Miniature LED pixel with alloy reflection structure

Abstract

The invention relates to the technical field of micro light emitting diodes (Micro-LEDs), and provides a micro LED pixel with an alloy reflection structure, which comprises an LED structure, an alloy reflection structure and an alloy reflection structure, the metal layer is located below the LED structure, the metal layer comprises an alloy reflecting layer, and the alloy reflecting layer is made of aluminum alloy or silver alloy. The aluminum alloy or the silver alloy is used as the reflecting layer, so that the oxidation resistance of the reflecting layer and the stability between the reflecting layer and the conductive layer can be remarkably improved.

Description

Technical Field

[0001] This invention generally relates to the field of micro-light-emitting diode (Micro-LED) technology. Specifically, this invention relates to a micro-LED pixel having an alloy reflective structure. Background Technology

[0002] Micro-LED is an emerging flat panel display technology. It consists of countless tiny LEDs, each LED being a pixel. These pixels are extremely small, typically only tens of micrometers or even smaller. Compared to traditional LCD and OLED displays, Micro-LED offers advantages such as higher brightness, faster response time, wider color gamut, and longer lifespan.

[0003] In Micro-LED chips, ITO is a commonly used ohmic contact material, and SiO2 is a commonly used passivation layer material for blue-green Micro-LEDs. Al and Ag, as high-reflectivity materials, are good choices for reflective layers. However, because Al reacts with ITO at high temperatures, diffuses clusters, and oxidizes, producing some rough and irregular products and reducing reflectivity, it is difficult to use them with ITO. In addition, during high-temperature oxygen deposition, silver is prone to oxidation, diffusion, and silver ion migration.

[0004] In view of the above problems, Chinese patent CN115832144A in the prior art proposes a flip-chip Micro-LED with a p-reflective electrode and its fabrication method. In this method, to suppress the decrease in reflectivity caused by diffusion clusters and oxidation of metallic silver or aluminum during chip fabrication and use, a metal material with high tensile stress is used as a barrier layer to cover the surface and sides of the underlying active metal, thereby suppressing diffusion clusters and oxidation of the underlying active metal. However, the addition of the barrier layer will significantly reduce the reflectivity of Al and Ag themselves. Summary of the Invention

[0005] To at least partially solve the aforementioned problems in the prior art, the present invention proposes a micro LED pixel with an alloy reflective structure, comprising: LED structure; and A metal layer located beneath the LED structure, wherein the metal layer includes an alloy reflective layer, and the alloy reflective layer is an aluminum alloy or a silver alloy.

[0006] In one embodiment of the present invention, the alloy reflective layer is connected to the LED structure.

[0007] In one embodiment of the present invention, the aluminum alloy includes AlCu, AlSi, AlMg, AlNi, AlSn and AlMn.

[0008] In one embodiment of the present invention, the silver alloy includes AgCu, AgNi, AgZn, AgPd, AgMg, and AgW.

[0009] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An adhesive layer located between the alloy reflective layer and the LED structure.

[0010] In one embodiment of the invention, the material of the adhesive layer includes Cr or Ti.

[0011] In one embodiment of the present invention, the LED structure includes a lower conductive layer, an upper conductive layer, and an LED light-emitting layer between the lower conductive layer and the upper conductive layer.

[0012] In one embodiment of the present invention, the LED light-emitting layer includes a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer between the first semiconductor epitaxial layer and the second semiconductor epitaxial layer.

[0013] In one embodiment of the present invention, the first semiconductor epitaxial layer is P-type and the second semiconductor epitaxial layer is N-type; or the first semiconductor epitaxial layer is N-type and the second semiconductor epitaxial layer is P-type; the material of the first semiconductor epitaxial layer is a Ga-containing III-V group semiconductor material; the light-emitting layer includes a multi-quantum well layer.

[0014] In one embodiment of the present invention, the lower conductive layer and the upper conductive layer are transparent conductive layers.

[0015] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A substrate, wherein the LED structure is bonded to the substrate via the metal layer.

[0016] In one embodiment of the present invention, the metal layer further includes a connection portion between the metal layer and a contact on the substrate, the connection portion being electrically connected between the metal layer and the contact on the substrate.

[0017] In one embodiment of the present invention, the material of the connecting part is a metal, including one or more of Al, Au, Rh, Ag, Cr, Ti, Pt, Sn, Cu, AuSn, and TiW.

[0018] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A conductive layer located above the LED structure, wherein the conductive layer electrically connects multiple LED structures.

[0019] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A metal structure located above and electrically connected to the conductive layer, wherein the metal structure is located in the gap between multiple LED structures.

[0020] In one embodiment of the invention, the metal structure serves as a common electrode for connecting each LED structure.

[0021] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An insulating medium, wherein the LED structure is embedded within the insulating medium.

[0022] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: Microlenses located on the top surface of the conductive layer and the metal structure.

[0023] The present invention also proposes a micro LED pixel with an alloy reflective structure, comprising: LED structure; An alloy reflective layer located below the LED structure for reflecting the light emitted by the LED structure, wherein the alloy reflective layer is an aluminum alloy or a silver alloy.

[0024] In one embodiment of the present invention, the alloy reflective layer is connected to the LED structure.

[0025] In one embodiment of the present invention, the aluminum alloy includes AlCu, AlSi, AlMg, AlNi, AlSn and AlMn.

[0026] In one embodiment of the present invention, the silver alloy includes AgCu, AgNi, AgZn, AgPd, AgMg, and AgW.

[0027] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An adhesive layer located between the alloy reflective layer and the LED structure.

[0028] In one embodiment of the invention, the material of the adhesive layer includes Cr or Ti.

[0029] In one embodiment of the present invention, the LED structure includes a conductive layer and an LED light-emitting layer located on the conductive layer.

[0030] In one embodiment of the present invention, the LED light-emitting layer includes a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer between the first semiconductor epitaxial layer and the second semiconductor epitaxial layer.

[0031] In one embodiment of the present invention, the first semiconductor epitaxial layer is P-type and the second semiconductor epitaxial layer is N-type; or the first semiconductor epitaxial layer is N-type and the second semiconductor epitaxial layer is P-type; the material of the first semiconductor epitaxial layer is a Ga-containing III-V group semiconductor material; the light-emitting layer includes a multi-quantum well layer.

[0032] In one embodiment of the present invention, the second semiconductor epitaxial layer in the LED structure of the plurality of micro LED pixels is integrated.

[0033] In one embodiment of the present invention, the conductive layer includes a metal layer or a transparent conductive layer.

[0034] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: The substrate located below the LED structure.

[0035] In one embodiment of the present invention, the LED structure is bonded to the substrate through a bonding portion between the conductive layer of the LED structure and the contacts on the substrate, and is electrically connected to the conductive layer and the contacts on the substrate.

[0036] In one embodiment of the present invention, the material of the bonding portion includes one or more of Al, Au, Rh, Ag, Cr, Ti, Pt, Sn, Cu, AuSn, and TiW.

[0037] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A passivation layer located between the reflective layer and the LED light-emitting layer of the LED structure.

[0038] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An insulating medium is filled between the alloy reflective layer and the substrate.

[0039] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A metal structure located above the gaps between multiple LED structures, the metal structure being electrically connected to a second semiconductor epitaxial layer of the LED structures.

[0040] In one embodiment of the present invention, the micro LED pixel with an alloy reflective structure according to claim 15, wherein the material of the metal structure is an aluminum alloy or a silver alloy.

[0041] In one embodiment of the invention, a gap is formed between adjacent microLED structures; the metal structure is formed at the bottom of the gap; or The tops of adjacent microLED structures are interconnected to form an interconnect top; gaps are formed between adjacent microLED structures and below the interconnect top; the metal structure is formed on top of the interconnect top and around the top of the microLED structure.

[0042] In one embodiment of the present invention, there is more than one microLED structure; the microLED structures are stacked in a vertical direction; interconnect conductive structures are perpendicular to the bottom of the microLED structures; each interconnect conductive structure is connected to the bottom of each microLED.

[0043] In one embodiment of the invention, the metal layer is formed on the sidewall surface of the interconnect conductive structure.

[0044] In one embodiment of the invention, the metal layer covers the entire surface of the interconnect conductive structure.

[0045] In one embodiment of the present invention, the metal structure serves as a reflector to reflect the light emitted by the LED structure.

[0046] In one embodiment of the present invention, the metal structure is an alloy reflective layer.

[0047] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: Microlenses located on the top surface of the LED structure.

[0048] The present invention also proposes a micro LED pixel with an alloy reflective structure, comprising: First LED structure; The second LED structure located above the first LED structure; and A metal layer located below the first LED structure, wherein the metal layer includes an alloy reflective layer, and the alloy reflective layer is an aluminum alloy or a silver alloy.

[0049] In one embodiment of the present invention, the alloy reflective layer is connected to the first LED structure.

[0050] In one embodiment of the present invention, the aluminum alloy includes AlCu, AlSi, AlMg, AlNi, AlSn and AlMn.

[0051] In one embodiment of the present invention, the silver alloy includes AgCu, AgNi, AgZn, AgPd, AgMg, and AgW.

[0052] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An adhesive layer located between the alloy reflective layer and the first LED structure.

[0053] In one embodiment of the invention, the material of the adhesive layer includes Cr or Ti.

[0054] In one embodiment of the present invention, the first LED structure includes a lower conductive layer, an upper conductive layer, and an LED light-emitting layer between the lower conductive layer and the upper conductive layer; The second LED structure includes a lower conductive layer, an upper conductive layer, and an LED light-emitting layer between the lower conductive layer and the upper conductive layer.

[0055] In one embodiment of the present invention, the upper conductive layer of the first LED structure is electrically connected to the upper conductive layer of the second LED structure.

[0056] In one embodiment of the present invention, the LED light-emitting layer includes a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer between the first semiconductor epitaxial layer and the second semiconductor epitaxial layer.

[0057] In one embodiment of the present invention, the first semiconductor epitaxial layer is P-type and the second semiconductor epitaxial layer is N-type; or the first semiconductor epitaxial layer is N-type and the second semiconductor epitaxial layer is P-type; the material of the first semiconductor epitaxial layer is a Ga-containing III-V group semiconductor material; the light-emitting layer includes a multi-quantum well layer.

[0058] In one embodiment of the present invention, the upper conductive layer and the lower conductive layer comprise a metal layer or a transparent conductive layer.

[0059] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A substrate located below the first LED structure, wherein the first LED structure is bonded to the substrate via the metal layer.

[0060] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An insulating medium, wherein the first LED structure and the second LED structure are embedded within the insulating medium.

[0061] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A metal structure, wherein the metal structure connects the lower conductive layer of the second LED structure to the metal bonding layer.

[0062] In one embodiment of the present invention, the metal structure includes an alloy reflective layer located on the sidewall of the metal structure.

[0063] The present invention also proposes a micro LED pixel with an alloy reflective structure, comprising: First LED structure; A second LED structure located above the first LED structure, wherein the color of the light emitted by the first LED structure is different from the color of the light emitted by the second LED structure; and A metal layer located below the first LED structure, wherein the metal layer includes an alloy reflective layer, and the alloy reflective layer is an aluminum alloy or a silver alloy.

[0064] In one embodiment of the present invention, the alloy reflective layer is connected to the first LED structure.

[0065] In one embodiment of the present invention, the aluminum alloy includes AlCu, AlSi, AlMg, AlNi, AlSn and AlMn.

[0066] In one embodiment of the present invention, the silver alloy includes AgCu, AgNi, AgZn, AgPd, AgMg, and AgW.

