Micro-led chip, preparation method thereof and visible light communication system

Abstract

The application relates to the technical field of optoelectronic manufacturing, and particularly discloses a Micro-LED chip, a preparation method thereof and a visible light communication system. The Micro-LED chip comprises a substrate, a first electrode, a first semiconductor layer, an active light-emitting layer, a second semiconductor layer, a contact layer, a second electrode and a microlens. A normal projection part of the contact layer on the second semiconductor layer covers the second semiconductor layer, and the cross section of the contact layer is in an inverted trapezoidal shape in the thickness direction; the second electrode is arranged around the contact layer; the normal projection of the second electrode and the contact layer on the second semiconductor layer covers the second semiconductor layer; the top surface of the microlens is in a curved shape, and the top surface forms a light-out surface of the Micro-LED chip. By implementing the application, the light beam angle can be reduced, the manufacturing difficulty of the microlens is reduced, and the manufacturing yield is improved.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic manufacturing technology, and in particular to a Micro-LED chip and its fabrication method, and a visible light communication system. Background Technology

[0002] Visible light communication systems possess advantages such as high bandwidth, low latency, and low power consumption. They outperform traditional radio frequency communication in terms of data transmission rate and electromagnetic interference resistance, and have broad application prospects. A core component of visible light communication systems is the microlens, whose main function is to compress the originally divergent ±90° conical beam into a collimated beam of ±12°, enabling the light to be coupled more precisely into the corresponding cores of a multi-core optical fiber, significantly improving coupling efficiency and suppressing crosstalk between adjacent channels. However, visible light communication systems based on Micro-LED chips currently face the following challenges: 1. Difficulty in lens manufacturing: Microlenses require nanometer-level precision, with curvature and thickness errors controlled to <5nm, far exceeding traditional process capabilities; 2. Low yield of microlens systems: Due to the presence of multiple channels (generally over 400 channels) in visible light communication systems, any deviation in the shape of a microlens can lead to the failure of the entire system, resulting in a current yield of only 70-85%; 3. Overly complex coupling and calibration between lenses and Micro-LED chips: 400+ channels require precise alignment channel by channel, demanding high coupling accuracy and advanced equipment, resulting in high time costs and susceptibility to environmental vibrations. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a Micro-LED chip and its preparation method, which can reduce the beam angle, reduce the manufacturing difficulty of microlenses, and improve the manufacturing yield.

[0004] Another technical problem that this invention aims to solve is to provide a visible light communication system.

[0005] To address the aforementioned technical problems, this invention provides a Micro-LED chip, comprising: A substrate having a first surface and a second surface disposed opposite to each other in the thickness direction; A first electrode is disposed on the first surface; A first semiconductor layer is disposed on the second surface and electrically connected to the first electrode through the substrate; An active light-emitting layer is disposed above the first semiconductor layer; A second semiconductor layer is disposed above the active light-emitting layer; A contact layer is disposed above the second semiconductor layer; the orthogonal projection of the contact layer onto the second semiconductor layer covers the second semiconductor layer, and the cross-section of the contact layer is inverted trapezoidal in the thickness direction; A second electrode is disposed above the second semiconductor layer and surrounds the contact layer; the orthographic projections of the second electrode and the contact layer onto the second semiconductor layer cover the second semiconductor layer; and A microlens is disposed on the contact layer, and its top surface is curved, forming the light-emitting surface of the Micro-LED chip.

[0006] As an improvement to the above technical solution, the contact layer is a Mg-doped GaN layer with a thickness of 100nm~200nm and a doping concentration of 5×10⁻⁶. 19 cm -3 ~1×10 21 cm -3 ; and / or The second electrode comprises a Ti layer, a Ni layer and an Au layer stacked sequentially, with thicknesses of 10nm~50nm, 80nm~150nm and 20nm~80nm, respectively; The microlens is made of SiO2.

