Micro light emitting diode, micro light emitting diode device, display and method thereof

Abstract

The invention relates to various aspects of a [mu]-LED or a [mu]-LED arrangement for augmented reality or light applications, in particular in the automotive field. The [mu]-LEDs are characterized by particularly small dimensions in the range of several [mu] m.

Description

[0001] This invention is a divisional application of the parent application, which is filed on January 29, 2020, with application number 202080023800.9 and invention title "Miniature Light Emitting Diode, Miniature Light Emitting Diode Device, Display and Method Thereof" (PCT International Application PCT / EP2020 / 052191 entered the Chinese National Phase).

[0002] This patent application claims priority to the following German patent applications: DE 10 2019 201114.4, dated January 29, 2019; DE 10 2019 111 766.6, dated May 7, 2019; DE 10 2019 112 124.8, dated May 9, 2019; DE 10 2019 116 313.7, dated June 14, 2019; DE 10 2019 131 506.9, dated November 21, 2019; DE 10 2019 118 251.4, dated July 5, 2019; DE 10 2019 118 082.1, dated July 4, 2019; and DE 10 2019, dated March 29, 2019. 108 260.9, DE 10 2019 on September 20, 2019 125 349.7, DE 10 2019 on May 13, 2019 112 490.5, DE 10 2019 on May 14, 2019 112 604.5, DE 10 2019 on May 14, 2019 112 609.6, DE 10 2019 on January 31, 2019 102 509.5, DE 10 2019 on June 7, 2019 115 479.0, DE 10 2019 on May 14, 2019 112 616.9, DE 10 2019 on May 23, 2019 113791.8, DE 10 2019 110 499.8 on April 23, 2019, DE 10 2019 110523.4 on April 23, 2019, DE 10 2019 130 934.4 on November 15, 2019, DE 10 2019 114321.7 on May 28, 2019, DE 10 2019 127 425.7 on October 11, 2019, DE 10 2019 112639.8 on May 14, 2019, DE 10 2019 112 605.3 on May 22, 2019 113636.9, DE 10 2019 103 365.9 on February 11, 2019, DE 10 2019 116312.9 on June 14, 2019, DE 10 2019 115 991.1 on June 12, 2019, DE 10 2019 125875.8 on September 25, 2019, DE 10 2019 127 424.9 on October 11, 2019, DE 10 2019 118085.6 on July 4, 2019, DE 10 2019 125 336 on September 20, 2019.5. DE 10 2019 113793.4 on May 23, 2019; DE 10 2019 110 500.5 on April 23, 2019; DE 10 2019 111 767.4 on May 7, 2019; DE 10 2019 121 672.9 on August 12, 2019; DE 10 2019 118 084.8 on July 4, 2019; DE 10 2019 113 768.3 on May 23, 2019; DE 10 2019 113 792.6 on May 23, 2019; DE 10 2019 110 on April 23, 2019. 497.1, DE 10 2019 114 442.6 dated May 29, 2019, DE 10 2019 129 209.3 dated October 29, 2019, DE 10 2019 130 821.6 dated November 14, 2019, and DE10 2019 130 866.6 dated November 15, 2019, the disclosures of which are incorporated herein by reference, and also claim Danish patent applications DK PA201970059, DK PA201970060, and DK, dated January 29, 2019. The patent claims priority to PA201970061, the disclosure of which is incorporated herein by reference, and also to U.S. patent application US 62 / 937,552, dated November 19, 2019, the disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to miniature light-emitting diodes, miniature light-emitting diode devices, and displays. Background Technology

[0004] The ongoing developments in the Internet of Things (IoT) and communications fields have opened doors to a variety of new applications and designs. These designs and applications offer greater effectiveness and efficiency for development, service, and manufacturing purposes.

[0005] One aspect of the new design involves augmented reality, or virtual reality. The general definition of “augmented reality” is: “an interactive experience of a real environment in which objects in the real world are extended by computer-generated perceptible information.”

[0006] Information is primarily conveyed through visualization, but not limited to visual perception. Sometimes, tactile or other sensory perceptions can be used to augment reality. In the case of visualization, the overlaid sensory visual information can be constructive—that is, supplementing the natural environment—or non-constructive, such as by covering a portion of the natural environment. In some applications, interaction with the overlaid sensory information may also occur in one or another manner. Thus, augmented reality enhances the user's continuous perception of the real environment.

[0007] In contrast, "virtual reality" replaces the user's real environment with a completely simulated one. In other words, while users can perceive the real world at least partially in an augmented reality environment, the environment in virtual reality is completely simulated and may differ significantly from reality.

[0008] Augmented reality (AR) can be used to improve natural environmental conditions, thereby enriching the user experience or supporting them in performing certain tasks. For example, users can use displays with AR capabilities to assist them in performing certain tasks. By overlaying information about real objects to provide clues to the user, it provides additional information, enabling them to act faster, safer, and more efficiently during manufacturing, repair tasks, or other services. In the medical field, AR technology can be used to guide and support doctors in diagnosing and treating patients. In development, engineers can directly experience their test results, making it easier to evaluate the outcomes. In the tourism or events industry, AR can provide users with additional information about attractions, history, and more. AR can also support learning activities or tasks. Summary of the Invention

[0009] The following introduction illustrates various aspects of μ (micro) displays in automotive and augmented reality applications. These aspects include devices, displays, controls, process techniques, and other suitable features for augmented reality and automotive applications. This includes aspects designed to generate light through indicators, displays, etc. Additionally, aspects of control circuitry, power supplies, and optical coupling outputs, light guiding, and light focusing are listed, along with applications of such devices, explained using various examples.

[0010] Because of the various limitations and challenges posed by the small size of the light-generating components, combining various aspects is not only advantageous but often necessary. For ease of handling, this disclosure is divided into several parts with similar topics. However, it should not be explicitly understood that features of one topic cannot be combined with other topics. Rather, aspects from different subject areas must be combined to create displays for augmented reality or other applications or in the automotive field.

[0011] To consider the following solutions, some terms and expressions should be explained to define common and shared understanding. For clarity, the listed terms are generally used herein. However, in individual cases, they may deviate from the intended interpretation, where such deviation is identifiable.

[0012] "Active Matrix Display"

[0013] The term "active matrix display" originally referred to liquid crystal screens containing a matrix of thin-film transistors controlled by LCD (liquid crystal display) pixels. Each individual pixel has a circuit with active components (mainly transistors) and power connections. However, this technology should not be limited to liquid crystals at present, but should specifically refer to the control of μ-LEDs (micro-light-emitting diodes) or μ displays.

[0014] "Active Matrix Carrier Substrate"

[0015] An "active matrix carrier substrate" or "active matrix backplane" refers to the driving device for the light-emitting diodes (LEDs) of a display with thin-film transistor (TFT) circuitry. Here, these circuits can be integrated into or applied to the backplane. The "active matrix carrier substrate" has one or more interface contacts that form an electrical connection with the μ-LED display structure. Therefore, the "active matrix carrier substrate" can be part of or carry an active matrix display.

[0016] "Active layer"

[0017] An active layer is a layer in an optoelectronic device or light-emitting diode (LED) where charge carriers recombine. In its simplest form, an active layer is characterized by regions of two adjacent semiconductor layers with different conductivity types. More complex active layers include quantum wells (see related description), multiple quantum wells, or other structures with additional properties. Structural and material systems can also be used to define the band gap in the active layer (see related description), which defines the wavelength and thus the color of light.

[0018] "Alvarez Lens Device"

[0019] The optical path of the video glasses can be adjusted by using Alvarez lens pairs. The adjustment optics include Alvarez lens devices, particularly rotatable variants with moiré lens devices. Here, beam deflection is determined by the first derivative of the individual phase plate morphologies, approximately z = ax² + by² + cx + dy + e for the radiation direction z and the transverse directions x and y, and is determined by the offset of the two phase plates arranged in pairs in the transverse directions x and y. For alternative designs, pivotable prisms are provided in the adjustment optics.

[0020] Augmented Reality (AR)

[0021] This is an interactive experience of a real-world environment, where the filmed project is located in the real world and enhanced by computer-generated perceptible information. Augmented reality is understood as a computer-aided extension of the perception of reality through such computer-generated perceptible information. This information can appeal to all human senses. However, augmented reality often refers only to the visual representation of information, i.e., images or videos with computer-generated additional information or virtual objects added through fade-in / overlay. Applications and explanations of how augmented reality works can be found in the introduction to the examples and below.

[0022] "car"

[0023] "Automotive" generally refers to motor vehicles or the automotive industry. Therefore, the term is intended to include this branch, but also all other industry branches, including microdisplays or general luminous indicators with very high resolution and μ-LEDs.

[0024] "band gap"

[0025] The energy gap between the valence band and conduction band of a solid is called the band gap, also known as the band gap or band exclusion zone. Its electrical and optical properties depend largely on the size of the band gap. The size of the band gap is usually expressed in electron volts (eV). The band gap is used to distinguish metals, semiconductors, and insulators. The band gap can be tuned (i.e., changed) by various measures such as spatial doping to detune the crystal structure or by altering the material system. Material systems with a so-called direct band gap, where the maximum value of the valence band and the minimum value of the conduction band are superimposed in momentum space, allow electron-hole pairs to recombine with emitted light.

