Miniature light-emitting pixel units and their formation methods, miniature light-emitting diode chips and microdisplay panels

Abstract

A miniature light-emitting pixel unit and its formation method, a miniature light-emitting diode chip, and a micro-display panel are disclosed. The pixel unit includes: a first epitaxial layer and a multi-quantum-well layer; a second epitaxial layer, with the multi-quantum-well layer located between the first and second epitaxial layers; an ohmic contact layer in contact with the first epitaxial layer; and a metal reflective layer in contact with the ohmic contact layer. The metal reflective layer has several protrusions extending into the ohmic contact layer. Extending the protrusions of the metal reflective layer into the ohmic contact layer reduces the distance between the metal reflective layer and the multi-quantum-well layer, allowing plasma energy excited by the metal reflective layer to penetrate the ohmic contact layer and the first epitaxial layer, thereby enabling efficient coupling between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum-well layer. By providing multiple protrusions, the surface area of ​​the metal reflective layer can be effectively increased, thereby improving its reflectivity.

Description

Technical Field

[0001] This invention relates to the field of microdisplay technology, and in particular to a micro light-emitting pixel unit and its formation method, a micro light-emitting diode chip, and a microdisplay panel. Background Technology

[0002] Inorganic micro-pixel light-emitting diodes, also known as micro LEDs or μ-LEDs, are a high-pixel-density LED planar display technology that uses micrometer-scale LEDs as pixels, assembled on a CMOS backplane at micrometer-scale intervals. Its display principle involves thinning, miniaturizing, and arraying the LED structure, resulting in dimensions ranging from a few micrometers to tens of micrometers. Micro LED displays possess excellent characteristics such as high luminous efficiency, high brightness, short response time, and high reliability, and are hailed by the industry as the next-generation display technology and the ultimate form of display.

[0003] However, existing micro-luminescent pixel units still have many problems. Summary of the Invention

[0004] The technical problem solved by the present invention is to provide a micro light-emitting pixel unit and its formation method, a micro light-emitting diode chip and a micro display panel, so as to improve the coupling effect between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum well layer.

[0005] To address the aforementioned problems, the present invention provides a micro-luminescent pixel unit, comprising: a first epitaxial layer having a first side and a second side opposite to each other; a multi-quantum well layer located on the first side, the multi-quantum well layer being in contact with the first epitaxial layer; a second epitaxial layer located on the first side, the multi-quantum well layer being located between the first epitaxial layer and the second epitaxial layer; an ohmic contact layer located on the second side, the ohmic contact layer being in contact with the first epitaxial layer; and a metal reflective layer located on the second side, the metal reflective layer being in contact with the ohmic contact layer, the ohmic contact layer being located between the first epitaxial layer and the metal reflective layer; wherein the metal reflective layer has a plurality of protrusions extending into the ohmic contact layer.

[0006] Optionally, the projection area of ​​the surface of the protrusion near the first epitaxial layer toward the first epitaxial layer is located within the projection area of ​​the surface of the protrusion away from the first epitaxial layer toward the first epitaxial layer.

[0007] Optionally, the structure of the protrusion includes: a cone, a pyramid, a frustum, a truncated cone, or a hemisphere.

[0008] Optionally, some of the protrusions are arranged in an array.

[0009] Optionally, the number of protrusions ranges from 70 to 120.

[0010] Optionally, the ohmic contact layer has a plurality of recesses that match the protrusions, and the ohmic contact layer is tightly bonded to the metal reflective layer.

[0011] Optionally, the ohmic contact layer is made of a transparent conductive material, which includes transparent metal materials or transparent conductive oxide materials.

[0012] Optionally, the material of the metal reflective layer includes silver, aluminum, or gold.

[0013] Optionally, it further includes: a conductive plug located on the second side, the conductive plug being in contact with the metal reflective layer, the metal reflective layer being located between the ohmic contact layer and the conductive plug.

[0014] Optionally, the material of the conductive plug includes copper.

[0015] Optionally, it further includes: a microlens located on the first side, wherein the projection region of the multi-quantum well layer toward the first epitaxial layer is located within the projection region of the microlens toward the first epitaxial layer.

[0016] Optionally, the height of the protrusion is less than or equal to the thickness of the ohmic contact layer, the thickness of the ohmic contact layer is in the range of 50nm to 100nm, and the height of the protrusion is in the range of 40nm to 100nm.

[0017] Optionally, the materials of the first epitaxial layer and the second epitaxial layer include gallium nitride, indium gallium nitride, or aluminum gallium indium phosphide.

[0018] Optionally, the material of the multiple quantum well layer includes gallium nitride, indium gallium nitride, aluminum indium phosphide, or gallium indium phosphide.

[0019] Accordingly, the present invention also provides a method for forming a micro-light-emitting pixel unit, comprising: forming a first epitaxial layer having a first side and a second side opposite to each other; forming a multi-quantum-well layer on the first side, the multi-quantum-well layer being in contact with the first epitaxial layer; forming a second epitaxial layer on the first side, the multi-quantum-well layer being located between the first epitaxial layer and the second epitaxial layer; forming an ohmic contact layer on the second side, the ohmic contact layer being in contact with the first epitaxial layer; forming a metal reflective layer on the second side, the metal reflective layer being in contact with the ohmic contact layer, the ohmic contact layer being located between the first epitaxial layer and the metal reflective layer; wherein the metal reflective layer has a plurality of protrusions, the protrusions extending into the ohmic contact layer.

[0020] Optionally, the projection area of ​​the surface of the protrusion near the first epitaxial layer toward the first epitaxial layer is located within the projection area of ​​the surface of the protrusion away from the first epitaxial layer toward the first epitaxial layer.

