Micro-LED chip with high color purity

Abstract

The invention provides a high-color-purity Micro-LED chip which comprises an n-type electrode, an epitaxial lamination layer and a p-type electrode, the epitaxial lamination layer comprises an n-type semiconductor layer, a multi-quantum-well light-emitting layer and a p-type semiconductor layer, the multi-quantum-well light-emitting layer is located between the n-type semiconductor layer and the p-type semiconductor layer, the side wall of the epitaxial lamination layer is coated with a first insulating layer, and the side wall of the p-type electrode is coated with a second insulating layer. The top surface of the epitaxial laminated layer is coated with a light-permeable second insulating layer, the outer side of the first insulating layer is provided with a reflecting layer, an annular shading layer is arranged above the second insulating layer, the outline of the annular shading layer is the same as that of the epitaxial laminated layer, and the middle part of the annular shading layer is a hollow light-permeable area; and the projection area of the hollow light-transmitting region in the longitudinal direction is smaller than the projection area of the bottom surface of the epitaxial laminated layer in the longitudinal direction. According to the Micro-LED chip, through the arrangement of the annular light shielding layer and other structures, the color purity and the light extraction efficiency are improved, and meanwhile the electrical performance and the light emitting performance are optimized.

Description

Technical Field

[0001] The present invention belongs to the technical field of display, and in particular relates to a Micro-LED chip with high color purity. Background Art

[0002] Micro-LED display is a highly competitive next-generation display technology that uses Micro-LED chips directly as the light-emitting pixel units of the display to achieve self-luminous display. The light spectrum of the Micro-LED chip directly determines the monochromatic light spectrum of the three primary colors of red, green and blue in the Micro-LED display, and further determines the color gamut and other chromaticity performance of the display.

[0003] In the manufacturing process of Micro-LED chips, the epitaxial wafer obtained by epitaxial growth must first be etched to obtain the mesa corresponding to a single chip. The side walls of the mesa formed by etching have a certain inclination angle and cannot be absolutely vertical. At the same time, since the lateral size of the Micro-LED chip is in the micron level, the light emission on the side wall becomes significant. However, there is often a certain difference in the spectrum between the light emitted from the sidewall area and the light emitted from the internal area of ​​the mesa. For example, the spectral peak wavelength of the light emitted from the sidewall area of ​​the nitride Micro-LED chip is blue, which will cause the overall spectrum of the Micro-LED chip to be broadened, which is not conducive to the realization of narrow spectrum and high color purity Micro-LED chips. It is extremely unfavorable for applications with light coupling such as AR display, and it will also degrade the color gamut for three-primary color full-color display applications.

[0004] Although the prior art has disclosed technical solutions for improving the actual performance of Micro-LED chips, none of them considers how to suppress the impact of sidewall area luminescence on the overall spectrum broadening, and does not consider improving the color purity of luminescence and the color gamut of display from the perspective of chip technology. Summary of the invention

[0005] In order to solve the above-mentioned technical problems in the prior art, the present application provides a Micro-LED chip with high color purity to eliminate the light emission from the sidewall area and improve the color purity of the overall light emission spectrum of the Micro-LED chip.

[0006] The present invention proposes a Micro-LED chip with high color purity, comprising: an n-type electrode, an epitaxial stack and a p-type electrode, the epitaxial stack comprising an n-type semiconductor layer, a multi-quantum well light-emitting layer and a p-type semiconductor layer, the multi-quantum well light-emitting layer being located between the n-type semiconductor layer and the p-type semiconductor layer, the sidewall of the epitaxial stack being coated with a first insulating layer, the top surface of the epitaxial stack being coated with a second insulating layer that is translucent, a reflective layer being arranged outside the first insulating layer, an annular light-shielding layer being arranged above the second insulating layer, the outer contour of the annular light-shielding layer being the same as the outer contour of the epitaxial stack, the middle part of the annular light-shielding layer being a hollow light-transmitting area, and the longitudinal projection area of ​​the hollow light-transmitting area being smaller than the longitudinal projection area of ​​the bottom surface of the epitaxial stack. Through the specific arrangement of the electrode, the epitaxial stack, the insulating layer and the key annular light-shielding layer, the chip has the foundation for improving color purity in structure, the arrangement of the annular light-shielding layer and its relationship with the epitaxial stack provide the possibility for shielding the sidewall light emission, thereby hopefully reducing the influence of the sidewall light emission on the overall spectrum and improving color purity.

