Full color light emitting diode microdisplay and method of manufacturing the same

Abstract

A full-color light emitting diode microdisplay and a method of manufacturing the same are disclosed. The full-color LED microdisplay has a plurality of pixels, each pixel including sub-pixels: a first LED comprising a blue / green dual-wavelength LED structure for emitting blue light; a second LED comprising the blue / green dual-wavelength LED structure for emitting green light; and a third LED comprising a red LED structure for emitting red light. The blue / green dual-wavelength LED structure includes a dual-wavelength MQWs active region of a first material having two emission peaks. The dual-wavelength MQWs active region includes a first quantum well stack, a second quantum well stack, and a third quantum well stack. The first quantum well stack and the third quantum well stack are configured for generating the blue light, and the second quantum well stack is configured for generating the green light. The red LED structure further includes a red light-emitting MQWs active region of a second material having a second emission peak.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 314,481, filed February 28, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention generally relates to a full-color light-emitting diode (LED) microdisplay, and more specifically, to a heterogeneous integrated full-color LED microdisplay of indium gallium nitride (InGaN) blue / green dual-wavelength LEDs and aluminum gallium indium phosphide (AlGaInP) red LEDs, and a method for manufacturing the same. Background Technology

[0004] Virtual reality (VR) and augmented reality (AR) devices offer users a unique sense of immersion and interactive experience. In the near future, VR / AR technology has the potential to be applied in education, healthcare, professional training, instruction, and entertainment. Microdisplays with tiny dimensions (e.g., <1 inch) are the most important devices in VR / AR applications. They are receiving increasing attention from industry. Liquid crystal (LC) and organic light-emitting diode (OLED) technologies are widely used in displays for televisions, personal computers, and smartphones. However, both have unavoidable drawbacks. VR / AR devices require high brightness, but LC-based microdisplays rely on light modulation, which has low energy efficiency, resulting in high power consumption. Furthermore, LC technology also suffers from low contrast and long response times. OLEDs are self-emissive elements with better efficiency and contrast, but the reliability of OLED devices remains an issue, especially under high brightness conditions. Inorganic LEDs are a suitable alternative to OLEDs. LEDs are characterized by self-emission, high efficiency, high brightness, and long lifespan. They can provide sufficient brightness and contrast for outdoor applications. Therefore, LED technology has attracted researchers and engineers as the next-generation technology for microdisplays.

[0005] Many companies have developed various types of mass transfer technologies to manufacture large-size (e.g., >5 inches) LED displays. In mass transfer, micro-LED devices on red, green, and blue LED epitaxial wafers are diced into individual LED pixels and transferred to a driver backplane. Typical transfer methods include pick-and-place using a transfer head, fluid transfer, and microprinting. These methods are theoretically applicable to LED microdisplays (<1 inch), but transfer accuracy, time consumption, cost, and transfer benefits remain significant challenges for this technology. To overcome the technical difficulties of mass transfer, monolithic fabrication of LED microdisplays is a more competitive approach. Due to the small size of the microdisplay, the entire microdisplay can be fabricated directly on the original substrate and integrated with driver integrated circuits (ICs). This type of monolithic LED microdisplay is mostly monochrome because only one type of monochrome LED epitaxial wafer is used. Due to limitations in material emission characteristics, it is difficult to grow LED epitaxial wafers that emit RGB three colors or white. To achieve full color, additional structures need to be integrated, such as applying color conversion layers or integrating monolithic LED arrays of other colors.

[0006] For example, the inventors of this application previously proposed a full-color LED microdisplay fabricated from a monolithic blue / green dual-wavelength LED array and a red quantum dot (QD) color conversion pattern (see U.S. Patent No. 10,943,532B2). The microdisplay can be driven by a passive matrix or an active matrix. RGB color filters (CFs) are coated on the corresponding sub-pixels for color purification. However, a problem with previous work is that even though the blue and green pixels can provide high brightness, the brightness of the microdisplay is still limited by the performance of the red QDs.

[0007] QD materials are widely used in monolithic LED microdisplays as color conversion layers to achieve full-color performance. Compared to traditional phosphors, QD materials have narrow emission peaks, tunable colors, and a wider color gamut. However, the performance of QD materials for LED microdisplays is still not ideal. For very small pixel pitches, QD patterns must be small enough, but methods for forming such tiny QD patterns are not yet mature. Furthermore, considering light extraction, optical crosstalk, and viewing angle issues, QD materials cannot be too thick. However, due to the aggregation effect of QDs, they typically have low optical density. This limits the overall conversion efficiency of the QD color conversion layer. QD degradation is also a concern when the microdisplay operates under high brightness conditions. As an alternative to color conversion schemes, all-inorganic LED microdisplays are a better choice due to their high efficiency and long lifespan. InGaN materials have high luminous efficiency in the blue and green light bands, while AlGaInP materials have high efficiency in the red light band. Fabricating monochromatic R / G / B monolithic LED arrays using only InGaN or only AlGaInP materials would be very complex.

[0008] For example, one patent proposes a monolithically integrated full-color LED microdisplay based on a tri-color InGaN LED chip, which displays red, green, and blue at different current densities (see US Patent No. 10,861,398B2). All pixels are identical, and the colors are controlled by the driving current, with the brightness of each color adjusted by the on / off duty cycle of the corresponding pixel. The microdisplay system also features pixel-level optics to collimate and directionally modulate the light emitted from the pixels. However, the proposed microdisplay exhibits an excessively large difference in brightness between red and blue-green light because the InGaN material is too inefficient in the red light band. To balance the effect used for color mixing, the brightness of the microdisplay must be very low, thus failing to meet the high brightness requirements of microdisplays. The driving method for controlling both the current and duty cycle within the same pixel may also be overly complex. Furthermore, due to the lack of a color filter (CF), the colors emitted by the tri-color LEDs are impure.

[0009] The invention disclosed in U.S. Patent No. 9,041,025,B2 describes a monolithic UV LED array integrated with an active matrix (AM) complementary metal-oxide-semiconductor (CMOS) driver. Solder bumps are deposited on the AM driver side, and the LED array is bonded to the driver chip via flip-chip bonding. Red, green, and blue phosphors are filled in a silicon mold, which is fixed to the UV LED array as a color converter. The problem with this invention is that this method is only suitable for large pixels because the phosphors are relatively large (micrometer-scale). Unabsorbed UV LED light sources may also be harmful to the human eye. This prevents the use of this method in microdisplay applications.

[0010] Therefore, there is a need in the art for an improved full-color LED microdisplay capable of eliminating or at least reducing the drawbacks and problems described above. Furthermore, other desirable features and advantages of the invention will become apparent from the accompanying drawings and the background description herein, as well as from the detailed description below and the appended claims. Summary of the Invention

[0011] This paper presents a full-color LED microdisplay that is achieved through heterogeneous integration of InGaN blue / green dual-wavelength LEDs and AlGaInP red LEDs.

[0012] According to a first embodiment of the present invention, a full-color LED microdisplay having multiple pixels is disclosed. Each pixel includes: a first LED comprising a blue / green dual-wavelength LED structure for emitting blue light; a second LED comprising a blue / green dual-wavelength LED structure for emitting green light; and a third LED comprising a red LED structure for emitting red light. The blue / green dual-wavelength LED structure includes a dual-wavelength MQWs active region of a first material having two emission peaks. The dual-wavelength MQWs active region includes a first quantum well stack, a second quantum well stack, and a third quantum well stack. The first and third quantum well stacks are configured to generate blue light, and the second quantum well stack is configured to generate green light. The red LED structure further includes a red-emitting MQWs active region of a second material having a second emission peak.

[0013] In some embodiments, the first material is indium gallium nitride (InGaN), and the second material is aluminum gallium indium phosphide (AlGaInP).

[0014] In some embodiments, the first quantum well stack and the third quantum well stack each include one or more blue emitting quantum wells (QWs) and one or more quantum barrier layers; the second quantum well stack includes one or more green emitting QWs and one or more quantum barrier layers.

[0015] In some embodiments, the first quantum well stack comprises three blue-emitting QWs; the second quantum well stack comprises one green-emitting QW; and the third quantum well stack comprises one blue-emitting QW.

[0016] In some embodiments, each blue emitting QW is an In nanotube with an arbitrary thickness between 1 nm and 10 nm. x Ga 1-x N layers, where x is any value between 0.1 and 0.2. The green emitting QW is an In layer with an arbitrary thickness between 1 nm and 5 nm. y Ga 1-y N layers, where y is any value between 0.2 and 0.3.

[0017] In some embodiments, the blue / green dual-wavelength LED structure further includes: a buffer layer comprising an undoped gallium nitride (GaN) layer; an n-doped semiconductor layer comprising a Si-doped n-GaN layer and an InGaN shallow well; and a p-doped semiconductor layer comprising a Mg-doped p-GaN layer and a Mg-doped p-In layer stacked on top of the Mg-doped p-GaN layer. 0.02 Ga 0.98 N layers.

[0018] In some embodiments, the red LED structure further includes: an n-side layer comprising a Si-doped n-GaAs layer, a Si-doped n-AlGaInP layer, and a Si-doped n-AlInP layer; and a p-side layer comprising a Zn- or Mg-doped p-AlInP layer and a Zn- or Mg-doped p-GaP layer. The active region of the red emitting MQWs is sandwiched between the n-side and p-side layers, and includes one or more AlGaInP quantum wells (QWs) sandwiched between two AlGaInP quantum barrier layers.

[0019] In some embodiments, the blue / green dual-wavelength LED structure further includes an electron blocking layer (EBL). The EBL further includes Mg doping at a concentration of 1 × 10⁻⁶. 17 cm -3 and 1×10 20 cm -3 One or more Al between x Ga 1-x N and In y Ga 1-y N layers. Preferably, x is any value between 0.01 and 0.3 and y is any value between 0 and 0.3.

[0020] In some embodiments, the dual-wavelength MQWs active region and the red-emitting MQWs active region are formed on two different vertically non-overlapping epitaxial layers.

[0021] In some embodiments, the active region of the dual-wavelength MQWs is located at a lower vertical position closer to the substrate than the active region of the red-emitting MQWs.