[0007] As an improvement to the above technical solution, the substrate is a GaN substrate; and / or The first semiconductor layer is an N-type GaN layer with a thickness of 300 nm to 500 nm and a Si doping concentration of 1 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3 ; and / or The active light-emitting layer comprises alternating layers of InGaN well layers and GaN barrier layers, with a period number of 2 to 5. The InGaN well layer has a thickness of 2 nm to 3 nm and an In content of 0.15 to 0.35%. The GaN barrier layer has a thickness of 5 nm to 10 nm. The second semiconductor layer is a p-type GaN layer with a thickness of 50 nm to 200 nm and a Mg doping concentration of 1 × 10⁻⁶. 19 cm -3 ~1×10 20 cm -3 .

[0008] As an improvement to the above technical solution, a photonic crystal layer is also included, which is disposed between the first semiconductor layer and the active light-emitting layer; The photonic crystal layer includes a body portion and an embedded portion; the body portion is made of GaN and has a thickness of 20nm~40nm; the body portion has a plurality of periodically distributed holes, and the embedded portion is filled in the holes; The embedded part is made of AlGaN, and the proportion of Al component is 0.3~0.5%.

[0009] As an improvement to the above technical solution, a MoS2 layer is also included, which is disposed between the second semiconductor layer and the contact layer; The thickness of the MoS2 layer is 20nm~50nm.

[0010] As an improvement to the above technical solution, a buffer layer, an undoped GaN layer, an AlGaN confinement layer, a first semiconductor layer, a photonic crystal layer, an active light-emitting layer, an electron blocking layer, a second semiconductor layer, a MoS2 layer, a contact layer, a second electrode, and a microlens are sequentially stacked on the second surface. The buffer layer is a low-temperature GaN layer with a thickness of 20nm~50nm; the undoped GaN layer has a thickness of 500nm~1500nm; the AlGaN confinement layer has a thickness of 10nm~50nm and an Al content of 0.2~0.4%; the electron blocking layer is an AlGaN layer with a thickness of 100nm~200nm and an Al content of 0.2~0.3%.

[0011] Accordingly, the present invention also discloses a method for fabricating a Micro-LED chip, which includes: An initial substrate is provided, having a second surface and a third surface disposed opposite to each other; A first semiconductor layer, an active light-emitting layer, a second semiconductor layer, and an initial contact layer are sequentially formed on the second surface; The initial contact layer is etched to form a contact layer with an inverted trapezoidal cross-section, thus obtaining the first intermediate. A second electrode is formed on the side where the contact layer of the first intermediate is located; An initial lens layer is formed on the second electrode and the contact layer; The initial lens layer is etched to form a microlens on the contact layer, thus obtaining a second intermediate. The initial substrate is thinned along the side containing the third surface to form the first surface; A first electrode is formed on the first surface, thus obtaining a Micro-LED chip.

[0012] As an improvement to the above technical solution, in the step of forming an initial lens layer on the second electrode and the contact layer, a SiO2 layer is deposited by PECVD. The process parameters for depositing the SiO2 layer include: a deposition temperature of 200℃~250℃, a chamber pressure of 20mtorr~50mtorr, a SiH4 flow rate of 15sccm~20sccm, a N2O flow rate of 60sccm~80sccm, and an Ar flow rate of 50sccm~100sccm.

[0013] As an improvement to the above technical solution, in the step of etching the initial lens layer to form a microlens on the contact layer and obtain the second intermediate, BOE etching solution is used for etching. The volume ratio of NH4F solution to HF solution in the BOE etching solution is 6:1 to 8:1, and the etching temperature is 30℃ to 40℃.

[0014] Accordingly, the present invention also discloses a visible light communication system comprising the aforementioned Micro-LED chip.