[0021] Optionally, the structure of the protrusion includes: a cone, a pyramid, a frustum, a truncated cone, or a hemisphere.

[0022] Optionally, some of the protrusions are arranged in an array.

[0023] Optionally, the number of protrusions ranges from 70 to 120.

[0024] Optionally, the ohmic contact layer has a plurality of recesses that match the protrusions, and the ohmic contact layer is tightly bonded to the metal reflective layer.

[0025] Optionally, the method for forming the ohmic contact layer and the metal reflective layer includes: forming an initial ohmic contact layer on the second side; performing a patterned etching process on the initial ohmic contact layer to form the ohmic contact layer, wherein the ohmic contact layer has a plurality of the recesses; forming the metal reflective layer on the second side, wherein the metal reflective layer covers the ohmic contact layer, and the metal contact layer fills the plurality of the recesses to form corresponding protrusions.

[0026] Optionally, the method for forming the metal reflective layer on the second side includes: forming a sacrificial layer on the second side; forming an initial metal reflective layer on the second side using a vapor deposition process, the initial metal reflective layer covering the surface of the sacrificial layer and the ohmic contact layer; and removing the sacrificial layer and the initial metal reflective layer on the surface of the sacrificial layer to form the metal reflective layer.

[0027] Optionally, the method for forming the metal reflective layer on the second side includes: forming an initial metal reflective layer on the second side using a vapor deposition process, the initial metal reflective layer covering the ohmic contact layer; and performing a patterned etching process on the initial metal reflective layer to form the metal reflective layer.

[0028] Optionally, it further includes: forming a conductive plug on the second side, the conductive plug being in contact with the metal reflective layer, the metal reflective layer being located between the ohmic contact layer and the conductive plug.

[0029] Optionally, it further includes: forming a microlens on the first side, wherein the projection region of the multi-quantum well layer toward the first epitaxial layer is located within the projection region of the microlens toward the first epitaxial layer.

[0030] Accordingly, the present invention also provides a miniature light-emitting diode chip, comprising: a plurality of miniature light-emitting pixel units as described in any of the above technical solutions; a driving backplane, wherein the plurality of miniature light-emitting pixel units are electrically connected to the driving backplane respectively.

[0031] Accordingly, the present invention also provides a micro display panel, including a micro light-emitting diode chip as described in the above technical solution.

[0032] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0033] In the micro-light-emitting pixel unit of the present invention, by extending a plurality of the protrusions of the metal reflective layer into the ohmic contact layer, the distance between the metal reflective layer and the multi-quantum well layer is reduced. This allows the plasma energy excited by the metal reflective layer to penetrate the ohmic contact layer and the first epitaxial layer, thereby enabling efficient coupling between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum well layer, thus increasing the light intensity of the micro-light-emitting pixel unit. Furthermore, there is no need to thin the first epitaxial layer, ensuring the current generated by the first epitaxial layer. Additionally, by providing multiple protrusions, the surface area of ​​the metal reflective layer can be effectively increased, thereby improving the reflectivity of the metal reflective layer.

[0034] Furthermore, the projection area of ​​the protrusion near the first epitaxial layer toward the first epitaxial layer is located within the projection area of ​​the protrusion away from the first epitaxial layer toward the first epitaxial layer. By setting the side of the protrusion near the multi-quantum well layer as a tip, more plasma energy excited by the metal reflective layer accumulates at the tip, further enhancing the coupling effect between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum well layer.

[0035] Furthermore, several of the protrusions are arranged in an array. The arrayed protrusions are more uniformly distributed, further enhancing the coupling effect between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum-well layer.

[0036] Furthermore, the number of protrusions ranges from 70 to 120. Setting the number of protrusions in the range of 70 to 120 can prevent the coupling effect between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum well layer from being too small, while also preventing the process difficulty from being increased by having too many protrusions.

[0037] Furthermore, the ohmic contact layer has several recesses that match the protrusions, and the ohmic contact layer is tightly bonded to the metal reflective layer. This tight bonding between the metal reflective layer and the ohmic contact layer enhances the overall strength of the device structure.

[0038] In the method for forming a micro-light-emitting pixel unit according to the technical solution of the present invention, by extending a plurality of the protrusions of the metal reflective layer into the ohmic contact layer, the distance between the metal reflective layer and the multi-quantum well layer is reduced. This allows the plasma energy excited by the metal reflective layer to penetrate the ohmic contact layer and the first epitaxial layer, thereby enabling efficient coupling between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum well layer, thus increasing the light intensity of the micro-light-emitting pixel unit. Furthermore, there is no need to thin the thickness of the first epitaxial layer, ensuring the current generated by the first epitaxial layer. In addition, by providing multiple protrusions, the surface area of ​​the metal reflective layer can be effectively increased, thereby improving the reflectivity of the metal reflective layer.

[0039] Furthermore, the projection area of ​​the protrusion near the first epitaxial layer toward the first epitaxial layer is located within the projection area of ​​the protrusion away from the first epitaxial layer toward the first epitaxial layer. By setting the side of the protrusion near the multi-quantum well layer as a tip, more plasma energy excited by the metal reflective layer accumulates at the tip, further enhancing the coupling effect between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum well layer.

[0040] Furthermore, several of the protrusions are arranged in an array. The arrayed protrusions are more uniformly distributed, further enhancing the coupling effect between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum-well layer.

[0041] Furthermore, the number of protrusions ranges from 70 to 120. Setting the number of protrusions in the range of 70 to 120 can prevent the number of protrusions from being too small, which would affect the coupling effect between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum well layer. It can also prevent the number of protrusions from being too large, which would increase the difficulty of the manufacturing process.