[0067] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An adhesive layer located between the alloy reflective layer and the first LED structure.

[0068] In one embodiment of the invention, the material of the adhesive layer includes Cr or Ti.

[0069] In one embodiment of the present invention, the first LED structure includes a lower conductive layer, an upper conductive layer, and a first color LED emitting layer between the lower conductive layer and the upper conductive layer; The second LED structure includes: a lower conductive layer, an upper conductive layer, and a second color LED emitting layer between the lower conductive layer and the upper conductive layer.

[0070] In one embodiment of the present invention, the LED light-emitting layer includes a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer between the first semiconductor epitaxial layer and the second semiconductor epitaxial layer.

[0071] In one embodiment of the present invention, the first semiconductor epitaxial layer is P-type and the second semiconductor epitaxial layer is N-type; or the first semiconductor epitaxial layer is N-type and the second semiconductor epitaxial layer is P-type; the material of the first semiconductor epitaxial layer is a Ga-containing III-V group semiconductor material; the light-emitting layer includes a multi-quantum well layer.

[0072] In one embodiment of the present invention, the upper conductive layer and the lower conductive layer comprise a metal layer or a transparent conductive layer.

[0073] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A substrate located below the first LED structure, wherein the first LED structure is bonded to the substrate via the metal layer.

[0074] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An insulating medium, wherein the first LED structure and the second LED structure are embedded within the insulating medium.

[0075] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: Multiple metal structures are arranged around the first LED structure and the second LED structure.

[0076] In one embodiment of the present invention, the plurality of metal structures include an alloy reflective layer located on the sidewalls of the plurality of metal structures.

[0077] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: Microlenses located on the top surface of the second LED structure.

[0078] The present invention also proposes a micro LED pixel with an alloy reflective structure, comprising: First LED structure; The second LED structure is located above the first LED structure; A third LED structure located above the second LED structure; and A metal layer located below the first LED structure, wherein the metal layer includes an alloy reflective layer, and the alloy reflective layer is an aluminum alloy or a silver alloy.

[0079] In one embodiment of the present invention, the alloy reflective layer is connected to the first LED structure.

[0080] In one embodiment of the present invention, the aluminum alloy includes AlCu, AlSi, AlMg, AlNi, AlSn and AlMn.

[0081] In one embodiment of the present invention, the silver alloy includes AgCu, AgNi, AgZn, AgPd, AgMg, and AgW.

[0082] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An adhesive layer located between the alloy reflective layer and the LED structure.

[0083] In one embodiment of the invention, the material of the adhesive layer includes Cr or Ti.

[0084] In one embodiment of the present invention, the first LED structure includes a lower conductive layer, an upper conductive layer, and a first color LED emitting layer between the lower conductive layer and the upper conductive layer; The second LED structure includes a lower conductive layer, an upper conductive layer, and a second color LED emitting layer between the lower conductive layer and the upper conductive layer; The third LED structure includes a lower conductive layer, an upper conductive layer, and a third color LED emitting layer between the lower conductive layer and the upper conductive layer.

[0085] In one embodiment of the present invention, the LED light-emitting layer includes a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer between the first semiconductor epitaxial layer and the second semiconductor epitaxial layer.

[0086] In one embodiment of the present invention, the first semiconductor epitaxial layer is P-type and the second semiconductor epitaxial layer is N-type; or the first semiconductor epitaxial layer is N-type and the second semiconductor epitaxial layer is P-type; the material of the first semiconductor epitaxial layer is a Ga-containing III-V group semiconductor material; the light-emitting layer includes a multi-quantum well layer.

[0087] In one embodiment of the present invention, the first LED structure further includes an upper connecting portion between the upper conductive layer and the LED light-emitting layer, and electrically connected to the upper conductive layer and the LED light-emitting layer.

[0088] In one embodiment of the present invention, the upper conductive layer and the lower conductive layer comprise a metal layer or a transparent conductive layer.

[0089] In one embodiment of the present invention, the area of ​​the LED light-emitting layer of the first LED structure is equal to or greater than the area of ​​the LED light-emitting layer of the first LED structure. The area of ​​the LED light-emitting layer of the first LED structure is equal to or greater than the area of ​​the LED light-emitting layer of the third LED structure.

[0090] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A substrate located below the first LED structure, wherein the first LED structure is bonded to the substrate via the metal layer.

[0091] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An insulating medium, wherein the first LED structure, the second LED structure, and the third LED structure are embedded within the insulating medium.

[0092] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: Multiple metal structures are arranged around the first LED structure, the second LED structure, and the third LED structure.

[0093] In one embodiment of the present invention, the plurality of metal structures include an alloy reflective layer located on the sidewalls of the plurality of metal structures.

[0094] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: Microlenses located on the top surface of the third LED structure.

[0095] The present invention also proposes a micro LED pixel with an alloy reflective structure, comprising: First LED structure; Second LED structure; A third LED structure, wherein the first LED structure, the second LED structure, and the third LED structure are offset from each other at the top; and A metal layer located below the first LED structure, wherein the metal layer includes an alloy reflective layer, and the alloy reflective layer is an aluminum alloy or a silver alloy.

[0096] In one embodiment of the present invention, the alloy reflective layer is connected to the first LED structure.

[0097] In one embodiment of the present invention, the aluminum alloy includes AlCu, AlSi, AlMg, AlNi, AlSn and AlMn.

[0098] In one embodiment of the present invention, the silver alloy includes AgCu, AgNi, AgZn, AgPd, AgMg, and AgW.

[0099] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An adhesive layer located between the alloy reflective layer and the first LED structure.

[0100] In one embodiment of the invention, the material of the adhesive layer includes Cr or Ti.

[0101] In one embodiment of the present invention, the first LED structure includes a lower conductive layer, an upper conductive layer, and a first color LED emitting layer between the lower conductive layer and the upper conductive layer; The second LED structure includes a lower conductive layer, an upper conductive layer, and a second color LED emitting layer between the lower conductive layer and the upper conductive layer; The third LED structure includes a lower conductive layer, an upper conductive layer, and a third color LED emitting layer between the lower conductive layer and the upper conductive layer.

[0102] In one embodiment of the present invention, the LED light-emitting layer includes a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer between the first semiconductor epitaxial layer and the second semiconductor epitaxial layer.

[0103] In one embodiment of the present invention, the first semiconductor epitaxial layer is P-type and the second semiconductor epitaxial layer is N-type; or the first semiconductor epitaxial layer is N-type and the second semiconductor epitaxial layer is P-type; the material of the first semiconductor epitaxial layer is a Ga-containing III-V group semiconductor material; the light-emitting layer includes a multi-quantum well layer.

[0104] In one embodiment of the present invention, the first LED structure further includes an upper connecting portion located between the upper conductive layer and the LED light-emitting layer and electrically connected to the upper conductive layer and the LED light-emitting layer.

[0105] In one embodiment of the present invention, the upper conductive layer and the lower conductive layer comprise a metal layer or a transparent conductive layer.

[0106] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: A substrate is located below the first LED structure, and the first LED structure is bonded to the substrate through the metal layer.

[0107] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: The metal pillars are located on the substrate, and the second LED structure and the third LED structure are bonded to the metal pillars through the metal bonding layer.

[0108] In one embodiment of the present invention, the lower end of the metal pillar is electrically connected to a contact on the substrate 610, and the upper end is electrically connected to the metal bonding layer.

[0109] In one embodiment of the present invention, the metal bonding layer includes an alloy reflective layer.

[0110] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: An insulating medium, wherein the first LED structure, the second LED structure, and the third LED structure are embedded within the insulating medium.

[0111] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: Multiple metal structures are arranged around the first LED structure, the second LED structure, and the third LED structure.

[0112] In one embodiment of the present invention, the plurality of metal structures include an alloy reflective layer located on the sidewalls of the plurality of metal structures.

[0113] In one embodiment of the present invention, the micro LED pixel with alloy reflective structure further includes: Microlenses located on the top surface of the third LED structure.

[0114] The present invention has at least the following beneficial effects: This invention uses aluminum alloy or silver alloy as the reflective layer, which can significantly improve the oxidation resistance of the reflective layer and the stability between the reflective layer and the conductive layer. Furthermore, this invention provides an adhesive layer between the reflective layer and the conductive layer, which can significantly improve the adhesion between the two layers without significantly reducing reflectivity. Attached Figure Description

[0115] To further illustrate the advantages and features of the various embodiments of the present invention, a more specific description of the embodiments of the present invention will be presented with reference to the accompanying drawings. It should be understood that these drawings depict only typical embodiments of the present invention and are therefore not intended to limit its scope. In the drawings, identical or corresponding parts will be indicated by the same or similar reference numerals for clarity.

[0116] Figure 1 This is a cross-sectional schematic diagram of a micro LED pixel according to the first embodiment of the present invention.

[0117] Figure 2A cross-sectional schematic diagram of a micro LED pixel with an alloy reflective structure according to a second embodiment of the present invention is shown.

[0118] Figure 3A A cross-sectional schematic diagram of a micro LED pixel with an alloy reflective structure is shown in the third embodiment of the present invention.

[0119] Figure 3B A circuit diagram of a micro LED pixel with an alloy reflective structure is shown in the third embodiment of the present invention.

[0120] Figure 4A A top view of a micro LED pixel with an alloy reflective structure is shown in the fourth embodiment of the present invention.

[0121] Figure 4B A schematic cross-sectional view of a micro-LED pixel with an alloy reflective structure along line AA is shown according to a fourth embodiment of the present invention.

[0122] Figure 5A A top view of a micro LED pixel according to a fifth embodiment of the present invention is shown.

[0123] Figure 5B A schematic cross-sectional view of a micro-LED pixel along line AA is shown according to a fifth embodiment of the present invention.

[0124] Figure 5C A schematic cross-sectional view of a micro-LED pixel along line BB according to a fifth embodiment of the present invention is shown.

[0125] Figure 5D A schematic cross-sectional view of a micro-LED pixel along line CC is shown according to a fifth embodiment of the present invention.

[0126] Figure 6A A top view of a micro LED pixel with an alloy reflective structure according to a sixth embodiment of the present invention is shown.

[0127] Figure 6B A schematic cross-sectional view of a micro-LED pixel with an alloy reflective structure along line AA is shown according to a sixth embodiment of the present invention.

[0128] Figure 6C A schematic cross-sectional view of a micro-LED pixel with an alloy reflective structure along line BB is shown according to a sixth embodiment of the present invention. Detailed Implementation

[0129] It should be noted that the components in the illustrations may be shown exaggeratedly for illustrative purposes and may not be proportionally accurate. In the illustrations, identical or functionally equivalent components are given the same labeling.

[0130] In this invention, unless otherwise stated, "arranged on," "arranged above," and "arranged on top of" do not exclude the possibility of an intermediate element between them. Furthermore, "arranged on or above" merely indicates the relative positional relationship between two components, and in certain cases, such as when the product orientation is reversed, it can also be converted to "arranged below or under," and vice versa.

[0131] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0132] In this invention, unless otherwise stated, the quantifiers “one” and “a” do not exclude the existence of multiple elements.

[0133] It should also be noted that, in the embodiments of the present invention, only a portion of the components or parts may be shown for clarity and simplicity. However, those skilled in the art will understand that, under the teachings of the present invention, necessary components or parts can be added according to specific needs. Furthermore, unless otherwise stated, features in different embodiments of the present invention can be combined with each other. For example, a feature in the second embodiment can replace a corresponding or functionally identical or similar feature in the first embodiment, and the resulting embodiment will also fall within the scope of disclosure or description of this application.

