High efficiency red micro-led with local current aperture

Abstract

Micro light emitting diodes (micro-LEDs) include a current aperture for restricting current to a localized region such that carrier recombination occurs primarily in the localized region to emit photons, thereby reducing surface recombination and increasing quantum efficiency. Current confinement and localization is achieved using local breakdown of a potential barrier layer by local contact, a lightly p-doped active layer that suppresses lateral transport of carriers to surface regions, selective ion implantation, etching or oxidation of a semiconductor layer, or any combination thereof.

Description

Technical Field

[0001] This disclosure generally relates to micro light-emitting diodes (micro-LEDs). More specifically, this disclosure relates to improving the quantum efficiency of micro-LEDs, such as AlGaInP-based red micro-LEDs. Background Technology

[0002] Light-emitting diodes (LEDs) convert electrical energy into light energy and offer numerous advantages over other light sources, such as reduced size, increased durability, and enhanced efficiency. LEDs can be used as light sources in many display systems, including televisions, computer monitors, laptops, tablets, smartphones, projection systems, and wearable electronic devices. Micro-LEDs (“μLEDs”) based on III-V semiconductors have begun to be developed for various display applications due to their small size, high packaging density, high resolution, and high brightness. These III-V semiconductors include, for example, alloys of aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), aluminum gallium indium phosphide (AlGaInP), and other quaternary phosphide compositions. For example, multiple micro-LEDs emitting different colors of light (e.g., red, green, and blue) can be used to form multiple sub-pixels in a display system, such as a television or near-eye display system. Summary of the Invention

[0003] This disclosure generally relates to micro light-emitting diodes (micro-LEDs). More specifically, this disclosure relates to improving the quantum efficiency of micro-LEDs, such as AlGaInP-based red micro-LEDs. According to one aspect of the invention, a micro-LED is provided, comprising a first n-type semiconductor layer, an active region on the first n-type semiconductor layer, a first p-type semiconductor layer on the active region, a carrier barrier region on the first p-type semiconductor layer, and an electrode comprising a tapered or submicron structure in contact with the carrier barrier region and configured to apply an electric field to a local region of the carrier barrier region to induce breakdown in the local region of the carrier barrier region.

[0004] The carrier barrier region may include: a second n-type semiconductor layer on a first p-type semiconductor layer, and a second p-type semiconductor layer on the second n-type semiconductor layer, wherein the second p-type semiconductor layer, the second n-type semiconductor layer, and the first p-type semiconductor layer can form a PNP device. The PNP device and the first n-type semiconductor layer can form a thyristor. The carrier barrier region may include an n+ semiconductor layer on the first p-type semiconductor layer, the first p-type semiconductor layer may include a p+ semiconductor layer, and the n+ semiconductor layer and the first p-type semiconductor layer can form a tunnel junction. The carrier barrier region may include: a tunnel barrier layer on the first p-type semiconductor layer, and a second n-type semiconductor layer on the first p-type semiconductor layer, wherein the tunnel barrier layer may have a higher band gap than the first p-type semiconductor layer and the second n-type semiconductor layer. The carrier barrier region may include a heterojunction, a Schottky barrier, or a heterobaric barrier that causes band bending to form a tunnel contact. In some embodiments, the distance between the carrier barrier region and the active region may be less than the carrier diffusion length of the active region. The local region of the carrier barrier region can be characterized by a linear size that is less than one-third the linear size of a micro LED.

[0005] The active region may include an AlGaInP quantum well and may be configured to emit red light. The active region may include at least one of a p-doped quantum barrier layer or a p-doped quantum well layer. The p-doped quantum well layer may be characterized by an acceptor concentration of 1 × 10⁻⁶. 17 / cm 3 and 1×10 19 / cm 3 Between. In some embodiments, the conical or submicron structure may include a pointed or tapered tip extending into the carrier barrier region. The micro-LED may be characterized by a linear dimension of less than 20 μm.

[0006] According to one aspect of the present invention, a micro-LED is provided, the micro-LED including a first n-type semiconductor layer, an active region, a first p-type semiconductor layer, a current-limiting structure, and an electrode, the active region being located on the first n-type semiconductor layer and including at least one p-doped quantum well, the first p-type semiconductor layer being located on the active region, the current-limiting structure including a local current hole and configured to inject carriers into the active region through the local current hole, and the electrode being located on the local current hole of the current-limiting structure.

[0007] The current-limiting structure may include a carrier barrier layer, and the electrode may include a tapered or submicron structure in contact with the carrier barrier layer and configured to apply an electric field to a local region of the carrier barrier layer to induce breakdown in that local region, thereby forming a local current hole. The carrier barrier layer may include a second n-type semiconductor layer on a first p-type semiconductor layer, and a second p-type semiconductor layer on the second n-type semiconductor layer, wherein the second p-type semiconductor layer, the second n-type semiconductor layer, the first p-type semiconductor layer, and the first n-type semiconductor layer can form a thyristor. The carrier barrier layer may include a tunnel junction or a heterojunction. In some embodiments, the p-doped quantum well is characterized by an acceptor concentration of 1 × 10⁻⁶. 17 / cm 3 With 1×10 19 / cm 3 Between. The local current aperture can be characterized by a linear dimension less than one-third the linear dimension of the micro-LED. In some embodiments, the active region may include an AlGaInP layer and may be configured to emit red light.

[0008] The foregoing summary is not intended to highlight key or essential features of the claimed subject matter, nor is it intended to be used alone to define the scope of the claimed subject matter. The subject matter should be understood through reference to appropriate portions of the entire specification, any or all of the drawings, and each claim. The foregoing, as well as other features and examples, will be described in more detail below in the description, claims, and drawings. Attached Figure Description

[0009] The following describes illustrative embodiments in detail with reference to the accompanying drawings.

[0010] Figure 1 A simplified block diagram of an example of an artificial reality system environment including a near-eye display (NED) according to certain embodiments.

[0011] Figure 2 A stereoscopic view of an example of a near-eye display in the form of a head-mounted display (HMD) device used to implement some of the examples disclosed herein.

[0012] Figure 3 A stereoscopic view of an example of a near-eye display in the form of glasses, used to implement some of the examples disclosed herein.

[0013] Figure 4 An example of an optical see-through augmented reality system including a waveguide display, according to certain embodiments, is shown.

[0014] Figure 5A An example of a near-eye display device including a waveguide display according to certain embodiments is shown.

[0015] Figure 5B An example of a near-eye display device including a waveguide display according to certain embodiments is shown.

[0016] Figure 6 An example of an image source component in an augmented reality system according to certain embodiments is shown.

[0017] Figure 7A An example of a light-emitting diode (LED) with a vertical mezzanine structure according to certain embodiments is shown.

[0018] Figure 7B A cross-sectional view of an example of an LED having a parabolic platform structure according to certain embodiments.

[0019] Figure 8 The relationship between the light emission power of a light-emitting diode and its current density is shown.

[0020] Figure 9 The surface recombination rates of various III-V semiconductors are shown.

[0021] Figure 10A Examples of how the external quantum efficiency of different AlGaInP red micro-LEDs with different physical dimensions varies with current density are shown.