[0042] Furthermore, the ohmic contact layer has several recesses that match the protrusions, and the ohmic contact layer is tightly bonded to the metal reflective layer. The tight bonding between the metal reflective layer and the ohmic contact layer can improve the overall strength of the device structure. Attached Figure Description

[0043] Figure 1This is a schematic diagram of the structure of a miniature light-emitting pixel unit;

[0044] Figures 2 to 9 This is a schematic diagram of the structure of each step in the method for forming a micro light-emitting pixel unit according to an embodiment of the present invention. Detailed Implementation

[0045] As described in the background section, existing micro-luminescent pixel units still have many problems. These will be explained in detail below.

[0046] Figure 1 This is a schematic diagram of the structure of a miniature light-emitting pixel unit.

[0047] Please refer to Figure 1 A miniature light-emitting pixel unit includes: a first epitaxial layer 100 having opposing first sides 100a and second sides 100b; a multi-quantum well layer 101 located on the first side 100a, the multi-quantum well layer 101 being in contact with the first epitaxial layer 100; a second epitaxial layer 102 located on the first side 100a, the multi-quantum well layer 101 being located between the first epitaxial layer 100 and the second epitaxial layer 102; an ohmic contact layer 103 located on the second side 100b, the ohmic contact layer 103 being in contact with the first epitaxial layer 100; a passivation layer 109 located on the second side 100b, the passivation layer 109 covering the exposed surfaces of the first epitaxial layer 100, the multi-quantum well layer 101 and the second epitaxial layer 102, and the passivation layer 109 exposing the surface of the ohmic contact layer 103; and a passivation layer 109 located on the second side 100b. A metal reflective layer 104 is located on the second side 100b, which is in contact with the ohmic contact layer 103, and the ohmic contact layer 103 is located between the first epitaxial layer 100 and the metal reflective layer 104; a conductive plug 105 is located on the second side 100b, which is in contact with the metal reflective layer 104, and the metal reflective layer 104 is located between the ohmic contact layer 103 and the conductive plug 105; an insulating layer 106 is located on the second side 100b, and the conductive plug 105 is located on the insulating layer 106, and the insulating layer 106 covers the metal reflective layer 104; a microlens 107 is located on the first side 100a, and the microlens 107 is located on the side of the second epitaxial layer 102 away from the first epitaxial layer 101; and an epitaxial electrode 108 is located on the second side 100b, and the epitaxial electrode 108 is electrically connected to the second epitaxial layer 102.

[0048] In this embodiment, the materials of the first epitaxial layer 100 and the second epitaxial layer 102 can be gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium indium phosphide (AlGaInP), or other III-V group semiconductor materials. The material of the multi-well layer 101 can be gallium nitride, indium gallium nitride, aluminum indium phosphide (AlGaP), or gallium indium phosphide (GaInP), wherein gallium nitride and indium gallium nitride are used to generate blue or green light, and indium gallium nitride, aluminum indium phosphide, and gallium indium phosphide are used to generate red light. The material of the ohmic contact layer 103 is a transparent conductive material, including transparent metal materials or transparent conductive oxide materials. The transparent conductive oxide material can be, but is not limited to, an N-type oxide semiconductor, preferably indium tin oxide. The material of the conductive plug 105 is copper. The materials of the insulating layer 106 and the passivation layer 109 can both be silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, or aluminum oxide. The material of the microlens 107 can be silicon oxide or silicon nitride. The microlens 107 is hemispherical in shape, and this hemispherical structure can further improve the light extraction efficiency of the micro-light-emitting pixel unit. The epitaxial electrode 108 can be made of gold, silver, or copper.

[0049] In this embodiment, the metal reflective layer 104 is a metal material, specifically silver, aluminum or gold, which can excite surface plasma. The excited plasma energy can interact with the light emitted by the multi-quantum well layer 101, thereby increasing the light intensity of the micro light-emitting pixel unit.

[0050] However, the first epitaxial layer 100 and the ohmic contact layer 103 lie between the metal reflective layer 104 and the multi-quantum well layer 101. When the distance between the metal reflective layer 104 and the multi-quantum well layer 101 is large, the plasma energy excited by the metal reflective layer 104 cannot penetrate the first epitaxial layer 100 and the ohmic contact layer 103, resulting in poor coupling between the excited plasma energy and the light emitted by the multi-quantum well layer 101. If the coupling effect between the excited plasma energy and the light emitted by the multi-quantum well layer 101 is improved by thinning the first epitaxial layer 100, it will affect the current generated by the first epitaxial layer 100.

[0051] Based on this, the present invention provides a micro-light-emitting pixel unit and its formation method, a micro-light-emitting diode chip, and a micro-display panel. By extending a plurality of the protrusions of the metal reflective layer into the ohmic contact layer, the distance between the metal reflective layer and the multi-quantum well layer is reduced, allowing the plasma energy excited by the metal reflective layer to penetrate the ohmic contact layer and the first epitaxial layer. This enables efficient coupling between the plasma energy excited by the metal reflective layer and the light emitted by the multi-quantum well layer, thereby increasing the light intensity of the micro-light-emitting pixel unit. Furthermore, there is no need to thin the first epitaxial layer, ensuring the current generated by the first epitaxial layer. Additionally, by providing multiple protrusions, the surface area of ​​the metal reflective layer can be effectively increased, thereby improving the reflectivity of the metal reflective layer.

[0052] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] In the description of this invention, it should be understood that the terms "upper," "lower," "top surface," "bottom surface," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the indicated position or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations of the invention. Furthermore, the terms "first" and "second" are used only to distinguish an entity or operation from another entity or operation, and do not require or imply any actual relationship, order, or relative importance between these entities or operations.