[0134] It should also be noted that, within the scope of this invention, terms such as "same," "equal," and "equal to" do not imply that the two values ​​are absolutely equal, but rather allow for a certain reasonable margin of error. In other words, these terms also encompass "substantially the same," "substantially equal," and "substantially equal to." Similarly, in this invention, the directional terms "perpendicular to," "parallel to," etc., also encompass the meanings of "substantially perpendicular to" and "substantially parallel to."

[0135] In this application, the term "configuration" refers to the setting of the shape, structure, material and / or function of a target object to achieve the desired technical effect, wherein "configuration" includes various alternative technical means to achieve the technical effect, which become apparent from the teachings of this application.

[0136] Furthermore, the numbering of the steps in the method of the present invention does not limit the execution order of the method steps. Unless otherwise stated, the method steps may be executed in a different order.

[0137] The present invention will be further described below with reference to specific embodiments and the accompanying drawings.

[0138] Figure 1 This is a cross-sectional schematic diagram of a micro-LED pixel according to a first embodiment of the present invention. Figure 1As shown, the micro-LED pixel is a monochrome micro-LED pixel with an alloy reflective structure, comprising: a substrate 110, an LED structure 120, a conductive layer 130, a metal structure 140, a microlens 150, and a metal layer 170 on which a reflective layer 172 is disposed. The metal layer 170 can serve as a metal bonding layer to bond the LED structure 120 to the substrate 110. In this embodiment, the reflective layer 172 is disposed on top of the metal layer 170, i.e., forming the top surface of the metal layer 170.

[0139] For example, the material of the metal structure is an aluminum alloy or a silver alloy. In one embodiment of this application, for example, the aluminum alloy may include one or more of AlCu, AlSi, AlMg, AlNi, AlS, AlMn, and combinations thereof; the silver alloy may include one or more of AgCu, AgNi, AgZn, AgPd, AgMg, AgW, and combinations thereof.

[0140] like Figure 1 As shown, a gap 190 is formed between adjacent micro-LED structures 120, and a metal structure 140 is formed at the bottom of the gap 190. For example, the metal structure 140 fills at least a portion of the gap 120, preferably filling the bottom of the gap 190 to form a flat surface of the metal structure 140. In other embodiments, the gap 190 may also have a non-flat surface, such as a curved or irregular surface.

[0141] Alternatively or additionally, the tops of adjacent microLED structures 120 may be interconnected, for example, via a conductive layer 130 to form an interconnect top 191, and a gap 190 may be formed between adjacent microLED structures 120 above the interconnect top (e.g., Figure 1 (as shown) or below ( Figure 1 (Not shown). Furthermore, a metal structure 140 may be formed on top of the interconnect top 191 and around the bottom of the microLED structure 120 (e.g., ...). Figure 1 (as shown) or top ( Figure 1 (Not shown).

[0142] The micro-LED structure 120 can be more than one, for example, two, three, ten, ..., one hundred, or one thousand or more. The micro-LED structures 120 can be stacked vertically rather than... Figure 1The microLED structures are arranged side-by-side as shown. In the former case, the interconnect conductive structures are perpendicular to the bottom of the microLED structures 120, serving as electrical / mechanical connections between the vertically stacked microLED structures 120 or between each LED structure and each electrode. Each interconnect conductive structure can be connected to the bottom of each microLED 120 separately. With the microLED structures 120 arranged vertically, chip area can be saved or a colored LED chip can be formed. In the vertical arrangement, the metal layer 170 is preferably formed on the sidewall surface of the interconnect conductive structure. Further, the metal layer can cover the entire surface of the interconnect conductive structure, such as the sidewall surface. Alternatively, the metal layer can cover only a portion of the surface of the interconnect conductive structure.

[0143] For clarity, "upward" means away from substrate 101, and "downward" means towards substrate 110. Other directional terms such as top, bottom, above, below, under, etc., are understood accordingly. Substrate 110 is a substrate on which an array of individual driver circuits is fabricated. In some embodiments, the driver circuits may also be located in a layer above substrate 110. Each driver circuit is a pixel driver. In some cases, the driver circuits are thin-film transistor pixel drivers or silicon CMOS pixel drivers. In one embodiment, substrate 110 is a silicon substrate. In another embodiment, the supporting substrate 110 is a transparent substrate, such as a glass substrate. Other example substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. The driver circuits form individual pixel drivers to control the operation of individual multi-color micro-LED pixels. The circuitry on substrate 110 includes contacts connected to each individual driver circuit and ground contacts.

[0144] In some embodiments, the LED structure 120 includes a lower conductive layer 121, an upper conductive layer 122, and an LED light-emitting layer 123 between the lower conductive layer 121 and the upper conductive layer 122. In some embodiments, the LED light-emitting layer may include a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer between the first and second semiconductor epitaxial layers. The light-emitting layer may be, but is not limited to, a multi-quantum-well layer. The first conductivity type may be N-type, and the second conductivity type may be P-type; or the first conductivity type may be P-type, and the second conductivity type may be N-type. The N-type semiconductor epitaxial layer in each light-emitting layer includes, but is not limited to, N-type Si-doped GaN, Si-doped AlGaN, Si-doped AlGaInP, Si-doped GaAs, or Si-doped AlInP; the P-type semiconductor epitaxial layer includes, but is not limited to, Mg-doped GaN, Mg-doped AlGaN, Mg-doped InGaN, Mg-doped InAlGaN, Mg-doped AlInP, Mg-doped AlGaInP, Mg-doped GaP, or C-doped GaP. Quantum well layers include, but are not limited to, InGaN / GaN cycles and InGaP / AlGaInP cycles.

[0145] In some embodiments, the upper conductive layer 122 and the lower conductive layer 121 may be metal layers or transparent conductive layers, such as ITO, FTO, or copper layers, which are formed to improve conductivity and transparency. In another embodiment, the lower conductive layer 121 may be a metal layer to form part of the metal bonding layer 170.

[0146] Although some features are described using the term "layer" here, it should be understood that these features are not limited to a single layer and may include multiple sub-layers. In some cases, a "structure" can be presented in the form of "layers".

[0147] In some embodiments, the LED structure 120 is bonded to the substrate 110 via a metal bonding layer 170. In some embodiments, the contacts of the metal bonding layer 170 on the substrate 110 form an electrical connection with the LED structure 120 above the metal bonding layer 170, serving as a P-electrode. In some embodiments, the thickness of the metal bonding layer 170 is from about 0.1 μm to about 3 μm. In a preferred embodiment, the thickness of the metal bonding layer 170 is about 0.3 μm. The metal bonding layer 170 may include an ohmic contact layer and a metal bonding layer. In some embodiments, the composition of the metal bonding layer 170 includes Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or mixtures thereof. For example, if Au-Au bonding is selected, the two Au layers require a Cr coating as an adhesive layer and a Pt coating as an anti-diffusion layer, with the Pt coating located between the Au layer and the Cr layer. The Cr and Pt layers are located at the top and bottom of the two bonded Au layers. In some embodiments, when the two Au layers are of similar thickness, mutual diffusion of Au on the two layers under high pressure and high temperature will bond the two layers together. Exemplary processes that can be used include eutectic bonding, hot-press bonding, and transient liquid phase (TLP) bonding.

[0148] In some embodiments, the metal bonding layer 170 may further include a connection portion 171 between the metal bonding layer 170 and the contacts on the substrate 110, and the connection portion electrically connects the metal bonding layer 170 and the contacts on the substrate 110. The material of the connection portion 171 is a metal, including one or more of Al, Au, Rh, Ag, Cr, Ti, Pt, Sn, Cu, AuSn, TiW, etc.

[0149] In some embodiments, the metal bonding layer 170 may also function as a reflector to reflect light emitted from the upper LED structure. In some embodiments, the metal bonding layer 170 may include a reflective layer 172. The reflective layer 172 is connected to the underlying conductive layer 121.

[0150] In some embodiments, the reflective layer 172 can be an alloy reflective layer. In some embodiments, the material of the alloy reflective layer is an aluminum alloy or a silver alloy. Aluminum alloy can significantly improve the thermal stability between the reflective layer 172 and the underlying conductive layer 121, avoiding reactions between metallic aluminum and the underlying conductive layer 121. Silver alloy is more stable and less prone to oxidation than metallic silver.

[0151] In some embodiments, the aluminum alloy includes, but is not limited to, AlCu, AlSi, AlMg, AlNi, AlSn, and AlMn. Different aluminum contents in the aluminum alloy will affect the reflectivity, oxidation resistance, and thermal stability of the aluminum alloy and the conductive layer.

[0152] In some embodiments, the silver alloy includes, but is not limited to, AgCu, AgNi, AgZn, AgPd, AgMg, and AgW. Different silver contents in aluminum alloys will affect the reflectivity, thermal stability, and oxidation resistance of the silver alloy.

[0153] In some embodiments, an adhesive layer exists between the reflective layer 172 and the underlying conductive layer 121. The material of the adhesive layer includes, but is not limited to, Cr, Ti, Ni, or Ta. This is because the adhesion between aluminum alloys or silver alloys and the conductive layer is relatively general, and the adhesive layer can increase the adhesion between the reflective layer and the conductive layer without significantly reducing the emissivity of the reflective layer. The thickness of the adhesive layer can be 1 nm Cr or 0.5 nm Ti. Experiments show that adding 1 nm Cr to the aluminum alloy only reduces the reflectivity by about 2%, but significantly enhances the adhesion between the aluminum alloy and the conductive layer.

[0154] In some embodiments, the conductive layer 130 is located above the LED structure 120 and is connected to the upper conductive layer 122 of the LED structure 120. The conductive layer 130 electrically connects multiple LED structures 120.

[0155] In some embodiments, the conductive layer 130 may be a metal layer or a transparent conductive layer such as ITO, FTO, or copper layer, and its formation is intended to improve conductivity and transparency.

[0156] In some embodiments, the metal structure 140 is located on and electrically connected to the conductive layer 130. The metal structure 140 is located in the gaps between the plurality of LED structures 120.

[0157] In some embodiments, the metal structure 140 can serve as a common electrode connecting the upper conductive layer of each LED structure, functioning as an N-electrode. That is, the metal structure 140 can electrically connect the upper conductive layers 122 of multiple LED structures 120 to the negative terminal of an external power supply.

[0158] However, those skilled in the art will understand that the N-type and P-type electrodes of the LED structure are interchangeable. For example, the metal structure 140 can serve as a common P-type electrode to connect the P-type epitaxial layer of each LED structure, while the corresponding N-type epitaxial layer of the LED structure is electrically connected to the metal bonding layer.

[0159] In some embodiments, the LED structure 120 is embedded within an insulating medium 160. The insulating medium 160 is transparent to light emitted from the LED structure 120. In some embodiments, the insulating medium 160 is made of a dielectric material, such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, SiCN, HfO2, Ta2O5, TiO2, ZrO2, La2O3, MgO, phosphosilicate glass (PSG), borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG), or bonding adhesive Micro Resist BCL-1200, or any combination thereof. In some embodiments, the insulating medium 160 allows light emitted from the LED pixel to pass through.

[0160] In some embodiments, a microlens 150 is formed on the top surface of the conductive layer 130 and the metal structure 140. In some embodiments, the microlens 150 alters the light path emitted by a single microLED pixel by making the light emitted by the LED device more focused or more diffused according to design requirements.