[0007] In some specific embodiments, the sidewalls of the epitaxial stack are inclined, and the bottom width of the epitaxial stack is smaller than the top width, and the annular light shielding layer at least covers the projection of the sidewalls of the epitaxial stack on the top surface. This arrangement further optimizes the shielding effect of the annular light shielding layer on the sidewall light emission, making it more difficult for the sidewall light emission to be directly emitted, thereby enhancing the ability to improve color purity.

[0008] In some specific embodiments, the first insulating layer covers the bottom surface of the epitaxial stack. This configuration helps to better protect the epitaxial stack, and may also help to improve the performance stability of the chip to a certain extent, indirectly providing a guarantee for improving color purity.

[0009] In some specific embodiments, the reflective layer includes a metal reflective layer or a distributed Bragg reflective layer, and the annular light-shielding layer includes a metal reflective layer, a distributed Bragg reflective layer or a light-absorbing layer. The reflective layer can reflect the lateral light back to the top surface to improve the light extraction efficiency, reduce the light loss, and help improve the luminous efficiency and color purity of the chip. Different annular light-shielding layer material selections can better achieve the effect of shielding the side wall light emission according to actual needs, further improving the color purity.

[0010] In some specific embodiments, an electron blocking layer and a current spreading layer are provided in the p-type semiconductor layer, which can optimize current transmission and electron blocking, improve the electrical performance of the chip, and indirectly help improve the luminous efficiency and color purity of the chip.

[0011] In some specific embodiments, 3 to 5 pairs of quantum wells are arranged in the multi-quantum well light-emitting layer, and the quantum wells are composed of a chemical formula of Al x Ga y In zP is composed of two semiconductor layers with different components and nanometer thickness, where x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1. Reasonable setting of the number of quantum wells can optimize the luminescence performance and improve the luminescence efficiency and color purity.

[0012] In some specific embodiments, the width of the p-type electrode and the width of the n-type electrode are both smaller than the width of the hollow light-transmitting area. This arrangement ensures that the electrodes will not hinder the light transmission and luminescence of the central area, which is beneficial to the normal luminescence of the chip and improves the color purity.

[0013] In some specific embodiments, the thickness of the p-type electrode and the n-type electrode is greater than the thickness of the first insulating layer and the second insulating layer, respectively. This arrangement can ensure good contact between the electrode and the semiconductor layer, and can also protect the insulating layer to a certain extent, which helps to improve the electrical performance and stability of the chip and indirectly improve the color purity.

[0014] In some specific embodiments, the first insulating layer is provided with a through hole at the position of the p-type electrode, and the p-type electrode is in contact with the p-type semiconductor layer; the n-type electrode is in contact with the upper surface or the lower surface of the n-type semiconductor layer, and when the n-type electrode is in contact with the lower surface of the n-type semiconductor layer, the first insulating layer is provided with a through hole at the position of the n-type electrode; when the n-type electrode is in contact with the upper surface of the n-type semiconductor layer, the second insulating layer is provided with a through hole at the position of the n-type electrode.

[0015] In some specific embodiments, the n-type electrode contacts the n-type semiconductor layer, and the p-type electrode contacts the p-type semiconductor layer. This arrangement ensures a good electrical connection between the electrode and the semiconductor layer, which is beneficial to the transmission of current and the normal light emission of the chip, and has a certain auxiliary effect on improving color purity.