[0054] Figures 2 to 9 This is a schematic diagram of the structure of each step in the method for forming a micro light-emitting pixel unit according to an embodiment of the present invention.

[0055] The first epitaxial layer, the multiple quantum layer, and the second epitaxial layer are formed. Please refer to [reference needed] for the detailed formation process. Figures 2 to 4 .

[0056] Please refer to Figure 2 Provide temporary substrate 200.

[0057] In this embodiment, the temporary substrate 200 is an epitaxial substrate layer. The temporary substrate 200 is used as a temporary support structure in the flip-chip fabrication process of the micro light-emitting pixel unit. In the subsequent actual device structure fabrication process of the micro light-emitting pixel unit, the temporary substrate 200 needs to be removed.

[0058] Please refer to Figure 3 A second epitaxial material layer 201, a multi-quantum well material layer 202, and a first epitaxial material layer 203 are sequentially stacked on the temporary substrate 200.

[0059] In this embodiment, the first epitaxial material layer 203 is used to provide a material basis for forming the first epitaxial layer; the multi-quantum well material layer 202 is used to provide a material basis for forming the multi-quantum well layer; and the second epitaxial material layer 201 is used to provide a material basis for forming the second epitaxial layer.

[0060] In this embodiment, the first epitaxial material layer 203 contains a first doped ion, and the second epitaxial material layer 201 contains a second doped ion. The first doped ion and the second doped ion have different electrical types.

[0061] In this embodiment, the electrical type of the first doped ion is P-type, and the electrical type of the second doped ion is N-type.

[0062] In other embodiments, the electrical type of the first doped ion may also be N-type, and the electrical type of the second doped ion may be P-type.

[0063] In this embodiment, the materials of the first epitaxial material layer 203 and the second epitaxial material layer 201 can be gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium indium phosphide (AlGaInP) or other III-V group semiconductor materials.

[0064] In this embodiment, the material of the multi-quantum well material layer 202 can be gallium nitride, indium gallium nitride, aluminum indium phosphide (AlGaP) or gallium indium phosphide (GaInP), wherein gallium nitride and indium gallium nitride are used to generate blue or green light, and indium gallium nitride, aluminum indium phosphide and gallium indium phosphide are used to generate red light.

[0065] Please refer to Figure 4 The second epitaxial material layer 201, the multi-quantum well material layer 202 and the first epitaxial material layer 203 are patterned and etched to form the second epitaxial layer 204, the multi-quantum well layer 205 and the first epitaxial layer 206.

[0066] In this embodiment, the first epitaxial layer 206 is formed by patterning and etching the first epitaxial material layer 203. Therefore, the material of the first epitaxial layer 206 is also gallium nitride, indium gallium nitride, aluminum gallium indium phosphide, or other III-V semiconductor materials, and the first doped ions are also present in the first epitaxial layer 206. The multi-quantum well layer 205 is formed by patterning and etching the multi-quantum well material layer 202. Therefore, the material of the multi-quantum well layer 205 is also gallium nitride, indium gallium nitride, aluminum indium phosphide, or gallium indium phosphide. The second epitaxial layer 204 is formed by patterning and etching the second epitaxial material layer 201. Therefore, the material of the second epitaxial layer 204 is also gallium nitride, indium gallium nitride, aluminum gallium indium phosphide, or other III-V semiconductor materials, and the second doped ions are also present in the second epitaxial layer 204.

[0067] The first epitaxial layer 206 has a first side 206a and a second side 206b. The multi-quantum well layer 205 and the second epitaxial layer 204 are located on the first side 206a. The multi-quantum well layer 205 is located between the first epitaxial layer 206 and the second epitaxial layer 204, and is in contact with the first epitaxial layer 206 and the second epitaxial layer 204, respectively.

[0068] It should be noted that, in this embodiment, the first side 206a is the front side of the micro-light-emitting pixel unit, and the second side 206b is the back side of the micro-light-emitting pixel unit. The first epitaxial layer 206 and the second epitaxial layer 204 serve as the positive and negative electrodes of the micro-light-emitting pixel unit, respectively.

[0069] Please refer to Figure 5 An ohmic contact layer 207 is formed on the second side 206b, and the ohmic contact layer 207 is in contact with the first epitaxial layer 206.

[0070] In this embodiment, the ohmic contact layer 207 has a plurality of recesses 2071.

[0071] In this embodiment, the method for forming the ohmic contact layer 207 includes: forming an initial ohmic contact layer (not shown) on the second side 206b (the surface of the first epitaxial layer 206); performing a patterned etching process on the initial ohmic contact layer to form the ohmic contact layer 207, wherein the ohmic contact layer 207 has a plurality of the recesses 2071.

[0072] In this embodiment, the ohmic contact layer 207 is made of a transparent conductive material, including transparent metal materials or transparent conductive oxide materials. The transparent conductive oxide material can be, but is not limited to, an N-type oxide semiconductor, and is preferably indium tin oxide (ITO). The material of the ohmic contact layer 207 needs to balance the conductivity of a metal to ensure the electrical connection requirements of the first epitaxial layer 206, while also being transparent to prevent obstruction of light emitted from the multi-quantum-well layer 205.

[0073] Please refer to Figure 6 After the ohmic contact layer 207 is formed, a passivation layer 208 is formed on the second side 206b.

[0074] In this embodiment, the passivation layer 208 covers the exposed surfaces of the first epitaxial layer 206, the multiple quantum well layer 205, and the second epitaxial layer 204, and the passivation layer 208 exposes the surface of the ohmic contact layer 207.

[0075] In this embodiment, the passivation layer 208 mainly serves as electrical isolation and device protection. The passivation material layer can be an aluminum oxide film layer formed by an atomic layer deposition process with good step coverage.