[0022] Figure 10B Examples of current-voltage (IV) curves for different AlGaInP red micro-LEDs with different physical dimensions are shown.

[0023] Figure 11A An example of micro-LED is shown.

[0024] Figure 11B Examples of micro-LEDs with improved external quantum efficiency according to certain embodiments are shown.

[0025] Figure 12 Examples of micro-LEDs with improved external quantum efficiency according to certain embodiments are shown.

[0026] Figure 13A An example of the energy band diagram of an n-doped active layer in a micro-LED is shown.

[0027] Figure 13B An example of the energy band diagram of the p-doped active layer in a micro-LED is shown.

[0028] Figure 14AAn example of the IV curve of an AlGaInP-based red micro-LED according to certain embodiments is shown.

[0029] Figure 14B Illustrations according to certain embodiments Figure 14A The external quantum efficiency of the example AlGaInP-based red micro-LED shown varies with the injection current.

[0030] Figure 15A Illustrations according to certain embodiments Figure 14A The output power of the emitted light of the example AlGaInP-based red micro-LED shown varies with the injected current.

[0031] Figure 15B Illustrations according to certain embodiments Figure 14A The normalized output spectrum of the emitted light of the example AlGaInP-based red micro-LED shown is displayed at different current levels.

[0032] Figure 16 Includes illustrations according to certain embodiments Figure 14A The image shown is an example of the luminescent pattern of a red micro-LED based on AlGaInP.

[0033] Figure 17A An example of a method for die-to-wafer bonding of an LED array according to certain embodiments is shown.

[0034] Figure 17B An example of a wafer-to-wafer bonding method for an LED array according to certain embodiments is shown.

[0035] Figures 18A to 18D An example of a method for hybrid bonding of an LED array according to certain embodiments is shown.

[0036] Figure 19 An example of an LED array having multiple auxiliary optical components fabricated thereon is shown according to certain embodiments.

[0037] Figure 20 A simplified block diagram of the electronic system in an example of a near-eye display according to certain embodiments.

[0038] The accompanying drawings depict embodiments of the present disclosure for illustrative purposes only. Those skilled in the art will readily recognize from the following description that alternative embodiments of the illustrated structures and methods may be employed without departing from the principles of the present disclosure or the claimed advantages.

[0039] In the accompanying drawings, similar parts and / or features may have the same reference numerals. Furthermore, various parts of the same type can be distinguished by following the reference numeral with a ligature and a second numeral to differentiate similar parts. If only the first reference numeral is used in the specification, the description applies to any of the similar parts having the same first reference numeral, regardless of the second reference numeral. Detailed Implementation

[0040] This disclosure generally relates to micro light-emitting diodes (micro-LEDs). More specifically, but not limited to, this document discloses techniques for improving the efficiency of micro-LEDs, such as AlGaInP-based red micro-LEDs. Various inventive embodiments are described herein, including devices, systems, methods, materials, processes, etc.

[0041] In a semiconductor light-emitting diode (LED), photons are typically generated through the recombination of electrons and holes within an active region (e.g., one or more semiconductor layers) at a given internal quantum efficiency (IQE). The IQE is the ratio of radiative electron-hole recombination in the active region that emits photons. The generated light can then be extracted from the LED in a specific direction or within a specific solid angle. The ratio between the number of emitted photons extracted from the LED and the number of electrons that pass through the LED is called the external quantum efficiency (EQE), which describes how efficiently the LED converts injected electrons into photons extracted from it. For LEDs, especially micro-LEDs with reduced physical dimensions, both the IQE and EQE can be very low, and improving the quantum efficiency of LEDs can be challenging.

[0042] The quantum efficiency of an LED depends on the relative rates of competing radiative (light-generating) and nonradiative (lossy) recombination occurring in the active region of the LED. Nonradiative recombination processes in the active region include Shockley-Read-Hall (SRH) recombination at defect sites, and electron-electron-hole (eeh) and / or electron-hole-hole (ehh) Auger recombination; electron-electron-hole and / or electron-hole-hole Auger recombination are nonradiative processes involving three charge carriers. In micro-LEDs, because the size of the LED may be comparable to the minority carrier diffusion length, most of the active region may be less than this minority carrier diffusion length (within which defect density and nonradiative recombination rates may be higher), thus allowing more injected charge carriers to diffuse into the region near these sidewall surfaces and potentially experience higher SRH recombination rates. This can lead to a decrease in the peak efficiency of the LED or an increase in the peak efficiency operating current. Increased current injection can cause the efficiency of micro-LEDs to decrease due to the higher Eeh or Eh Auger recombination rates at higher current densities. As the physical size of LEDs is further reduced, efficiency losses become more significant due to surface recombination near etched sidewall facets (which include surface defects). AlGaInP materials have high surface recombination rates and minority carrier diffusion lengths. For example, carriers in AlGaInP materials can have high diffusivity (mobility), and AlGaInP materials can have surface recombination rates an order of magnitude higher than those of group III nitride materials. Therefore, the internal and external quantum efficiencies of AlGaInP red LEDs may decrease even more significantly with decreasing device size.

[0043] According to certain embodiments, a micro-LED (e.g., an AlGaInP red micro-LED) may include a current hole for confining current to a local region much smaller than the size of the micro-LED, such that carrier recombination can occur primarily in this local region to emit photons, and the diffusion of injected carriers from the active region to the sidewalls of the micro-LED can be reduced, thereby reducing surface recombination and improving quantum efficiency. For example, current confinement and localization can be achieved by: (1) local breakdown of a barrier layer (e.g., a thyristor, tunnel junction, heterojunction, etc.) by using local contacts (e.g., pointed p-contacts, submicron p-contacts, or filaments) to generate a high electric field in the local region, or by using local defects in the barrier layer, which allows for local injection and confinement of carriers to the active region; (2) selective ion implantation, etching, oxidation, etc. of the semiconductor layer; (3) a lightly p-doped active layer for suppressing lateral transport (e.g., diffusion) of carriers to the surface region; or any combination of (1) to (3). Current localization can also induce self-heating in the semiconductor. Since carrier diffusivity and mobility decrease at higher temperatures, this, in turn, reduces carrier diffusion towards the sidewalls of the active region. Light p-doping in the active region allows the trapped states at the surface to move further away from the Fermi level and can form a hole depletion region, which reduces hole diffusion towards the sidewalls. Therefore, the hole concentration at the sidewalls can be reduced, and thus non-radiative surface recombination can be minimized. Furthermore, due to the limitation and localization of the injection current, light emission can occur only in localized regions, which facilitates more efficient light extraction and external coupling from the micro-LED. Therefore, the overall external quantum efficiency of the micro-LED can be improved.

[0044] The micro-LEDs described herein can be used in conjunction with various technologies, such as artificial reality systems. Artificial reality systems (e.g., head-mounted display (HMD) systems or heads-up display (HUD) systems) typically include a display configured to present artificial images depicting objects in a virtual environment. As in virtual reality (VR), augmented reality (AR), or mixed reality (MR) applications, the display can present images of virtual objects, or a combination of real and virtual objects. For example, in AR systems, a user can view both a display image of a virtual object (e.g., a computer-generated image (CGI)) and the surrounding environment, for instance, by looking through transparent display glasses or lenses (often referred to as optical see-through) or by viewing a display image of the surrounding environment captured by a camera (often referred to as video see-through). In some AR systems, an LED-based display subsystem can be used to present artificial images to the user.