[0161] In some embodiments, the microlens 150 may be made of a variety of materials that are transparent at the wavelengths emitted by the individual microLED structure. Exemplary transparent materials for the microlens 150 include polymers, dielectric materials, and semiconductor materials. In some embodiments, the dielectric material includes one or more materials, such as silicon oxide, silicon nitride, silicon carbide, titanium oxide, zirconium oxide, aluminum oxide, etc. In some embodiments, the microlens 150 is made of photoresist.

[0162] In some embodiments, the microlens 150 is typically hemispherical in shape. In some embodiments, the central axis of the microlens 150 is aligned with or the same as the central axis of a single microLED structure without a lens.

[0163] Each microlens 150 has positive optical power and is positioned to reduce the divergence or viewing angle of light emitted from a corresponding microLED pixel light source. In one embodiment, the light beam emitted from the microLED pixel light source has a relatively wide original divergence angle. In one embodiment, the original angle of the edge rays of the beam relative to the orthogonal axis perpendicular to the substrate 110 is greater than 60 degrees. The light is bent by the microlens 150, such that the new edge rays now have a reduced divergence angle. In one embodiment, the reduced angle is less than 30 degrees. The microlenses in the microlens array are typically identical. Examples of microlenses include spherical microlenses, aspherical microlenses, Fresnel microlenses, and cylindrical microlenses.

[0164] Microlens 150 typically has a flat side and a curved side. Figure 1 In this configuration, the bottom of the microlens 150 is flat, and the top of the microlens 150 is curved. Typical shapes of the base for each microlens 150 include circular, square, rectangular, and hexagonal. Individual microlenses in the microlens array of the display panel may be the same or different in terms of shape, curvature, optical power, size, base, and spacing. In some embodiments, the shape of the microlens 150 matches that of a single microLED structure. In one example, the shape of the base of the microlens 150 is the same as the shape of the single microLED structure. In another example, the shape of the base of the microlens 150 is different from that of the single microLED structure; for example, a microlens with a circular base has the same width as a single microLED structure, but its area is smaller because the base of the microlens is circular while the base of the single microLED structure is square. In some embodiments, the area of ​​the microlens base is smaller than the area of ​​the microLED pixel source. In some embodiments, the area of ​​the microlens base is the same as or larger than the area of ​​the microLED light source.

[0165] In some embodiments, brightness enhancement is achieved by integrating a microlens array onto the display panel. In some instances, due to the light-focusing effect of the microlenses, the brightness with the microlens array is four times that without the microlens array in the direction perpendicular to the display surface. In alternative embodiments, the brightness enhancement factor can vary depending on the design of the microlens array and the optical spacer layer. For example, an enhancement factor greater than 8 can be achieved.

[0166] Microlenses can be fabricated through a variety of manufacturing processes, including deposition, patterning, and etching.

[0167] Figure 2 A cross-sectional schematic diagram of a micro-LED pixel with an alloy reflective structure according to a second embodiment of the present invention is shown. Figure 2 As shown, the micro LED pixel with alloy reflective structure is a monochrome micro LED pixel, including: substrate 210, LED structure 220, bonding portion 230, reflective layer 240, passivation layer 250, insulating medium 260, metal structure 270 and microlens 280.

[0168] In some embodiments, substrate 210 is a substrate on which an array of individual driver circuits is fabricated. In some embodiments, the driver circuits may also be located in a layer above substrate 210. Each driver circuit is a pixel driver. In some cases, the driver circuit is a thin-film transistor pixel driver or a silicon CMOS pixel driver. In one embodiment, substrate 210 is a silicon substrate. In another embodiment, the supporting substrate 210 is a transparent substrate, such as a glass substrate. Other example substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. The driver circuits form individual pixel drivers to control the operation of individual micro-LED pixels. The circuitry on substrate 210 includes contacts connected to each individual driver circuit and ground contacts.

[0169] In some embodiments, the LED structure 220 may include a conductive layer 221 and an LED light-emitting layer located on the conductive layer 221.

[0170] In some embodiments, the LED light-emitting layer may include a first semiconductor epitaxial layer 222 of a first conductivity type, a second semiconductor epitaxial layer 223 of a second conductivity type, and a light-emitting layer 224 between the first semiconductor epitaxial layer 222 and the second semiconductor epitaxial layer 223. The light-emitting layer 224 may be, but is not limited to, a multi-quantum-well layer. The first conductivity type may be N-type, and the second conductivity type may be P-type; or the first conductivity type may be P-type, and the second conductivity type may be N-type. The N-type semiconductor epitaxial layer in each light-emitting layer includes, but is not limited to, N-type Si-doped GaN, Si-doped AlGaN, Si-doped AlGaInP, Si-doped GaAs, or Si-doped AlInP; the P-type semiconductor epitaxial layer includes, but is not limited to, Mg-doped GaN, Mg-doped AlGaN, Mg-doped InGaN, Mg-doped InAlGaN, Mg-doped AlInP, Mg-doped AlGaInP, Mg-doped GaP, or C-doped GaP. The quantum well layer includes, but is not limited to, InGaN / GaN cycling and InGaP / AlGaInP cycling.

[0171] In some embodiments, the second semiconductor epitaxial layer 223 of the LED structure 220 of multiple micro-LED pixels is integrated as a single entity.

[0172] In some embodiments, a second semiconductor epitaxial layer 223 of the LED structure 220 of the plurality of micro-LED pixels is integrated.

[0173] In some embodiments, the conductive layer 221 can be a metal layer or a transparent conductive layer, such as ITO, FTO, or copper, and is formed to improve conductivity and transparency.

[0174] Although some features are described using the term "layer" here, it should be understood that these features are not limited to a single layer and may include multiple sub-layers. In some cases, a "structure" can be presented in the form of "layers".

[0175] In some embodiments, the LED structure 220 is bonded to the substrate 210 via a bonding portion 230 located between the conductive layer 221 of the LED structure 220 and the contacts 211 on the substrate 210, and is electrically connected to the conductive layer 221 and the contacts 211 on the substrate 210. The material of the bonding portion 230 is a metal, including one or more of Al, Au, Rh, Ag, Cr, Ti, Pt, Sn, Cu, AuSn, TiW, etc.

[0176] In some embodiments, the reflective layer 240 is located below the LED structure 220 to reflect light emitted from the LED structure 220 above. In some embodiments, the reflective layer is located between the conductive layer 221 and the bonding portion 230, and is electrically connected to both the conductive layer 221 and the bonding portion 230. In some embodiments, the reflective layer 240 may be an alloy reflective layer.

[0177] In some embodiments, a passivation layer 250 is provided between the reflective layer 240 and the LED light-emitting layer of the LED structure 220. In some embodiments, the passivation layer 250 is made of a passivation material, such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, SiCN, HfO2, Ta2O5, TiO2, ZrO2, La2O3, MgO, phosphosilicate glass (PSG), borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG), or bonding adhesives Micro Resist BCL-1200, or any combination thereof.

[0178] In some embodiments, an insulating medium 260 is filled between the reflective layer 240 and the substrate 210. The insulating medium 260 is made of a dielectric material, such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, SiCN, HfO2, Ta2O5, TiO2, ZrO2, La2O3, MgO, phosphosilicate glass (PSG), borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG), or bonding adhesives such as Micro ResistBCL-1200, or any combination thereof.

[0179] In some embodiments, the metal structure 270 is located in the gap between the plurality of LED structures 220 and is electrically connected to the second semiconductor epitaxial layer 223 of the LED structure 220.

[0180] In some embodiments, the metal structure 240 can serve as a common electrode to connect the second semiconductor epitaxial layer 223 of each LED structure, functioning as an N-electrode. That is, the metal structure 240 can electrically connect the second semiconductor epitaxial layer 223 corresponding to the LED structure 120 to the negative terminal of an external power supply.

[0181] In some embodiments, the metal structure 240 may also function as a reflector to reflect light emitted by the LED structure 120. In some embodiments, the metal structure 240 is an alloy reflective layer.

[0182] In some embodiments, a microlens 280 is formed on the top surface of the second semiconductor epitaxial layer 223 of the LED structure 120.

[0183] Figure 3A A cross-sectional schematic diagram of a micro LED pixel with an alloy reflective structure according to a third embodiment of the present invention is shown. Figure 3B A circuit diagram of a micro LED pixel with an alloy reflective structure according to a third embodiment of the present invention is shown. Figure 3A and Figure 3B As shown, the micro LED pixel with alloy reflective structure is a monochrome micro LED pixel with stacked LED emitters, including: substrate 310, first LED structure 320, second LED structure 330, metal bonding layer 340, insulating medium 350 and metal structure 360.

[0184] In some embodiments, substrate 310 is a substrate on which an array of individual driver circuits is fabricated. In some embodiments, the driver circuits may also be located in a layer above substrate 310. Each driver circuit is a pixel driver. In some cases, the driver circuit is a thin-film transistor pixel driver or a silicon CMOS pixel driver. In one embodiment, substrate 310 is a silicon substrate. In another embodiment, the supporting substrate 310 is a transparent substrate, such as a glass substrate. Other example substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. The driver circuits form individual pixel drivers to control the operation of individual micro-LED pixels. The circuitry on substrate 310 includes contacts 311 connected to each individual driver circuit and a ground contact.

[0185] In some embodiments, the first LED structure 320 may include a lower conductive layer 321, an upper conductive layer 322, and an LED light-emitting layer 323 between the lower conductive layer 321 and the upper conductive layer 322; the second LED structure 330 may include a lower conductive layer 331, an upper conductive layer 332, and an LED light-emitting layer 333 between the lower conductive layer 331 and the upper conductive layer 332.

[0186] In some embodiments, the upper conductive layer 322 of the first LED structure 320 is electrically connected to the upper conductive layer 332 of the second LED structure 330.

[0187] In some embodiments, LED light-emitting layers 323 and 333 may include a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer between the first and second semiconductor epitaxial layers. The light-emitting layer may be, but is not limited to, a multi-quantum-well layer. The first conductivity type may be N-type, and the second conductivity type may be P-type; or the first conductivity type may be P-type, and the second conductivity type may be N-type. The N-type semiconductor epitaxial layer in each light-emitting layer includes, but is not limited to, N-type Si-doped GaN, Si-doped AlGaN, Si-doped AlGaInP, Si-doped GaAs, or Si-doped AlInP; the P-type semiconductor epitaxial layer includes, but is not limited to, Mg-doped GaN, Mg-doped AlGaN, Mg-doped InGaN, Mg-doped InAlGaN, Mg-doped AlInP, Mg-doped AlGaInP, Mg-doped GaP, or C-doped GaP. The quantum well layer includes, but is not limited to, InGaN / GaN cycling and InGaP / AlGaInP cycling.

[0188] In some embodiments, the upper conductive layer and the lower conductive layer can be metal layers or transparent conductive layers, such as ITO, FTO, or copper layers, which are formed to improve conductivity and transparency. In another embodiment, the lower conductive layer 321 can be a metal layer to form part of the metal bonding layer 340.