[0076] In this embodiment, the material of the passivation layer 208 needs to balance insulation and light transmittance. The light transmittance is to reduce the obstruction of emitted light by the passivation layer 208. The material of the passivation layer 208 can be silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, or aluminum oxide.

[0077] Please refer to Figure 7 A metal reflective layer 209 is formed on the second side 206b, the metal reflective layer 209 is in contact with the ohmic contact layer 207, the ohmic contact layer 207 is located between the first epitaxial layer 206 and the metal reflective layer 209; wherein, the metal reflective layer 209 has a plurality of protrusions 2091, the protrusions 2091 extending into the ohmic contact layer 207.

[0078] By extending a plurality of the protrusions 2091 of the metal reflective layer 209 into the ohmic contact layer 207, the distance between the metal reflective layer 209 and the multi-quantum well layer 205 is reduced. This allows the plasma energy excited by the metal reflective layer 209 to penetrate the ohmic contact layer 207 and the first epitaxial layer 206, thereby enabling efficient coupling between the plasma energy excited by the metal reflective layer 209 and the light emitted by the multi-quantum well layer 205, thus increasing the light intensity of the micro-light-emitting pixel unit. Furthermore, there is no need to thin the first epitaxial layer 206, ensuring the current generated by the first epitaxial layer 206. Additionally, by providing multiple protrusions 2091, the surface area of ​​the metal reflective layer 209 can be effectively increased, thereby improving the reflective effect of the metal reflective layer 209.

[0079] In this embodiment, the metal reflective layer 209 covers the ohmic contact layer 207, and the metal contact layer fills a plurality of the recesses 2071 to form corresponding protrusions 2091.

[0080] In this embodiment, the method for forming the metal reflective layer 209 on the second side 206b (the surface of the passivation layer 208 and the ohmic contact layer 207) includes: forming a sacrificial layer (not shown) on the second side 206b; forming an initial metal reflective layer (not shown) on the second side 206b using a vapor deposition process, the initial metal reflective layer covering the surface of the sacrificial layer and the ohmic contact layer 207; and removing the sacrificial layer and the initial metal reflective layer on the surface of the sacrificial layer to form the metal reflective layer 209.

[0081] It should be noted that the sacrificial layer is used to pre-mask the locations where the metal reflective layer 209 should not form, and is then peeled off after the initial metal reflective layer 209 is formed. The material of the sacrificial layer can be a photoresist material.

[0082] In other embodiments, the method of forming the metal reflective layer on the second side may further include: forming an initial metal reflective layer on the second side using a vapor deposition process, the initial metal reflective layer covering the ohmic contact layer; and performing a patterned etching process on the initial metal reflective layer to form the metal reflective layer.

[0083] In this embodiment, the ohmic contact layer 207 and the metal reflective layer 209 are tightly bonded together, and the metal reflective layer 209 and the ohmic contact layer 207 have a structural intersection in the stacking direction. The tight bonding between the metal reflective layer 209 and the ohmic contact layer 207 can improve the overall strength of the device structure.

[0084] In this embodiment, the projection area of ​​the surface of the protrusion 2091 near the first epitaxial layer 206 toward the first epitaxial layer 206 is located within the projection area of ​​the surface of the protrusion 2091 away from the first epitaxial layer 206 toward the first epitaxial layer 206. By setting the side of the protrusion 2091 near the multi-quantum well layer 205 as a tip, more plasma energy excited by the metal reflective layer 209 accumulates at the tip, further enhancing the coupling effect between the plasma energy excited by the metal reflective layer 209 and the light emitted by the multi-quantum well layer 205.

[0085] In this embodiment, the structure of the protrusion 2091 can be a cone, pyramid, frustum, prism, or hemisphere.

[0086] In this embodiment, the height of the protrusion 2091 is less than or equal to the thickness of the ohmic contact layer 207, the thickness of the ohmic contact layer 207 is between 50nm and 100nm, and the height of the protrusion 2091 is between 40nm and 100nm.

[0087] In this embodiment, a plurality of the protrusions 2091 are arranged in an array. The array of protrusions 2091 is more uniformly distributed, further enhancing the coupling effect between the plasma energy excited by the metal reflective layer 209 and the light emitted by the multi-quantum well layer 205.

[0088] In this embodiment, the number of protrusions 2091 ranges from 70 to 120. Setting the number of protrusions 2091 within this range prevents both a small number of protrusions from affecting the coupling effect between the plasma energy excited by the metal reflective layer 209 and the light emitted by the multi-quantum well layer 205, and a large number of protrusions from increasing the manufacturing process difficulty.

[0089] In this embodiment, the material of the metal reflective layer 209 can be silver, aluminum, or gold. Silver has a plasma wavelength of approximately 136 nanometers, strong reflectivity, and is suitable for surface plasmon resonance (SPR) of blue or green light; gold has a plasma wavelength of approximately 200 nanometers, suitable for SPR of red or near-red light; and aluminum has a plasma wavelength of approximately 100 nanometers, suitable for SPR in the ultraviolet range.

[0090] Please refer to Figure 8 After the metal reflective layer 209 is formed, a conductive plug 210 is formed on the second side 206b. The conductive plug 210 is in contact with the metal reflective layer 209, and the metal reflective layer 209 is located between the ohmic contact layer 207 and the conductive plug 210.

[0091] In this embodiment, the method of forming the conductive plug 210 includes: forming an insulating layer 211 on the second side 206b, the insulating layer 211 covering the metal reflective layer 209; forming a plug opening (not shown) in the insulating layer 211, the plug opening exposing a portion of the surface of the metal reflective layer 209; and forming the conductive plug 210 in the plug opening.

[0092] In this embodiment, the material of the insulating layer 211 can be silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, or aluminum oxide.