[0022] In some embodiments, the blue / green dual-wavelength LED structure further includes an n-doped semiconductor layer and a p-doped semiconductor layer. The red LED structure further includes an n-side layer and a p-side layer. The active regions of the dual-wavelength MQWs are sandwiched between the n-doped semiconductor layer and the p-doped semiconductor layer. The active regions of the red emitting MQWs are sandwiched between the n-side layer and the p-side layer. Preferably, for the blue / green dual-wavelength LED, the p-doped semiconductor layer is above the active regions of the dual-wavelength MQWs and the n-doped semiconductor layer; for the red LED, the n-side layer is above the active regions of the red emitting MQWs and the p-side layer.

[0023] In some embodiments, the first LED, the second LED, and the third LED are formed above the driver panel via a plurality of pixel bonding pads. Preferably, the driver panel is a CMOS driver chip, a thin-film transistor (TFT) driver backplane, a gate-in-panel (GIP) circuit, or other driver panel including circuitry on the panel substrate.

[0024] In some embodiments, the active region of the dual-wavelength MQWs is located at a lower vertical position closer to the driver panel than the active region of the red-emitting MQWs.

[0025] In some embodiments, the blue / green dual-wavelength LED structure further includes an n-doped semiconductor layer and a p-doped semiconductor layer. The red LED structure further includes an n-side layer and a p-side layer. The active regions of the dual-wavelength MQWs are sandwiched between the n-doped semiconductor layer and the p-doped semiconductor layer. The active regions of the red emitting MQWs are sandwiched between the n-side layer and the p-side layer. Preferably, for the blue / green dual-wavelength LED, the n-doped semiconductor layer is above the active regions of the dual-wavelength MQWs and the p-doped semiconductor layer; for the red LED, the n-side layer is above the active regions of the red emitting MQWs and the p-side layer.

[0026] According to a second embodiment of the present invention, a method for manufacturing a full-color LED microdisplay is provided. The full-color LED microdisplay comprises: a first LED having a blue / green dual-wavelength LED structure for emitting blue light; a second LED having a blue / green dual-wavelength LED structure for emitting green light; and a third LED including a red LED structure for emitting red light. The method comprises: (1) forming a first monolithic LED array having a blue / green dual-wavelength LED structure on a substrate, including the steps of depositing or growing a buffer layer, an n-doped semiconductor layer, a dual-wavelength multiple quantum well (MQWs) active region of a first material having two emission peaks, an electron blocking layer (EBL), and a p-doped semiconductor layer on the substrate; (2) forming a second monolithic LED array having a red LED structure on a gallium arsenide (GaAs) substrate, including the steps of depositing or growing an n-side layer, a red emitting MQWs active region of a second material having a second emission peak, and a p-side layer on the GaAs substrate; (3) performing flip-chip bonding to heterogeneously integrate the first monolithic LED array and the second monolithic LED array; and (4) removing the GaAs substrate by performing dry etching, wet etching, or a combination of dry etching and wet etching.

[0027] In some embodiments, the step of forming a first monolithic LED array having a blue / green dual-wavelength LED structure further includes: (1) applying an etch mask comprising a photoresist, silicon dioxide (SiO2), or silicon nitride (Si3N4); (2) performing etching to remove a portion of all epitaxial layers above the substrate to expose the first LED, the second LED, and a multilayer structure, wherein the multilayer structure is used to house a third LED and connect the third LED to the first monolithic LED array; (3) depositing a current diffusion layer (CSL), an n-metal layer, and a p-metal layer on the first LED and the second LED respectively by evaporation or sputtering, wherein the CSL is an indium tin oxide (ITO) or Ni / Au metal stack; (4) depositing and patterning the n-metal layer on the CSL of the first LED and the second LED respectively; and (5) coating a blue color filter (CF) and a green color filter on top of the first LED and the second LED respectively and performing hard baking.

[0028] In some embodiments, the step of forming a second monolithic LED array having a red LED structure further includes: (1) applying an etch mask comprising a photoresist, silicon dioxide (SiO2), or silicon nitride (Si3N4); (2) performing etching to remove a portion of the epitaxial layer above the GaAs substrate to expose a third LED; (3) depositing and patterning a p-metal layer and an n-metal layer on the third LED as p-electrodes and n-electrodes; (4) depositing and patterning a passivation layer, wherein the passivation layer is SiO2, Si3N4, Al2O3, hard-baked photoresist, an organic polymer, or any combination thereof; and (5) depositing and patterning p-metal bumps on the p-metal layer for electrically connecting the third LED to the first monolithic LED array.

[0029] In some embodiments, the step of forming a second monolithic LED array with a red LED structure further includes the step of depositing or growing an etch stop layer (ESL). Preferably, the ESL is provided to improve etch selectivity when removing the GaAs substrate.

[0030] In some embodiments, the flip-chip bonding step further includes: coating an underfill layer on the first monolithic LED array and the second monolithic LED array; and applying a temperature of 150°C to 300°C for 0.5 minutes to 10 minutes to bond the first monolithic LED array and the second monolithic LED array and cure the underfill layer.

[0031] In some embodiments, the method further includes: performing flip-chip bonding to bond a first monolithic LED array onto a driver panel; and removing a substrate by performing dry etching, wet etching, or a combination of dry and wet etching prior to performing flip-chip bonding to heterogeneously integrate the first and second monolithic LED arrays. Preferably, the driver panel is a CMOS driver chip, a thin-film transistor (TFT) driver backplane, a gate-in-panel (GIP) circuit, or other driver panel including circuitry on the panel substrate.

[0032] This summary is provided to introduce, in a simplified form, some concepts that will be further described in the following detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter. Other aspects and advantages of the invention are disclosed as shown in the embodiments below. Attached Figure Description

[0033] The accompanying drawings contain figures for further illustration and elucidation of the above and other aspects, advantages, and features of the invention. It should be understood that these drawings depict only certain embodiments of the invention and are not intended to limit its scope. It should also be understood that these drawings are shown for simplicity and clarity and are not necessarily drawn to scale. The invention will now be described and explained with additional features and details using the accompanying drawings, in which:

[0034] Figure 1 A schematic cross-sectional view of the active region of the blue / green dual-wavelength LED epitaxial wafer and multiple quantum wells (MQWs) is shown.

[0035] Figure 2A A schematic cross-sectional view of a blue / green dual-wavelength LED epitaxial wafer for manufacturing a full-color LED microdisplay, according to certain embodiments of the present invention, is shown.

[0036] Figure 2B It shows the result of Figure 2A The electroluminescence spectrum of an LED chip fabricated from a blue / green dual-wavelength LED epitaxial wafer is shown in the figure.

[0037] Figure 3A A schematic cross-sectional view of a red LED epitaxial wafer for manufacturing a full-color LED microdisplay, according to certain embodiments of the present invention, is shown.

[0038] Figure 3B It shows the result of Figure 3A The electroluminescence spectrum of an LED chip fabricated from a red LED epitaxial wafer is shown in the image.

[0039] Figure 4AA cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the first step in the fabrication of a monolithic LED array with a blue / green dual-wavelength LED structure for a first type of full-color LED microdisplay;

[0040] Figure 4B A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating a second step in the fabrication of a monolithic LED array with a blue / green dual-wavelength LED structure for a first type of full-color LED microdisplay;

[0041] Figure 4C A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the third step in the fabrication of a monolithic LED array with a blue / green dual-wavelength LED structure for a first type of full-color LED microdisplay;

[0042] Figure 5A A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the first step in the fabrication of a monolithic LED array with a red LED structure for a first type of full-color LED microdisplay;

[0043] Figure 5B A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating a second step in the fabrication of a monolithic LED array with a red LED structure for a first type of full-color LED microdisplay;

[0044] Figure 5C A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the third step in the fabrication of a monolithic LED array with a red LED structure for a first type of full-color LED microdisplay;

[0045] Figure 6A A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the... Figure 5C The second monolithic LED array and Figure 4C The first step in integrating a first monolithic LED array is used to realize a first type of full-color LED microdisplay.

[0046] Figure 6B A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the... Figure 5C The second monolithic LED array and Figure 4C The first monolithic LED array phase integration is used in the second step to realize the first type of full-color LED microdisplay;

[0047] Figure 6CIt was shown from another direction Figure 6B A cross-sectional view of an exemplary LED pixel;

[0048] Figure 7 A top view of an exemplary device of a full-color LED microdisplay according to a first embodiment of the present invention is shown;

[0049] Figure 8A A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the first step in the fabrication of a monolithic LED array with a blue / green dual-wavelength LED structure for a second type of full-color LED microdisplay;

[0050] Figure 8B A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating a second step in the fabrication of a monolithic LED array with a blue / green dual-wavelength LED structure for a second type of full-color LED microdisplay;

[0051] Figure 8C A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the third step in the fabrication of a monolithic LED array with a blue / green dual-wavelength LED structure for a second type of full-color LED microdisplay;

[0052] Figure 9A A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the first step in the fabrication of a monolithic LED array with a red LED structure for a second type of full-color LED microdisplay;

[0053] Figure 9B A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating a second step in the fabrication of a monolithic LED array with a red LED structure for a second type of full-color LED microdisplay;

[0054] Figure 9C A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the third step in the fabrication of a monolithic LED array with a red LED structure for a second type of full-color LED microdisplay;

[0055] Figure 10A A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the... Figure 8C The first monolithic LED array with a blue / green dual-wavelength LED structure shown in the figure is integrated with a driver panel for the first step of realizing a second type of full-color LED microdisplay;

[0056] Figure 10B A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the... Figure 8C The first monolithic LED array with a blue / green dual-wavelength LED structure shown in the figure is integrated with a driver panel for the second step of realizing a second type of full-color LED microdisplay;

[0057] Figure 10C A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the... Figure 9C The second monolithic LED array with a red LED structure shown in the image is... Figure 10B The first monolithic LED array shown is integrated with the driver panel as a first step in realizing a second type of full-color LED microdisplay;

[0058] Figure 10D A cross-sectional view of an exemplary LED pixel according to certain embodiments of the present invention is shown, illustrating the... Figure 9C The second monolithic LED array with a red LED structure shown in the image is... Figure 10B The first monolithic LED array shown is integrated with the driver panel in a second step to realize the second type of full-color LED microdisplay; and

[0059] Figure 11 A top view of an exemplary device of a full-color LED microdisplay according to a second embodiment of the present invention is shown. Detailed Implementation

[0060] The following detailed descriptions are merely exemplary in nature and are not intended to limit the invention or its applications and / or uses. It should be understood that numerous variations exist. These detailed descriptions will enable those skilled in the art to implement exemplary embodiments of the invention without excessive experimentation, and it should be understood that various changes or modifications can be made to the functions and structures described in the exemplary embodiments without departing from the scope of the invention as set forth in the appended claims.