[0026] "Prague Grating"

[0027] A Bragg fiber grating is a special optical interference filter etched into an optical waveguide. Wavelengths within the filter bandwidth near λB are reflected. Various methods are used to generate periodic modulation of the refractive index within the fiber core of the waveguide. This creates regions with high and low refractive indices that reflect light of specific wavelengths (bandstop). The center wavelength of the filter bandwidth in a single-mode fiber is determined by the Bragg condition.

[0028] "Directionality"

[0029] Directivity, or directionality, is used to describe the radiation characteristics of μ-LEDs or other light-emitting components. High directionality corresponds to highly directional radiation or a low-radiation cone. Typically, the goal is to achieve a high level of directional radiation to minimize crosstalk between light and adjacent pixels. Consequently, the brightness of the light-emitting component varies depending on the viewing angle, thus differing from a Lambertian emitter.

[0030] Directionality can be altered, for example, by mechanical or other means on the side used for emission. Besides lenses, this includes photonic crystals or columnar structures (pillar structures) arranged on the emission surface of the pixelated array or, in particular, on an arrangement of μ-LEDs. These create a virtual bandgap that reduces or prevents the light vector from diffusing along the emission surface.

[0031] "Far field"

[0032] The terms near field and far field describe the spatial regions surrounding components that emit electromagnetic waves and have distinct characteristics. Typically, these spatial regions are divided into three areas: the reactive near field, the transition field, and the far field. In the far field, electromagnetic waves propagate as plane waves, independent of the radiating element.

[0033] "Screen window effect"

[0034] The screen-door effect (SDE) is a permanently visible image artifact in digital video projectors. The term describes an undesirable, technically relevant dark distance between individual pixels or their projected information, taking the form of a screen. This distance originates from the construction, as the conductive circuitry used for control runs between the individual LCD segments, where light is swallowed up and cannot reach the screen. If small photoelectric light-emitting devices are used, particularly μ-LEDs, or the distance between individual LEDs is too large, the low packing density produced when viewing a single LED can result in a visible difference in pixel areas between bright and dark spots. This so-called screen-door effect is particularly noticeable when viewed from a smaller distance, especially in applications such as VR (virtual reality) glasses. When the illumination differences within a pixel persist periodically across the entire matrix arrangement, the sub-pixel structure is often perceived and annoying. Therefore, the screen-door effect should be avoided as much as possible in automotive and augmented reality applications.

[0035] "Flip Chip"

[0036] Flip chip assembly is a method of fabrication and connection technology used to contact unpackaged semiconductor chips via contact bumps known as "bumps." With flip chip assembly, the chip can be directly mounted without additional interconnects, with its effective contact surface facing down (towards the substrate / circuit carrier) above the bumps. This results in a particularly small housing size and shorter conductor length. Therefore, flip chips are especially suitable for electronic semiconductor components that contact on their back side. Such components may also require special transfer techniques, such as using an auxiliary carrier. In the case of flip chips, the radiation direction is typically opposite to the side of the contact surface.

[0037] "trigger"

[0038] A flip-flop, also commonly known as a bistable switching stage or bistable switching element, is an electronic circuit with two stable output signal states. The current state depends not only on the currently available input signal but also on the state that existed prior to the point in time being considered. There is no time correlation, only event correlation. Due to its bistable nature, a flip-flop can store one bit of data indefinitely. However, unlike other types of memory, a voltage supply must always be guaranteed. Flip-flops are a fundamental component of sequential circuits and an essential part of digital technology, thus forming a basic element in many electronic circuits, from quartz clocks to microprocessors. In particular, as a basic one-bit memory, it is a fundamental element of the static memory module used in computers. Some embodiments may use different types of flip-flops or other buffer circuits to store state information. Their respective input and output signals are digital, meaning they alternate between logical "false" and logical "true". These values ​​are also referred to as "low" 0 and "high" 1.

[0039] Head-up display

[0040] A head-up display (HUD) is a display system or projection device in which a user maintains a certain head posture or gaze as information is projected into the user's field of view. HUDs are augmented reality systems. In some cases, HUDs incorporate sensors that determine the direction or orientation of the user's gaze in space.

[0041] Horizontal LED

[0042] In the case of horizontal LEDs, the electrical connection is located on the common side of the LED. This is typically the back side of the LED, away from the light-emitting surface. Therefore, horizontal LEDs have contacts formed only on the surface side.

[0043] "Interference filter"

[0044] An interference color filter is an optical component that uses the interference effect to filter light in a frequency-dependent manner (i.e., in a color-dependent manner for visible light).

[0045] "Collimation"

[0046] In optics, collimation refers to the parallel direction of diverging rays. The associated lens is called a collimator or condenser. A collimated beam contains mostly parallel rays and therefore has minimal scattering during propagation. Its use in this sense relates to the scattering of light emitted from a light source. A collimated beam emitted from a surface is highly dependent on the angle of radiation. In other words, the radiance (unit power per unit angle of a projected light source area) of a collimated light source varies with increasing angle. Light can be collimated in various ways, such as by using a special lens placed in front of the light source. Therefore, collimated light can also be considered as light with a high degree of directional dependence.

[0047] "Converter Materials"

[0048] Converter materials are materials suitable for converting light of a first wavelength into light of a second wavelength, shorter than the second. These include various permanent inorganic and organic dyes as well as quantum dots. Converter materials can be applied and constructed in a variety of processes.

[0049] "Lambert Launcher"

[0050] The so-called Lambertian radiation characteristic is required in many applications. This means that the luminescent surface ideally has a uniform radiation density on its surface, resulting in a vertically circular distribution of radiation intensity. Since humans can only assess brightness with their eyes (brightness is the luminous equivalent of illuminance), such Lambertian materials appear equally bright regardless of the viewing direction. This uniform, angle-independent brightness can be an important quality factor, especially for curved and flexible display surfaces, which is sometimes difficult to achieve with currently available displays due to their structure and LED technology.

[0051] LEDs and μ-LEDs are similar to Lambertian emitters and emit light at a large spatial angle. Depending on the application, further steps can be taken to improve radiation characteristics, or greater directionality can be attempted (see related notes).

[0052] "Conductivity type"

[0053] The term "conductivity type" refers to the majority (n- or p-type) charge carriers in a given semiconductor material. That is, a semiconductor material doped with n (negative) type is considered to be of n conductivity type. Similarly, if a semiconductor material is n-type, then it is n-type doped. The term "active" region in a semiconductor refers to the boundary region between an n-type doped layer and a p (positive)-type doped layer. Radiative recombination of p-type and n-type charge carriers occurs in this region. In some embodiments, the active region is further constructed and includes, for example, a quantum well or quantum dot structure.

[0054] "Light field display"

[0055] A display technology that projects raster images directly onto the retina of the eye is called a Virtual Retinal Display (VNA) or Light Field Display. The user gains the impression of a canvas floating in front of them. Light Field Displays can be provided as glasses, projecting raster images directly onto the user's retina. Using a Virtual Retinal Display, an image is created within the user's eye through direct projection of the retina. Light Field Displays are augmented reality systems.

[0056] "Plate printing" or "photolithography"

[0057] Photolithography is one of the core methods in semiconductor and microsystems technology, used to manufacture integrated circuits and other products. In this process, the image of a photomask is transferred onto a photosensitive photoresist through exposure. Subsequently, the exposed areas of the photoresist are dissolved (or the unexposed areas can also be dissolved when the photoresist cures under light). This forms a lithographic mask, which can be further processed through chemical and physical processes, such as applying material to the open areas or etching recesses in the open areas. The remaining photoresist can then be removed.

[0058] “μ-LED”

[0059] μ-LEDs are optoelectronic devices with edge lengths less than 70 μm, particularly less than 20 μm, and especially in the range of 1 μm to 10 μm. Another range is between 10 and 30 μm. This results in a range of several hundred μm. 2 Up to tens of μm 2 The area of ​​a μ-LED is approximately 60 μm², with an edge length of approximately 8 μm. In some cases, the edge length of a μ-LED is 5 μm or less, resulting in a size less than 30 μm². For example, the typical height of such a μ-LED is between 1.5 μm and 10 μm.

[0060] Besides classic lighting applications, μ-LEDs are primarily used in displays. Here, μ-LEDs form pixels or subpixels and emit light of a specified color. Due to their small pixel size and high density at close range, μ-LEDs are also suitable for small, monolithic displays used in AR applications.

[0061] Due to the extremely small size of μ-LEDs, their production and processing are significantly more difficult compared to previous large LEDs. This also applies to other components such as contact lenses, packaging, and lenses. Some aspects feasible in large optoelectronic components cannot be achieved in μ-LEDs, or must be achieved in different ways. In this respect, μ-LEDs are therefore significantly different from traditional LEDs, i.e., light-emitting elements with an edge length of 200 μm or more.

[0062] μ-LED array

[0063] See Microdisplay

[0064] "Miniature display"

[0065] A microdisplay, or μ-LED array, is a matrix with a large number of pixels arranged in prescribed rows and columns. Functionally, a μ-LED array typically forms a matrix primarily composed of μ-LEDs of the same type and color. Therefore, it provides a larger surface area for illumination. On the other hand, the purpose of a μ-display is to transmit information, which often also necessitates different colors or positional control for each individual pixel or subpixel. A microdisplay can consist of multiple μ-LED arrays, formed together on a backplane or other carrier. However, μ-LED arrays can also be used to form microdisplays.

[0066] Each pixel is on the order of a few μm, similar to a μ-LED. Therefore, a μ-display with 1920×1080 pixels, each with a 5μm μ-LED, and directly adjacent pixels has an overall size of 10 mm². In other words, a microdisplay or μ-LED array is a small-scale device implemented using μ-LEDs.