[0045] As used herein, the term "light-emitting diode (LED)" refers to a light source comprising at least an n-type semiconductor layer, a p-type semiconductor layer, and a light-emitting region (i.e., an active region) located between the n-type and p-type semiconductor layers. The light-emitting region may include one or more semiconductor layers forming one or more heterostructures, such as quantum wells. In some embodiments, the light-emitting region may include multiple semiconductor layers forming one or more multiple-quantum-wells (MQWs), each MQW comprising multiple (e.g., about two to six) quantum wells.

[0046] As used herein, the term "micro-LED" or "μLED" refers to an LED having a chip with a linear dimension less than about 200 μm, for example, less than 100 μm, less than 50 μm, less than 20 μm, less than 10 μm, or smaller. For example, the linear dimension of a micro-LED can be as small as 6 μm, 5 μm, 4 μm, 2 μm, or smaller. Some micro-LEDs may have a linear dimension (e.g., length or diameter) comparable to the minority carrier diffusion length. However, the disclosure herein is not limited to micro-LEDs and can also be applied to small-sized LEDs (mini-LEDs) and large-sized LEDs.

[0047] As used herein, the term "bonding" can refer to various methods used to physically and / or electrically connect two or more devices and / or wafers, such as adhesive bonding, metal-to-metal bonding, metal-oxide bonding, wafer-to-wafer bonding, die-to-wafer bonding, hybrid bonding, soldering, under-bump metallization, etc. For example, adhesive bonding can use a curable adhesive (e.g., epoxy resin) to physically bond two or more devices and / or wafers through adhesive forces. For example, metal-to-metal bonding can include wire bonding or flip-chip bonding using solder surfaces (e.g., pads or solder balls), conductive adhesives, or intermetallic solder joints. Metal-oxide bonding can form metal and oxide patterns on each surface, bonding multiple oxide portions together, and then bonding multiple metal portions together to form a conductive path. Wafer-to-wafer bonding can bond two wafers (e.g., silicon wafers or other semiconductor wafers) without any intermediate layers, and this wafer-to-wafer bonding is based on chemical bonds between the surfaces of the two wafers. Wafer-to-wafer bonding may include wafer cleaning and other pre-processing, alignment and pre-bonding at room temperature, and annealing at high temperatures (e.g., about 250°C or higher). Die-to-wafer bonding may use multiple bumps on a wafer to align multiple features of a pre-formed chip with multiple drivers on that wafer. For example, hybrid bonding may include wafer cleaning, high-precision alignment of multiple contacts on one wafer with multiple contacts on another wafer, dielectric bonding of dielectric materials within these wafers at room temperature, and metal bonding of multiple contacts by annealing at temperatures such as 250°C to 300°C or higher. As used herein, the term "bump" may generally refer to a metal interconnect used or formed during bonding.

[0048] In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of various examples of this disclosure. However, it will be apparent, however, that various examples can be practiced without these specific details. For example, devices, systems, structures, components, methods, and other parts may be shown as multiple parts in the form of block diagrams so as not to obscure these examples with unnecessary detail. In other instances, well-known devices, processes, systems, structures, and techniques may be shown without necessary detail to avoid obscuring these examples. The accompanying drawings and description are not intended to be limiting. The terms and expressions used in this disclosure are used as descriptive terms rather than limiting terms and are not intended to exclude any equivalents of the multiple features shown and described, or partial features of such features, when using such terms and expressions. In this document, the word “example” is used to mean “used as an example, instance, or illustration.” Any embodiment or design described herein as an “example” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0049] Figure 1 A simplified block diagram of an example of an artificial reality system environment 100 including a near-eye display 120 according to certain embodiments. Figure 1 The illustrated artificial reality system environment 100 may include a near-eye display 120, an optional external imaging device 150, and an optional input / output interface 140, each of which may be coupled to an optional console 110. Although Figure 1 An example of an artificial reality system environment 100 is shown, including a near-eye display 120, an external imaging device 150, and an input / output interface 140. However, the artificial reality system environment 100 may include any number of these components, or any of these components may be omitted. For example, it may have multiple near-eye displays 120 monitored by one or more external imaging devices 150 communicating with a console 110. In some configurations, the artificial reality system environment 100 may not include the external imaging device 150, the optional input / output interface 140, and the optional console 110. In alternative configurations, the artificial reality system environment 100 may include different or additional components.

[0050] The near-eye display 120 may be a head-mounted display that presents content to a user. Examples of content presented by the near-eye display 120 include one or more of the following: images, videos, audio, or any combination thereof. In some embodiments, audio may be presented via an external device (e.g., speakers and / or headphones) that receives audio information from the near-eye display 120, the console 110, or both the near-eye display and the console, and presents audio data based on that audio information. The near-eye display 120 may include one or more rigid bodies that may be rigidly or non-rigidly joined together. Rigid joining between multiple rigid bodies allows the joined rigid bodies to function as a single rigid entity. Non-rigid joining between multiple rigid bodies allows these rigid bodies to move relative to each other. In various embodiments, the near-eye display 120 may be implemented with any suitable shape factor, including a pair of glasses. The following references Figure 2 and Figure 3 Some embodiments of the near-eye display 120 are further described. Additionally, in various embodiments, the functionality described herein can be used in a head-mounted viewer that combines images of the external environment of the near-eye display 120 with artificial reality content (e.g., computer-generated images). Therefore, the near-eye display 120 can utilize generated content (e.g., images, videos, sounds, etc.) to enhance images of the physical, real-world environment outside the near-eye display 120 to present augmented reality to the user.

[0051] In various embodiments, the near-eye display 120 may include one or more of display electronics 122, display optics 124, and an eye-tracking unit 130. In some embodiments, the near-eye display 120 may also include one or more locators 126, one or more position sensors 128, and an inertial measurement unit (IMU) 132. The near-eye display 120 may omit any one of the eye-tracking unit 130, locator 126, position sensor 128, and IMU 132, or may include multiple additional elements as in various embodiments. Additionally, in some embodiments, the near-eye display 120 may include a combination of... Figure 1 The functions of various components described are multiple components.

[0052] Display electronics 122 can display images to a user or facilitate the display of images to a user based on data received from, for example, console 110. In various embodiments, display electronics 122 may include one or more display panels, such as a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, an inorganic light-emitting diode (ILED) display, a micro light-emitting diode (μLED) display, an active-matrix OLED display (AMOLED), a transparent OLED display (TOLED), or some other type of display. For example, in one embodiment of the near-eye display 120, display electronics 122 may include a front TOLED panel, a rear display panel, and optical components (e.g., attenuators, polarizers, or diffraction or spectral films) between the front TOLED panel and the rear display panel. Display electronics 122 may include a plurality of pixels for emitting light of primary colors such as red, green, blue, white, or yellow. In some embodiments, display electronics 122 can display three-dimensional (3D) images by creating a stereoscopic effect from multiple two-dimensional panels to generate a subjective perception of image depth. For example, display electronics 122 may include a left display positioned in front of the user's left eye and a right display positioned in front of the user's right eye. The left and right displays may present horizontally shifted copies of the image relative to each other to create a stereoscopic effect (i.e., the user perceives image depth by viewing the image).