[0189] In some embodiments, the first LED structure 320 is bonded to the substrate 510 via a metal bonding layer 340. The metal bonding layer 340 may be disposed on the substrate 310. One method is to grow the metal bonding layer 340 on the substrate 310. In some embodiments, the metal bonding layer 340 forms an electrical connection between a contact 311 on the substrate 310 and the first LED structure 320 located above the metal bonding layer 340, serving as a P-electrode. In some embodiments, the thickness of the metal bonding layer 340 is from about 0.1 μm to about 3 μm. In a preferred embodiment, the thickness of the metal bonding layer 340 is about 0.3 μm. The metal bonding layer may include an ohmic contact layer and a metal bonding layer. In some cases, the metal bonding layer 340 includes two metal layers. One of the metal layers is deposited at the bottom of the first LED structure 320. The corresponding bonding metal layer is deposited on the substrate 310. In some embodiments, the metal bonding layer 340 comprises Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or mixtures thereof. For example, if Au-Au bonding is selected, each of the two Au layers requires a Cr coating as an adhesive layer and a Pt coating as an anti-diffusion layer, with the Pt coating located between the Au layer and the Cr layer. The Cr and Pt layers are located at the top and bottom of the two bonded Au layers. In some embodiments, when the thicknesses of the two Au layers are approximately the same, mutual diffusion of Au on the two layers under high pressure and high temperature will bond the two layers together. Exemplary processes that can be used include eutectic bonding, hot-press bonding, and transient liquid phase (TLP) bonding.

[0190] In some embodiments, the metal bonding layer 340 may also function as a reflector, reflecting light emitted from the upper LED structure. In some embodiments, the metal bonding layer 340 may include a reflective layer 341. Moreover, the reflective layer 341 may be an alloy reflective layer.

[0191] In some embodiments, the second LED structure 330 is located above the first LED structure 320. The first LED structure 320 and the second LED structure 330 are embedded within an insulating medium 350. The insulating medium 350 is transparent to light emitted from the first LED structure 320 and the second LED structure 330. In some embodiments, the insulating medium 350 is made of a dielectric material, such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, SiCN, HfO2, Ta2O5, TiO2, ZrO2, La2O3, MgO, phosphosilicate glass (PSG), borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG), or bonding adhesives such as Micro Resist BCL-1200, or any combination thereof. In some embodiments, the insulating medium 350 allows light emitted from the LED pixels to pass through. In some embodiments, the insulating medium 350 may include multiple portions, such as two embedded medium portions and one bonding medium portion. The embedded medium portion refers to the dielectric layer surrounding each LED structure; the bonding medium portion refers to the dielectric layer between two LED structures. The embedded medium portions and the bonding medium portions may have the same or different compositions.

[0192] In some embodiments, the first LED structure 320 is embedded in the embedded medium portion, and the surface of the embedded medium portion is smoothed or planarized by a chemical mechanical polishing method.

[0193] In some embodiments, the second LED structure 330 is bonded to the first LED structure 320 via a bonding medium. The second LED structure 330 is embedded within the embedding medium, and the surface of the embedding medium is smoothed or planarized by a chemical mechanical polishing method.

[0194] In some embodiments, the metal structure 360 ​​may be connected to the lower conductive layer 331 and the metal bonding layer 340 of the second LED structure 330.

[0195] In some embodiments, a reflective layer 361 is provided on the sidewall of the metal structure 360. In some embodiments, the reflective layer 361 is an alloy reflective layer.

[0196] Figure 4A A top view of a micro LED pixel with an alloy reflective structure according to a fourth embodiment of the present invention is shown. Figure 4B A schematic cross-sectional view of a micro-LED pixel with an alloy reflective structure along line AA is shown according to a fourth embodiment of the present invention. Figure 4A and Figure 4BAs shown, the micro LED pixel with alloy reflective structure is a dual-color micro LED pixel, including: substrate 410, first LED structure 420, second LED structure 430, metal bonding layer 440, and multiple metal structures 460.

[0197] In some embodiments, substrate 410 is a substrate for fabricating an array of individual driver circuits. In some embodiments, the driver circuits may also be located in one of the layers above substrate 410. Each driver circuit is a pixel driver. In some cases, the driver circuit is a thin-film transistor pixel driver or a silicon CMOS pixel driver. In one embodiment, substrate 410 is a silicon substrate. In another embodiment, the support substrate 410 is a transparent substrate, such as a glass substrate. Other example substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. The driver circuits constitute individual pixel drivers to control the operation of each multicolor Micro-LED pixel. The circuitry on substrate 410 includes contacts 411 connected to each individual driver circuit and a ground contact.

[0198] In some embodiments, the first LED structure 420 may include a lower conductive layer 421, an upper conductive layer 422, and a green LED light-emitting layer 423 located between the lower conductive layer 421 and the upper conductive layer 422; the second LED structure 430 may include a lower conductive layer 431, an upper conductive layer 432, and a blue LED light-emitting layer 433 located between the lower conductive layer 431 and the upper conductive layer 432. Those skilled in the art should understand that the LED light-emitting layer 423 in the first LED structure 420 is not limited to a green light-emitting layer, and the LED light-emitting layer 433 in the second LED structure 430 is not limited to a blue light-emitting layer. That is, the LED light-emitting layers 423 and 433 can be any color light-emitting layers as needed. The green and blue light-emitting layers or LED structures described herein are merely illustrative and not restrictive.

[0199] In some embodiments, LED light-emitting layers 423 and 433 may include a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer located between the first and second semiconductor epitaxial layers. The light-emitting layer may be, but is not limited to, a multi-quantum-well layer. The first conductivity type may be N-type, and the second conductivity type may be P-type; or the first conductivity type may be P-type, and the second conductivity type may be N-type. The N-type semiconductor epitaxial layer in each light-emitting layer includes, but is not limited to, N-type Si-doped GaN, Si-doped AlGaN, Si-doped AlGaInP, Si-doped GaAs, or Si-doped AlInP; the P-type semiconductor epitaxial layer includes, but is not limited to, Mg-doped GaN, Mg-doped AlGaN, Mg-doped InGaN, Mg-doped InAlGaN, Mg-doped AlInP, Mg-doped AlGaInP, Mg-doped GaP, or C-doped GaP. The quantum well layer includes, but is not limited to, InGaN / GaN cycling and InGaP / AlGaInP cycling.

[0200] In some embodiments, the upper conductive layer and the lower conductive layer can be metal layers or transparent conductive layers, such as ITO, FTO, or copper layers, which are formed to improve conductivity and transparency. In another embodiment, the lower conductive layer 421 can be a metal layer to form part of the metal bonding layer 440.

[0201] In some embodiments, the first LED structure 420 is bonded to the substrate 410 via a metal bonding layer 440. The metal bonding layer 440 may be disposed on the substrate 410. One method is to grow the metal bonding layer 440 on the substrate 410. In some embodiments, the contacts 411 of the metal bonding layer 440 on the substrate 410 are electrically connected to the first LED structure 420 located above the metal bonding layer 440, serving as a P-electrode. In some embodiments, the thickness of the metal bonding layer 440 is approximately 0.1 μm to 3 μm. In a preferred embodiment, the thickness of the metal bonding layer 440 is approximately 0.3 μm. The metal bonding layer may include an ohmic contact layer and a metal bonding layer. In some cases, the metal bonding layer 440 includes two metal layers. One layer is deposited on the bottom of the first LED structure 420, and the corresponding bonding metal layer is deposited on the substrate 410. In some embodiments, the metal bonding layer 440 comprises Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or mixtures thereof. For example, if Au-Au bonding is selected, each of the two Au layers requires a Cr coating as an adhesive layer and a Pt coating as an anti-diffusion layer, with the Pt coating located between the Au layer and the Cr layer. The Cr layer and the Pt layer are located at the top and bottom of the two bonded Au layers, respectively. In some embodiments, when the thicknesses of the two Au layers are similar, interlayer bonding can be achieved through mutual diffusion of the two Au layers under high pressure and high temperature conditions. Eutectic bonding, hot-press bonding, and transient liquid phase bonding (TLP) are example technologies that can be used.

[0202] In some embodiments, the metal bonding layer 440 may also function as a reflector to reflect light emitted from the upper LED structure. In some embodiments, the metal bonding layer 440 may include a reflective layer 441. Furthermore, the reflective layer 441 may be an alloy reflective layer.

[0203] In some embodiments, the second LED structure 430 is located above the first LED structure 420. The first LED structure 420 and the second LED structure 430 are embedded within an insulating medium 450. The insulating medium 450 is transparent to light emitted from the first LED structure 420 and the second LED structure 430. In some embodiments, the insulating medium 450 is made of a dielectric material, such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, SiCN, HfO2, Ta2O5, TiO2, ZrO2, La2O3, MgO, phosphosilicate glass (PSG), borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG), or bonding adhesive Micro Resist BCL-1200, or any combination thereof. In some embodiments, the insulating medium 450 allows light emitted from the LED structure to pass through. In some embodiments, the insulating medium 450 may include multiple portions, such as two embedded medium portions and one bonding medium portion. The embedded medium portion refers to the dielectric layer surrounding each LED structure; the bonding medium portion refers to the dielectric layer between two LED structures. The embedded medium portions and the bonding medium portions may have the same or different compositions.

[0204] In some embodiments, the first LED structure 420 is embedded in the embedding medium portion, and the surface of the embedding medium portion is smoothed or planarized by a chemical mechanical polishing method.

[0205] In some embodiments, the second LED structure 430 is bonded to the first LED structure 420 via a bonding medium. The second LED structure 430 is embedded in the embedding medium, and the surface of the embedding medium is smoothed or planarized by a chemical mechanical polishing method.

[0206] In some embodiments, a plurality of metal structures 460 are arranged around the first LED structure and the second LED structure.

[0207] In some embodiments, the plurality of metal structures 460 may include metal structures 460a to 460d. Each metal structure is isolated from the others by an insulating medium 450. The plurality of metal structures 460 may be interconnecting vias formed in the insulating medium 450. Figure 4AAs shown, metal structures 460a and 460c can be used as common electrodes to connect the upper conductive layers 432 and 422 and the top electrode corresponding to the LED structure; metal structure 460b can connect the lower conductive layer 431 of the second LED structure 430 and the contact 411 on the substrate 410. Metal structures 460a and 460c can be located on the substrate 410, but are not directly electrically connected to the substrate 410. Metal structures 460a and 460c can electrically connect the upper conductive layers 432 and 422 corresponding to the LED structure to the negative terminal of an external power supply. The upper conductive layers 432 and 422 can be flat, or have upward or downward slopes due to the height difference between the metal structure and the LED light-emitting layer. For example, when forming the upper conductive layers 432 and 422, if the height of the metal structure is the same as that of the LED light-emitting layer, the upper conductive layers 432 and 422 are essentially flat; if the height of the metal structure is higher than that of the LED light-emitting layer, the upper conductive layers 432 and 422 include a ramp rising from the edge of the LED light-emitting layer to the metal structure; if the height of the metal structure is lower than that of the LED light-emitting layer, the upper conductive layers 432 and 422 include a ramp descending from the edge of the LED light-emitting layer to the metal structure. Those skilled in the art should understand that upper conductive layers of any shape can be designed according to the specific requirements of the micro-LED pixels, and such designs are all within the scope of protection of this invention.

[0208] In some embodiments, the top electrode may include an upper conductive layer 432 and a current diffusion layer. The upper conductive layer 432 may be formed on the LED light-emitting layer 433 and extend to the entire surface of the microLED pixel array below the bottom of the microlens.

[0209] The current diffusion layer can be formed on the upper conductive layer 432 and has better conductivity than the upper conductive layer 432. The current diffusion layer does not cover the light-emitting area of ​​each micro-LED pixel.

[0210] In some embodiments, the lower end of the metal structure 460 is located on the substrate 410; and the upper end of the metal structure 460 extends to a position not lower than the top surface of the second or third LED structure; preferably, the upper end of the metal structure 460 extends to the top surface of the insulating medium 450 or the bottom of the microlens or directly to the bottom of the top pad.