[0015] Implementing this invention has the following beneficial effects: In one embodiment of the present invention, a Micro-LED chip includes a substrate, a first electrode, a first semiconductor layer, an active light-emitting layer, a second semiconductor layer, a contact layer, a second electrode, and a microlens. The contact layer, projected onto the second semiconductor layer, covers the second semiconductor layer, and its cross-section is inverted trapezoidal in the thickness direction. The second electrode surrounds the contact layer. The second electrode and the projection of the contact layer onto the second semiconductor layer cover the second semiconductor layer. The top surface of the microlens is curved and forms the light-emitting surface of the Micro-LED chip. Based on the above structure, the Micro-LED chip, firstly, by using a contact layer with a specific morphology as a base, directly integrates the microlens onto the light-emitting surface of the Micro-LED chip, significantly simplifying the fabrication of the microlens and eliminating the need for subsequent alignment, thus greatly improving manufacturing yield. Secondly, by using a microlens with a specific morphology and by blocking light from other parts through the first electrode, the combination effectively improves light confinement, significantly reducing the beam angle and establishing a good foundation for communication transmission. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a Micro-LED chip in one embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a Micro-LED chip in another embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a Micro-LED chip in another embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a Micro-LED chip in another embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0019] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0020] Please see Figure 1As a first aspect of the present invention, a Micro-LED chip is provided, comprising a substrate 100, a first electrode 200, a first semiconductor layer 310, an active light-emitting layer 320, a second semiconductor layer 330, a contact layer 340, a second electrode 400, and a microlens 500. The substrate 100 has a first surface and a second surface disposed opposite each other in the thickness direction. The first electrode 200 is disposed on the first surface. The first semiconductor layer 310, the active light-emitting layer 320, the second semiconductor layer 330, and the contact layer 340 are sequentially stacked on the second surface. The projection portion of the contact layer 340 onto the second semiconductor layer 330 covers the second semiconductor layer 330, and the cross-section of the contact layer 340 is inverted trapezoidal in the thickness direction. The second electrode 400 is disposed above the second semiconductor layer 330 and surrounds the contact layer 340. The sidewall of the second electrode 400 contacts the contact layer 340, meaning that the orthogonal projections of the contact layer 340 and the second electrode 400 onto the second semiconductor layer 330 completely cover the second semiconductor layer 330. The microlens 500 is disposed on the contact layer 340, and its top surface is curved, forming the light-emitting surface of the Micro-LED chip. Based on the above structure, the Micro-LED chip offers several advantages. First, by using a contact layer 340 with a specific morphology as a base, the microlens 500 can be directly integrated into the light-emitting surface of the Micro-LED chip, significantly simplifying the fabrication of the microlens 500 and eliminating the need for subsequent alignment, thus greatly improving manufacturing yield. Second, the first electrode 200 effectively blocks light emitted from parts other than the microlens 500. Furthermore, by using a microlens with a curved top surface, the light confinement is enhanced, significantly reducing the beam angle and establishing a solid foundation for communication transmission.

[0021] Specifically, the substrate 100 is a silicon-based substrate or a GaN substrate, and conductivity is achieved through doping to realize the electrical connection between the first electrode 200 and the first semiconductor layer 310. Preferably, in some embodiments, the substrate 100 is a GaN substrate, which has a high degree of lattice matching with the first semiconductor layer 310 and the second semiconductor layer 330, which is beneficial to reducing the interface defect density and increasing the optical power density. At the same time, it has excellent heat dissipation performance, making it suitable for Micro-LED communication scenarios with high modulation speeds.

[0022] Specifically, the first semiconductor layer 310 is an N-type GaN layer or an N-type AlGaN layer, but is not limited thereto. Preferably, in some embodiments, the first semiconductor layer 310 is an N-type GaN layer with a thickness of 300 nm to 500 nm and a Si doping concentration of 1 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3The N-type GaN layer has excellent electron mobility and carrier injection efficiency, which can improve optical power density and enhance the modulation bandwidth and optical output stability of Micro-LED chips.