[0016] The high color purity Micro-LED chip of the present invention has the following technical effects:

[0017] 1. Improve color purity: This application sets an annular light-shielding layer, whose outline is consistent with the epitaxial stack and the longitudinal projection area of ​​the central hollow light-transmitting area is smaller than the bottom area of ​​the epitaxial stack, which can effectively shield the light emission of the sidewall area. At the same time, the annular light-shielding layer can be a metal reflective layer, a distributed Bragg reflective layer or a light-absorbing layer, which can better absorb or reflect the sidewall light emission, reduce the impact of the sidewall light emission on the overall spectrum, and thus improve the color purity of the chip light emission.

[0018] 2. Improve light extraction efficiency: The present application uses a reflective layer (metal reflective layer or distributed Bragg reflective layer) set on the outside of the epitaxial stack side wall to reflect part of the internal light that is transmitted to the side wall through the optical waveguide effect to the top surface for emission, thereby avoiding lateral light emission and improving the light extraction efficiency of the chip.

[0019] 3. Optimizing electrical performance: This application can optimize current transmission and electron blocking and improve the electrical performance of the chip by setting an electron blocking layer and a current expansion layer in the p-type semiconductor layer. The n-type electrode contacts the n-type semiconductor layer, the p-type electrode contacts the p-type semiconductor layer, and the thickness of the p-type electrode and the n-type electrode is greater than the thickness of the first insulating layer and the second insulating layer, respectively, which ensures good contact between the electrode and the semiconductor layer, is conducive to the transmission of current, and thus indirectly improves the luminous efficiency and color purity of the chip.

[0020] 4. Optimize luminescence performance: In this application, 3-5 pairs of quantum wells are set in the multi-quantum well light-emitting layer. The reasonable number of quantum wells can optimize the luminescence performance and improve the luminescence efficiency and color purity. The first insulating layer covers the bottom surface of the epitaxial stack, and the second insulating layer is light-transmissive and covers the top surface of the epitaxial stack. This setting of the insulating layer helps to protect the epitaxial stack and provide protection for the normal light emission of the chip, indirectly improving the luminescence performance and color purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and are used together with the description to explain the principles of the present invention. It will be easy to recognize other embodiments and many expected advantages of the embodiments because they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale with each other. The same reference numerals refer to corresponding similar parts.

[0022] Figure 1 is a schematic structural diagram of a Micro-LED chip with high color purity according to a first embodiment of the present invention;

[0023] Figure 2 Schematic diagram of internal light of a Micro-LED chip with high color purity according to a first specific embodiment of the present invention;

[0024] Figure 3 is a schematic structural diagram of a Micro-LED chip with high color purity according to a fourth embodiment of the present invention;

[0025] Figure 4 4 is a schematic diagram of the structure of a Micro-LED chip with high color purity according to the fifth embodiment of the present invention. DETAILED DESCRIPTION

[0026] In the following detailed description, reference is made to the accompanying drawings, which form a part of the detailed description and are shown by illustrative specific embodiments in which the present invention can be put into practice. To this end, directional terms, such as "top", "bottom", "left", "right", "up", "down", etc., are used with reference to the orientation of the figures described. Because the parts of the embodiments can be positioned in several different orientations, directional terms are used for the purpose of illustration and are by no means limiting. It should be understood that other embodiments may be utilized or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description should not be adopted in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0027] Figure 1 The schematic diagram of the structure of the high color purity Micro-LED chip of the present invention is shown as follows: Figure 1 As shown, the high color purity Micro-LED chip is provided with an n-type electrode 1, an epitaxial stack and a p-type electrode 2, wherein the epitaxial stack is provided with an n-type semiconductor layer 3, a multi-quantum well light-emitting layer 4 and a p-type semiconductor layer 5, the multi-quantum well light-emitting layer 4 is located between the n-type semiconductor layer 3 and the p-type semiconductor layer 5, and a first insulating layer 6 is provided for covering the side wall of the epitaxial stack, and a second insulating layer 7 is provided for covering the top surface of the epitaxial stack, and the light emitted by the multi-quantum well light-emitting layer 4 can pass through the second insulating layer 7, and a reflective layer 8 is further provided on the outside of the first insulating layer 6, and an annular shading layer 9 is provided above the second insulating layer 7, and the outer contour of the annular shading layer 9 is consistent with the outer contour of the epitaxial stack, and the center of the annular shading layer 9 is a hollow light-transmitting area 10, and the longitudinal projection area of ​​the hollow light-transmitting area 10 is smaller than the longitudinal projection area of ​​the bottom surface of the epitaxial stack, so that the annular shading layer 9 can shield the light emission of the side wall area.