[0061] Benefits, advantages, solutions to problems, and any one or more elements that may lead to or make any benefit, advantage, or solution more significant should not be construed as key, essential, or necessary features or elements of any or all claims. The invention is defined solely by the appended claims (including any modifications made during the pending period of this application and all equivalents of those claims).

[0062] In the context of describing the invention (especially in the context of the appended claims), the use of the terms “a,” “an,” “the,” and “at least one,” and similar designations, should be interpreted as encompassing both the singular and plural, unless otherwise stated herein or obviously contradicted by the context. Unless otherwise stated, the terms “comprising,” “having,” and “including,” or any other variations thereof, should be interpreted as open-ended terms (i.e., meaning “including, but not limited to,”). The use of any and all example or exemplary language (e.g., “such as”) provided herein is intended only to better illustrate the invention and not to limit its scope, unless otherwise stated. No language in the specification should be construed as indicating that any unclaimed element is essential to the implementation of the invention. Furthermore, unless explicitly stated to the contrary, “or” means inclusive “or,” not exclusive “or.” For example, condition A or B satisfies either: A is true and B is false, A is false and B is true, or both A and B are true. Approximate terms, such as “about,” “substantially,” “approximately,” and “basically,” encompass values ​​greater than or less than ten percent of the specified value.

[0063] Unless otherwise defined, all terms (including technical and scientific terms) used in the embodiments of the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0064] As used herein, “micro” refers to the descriptive size of certain devices according to certain embodiments of the invention. As used herein, the term “microdisplay” refers to the size of a display whose diagonal is less than 1 inch. However, it should be understood that embodiments of the invention are not necessarily so limited, and certain aspects of the embodiments can be applied to larger size scales.

[0065] As used herein, the term "monolithic" refers to a characteristic of the manufacturing process that forms an LED array. A "monolithic LED array" means that all LEDs in an LED array are formed on a substrate using the same manufacturing process.

[0066] As used herein, the term "above" describes the relative vertical position of layers or regions to each other, encompassing both top and bottom orientations depending on the spatial orientation of the microdisplay device. Generally, the first layer above the second layer refers to the layer that is further away from the substrate in the vertical direction.

[0067] As used herein, the term "primary color" refers to each of the colors present in a pixel. Generally, primary colors are defined as three color components: red (R), green (G), and blue (B). Pixels are repeated across a microdisplay to form a device with a desired matrix resolution; a microdisplay is essentially composed of pixels. Each pixel contains an LED used to emit the primary color.

[0068] As used herein, the term "dual wavelength" refers to an LED spectrum with two emission peaks at two distinct emission wavelengths. The term "emission peak" refers to a local maximum emission intensity at an emission wavelength that is at least twice that at a neighboring or adjacent emission wavelength.

[0069] In this invention, InGaN blue / green dual-wavelength LEDs and AlGaInP red LEDs are employed and integrated. Both LED pixel arrays are monolithically fabricated on their original substrates and then integrated together via flip-chip bonding. Using blue and green CFs on the dual-wavelength LEDs and red LEDs, the panel has proven to be an improved full-color LED microdisplay with high brightness and better brightness performance.

[0070] Figure 1 A schematic cross-sectional view of a blue / green dual-wavelength LED epitaxial wafer 100 for fabricating LED microdisplays is shown. The epitaxial wafer 100 sequentially includes a buffer layer 102, an n-(In)GaN layer 103, multiple quantum well (MQW) active regions 104, an electron blocking layer (EBL) 105, and a p-(In)GaN layer 106, all of which are grown or deposited on a substrate layer 101. In some embodiments, the aforementioned semiconductor layers of the epitaxial wafer 100 can be epitaxially grown or deposited on the substrate layer 101 using growth methods including, but not limited to, metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), ultra-high vacuum rapid thermal chemical vapor deposition, thermal pulsed laser deposition, pulsed electron deposition, and hydrothermal methods.

[0071] In some embodiments, the substrate 101 comprises gallium nitride (GaN), sapphire, silicon carbide, or silicon. In some embodiments, the substrate has a thickness between 10 μm and 100 mm.

[0072] In some embodiments, the buffer layer 102 includes one or more Al x Ga 1-x N layers, where x is any value between 0 and 1 (inclusive of non-integers). When x equals 0, buffer layer 102 comprises GaN. When x equals 1, buffer layer 102 comprises AlN. In some embodiments, the thickness of buffer layer 102 is between 10 nm and 100 μm.

[0073] In some embodiments, the n-(In)GaN layer 103 contains one or more In... x Ga 1-x N layers, where x is any value between 0 and 0.3. In x Ga 1-x The N-layer can be Si-doped or not. The Si doping concentration in the n-(In)GaN layer 103 is between 0 and 1 × 10⁻⁶.20 cm -3 between.

[0074] In some embodiments, EBL 105 comprises one or more Mg-doped Al atoms. x Ga 1-x N and In y Ga 1-y N layers, where x is any value between 0.01 and 0.3 and y is any value between 0 and 0.3. The Mg doping concentration in EBL 105 is 1 × 10⁻⁶. 17 cm -3 and 1×10 20 cm -3 between.

[0075] In some embodiments, the p-(In)GaN layer 106 comprises one or more Mg-doped In layers. x Ga 1-x N layers, where x is any value between 0 and 0.1. The Mg doping concentration in the p-(In)GaN layer 106 is 1 × 10⁶. 17 cm -3 and 1×10 20 cm -3 between.

[0076] The active region 104 of the MQWs includes a first quantum well stack 107, a second quantum well stack 108, a third quantum well stack 109, and a quantum barrier layer 1041 disposed on top of the quantum well stacks. The first quantum well stack 107 and the third quantum well stack 109 emit a first primary color, and the second quantum well stack 108 emits a second primary color. In the illustrated embodiment, the first quantum well stack 107 includes one or more blue emitting quantum wells (QWs) 1042 and one or more quantum barrier layers 1041. The second quantum well stack 108 includes one or more green emitting QWs 1043, and each QW is spaced apart by a quantum barrier layer 1041. The third quantum well stack 109 includes one or more blue emitting QWs 1042, and each QW is spaced apart by a quantum barrier layer 1041. In some embodiments, the first primary color is blue, and the second primary color is green. Each blue emitting QW 1042 is sandwiched between two quantum barrier layers 1041. Each green luminescent QW 1043 is also sandwiched between two quantum barrier layers 1041. It will be apparent to those skilled in the art that the first and second primary colors can be adjusted or interchanged without departing from the scope and spirit of the invention.

[0077] In some embodiments, the quantum barrier layer 1041 is GaN with a thickness between 5 nm and 30 nm. The quantum barrier layer 1041 may or may not be Si-doped. The Si doping concentration in the quantum barrier layer 1041 is between 0 and 1 × 10⁻⁶. 18 cm -3 between.

[0078] In some embodiments, the blue emitting QW 1042 includes In x Ga 1-x N layers, where x is any value between 0.1 and 0.2. The blue-emitting QW 1042 has a first thickness between 1 nm and 10 nm.

[0079] In some embodiments, the green luminescent QW 1043 includes In y Ga 1-y N layers, where y is any value between 0.2 and 0.3. The green-emitting QW 1043 has a second thickness between 1 nm and 5 nm.

[0080] Figure 2A A schematic cross-sectional view of an exemplary blue / green dual-wavelength LED epitaxial wafer for a full-color LED microdisplay is shown. In some embodiments, the epitaxial wafer 200 is grown from a sapphire substrate 201 via MOCVD. An undoped GaN layer 202 is grown as a buffer layer. An n-(In)GaN layer 203 comprises a Si-doped n-GaN layer 2031 and an InGaN shallow well 2032. The InGaN shallow well 2032 comprises ten 1nm / 9nm In... 0.05 Ga 0.95An N / Si-doped n-GaN layer. An InGaN shallow well 2032 can compensate for strain in the epitaxial wafer 200. A dual-wavelength MQW active region 204 is provided above the n-(In)GaN layer 203. The dual-wavelength MQW active region 204 includes a first quantum well stack 207, a second quantum well stack 208, a third quantum well stack 209, and a quantum barrier 2041 disposed on top of the quantum well stacks. Each of the first quantum well stack 207, the second quantum well stack 208, and the third quantum well stack 209 generates light in response to injected charge carriers. The first quantum well stack 207 and the third quantum well stack 209 are configured to generate light of a first primary color, and the second quantum well stack 208 is configured to generate light of a second primary color. The first quantum well stack 207 includes three blue emitting QWs 2042, and each blue emitting QW 2042 is spaced apart by the quantum barrier 2041. The second quantum well stack 208 includes a quantum barrier 2041 and a green light-emitting QW 2043. The third quantum well stack 209 includes a quantum barrier 2041 and a blue light-emitting QW 2042. Each blue light-emitting QW 2042 and each green light-emitting QW 2043 is sandwiched between the two quantum barrier layers 2041. In some embodiments, color filters (CFs) are coated and patterned on the epitaxial wafer 200. When the epitaxial wafer 200 is used to generate blue light, a blue CF is coated. When the epitaxial wafer 200 is used to generate green light, a green CF is coated.

[0081] In one example, quantum barrier 2041 is a Si-doped n-GaN with a thickness of 16 nm.