[0067] Microdisplays or μ-LED arrays can be formed from a single, identical component. The μ-LEDs in a μ-LED array can be formed monolithically. Such microdisplays or μ-LED arrays are called monolithic μ-LED arrays or microdisplays.

[0068] Alternatively, both components can be formed by growing μ-LEDs individually on a substrate and then arranging them individually or in groups on a carrier using a so-called pick-and-place process, maintaining a certain distance between them. Such a microdisplay or μ-LED array is referred to as non-monolithic. In a non-monolithic microdisplay or μ-LED array, other distances between individual μ-LEDs are also possible. These distances can be flexibly chosen depending on the application and implementation. Therefore, such a microdisplay or μ-LED array can also be referred to as a pitch-extended component. In a pitch-extended microdisplay or μ-LED array, the μ-LEDs are arranged at greater distances when delivered to the carrier than they are on the growth substrate. In a non-monolithic microdisplay or μ-LED array, each individual pixel may each include a blue-emitting μ-LED, a green-emitting μ-LED, and a red-emitting μ-LED.

[0069] To leverage the advantages of both monolithic and non-monolithic μ-LED arrays within a single module, monolithic μ-LED arrays can be combined with non-monolithic μ-LED arrays in a microdisplay. This allows the microdisplay to be used for different functions or applications. Such a display is called a hybrid display.

[0070] "μ-LED nanopillars"

[0071] μ-LED nanopillars are typically a stack of semiconductor layers with an active layer, thus forming a μ-LED. The edge length of a μ-LED nanopillar is less than its height. For example, the edge length of a μ-LED nanopillar is approximately 10 nm to 300 nm, while the height of the device may be 200 nm to 1 μm or higher.

[0072] "μ column"

[0073] μ-pillars or pillars specifically refer to a geometric structure, particularly a rod or bar, or generally a slender, cylindrical structure. The spatial dimensions of manufactured μ-pillars range from μm to nm. Therefore, nanopillars are also included herein.

[0074] "Nanopillars"

[0075] In nanotechnology, nanopillars are a design concept for nanoscale objects. Each of them ranges in size from approximately 10 nm to 500 nm. They can be synthesized from metallic or semiconducting materials. The aspect ratio (length divided by width) is 3 to 5. Nanopillars are made through direct chemical synthesis. A combination of ligands acts as a shape control agent and attaches to different faces of the nanopillar with varying strengths. This allows for different designs of nanopillars with different growth rates to produce an elongated object. μLED nanopillars are such nanopillars.

[0076] Miniature LED

[0077] Its size ranges from 100μm to 750μm, especially in the range greater than 150μm.

[0078] Moiré effect and Moiré lens array

[0079] The moiré effect refers to the noticeably coarser gratings produced by the superposition of regular, finer gratings. The resulting pattern, resembling a pattern from interference, is a special case of aliasing caused by undersampling. In signal analysis, aliasing occurs when the signal being sampled contains frequency components higher than half the sampling frequency. In image processing and computer graphics, aliasing occurs when an image is sampled, resulting in patterns not present in the original image. A moiré lens array is a special case of an Alvarez lens array.

[0080] "Single component"

[0081] A single-unit component refers to a component made from a single part. A typical example of such a component is a single-pixel array, where the array is made from a single part, and the array's μ-LEDs are fabricated together on a carrier.

[0082] "Optical mode"

[0083] A mode is a description of a wave's specific time-static properties. The wave is described as a sum of different modes. These modes differ in their spatial distribution of intensity. The shape of a mode is determined by the boundary conditions of wave propagation. Analysis based on vibration modes can be applied to both standing waves and continuous waves. For electromagnetic waves such as light, lasers, and radio waves, the following types of modes are distinguished: TEM (transverse electromagnetic) mode, TE (transverse electric) or H (magnetic) mode, TM (transverse magnetic) or E (electric) mode. TEM (transverse electromagnetic) mode: Both the electric and magnetic fields are always perpendicular to the direction of propagation. This mode can only propagate when there are two isolated conductors (equipotential surfaces) in a coaxial cable or when there are no electrical conductors in a gas laser or optical waveguide. TE or H mode: Only the electric field component is perpendicular to the direction of propagation, while the magnetic field component points in the direction of propagation. TM or E mode: Only the magnetic field component is perpendicular to the direction of propagation, while the electric field component points in the direction of propagation.

[0084] "Optoelectronic components"

[0085] An optoelectronic component is a semiconductor substrate that generates light through recombination of charge carriers during operation, and then emits light. The emitted light can range from infrared to ultraviolet, with the wavelength depending on various parameters, the material system used, and the doping. Optoelectronic components are also known as light-emitting diodes (LEDs).

[0086] For the purposes of this disclosure, the terms optoelectronic component and light-emitting component are used synonymously. Therefore, in terms of its geometry, a μ-LED (see related description) is a specific type of optoelectronic component. In displays, optoelectronic components are typically monolithic or single components placed on a matrix.

[0087] "Passive matrix backplane" or "passive matrix carrier substrate"

[0088] A passive matrix display is a matrix display in which individual pixels are passively controlled (without additional electronic components for each pixel). The light-emitting diodes (LEDs) of the display can be controlled by the circuitry of an integrated circuit (IC). In contrast, a screen with active pixels controlled by transistors is called an active matrix display. A passive matrix carrier substrate is part of and supports the passive matrix display.

[0089] "Photonic crystal" or "photonic structure"

[0090] A photonic structure can be a photonic crystal, a quasi-periodic, or a deterministic aperiodic photonic structure. A photonic structure generates a band structure for photons through periodic variations in the optical refractive index. This band structure can have a band gap within a specific frequency range. This means that photons cannot propagate through the photonic structure in all spatial directions. In particular, propagation parallel to the surface is generally blocked, but propagation perpendicular to the surface is possible. In this way, the photonic structure or photonic crystal determines propagation in a specific direction. It blocks or reduces the radiation along one direction and thus produces a radiation or a beam of radiation, directed as needed to a spatial region or emission region provided for this purpose.

[0091] Photonic crystals are photonic structures that appear or are generated in transparent solids. Photonic crystals are not necessarily crystals; their name comes from the diffraction and reflection effects of X-rays in crystals, due to their lattice constant. The structural size is equal to or greater than one-quarter of the photon's wavelength, meaning they range from 1 μm to several μm. They are generated using classical photolithography or through self-organizing processes.

[0092] Alternatively, similar or identical properties of photonic crystals can also be produced with aperiodic but still ordered structures. Such structures are in particular quasi-periodic or well-defined aperiodic structures. For example, this could be a helical arrangement of photons.

[0093] In particular, the so-called two-dimensional photonic crystal is mentioned here by way of example, which has a periodic variation of optical refractive index in two spatial directions that are perpendicular to each other, especially in two spatial directions that are parallel to the light emitting surface and perpendicular to each other.

[0094] However, one-dimensional photonic structures, particularly one-dimensional photonic crystals, also exist. One-dimensional photonic crystals exhibit a periodic change in refractive index along a single direction. This direction can extend parallel to the light exit surface. The one-dimensional structure allows beam shaping to occur in a first spatial direction. In a photonic structure, the photonic effect can be achieved in just a few cycles. The photonic structure can be designed, for example, to ensure that electromagnetic radiation is at least approximately collimated relative to the first spatial direction. Therefore, a collimated beam can be generated at least relative to the first spatial direction.

[0095] "Pixel"

[0096] The individual color values ​​of a digital photodiode pattern, and the surface elements required to record or display these color values ​​in an image sensor or screen with photodiode control, are called pixels, image points, image cells, or image dots. Therefore, a pixel is a positionable element in a display device and has at least one light-emitting device. Pixels have a definite size, and adjacent pixels are separated by a defined spacing or pixel space. In displays, especially μ displays, three (or several with added redundancy) sub-pixels of different colors are typically combined into one pixel.

[0097] "planar array"

[0098] A planar array is a substantially flat surface. It is typically smooth and has no protruding structures. Generally, surface roughness is undesirable and does not provide the desired functionality. A planar array is, for example, a monolithic planar array with multiple optoelectronic components.

[0099] Pulse Width Modulation

[0100] Pulse Width Modulation (PWM) is a type of modulation used to control components, particularly μ-LEDs. A PWM signal controls a switch configured to turn on and off the current flowing through the corresponding μ-LED, thus causing the μ-LED to light up or not. When using PWM, the output provides a square wave signal with a fixed frequency f. During each cycle T (= 1 / f), the relative amount of on-time compared to the off-time determines the brightness of the light emitted by the μ-LED. The longer the on-time, the brighter the light.

[0101] "Quantum trap"

[0102] A quantum well is understood as a potential line in a strip structure within one or more semiconductor materials, which restricts the degree of freedom of a particle to move in one spatial dimension (typically the z-direction). Thus, a charge carrier can only occupy a planar region (the xy-plane). The width of the quantum well determines the quantum mechanical states that the particle can adopt, resulting in the formation of energy levels (sub-bands), meaning the particle can only have discrete (potential) values.

[0103] "complex"

[0104] There is generally a distinction between radiative and nonradiative recombination. The latter produces a photon that can leave the component. Nonradiative recombination results in the generation of acoustic quanta, which heat the component. The ratio of radiative to nonradiative recombination is an important parameter that depends on the component size, among other factors. Typically, the smaller the component, the smaller the ratio, thus increasing nonradiative recombination relative to radiative recombination.