[0093] In this embodiment, the conductive plug 210 may be made of copper.

[0094] In this embodiment, the conductive plug 210 is used to electrically connect the first epitaxial layer 206 to the provided driving backplane, and the driving backplane supplies power to the first epitaxial layer 206, thereby driving the pixel unit to emit light.

[0095] Please refer to Figure 9 After forming the conductive plug 210, the temporary substrate 200 is removed to expose the second epitaxial layer 204; after removing the temporary substrate 200, a microlens 212 is formed on the first side 206a, and the projection region of the multi-quantum well layer 205 toward the first epitaxial layer 206 is located within the projection region of the microlens 212 toward the first epitaxial layer 206.

[0096] In this embodiment, before forming the microlens 212, an ohmic contact layer (not shown) needs to be formed on the second epitaxial layer 204 to reduce the contact resistance of the second epitaxial layer 204.

[0097] In this embodiment, the material of the microlens 212 can be silicon oxide or silicon nitride.

[0098] In this embodiment, the microlens 212 is hemispherical in shape, and the hemispherical structure can further improve the light emission efficiency of the micro light-emitting pixel unit.

[0099] Please continue to refer to this. Figure 9 In this embodiment, before forming the microlens 212, an epitaxial electrode 213 is formed on the first side 206a, and the epitaxial electrode 213 is electrically connected to the second epitaxial layer 204.

[0100] In this embodiment, the material of the epitaxial electrode 213 can be gold, silver or copper.

[0101] It should be noted that, in this embodiment, an ohmic contact layer (not shown) of indium tin oxide material is added between the epitaxial electrode 213 and the second epitaxial layer 204, and between the epitaxial electrode 213 and the microlens 212. The epitaxial electrode 213 is distributed in the channel between the pixel units to compensate for the current spread of indium tin oxide.

[0102] Accordingly, this embodiment of the invention also provides a miniature light-emitting pixel unit, please refer to [further details]. Figure 9 The method includes: a first epitaxial layer 206 having opposing first sides 206a and second sides 206b; a multi-quantum well layer 205 located on the first side 206a, the multi-quantum well layer 205 being in contact with the first epitaxial layer 206; a second epitaxial layer 204 located on the first side 206a, the multi-quantum well layer 205 being located between the first epitaxial layer 206 and the second epitaxial layer 204; an ohmic contact layer 207 located on the second side 206b, the ohmic contact layer 207 being in contact with the first epitaxial layer 206; and a metal reflective layer 209 located on the second side 206b, the metal reflective layer 209 being in contact with the ohmic contact layer 207, the ohmic contact layer 207 being located between the first epitaxial layer 206 and the metal reflective layer 209; wherein the metal reflective layer 209 has a plurality of protrusions 2091 extending into the ohmic contact layer 207.

[0103] By extending a plurality of the protrusions 2091 of the metal reflective layer 209 into the ohmic contact layer 207, the distance between the metal reflective layer 209 and the multi-quantum well layer 205 is reduced. This allows the plasma energy excited by the metal reflective layer 209 to penetrate the ohmic contact layer 207 and the first epitaxial layer 206, thereby enabling efficient coupling between the plasma energy excited by the metal reflective layer 209 and the light emitted by the multi-quantum well layer 205, thus increasing the light intensity of the micro-light-emitting pixel unit. Furthermore, there is no need to thin the first epitaxial layer 206, ensuring the current generated by the first epitaxial layer 206. Additionally, by providing multiple protrusions 2091, the surface area of ​​the metal reflective layer 209 can be effectively increased, thereby improving the reflective effect of the metal reflective layer 209.

[0104] In this embodiment, the materials of the first epitaxial layer 206 and the second epitaxial layer 204 can be gallium nitride, indium gallium nitride, aluminum gallium indium phosphide, or other III-V group semiconductor materials.

[0105] In this embodiment, the material of the multiple quantum well layer 205 can be gallium nitride, indium gallium nitride, aluminum indium phosphide, or gallium indium phosphide. Among them, gallium nitride and indium gallium nitride are used to generate blue or green light, while indium gallium nitride, aluminum indium phosphide, and gallium indium phosphide are used to generate red light.

[0106] In this embodiment, the projection area of ​​the surface of the protrusion 2091 near the first epitaxial layer 206 toward the first epitaxial layer 206 is located within the projection area of ​​the surface of the protrusion 2091 away from the first epitaxial layer 206 toward the first epitaxial layer 206. By setting the side of the protrusion 2091 near the multi-quantum well layer 205 as a tip, more plasma energy excited by the metal reflective layer 209 accumulates at the tip, further enhancing the coupling effect between the plasma energy excited by the metal reflective layer 209 and the light emitted by the multi-quantum well layer 205.

[0107] In this embodiment, the structure of the protrusion 2091 can be a cone, pyramid, frustum, prism, or hemisphere.

[0108] In this embodiment, a plurality of the protrusions 2091 are arranged in an array. The array of protrusions 2091 is more uniformly distributed, further enhancing the coupling effect between the plasma energy excited by the metal reflective layer 209 and the light emitted by the multi-quantum well layer 205.

[0109] In this embodiment, the number of protrusions 2091 ranges from 70 to 120. Setting the number of protrusions 2091 within this range prevents both a small number of protrusions from affecting the coupling effect between the plasma energy excited by the metal reflective layer 209 and the light emitted by the multi-quantum well layer 205, and a large number of protrusions from increasing the manufacturing process difficulty.

[0110] In this embodiment, the ohmic contact layer 207 has a plurality of recesses 2071 that match the protrusions 2091, and the ohmic contact layer 207 is tightly bonded to the metal reflective layer 209. The tight bond between the metal reflective layer 209 and the ohmic contact layer 207 can improve the overall strength of the device structure.