[0082] In one example, the blue emitting QW 2042 is an In electron wafer with a thickness of 2.5 nm. 0.15 Ga 0.85 N. Green luminescent QW 2043 is an In film with a thickness of 2.5 nm. 0.25 Ga 0.75 N.

[0083] In one example, the EBL 205 contains five 5nm / 5nm Al chips. 0.1 Ga 0.9 N / In 0.05 Ga 0.95 N-layer. EBL 205 is Mg-doped.

[0084] In one example, the p-(In)GaN layer 206 comprises a Mg-doped p-GaN layer and a Mg-doped p-In layer stacked on top of the Mg-doped p-GaN layer. 0.02 Ga 0.98 The N-layer is used to reduce contact resistance when manufacturing the epitaxial wafer 200 as an LED microdisplay.

[0085] Figure 2B It shows a combination of blue / green dual wavelengths Figure 2A The LED epitaxial wafer 200 is manufactured with a diameter of 0.08mm. 2 Electroluminescence spectrum of LED chips with active area. LED chips are available in 10mA, 20mA, 50mA, and 100mA ranges (corresponding to 12.5 A / cm²). 2 25A / cm 2 62.5A / cm 2 and 125A / cm 2 The LED is driven by a driving current (current density). As shown in the electroluminescence spectrum, the light emitted from the LED chip has two emission peaks at approximately 455 nm and 535 nm, respectively. The first emission peak, with a wavelength range from 420 nm to 500 nm, is a blue emission peak, and the second emission peak, with a wavelength range from 500 nm to 600 nm, is a green emission peak. The blue and green emission peaks are comparable, meaning that the power intensity ratio of the blue / green emission peaks is in the range of 0.2 to 5. Comparable power intensities of the blue and green emission peaks are beneficial to the brightness and color gamut of the LED microdisplay. It will be apparent to those skilled in the art that the power intensity ratio of the blue / green emission peaks may not be limited to the range of 0.2 and 5 without departing from the scope and spirit of the invention.

[0086] Figure 3A A schematic cross-sectional view of an exemplary red LED epitaxial wafer for a full-color LED microdisplay is shown. Any type of AlGaInP LED material can be used for red light emission. In some embodiments, the epitaxial wafer 300 is grown from a gallium arsenide (GaAs) substrate 301 via MOCVD. Optionally, an AlGaInP etch stop layer 302 is grown on the GaAs substrate 301. Optionally, the n-side layer 303 includes a Si-doped n-GaAs layer 3031, a Si-doped n-AlGaInP layer 3032, and a Si-doped n-AlInP layer 3033. A red emitting MQWs active region 304 is disposed above the n-side layer 303 and is configured to generate red light. The red emitting MQWs active region 304 contains one or more red emitting AlGaInP QWs (not shown) sandwiched between two AlGaInP quantum barrier layers (not shown). The QW and quantum barrier layer have different Al and Ga compositions. In some embodiments, the third primary color is red. The p-side layer 305 comprises a zinc (Zn) or Mg-doped p-AlInP layer 3051 and a Zn or Mg-doped p-GaP layer 3052. The red emitting MQW active region 304 is sandwiched between the n-side layer 303 and the p-side layer 305.

[0087] Figure 3B It shows the result of Figure 3A AlGaInP red LED epitaxial wafers 300 fabricated with a thickness of 0.08mm 2 Electroluminescence spectrum of an active-area LED chip. The LED chip is powered by 20 mA (corresponding to 25 A / cm²). 2 The LED is driven by a driving current (current density). As shown in the electroluminescence spectrum, the light emitted from the LED chip has an emission peak at approximately 625 nm. The emission peak is in the wavelength range of 560 nm to 660 nm, which represents the red emission peak.

[0088] Based on the above description, the LED microdisplay includes a dual-wavelength LED for emitting light having a first primary color and a second primary color, and a monochromatic LED for emitting red light. In one embodiment, the dual-wavelength LED is a... Figure 2A InGaN blue / green dual-wavelength LEDs with a specific structure; and the red LED is an InGaN LED with... Figure 3A The structure of the AlGaInP red LED is described. Specifically, the dual-wavelength LED and the red LED have different substrates and different multilayer semiconductor structures. The dual-wavelength LED and the red LED are integrated together via flip-chip bonding, enabling the heterogeneous integration of the sapphire substrate 201 and the GaAs substrate 301 in the LED microdisplay.

[0089] Figures 4A to 4C A cross-sectional view of an exemplary LED pixel according to a first embodiment of the present invention is shown, illustrating the manufacturing steps of a first monolithic LED array having a blue / green dual-wavelength LED structure for a full-color LED microdisplay.

[0090] Figure 4A The first manufacturing step of a first monolithic LED array with a blue / green dual-wavelength LED structure is shown. A blue / green dual-wavelength LED epitaxial wafer 400 is used for manufacturing, and in some embodiments, the structure of the epitaxial wafer 400 is similar to... Figure 2AThe epitaxial wafer 200 is identical. Two LEDs 407 and 408, and a multilayer structure 409 are formed on the substrate 401 of the epitaxial wafer 400. In some embodiments, the substrate 401 is a GaN substrate, a sapphire substrate, a silicon carbide substrate, or a silicon substrate. More preferably, the substrate 401 is a sapphire substrate. The first LED 407 and the second LED 408 have the same structure, sequentially including a buffer layer 402a, a first n-doped semiconductor layer 403a, a dual-wavelength MQWs (D-MQWs) active region 404, an EBL 405, and a p-doped semiconductor layer 406. In some embodiments, the first n-doped semiconductor layer 403a is an n-(In)GaN layer, and the p-doped semiconductor layer 406 is a p-(In)GaN layer. The multilayer structure 409 is designed for bonding a third LED having a red LED structure and may include a buffer layer 402b and a second n-doped semiconductor layer 403b. In some embodiments, the second n-doped semiconductor layer 403b is an n-(In)GaN layer. Optionally, an epitaxial layer is provided in the multilayer structure 409 to compensate for the height difference. When the second monolithic LED array is flip-chip bonded to the first monolithic LED array, the multilayer structure 409 is provided to accommodate the third LED 506. Figures 5A to 5C The third LED 506 is then connected to the first monolithic LED array. In some embodiments, all or part of the multilayer structure 409 may be etched away. To fabricate the first LED 407, the second LED 408, and the multilayer structure 409, isolation trenches are etched between them by removing a portion of all epitaxial layers above the substrate 401. The first LED 407, the second LED 408, and the multilayer structure 409 are then etched to further expose the first n-doped semiconductor layer 403a and the second n-doped semiconductor layer 403b. The etching mask may be a photoresist, silicon dioxide (SiO2), or silicon nitride (Si3N4). The etching method may be dry etching (e.g., inductively coupled plasma etching), wet etching, or a combination of dry and wet etching. A photolithography process may be included to facilitate the etching process. The photolithography process may include photoresist coating, soft baking, mask alignment, exposure, post-exposure baking, photoresist development, rinsing, drying, other suitable processes, or any combination thereof.

[0091] Figure 4B The second fabrication step of a first monolithic LED array with a blue / green dual-wavelength LED structure is illustrated. Optionally, a current spreading layer (CSL) 410 is deposited and patterned on the first LED 407 and the second LED 408, respectively. In some embodiments, the CSL 410 may be an indium tin oxide (ITO) or Ni / Au metal stack.

[0092] On CSL 410, n-metal layers 411a and 411b are deposited and patterned for the first LED 407 and the second LED 408, respectively. The n-metal layer 411a in the first LED 407 and the second LED 408 is an n-electrode deposited on a first n-doped semiconductor layer 403a. The n-metal layer 411b in the multilayer structure 409 is a bonding pad. In some embodiments, the n-metal layers 411a and 411b may be a metal stack comprising one or more metals (such as titanium (Ti), chromium (Cr), aluminum (Al), copper (Cu), nickel (Ni), platinum (Pt), or gold (Au)). After the n-metal deposition of the n-metal layers 411a and 411b, a passivation layer 412 is coated and patterned. The passivation layer 412 has openings for p-electrodes on top of the first LED 407 and the second LED 408, and also has openings in the multilayer structure 409 to expose the n-metal layer 411b. An opening (not shown) is also formed in the passivation layer 412 to expose the n-metal layer (see [link]). Figure 6C 411c) is used to bond the red LED. In some embodiments, the passivation layer 412 may be SiO2, Si3N4, alumina (Al2O3), hard-baked photoresist, organic polymer, or any combination thereof.

[0093] p-metal layers 413a and 413b are deposited and subsequently patterned. In the first LED 407 and the second LED 408, p-metal layer 413a serves as a p-electrode, and in the multilayer structure 409, p-metal layer 413b forms a p-side connection to the n-metal layer 411b (bonding pad). The p-metal layers 413a and 413b can be metal stacks comprising one or more metals (such as Ti, Cr, Al, Cu, Ni, Pt, or Au).

[0094] CSL 410, n-metal layers 411a, 411b, and p-metal layers 413a, 413b can be deposited by evaporation or sputtering. The n-metal layers 411a, 411b, and p-metal layers 413a, 413b can be patterned by a stripping process using photoresist or by etching using a mask. CSL 410, n-metal layers 411a, 411b, and p-metal layers 413a, 413b can be annealed for 0.5 to 10 minutes at a temperature between 400°C and 800°C after the patterning process. The passivation layer 412 can be coated using chemical vapor deposition (CVD) for inorganic dielectrics and by spin coating or spraying for organic materials. The passivation layer 412 can be patterned using etching or photolithography using a mask.

[0095] Figure 4CThe third manufacturing step of a first monolithic LED array with a blue / green dual-wavelength LED structure is shown. Blue CF 414 is coated on top of the first LED 407 and hard-baked. Blue CF 414 allows blue light to pass through and absorbs other components of visible light. Similarly, green CF 415 is coated on top of the second LED 408 and hard-baked. Green CF 415 allows green light to pass through and absorbs other components of visible light. The coating methods for blue CF 414 and green CF 415 can be performed by spin coating or spray coating. Figures 4A to 4C The fabrication process of the first monolithic LED array with a blue / green dual-wavelength LED structure shown is completed after the CF coating step. The first LED 407 becomes a blue LED pixel, and the second LED 408 becomes a green LED pixel.