[0211] In some embodiments, the lower end of the metal structure 460b may be electrically connected to a contact on the substrate 410, and the upper end may extend to a position not lower than the top surface of the second LED structure; preferably, the upper end may extend to the top surface of the insulating medium 450 or the bottom of the microlens, or directly to the bottom of the top pad but not electrically connected to the top pad. The lower ends of the metal structures 460a and 460c may not be electrically connected to the contacts on the substrate 410, and the upper ends may extend to a position not lower than the top surface of the second LED structure; preferably, the upper ends may extend to the top surface of the insulating medium 450 or the bottom of the microlens, or directly to the bottom of the top pad and be electrically connected to the top pad.

[0212] Those skilled in the art should understand that the number, layout, size, and connection method of the metal structure 460 and the top pads are not limited to... Figures 4A-4B The illustrated embodiment can be modified according to actual needs, such as increasing or decreasing the number of metal structures, adjusting the shape of the metal structures, etc., and all such modifications fall within the protection scope of this invention. In the embodiment, metal structures 460a and 460c can serve as a common N-electrode connected to the upper conductive layers 432 and 422 corresponding to the LED structure, and metal structure 460b can serve as a P-electrode electrically connected to the lower conductive layer 431 corresponding to the LED structure. However, those skilled in the art should understand that the N-electrode and P-electrode of the LED structure are interchangeable. For example, metal structures 460a and 460c can serve as a common P-electrode connected to the P-type epitaxial layer of each LED structure, and metal structure 460b can serve as an N-electrode electrically connected to the corresponding N-type epitaxial layer of the LED structure.

[0213] In some embodiments, the materials of the plurality of metal structures 460 may be conductive metals, alloys, compounds, or combinations thereof.

[0214] In some embodiments, a reflective layer 461 is disposed on the sidewalls of a plurality of metal structures 460. In some embodiments, the reflective layer is an alloy reflective layer.

[0215] In some embodiments, a plurality of metal structures substantially surround the first LED structure and the second LED structure, such that light emitted from the LED structure toward the metal structure is reflected by the reflective layer 461 and emitted from the top surface of a single LED pixel.

[0216] In some embodiments, the plurality of metal structures having the reflective layer 461 can be fabricated by a combination of deposition, photolithography, and etching processes. In some embodiments, the plurality of metal structures having the reflective layer 461 can be fabricated by other suitable methods.

[0217] In some embodiments, a microlens 470 is formed on the top surface of the second LED structure 430. In some embodiments, the microlens 470 alters the light path emitted by a single microLED pixel by making the light emitted by the LED device more focused or more diffused according to design requirements.

[0218] Figure 5A A top view of a micro LED pixel according to a fifth embodiment of the present invention is shown. Figure 5B A schematic cross-sectional view of a micro-LED pixel along line AA is shown according to a fifth embodiment of the present invention. Figure 5C A schematic cross-sectional view of a micro-LED pixel along line BB according to a fifth embodiment of the present invention is shown. Figure 5D A schematic cross-sectional view of a micro-LED pixel along line CC is shown according to a fifth embodiment of the present invention. Figures 5A to 5D As shown, the micro LED pixel is a three-color micro LED pixel, including: substrate 510, first LED structure 520, second LED structure 530, third LED structure 540, multiple metal structures 550, and microlens 560.

[0219] For clarity, "upward" means away from substrate 510, and "downward" means towards substrate 510. Other directional terms such as top, bottom, above, below, under, etc., are understood accordingly. The support substrate 510 is a substrate on which an array of individual driver circuits is fabricated. In some embodiments, the driver circuits may also be located in a layer above substrate 510. Each driver circuit is a pixel driver. In some cases, the driver circuit is a thin-film transistor pixel driver or a silicon CMOS pixel driver. In one embodiment, substrate 510 is a silicon substrate. In another embodiment, support substrate 510 is a transparent substrate, such as a glass substrate. Other example substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. The driver circuits form individual pixel drivers to control the operation of individual multi-color micro-LED pixels. The circuitry on substrate 510 includes contacts 511 connected to each individual driver circuit and a ground contact.

[0220] In some embodiments, the first LED structure 520 may include a lower conductive layer 521, an upper conductive layer 522, and a red LED light-emitting layer 523 located between the lower conductive layer 521 and the upper conductive layer 522; the second LED structure 530 may include a lower conductive layer 531, an upper conductive layer 532, and a green LED light-emitting layer 533 located between the lower conductive layer 531 and the upper conductive layer 532; the third LED structure 540 may include a lower conductive layer 541, an upper conductive layer 542, and a blue LED light-emitting layer 543 located between the lower conductive layer 541 and the upper conductive layer 542. Those skilled in the art should understand that the LED light-emitting layer 523 in the first LED structure 520 is not limited to a red light-emitting layer, the LED light-emitting layer 533 in the second LED structure 530 is not limited to a green light-emitting layer, and the LED light-emitting layer 543 in the third LED structure 540 is not limited to a blue light-emitting layer. That is, the LED light-emitting layers 523, 533, and 543 can be any color light-emitting layers as needed. The red, green, and blue light-emitting layers or LED structures described herein are for illustrative purposes only and are not intended to be limiting.

[0221] In some embodiments, LED light-emitting layers 523, 533, and 543 may include a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer located between the first and second semiconductor epitaxial layers. The light-emitting layer may be, but is not limited to, a multi-quantum-well layer. The first conductivity type may be N-type, and the second conductivity type may be P-type; or the first conductivity type may be P-type, and the second conductivity type may be N-type. The N-type semiconductor epitaxial layer of each of the three-color light-emitting layers includes, but is not limited to, N-type Si-doped GaN, Si-doped AlGaN, Si-doped AlGaInP, Si-doped GaAs, or Si-doped AlInP; the P-type semiconductor epitaxial layer includes, but is not limited to, Mg-doped GaN, Mg-doped AlGaN, Mg-doped InGaN, Mg-doped InAlGaN, Mg-doped AlInP, Mg-doped AlGaInP, Mg-doped GaP, or C-doped GaP. The quantum well layer includes, but is not limited to, InGaN / GaN cycling and InGaP / AlGaInP cycling.

[0222] In some embodiments, the first LED structure 520 may further include an upper connecting portion 524 located between the upper conductive layer 522 and the LED light-emitting layer 523, and electrically connected to both the upper conductive layer 522 and the LED light-emitting layer 523. The upper connecting portion 524 is made of metal, including one or more of Al, Au, Rh, Ag, Cr, Ti, Pt, Sn, Cu, AuSn, TiW, etc.

[0223] In some embodiments, the upper conductive layer and the lower conductive layer can be metal layers or transparent conductive layers, such as ITO, FTO, or copper layers, which are formed to improve conductivity and transparency. In another embodiment, the lower conductive layer 521 can be a metal layer to form part of the metal bonding layer 570.

[0224] Although some features are described using the term "layer" here, it should be understood that these features are not limited to a single-layer structure and may also include multiple sub-layers. In some cases, a "structure" can be presented in the form of "layers".

[0225] In some embodiments, the area of ​​the bottom red LED light-emitting layer 523 may be equal to or greater than the area of ​​the middle green LED light-emitting layer 533. In some embodiments, the area of ​​the middle green LED light-emitting layer 533 may be equal to or greater than the area of ​​the top blue LED light-emitting layer 543.

[0226] In some embodiments, the first LED structure 520 is bonded to the substrate 510 via a metal bonding layer 570. The metal bonding layer 570 may be disposed on the substrate 510. One method is to grow the metal bonding layer 570 on the substrate 510. In some embodiments, the metal bonding layer 570 forms an electrical connection between a contact 511 on the substrate 510 and the first LED structure 520 located above the metal bonding layer 570, serving as a P-electrode. In some embodiments, the thickness of the metal bonding layer 570 is from about 0.1 μm to about 3 μm. In a preferred embodiment, the thickness of the metal bonding layer 570 is about 0.3 μm. The metal bonding layer may include an ohmic contact layer and a metal bonding layer. In some cases, the metal bonding layer 570 includes two metal layers. One of the metal layers is deposited at the bottom of the first LED structure 520. The corresponding bonding metal layer is deposited on the substrate 510. In some embodiments, the metal bonding layer 570 comprises Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or mixtures thereof. For example, if Au-Au bonding is selected, each of the two Au layers requires a Cr coating as an adhesive layer and a Pt coating as an anti-diffusion layer, with the Pt coating located between the Au layer and the Cr layer. The Cr and Pt layers are located at the top and bottom of the two bonded Au layers. In some embodiments, when the thicknesses of the two Au layers are approximately the same, mutual diffusion of Au on the two layers under high pressure and high temperature will bond the two layers together. Exemplary processes that can be used include eutectic bonding, hot-press bonding, and transient liquid phase (TLP) bonding.

[0227] In some embodiments, the metal bonding layer 570 may also function as a reflector, reflecting light emitted from the upper LED structure. In some embodiments, the metal bonding layer 570 may include a reflective layer 571. Moreover, the reflective layer 571 may be an alloy reflective layer.

[0228] In some embodiments, a second LED structure 530 is located above a first LED structure 520, and a third LED structure 540 is located above a second LED structure 530. The first LED structure 520, the second LED structure 530, and the third LED structure 540 are embedded within an insulating medium 580. The insulating medium 580 is transparent to light emitted from the first LED structure 520, the second LED structure 530, and the third LED structure 540. In some embodiments, the insulating medium 580 is made of a dielectric material, such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, SiCN, HfO2, Ta2O5, TiO2, ZrO2, La2O3, MgO, phosphosilicate glass (PSG), borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG), or bonding adhesives such as Micro Resist BCL-1200, or any combination thereof. In some embodiments, the insulating medium 580 can facilitate the passage of light emitted from the LED pixels. In some embodiments, the insulating medium 580 may include multiple portions, such as three embedded medium portions and two bonding medium portions. An embedded medium portion refers to the dielectric layer surrounding each LED structure; a bonding medium portion refers to the dielectric layer between two LED structures. The embedded medium portions and the bonding medium portions may have the same or different compositions.

[0229] In some embodiments, the first LED structure 520 is embedded in the embedding medium portion, and the surface of the embedding medium portion is smoothed or planarized by a chemical mechanical polishing method.

[0230] In some embodiments, the second LED structure 530 is bonded to the first LED structure 520 via a bonding medium. The second LED structure 530 is embedded within the embedding medium, and the surface of the embedding medium is smoothed or planarized by a chemical mechanical polishing method.

[0231] In some embodiments, the third LED structure 540 is bonded to the second LED structure 530 via a bonding medium. The third LED structure 540 is embedded within the embedding medium, and the surface of the embedding medium is smoothed or planarized by a chemical mechanical polishing method.

[0232] In some embodiments, a plurality of metal structures 550 are arranged around a first LED structure, a second LED structure, and a third LED structure.