[0028] In a specific embodiment, the sidewall of the epitaxial stack is an inclined sidewall, the width of the bottom surface of the epitaxial stack is smaller than the width of the top surface of the epitaxial stack, and the annular light shielding layer 9 at least covers the projection of the sidewall of the epitaxial stack on the top surface (that is, the annular light shielding layer 9 is arranged directly above the area corresponding to the sidewall). This arrangement further optimizes the shielding effect of the annular light shielding layer on the light emitted from the sidewall, making it more difficult for the light emitted from the sidewall to be directly emitted, thereby enhancing the ability to improve color purity.

[0029] In a specific embodiment, the first insulating layer 6 also covers the bottom surface of the epitaxial stack. This configuration helps to better protect the epitaxial stack, and may also help improve the performance stability of the chip to a certain extent, indirectly providing a guarantee for improving color purity.

[0030] In a specific embodiment, the reflective layer 8 is a metal reflective layer or a distributed Bragg reflective layer; the light emitted by the multi-quantum well light-emitting layer 4 cannot pass through the annular light-shielding layer 9, and the annular light-shielding layer 9 is a metal reflective layer or a distributed Bragg reflective layer or a light-absorbing layer. The reflective layer 8 can reflect the lateral light back to the top surface, improve the light extraction efficiency, reduce the light loss, and help improve the luminous efficiency and color purity of the chip. Different materials for the annular light-shielding layer 9 can better achieve the effect of shielding the side wall light emission according to actual needs, and further improve the color purity.

[0031] In a specific embodiment, the p-type semiconductor layer 5 also includes an electron blocking layer and a current spreading layer. The multi-quantum well light-emitting layer 4 is provided with three pairs of quantum wells. The quantum wells are composed of a general chemical formula of Al x In y Ga z N (where x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1) is formed by stacking two semiconductor layers with different components and nanometer thickness.

[0032] In a specific embodiment, the width of the p-type electrode 2 and the width of the n-type electrode 1 are both smaller than the width of the hollow light-transmitting region 10. The thickness of the p-type electrode 2 and the thickness of the n-type electrode 1 are both greater than the thickness of the first insulating layer 6 and the thickness of the second insulating layer 7. The first insulating layer 6 is provided with a through hole at the location of the n-type electrode 1 so that the n-type electrode 1 contacts the n-type semiconductor layer 3, and the first insulating layer 6 is provided with a through hole at the location of the p-type electrode 2 so that the p-type electrode 2 contacts the p-type semiconductor layer 5. The n-type electrode 1 contacts the lower surface of the n-type semiconductor layer 3.