[0096] Figures 5A to 5C A cross-sectional view of an exemplary LED pixel according to a first embodiment of the present invention is shown, illustrating the manufacturing steps of a second monolithic array with a red LED structure for a full-color LED microdisplay.

[0097] Figure 5A The first manufacturing step of a second monolithic LED array with a red LED structure is shown. A red LED epitaxial wafer 500 is used for manufacturing, and in some embodiments, the structure of the epitaxial wafer 500 is similar to... Figure 3A The epitaxial wafer 300 is identical to the epitaxial wafer 500. A third LED 506 and a window region 507 are formed on the GaAs substrate 501 of the epitaxial wafer 500. The third LED 506 includes a red LED structure for emitting red light. Optionally, the third LED 506 includes an etch stop layer (ESL) 502, an n-side layer 503, a red emitting MQWs (R-MQWs) active region 504, and a p-side layer 505. The window region 507 is set to be transparent to accommodate the first LED 407 and the second LED 408. Because the epitaxial layers of the third LED 506 absorb light, all epitaxial layers grown on the GaAs substrate 501 in the window region 507 are removed. In some embodiments, the third LED 506 is etched first to expose the n-side layer 503, and then the window region 507 is etched. The etching mask may be a photoresist, SiO2, or Si3N4. The etching method may be dry etching, wet etching, or a combination of dry and wet etching. The process may include a photolithography process to assist the etching process. The photolithography process may include photoresist coating, soft baking, mask alignment, exposure, post-exposure baking, photoresist development, rinsing, drying, other suitable processes, or any combination thereof.

[0098] Figure 5BThe second manufacturing step of a second monolithic LED array with a red LED structure is shown. A p-metal layer 508 is deposited and patterned on a third LED 506 as a p-electrode. The p-metal layer 508 may be a metal stack comprising one or more metals (such as Zn, beryllium (Be), Ni, Pt, or Au). An n-metal layer 509 is deposited and patterned on the third LED 506 as an n-electrode. The LED array has a common n-electrode structure, such that all n-metal layers are electrically connected. The n-metal layer 509 may be a metal stack comprising one or more metals (such as germanium (Ge), Ni, Pt, Ti, or Au). After the n-metal deposition of the n-metal layer 509, a passivation layer 510 is coated and patterned. The passivation layer 510 has an opening on the top of the third LED 506 for depositing p-metal bumps 511 (see [link to documentation]). Figure 5C An opening (not shown) is also formed in the passivation layer 510 to expose the n-metal layer 509 for the n-metal bump (not shown). The passivation layer 510 may be SiO2, Si3N4, Al2O3, hard-baked photoresist, organic polymer, or any combination thereof.

[0099] The p-metal layer 508 and n-metal layer 509 can be deposited by evaporation or sputtering. The p-metal layer 508 and n-metal layer 509 can be patterned by a stripping process using photoresist or by etching using a mask. The p-metal layer 508 and n-metal layer 509 can be annealed for 0.5 to 10 minutes at a temperature between 300°C and 600°C after the patterning process. For inorganic dielectrics, the passivation layer deposition method can be performed by CVD, and for organic materials, it can be performed by spin coating or spraying. The passivation layer patterning method can be performed by etching or photolithography using a mask.

[0100] Figure 5C The third fabrication step of a second monolithic LED array with a red LED structure is illustrated. P-metal bumps 511 and n-metal bumps (not shown) are deposited and patterned on the third LED 506 as bonding metals for subsequent bonding processes. The p-metal bumps 511 are deposited on top of the p-metal layer 508, and the n-metal bumps are deposited on top of the n-metal layer 509 through etched openings (not shown) in the passivation layer 510. The p-metal bumps 511 and n-metal bumps may comprise one or more layers of metal, such as Au, a gold-tin (Au-Sn) alloy, a copper-tin (Cu-Sn) alloy, or a gold-indium (Au-In) alloy. The thickness of the p-metal bumps 511 and n-metal bumps can range from 1 μm to 20 μm. Figures 5A to 5CThe fabrication process of the second monolithic LED array with a red LED structure shown is completed after the bump deposition step. In some embodiments, the area of ​​the patterned p-metal bumps 511 and n-metal bumps can be larger than the openings in the passivation layer 510, and they are then reformed by a reflow process at a temperature above 170°C. During the reflow process, all metal outside the openings flows into the openings to form metal bumps. By controlling the area ratio of the metal pattern to the openings, metal bumps of different heights can be easily obtained. In some embodiments, the height of the n-metal bump 509 can be greater than the height of the p-metal bump 511 to compensate for any height difference. The p-metal bumps 511 and n-metal bumps 509 can be deposited by evaporation or sputtering. The p-metal bumps 511 and n-metal bumps can be patterned by a stripping process using photoresist or by etching using a mask.

[0101] Figures 6A to 6B This is a cross-sectional view of the LED pixels, illustrating the heterogeneous integration process of a second monolithic LED array with a red LED structure and a first monolithic LED array with a blue / green dual-wavelength LED structure. The cross-sectional structure only shows a partial representation of the entire full-color LED microdisplay. According to a first embodiment of the invention, the second monolithic LED array provides red LED pixels for the full-color LED microdisplay, and the first monolithic LED array provides blue and green LED pixels for the full-color LED microdisplay.

[0102] Figure 6A It shows Figure 5C The second monolithic LED array and Figure 4C The first step in the heterogeneous integration of the first monolithic LED array is as follows: A full-color pixel 600 is formed by bonding a second monolithic LED array to the first monolithic LED array via p-metal bumps 511 and n-metal bumps (not shown). Blue LED 601, green LED 602, and red LED 603 are provided in the full-color pixel 600. The p-metal bumps 511 are electrically connected to the p-metal layer 413b of the first monolithic LED array via n-metal layers 411b and 508 at the second monolithic LED array. Alternatively, the n-metal bumps are electrically connected to n-metal layers 411a and 509 of the first monolithic LED array. Optionally, an underfill layer 604 fills the gap between the first and second monolithic LED arrays. The underfill layer 604 may be an organic polymer.

[0103] The method for bonding the second monolithic LED array to the red LED structure can be flip-chip bonding. In some embodiments, the bonding temperature is between 150°C and 300°C, and the bonding time can be between 0.5 minutes and 10 minutes. The underfill layer 604 can be applied to the first and second monolithic LED arrays before performing the flip-chip bonding process and cured during or after the bonding process.

[0104] Figure 6B It shows Figure 5C The second monolithic LED array and Figure 4C The second step in the heterogeneous integration of the first monolithic LED array involves removing the GaAs substrate 501, which can be performed by dry etching, wet etching, or a combination of both. In some embodiments, the GaAs substrate 501 is removed using a mixture of an aqueous ammonia solution and a H2O2 solution. The substrate removal process stops at the surface of the passivation layer 510 and, optionally, at the surface of the ESL 502, which is provided to improve etch selectivity. The process is complete after etching. Figures 6A to 6B The integration process shown in the figure is used to fabricate a full-color LED microdisplay according to a first embodiment of the present invention. The full-color LED microdisplay is characterized in that the microdisplay panel is located on a substrate 401 of a first monolithic LED array having a blue / green dual-wavelength LED structure, and requires a single flip-chip bonding process. Blue LED 601 and green LED 602 ​​each have a dual-wavelength MQWs active region 404 of a first material, while red LED 603 has a red-emitting MQWs active region 504. The dual-wavelength MQWs active region 404 comprises InGaN material, and the red-emitting MQWs active region 504 comprises AlGaInP material. Due to the presence of blue CF 414 and green CF 415, blue LED 601 emits blue light, green LED 602 ​​emits green light, and red LED 603 emits red light. Light from blue LED 601 and green LED 602 ​​can pass through a transparent window region 507.

[0105] The full-color LED microdisplay obtained by flip-chip bonding of the first and second monolithic LED arrays is characterized in that the dual-wavelength MQWs active region 204 of the blue / green dual-wavelength LED structure is positioned at a lower vertical position closer to the substrate 401, and the red emitting MQWs active region 304 of the red LED structure is positioned at a higher vertical position. Specifically, the red LED structure of the third LED 409 is vertically above the blue / green dual-wavelength LED structures of the first LED 407 and the second LED 408. The dual-wavelength MQWs active region 204 and the red emitting MQWs active region 304 are formed on two different vertically non-overlapping epitaxial layers.

[0106] As discussed above, the blue / green dual-wavelength LED structure comprises an n-doped semiconductor layer 403a and a p-doped semiconductor layer 406, and the red LED structure comprises an n-side layer 503 and a p-side layer 505. When the first monolithic LED array is flip-chip bonded to the second monolithic LED array, the full-color LED microdisplay will have epitaxial layers arranged vertically in the following order (from top to bottom): n-side layer 503, red emitting MQWs active region 504, p-side layer 505, p-doped semiconductor layer 406, dual-wavelength MQWs active region 404, n-doped semiconductor layer 403a, and substrate 401. In other words, the dual-wavelength MQWs active region 404 is sandwiched between the n-doped semiconductor layer 403a and the p-doped semiconductor layer 406. Specifically, the p-doped semiconductor layer 406 is positioned above the dual-wavelength MQWs active region 404 and the n-doped semiconductor layer 403a. The red luminescent MQWs active region 504 is sandwiched between the n-side layer 503 and the p-side layer 505, wherein the n-side layer 503 is positioned above the red luminescent MQWs active region 504 and the p-side layer 505.

[0107] Since the full-color LED microdisplay is formed by a matrix of multiple pixels arranged in rows and columns, and each pixel has the same arrangement of stacked semiconductor layers on substrate 401, a first LED 407 and a second LED 408 with blue / green dual-wavelength LED structures, and a third LED 409 with red LED structures, the full-color LED microdisplay of the present invention has the advantages of high contrast and better brightness performance, with emission peaks at approximately 455nm, 535nm and 625nm.