[0023] Specifically, the active light-emitting layer 320 is an InGaN-GaN type multiple quantum well layer, an InGaN-AlGaN type multiple quantum well layer, or an AlGaN-AlGaN type multiple quantum well layer, but is not limited to these. Preferably, in some embodiments, the active light-emitting layer 320 includes alternately stacked InGaN well layers and GaN barrier layers, with a period number of 2 to 5, the thickness of the InGaN well layers being 2 nm to 3 nm, the In composition ratio being 0.15 to 0.35, and the thickness of the GaN barrier layers being 5 nm to 10 nm. Specifically, the second semiconductor layer 330 is a P-type GaN layer or a P-type AlGaN layer, but is not limited thereto. Preferably, in some embodiments, the second semiconductor layer 330 is a P-type GaN layer with a thickness of 50 nm to 200 nm and a Mg doping concentration of 1 × 10⁻⁶. 19 cm -3 ~1×10 20 cm -3 .

[0024] Specifically, the contact layer 340 is a highly doped P-GaN layer (doping concentration ≥ 5 × 10⁻⁶). 19 cm -3 The contact layer 340 may be a Mg-doped GaN layer, but is not limited to this. Preferably, in some embodiments, the contact layer 340 is a Mg-doped GaN layer with a thickness of 100 nm to 200 nm and a doping concentration of 5 × 10⁻⁶. 19 cm -3 ~1×10 21 cm -3 The highly doped contact layer 340 not only reduces contact resistance and increases optical power density, but also works in conjunction with the microlens 500 to reduce light loss and improve light extraction efficiency.

[0025] Specifically, the contact layer 340 is photolithographically etched to form a mesa structure. More specifically, its cross-section in the thickness direction is an inverted trapezoidal shape. Based on this inverted trapezoidal structure, not only can a microlens 500 with a curved top surface be formed by subsequent photolithographic etching, but the contact area between the second electrode 400 and the contact layer 340 is also increased, thereby improving the ohmic contact. Specifically, the angle between the sidewall of the contact layer 340 and the plane containing the second semiconductor layer 330 is 55° to 65°.

[0026] Specifically, the first electrode 200 is a metal stack commonly used in the art, such as a Ni / Au stack, a Ni / Ti / Au stack, or a Ti / Al / Ni / Au stack, but is not limited thereto. Preferably, in some embodiments, the first electrode 200 is a Ti / Au stack with thicknesses of 20nm~50nm and 100nm~200nm, respectively.

[0027] Specifically, the second electrode 400 is a common metal stack in the art, such as a Ni / Au stack, a Ni / Ti / Au stack, or a Ti / Al / Ni / Au stack, but is not limited thereto. Preferably, in some embodiments, the second electrode 400 includes a Ti layer, a Ni layer, and an Au layer stacked sequentially, with thicknesses of 10nm~50nm, 80nm~150nm, and 20nm~80nm, respectively. This structure of the second electrode 400 not only has good ohmic contact performance but also effectively blocks light from escaping from the non-emitting surface, reducing the light beam angle. Furthermore, during the etching process, the second electrode 400 can effectively prevent the sidewalls of the contact layer 340 and the sidewalls of the second semiconductor layer from being etched, further improving the optical power density. More preferably, in some embodiments, the thickness of the second electrode 400 is the same as the thickness of the contact layer 340.

[0028] Specifically, the microlens 500 has a curved surface structure, and its top surface can be a sphere, an ellipsoid, a cylinder, or other non-spherical shape, such as a parabola, a hyperboloid, or a freeform surface, but is not limited thereto. Preferably, in some embodiments, the top surface of the microlens 500 is a sphere with a diameter of 3μm to 20μm.

[0029] The microlens 500 can be made of materials such as SiO2, TiO2, and Al2O3, but is not limited to these. Preferably, in some embodiments, the microlens 500 is made of SiO2, which has a low refractive index and high light transmittance, which is beneficial to improving the light extraction rate. In addition, its high hardness can effectively protect the light-emitting surface.