[0105] Refresh time

[0106] The refresh time is the time after which units such as displays must be rewritten to prevent information loss or premature refresh by external factors.

[0107] "Rohchip" or "light-emitting element"

[0108] A light emitter, or virgin chip, is a semiconductor structure fabricated on a wafer and then separated from it. This semiconductor structure is adapted to generate light after electrical contact during operation. Therefore, in this context, a virgin chip is a semiconductor structure containing active layers for generating light. Virgin chips are typically separated after contact, but can also be further processed in array form.

[0109] "Slot antenna"

[0110] A slot antenna is a special type of antenna in which, instead of surrounding the metallic structure with air (as a non-conductor) in space, an interruption is provided in the metallic structure (e.g., a metal plate, waveguide, etc.). This interruption causes the reflection of electromagnetic waves, the wavelength of which depends on the geometry of the interruption. Typically, the interruption follows the dipole principle, but theoretically it can have any other geometry. Therefore, a slot antenna comprises a metallic structure with a cavity resonator whose length is on the order of the visible light wavelength. The metallic structure can be arranged in or surrounded by an insulating material. The metallic structure is typically grounded to establish a certain potential.

[0111] Field of view

[0112] The field of view (FOV) refers to the area within the field of view of an optical device, solar sensor, camera's image surface (film or recording sensor), or perspective display where events or changes can be perceived and recorded. The field of view is specifically the area that a person can see without moving their eyes. Regarding augmented reality and prominent objects placed in front of the eyes, the field of view includes the area specified as multiple angles of view during stable eye fixation.

[0113] "Subpixel"

[0114] A subpixel describes the internal structure of a pixel. Generally, the term "subpixel" is associated with a higher resolution than that expected from a single pixel. A pixel can also contain several smaller subpixels, each emitting a different color. The overall color impression of a pixel is produced by the mixing of the individual subpixels. Therefore, a subpixel is the smallest locatable unit in a display device. Similarly, a subpixel has a specific size, smaller than the size of the pixel to which it belongs.

[0115] Vertical LED

[0116] Compared to horizontal LEDs, vertical LEDs have electrical connections on both the front and back sides. One of the two sides also forms a light-emitting surface. Therefore, a vertical LED has contacts formed on two opposing main surface sides. Consequently, a conductive yet transparent material must be deposited to ensure electrical contact while allowing light to pass through.

[0117] Virtual Reality

[0118] Virtual reality (VR) refers to the representation and simultaneous perception of reality and its physical properties in a real-time, computer-generated, interactive virtual environment. Virtual reality can replace the operator's real environment with a completely simulated environment.

[0119] The following sections will introduce various aspects of the μ-LED semiconductor structure. This includes the structural and material systems used for light emission. However, these aspects also involve key processing points.

[0120] In the field of augmented reality, and in automotive displays or other display devices with μ-LEDs, a fundamental aspect is that adjacent μ-LEDs in the device are also spaced apart as μ displays or μ arrays, making it impossible for the human eye to distinguish or identify individual μ-LEDs in such a device. Specifically, individual rows or columns of μ-LEDs arranged row by row or column by column cannot be distinguished or identified by the human eye. Therefore, the distance between μ-LEDs, or the pixel density and pixel pitch of the μ-LED array, should also be adjusted accordingly based on the distance between the observer and the μ-LED array, so that the observer's eye cannot distinguish individual μ-LEDs in the μ-LED array within the appropriate application.

[0121] Compared to arrays with organic LEDs (OLEDs) and liquid crystal displays (LCDs), μ-LED arrays have lower energy consumption and up to 10 6 Cd / m 2 The advantages of high brightness. Furthermore, μ-LED arrays can achieve extremely high pixel densities of up to 5000 pixels per inch (PPI) and nanosecond-level refresh rates when applied in displays. In addition, compared to OLED and LCD, μ-LED arrays have a very long lifespan and excellent stability in resisting environmental influences. Moreover, using μ-LED arrays allows for the adaptation of contrast range and / or resolution values ​​to desired values, such as application-specific adaptation.

[0122] Furthermore, arrays composed of μ-LEDs allow the light-emitting areas formed by the μ-LEDs to be adapted to fit desired shapes. This means that the application is not limited to ordinary displays, and μ-LED arrays can also be used in the automotive field, for example, using curved surfaces as displays or lighting devices. This area can be used to display information as well as a simpler light-emitting area for illumination or lighting.

[0123] One aspect involves the generation of different colors in a monolithic display. In a monolithic μ-LED array, each individual pixel can each contain, for example, a μ-LED that emits blue light, and each μ-LED can also have a converter material to partially or completely convert the blue light into secondary light, which, together with the blue primary light, produces mixed light, such as white light. Monolithic μ-LED arrays enable high brightness in the emitting area and are therefore advantageously used in automotive lamps, such as as a light source for automotive headlights.

[0124] Conversely, non-monolithic microdisplays or μ-LED arrays allow for the arrangement of other components, such as electronic components for operating the μ-LEDs, or sensors or detectors, using the gaps between adjacent pixels or μ-LEDs. Non-monolithic μ-LED arrays can be advantageously used, for example, in displays and displays with integrated sensors, particularly touchscreens, as well as for operating elements.

[0125] Some aspects primarily concern the arrangement and contact of vertical μ-LEDs with transparent and electrical overlays. The objective here is particularly to improve display performance when there are a large number of pixel counts per unit area. Due to the spatial location of the electrical contacts of the vertical μ-LEDs on the top side away from the carrier substrate, transparent or at least partially transparent conductive materials are considered, as already described in this application. For example, materials such as ITO (indium tin oxide), transparent or partially transparent mixed oxides that are semiconductive to visible light are known for this purpose, but these materials have relatively high surface resistivity.

[0126] Therefore, pixel elements in the form of one or more μ-LEDs have been proposed for generating image dots in a display having a flat carrier substrate. The carrier substrate can be understood herein as a backplane or carrier surface, which provides a mechanically stable holding function and, in addition, provides electrical connections for the μ-LEDs. Possible materials for the carrier substrate can be insulating compounds or semiconductors, such as silicon or III-V semiconductor materials. According to one example, the carrier substrate is designed to be flexible or bendable.

[0127] At least one μ-LED device is disposed on a carrier substrate and is designed to emit light transversely to the plane of the carrier substrate in a direction opposite to the carrier substrate. Here, the at least one μ-LED can be attached to the carrier substrate, for example, by adhesive bonding, fusion bonding, or as a result of an epitaxial layer process. The μ-LED is designed as a so-called vertical chip, wherein at least one contact is located in a spatial region of the μ-LED away from the carrier substrate. Therefore, at least one μ-LED has an electrical contact on its upper side opposite to the carrier substrate. The upper side here should be understood to refer to a region of the side or outer surface of the μ-LED, wherein at least a portion of the upper side is oriented parallel to the plane of the carrier substrate.

[0128] Some design schemes for vertical μ-LEDs are presented here. These include, but are not limited to, the aforementioned paired rods with converter material arranged between them, vertically or horizontally oriented μ pillars, or antenna structures. Quantum well mixing can be provided to provide charge carriers from one or more edges of the active layer.

[0129] The electrical contacts can be, for example, metal or a generally conductive surface. The concept here is that this surface should contact a layer covering it relative to the plane of the carrier substrate. The pixel element has a flat contact layer on the top surface of the transmitter chip that is at least partially conductive. It is electrically connected to the electrical contacts of the transmitter chip.

[0130] In other words, for example, an additional layer can be fabricated on at least one μ-LED, which is in direct contact with the electrical contacts of at least one μ-LED. For example, this flat contact layer can be extended in one piece over multiple μ-LEDs and pixel elements. According to one example, the contact layer forms a common cathode or a common anode. According to one instance, the thickness of the contact layer is between 80 and 150 nm.

[0131] The flat contact layer is designed to be at least partially transparent to light emitted by at least one μ-LED. This means that light emitted by at least one μ-LED can pass through the contact layer at least partially. For example, known ITO materials can be used for this. Printed conductors are provided on the contact layer, which are conductive and flatly connected to the contact layer. The conductivity of the printed conductors is greater than that of the contact layer. The printed conductors can be designed, for example, as planar or flat surfaces or strips.

[0132] The material of the printed conductors is chosen to have better conductivity than, for example, ITO. In other words, the printed conductors should bridge the less conductive areas of the contact layer, thereby achieving an overall reduction in resistance via the contact layer, also known as improved lateral conductivity. For this purpose, the printed conductors should be connected to the contact layer at least at two points far apart from each other, so as to reduce the total resistance of the arrangement of the printed conductors and the contact layer between these two points through the increased conductivity of the printed conductors.

[0133] Printed conductors can be understood, for example, as busbars, distribution strips, or similar conductive structures. According to one example, printed conductors are designed as part of the contact layer itself as a space-constrained structure. This could mean, for example, providing areas within the contact layer with different structures or regions with altered combinations of materials or substances that improve conductivity. Materials for printed conductors can include, for example, silver, aluminum, gold, chromium, or nickel-vanadium.

[0134] According to one example, a contact layer may be arranged in an intermediate space between two adjacently arranged μ-LEDs. In other words, the structure and arrangement of the μ-LEDs between the individual μ-LEDs result in an intermediate space that can be advantageously configured to receive the contact layer. According to one example, electrical contacts of at least one μ-LED are arranged on the side of at least one μ-LED. In other words, the contact layer contacts the contacts of at least one μ-LED, for example, in a region of the intermediate space between two μ-LEDs.