[0233] In some embodiments, the plurality of metal structures 550 may include metal structures 550a to 550h. Each metal structure is isolated from the others by an insulating medium 580. The plurality of metal structures 550 may be interconnecting vias formed in the insulating medium 580. Figure 2 As shown in Figure A, metal structure 550a can connect the lower conductive layer 531 of the second LED structure 530 to the contacts on the substrate 510; metal structure 550c can connect the lower conductive layer 541 of the third LED structure 540 to the contacts on the substrate 510; metal structures 550b, 550d, 550f, and 550h can serve as common electrodes, connected to the corresponding upper conductive layers 542, 532, 522, and top electrode of the LED structure. Metal structures 550a and 550c can electrically connect the corresponding lower conductive layers 531 and 541 of the LED structure to the positive terminal of an external power supply. Metal structures 550b, 550d, 550f, and 550h can be disposed on the substrate 510, but are not directly electrically connected to the substrate 510. Metal structures 550b, 550d, 550f, and 550h can electrically connect the corresponding upper conductive layers 542, 532, and 522 of the LED structure to the negative terminal of an external power supply. The upper conductive layers 542, 532, and 522 can be flat, or have upward or downward slopes due to the height difference between the metal structure and the LED light-emitting layer. For example, when forming the upper conductive layers 542, 532, and 522, if the height of the metal structure is the same as that of the LED light-emitting layer, the upper conductive layers 542, 532, and 522 are substantially flat; if the height of the metal structure is higher than that of the LED light-emitting layer, the upper conductive layers 542, 532, and 522 include a slope rising from the edge of the LED light-emitting layer to the metal structure; if the height of the metal structure is lower than that of the LED light-emitting layer, the upper conductive layers 542, 532, and 522 include a slope descending from the edge of the LED light-emitting layer to the metal structure. Those skilled in the art will understand that upper conductive layers of any shape can be designed according to the specific requirements of the micro-LED pixels, and such designs are all within the scope of protection of this invention.

[0234] In some embodiments, the top electrode may include an upper conductive layer 542 and a current diffusion layer. The upper conductive layer 542 may be formed on the LED light-emitting layer 543 and extend to the entire surface of the microLED pixel array below the bottom of the microlens.

[0235] The current diffusion layer can be formed on the upper conductive layer 542 and has better conductivity than the upper conductive layer 542. The current diffusion layer does not cover the light-emitting area of ​​each micro-LED pixel.

[0236] In some embodiments, the lower end of the metal structure 550 is located on the substrate 510; and the upper end of the metal structure 550 extends to a position not lower than the top surface of the second or third LED structure; preferably, the upper end of the metal structure 550 extends to the top surface of the insulating medium 580 or the bottom of the microlens or directly to the bottom of the top pad.

[0237] In some embodiments, the lower ends of metal structures 550a and 550c may be individually electrically connected to contacts on substrate 510, and the upper ends may extend to a position not lower than the top surface of the second or third LED structure; preferably, the upper ends may extend to the top surface of insulating medium 580 or the bottom of microlens or directly to the bottom of top pad but not electrically connected to the top pad. The lower ends of metal structures 550b, 550d, 550f and 550h may not be electrically connected to contacts on substrate 510, and the upper ends may extend to a position not lower than the top surface of the second or third LED structure; preferably, the upper ends may extend to the top surface of insulating medium 580 or the bottom of microlens, or directly to the bottom of top pad and electrically connected to the top pad.

[0238] Those skilled in the art should understand that the number, layout, size, and connection method of the metal structure 550 and the top pads are not limited to... Figures 5A-5D The illustrated embodiment can be modified according to actual needs, such as increasing or decreasing the number of metal structures, adjusting the shape of the metal structures, etc., and all such modifications fall within the protection scope of this invention. Figures 5A-5D In the illustrated embodiment, metal structures 550b, 550d, 550f, and 550h can serve as common N-electrodes connected to the upper conductive layers 542, 532, and 522 corresponding to the LED structure, while metal structures 550a and 550c can serve as P-electrodes electrically connected to the lower conductive layers 531 and 541 corresponding to the LED structure. However, those skilled in the art should understand that the N-electrodes and P-electrodes of the LED structure are interchangeable. For example, metal structures 550b, 550d, 550f, and 550h can serve as common P-electrodes connected to the P-type epitaxial layer of each LED structure, while metal structures 550a and 550c can serve as N-electrodes electrically connected to the N-type epitaxial layer corresponding to the LED structure.

[0239] In some embodiments, the materials of the plurality of metal structures 550 may be conductive metals, alloys, compounds, or combinations thereof.

[0240] In some embodiments, such as Figure 5B As shown, a reflective layer 551 is disposed on the sidewalls of a plurality of metal structures 550. In some embodiments, the reflective layer is an alloy reflective layer.

[0241] In some embodiments, a plurality of metal structures substantially surround a first LED structure, a second LED structure, and a third LED structure, such that light emitted from the LED structures toward the metal structures is reflected by a reflective layer 551 and emitted from the top surface of a single LED pixel.

[0242] In some embodiments, the plurality of metal structures having the reflective layer 551 can be fabricated by a combination of deposition, photolithography, and etching processes. In some embodiments, the plurality of metal structures having the reflective layer 551 can also be fabricated by other suitable methods.

[0243] In some embodiments, a microlens 560 is formed on the top surface of the third LED structure 540. In some embodiments, the microlens 560 alters the light path emitted by a single microLED pixel by making the light emitted by the LED device more focused or more diffused according to design requirements.

[0244] In some embodiments, the microlens 560 may be made of a variety of materials that are transparent within the wavelength range emitted by a single microLED pixel. Exemplary transparent materials for the microlens 560 include polymers, dielectric materials, and semiconductor materials. In some embodiments, the dielectric material includes one or more materials, such as silicon oxide, silicon nitride, silicon carbide, titanium oxide, zirconium oxide, aluminum oxide, etc. In some embodiments, the microlens 560 is made of photoresist.

[0245] In some embodiments, the microlens 560 is typically hemispherical in shape. In some embodiments, the central axis of the microlens 560 is aligned with or the same as the central axis of a single microLED pixel without a lens.

[0246] It is important to understand that a complete display panel comprises an array of multiple individual pixels and numerous microlenses. Furthermore, there is no one-to-one correspondence between microlenses and pixel light sources, nor is there a one-to-one correspondence between pixel driver circuits (not shown) and pixel light sources. Pixel light sources can also be made from multiple independent light-emitting elements, such as single-pixel LEDs connected in parallel. In some embodiments, a microlens 560 can cover multiple lensless single LED pixels.

[0247] Each microlens 560 has positive optical power and is positioned to reduce the divergence or viewing angle of light emitted from a corresponding microLED pixel light source. In one example, the beam emitted from the pixel light source has a fairly wide original divergence angle. In one embodiment, the original angle of the edge rays of the beam relative to the orthogonal axis perpendicular to the substrate 510 is greater than 60 degrees. The light is bent by the microlens 560, such that the new edge rays now have a reduced divergence angle. In one embodiment, the reduced angle is less than 30 degrees. The microlenses in the microlens array are typically identical. Examples of microlenses include spherical microlenses, aspherical microlenses, Fresnel microlenses, and cylindrical microlenses.

[0248] Microlenses 560 typically have a flat side and a curved side. Figures 5A-5D In this configuration, the bottom of the microlens 560 is flat, and the top of the microlens 560 is curved. Typical shapes of the base for each microlens 560 include circular, square, rectangular, and hexagonal. Individual microlenses in the microlens array of the display panel may be the same or different in terms of shape, curvature, optical power, size, base, and spacing. In some embodiments, the microlens 560 matches the shape of a single LED pixel. In one example, the shape of the base of the microlens 560 is the same as the shape of a single LED pixel. In another example, the shape of the base of the microlens 560 is different from the shape of a single LED pixel; for example, a microlens with a circular base has the same width as a single LED pixel, but its area is smaller because the microlens base is circular while the single LED pixel base is square. In some embodiments, the area of ​​the microlens base portion is smaller than the area of ​​the pixel light source. In some embodiments, the surface area of ​​the microlens base portion is the same as or larger than the area of ​​the pixel light source.

[0249] Some embodiments achieve brightness enhancement by integrating a microlens array onto the display panel. In some instances, due to the light-focusing effect of the microlenses, the brightness with the microlens array is four times that without the microlens array in the direction perpendicular to the display surface. In alternative embodiments, the brightness enhancement factor can vary depending on the design of the microlens array and optical spacers. For example, an enhancement factor greater than 8 can be achieved.

[0250] Microlenses can be fabricated using a variety of methods, including deposition, patterning, and etching.

[0251] Figure 6A A top view of a micro LED pixel with an alloy reflective structure according to a sixth embodiment of the present invention is shown. Figure 6B A schematic cross-sectional view of a micro-LED pixel with an alloy reflective structure along line AA is shown according to a sixth embodiment of the present invention. Figure 6C A schematic cross-sectional view of a micro-LED pixel with an alloy reflective structure along line BB is shown according to a sixth embodiment of the present invention. Figures 6A-6C As shown, the micro-LED pixel with alloy reflective structure is a tri-color micro-LED pixel, comprising: a substrate 610, a first LED structure 620, a second LED structure 630, a third LED structure 640, a metal structure 650, and a microlens 660. The first LED structure 620, the second LED structure 630, and the third LED structure 640 are not coaxially stacked. Instead, they are offset from each other from the top.

[0252] In some embodiments, the first LED structure 620 may include a lower conductive layer 621, an upper conductive layer 622, and a red LED light-emitting layer 623 located between the lower conductive layer 621 and the upper conductive layer 622; the second LED structure 630 may include a lower conductive layer 631, an upper conductive layer 632, and a green LED light-emitting layer 633 located between the lower conductive layer 631 and the upper conductive layer 632; the third LED structure 640 may include a lower conductive layer 641, an upper conductive layer 642, and a blue LED light-emitting layer 643 located between the lower conductive layer 641 and the upper conductive layer 642. Those skilled in the art should understand that the LED light-emitting layer 623 in the first LED structure 620 is not limited to a red light-emitting layer, the LED light-emitting layer 633 in the second LED structure 630 is not limited to a green light-emitting layer, and the LED light-emitting layer 643 in the third LED structure 640 is not limited to a blue light-emitting layer. That is, the LED light-emitting layers 623, 633, and 643 can be any color light-emitting layers as needed. The red, green, and blue light-emitting layers or LED structures described herein are for illustrative purposes only and are not intended to be limiting.

[0253] In some embodiments, LED light-emitting layers 623, 633, and 643 may include a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer therebetween. The light-emitting layer may be, but is not limited to, a multi-quantum-well structure. The first conductivity type may be N-type, and the second conductivity type may be P-type; or the first conductivity type may be P-type, and the second conductivity type may be N-type. The N-type semiconductor epitaxial layer of each of the three color light-emitting layers includes, but is not limited to, N-type Si-doped GaN, Si-doped AlGaN, Si-doped AlGaInP, Si-doped GaAs, or Si-doped AlInP; the P-type semiconductor epitaxial layer includes, but is not limited to, Mg-doped GaN, Mg-doped AlGaN, Mg-doped InGaN, Mg-doped InAlGaN, Mg-doped AlInP, Mg-doped AlGaInP, Mg-doped GaP, or C-doped GaP. The quantum well layer includes, but is not limited to, InGaN / GaN cycling and InGaP / AlGaInP cycling.

[0254] In some embodiments, the first LED structure 620 may further include an upper connecting portion 624 located between the upper conductive layer 622 and the LED light-emitting layer 623, and electrically connected to both the upper conductive layer 622 and the LED light-emitting layer 623. The upper connecting portion 624 is made of a metal, including one or more of Al, Au, Rh, Ag, Cr, Ti, Pt, Sn, Cu, AuSn, TiW, etc.

[0255] In some embodiments, the upper conductive layer and the lower conductive layer can be metal layers or transparent conductive layers, such as ITO, FTO, or copper layers, which are formed to improve conductivity and transparency. In another embodiment, the lower conductive layer 621 can be a metal layer to form part of a metal bonding layer.

[0256] Although some features are described using the term "layer" here, it should be understood that these features are not limited to a single-layer structure and may also include multiple sub-layers. In some cases, a "structure" can be presented in the form of "layers".