[0111] In this embodiment, the height of the protrusion 2091 is less than or equal to the thickness of the ohmic contact layer 207, the thickness of the ohmic contact layer 207 is between 50nm and 100nm, and the height of the protrusion 2091 is between 40nm and 100nm.

[0112] In this embodiment, the ohmic contact layer 207 is made of a transparent conductive material, including transparent metal materials or transparent conductive oxide materials. The transparent conductive oxide material can be, but is not limited to, an N-type oxide semiconductor, and is preferably indium tin oxide (ITO). The material of the ohmic contact layer 207 needs to balance the conductivity of a metal to ensure the electrical connection requirements of the first epitaxial layer 206, while also being transparent to prevent obstruction of light emitted from the multi-quantum-well layer 205.

[0113] In this embodiment, the material of the metal reflective layer 209 can be silver, aluminum, or gold. Silver has a plasma wavelength of approximately 136 nanometers, strong reflectivity, and is suitable for surface plasmon resonance (SPR) of blue or green light; gold has a plasma wavelength of approximately 200 nanometers, suitable for SPR of red or near-red light; and aluminum has a plasma wavelength of approximately 100 nanometers, suitable for SPR in the ultraviolet range.

[0114] In this embodiment, a conductive plug 210 is further included, located on the second side 206b. The conductive plug 210 contacts the metal reflective layer 209, which is situated between the ohmic contact layer 207 and the conductive plug 210. The conductive plug 210 is used to electrically connect the first epitaxial layer 206 to the provided driving backplane, thereby supplying power to the first epitaxial layer 206 and driving the pixel unit to emit light.

[0115] In this embodiment, the conductive plug 210 may be made of copper.

[0116] In this embodiment, it further includes a microlens 212 located on the first side 206a, wherein the projection region of the multi-quantum well layer 205 toward the first epitaxial layer 206 is located within the projection region of the microlens 212 toward the first epitaxial layer 206.

[0117] In this embodiment, the microlens 212 is hemispherical in shape, and the hemispherical structure can further improve the light emission efficiency of the micro light-emitting pixel unit.

[0118] Accordingly, this invention also provides a miniature light-emitting diode chip, please refer to the following embodiments. Figure 9 It includes: a plurality of micro light-emitting pixel units as described in any of the above embodiments; a driving backplate (not shown), wherein the plurality of micro light-emitting pixel units are electrically connected to the driving backplate respectively.

[0119] Accordingly, this embodiment of the invention also provides a micro-display panel, including the micro-light-emitting diode chip described in the above embodiments. The micro-display panel has a very small volume, with length and width dimensions between 500 μm and 50000 μm. The light-emitting area of ​​the micro-display panel is very small, such as 1 mm × 1 mm, 2.64 mm × 2.02 mm, 3 mm × 5 mm, etc. The light-emitting area of ​​the micro-display panel includes multiple micro-LED pixels arranged in an array, specifically in a pixel arrangement of 320 × 240, 640 × 480, 1600 × 1200, 1920 × 1080, or 2560 × 1440. The size of a single micro-LED pixel is between 100 nm and 100 micrometers. In some embodiments, the size of a single micro-LED pixel is between 150 nm and 15 micrometers. In some embodiments, the size of a single micro-LED pixel can be less than 10 micrometers.

[0120] A driving backplane is disposed on the back of the micro-LED pixel array. The driving backplane is electrically connected to the micro-LEDs in the micro-LED pixel array. The driving backplane can acquire signals such as image data from the outside world and can control the corresponding micro-LEDs to emit light or not emit light. The driving backplane is a TFT (Thin Film Transistor) board or an IC (Integrated Circuit) board. For example, the driving backplane of the micro-display panel described above integrates a frame buffer, a column driving circuit, and a row driving circuit. The frame buffer includes a first pixel storage area, and the micro-LED pixel array includes a second pixel storage area. A complete frame of pixel grayscale data from the outside world can first enter the first pixel storage area of ​​the frame buffer. The column driving circuit can load the pixel grayscale data in the first pixel storage area of ​​the frame buffer into the second pixel storage area of ​​the micro-LED pixel array. The row driving circuit can scan the pixel grayscale data in the second pixel storage area and generate a pulse modulation signal to achieve the purpose of displaying different grayscale levels. When driving multiple micro-LED pixels in the micro-LED pixel array, either a single pixel can be driven independently, or multiple pixel units can be driven independently. The specific driving method should not constitute a limitation of this application.

[0121] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A micro light emitting pixel unit, characterized by, include: A first epitaxial layer, the first epitaxial layer having opposing first and second sides; A multi-quantum well layer located on the first side, the multi-quantum well layer being in contact with the first epitaxial layer; The second epitaxial layer is located on the first side, and the multi-quantum well layer is located between the first epitaxial layer and the second epitaxial layer; An ohmic contact layer is located on the second side, and the ohmic contact layer is in contact with the first epitaxial layer; a metal reflective layer is located on the second side, and the metal reflective layer is in contact with the ohmic contact layer. The ohmic contact layer is located between the first epitaxial layer and the metal reflective layer; wherein the metal reflective layer has a plurality of protrusions that extend into the ohmic contact layer.

2. The micro light emitting pixel unit of claim 1, wherein, The projection area of ​​the protrusion near the first epitaxial layer toward the first epitaxial layer is located within the projection area of ​​the protrusion away from the first epitaxial layer toward the first epitaxial layer.

3. The micro light emitting pixel unit of claim 2, wherein, The structure of the protrusion includes: a cone, a pyramid, a frustum, or a hemisphere.