[0135] In one aspect, printed conductors are arranged outside the main emission region of the μ-LEDs between two adjacent μ-LEDs disposed on a carrier substrate. It is important to consider that, due to their structure, the μ-LEDs emit most of their light transversely to and away from the carrier substrate plane. It may be desirable that a large amount of light is emitted as vertically as possible, i.e., with a conical or ideal Lambertian emission characteristic.

[0136] This necessitates suppressing unwanted light components outside the advantageous main emission area to avoid crosstalk, interfering with each other, and unwanted reflections. Therefore, most of the opaque printed conductors should not obscure or restrict the main emission area, and are thus advantageously positioned outside the main emission area or radiation channel. This can be achieved, in particular, by creating a suitable spatial region in the intermediate space between the μ-LEDs.

[0137] In one aspect, the printed conductors are designed to absorb and / or reflect light components emitted by at least one μ-LED outside the main emission region in order to perform beam shaping on at least one μ-LED. In other words, this means that in addition to the function of increasing conductivity, the printed conductors can also be used to absorb or reflect the light emitted by the μ-LED.

[0138] Therefore, printed conductors are intentionally placed in the area surrounding the main emitting region of at least one μ-LED to achieve a beamforming effect. For example, the printed conductors can be designed as a flat conductor structure extending in a loop around the area of ​​at least one μ-LED. When three μ-LEDs are used as sub-pixels (each forming a pixel), the conductor structure can extend around each pixel. According to another example, beamforming can be achieved by providing an opening in the printed conductor through which the emitted light can pass.

[0139] To achieve improved absorption of unwanted light components outside the main emitting region of a μ-LED, according to one aspect, the printed circuit board has a light-absorbing layer on its side facing the carrier substrate. According to one example, this could be a separate layer of absorbing material, but it could also be achieved through surface structures on the printed circuit board.

[0140] In one aspect, printed conductors extend over multiple μ-LEDs. Additionally, recesses are provided on the printed conductors in the respective main emitting regions of the μ-LEDs to allow light emitted by the respective μ-LED to pass through. These recesses can be, for example, openings, holes, gaps, or similar structures through which light emitted by the μ-LEDs can pass. In other words, the printed conductors can be configured as a continuous layer or as coherent elements. Among other things, this can advantageously allow for more complex shapes of openings or cutouts used for beam shaping.

[0141] In one aspect, the printed wires are applied to the side of the contact layer facing away from the carrier substrate. In other words, the printed wires are located above the contact layer, for example, as elements subsequently applied sequentially during the manufacturing process. In the other aspect, the printed wires are applied to the side of the contact layer facing the carrier substrate. In other words, this means that, viewed from the carrier substrate, the printed wires are located below the ITO contact layer.

[0142] On the other hand, printed conductors are applied to a carrier substrate. The adjacent arrangement of several μ-LEDs creates corresponding intermediate spaces. These intermediate spaces can reach the level or height of the carrier substrate itself. It is worth noting that the planarization layer is not continuous but is cut out in the area of ​​this intermediate space. Currently, the technological advantage lies in the ability to directly produce printed conductors on the carrier substrate and then vertically apply the contact layer thereon.

[0143] According to one aspect, at least one μ-LED device is disposed within a cavity of a carrier substrate, and printed conductors are disposed outside the cavity. Thus, the carrier substrate can be understood, for example, as a structured surface that is not designed to be always flat or planar, but rather has grooves. The μ-LED is placed in these grooves or recesses, so that the sidewalls of these grooves can be used as reflective surfaces for beam shaping. To avoid shading and absorption, one or more printed conductors are disposed outside the grooves.

[0144] According to one aspect, a connection element for electrically connecting a contact layer to a port element on a carrier substrate is provided on the pixel element. Here, it can be seen that the contact layer disposed above the carrier substrate forms, for example, a common anode or a common cathode, and therefore must be electrically connected. This can be achieved by fixing one end of the port element to the contact layer in a conductive manner, while the other end is fixed to a conductive structure of the carrier substrate. The port element can, for example, be disposed on the outer edge region of one or more pixel elements.

[0145] On the other hand, the fabrication of one or more pixel elements for a display is involved. For this purpose, a flat carrier substrate is provided in the first step, and a large number of light-emitting components are fabricated thereon. These components can be fabricated using conventional methods by applying, doping, and structuring various semiconductor layers. Typical material systems are based on GaN, including GaN, GaNP, GaNInP, GaNAIP, etc. Multiple light-emitting components have a main radiation direction away from the carrier substrate. Additionally, electrical contacts are provided on the surfaces of the multiple light-emitting components away from the carrier substrate. Furthermore, a planar contact layer, at least partially conductive, is applied, electrically connected to the electrical contacts of the multiple light-emitting components. On one hand, the contact layer can extend on the carrier substrate and cover the components. The contact layer is designed to be at least partially transparent to light emitted by the semiconductor components during operation. At least one printed conductor is disposed on the contact layer and electrically connected to and planarly connected to the contact layer. Here, the conductivity of the printed conductor is greater than the conductivity of the contact layer. Attached Figure Description

[0146] The following sections use various design schemes and examples to illustrate some of the aspects mentioned above and summarized in more detail.

[0147] Figure 1 The diagram illustrates some requirements for a so-called μ display or microdisplay device in terms of various dimensions of field of view and pixel spacing in a μ display; Figure 2 A diagram showing the spatial distribution of rod and cone cells in the human eye; Figure 3 A diagram showing the perceptual abilities of the human eye with assigned projection areas; Figure 4A graph showing the sensitivity of rod and cone cells at different wavelengths is presented; Figure 5 The diagram illustrates some requirements for microdisplays of various sizes in terms of the field of view and collimation of pixels in a μ display; Figure 6 An exemplary design of a pixel array is shown to illustrate... Figure 1 and Figure 5 The parameters represented in the text; Figure 7 A graph showing the required number of pixels depends on the number of fields of view for a given resolution; Figure 8 The top view used to illustrate some aspects shows a portion of a microdisplay with multiple μ-LEDs and a transparent contact layer designed as a common cathode; Figure 9 and Figure 10 The illustration shows some pixel elements with μ-LEDs, a contact layer, and two printed wires, based on some aspects of the proposed design; Figure 11 A pixel element with multiple conductor structures for anode and cathode with μ-LEDs is shown in a top view, as well as a portion of a μ-LED with beam-shaping elements; Figure 12 Another supplementary design scheme for the implementation of the previous figure is shown; Figure 13 A top view of a portion of a μ display with pixel elements, based on some aspects of the proposed design, is shown, wherein the pixel elements have a contact layer and a recess in the region of the μ-LED; Figure 14 It shows according to Figure 13 A vertical cross-sectional view of a pixel element having μ-LEDs, printed wires, and an emission area, to illustrate another perspective; Figure 15 An alternative embodiment for limiting the reflective region of a μ-LED is shown; Figure 16 A vertical cross-sectional view through a pixel element with three μ-LEDs and a transparent overlay electrode is shown, according to some aspects. Figure 17 A vertical cross-sectional view, rotated 90 degrees from the previous figure, is shown, passing through a pixel element with printed conductors, according to some aspects of the proposed design. Figure 18 An embodiment of a pixel in a vertical cross-sectional view is shown, the pixel having printed conductors beneath a stepped contact layer; Figure 19A pixel with printed conductors beneath a planar contact layer is shown in a vertical cross-sectional view. Figure 20 An embodiment with two pixel elements is shown in a vertical cross-sectional view, the pixel elements having printed lines on a carrier substrate; Figure 21 A vertical cross-sectional view shows a pixel element with three μ-LEDs arranged in a planar manner in a cavity of a carrier substrate. Figure 22 A pixel with three μ-LEDs is shown in a vertical cross-sectional view. The μ-LEDs are arranged in a cavity of a carrier substrate with raised intermediate space walls. Figure 23 This illustrates a supplementary design for the pixels in the previous image, where the remaining space within the cavity is filled with converter material; Figures 24 to 26 Different arrangements of μ-LEDs on a carrier substrate, based on some aspects of the proposed principle, are shown, as well as the reflection behavior of the emitted light on the sidewalls of the cavity. Detailed Implementation

[0148] Augmented reality is largely created by a dedicated display that overlays images onto reality. This display can be placed directly in the user's line of sight, i.e., directly in front of them. Alternatively, beam deflection elements can be used to direct light from the display toward the user's eyes.

[0149] In both cases, a display can be implemented, and the user can wear glasses or other visual augmentation devices as part of the device. Google's™ Glasses is an example of such a visual augmentation device, allowing users to overlay certain information about objects in the real world. With Google™ Glasses, the information is displayed on a small screen in front of the glasses. In this respect, the appearance of this add-on device is a key feature of the glasses, combining technological functionality with the design aspects of wearing glasses. Simultaneously, users need glasses that don't have such bulky or easily damaged devices to provide augmented reality functionality. Therefore, one concept is that the glasses themselves become a display or at least one screen, with information projected onto or into a projector.

[0150] In this type of situation, the user's field of view is limited to the size of the glasses. Therefore, the area on which augmented reality can be projected is approximately the size of the glasses lenses. The same but different information can be projected onto or onto both lenses of a pair of glasses.