[0033] Continue to refer Figure 2 , Figure 2 FIG. 4 shows a schematic diagram of a structure of a calibration component according to a specific embodiment of the present invention. Figure 2As shown, the light is mainly emitted from the multi-quantum well light-emitting layer 4, which is located between the n-type semiconductor 3 and the p-type semiconductor layer 5. A part of the light emitted by the multi-quantum well light-emitting layer 4 can be emitted from the hollow light-transmitting area 10 at the top of the chip through the second insulating layer 6. For the sidewall area, the propagation of the light emitted by the multi-quantum well light-emitting layer 4 in the sidewall area is restricted. The annular light-shielding layer 9 is arranged above the second insulating layer 7 and its outer contour is consistent with the epitaxial stack. The longitudinal projection area of ​​the central hollow light-transmitting area 10 is smaller than the bottom area of ​​the epitaxial stack, so the light emitted from the sidewall area is absorbed by the annular light-shielding layer 9 or reflected back to the multi-quantum well light-emitting layer 4 for reabsorption, and will not leak from the top surface, thereby reducing the influence of the sidewall light emission on the overall spectrum and improving the color purity. From the top, the light is emitted from the hollow light-transmitting area 10, and the width of the electrodes (n-type electrode 1 and p-type electrode 2) is smaller than the width of the hollow light-transmitting area 10, which will not hinder the emission of light. At the same time, the thickness of the p-type electrode 2 and the n-type electrode 1 are both greater than the thickness of the first insulating layer 6 and the second insulating layer 7, ensuring good contact between the electrode and the semiconductor layer, which is conducive to the normal light emission of the chip. The reflective layer 8 (metal reflective layer or distributed Bragg reflective layer) outside the first insulating layer 6 reflects part of the internal light that is transmitted to the side wall through the optical waveguide effect to the top surface for emission, avoiding lateral light emission and improving the light extraction efficiency of the chip.

[0034] In the second embodiment of the present application, 5 pairs of quantum wells can be set in the multi-quantum well light-emitting layer 4. The quantum well is formed by stacking two semiconductor layers with different components and nanometer thickness with a general chemical formula of AlxGayInzP (where x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1). The quantum well is formed by stacking two semiconductor layers with different components and nanometer thickness with a specific general chemical formula. A reasonable number of quantum wells and structural settings can optimize the luminescence performance and improve the luminescence efficiency and color purity. The rest of the structure is similar to Figure 1 The embodiments are the same as those of the present invention and will not be described again here.

[0035] In the third embodiment of the present application, the n-type electrode 1 and the p-type electrode 2 are exchanged in position, and the n-type semiconductor layer 3 and the p-type semiconductor layer 5 are exchanged in position. Figure 1 The electrodes are still in contact with the corresponding semiconductor layers, and other structures remain unchanged, so the electrical performance can still be guaranteed, the current can be transmitted normally, the chip can work normally, and the annular light-shielding layer still has the function of shielding the side wall light emission to improve the color purity, and the side wall outer reflective layer still has the function of improving the light extraction efficiency.

[0036] Figure 3 FIG. 4 shows a schematic structural diagram of a Micro-LED chip with high color purity according to a fourth embodiment of the present invention. Figure 3As shown, the n-type electrode 1 contacts the upper surface of the n-type semiconductor layer 3, and the second insulating layer 7 is provided with a through hole at the location of the n-type electrode 1 so that the n-type electrode 1 contacts the n-type semiconductor layer 3. The change in the contact method does not affect the overall performance of the chip, and the electrical performance can still ensure the normal transmission of current. At the same time, in terms of optical performance, the color purity can still be improved through the annular shading layer, and the light extraction efficiency can be improved through the reflective layer. The rest of the structure is the same as Figure 1 The embodiments are the same as those of the present invention and will not be described again here.

[0037] Figure 4 FIG. 4 shows a schematic structural diagram of a high color purity Micro-LED chip according to a fifth embodiment of the present invention. Figure 4 As shown, the n-type electrode 1 is also provided with an extension portion, which is located on the bottom surface of the reflective layer 8 and is adjacent to the p-type electrode 2. The rest of the structure is the same as Figure 1 The embodiments are the same as those of the present invention and will not be described again here.

[0038] The high color purity Micro-LED chip of the present application is provided with an annular shading layer 9 on the top of the chip, and the center of the chip is a hollow light-transmitting area, so that the light in the central area of ​​the chip can be emitted, while the light emitted in the side wall area is absorbed by the annular shading layer 9 or reflected back by the annular shading layer 9 to the quantum well for reabsorption. The light emitted in the side wall area is shielded and will not be directly emitted, thereby improving the color purity of the chip light emission and reducing the spectrum broadening problem caused by the light emission in the side wall area; a reflective layer 8 is provided on the outside of the side wall to reflect part of the internal light that is transmitted to the side wall through the optical waveguide effect to the top surface for emission, thereby avoiding lateral light emission and improving the light extraction efficiency of the chip.