[0108] Figure 6C Another cross-sectional view of the full-color LED microdisplay is shown. Electrical connections for the n-metal bump 512 are illustrated here. The structure of the first monolithic LED array with a blue / green dual-wavelength LED structure for bonding the n-metal bump 512 includes a buffer layer 402c, a third n-doped semiconductor layer 403c, and an n-metal layer 411c. In some embodiments, the third n-doped semiconductor layer 403c is an n-(In)GaN layer. As described above, this structure of the n-metal bump 512 is similar to the bonding structure of the p-metal bump 511, and the n-metal bump 512 is formed together with the p-metal bump 511 in the same manufacturing process. The n-metal bump 512 electrically connects the n-metal layer 411c at the first monolithic LED array and the n-metal layer 509 at the second monolithic LED array.

[0109] Figure 7This is a top view of an exemplary device of a full-color LED microdisplay according to a first embodiment of the present invention. The microdisplay panel 700 includes a plurality of pixels 600. Each pixel 600 includes a blue LED 601, a green LED 602, and a red LED 603. The blue LED 601 and green LED 602 ​​are formed on a first semiconductor structure having a substrate 401, while the red LED 603 is formed on a second semiconductor structure having a GaAs substrate 501, the second semiconductor structure being flip-chip bonded to the first semiconductor structure. In some embodiments, the first semiconductor structure is a first monolithic LED array having a blue / green dual-wavelength LED structure, and the second semiconductor structure is a second monolithic LED array having a red LED structure. The upper ends of the blue LED 601 and green LED 602 ​​are passivation layers 510 of the second semiconductor structure, and the upper ends of the red LED 603 are ESL 502 or other epitaxial layers of the red LED 603. The arrangement of the LEDs in the full-color pixel 600 can have other configurations, such as a Bayer pattern or a pentile matrix, without departing from the scope and spirit of the invention. The dashed line shows the cross-section along axis A-A'. Figure 6B ) and the cross section along axis B-B' ( Figure 6C The position of ).

[0110] The full-color LED microdisplay panel 700 disclosed above features passive matrix (PM) driving. The n-metal layer 411a sends data driving signals (source signals) to the blue LEDs 601 and green LEDs 602 in each column. The n-metal layer 411c ( Figure 6C The p-metal layer 413a and n-metal layer 509 send data drive signals (source signals) to the red LED 603 via n-metal bumps 512 in each column. The p-metal layer 413a sends scan drive signals (gate signals) to the LED pixels in each row. The p-metal layer 413b ( Figure 6B The n-metal lines are connected to the p-metal layer 413a in the same row. The red LED 603 is connected to the p-metal layers 413a and 413b via metal bumps 511 and other associated pads. The n-metal lines and p-metal lines form the PM driver circuit. Data drive signals and scan drive signals can be provided by application-specific integrated circuits (ASICs), microcontroller units (MCUs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), gate-in-panel (GIP) circuits, programmable I / O devices, other semiconductor devices, or any combination thereof.

[0111] Figures 8A to 8C A cross-sectional view of an exemplary LED pixel according to a second embodiment of the present invention is shown, illustrating the manufacturing steps of a first monolithic LED array with a blue / green dual-wavelength LED structure for a full-color LED microdisplay.

[0112] Figure 8A The first manufacturing step of a first monolithic LED array with a blue / green dual-wavelength LED structure is shown. A blue / green dual-wavelength LED epitaxial wafer 800 is used for the fabrication of the LED array, and in some embodiments, the structure of the epitaxial wafer 800 is similar to... Figure 2A The epitaxial wafer 200 is identical. Two LEDs 807 and 809, and a window region 808 are formed on the substrate 801 of the epitaxial wafer 800. The window region 808 is used to bond the red LED 808, and an n-bonding region 807b is located near the first LED 807 used for n-bonding (discussed below). The first LED 807 and the second LED 809 each include (in a stacked sequence) a buffer layer 802, a first n-doped semiconductor material 803a, a second n-doped semiconductor material 803b, a dual-wavelength MQWs active region 804, an EBL 805, and a p-doped semiconductor layer 806. In some embodiments, the first n-doped semiconductor layer 803a and the second n-doped semiconductor layer 803b are n-(In)GaN layers, and the p-doped semiconductor layer 806 is a p-(In)GaN layer. The mesa of the first LED 807 and the second LED 809 may be identical. Window region 808 includes a buffer layer 802. Window region 808, first LED 807, and second LED 809 are formed by etching. In window region 808, all epitaxial layers on substrate 801 are removed except for buffer layer 802. In n-bonding region 807b, all epitaxial layers on substrate 801 are removed except for buffer layer 802 and a portion of second n-doped semiconductor layer 803b. Buffer layer 802 can be completely or partially etched. The remaining buffer layer 802 can protect the LED array during substrate removal. First LED 807 and second LED 809 are etched to expose first n-doped semiconductor layer 803a and second n-doped semiconductor layer 803b. The etching mask can be a photoresist, SiO2, or Si3N4. The etching method can be dry etching, wet etching, or a combination of dry and wet etching.

[0113] Figure 8B The second fabrication step of the first monolithic LED array with a blue / green dual-wavelength LED structure is shown. Optionally, CSL810 is deposited and patterned on two LEDs 807 and 809. CSL 810 can be an ITO or Ni / Au metal stack.

[0114] On CSL 810, n-metal layers 811a and 811b are deposited and patterned for the first LED 807 and the second LED 809, respectively. The n-metal layer 811a in the first LED 807 and the second LED 809 is an n-electrode on a first n-doped semiconductor layer 803a. The n-metal layer 811b is a pad in an n-bonding region 807b. The LED array has a common n-electrode structure, such that the n-metal layers 811a and 811b are electrically connected. A p-metal layer 813 is deposited and patterned on CSL 810. In some embodiments, the n-metal layers 811a, 811b and p-metal layer 813 may be a metal stack comprising one or more metals (such as Ti, Cr, Al, Cu, Ni, Pt, Au). A passivation layer 812 is deposited and patterned after the metal deposition. The passivation layer 812 has openings on the p-metal layer 813 of the first LED 807 and the second LED 809, on the exposed area of ​​the buffer layer 802, and on the n-metal layer 811b. These openings are left for metal bump formation and pixel bonding. In some embodiments, the passivation layer may be SiO2, Si3N4, Al2O3, hard-baked photoresist, organic polymer, or any combination thereof.

[0115] CSL 810, n-metal layer 811a, and p-metal layer 813 can be deposited by evaporation or sputtering. The n-metal layer 811a and p-metal layer 813 can be patterned by a stripping process using photoresist or by etching using a mask. After patterning, CSL 810 and the metal can be annealed at a temperature between 400°C and 800°C for 0.5 to 10 minutes. For inorganic dielectrics, the passivation layer deposition method can be performed by CVD, and for organic materials, by spin coating or spraying. The patterning method for the passivation layer 812 can be performed by etching or photolithography using a mask.

[0116] Figure 8C The third manufacturing step of a first monolithic LED array with a blue / green dual-wavelength LED structure is illustrated. P-metal bumps 814 and n-metal bumps 815 are deposited and patterned on the first LED 807 and the second LED 809 as bonding metals for subsequent bonding processes. The p-metal bumps 814 are on top of the p-metal layer 813, and the n-metal bumps 815 are connected to the top of the n-metal layer 811b through openings in the passivation layer 812. The p-metal bumps 814 and n-metal bumps 815 may comprise one or more layers of metal, such as Au, Au-Sn alloy, Cu-Sn alloy, or Au-In alloy. The thickness of the p-metal bumps 814 and n-metal bumps 815 can be between 1 μm and 10 μm. Figures 8A to 8CThe fabrication process of the first monolithic LED array with a blue / green dual-wavelength LED structure shown is completed after the bump deposition step. In some embodiments, the heights of the p-metal bumps 814 and n-metal bumps 815 can be controlled by adjusting the area ratio of the metal pattern and the opening, as well as by a reflow process, both of which are explained in the description above. In some embodiments, the height of the n-metal bumps 815 can be greater than the height of the p-metal bumps 814 to compensate for the height difference.

[0117] Figures 9A to 9C A cross-sectional view of an exemplary LED pixel according to a second embodiment of the present invention is shown, illustrating the manufacturing steps of a second monolithic LED array with a red LED structure for a full-color LED microdisplay.

[0118] Figure 9A The first manufacturing step of a second monolithic LED array with a red LED structure is shown. A red LED epitaxial wafer 900 is used in the fabrication of the LED array, and in some embodiments, the structure of the epitaxial wafer 900 is similar to... Figure 3A The epitaxial wafer 300 shown is identical. A red LED 906 and window regions 907a and 907b are formed on the GaAs substrate 901 of the epitaxial wafer 900. The red LED 906 includes an n-side layer 903a, a red emitting MQWs active region 904, a p-side layer 905, and an optional ESL 902a. Window regions 907a and 907b are set to be transparent to accommodate a first LED 807 and a second LED 809. All epitaxial layers grown on the GaAs substrate 901 in window regions 907a and 907b are removed. A structure for n-electrode connections, including ESL 902b and n-side layer 903b, is also formed. ESL 902a and 902b and n-side layers 903a and 903b can be formed in the same etching process. In some embodiments, the red LED epitaxial wafer 900 is first etched to expose the n-side layers 903a and 903b, and then the window regions 907a and 907b are etched. The etching mask may be a photoresist, SiO2, or Si3N4. The etching method may be dry etching, wet etching, or a combination of dry and wet etching.

[0119] Figure 9BThe second fabrication step of a second monolithic LED array with a red LED structure is shown. A p-metal layer 908 is deposited and patterned on the red LED 906 as a p-electrode. The p-metal layer 908 may be a metal stack comprising one or more metals (such as Zn, Be, Ni, Pt, or Au). An n-metal layer 909a, 909b is deposited and patterned on the n-side layers 903a, 903b as an n-electrode. The n-metal layer 909b also serves as a bonding pad for the n-metal bumps. The LED array has a common n-electrode structure, such that the n-metal layers 909a, 909b are electrically connected. The n-metal layers 909a, 909b may be a metal stack comprising one or more metals (such as Ge, Ni, Pt, Ti, or Au). A passivation layer 910 is deposited and patterned after the n-metal deposition of the n-metal layers 909a, 909b. The passivation layer 910 has an opening on the top of the red LED 906 for electrical connection to the p-metal bump 911 (see [link]). Figure 9C ), and has an opening on the top of the n-metal layer 909b for electrically connecting the n-metal bump 912 (see Figure 9C The passivation layer 910 can be SiO2, Si3N4, Al2O3, hard-baked photoresist, organic polymer, or any combination thereof.