[0151] In other words, the image experienced by a user while wearing augmented reality glasses should have a resolution that creates a seamless impression, so that the user doesn't perceive augmented reality as a pixelated object or a low-resolution element. Straight bevels, arrows, or similar elements appear as staircase-like outlines at low resolutions, which is distracting for the user.

[0152] To achieve an ideal visual impression, two display parameters are considered important, as they influence the visual impression for a given or known human eye. One is the pixel size itself, the geometry and dimensions of a single pixel, or the area of ​​three subpixels representing that pixel. The second parameter is the pixel pitch, the distance between two adjacent pixels or subpixels, which varies depending on the context. Sometimes, pixel pitch is also referred to as the space between pixels. Larger pixel gaps can be detected by the user and perceived as gaps between pixels, potentially leading to what is known as the "flying screen effect." Therefore, the gap should not exceed a certain limit.

[0153] The maximum angular resolution of the human eye is typically between 0.02 and 0.03 arcminutes, roughly equivalent to 1.2 to 1.8 arcminutes per line. This results in a pixel pitch of 0.6-0.9 arcminutes. Some current mobile phone displays have approximately 400 pixels per inch, resulting in a viewing angle of approximately 2.9° at a distance of 25 cm from the user's eyes, or approximately 70 pixels per degree. Therefore, the distance between two pixels in such a display is within the range of maximum angular resolution. Furthermore, the pixel size itself is approximately 56 μm.

[0154] Figure 1 The pixel spacing is shown, that is, the distance between two adjacent pixels that depends on the field of view. In this respect, the field of view is the extension of the observable world seen at a given moment. This is because human vision is defined as the angle of view in degrees during a stable fixation of the eye.

[0155] In particular, the forward horizontal curvature of the binocular visual field is slightly higher than 210°, while the vertical curvature of the human visual field is approximately 135°. However, the range of visual ability is not uniform across the entire visual field and may vary from person to person.

[0156] Human binocular vision covers approximately 114° horizontally (peripheral vision) and approximately 90° vertically. The remaining degrees on both sides do not constitute binocular vision, but can be considered part of the field of view.

[0157] Furthermore, color vision and the ability to perceive shape and motion further limit the horizontal and vertical fields of vision. The rods and cones responsible for color vision are unevenly distributed.

[0158] This viewpoint is Figures 2 to 4This was explained in more detail. In the central visual domain, that is, directly in front of the eyes, as required by augmented reality applications, and partly in the automotive field, the eye's sensitivity is very high in terms of spatial resolution and color perception.

[0159] Figure 2 The spatial density of cones and rods per square millimeter is shown, which is related to the angle of the central concave region. Figure 3 The wavelength-dependent color sensitivity of cones and rods is described. In the central region of the fovea, increased cone density (L, S, and M) leads to better color perception. Sensitivity begins to decrease at a distance of approximately 25° around the fovea, as the density of visual cells decreases. Near the edges, color perception decreases further, but contrast vision through rods remains over a wider angular range. Overall, this creates a radially symmetrical visual pattern for the eye, rather than a Cartesian one. Therefore, high resolution of all primary colors is necessary, especially at the center. At the edges, working with an emitter adapted to the spectral sensitivity of rods may suffice (maximum sensitivity 498 nm, see...). Figure 4 And the sensitivity of the eyes).

[0160] Figure 3 The graph of angular resolution A relative to the angular deviation α from the optical axis of the eye illustrates the different perceptual abilities of the human eye. It can be seen that the highest angular resolution A exists within the interval of + / - 2.5° angular deviation α, where the fovea 7 is arranged on the retina 19 with a diameter of 1.5 mm. Furthermore, the location of the blind spot 22 on the retina 19 is plotted, which appears in the region of the optic disc 23, with an angular deviation α of approximately 15°.

[0161] The eye can compensate for this non-constant density, and it can also compensate for so-called blind spots through minute eye movements. This change in the direction or focus of the gaze can be counteracted through appropriate optical systems and eye tracking.

[0162] In addition, even when wearing glasses, the field of vision is further limited; for example, the field of vision of each lens can be within approximately 80°.

[0163] Figure 1The pixel pitch on the Y-axis, measured in μm, defines the distance between two adjacent pixels. Different curves, C1 to C7, define the diagonal dimensions of the corresponding displays, ranging from 5mm to approximately 35mm. For example, curve C1 corresponds to a display with a diagonal dimension of 5mm, meaning a side length of approximately 2.25mm. For a field of view of approximately 80°, the pixel pitch of a display with a 5mm diagonal dimension is within the range of 1μm. For larger displays, such as those using curve C7 and a 35mm diagonal dimension, the same field of view can be achieved with a pixel pitch of approximately 5μm.

[0164] However, Figure 1 The curves in the diagram illustrate that a larger field of view is preferred for augmented reality applications, while very high pixel density and small pixel pitch are required to avoid the well-known screen-flying effect. We can now calculate the pixel size for a given number of pixels, a given field of view, and a given diagonal size for a μ display.

[0165] Equation 1 shows the relationship between pixel size D, pixel pitch pp, number of pixels N, and display edge length d. The distance r between two adjacent pixels, calculated from their respective centers, is given by the following equation.

[0166] r = d / 2 + pp + d / 2.

[0167] D = d / N-pp (1)

[0168] N = d / (D + pp)

[0169] Assuming the distance between the monitor (e.g., glasses) and the eye is 2.54 cm (1 inch), then for the roughly estimated 1 arcminute angular resolution above, the distance r between two adjacent pixels is...

[0170] r = tan(1 / 60°) × 30mm

[0171] r = 8.7μm

[0172] Therefore, pixel size is less than 10 μm, especially when a certain space is required between two different pixels. Using the distance r between two pixels and a display with a size of 15 mm × 10 mm, 1720 × 1150 pixels can be arranged on the surface.

[0173] Figure 6An arrangement with a carrier 21 is shown, on which a plurality of pixels 20 and 20a to 20c are arranged. Pixels 20 arranged adjacent to each other have a pixel pitch pp, while pixels 20a to 20c are placed on the carrier 21 with a larger pixel pitch pp. The distance between two pixels is given by the sum of the pixel pitch and half the size of each adjacent pixel. Each pixel 20 is configured such that its illumination characteristics, or emission vector 22, are substantially perpendicular to the emission surface of the corresponding LED.

[0174] The angle between the vertical axis on the emitting surface of the LED and the beam vector is defined as the collimation angle. In the example of emission vector 22, the collimation angle of LED 20 is approximately zero. LED 20 emits collinear light and does not expand significantly.

[0175] Conversely, the collimation angle of the emission vector 23 of LED pixels 20a to 20c is very large, and is in the range of approximately 45°. As a result, a portion of the light emitted by LED 20a overlaps with the emission of the adjacent LED 20b.

[0176] The emission of LEDs 20a to 20c partially overlaps, resulting in the superposition of their respective light emissions. If the LEDs emit different colors of light, the result will be a mixture or combination of colors. A similar effect occurs between high-contrast areas, i.e., when LED 20a is dark while LED 20b emits some kind of light. Due to the overlap, the contrast is reduced, and the information at each individual location corresponding to the pixel position is also reduced.

[0177] For displays with a small distance from the user's eyes, such as those mentioned above, a large collimation angle can be quite annoying due to the aforementioned effects and other drawbacks. Users can perceive a large collimation angle and may experience a slight difference in the color of depicted objects, a blurriness, or reduced contrast.

[0178] in this regard, Figure 5 This illustrates the collimation angle in degrees relative to the field of view in degrees, which is independent of a specific display size. For smaller display sizes, such as those in curve C1 (approximately 5 mm diagonally), the collimation angle increases significantly depending on the field of view.

[0179] As monitor sizes increase, the requirements for collimation change dramatically. Therefore, even with large monitor geometries, as shown by curve C7, the collimation angle reaches approximately 10° within a 100° field of view. In other words, the collimation requirements increase for larger monitors and larger fields of view. In such monitors, the light emitted from the pixels must be highly collimated to avoid or reduce the aforementioned effects. Therefore, when providing users with monitors that offer large fields of view, even if the monitor's geometry is relatively large, robust collimation capabilities are necessary.

[0180] Based on the above charts and equations, it can be deduced that as the geometry and field of view of a display increase, the requirements regarding pixel pitch and collimation become increasingly challenging. As Equation 1 shows, the size of a display increases dramatically with the number of pixels. Conversely, a large field of view requires a large number of pixels to achieve sufficient resolution and avoid screen flickering or other interference effects.

[0181] Figure 7 The diagram illustrates the number of pixels required to achieve an angular resolution of 1.3 armes. For a field of view of approximately 80°, the number of pixels exceeds 5 million. It can be quickly estimated that the pixel size for QHD resolution is far less than 10μm, even with a display size of 15mm × 10mm. In total, an augmented reality display with resolutions in the HD range (i.e., 1080p) requires a total of 2,073,600 pixels. This would cover a field of view of approximately 50°. The number of pixels arranged in a 10 × 10mm display with a pixel spacing of 1μm would result in a pixel size of approximately 4μm.

[0182] The above considerations make it clear that the challenges in terms of resolution, collimation, and field of view suitable for augmented reality applications are considerable. Therefore, the technical implementation of such displays also places very high demands on them.

[0183] Traditionally used technologies were designed for manufacturing displays with LED edge lengths in the range of 100 μm or even longer. However, they cannot automatically scale to the 70 μm and below dimensions required here. Pixel sizes of a few μm and distances of a few μm or even smaller, closer to the order of magnitude of the generated light wavelength, require new processing technologies.