[0030] Preferably, please refer to Figure 2 In some embodiments, the Micro-LED chip further includes a photonic crystal layer 600 disposed between the first semiconductor layer 310 and the active light-emitting layer 320. The photonic crystal layer 600 includes a body portion 610 and an embedded portion 620. The body portion 610 is made of GaN and has a thickness of 20 nm to 40 nm. Multiple periodically distributed holes are formed on the body portion 610, and the embedded portion 620 is filled within the holes. The embedded portion 620 is made of AlGaN, with an Al content of 0.3% to 0.5%. This photonic crystal layer 600 can suppress nonradiative recombination within the active light-emitting layer 320, optimize the internal quantum efficiency of the Micro-LED chip, and improve its modulation bandwidth.

[0031] Preferably, please refer to Figure 3 In some implementations, the Micro-LED chip also includes a MoS2 layer 700, which is disposed between the second semiconductor layer 330 and the contact layer 340; the thickness of the MoS2 layer 700 is 20nm~50nm. The MoS2 layer 700 has high carrier mobility, which can improve carrier transport speed, thereby enhancing high-frequency response performance and increasing the modulation bandwidth of the Micro-LED chip.

[0032] Preferably, please refer to Figure 4 In some embodiments, a buffer layer 350, an undoped GaN layer 360, an AlGaN confinement layer 370, a first semiconductor layer 310, a photonic crystal layer 600, an active light-emitting layer 320, an electron blocking layer 380, a second semiconductor layer 330, a MoS2 layer 700, a contact layer 340, a second electrode 400, and a microlens 500 are sequentially stacked on the second surface of the substrate 100. The substrate 100 is a GaN substrate 100; the buffer layer 350 is a low-temperature GaN layer (MOCVD growth temperature ≤ 600℃) with a thickness of 20nm~50nm; the undoped GaN layer 360 has a thickness of 500nm~1500nm; the AlGaN confinement layer 370 has a thickness of 10nm~50nm and an Al content of 0.2~0.4%; the first semiconductor layer 310 is an N-type GaN layer with a thickness of 300nm~500nm and a Si doping concentration of 1×10⁻⁶. 18 cm -3 ~5×10 19 cm -3 The active light-emitting layer 320 comprises alternating layers of InGaN well layers and GaN barrier layers, with a period number of 2 to 5. The thickness of the InGaN well layers is 2 nm to 3 nm, and the In content is 0.15% to 0.35%. The thickness of the GaN barrier layers is 5 nm to 10 nm. The electron blocking layer 380 is an AlGaN layer with a thickness of 100 nm to 200 nm and an Al content of 0.2% to 0.3%. The second semiconductor layer 330 is a P-type GaN layer with a thickness of 50 nm to 200 nm and a Mg doping concentration of 1 × 10⁻⁶. 19 cm -3 ~1×10 20 cm -3 The thickness of the MoS2 700 layer is 20nm~50nm. The Micro-LED chip with the above structure has high optical power density, narrow spectral width, and fast modulation speed, making it suitable for high-speed visible light communication systems.

[0033] Specifically, based on the Micro-LED chip described above in this invention, the beam angle can be limited to 7°~12°, and the bandwidth can reach 0.8GHz~2.5GHz.

[0034] Accordingly, as a second aspect of the present invention, the present invention provides a method for fabricating a Micro-LED chip, comprising the following steps: (1) Provide an initial substrate; The initial substrate includes a second surface and a third surface that are disposed opposite to each other in the thickness direction.

[0035] Preferably, in some embodiments, the initial substrate is polished and cleaned before forming subsequent semiconductor layers.

[0036] (2) A first semiconductor layer, an active light-emitting layer, a second semiconductor layer and an initial contact layer are sequentially formed on the second surface; Specifically, layered structures can be grown using molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), but are not limited to these methods.

[0037] Preferably, in some embodiments, a buffer layer, an undoped GaN layer, an AlGaN confinement layer, a first semiconductor layer, a photonic crystal layer, an active light-emitting layer, an electron blocking layer, a second semiconductor layer, a MoS2 layer, and an initial contact layer are sequentially formed on the second surface by MOCVD.