[0120] The n-metal layers 909a, 909b, and p-metal layer 908 can be deposited by evaporation or sputtering. The n-metal layers 909a, 909b, and p-metal layer 908 can be patterned by a stripping process using photoresist or by etching using a mask. The n-metal layers 909a, 909b, and p-metal layer 908 can be annealed for 0.5 to 10 minutes at a temperature between 300°C and 600°C after the patterning process. The deposition method for the passivation layer 910 can be performed by CVD for inorganic dielectrics and by spin coating or spraying for organic materials. The patterning method for the passivation layer 910 can be performed by etching or photolithography using a mask.

[0121] Figure 9C The third fabrication step of a second monolithic LED array with a red LED structure is illustrated. P-metal bumps 911 and n-metal bumps 912 are deposited and patterned on top of the red LED 906 and the n-metal layer 909b, respectively, as bonding metals for subsequent bonding processes. The p-metal bumps 911 and n-metal bumps 912 are connected to their corresponding metal electrodes through openings etched in the passivation layer 910. The p-metal bumps 911 and n-metal bumps 912 may comprise one or more layers of metal, such as Au, Au-Sn alloy, Cu-Sn alloy, or Au-In alloy. The thickness of the p-metal bumps 911 and n-metal bumps 912 can be between 1 μm and 20 μm. Figures 9A to 9CThe fabrication process of the second monolithic LED array with a red LED structure shown is completed after the bump deposition step. In some embodiments, the heights of the p-metal bumps 911 and n-metal bumps 912 can be controlled by adjusting the area ratio of the metal pattern and the opening, as well as the reflow process, both of which are explained in the description above. In some embodiments, the height of the n-metal bumps 912 can be greater than the height of the p-metal bumps 911 to compensate for the height difference. The metal deposition method in the above steps can be evaporation or sputtering. The p-metal bumps 911 and n-metal bumps 912 can be patterned by a stripping process using photoresist or by etching using a mask.

[0122] Figures 10A to 10D This is a cross-sectional view of an LED pixel, illustrating the manufacturing process of integrating a first monolithic LED array with a blue / green dual-wavelength LED structure and a second monolithic LED array with a red LED structure on a driver panel to obtain 1000 full-color pixels. The cross-sectional structure only shows a partial representation of the entire LED array. According to a second embodiment of the invention, the second monolithic LED array provides red LED sub-pixels for the full-color LED microdisplay, and the first monolithic LED array provides blue and green LED sub-pixels for the full-color LED microdisplay.

[0123] Figure 10A Integrated Figure 8C The diagram illustrates the first step of a first monolithic LED array and driver panel 1001 with a blue / green dual-wavelength LED structure. After the first monolithic LED array is bonded to the driver panel 1001, full-color pixels 1000 are partially formed. The driver panel 1001 can be a CMOS driver chip, a thin-film transistor (TFT) driver backplane, a gate-in-panel (GIP) circuit, or other driver panels including circuitry on a panel substrate. On the driver panel 1001, there are a first pad 1002 for n-connection of the red LED array, a second pad 1003 for n-connection of the first monolithic LED array, and three sub-pixel pads 1004 for p-connection of the three LEDs 1007, 1008, and 1009. A p-metal bump 814 electrically connects a p-metal layer 813 to the pad 1004. An n-metal bump 815 electrically connects an n-metal layer 811b and the second pad 1003. A first n-bonding region 1005 is provided for the second monolithic LED array, and a second n-bonding region 1006 is provided for the first monolithic LED array. The full-color pixel 1000 includes: a first LED 1007, which includes a blue / green dual-wavelength LED structure for emitting blue light; a second LED 1009, which includes a blue / green dual-wavelength LED structure for emitting green light; and a third LED 1008, which includes a red LED structure for emitting red light. Figures 10A to 10C The three LEDs 1007, 1008, and 1009 shown are incomplete. The first monolithic LED array with a blue / green dual-wavelength LED structure can be flip-chip bonded to the driver panel 1001 at a bonding temperature between 150°C and 300°C. The bonding time can be between 0.5 minutes and 10 minutes.

[0124] Figure 10B Integrated Figure 8C The second step of the first monolithic LED array with blue / green dual-wavelength LED structure and driver panel 1001 is shown in the figure. Figure 10A The substrate 801 is removed in the second step. The substrate removal method can be dry etching, wet etching, or a combination of both. In some embodiments, the substrate 801 is silicon and is removed using an HNA (HF-nitric acid-acetic acid) etchant. The substrate removal process stops at the surface of the remaining buffer layer 802. The buffer layer 802 is then removed by dry etching. Blue CF 1010 is coated on top of the first LED 1007, and green CF 1011 is also coated on top of the second LED 1009. The CF layer can be coated by spin coating or spray coating. Blue CF 1010 and green CF 1011 are hard baked.

[0125] Figure 10C It shows that Figure 9C The first step shown is the integration of a second monolithic LED array with a red LED structure into an integral assembly of a first monolithic LED array and a driver panel. The red LED array is bonded to the driver panel 1001 via window region 808 and n-bonding region 807b of the first monolithic LED array, which has a blue / green dual-wavelength LED structure, to form a full-color pixel 1000. A p-metal bump 911 electrically connects the p-metal layer 908 and the pixel pad 1004. An n-metal bump 912 electrically connects the n-metal layer 909b and the first pad 1002. Optionally, an underfill layer 1012 fills the gap between the dual-wavelength LED array and the red LED array. The underfill layer 1012 can be an organic polymer. The red LED array can be flip-chip bonded to it at a bonding temperature between 150°C and 300°C. The bonding time can be between 0.5 minutes and 10 minutes. The underfill material can be applied before the bonding process and cured during or after the bonding process.

[0126] Figure 10D It shows that Figure 9C The second step, shown in the diagram, involves integrating the second monolithic LED array with a red LED structure into an integrated body of the first monolithic LED array and the driver panel. In this second step, the... Figure 10CThe GaAs substrate 901 is shown in the image. The substrate can be removed using dry etching, wet etching, or a combination of both. In some embodiments, the GaAs substrate 901 is removed using a mixture of ammonia solution and H2O2 solution. The substrate removal process stops at the surface of the passivation layer 910, and optionally at the surface of the etch stop layers 902a and 902b. The etch stop layers 902a and 902b can improve etch selectivity. Figures 10A to 10D The described integration process is completed after the etching step, resulting in the full-color LED microdisplay of the second embodiment. The LED microdisplay of the second embodiment is characterized by employing an external microdisplay driver panel and performing two bonding operations. A first LED 1007 emits blue light, a second LED 1009 emits green light, and a third LED 1008 emits red light. Light from the first LED 1007 and the second LED 1009 can pass through transparent window areas 907a and 907b on the second monolithic LED array.

[0127] Figure 11 This is a top view illustrating an exemplary device of a full-color LED microdisplay according to a second embodiment of the present invention. The microdisplay panel 1100 includes a plurality of full-color pixels 1000 and a driver panel 1001. The plurality of full-color pixels 1000 are composed of a lower semiconductor structure and an upper semiconductor structure. A first LED 1007 and a second LED 1009 are formed on the lower semiconductor layer, wherein the lower semiconductor layer is a first monolithic LED array having a blue / green dual-wavelength LED structure, and are first bonded to the driver panel 1001. A third LED 1008 is formed on the upper semiconductor layer, wherein the upper semiconductor layer is a second monolithic LED array having a red LED structure, and is subsequently bonded. Light from the first LED 1007 and the second LED 1009 passes through a passivation layer 910 of the upper semiconductor layer, and the surface of the third LED 1008 is an etch stop layer 902a, 902b, or other epitaxial layer of the upper semiconductor layer. Without departing from the scope and spirit of the invention, the three LEDs 1007, 1008, and 1009 in the full-color pixel 1000 may have other configurations, such as a Bayer pattern or a pentile matrix. The dotted dashed lines indicate a cross-section along axis C-C'. Figure 10D The dashed line indicates the location of the first n-doped semiconductor layer 803a and the second n-doped semiconductor layer 803b.

[0128] Depending on the type of driver panel 1001, the full-color LED microdisplay panel disclosed above can be driven by a passive matrix (PM) or an active matrix (AM). The n-metal layers 811a and 811b at the first monolithic LED array and the n-metal layers 909a and 909b at the second monolithic LED array are both connected to a common signal via n-metal bumps 815 and 912. P-metal bumps 814 and 911 connect the p-electrodes of the three LEDs 1007, 1008, and 1009 to the driver panel 1001 and transmit drive signals from there. The three LEDs 1007, 1008, and 1009 have the same common n-electrode signal and individual p-electrode drive signals. The signals can be provided by an ASIC, MCU, PLD, FPGA, GIP circuit, programmable I / O device, other semiconductor device, or any combination of the foregoing.

[0129] The foregoing describes the basic structure of a full-color LED microdisplay with heterogeneous integration of InGaN blue / green dual-wavelength LEDs and AlGaInP red LEDs proposed in this invention. It is evident that the variations and other features and alternatives disclosed above can be integrated into other semiconductor devices. Therefore, this embodiment is to be considered illustrative rather than restrictive in all respects. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and therefore all variations within the meaning and scope of the equivalents of the claims are intended to be included within the scope of the invention.