[0053] In some embodiments, display optics 124 may optically display image content (e.g., using optical waveguides and couplers to optically display image content) or amplify received image light from display electronics 122, correct optical errors associated with the image light, and present corrected image light to a user of near-eye display 120. In various embodiments, display optics 124 may include one or more optical elements, such as a substrate, optical waveguide, aperture, Fresnel lens, convex lens, concave lens, filter, input / output coupler, or any other suitable optical element that may affect the image light emitted from display electronics 122. Display optics 124 may include combinations of different optical elements and multiple mechanical couplings for maintaining the relative spacing and orientation of these optical elements in the combination. One or more optical elements in display optics 124 may have optical coatings, such as anti-reflective coatings, reflective coatings, filter coatings, or combinations of different optical coatings.

[0054] The amplification of image light by the display optics 124 allows the display electronics 122 to be physically smaller, lighter, and consume less power compared to a larger display. Additionally, the amplification increases the field of view of the displayed content. The amplification amount of image light by the display optics 124 can be varied by adjusting, adding, or removing optical elements from the display optics 124. In some embodiments, the display optics 124 can project a display image onto one or more image planes that are further away from the user's eye than the near-eye display 120.

[0055] Display optics 124 can also be designed to correct one or more types of optical errors, such as two-dimensional optical errors, three-dimensional optical errors, or any combination thereof. Two-dimensional errors can include optical aberrations occurring in two dimensions. Example types of two-dimensional errors can include barrel distortion, pincushion distortion, longitudinal chromatic aberration, and lateral chromatic aberration. Three-dimensional errors can include optical errors occurring in three dimensions. Example types of three-dimensional errors can include spherical aberration, coma, field curvature, and astigmatism.

[0056] The multiple locators 126 may be multiple objects located at multiple specific positions on the near-eye display 120 relative to each other and relative to a reference point on the near-eye display 120. In some embodiments, the console 110 may identify the multiple locators 126 in images acquired by the external imaging device 150 to determine the position, orientation, or both position and orientation of the artificial reality head-mounted viewer. The locators 126 may be LEDs, corner cube reflectors, reflective markers, a light source that contrasts with the environment in which the near-eye display 120 operates, or any combination thereof. In embodiments where the multiple positioners 126 are multiple active components (e.g., LEDs or other types of light-emitting devices), the multiple positioners 126 may emit light in the visible band (e.g., about 380 nanometers (nm) to 750 nm), light in the infrared (IR) band (e.g., about 750 nm to 1 mm), light in the ultraviolet band (e.g., about 10 nm to about 380 nm), light in another part of the electromagnetic spectrum, or light in any combination of multiple parts of the electromagnetic spectrum.

[0057] External imaging device 150 may include one or more cameras, one or more video cameras, any other device capable of acquiring images including one or more of the plurality of positioners 126, or any combination thereof. Additionally, external imaging device 150 may include one or more filters (e.g., to increase the signal-to-noise ratio). External imaging device 150 may be configured to detect light emitted or reflected from the plurality of positioners 126 in the field of view of external imaging device 150. In embodiments where the plurality of positioners 126 includes a plurality of passive elements (e.g., retroreflectors), external imaging device 150 may include a light source illuminating some or all of the plurality of positioners 126 (which may reflect light back to a light source in external imaging device 150). Slow calibration data may be transmitted from external imaging device 150 to console 110, and external imaging device 150 may receive one or more calibration parameters from console 110 to adjust one or more imaging parameters (e.g., focal length, focus, frame rate, sensor temperature, shutter speed, aperture, etc.).

[0058] Multiple position sensors 128 may generate one or more measurement signals in response to movement of the near-eye display 120. Examples of multiple position sensors 128 may include accelerometers, gyroscopes, magnetometers, other motion detection or error correction sensors, or any combination thereof. For example, in some embodiments, multiple position sensors 128 may include multiple accelerometers for measuring translational movement (e.g., forward / backward, up / down, or left / right) and multiple gyroscopes for measuring rotational movement (e.g., pitch, yaw, or roll). In some embodiments, the various position sensors may be orthogonally oriented to each other.

[0059] IMU 132 can be an electronic device that generates rapid calibration data based on measurement signals received from one or more of a plurality of position sensors 128. The plurality of position sensors 128 can be located external to IMU 132, internal to IMU 132, or any combination thereof. Based on one or more measurement signals from one or more position sensors 128, IMU 132 can generate rapid calibration data indicating an estimated position of the near-eye display 120 relative to an initial position. For example, IMU 132 can integrate multiple measurement signals received from multiple accelerometers over time to estimate a velocity vector, and integrate that velocity vector over time to determine an estimated position of a reference point on the near-eye display 120. Alternatively, IMU 132 can provide sampled measurement signals to console 110 that can determine the rapid calibration data. While a reference point can generally be defined as a point in space, in various embodiments, a reference point can also be defined as a point within the near-eye display 120 (e.g., the center of IMU 132).

[0060] Eye-tracking unit 130 may include one or more eye-tracking systems. Eye tracking can refer to determining the positioning of the eyes relative to the near-eye display 120, including the orientation and position of the eyes relative to the near-eye display. The eye-tracking system may include an imaging system for imaging one or more eyes, and may optionally include a light emitter that generates light that is directed to the eyes such that light reflected from the eyes can be captured by the imaging system. For example, eye-tracking unit 130 may include an incoherent or coherent light source (e.g., a laser diode) that emits light in the visible or infrared spectrum, and a camera that captures the light reflected from the user's eyes. As another example, eye-tracking unit 130 may capture reflected radio waves emitted by a small radar unit. Eye-tracking unit 130 may use multiple low-power light emitters that emit light at frequencies and intensities that will not harm the eyes or cause physical discomfort. The eye-tracking unit 130 can be arranged to increase the contrast in the image of the eye acquired by the eye-tracking unit 130 while reducing the total power consumed by the eye-tracking unit 130 (e.g., reducing the power consumed by the light emitter and imaging system included in the eye-tracking unit 130). For example, in some embodiments, the eye-tracking unit 130 may consume less than 100 milliwatts of power.

[0061] The near-eye display 120 can use eye orientation to, for example, determine the user's interpupillary distance (IPD), determine gaze direction, introduce depth cues (e.g., blurring images outside the user's primary line of sight), collect exploration of user interactions in VR media (e.g., the time spent on any particular object, scene, or frame based on experienced stimuli), perform other functions partially based on the orientation of at least one of the user's eyes, or any combination thereof. Since orientation can be determined for both of the user's eyes, the eye-tracking unit 130 is able to determine where the user is looking. For example, determining the direction of the user's gaze may include determining a convergence point based on the determined orientation of the user's left and right eyes. The convergence point may be the point where the two foveal axes of the user's eyes intersect. The direction of the user's gaze may be the direction of a line passing through the convergence point and the midpoint between the pupils of the user's eyes.