[0184] Furthermore, new challenges have emerged in light collimation and guidance. For example, optical lenses that can be easily structured into larger LEDs and calculated using classical optics cannot be directly scaled down to such small sizes without using Maxwell's equations. In addition, it is nearly impossible to manufacture small lenses without large errors or deviations. In some variants, quantum effects affect the behavior of pixels of these sizes and must be taken into account. Tolerance requirements in the production or transmission techniques of pixels on auxiliary carriers or matrix structures are becoming increasingly stringent. Pixels must also be contactable and individually controllable. Conventional circuitry has space requirements that, in some cases, exceed the pixel area, creating placement and space issues.

[0185] Therefore, new designs for controlling and accessing pixels of this size may be entirely different from traditional technologies. Finally, a key focus is on the power consumption of such displays and controls. Low power consumption is particularly desirable for mobile applications.

[0186] In summary, many designs suitable for larger pixel sizes require extensive modifications before successful scaling down. While a design suitable for producing 200 μm LEDs can be easily scaled up to 2000 μm LEDs, scaling down to 20 μm is much more difficult. Many documents and literature disclosing such designs do not account for the various effects and increased requirements of extremely small sizes, and therefore are not directly applicable to or limited to pixel sizes significantly larger than 70 μm.

[0187] The following sections present various aspects of the structure and fabrication of μ-LED semiconductors, including processing, optical coupling output and light guidance, display, and control. These are suitable for designing displays with pixel sizes of 70 μm and below. Some designs are specifically designed for the production, optical coupling output, and control of μ-LEDs with edge lengths less than 20 μm, particularly less than 10 μm. It goes without saying that the designs presented here regarding these aspects can and should be combined with each other. For example, this relates to the design of μ-LEDs with designs for producing coupled output light. Specifically, μ-LEDs implemented, for example, by methods to avoid edge defects or by current conduction or current contraction, can provide optical coupling output structures based on photonic crystal structures. Special control can also be implemented for displays with variable pixel sizes. Light guidance with piezoelectric mirrors can be implemented in μ-LED displays based on slot antennas or conventional monolithic pixel matrices.

[0188] In some of the design options and aspects described below, additional examples of various design options or combinations of their aspects are indicated. These are intended to clearly show that those skilled in the art can combine the aspects, design options, or parts thereof with each other. Some applications require specially modified designs, while others have lower technical requirements. Automotive applications and displays, for example, typically have larger pixel edge lengths due to the greater distance from the user. In particular, there are classic pixel applications or virtual reality applications, in addition to augmented reality applications. In the context of this disclosure, this is also clearly desirable for realizing μ-LED displays with pixel edge lengths below 70 μm.

[0189] Figure 8 A portion of a miniature display with several μ-LEDs and a transparent contact layer designed as a common cathode is shown in a top view.

[0190] exist Figure 9In this configuration, numerous individual contacts are combined within a common contact layer 16. This contact layer 16 is designed to be flat, at least partially conductive, and serves as a common cathode, contacting the upper side of the μ-LED 18 and the electrical contact 20 on its upper side. Due to the partially transparent design of the contact layer 16, light emitted by the μ-LED 18 can pass through the contact layer 16 at least partially. Accordingly, on one side, there is an arrangement or contact between the vertical μ-LED and the transparent and electrically conductive overlay.

[0191] As can be seen, due to the possibility of contacting the μ-LED 18 on their respective upper sides via contacts 20, the previously necessary conductor structure 14 for the cathode can be eliminated, thus allowing for more space to be used. In the example shown here, connecting conductors 20 are provided for the contact layer 16, serving as electrical contacts for the contact layer 16. Because of the common contact layer 16, separate individual contacts for each individual μ-LED 18 can be eliminated, and instead, this can be achieved using the easily fabricated common contact layer 16.

[0192] Figure 10 A variant of the optical pixel element 10 further developed according to the present invention is shown, the basic structure of which corresponds to that according to Figure 9 The pixel element, wherein a common contact layer 16, together with a connecting conductor 20, forms a common cathode for forming the μ-LED 18 below. In the example shown here, two parallel printed conductors 26 are provided on the contact layer 16.

[0193] These printed conductors 26 have a higher conductivity than the material of the contact layer 16, thereby reducing the overall resistance of the overall arrangement of the contact layer 16 and the printed conductors 26 compared to the contact layer 16. In other words, the printed conductors 26 bridge areas of the poorly conductive contact layer 16. In principle, the printed conductors 26 can be designed in various shapes, such as straight, curved, zigzag, etc., and their widths and thicknesses can vary.

[0194] The printed conductors 26 can also be designed as a combination of numerous individual fine conductors resembling stranded wires. It can be seen that the printed conductors 26 are arranged outside the main radiating region 28 (see...). Figure 11 and Figure 12 Therefore, they do not block or obstruct light from emitting from pixel element 10 or from μ-LED 18.

[0195] Figure 11 The structure of pixel element 10 is shown, wherein conductor structure 12 for the anode and conductor structure 14 for the cathode are arranged parallel to each other on a carrier substrate 22. Figure 8In contrast to the known pixel element 10 with horizontal μ-LEDs (whose lower contacts are in direct contact with lines 14 and 12), here the upper contacts, i.e., those facing away from the carrier substrate, are the corresponding μ-LEDs 18 connected to the cathode conductor structure 14 via partially transparent contacts. Additionally, a beam shaping element 32 is provided for each μ-LED 18. This beam shaping element 32 can also be understood as a so-called coupled output structure. Therefore, this illustration is similar to other figures and other embodiments. Contact can also be implemented in a similar manner.

[0196] Due to the geometry of the beam-forming element, such as the structure surrounding the μ-LED 18, an opening of a certain size is necessary for the desired shape of emitted light. This size can, in turn, mean that undesirable spatial overlap between the cathode conductor structure 14 and the beam-forming element 32 may occur in the overlap region 30. This is particularly possible because both the conductor structure 12 for the anode and the conductor structure 14 for the cathode must be held on the carrier substrate 22 simultaneously.

[0197] It should be noted that the conductor structure 12 for the anode and the conductor structure 14 for the cathode can also be arranged in reverse order. This means that the electrical contacts 20 of the μ-LED 18 can be designed as either the cathode or anode on the upper side. Accordingly, the conductor structures 12 and 14 are designed as either anode conductor structures or cathode conductor structures.

[0198] Figure 12 Showing from Figure 10 The pixel element 10 has a basic structure with two parallel printed conductors 26. The vertical μ-LED is in contact with the contact track 12 on one side and with the conductive transparent layer (not shown) on the other. By eliminating the conductor structure 14, more space is available for the beam-forming element 32, thus preventing unwanted overlap or electrical contact.

[0199] exist Figure 13 Another embodiment of the optical pixel element 10 is shown. Although the basic structure of the pixel element having μ-LED 18, conductor structure 12 for the anode, and carrier substrate 22 is similar... Figure 9 The example shown corresponds, but here the printed conductors 26 are designed as a continuous surface over the plurality of μ-LEDs 18. In the regions of the respective main emitting regions 28, recesses 34 are provided, which are intended for beam shaping. In other words, these recesses 34 are used to guide the light emitted by the respective μ-LEDs 18. In this way, a separate beam shaping element 32 (e.g., see the figure) can be omitted, as that function can now be taken over by the recesses 34.

[0200] exist Figure 14The beam shaping aspect of the light emitted by the μ-LED 18 is explained in more detail. The μ-LED 18, arranged on a carrier substrate 22 (not shown), can be seen in the vertical cross-sectional view. It emits light transversely to the carrier substrate plane 36 in a direction away from the carrier substrate 22. In the example shown here, the μ-LED has a cardioid propagation characteristic. However, it is desirable that the light is emitted only in the main emitting region 28 of the μ-LED 18. To shield the unwanted light component, one or more printed conductors 26 are used here. These can be designed to be reflective or absorptive on their underside. In another aspect, the printed conductors include a light-absorbing layer 38 on their underside. This layer can prevent or reduce additional unwanted reflections or crosstalk between adjacent μ-LEDs 18.

[0201] exist Figure 15 Alternative embodiments are shown in the figure. In this case, it is proposed that, as Figure 15 As shown, the transparent conductive layer 38a partially overlaps the μ-LED and is thus firmly attached to the contacts located on it. Meanwhile, reflective printed wires enable beam shaping.

[0202] exist Figure 16 The image shows a vertical cross-section passing through the pixel element 10 in the longitudinal direction. Three μ-LEDs 18 can be seen, connected to the carrier substrate and corresponding conductor structures 12 of the anode via anode contacts 40. The planarization layer 42 has a height of, for example, 2-4 μm. Due to the overall planar construction, the height of the μ-LEDs, including the anode contacts 40, can also be within this size range. A flat, at least partially conductive, and at least partially transparent to light contact layer 16 is provided on the top side.

[0203] Because contact layer 16 represents a common cathode or anode port, it must be electrically connected to an external port element accordingly. For this purpose, connection element 44 is designed to provide an electrical connection between contact layer 16 and the port element of carrier substrate 22. In this example, it is positioned at the edge of pixel element 10. The port element of carrier substrate 22 can be, for example, a suitable conductive surface or conductor structure that allows, for example, connection to external components or supply lines of pixel element 10.