[0257] In some embodiments, the first LED structure 620, the second LED structure 630, and the third LED structure 640 are adjacent to each other but do not overlap.

[0258] In some embodiments, the first LED structure 620 is bonded to the substrate 610 via a metal bonding layer 671. The metal bonding layer 671 may be disposed on the substrate 610. One method is to grow the metal bonding layer 671 on the substrate 610. In some embodiments, the metal bonding layer 671 forms an electrical connection between a contact 611 on the substrate 610 and the first LED structure 620 located above the metal bonding layer 671, serving as a P-electrode. In some embodiments, the thickness of the metal bonding layer 671 is from about 0.1 μm to about 3 μm. In a preferred embodiment, the thickness of the metal bonding layer 671 is about 0.3 μm. The metal bonding layer may include an ohmic contact layer and a metal bonding layer. In some cases, the metal bonding layer 671 includes two metal layers. One of the metal layers is deposited at the bottom of the first LED structure 620. The corresponding bonding metal layer is deposited on the substrate 610. In some embodiments, the metal bonding layer 671 comprises Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or mixtures thereof. For example, if Au-Au bonding is selected, each of the two Au layers requires a Cr coating as an adhesive layer and a Pt coating as an anti-diffusion layer, with the Pt coating located between the Au layer and the Cr layer. The Cr and Pt layers are located at the top and bottom of the two bonded Au layers. In some embodiments, when the thicknesses of the two Au layers are approximately the same, mutual diffusion of Au on the two layers under high pressure and high temperature will bond the two layers together. Exemplary processes that can be used include eutectic bonding, hot-press bonding, and transient liquid phase (TLP) bonding.

[0259] In some embodiments, the metal bonding layer 671 may also function as a reflector, reflecting light emitted from the LED structure above. In some embodiments, the metal bonding layer 671 may include a reflective layer. Furthermore, the reflective layer may include an alloy reflective structure.

[0260] In some embodiments, the second LED structure 630 is bonded to a metal pillar 673 on the substrate 610 via a metal bonding layer 672. The third LED structure 640 is bonded to a metal pillar 675 on the substrate 610 via a metal bonding layer 674. In some embodiments, the lower end of the metal pillar 673 is electrically connected to a contact 611 on the substrate 610, and the upper end is electrically connected to the metal bonding layer 672, serving as a P-type electrode. One method is to grow the metal pillar 673 on the substrate 610. In some embodiments, the upper end of the metal pillar 673 is not lower than the top of the first LED structure 620, thereby enabling the second LED structure 630 to be bonded to the metal pillar 673. In some embodiments, the lower end of the metal pillar 675 is electrically connected to a contact 611 on the substrate 610, and the upper end is electrically connected to the metal bonding layer 674, serving as a P-type electrode. One method is to grow the metal pillar 675 on the substrate 610. In some embodiments, the upper end of the metal pillar 675 is not lower than the top of the second LED structure 630, so that the third LED structure 640 can be bonded to the metal pillar 675.

[0261] In some embodiments, the metal bonding layers 672 and 674 may also function as reflectors, reflecting light emitted from the upper LED structure. In some embodiments, the metal bonding layers 672 and 674 may include reflective layers. Furthermore, the reflective layers may include alloy reflective structures.

[0262] In some embodiments, the first LED structure 620, the second LED structure 630, and the third LED structure 640 are directly bonded together via a metal bonding layer, and metal bonding has lower requirements for surface flatness. Therefore, the micro LED pixel described in this invention can combine the advantages of both metal bonding and direct bonding.

[0263] In some embodiments, the first LED structure 620, the second LED structure 630, and the third LED structure 640 are embedded within an insulating medium 680. The insulating medium 680 is transparent to light emitted from the first LED structure 620, the second LED structure 630, and the third LED structure 640. In some embodiments, the insulating medium 680 is made of a dielectric material, such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, SiCN, HfO2, Ta2O5, TiO2, ZrO2, La2O3, MgO, phosphosilicate glass (PSG), borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG), or bonding adhesives such as Micro Resist BCL-1200, or any combination thereof. In some embodiments, the insulating medium 680 allows light emitted from the LED pixels to pass through.

[0264] In some embodiments, the metal structure 650 surrounds the outer periphery of the first LED structure 620, the second LED structure 630, and the third LED structure 640. In some embodiments, the metal structure 650 can serve as a common electrode connecting the upper conductive layer of each LED structure, functioning as an N-electrode. That is, the metal structure 650 can electrically connect the upper conductive layers 642, 632, and 622 of the corresponding LED structures to the negative terminal of an external power supply.

[0265] However, those skilled in the art should note that the N-type and P-type electrodes in an LED structure are interchangeable. For example, the metal structure 650 can serve as a common P-type electrode, connected to the P-type epitaxial layer of each LED structure, while the corresponding N-type epitaxial layer of the LED structure is electrically connected to the metal bonding layer.

[0266] The upper conductive layers 642, 632, and 622 can be flat, or have upward or downward slopes due to the height difference between the metal structure and the LED light-emitting layer. For example, when forming the upper conductive layers 642, 632, and 622, if the height of the metal structure is the same as that of the LED light-emitting layer, the upper conductive layers 642, 632, and 622 are substantially flat; if the height of the metal structure is higher than that of the LED light-emitting layer, the upper conductive layers 642, 632, and 622 include a slope rising from the edge of the LED light-emitting layer to the metal structure; if the height of the metal structure is lower than that of the LED light-emitting layer, the upper conductive layers 642, 632, and 622 include a slope descending from the edge of the LED light-emitting layer to the metal structure. Those skilled in the art will understand that upper conductive layers of any shape can be designed according to the specific requirements of the micro-LED pixels, and such designs are all within the scope of protection of this invention.

[0267] In some embodiments, the lower end of the metal structure 650 may be located on the substrate 610 but not electrically connected to the contacts on the substrate 610; and the upper end of the metal structure 650 may extend to a position not lower than the top surface of the second or third LED structure; preferably, the upper end of the metal structure 650 may extend to the top surface of the insulating medium 680 or the bottom of the microlens or directly to the bottom of the top pad and be electrically connected to the top pad. In some embodiments, the metal structure 650 may be used as an optical isolation structure to eliminate crosstalk.

[0268] In some embodiments, a reflective layer 651 is disposed on the sidewall of the metal structure 650. In some embodiments, the metal structure 650 substantially surrounds the first LED structure, the second LED structure, and the third LED structure, such that light emitted from the LED structures toward the metal structure 650 is reflected by the reflective layer 651 and emitted from the top surface of a single LED pixel. In some embodiments, the reflective layer 651 may be an alloy reflective structure.

[0269] In some embodiments, bottom reflective layers 691, 692, and 693 are disposed between the metal bonding layer and the LED structure. In some embodiments, bottom reflective layers 691, 692, and 693 may be alloy reflective structures.

[0270] In some embodiments, a microlens 660 is formed on the top surface of an insulating medium 680.

[0271] While various embodiments of the invention have been described above, it should be understood that they are merely examples and not limitations. It will be apparent to those skilled in the art that various combinations, modifications, and alterations can be made therein without departing from the spirit and scope of the invention. Therefore, the breadth and scope of the invention disclosed herein should not be limited to the exemplary embodiments described above, but should be defined solely by the appended claims and their equivalents.

Claims

1. A miniature LED pixel with an alloy reflective structure, characterized in that, include: LED structure; as well as A metal layer located beneath the LED structure, wherein the metal layer includes an alloy reflective layer, and the alloy reflective layer is an aluminum alloy or a silver alloy.

2. The micro LED pixel with an alloy reflective structure according to claim 1, characterized in that, The alloy reflective layer is connected to the LED structure.

3. The micro LED pixel with an alloy reflective structure according to claim 1, characterized in that, The aluminum alloys include AlCu, AlSi, AlMg, AlNi, AlSn, and AlMn.

4. The micro LED pixel with an alloy reflective structure according to claim 1, characterized in that, The silver alloys include AgCu, AgNi, AgZn, AgPd, AgMg, and AgW.

5. The micro LED pixel with an alloy reflective structure according to claim 2, characterized in that, Also includes: An adhesive layer located between the alloy reflective layer and the LED structure.

6. The micro LED pixel with an alloy reflective structure according to claim 5, characterized in that, The adhesive layer is made of materials including Cr, Ti, Ni, or Ta.

7. The micro LED pixel with an alloy reflective structure according to claim 1, characterized in that, The LED structure includes a lower conductive layer, an upper conductive layer, and an LED light-emitting layer between the lower conductive layer and the upper conductive layer.

8. The micro LED pixel with an alloy reflective structure according to claim 7, characterized in that, The LED light-emitting layer includes a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and a light-emitting layer between the first semiconductor epitaxial layer and the second semiconductor epitaxial layer.

9. The micro LED pixel with an alloy reflective structure according to claim 8, characterized in that, The first semiconductor epitaxial layer is P-type, and the second semiconductor epitaxial layer is N-type; or the first semiconductor epitaxial layer is N-type, and the second semiconductor epitaxial layer is P-type; the material of the first semiconductor epitaxial layer is a Ga-containing III-V group semiconductor material; the light-emitting layer includes a multi-quantum well layer.

10. The micro LED pixel with an alloy reflective structure according to claim 7, characterized in that, The lower conductive layer and the upper conductive layer are transparent conductive layers.

11. The micro LED pixel with an alloy reflective structure according to claim 1, characterized in that, Also includes: A substrate, wherein the LED structure is bonded to the substrate via the metal layer.

12. The micro LED pixel with an alloy reflective structure according to claim 11, characterized in that, The metal layer further includes a connection between the metal layer and a contact on the substrate, and the connection is electrically connected between the metal layer and the contact on the substrate.

13. The micro LED pixel with an alloy reflective structure according to claim 12, characterized in that, The material of the connecting part is a metal, including one or more of Al, Au, Rh, Ag, Cr, Ti, Pt, Sn, Cu, AuSn, and TiW.

14. The micro LED pixel with an alloy reflective structure according to claim 1, characterized in that, Also includes: A conductive layer located above the LED structure, wherein the conductive layer electrically connects multiple LED structures.

15. The micro LED pixel with an alloy reflective structure according to claim 14, characterized in that, Also includes: A metal structure located above and electrically connected to the conductive layer, wherein the metal structure is located in the gap between the plurality of LED structures.

16. The micro LED pixel with an alloy reflective structure according to claim 15, characterized in that, The metal structure serves as a common electrode for connecting each LED structure.

17. The micro LED pixel with an alloy reflective structure according to claim 15, characterized in that, The material of the metal structure is aluminum alloy or silver alloy.

18. The micro LED pixel with an alloy reflective structure according to claim 15, characterized in that: A gap is formed between adjacent microLED structures; the metal structure is formed at the bottom of the gap; or The tops of adjacent microLED structures are interconnected to form an interconnect top; gaps are formed between adjacent microLED structures and below the interconnect top; the metal structure is formed on top of the interconnect top and around the top of the microLED structure.

19. The micro LED pixel with an alloy reflective structure according to claim 1, characterized in that, There is more than one microLED structure; the microLED structures are stacked in the vertical direction; the interconnect conductive structure is perpendicular to the bottom of the microLED structure; each interconnect conductive structure is connected to the bottom of each microLED.

20. The micro LED pixel with an alloy reflective structure according to claim 19, characterized in that, The metal layer is formed on the sidewall surface of the interconnected conductive structure.

21. The micro LED pixel with an alloy reflective structure according to claim 20, characterized in that, The metal layer covers the entire surface of the interconnected conductive structure.

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