[0062] Input / output interface 140 may be a device that allows a user to send action requests to console 110. An action request may be a request to perform a specific action. For example, an action request may be to launch an application, terminate an application, or perform a specific action within an application. Input / output interface 140 may include one or more input devices. Example input devices may include a keyboard, mouse, game controller, gloves, buttons, touchscreen, or any other suitable device for receiving action requests and transmitting the received action requests to console 110. Action requests received by input / output interface 140 may be transmitted to console 110, which may perform an action corresponding to the requested action. In some embodiments, input / output interface 140 may provide haptic feedback to the user based on instructions received from console 110. For example, input / output interface 140 may provide haptic feedback when an action request is received, or when console 110 has performed the requested action and transmitted instructions to input / output interface 140. In some embodiments, the external imaging device 150 may be used to track the input / output interface 140, such as the location or position of a controller (which may include, for example, an IR light source), or the location or position of a user's hand, to determine user actions. In some embodiments, the near-eye display 120 may include one or more imaging devices for tracking the input / output interface 140, such as the location or position of a controller, or the location or position of a user's hand, to determine user actions.

[0063] The console 110 can provide content to the near-eye display 120 for presentation to the user based on information received from one or more of the external imaging device 150, the near-eye display 120, and the input / output interface 140. Figure 1 In the example shown, console 110 may include an app store 112, a head-mounted viewer tracking module 114, an artificial reality engine 116, and an eye-tracking module 118. Some embodiments of console 110 may include [missing information - likely related to integration / combination]. Figure 1 The modules described herein are different from or additional modules. The functions further described below may be distributed among multiple components of console 110 in a manner different from that described herein.

[0064] In some embodiments, console 110 may include a processor and a non-transitory computer-readable storage medium storing multiple instructions executable by the processor. The processor may include multiple processing units that execute the multiple instructions in parallel. The non-transitory computer-readable storage medium may be any memory, such as a hard disk drive, removable memory, or solid-state drive (e.g., flash memory or dynamic random access memory (DRAM)). In various embodiments, in combination with... Figure 1 The various modules of the described console 110 can be encoded into a variety of instructions in a non-transitory computer-readable storage medium, which, when executed by a processor, cause the processor to perform a variety of functions further described below.

[0065] Application store 112 may store one or more applications for execution by console 110. An application may include a set of instructions that, when executed by the processor, generate content to be presented to the user. The content generated by the application may be in response to input received from the user through eye movement or input received from input / output interface 140. Examples of applications may include game applications, conferencing applications, video playback applications, or other suitable applications.

[0066] The head-mounted display tracking module 114 can use slow calibration data from the external imaging device 150 to track the movement of the near-eye display 120. For example, the head-mounted display tracking module 114 can use multiple locators observed from the slow calibration data and a model of the near-eye display 120 to determine the position of a reference point for the near-eye display 120. The head-mounted display tracking module 114 can also use position information from fast calibration data to determine the position of the reference point for the near-eye display 120. Additionally, in some embodiments, the head-mounted display tracking module 114 can use multiple components of fast calibration data, slow calibration data, or any combination thereof to predict the future position of the near-eye display 120. The head-mounted display tracking module 114 can provide the artificial reality engine 116 with an estimated or predicted future position of the near-eye display 120.

[0067] The artificial reality engine 116 can execute applications within the artificial reality system environment 100 and receive position information, acceleration information, velocity information, predicted future position of the near-eye display 120, or any combination thereof from the head-mounted viewer tracking module 114. The artificial reality engine 116 can also receive estimated eye position and orientation information from the eye-tracking module 118. Based on the received information, the artificial reality engine 116 can determine the content to be provided to the near-eye display 120 for presentation to the user. For example, if the received information indicates that the user has looked to the left, the artificial reality engine 116 can generate content for the near-eye display 120 that reflects the movement of the user's eyes in the virtual environment. Additionally, the artificial reality engine 116 can respond to action requests received from the input / output interface 140, execute actions within an application running on the console 110, and provide feedback to the user indicating that the action has been performed. The feedback can be visual or auditory feedback via the near-eye display 120, or tactile feedback via the input / output interface 140.

[0068] The eye-tracking module 118 can receive eye-tracking data from the eye-tracking unit 130 and determine the position of the user's eyes based on the eye-tracking data. The position of the eyes can include the orientation, position, or both orientation and position of the eyes relative to the near-eye display 120 or any element of the near-eye display. Since the axis of rotation of the eye changes as the eye is positioned in its orbit, determining the position of the eye in its orbit allows the eye-tracking module 118 to determine the orientation of the eyes more accurately.

[0069] Figure 2 This is a stereoscopic view of an example of a near-eye display in the form of an HMD device 200 used to implement some of the various examples disclosed herein. The HMD device 200 may be, for example, a VR system, an AR system, a MR system, or any combination thereof. The HMD device 200 may include a body 220 and a headband 230. Figure 2 The bottom side 223, front side 225, and left side 227 of the main body 220 are shown in a perspective view. The headband 230 may have an adjustable or extendable length. Sufficient space may be provided between the main body 220 and the headband 230 of the HMD device 200 to allow a user to wear the HMD device 200 on their head. In various embodiments, the HMD device 200 may include additional components, fewer components, or different components. For example, in some embodiments, the HMD device 200 may include eyeglass temples and temple tips (e.g., as follows). Figure 3 (as shown), instead of headband 230.

[0070] HMD device 200 can present media to a user, including virtual and / or augmented views of a physically real-world environment with computer-generated elements. Examples of media presented by HMD device 200 may include images (e.g., two-dimensional (2D) images or three-dimensional (3D) images), video (e.g., 2D or 3D video), audio, or any combination thereof. This can be achieved through one or more display components housed in the body 220 of HMD device 200. Figure 2 (Not shown in the image) to present these images and videos to each of the user's eyes. In various embodiments, the one or more display components may include a single electronic display panel or multiple electronic display panels (e.g., one display panel for each of the user's eyes). Examples of one or more electronic display panels may include, for example, LCD, OLED, ILED, μLED, AMOLED, TOLED, some other display, or any combination thereof. HMD device 200 may include two eyebox areas.

[0071] In some embodiments, the HMD device 200 may include various sensors (not shown), such as depth sensors, motion sensors, position sensors, and eye-tracking sensors. Some of these sensors may be detected using structured light patterns. In some embodiments, the HMD device 200 may include an input / output interface for communicating with a console. In some embodiments, the HMD device 200 may include a virtual reality engine (not shown) that can execute multiple applications within the HMD device 200 and receive depth information, position information, acceleration information, velocity information, predicted future position, or any combination thereof from various sensors of the HMD device 200. In some embodiments, the information received by the virtual reality engine may be used to generate signals (e.g., display instructions) for one or more display components. In some embodiments, the HMD device 200 may include a plurality of positioners (not shown, e.g., a plurality of positioners 126) located at multiple fixed positions on the body 220 relative to each other and relative to a reference point. Each of these positioners may emit light that can be detected by an external imaging device.