[0204] exist Figure 17 In, it is shown Figure 16 The pixel element 10 is shown in this view, rotated 90°. Printed conductors 26 can also be seen here, arranged in the intermediate space between the two emitter chips 18, thus placing them within the main radiating region 28 of the respective μ-LED 18 (see, for example, [link to relevant documentation]). Figure 14 The outside of ). Here and below Figures 18 to 22 In the middle, port element 44 is located at the edge of pixel element 10.

[0205] Figure 18 and Figure 19 An example of how printed conductors 26 are arranged on contact layer 16 is shown. Figure 18 In this configuration, the printed conductor 26 is partially embedded in the planarization layer 42, and is also disposed on the underside of the contact layer 16. In this case, the contact layer 16 is treated to have stepped protrusions on the printed conductor 26.

[0206] Figure 19 The embodiment of pixel element 10 in the figure basically corresponds to Figure 18 The structure of the pixel element 10 includes a contact layer 16 designed to be coherently flat, and printed conductors 26 are disposed on the underside of the contact layer 16. In this case, the printed conductors 26 extend into the area of ​​the planarization layer 42.

[0207] exist Figure 20 In this embodiment, the planarization layer 42 is interrupted in the region between two adjacent transmitter chips 18. This provides the possibility of directly placing the printed conductors 26 on the carrier substrate 22. The contact layer 16 is therefore positioned above it. This implementation variant, for example, makes it easier to provide the printed conductors 26 that have already been fabricated along with the carrier substrate 22.

[0208] Figure 21 and Figure 22 Examples of the arrangement of μ-LEDs 18 within cavities 46 of pixel elements 10 or carrier substrate 22 are shown. Alternatively, protrusions may be provided. The latter design is similar to the shapes shown in the other figures.

[0209] Figure 23 A supplementary design scheme for the pixel in the above figure is shown, wherein the remaining space within the cavity is filled with converter materials 35r and 35, respectively. The converter material extends all the way to the cover electrode, but it can also be positioned above the cover electrode to also convert upwardly radiated light. In this way, the converter material can also be used to form a flat surface. In one embodiment, the converter material has quantum dots, which are filled into the cavity in the form of powder or emulsion. In some cases, the quantum dots can be made significantly smaller than certain conventional powder forms of inorganic dyes, so they are also suitable for μ-LEDs.

[0210] Alternatively, printed conductors 26 may be provided in the bulge 48 between the two cavities 46. The arrangement of the μ-LED 18 in the cavities 46 is particularly advantageous in terms of emission characteristics, because light emitted, especially in the lateral direction, can be reflected on the sides of the bulge 48 of the cavities.

[0211] exist Figure 24In this process, the sides of the protrusion 48 are made smooth, such that light emitted from the μ-LED 18 to the sides is reflected once and advantageously deflected in a direction away from the carrier substrate 22. Figure 25 In the center, the material of the sides of the ridge 48 is designed to cause multiple reflections of incident light in different directions. Figure 24 and Figure 25 In the middle, the protrusions 48 are located on the edge of the pixel element 10 or on the edge of the device composed of multiple μ-LEDs 18.

[0212] Figure 26 An example is shown in which a bump 48 is provided between two adjacent μ-LEDs 18. The optical separation achieved by the shading effect of the bump 48 on the individual μ-LEDs 18 within the pixel element 10 can, for example, avoid crosstalk or cross-interference, and thus also improve the contrast of the display.

[0213] In the following sections, various devices and apparatuses, as well as methods for their manufacture, processing, and operation, are again listed as examples. The following items illustrate aspects and implementations of the proposed principles and designs that can be combined in various ways. Such combinations are not limited to those given below: 231. A pixel for generating image points of a display, having: - A μ-LED device according to any of the foregoing items, particularly according to any one of items 221 to 229, Among them, a printed wire is provided on the second contact layer that forms the contact layer. The printed wire is conductive and flatly connected to the contact layer. The conductivity of the printed conductors is greater than that of the contact layer.

[0214] 232. A pixel for generating image points of a display, having

[0215] - A flat carrier substrate; - At least one μ-LED disposed on a carrier substrate; In this embodiment, at least one μ-LED is designed to emit light transversely to the plane of the carrier substrate in a direction away from the carrier substrate; At least one μ-LED has an electrical contact on its upper side facing away from the carrier substrate; The pixel on the upper side of at least one μ-LED has a flat contact layer that is at least partially conductive and is electrically connected to an electrical contact of at least one μ-LED. The contact layer for light emitted by at least one μ-LED is designed to be at least partially transparent; The contact layer has printed wires that are electrically and planar connected to the contact layer ground.

[0216] The conductivity of the printed conductors is greater than that of the contact layer.

[0217] 233. The pixel according to item 231 or 232, wherein printed wires are arranged between two μ-LEDs, the two μ-LEDs being arranged adjacently on a carrier substrate outside the main emission area.

[0218] 234. The pixel according to item 231 or 232, wherein the printed wires are designed to absorb and / or reflect light components outside the main emission region for beam shaping of at least one μ-LED.

[0219] 235. The pixel according to any one of the preceding items, wherein the printed conductor has a light-absorbing layer on its side facing the carrier substrate.

[0220] 236. The pixel according to any one of the preceding items, wherein printed conductors extend flatly over a plurality of μ-LEDs, and recesses are provided on the printed conductors in regions of the respective main emitting regions of the μ-LEDs for the passage of light emitted by the respective μ-LEDs.

[0221] 237. The pixel according to any one of the preceding items, wherein printed wires are applied to the side of the contact layer opposite to the carrier substrate.

[0222] 238. The pixel according to any one of the preceding items, wherein printed wires are applied to the side of the contact layer facing the carrier substrate.

[0223] 239. The pixel according to item 238, wherein printed lines are applied to a carrier substrate.

[0224] 240. The pixel according to any one of the preceding items, wherein at least one μ-LED is disposed in a cavity of a carrier substrate, and printed wires are disposed outside the cavity.

[0225] 241. The pixel according to any one of the preceding items, wherein a converter material is arranged in a cavity.

[0226] 242. The pixel according to any one of the preceding items, wherein a connecting element is provided on the pixel element for electrically connecting the contact layer to an interface element of a carrier substrate.

[0227] 243. A method of manufacturing pixel elements for producing a display, comprising: - Provide a flat carrier substrate and generate multiple light-emitting components, particularly μ-LEDs, on the carrier substrate, each of which has an electrical contact on the upper side facing away from the carrier substrate; - Apply a contact layer that is at least partially conductive and flat, which is electrically connected to the electrical contacts of a plurality of light-emitting components; The contact layer for light emitted by the multiple light-emitting components is at least partially constructed to be transparent; - Printed conductors are provided on the contact layer, which are electrically and flatly connected to the contact layer; The conductivity of the printed conductors is greater than that of the contact layer.

Claims

1. A pixel for generating image points of a display, having - A flat carrier substrate; - At least one μ-LED, which is arranged on a carrier substrate; in, At least one μ-LED is designed to emit light transversely to the plane of the substrate in a direction away from the substrate. At least one μ-LED has an electrical contact on its upper side facing away from the carrier substrate; The pixel on the upper side of at least one μ-LED has a flat contact layer that is at least partially conductive and is electrically connected to an electrical contact of at least one μ-LED. The contact layer for light emitted by at least one μ-LED is designed to be at least partially transparent; The contact layer has printed wires that are electrically and planar connected to the contact layer ground. The conductivity of the printed conductors is greater than that of the contact layer.

2. The pixel according to claim 1, wherein, Printed wires are arranged between two μ-LEDs, which are arranged adjacent to each other on the carrier substrate outside the main emission area.

3. The pixel according to claim 1 or 2, wherein, The printed conductors are designed to absorb and / or reflect light components outside the main emission area for beam shaping of at least one μ-LED.

4. The pixel according to claim 1, wherein, The printed conductor has a light-absorbing layer on the side facing the carrier substrate.

5. The pixel according to claim 1, wherein, Printed conductors extend flatly over multiple μ-LEDs, and recesses are provided on the printed conductors in the regions of the respective main emitting areas of the μ-LEDs for the passage of light emitted by the respective μ-LEDs.

6. The pixel according to claim 1, wherein, Printed conductors are applied to the side of the contact layer away from the carrier substrate.

7. The pixel according to claim 1, wherein, Printed conductors are applied to the side of the contact layer facing the carrier substrate.

8. The pixel according to claim 7, wherein, Printed conductors are applied to the carrier substrate.

9. The pixel according to claim 1, wherein, At least one μ-LED is disposed in a cavity of the carrier substrate, and printed wires are disposed outside the cavity.

10. The pixel according to claim 1, wherein, Arrange the converter material in the cavity.

11. The pixel according to claim 1, wherein, A connection element is provided on the pixel element for electrically connecting the contact layer to the interface element of the carrier substrate.

12. A method of manufacturing pixel elements for producing a display, comprising: - Provide a flat carrier substrate and generate multiple light-emitting components, particularly μ-LEDs, on the carrier substrate, each of which has an electrical contact on the upper side facing away from the carrier substrate; - Apply a contact layer that is at least partially conductive and flat, which is electrically connected to the electrical contacts of a plurality of light-emitting components; The contact layer for light emitted by the multiple light-emitting components is at least partially constructed to be transparent; - A printed conductor is provided on the contact layer, which is electrically and flatly connected to the contact layer; The conductivity of the printed conductors is greater than that of the contact layer.

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