[0038] More specifically, when forming the photonic crystal layer, a GaN layer is first formed on the first semiconductor layer, then periodically distributed holes are etched to obtain the body part, and then an AlGaN material embedding part is formed in the holes.

[0039] (3) The initial contact layer is etched to form a contact layer with an inverted trapezoidal cross section, thus obtaining the first intermediate body; Specifically, the initial contact layer can be etched using dry or wet etching processes to form a contact layer with an inverted trapezoidal cross-section.

[0040] (4) A second electrode is formed on the side where the contact layer of the first intermediate is located; Specifically, the second electrode can be formed by electron beam evaporation or magnetron sputtering, but is not limited thereto. Preferably, in some embodiments, a photoresist layer is first formed on the side where the contact layer of the first intermediate is located, then the photoresist layer in the predetermined area is removed by exposure and development, then a metal stack is deposited by evaporation, and finally the photoresist layer and the metal stack thereon are removed by peeling off the photoresist to obtain the second electrode.

[0041] (5) An initial lens layer is formed on the second electrode and the contact layer; Specifically, the initial lens layer can be formed by plasma-enhanced chemical vapor deposition (PECVD) or atomic layer deposition (ALD), but is not limited to these methods.

[0042] Preferably, in some embodiments, a SiO2 layer is deposited by PECVD as the initial lens layer. The process parameters for depositing the SiO2 layer include: a deposition temperature of 200℃~250℃, a chamber pressure of 20mtorr~50mtorr; a SiH4 flow rate of 15sccm~20sccm, a N2O flow rate of 60sccm~80sccm, and an Ar flow rate of 50sccm~100sccm. The SiO2 layer obtained based on the above deposition process has the advantages of high uniformity and low stress accumulation, which is beneficial for the subsequent formation of curved microlenses.

[0043] (6) The initial lens layer is etched to form a microlens on the contact layer, thus obtaining the second intermediate; The initial lens layer can be etched using either dry or wet etching processes, but is not limited to these. Preferably, in some embodiments, when the initial lens layer is a SiO2 layer, BOE etching solution is used for etching; wherein the volume ratio of NH4F solution (40 vol% aqueous solution) to HF solution (49 vol% aqueous solution) in the BOE etching solution is 6:1 to 8:1, and the etching temperature is 30°C to 40°C. Based on the above etching conditions, a microlens with a smooth curved surface profile on the top surface can be formed.

[0044] (7) Thin the initial substrate along the side where the third surface is located to form the first surface; (8) A first electrode is formed on the first surface, thus obtaining a Micro-LED chip.

[0045] Specifically, the first electrode can be formed by electron beam evaporation or magnetron sputtering processes, but is not limited to these.

[0046] Based on the above-described method for fabricating Micro-LED chips according to the present invention, the microlens structure can be integrated into the Micro-LED chip in a single unit, and the fabrication process is simple, avoiding the stepped exposure and stepped curing processes in traditional microlens fabrication. Furthermore, the microlens formation method of the present invention has strong overall compatibility with the Micro-LED chip fabrication method, making it suitable for large-scale manufacturing.