[0072] Figure 3 A stereoscopic view of an example of a near-eye display 300 in the form of glasses, used to implement some of the examples disclosed herein. The near-eye display 300 may be... Figure 1This describes a specific embodiment of the near-eye display 120, and it can be configured to operate as a virtual reality display, an augmented reality display, and / or a mixed reality display. The near-eye display 300 may include a frame 305 and a display 310. The display 310 may be configured to present content to a user. In some embodiments, the display 310 may include display electronics and / or display optics. For example, as described above regarding... Figure 1 As described in the near-eye display 120, the display 310 may include an LCD display panel, an LED display panel, or an optical display panel (e.g., a waveguide display assembly).

[0073] The near-eye display 300 may also include various sensors 350a, 350b, 350c, 350d, and 350e located on or within the frame 305. In some embodiments, sensors 350a-350e may include one or more depth sensors, one or more motion sensors, one or more position sensors, one or more inertial sensors, or one or more ambient light sensors. In some embodiments, sensors 350a-350e may include one or more image sensors configured to generate image data representing different fields of view in different directions. In some embodiments, sensors 350a-350e may be used as input devices to control or influence the content displayed on the near-eye display 300, and / or to provide an interactive VR / AR / MR experience to the user of the near-eye display 300. In some embodiments, sensors 350a-350e may also be used for stereoscopic imaging.

[0074] In some embodiments, the near-eye display 300 may further include one or more illuminators 330 for projecting light into a physical environment. The projected light may be associated with different frequency bands (e.g., visible light, infrared light, ultraviolet light, etc.) and may be used for various purposes. For example, one or more illuminators 330 may project light into a dark environment (or an environment with low-intensity infrared, ultraviolet, etc.) to assist the radiation-assisted sensors 350a-350e in acquiring images of different objects within the dark environment. In some embodiments, one or more illuminators 330 may be used to project certain light patterns onto multiple objects within the environment. In some embodiments, one or more illuminators 330 may function as locators, as described above regarding... Figure 1 The described locator 126.

[0075] In some embodiments, the near-eye display 300 may further include a high-resolution camera 340. The camera 340 can capture images of the physical environment within the field of view. For example, it can be generated by a virtual reality engine (e.g., Figure 1The artificial reality engine 116 in the image processes the captured images to add virtual objects to the captured images or modify physical objects in the captured images, and the processed images can be displayed to the user by the display 310 for use in AR or MR applications.

[0076] Figure 4An example of an optical see-through augmented reality system 400 including a waveguide display according to certain embodiments is shown. Augmented reality system 400 may include a projector 410 and a combiner 415. Projector 410 may include a light source or image source 412 and projector optics 414. In some embodiments, light source or image source 412 may include one or more of the aforementioned micro-LED devices. In some embodiments, light source or image source 412 may include multiple pixels displaying virtual objects, such as an LCD display panel or an LED display panel. In some embodiments, light source or image source 412 may include a light source that generates coherent or partially coherent light. For example, light source or image source 412 may include a laser diode, a vertical-cavity surface-emitting laser, an LED, and / or the aforementioned micro-LEDs. In some embodiments, light source or image source 412 may include multiple light sources (e.g., an array of the aforementioned micro-LEDs), each emitting monochromatic image light corresponding to a primary color (e.g., red, green, or blue). In some embodiments, the light source or image source 412 may include three two-dimensional micro-LED arrays, each of which may include a plurality of micro-LEDs configured to emit light of a primary color (e.g., red, green, or blue). In some embodiments, the light source or image source 412 may include an optical pattern generator, such as a spatial light modulator. The projector optics 414 may include one or more optical components that can modulate the light from the light source or image source 412, for example, by expanding, collimating, scanning, or projecting the light from the light source or image source onto the combiner 415. The one or more optical components may include, for example, one or more lenses, one or more liquid lenses, one or more mirrors, one or more apertures, and / or one or more gratings. For example, in some embodiments, the light source or image source 412 may include one or more one-dimensional micro-LED arrays or one or more elongated two-dimensional micro-LED arrays, and the projector optics 414 may include one or more one-dimensional scanners (e.g., micromirrors or prisms) configured to scan the one-dimensional or elongated two-dimensional micro-LED arrays to generate image frames. In some embodiments, the projector optics 414 may include a liquid lens (e.g., a liquid crystal lens) having multiple electrodes, which allows scanning of light from the light source or image source 412.

[0077] Combiner 415 may include an input coupler 430 for coupling light from projector 410 to substrate 420 of combiner 415. Combiner 415 may transmit at least 50% of light in a first wavelength range and reflect at least 25% of light in a second wavelength range. For example, the first wavelength range may be visible light from about 400 nm to about 650 nm, and the second wavelength range may be in the infrared band, for example from about 800 nm to about 1000 nm. Input coupler 430 may include a volume holographic grating, a diffractive optical element (DOE) (e.g., a surface-relief grating), a tilted surface of substrate 420, or a refractive coupler (e.g., a wedge or prism). For example, input coupler 430 may include a reflective volume Bragg grating or a transmissive volume Bragg grating. Input coupler 430 may have a coupling efficiency greater than 30%, 50%, 75%, 90%, or higher for visible light. Light coupled into substrate 420 can propagate within substrate 420 via, for example, total internal reflection (TIR). Substrate 420 can be in the form of a lens for eyeglasses. Substrate 420 can have a flat or curved surface and can comprise one or more types of dielectric materials, such as glass, quartz, plastic, polymer, poly(methyl methacrylate) (PMMA), crystal, or ceramic. The thickness of the substrate can range, for example, from less than about 1 mm to about 10 mm or more. Substrate 420 can be transparent to visible light.

[0078] The substrate 420 may include, or be coupled to, a plurality of output couplers 440, each output coupler configured to extract at least a portion of light guided by and propagating within the substrate 420 and to direct the extracted light 460 to an eye-fitting region 495, where the user's eye 490 can be located when the augmented reality system 400 is in use. The plurality of output couplers 440 may replicate an exit pupil to increase the size of the eye-fitting region 495, making the displayed image visible over a larger area. Similar to the input coupler 430, the output couplers 440 may include grating couplers (e.g., volume holographic gratings or surface relief gratings), other diffractive optical elements (DOEs), prisms, etc. For example, the output coupler 440 may include a reflective volume Bragg grating or a transmissive volume Bragg grating. The plurality of output couplers 440 may have different coupling (e.g., diffraction) efficiencies at different locations. The substrate 420 can also allow light 450 from the environment in front of the combiner 415 to pass through with almost no loss or lossless transmission. The output coupler 440 can also allow light 450 to pass through with very little loss. For example, in some embodiments, the output coupler 440 can have a very low diffraction efficiency for light 450, such that light 450 can be refracted with very little loss, or otherwise pass through the output coupler 440 with very little loss, thus allowing the light to have a higher intensity than the extracted light 460. In some embodiments, the output coupler 440 can have a high diffraction efficiency for light 450 and can diffract light 450 with little loss in certain desired directions (i.e., diffraction angles). Therefore, a user may be able to view the combined image of the environment in front of the combiner 415 and the image of the virtual object projected by the projector 410.