[0039] Obviously, those skilled in the art can make various modifications and changes to the embodiments of the present invention without departing from the spirit and scope of the present invention. In this way, if these modifications and changes are within the scope of the claims of the present invention and their equivalents, the present invention is also intended to cover these modifications and changes. The word "comprising" does not exclude the presence of other elements or steps not listed in the claims. The simple fact that certain measures are recorded in mutually different dependent claims does not indicate that the combination of these measures cannot be used to profit. Any reference numerals in the claims should not be considered to limit the scope.

Claims

1. High color purity Micro-LED chip, characterized by: include: An n-type electrode, an epitaxial stack and a p-type electrode, the epitaxial stack comprising an n-type semiconductor layer, a multi-quantum well light-emitting layer and a p-type semiconductor layer, the multi-quantum well light-emitting layer being located between the n-type semiconductor layer and the p-type semiconductor layer, the sidewalls of the epitaxial stack being coated with a first insulating layer, the top surface of the epitaxial stack being coated with a second light-transmissive insulating layer, a reflective layer being arranged on the outer side of the first insulating layer, an annular light-shielding layer being arranged above the second insulating layer, the outer contour of the annular light-shielding layer being the same as the outer contour of the epitaxial stack, the middle portion of the annular light-shielding layer being a hollow light-transmissive region, and the longitudinal projection area of ​​the hollow light-transmissive region being smaller than the longitudinal projection area of ​​the bottom surface of the epitaxial stack.

2. The high color purity Micro-LED chip according to claim 1, characterized in that: The sidewalls of the epitaxial stack are inclined, and the bottom width of the epitaxial stack is smaller than the top width. The annular light shielding layer at least covers the projection of the sidewalls of the epitaxial stack on the top surface.

3. The high color purity Micro-LED chip according to claim 1, characterized in that: The first insulating layer covers the bottom surface of the epitaxial stack.

4. The high color purity Micro-LED chip according to claim 1, characterized in that: The reflective layer includes a metal reflective layer or a distributed Bragg reflective layer, and the annular light-shielding layer includes a metal reflective layer, a distributed Bragg reflective layer or a light-absorbing layer.

5. The high color purity Micro-LED chip according to claim 1, characterized in that: An electron blocking layer and a current spreading layer are arranged in the p-type semiconductor layer.

6. The high color purity Micro-LED chip according to claim 1, characterized in that: The multi-quantum well light-emitting layer is provided with 3 to 5 pairs of quantum wells, and the quantum wells are composed of a chemical formula of Al x Ga y In z P is formed by stacking two semiconductor layers with different components and nanometer thickness, where x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1.

7. The high color purity Micro-LED chip according to claim 1, characterized in that: The width of the p-type electrode and the width of the n-type electrode are both smaller than the width of the hollow light-transmitting area.

8. The high color purity Micro-LED chip according to claim 1, characterized in that: The thickness of the p-type electrode and the n-type electrode are respectively greater than the thickness of the first insulating layer and the second insulating layer.

9. The high color purity Micro-LED chip according to claim 1, characterized in that: The first insulating layer is provided with a through hole at the position of the p-type electrode, and the p-type electrode is in contact with the p-type semiconductor layer; the n-type electrode is in contact with the upper surface or the lower surface of the n-type semiconductor layer, and when the n-type electrode is in contact with the lower surface of the n-type semiconductor layer, the first insulating layer is provided with a through hole at the position of the n-type electrode; when the n-type electrode is in contact with the upper surface of the n-type semiconductor layer, the second insulating layer is provided with a through hole at the position of the n-type electrode.

10. The high color purity Micro-LED chip according to claim 1, characterized in that: The n-type electrode is provided with an extension portion, and the extension portion is located on the bottom surface of the reflective layer and is adjacent to the p-type electrode.

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