[0047] Accordingly, as a third aspect of the present invention, the present invention also provides a visible light communication system comprising the aforementioned Micro-LED chip. The system further includes, but is not limited to, a modulation module, a detector, a demodulation module, etc.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the described embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0049] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for fabricating a Micro-LED chip, characterized in that, include: An initial substrate is provided, having a second surface and a third surface disposed opposite to each other; A first semiconductor layer, an active light-emitting layer, a second semiconductor layer, and an initial contact layer are sequentially formed on the second surface; The initial contact layer is etched to form a contact layer with an inverted trapezoidal cross-section, thus obtaining a first intermediate body; wherein, the orthogonal projection of the contact layer onto the second semiconductor layer covers the second semiconductor layer, and the cross-section of the contact layer is inverted trapezoidal in the thickness direction; A second electrode is formed on the side where the contact layer of the first intermediate is located; wherein the second electrode is disposed around the contact layer; the orthogonal projection of the second electrode and the contact layer onto the second semiconductor layer covers the second semiconductor layer; An initial lens layer is formed on the second electrode and the contact layer; The initial lens layer is etched to form a microlens on the contact layer, resulting in a second intermediate; wherein the top surface of the microlens is curved and forms the light-emitting surface of the Micro-LED chip. The initial substrate is thinned along the side containing the third surface to form the first surface; A first electrode is formed on the first surface, thus obtaining a Micro-LED chip; The initial lens layer is a SiO2 layer, which is deposited by PECVD. The deposition process parameters include: deposition temperature of 200℃~250℃, chamber pressure of 20mtorr~50mtorr; SiH4 flow rate of 15sccm~20sccm, N2O flow rate of 60sccm~80sccm, and Ar flow rate of 50sccm~100sccm. The initial lens layer is etched using BOE etching solution to form a microlens; the volume ratio of NH4F solution to HF solution in the BOE etching solution is 6:1 to 8:1, and the etching temperature is 30℃ to 40℃.

2. The method for fabricating a Micro-LED chip as described in claim 1, characterized in that, The contact layer is a Mg-doped GaN layer with a thickness of 100 nm to 200 nm and a doping concentration of 5 × 10⁻⁶. 19 cm -3 ~1×10 21 cm -3 ; and / or The second electrode comprises a Ti layer, a Ni layer and an Au layer stacked sequentially, with thicknesses of 10nm~50nm, 80nm~150nm and 20nm~80nm, respectively.

3. The method for fabricating a Micro-LED chip as described in claim 1, characterized in that, The substrate is a GaN substrate; and / or The first semiconductor layer is an N-type GaN layer with a thickness of 300 nm to 500 nm and a Si doping concentration of 1 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3 ; and / or The active light-emitting layer comprises alternating layers of InGaN well layers and GaN barrier layers, with a period number of 2 to 5. The InGaN well layer has a thickness of 2 nm to 3 nm and an In content of 0.15 to 0.35%. The GaN barrier layer has a thickness of 5 nm to 10 nm. The second semiconductor layer is a p-type GaN layer with a thickness of 50 nm to 200 nm and a Mg doping concentration of 1 × 10⁻⁶. 19 cm -3 ~1×10 20 cm -3 .

4. The method for fabricating a Micro-LED chip as described in any one of claims 1 to 3, characterized in that, It also includes a photonic crystal layer disposed between the first semiconductor layer and the active light-emitting layer; The photonic crystal layer includes a body portion and an embedded portion; the body portion is made of GaN and has a thickness of 20nm~40nm; the body portion has a plurality of periodically distributed holes, and the embedded portion is filled in the holes; The embedded part is made of AlGaN, and the proportion of Al component is 0.3~0.5%.

5. The method for fabricating a Micro-LED chip as described in any one of claims 1 to 3, characterized in that, It also includes a MoS2 layer, which is disposed between the second semiconductor layer and the contact layer; The thickness of the MoS2 layer is 20nm~50nm.

6. The method for fabricating a Micro-LED chip as described in claim 1, characterized in that, The second surface is sequentially stacked with a buffer layer, an undoped GaN layer, an AlGaN confinement layer, the first semiconductor layer, a photonic crystal layer, the active light-emitting layer, an electron blocking layer, the second semiconductor layer, a MoS2 layer, the contact layer, and a microlens; The buffer layer is a low-temperature GaN layer with a thickness of 20nm~50nm; the undoped GaN layer has a thickness of 500nm~1500nm; the AlGaN confinement layer has a thickness of 10nm~50nm and an Al content of 0.2~0.4%; the electron blocking layer is an AlGaN layer with a thickness of 100nm~200nm and an Al content of 0.2~0.3%.

7. A Micro-LED chip, characterized in that, It is prepared by the method for preparing a Micro-LED chip as described in any one of claims 1 to 6.

8. A visible light communication system, characterized in that, Includes the Micro-LED chip as described in claim 7.

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