[0079] Figure 5AAn example of a near-eye display (NED) device 500 including a waveguide display 530 according to certain embodiments is shown. The NED device 500 may be an example of a near-eye display 120, an augmented reality system 400, or another type of display device. The NED device 500 may include a light source 510, projection optics 520, and a waveguide display 530. The light source 510 may include multiple panels of multiple light emitters of different colors, for example, a panel of multiple red light emitters 512, a panel of multiple green light emitters 514, and a panel of multiple blue light emitters 516. The multiple red light emitters 512 are organized into an array; the multiple green light emitters 514 are organized into an array; and the multiple blue light emitters 516 are organized into an array. The size and spacing of the multiple light emitters in the light source 510 can be very small. For example, each light emitter may have a diameter of less than 2 μm (e.g., about 1.2 μm) and a spacing of less than 2 μm (e.g., about 1.5 μm). In this respect, the number of light emitters in each red light emitter 512, the number of light emitters in each green light emitter 514, and the number of light emitters in each blue light emitter 516 can be equal to or greater than the number of pixels in a displayed image, such as 960×720 pixels, 1280×720 pixels, 1440×1080 pixels, 1920×1080 pixels, 2160×1080 pixels, or 2560×1080 pixels. Therefore, the light source 510 can synchronously generate the displayed image. The NED device 500 can operate without a scanning element.

[0080] The light emitted by the light source 510 can be calibrated by a projection optics device 520 (which includes a lens array) before reaching the waveguide display 530. The projection optics device 520 can collimate or focus the light emitted by the light source 510 onto the waveguide display 530, which may include a coupler 532 for coupling the light emitted by the light source 510 into the waveguide display 530. The light coupled into the waveguide display 530 can be, for example, as described above... Figure 4 The described total internal reflection propagates within the waveguide display 530. Coupler 532 can also couple multiple portions of the light propagating within the waveguide display 530 to the outside of the waveguide display 530 and toward the user's eye 590.

[0081] Figure 5BAn example of a near-eye display (NED) device 550 including a waveguide display 580 according to certain embodiments is shown. In some embodiments, the NED device 550 may use a scanning mirror 570 to project light from a light source 540 onto an image field in which a user's eye 590 may be located. The NED device 550 may be an example of a near-eye display 120, an augmented reality system 400, or another type of display device. The light source 540 may include one or more rows of light emitters of different colors, or one or more columns of light emitters of different colors, such as multiple rows of red light emitters 542, multiple rows of green light emitters 544, and multiple rows of blue light emitters 546. For example, the plurality of red light emitters 542, the plurality of green light emitters 544, and the plurality of blue light emitters 546 may each include N rows, each row including, for example, 2560 light emitters (pixels). The plurality of red light emitters 542 are organized into an array; the plurality of green light emitters 544 are organized into an array; and the plurality of blue light emitters 546 are organized into an array. In some embodiments, light source 540 may include a single row of light emitters for each color. In some embodiments, light source 540 may include multiple rows of light emitters for each of the colors red, green, and blue, wherein each row may, for example, include 1080 light emitters. In some embodiments, the size and / or spacing of the multiple light emitters in light source 540 may be relatively large (e.g., about 3 μm to 5 μm), so light source 540 may not include multiple light emitters sufficient to synchronously generate a complete display image. For example, the number of light emitters for a single color may be less than the number of pixels in the display image (e.g., 2560 × 1080 pixels). The light emitted by light source 540 may be a collimated or divergent beam.

[0082] The light emitted by the light source 540 can be modulated by various optical devices, such as collimating lenses or freeform optical elements 560, before reaching the scanning mirror 570. The freeform optical element 560 may include, for example, a faceted prism or another light-folding element that can guide the light emitted by the light source 540 to the scanning mirror 570, thereby changing, for example, the propagation direction of the light emitted by the light source 540 by about 90° or more. In some embodiments, the freeform optical element 560 may be rotatable to scan the light. The scanning mirror 570 and / or the freeform optical element 560 can reflect and project the light emitted by the light source 540 onto a waveguide display 580, which may include a coupler 582 for coupling the light emitted by the light source 540 into the waveguide display 580. The light coupled into the waveguide display 580 can be, for example, as described above... Figure 4The described total internal reflection propagates within the waveguide display 580. Coupler 582 can also couple multiple portions of the light propagating within the waveguide display 580 out of the waveguide display 580 and toward the user's eye 590.

[0083] The scanning mirror 570 may include a microelectromechanical (MEMS) mirror or any other suitable mirror. The scanning mirror 570 can rotate to perform one-dimensional or two-dimensional scanning. As the scanning mirror 570 rotates, light emitted by the light source 540 can be directed to different areas of the waveguide display 580, such that in each scanning cycle, a complete display image can be projected onto the waveguide display 580 and directed by the waveguide display 580 to the user's eye 590. For example, in embodiments where the light source 540 includes multiple light emitters for all pixels in one or more rows, or multiple light emitters for all pixels in one or more columns, the scanning mirror 570 can rotate in the column direction or row direction (e.g., the x-direction or y-direction) to scan the image. In embodiments where the light source 540 includes multiple light emitters for some, but not all, of pixels in one or more rows or columns, the scanning mirror 570 can rotate in both row and column directions (e.g., x and y directions) to project an image (e.g., using a raster-type scanning pattern to project an image).

[0084] The NED device 550 can operate within a predefined display period. A display period (e.g., a cycle) can refer to the duration of scanning or projecting a complete image. For example, the display period can be the reciprocal of the desired frame rate. In the NED device 550 including a scanning mirror 570, the display period can also be referred to as a scanning period or scanning cycle. The light generation performed by the light source 540 can be synchronized with the rotation of the scanning mirror 570. For example, each scanning cycle can include multiple scanning steps, where the light source 540 can generate different light patterns in each corresponding scanning step.

[0085] During each scan cycle, as the scanning mirror 570 rotates, a display image can be projected onto the waveguide display 580 and the user's eye 590. The actual color value and light intensity (e.g., luminance) of a given pixel location in the display image can be the average of the beams of three colors (e.g., red, green, and blue) illuminating that pixel location during the scan cycle. After completing a scan cycle, the scanning mirror 570 can return to its initial position to project light for the first few rows of the next display image, or it can rotate in the opposite direction or in the opposite scan mode to project light for the next display image, wherein a new set of drive signals can be fed to the light source 540. The same process can be repeated during each scan cycle as the scanning mirror 570 rotates. In this respect, different images can be projected onto the user's eye 590 in different scan cycles.

[0086] Figure 6 An example of an image source component 610 in a near-eye display system 600 according to certain embodiments is shown. The image source component 610 may, for example, include a display panel 640 and a projector 650, the display panel generating a display image to be projected onto a user's eyes, and the projector projecting the display image generated by the display panel 640 onto a screen as described above. Figures 4 to 5B The waveguide display described herein. Display panel 640 may include a light source 642 and driving circuitry 644 for the light source 642. Light source 642 may, for example, include light source 510 or 540. Projector 650 may, for example, include the aforementioned freeform optical element 560, the aforementioned scanning mirror 570, and / or the aforementioned projection optics 520. Near-eye display system 600 may also include controller 620, which synchronously controls the light source 642 and projector 650 (e.g., scanning mirror 570). Image source assembly 610 may generate image light and output the image light to the waveguide display (…). Figure 6 (Not shown in the diagram), for example, output to waveguide display 530 or 580. As described above, the waveguide display can receive image light at one or more input coupling elements and guide the received image light to one or more output coupling elements. The input coupling elements and output coupling elements may include, for example, diffraction gratings, holographic gratings, prisms, or any combination thereof. The input coupling elements can be selected such that the waveguide display undergoes total internal reflection. The output coupling elements can couple multiple portions of the totally internally reflected image light outside the waveguide display.