4. The micro light emitting pixel unit of claim 1, wherein, Several of the protrusions are arranged in an array.

5. The micro light emitting pixel unit of claim 1, wherein, The number of protrusions ranges from 70 to 120.

6. The micro light emitting pixel unit of claim 1, wherein, The ohmic contact layer has a plurality of recesses that match the protrusions, and the ohmic contact layer is tightly bonded to the metal reflective layer.

7. The micro light emitting pixel unit of claim 1, wherein, The ohmic contact layer is made of a transparent conductive material, which includes transparent metal materials or transparent conductive oxide materials.

8. The micro light emitting pixel unit of claim 1, wherein, The material of the metal reflective layer includes silver, aluminum, or gold.

9. The micro light emitting pixel unit of claim 1, wherein, Also includes: A conductive plug is located on the second side, the conductive plug is in contact with the metal reflective layer, and the metal reflective layer is located between the ohmic contact layer and the conductive plug.

10. The micro light emitting pixel unit of claim 9, wherein, The material of the conductive plug includes copper.

11. The micro light emitting pixel unit of claim 1, wherein, Also includes: The microlens located on the first side has a projection region of the multi-quantum well layer toward the first epitaxial layer within the projection region of the microlens toward the first epitaxial layer.

12. The micro light emitting pixel unit of claim 1, wherein, The height of the protrusion is less than or equal to the thickness of the ohmic contact layer, the thickness of the ohmic contact layer is between 50nm and 100nm, and the height of the protrusion is between 40nm and 100nm.

13. The micro light emitting pixel unit of claim 1, wherein, The materials of the first epitaxial layer and the second epitaxial layer include gallium nitride, indium gallium nitride, or aluminum gallium indium phosphide.

14. The micro light emitting pixel unit of claim 1, wherein, The materials of the multiple quantum well layers include gallium nitride, indium gallium nitride, aluminum indium phosphide, or gallium indium phosphide.

15. A method of forming a micro light emitting pixel unit, comprising: include: A first epitaxial layer is formed, the first epitaxial layer having opposing first and second sides; A multi-quantum-well layer is formed on the first side, and the multi-quantum-well layer is in contact with the first epitaxial layer; A second epitaxial layer is formed on the first side, and the multiple quantum well layer is located between the first epitaxial layer and the second epitaxial layer; An ohmic contact layer is formed on the second side, and the ohmic contact layer is in contact with the first epitaxial layer; a metal reflective layer is formed on the second side, and the metal reflective layer is in contact with the ohmic contact layer, and the ohmic contact layer is located between the first epitaxial layer and the metal reflective layer; wherein the metal reflective layer has a plurality of protrusions, and the protrusions extend into the ohmic contact layer.

16. The method of claim 15, wherein the micro light emitting pixel unit is formed by a process comprising: The projection area of ​​the protrusion near the first epitaxial layer toward the first epitaxial layer is located within the projection area of ​​the protrusion away from the first epitaxial layer toward the first epitaxial layer.

17. The method of claim 16, wherein the micro light emitting pixel unit is formed by a process comprising: The structure of the protrusion includes: a cone, a pyramid, a frustum, or a hemisphere.

18. The method for forming a micro-light-emitting pixel unit according to claim 15, characterized in that, Several of the protrusions are arranged in an array.

19. The method for forming a micro-light-emitting pixel unit according to claim 15, characterized in that, The number of protrusions ranges from 70 to 120.

20. The method for forming a micro-light-emitting pixel unit according to claim 15, characterized in that, The ohmic contact layer has a plurality of recesses that match the protrusions, and the ohmic contact layer is tightly bonded to the metal reflective layer.

21. The method for forming a micro-light-emitting pixel unit according to claim 20, characterized in that, The method for forming the ohmic contact layer and the metal reflective layer includes: forming an initial ohmic contact layer on the second side; performing a patterned etching process on the initial ohmic contact layer to form the ohmic contact layer, wherein the ohmic contact layer has a plurality of the recesses; forming the metal reflective layer on the second side, wherein the metal reflective layer covers the ohmic contact layer, and the metal contact layer fills the plurality of the recesses to form corresponding protrusions.

22. The method for forming a micro-light-emitting pixel unit according to claim 21, characterized in that, The method of forming the metal reflective layer on the second side includes: forming a sacrificial layer on the second side; forming an initial metal reflective layer on the second side using a vapor deposition process, the initial metal reflective layer covering the surface of the sacrificial layer and the ohmic contact layer; and removing the sacrificial layer and the initial metal reflective layer on the surface of the sacrificial layer to form the metal reflective layer.

23. The method for forming a micro-light-emitting pixel unit according to claim 21, characterized in that, The method for forming the metal reflective layer on the second side includes: forming an initial metal reflective layer on the second side using a vapor deposition process, the initial metal reflective layer covering the ohmic contact layer; and performing a patterned etching process on the initial metal reflective layer to form the metal reflective layer.

24. The method for forming a micro-light-emitting pixel unit according to claim 15, characterized in that, Also includes: A conductive plug is formed on the second side, the conductive plug being in contact with the metal reflective layer, the metal reflective layer being located between the ohmic contact layer and the conductive plug.

25. The method for forming a micro-light-emitting pixel unit according to claim 15, characterized in that, Also includes: A microlens is formed on the first side, and the projection region of the multi-quantum well layer toward the first epitaxial layer is located within the projection region of the microlens toward the first epitaxial layer.

26. A miniature light-emitting diode chip, characterized in that, include: Several micro-luminescent pixel units as described in any one of claims 1 to 14; A driving backplate, wherein several of the micro light-emitting pixel units are electrically connected to the driving backplate.

27. A micro-display panel, characterized in that, Including the micro light-emitting diode chip as described in claim 26.

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