Claims

1. A full-color light-emitting diode microdisplay, comprising multiple pixels, each pixel comprising a sub-pixel: The first light-emitting diode includes a blue / green dual-wavelength light-emitting diode structure for emitting blue light; The second light-emitting diode includes the blue / green dual-wavelength light-emitting diode structure for emitting green light; as well as The third light-emitting diode includes a red light-emitting diode structure for emitting red light. in: The blue / green dual-wavelength light-emitting diode structure further includes a dual-wavelength multi-quantum-well active region of a first material having two emission peaks, wherein the dual-wavelength multi-quantum-well active region includes a first quantum well stack, a second quantum well stack, and a third quantum well stack; The first quantum well stack and the third quantum well stack are configured to generate the blue light, and the second quantum well stack is configured to generate the green light; The red light-emitting diode structure further includes a red light-emitting multi-quantum-well active region of a second material having a second emission peak; and The first material is indium gallium nitride and the second material is aluminum gallium indium phosphide.

2. The full-color light-emitting diode microdisplay according to claim 1, wherein the first quantum well stack and the third quantum well stack each comprise one or more blue light-emitting quantum wells and one or more quantum barrier layers; and the second quantum well stack comprises one or more green light-emitting quantum wells and one or more quantum barrier layers.

3. The full-color light-emitting diode microdisplay according to claim 2, wherein the first quantum well stack comprises three blue light-emitting quantum wells; the second quantum well stack comprises one green light-emitting quantum well; and the third quantum well stack comprises one blue light-emitting quantum well.

4. The full-color light-emitting diode microdisplay according to claim 3, wherein: Each blue-emitting quantum well is an In with a first thickness between 1 nm and 10 nm. x Ga 1-x N layers, where x is any value between 0.1 and 0.2; and The green luminescent quantum well is an In₂ structure with a second thickness between 1 nm and 5 nm. y Ga 1-y N layers, where y is any value between 0.2 and 0.

3.

5. The full-color light-emitting diode microdisplay according to claim 1, wherein the blue / green dual-wavelength light-emitting diode structure further comprises: A buffer layer comprising an undoped gallium nitride layer; n-doped semiconductor layer, comprising a Si-doped n-GaN layer and an indium gallium nitride shallow well; as well as The p-doped semiconductor layer includes a Mg-doped p-GaN layer and a Mg-doped p-In layer stacked on top of the Mg-doped p-GaN layer. 0.02 Ga 0.98 N layers.

6. The full-color light-emitting diode microdisplay according to claim 1, wherein the red light-emitting diode structure further comprises: n-side layers, including Si-doped n-GaAs layers, Si-doped n-AlGaInP layers and Si-doped n-AlInP layers; as well as The p-side layers include Zn or Mg-doped p-AlInP layers and Zn or Mg-doped p-GaP layers. in: The red-emitting multi-quantum-well active region is sandwiched between the n-side layer and the p-side layer; and The red-emitting multi-quantum-well active region includes one or more red-emitting AlGaInP quantum wells sandwiched between two AlGaInP quantum barrier layers.

7. The full-color light-emitting diode microdisplay according to claim 1, wherein: The blue / green dual-wavelength light-emitting diode structure further includes an electron blocking layer; The electron blocking layer further comprises Mg doping at a concentration of 1×10⁻⁶. 17 cm -3 and 1×10 20 cm -3 One or more Mg-doped Al x Ga 1-x N and In y Ga 1-y N layers; and x is any value between 0.01 and 0.3, and y is any value between 0 and 0.

3.

8. The full-color light-emitting diode microdisplay according to claim 1, wherein the dual-wavelength multi-quantum-well active region and the red light-emitting multi-quantum-well active region are formed on two different epitaxial layers that do not overlap vertically.

9. The full-color light-emitting diode microdisplay according to claim 7, wherein the dual-wavelength multi-quantum-well active region is located at a lower vertical position closer to the substrate than the red light-emitting multi-quantum-well active region.

10. The full-color light-emitting diode microdisplay according to claim 1, wherein: The blue / green dual-wavelength light-emitting diode structure further includes an n-doped semiconductor layer and a p-doped semiconductor layer; The red light-emitting diode structure further includes an n-side layer and a p-side layer; The dual-wavelength multi-quantum-well active region is sandwiched between the n-doped semiconductor layer and the p-doped semiconductor layer, wherein the p-doped semiconductor layer is above the dual-wavelength multi-quantum-well active region and the n-doped semiconductor layer; and The red luminescent multi-quantum well active region is sandwiched between the n-side layer and the p-side layer, wherein the n-side layer is above the red luminescent multi-quantum well active region and the p-side layer.

11. The full-color light-emitting diode microdisplay according to claim 1, wherein the first light-emitting diode, the second light-emitting diode and the third light-emitting diode are bonded to a driver panel via a plurality of sub-pixel pads, wherein the driver panel is a CMOS driver chip, a thin-film transistor driver backplane, an in-panel gate circuit or other driver panel including circuitry on a panel substrate.

12. The full-color light-emitting diode microdisplay of claim 11, wherein the dual-wavelength multi-quantum-well active region is located at a lower vertical position closer to the driver panel than the red light-emitting multi-quantum-well active region.

13. The full-color light-emitting diode microdisplay according to claim 11, wherein: The blue / green dual-wavelength light-emitting diode structure further includes an n-doped semiconductor layer and a p-doped semiconductor layer; The red light-emitting diode structure further includes an n-side layer and a p-side layer; The dual-wavelength multi-quantum-well active region is sandwiched between the n-doped semiconductor layer and the p-doped semiconductor layer, wherein the n-doped semiconductor layer is above the dual-wavelength multi-quantum-well active region and the p-doped semiconductor layer; and The red luminescent multi-quantum well active region is sandwiched between the n-side layer and the p-side layer, wherein the n-side layer is above the red luminescent multi-quantum well active region and the p-side layer.

14. A method for manufacturing a full-color light-emitting diode microdisplay, the full-color light-emitting diode microdisplay comprising a first light-emitting diode having a blue / green dual-wavelength light-emitting diode structure for emitting blue light, a second light-emitting diode having the blue / green dual-wavelength light-emitting diode structure for emitting green light, and a third light-emitting diode comprising a red light-emitting diode structure for emitting red light, the method comprising: Forming a first monolithic light-emitting diode array having the blue / green dual-wavelength light-emitting diode structure on a substrate includes the steps of depositing or growing a buffer layer, a first n-doped semiconductor layer, a dual-wavelength multi-quantum-well active region of a first material having two emission peaks, an electron blocking layer, and a p-doped semiconductor layer on the substrate. Forming a second monolithic light-emitting diode array having the red light-emitting diode structure on a gallium arsenide substrate includes the steps of depositing or growing an n-side layer, a red light-emitting multi-quantum-well active region of a second material having a second emission peak, and a p-side layer on the gallium arsenide substrate. Perform flip-chip bonding to heterogeneously integrate the first monolithic LED array and the second monolithic LED array; as well as The gallium arsenide substrate is removed by performing dry etching, wet etching, or a combination of dry and wet etching. The first material is indium gallium nitride, and the second material is aluminum gallium indium phosphide.

15. The method of claim 14, wherein the step of forming the first monolithic light-emitting diode array having the blue / green dual-wavelength light-emitting diode structure further comprises: Apply an etching mask, including photoresist, silicon dioxide, or silicon nitride; Etching is performed to remove a portion of all epitaxial layers above the substrate to expose the first light-emitting diode, the second light-emitting diode, and the multilayer structure, wherein the multilayer structure is provided to accommodate the third light-emitting diode and to connect the third light-emitting diode to the first monolithic light-emitting diode array; A current spreading layer, an n-metal layer, and a p-metal layer are deposited on the first light-emitting diode and the second light-emitting diode by evaporation or sputtering, respectively, wherein the current spreading layer is an indium tin oxide or a Ni / Au metal stack; n-metal layers are deposited and patterned on the current spreading layers of the first light-emitting diode and the second light-emitting diode, respectively; as well as Blue and green color filters were coated on the top of the first and second light-emitting diodes, respectively, and then hard baking was performed.

16. The method of claim 14, wherein the step of forming the second monolithic light-emitting diode array having the red light-emitting diode structure further comprises: Apply an etching mask, including photoresist, silicon dioxide, or silicon nitride; Etching is performed to remove a portion of all epitaxial layers above the gallium arsenide substrate to expose the third light-emitting diode; A p-metal layer and an n-metal layer are deposited and patterned on the third light-emitting diode as p-electrodes and n-electrodes, respectively. A passivation layer is deposited and patterned, wherein the passivation layer is silicon dioxide, silicon nitride, Al2O3, hard-baked photoresist, organic polymer, or any combination thereof; as well as P-metal bumps are deposited and patterned on the p-metal layer for electrically connecting the third light-emitting diode to the first monolithic light-emitting diode array.

17. The method of claim 14, wherein the step of forming the second monolithic light-emitting diode array having the red light-emitting diode structure further comprises the step of depositing or growing an etch stop layer, wherein the etch stop layer is provided to improve etch selectivity when the gallium arsenide substrate is removed.

18. The method of claim 14, wherein the step of performing flip-chip bonding further comprises: A bottom filler layer is coated on the first monolithic light-emitting diode array and the second monolithic light-emitting diode array; as well as A bonding temperature of 150°C to 300°C is applied for 0.5 minutes to 10 minutes to bond the first monolithic LED array and the second monolithic LED array and to cure the bottom filler layer.

19. The method of claim 14, further comprising: Perform flip-chip bonding to bond the first monolithic light-emitting diode array onto a driver panel, wherein the driver panel is a CMOS driver chip, a thin-film transistor driver backplane, an in-panel gate circuit, or other driver panel that includes circuitry on a panel substrate. as well as Before performing flip-chip bonding to heterogeneously integrate the first monolithic LED array and the second monolithic LED array, the substrate is removed by performing dry etching, wet etching, or a combination of dry etching and wet etching.

20. The method of claim 14, wherein: The dual-wavelength multi-quantum-well active region includes one or more blue-emitting quantum wells and one or more green-emitting quantum wells. in: Each blue-emitting quantum well is an In with a first thickness between 1 nm and 10 nm. x Ga 1-x N layers, where x is any value between 0.1 and 0.2; and The green luminescent quantum well is an In₂ structure with a second thickness between 1 nm and 5 nm. y Ga 1-y N layers, where y is any value between 0.2 and 0.3.

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