micro-LED structure corresponding to the blue sub-pixel region; Preferably, the one-time epitaxial growth of the Micro-LED structure on the substrate containing the microstructure includes the following steps: The n-type GaN layer, the multi-quantum well active layer and the p-type GaN layer are sequentially epitaxially grown on the substrate containing the microstructure, wherein the multi-quantum well active layer in different sub-pixel regions has different In components; Preferably, the preparation method further includes step S4: An n-type electrode, a p-type electrode and an insulating protective layer are formed on the Micro-LED structure, the insulating protective layer is located at the intervals between each pixel unit and each sub-pixel region in each pixel unit and on the upper surface, and the upper surfaces of the corresponding n-type electrode and p-type electrode are exposed.

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