[0087] As described above, light source 642 may include a plurality of light emitters arranged in an array or matrix. Each light emitter may emit monochromatic light, such as red, blue, green, infrared, etc. Although RGB colors are generally discussed in this disclosure, the embodiments described herein are not limited to using red, green, and blue as primary colors. Other colors may also be used as primary colors for the near-eye display system 600. In some embodiments, a display panel according to one embodiment may use more than three primary colors. Each pixel in light source 642 may include three sub-pixels, which include a red micro-LED, a green micro-LED, and a blue micro-LED. Semiconductor LEDs typically include an active light-emitting layer within a plurality of semiconductor material layers. The plurality of semiconductor material layers may include different compound materials or the same substrate material with different dopants and / or different doping densities. For example, the plurality of semiconductor material layers may include an n-type material layer, an active region, and a p-type material layer, the active region including a heterostructure (e.g., one or more quantum wells). The plurality of semiconductor material layers may be grown on a surface of a substrate having a specific orientation. In some embodiments, in order to increase light extraction efficiency, a mesa comprising at least some of the plurality of semiconductor material layers may be formed.

[0088] The controller 620 can control image rendering operations of the image source component 610, such as the operation of the light source 642 and / or the projector 650. For example, the controller 620 can determine multiple instructions for the image source component 610 to render one or more display images. These instructions may include display instructions and scanning instructions. In some embodiments, display instructions may include image files (e.g., bitmap files). Display instructions may be received, for example, from a console (e.g., as mentioned above). Figure 1 The console 110 described herein. The image source component 610 can use scan instructions to generate image light. The scan instructions may specify, for example, the type of image light source (e.g., monochrome or multicolor), scan rate, orientation of the scanning device, one or more illumination parameters, or any combination thereof. The controller 620 may include a combination of hardware, software, and / or firmware, not shown herein so as not to obscure other aspects of this disclosure.

[0089] In some embodiments, controller 620 may be a graphics processing unit (GPU) of a display device. In other embodiments, controller 620 may be other types of processors. Operations performed by controller 620 may include acquiring content for display and dividing the content into multiple discrete portions. Controller 620 may provide light source 642 with multiple scanning instructions, which include addresses corresponding to individual source elements of light source 642 and / or electrical biases applied to those individual source elements. Controller 620 may instruct light source 642 to sequentially present the multiple discrete portions using light emitters corresponding to one or more rows of pixels in an image (which is ultimately displayed to the user). Controller 620 may also instruct projector 650 to perform different light adjustments. For example, controller 620 may control projector 650 to scan the multiple discrete portions as described above. Figure 5B The waveguide display described (e.g., waveguide display 580) has different regions of coupling elements. In this respect, at the exit pupil of the waveguide display, the individual discrete parts are presented at different corresponding positions. Although the individual discrete parts are presented at different corresponding times, the presentation and scanning of these discrete parts occur fast enough that the user's eye can integrate the multiple different parts into a single image or a series of images.

[0090] Image processor 630 may be a general-purpose processor and / or one or more dedicated circuits for performing the various features described herein. In one embodiment, the general-purpose processor may be coupled to memory to execute software instructions that cause the processor to perform certain processes described herein. In another embodiment, image processor 630 may be one or more circuits dedicated to performing certain features. Although Figure 6 The image processor 630 is shown as a separate unit from the controller 620 and the drive circuit 644, but in other embodiments, the image processor 630 may be a subunit of the controller 620 or a subunit of the drive circuit 644. That is, in those embodiments, the controller 620 or the drive circuit 644 may perform various image processing functions of the image processor 630. The image processor 630 may also be referred to as an image processing circuit.

[0091] exist Figure 6In the example shown, the driving circuit 644 can drive the light source 642 based on data or multiple instructions (e.g., display instructions and scan instructions) sent by the controller 620 or the image processor 630. In one embodiment, the driving circuit 644 may include a circuit board connected to and mechanically holding the light emitters of the light source 642. The light source 642 can emit light according to one or more illumination parameters, which may be set by the controller 620 and potentially adjusted by the image processor 630 and the driving circuit 644. The light source 642 can use illumination parameters to generate light. Illumination parameters may include, for example, source wavelength, pulse rate, pulse amplitude, beam type (continuous or pulsed), one or more other parameters that may affect the emitted light, or any combination thereof. In some embodiments, the light generated by the light source 642 may include multiple beams of red, green, and blue light, or any combination of multiple beams of red, green, and blue light.

[0092] Projector 650 can perform a set of optical functions, such as focusing, combining, modulating, or scanning image light generated by light source 642. In some embodiments, projector 650 may include a combining component, a light modulating component, or a scanning mirror component. Projector 650 may include one or more optical components that optically modulate and potentially redirect the light from light source 642. An example of light modulating may include adjusting the light (e.g., amplifying, collimating, or correcting one or more optical errors (e.g., field curvature, chromatic aberration, etc.), some other light adjustment, or any combination thereof. The optical components of projector 650 may include, for example, lenses, mirrors, apertures, gratings, or any combination thereof.

[0093] Projector 650 can redirect image light through one or more of its reflective and / or refractive portions, projecting the image light toward a waveguide display at certain orientations. The location where the image light is redirected to the waveguide display can depend on the specific orientation of the one or more reflective and / or refractive portions. In some embodiments, projector 650 includes a single scanning mirror that scans in at least two dimensions. In other embodiments, projector 650 may include a plurality of scanning mirrors, each of which scans in a plurality of directions orthogonal to each other. Projector 650 may perform raster scanning (horizontally or vertically), bi-resonant scanning, or any combination thereof. In some embodiments, projector 650 may perform controlled vibrations at specific oscillation frequencies along the horizontal and / or vertical directions to scan along two dimensions and generate a two-dimensional projected image of the media presented to the user's eye. In other embodiments, projector 650 may include lenses or prisms that may function similarly or identically to the one or more scanning mirrors. In some embodiments, the image source component 610 may not include a projector, wherein light emitted by the light source 642 can be directly incident on the waveguide display.

[0094] The overall efficiency of a photonic integrated circuit or waveguide-based display (e.g., in augmented reality system 400, or in NED devices 500 or 550) can be the product of the efficiencies of multiple individual components, and can also depend on how these components are connected. For example, the overall efficiency η of the waveguide-based display in augmented reality system 400... tot The overall efficiency of the waveguide-based display can be determined based on the luminous efficiency of the image source 412, the optical coupling efficiency from the image source 412 through the projector optics 414 and the input coupler 430 to the combiner 415, and the output coupling efficiency of the output coupler 440.

[0095] η tot =η EQE ×η in ×η out (1)

[0096] Where, η EQE The external quantum efficiency of image source 412, η in It is the internal coupling efficiency of light from image source 412 to waveguide (e.g., substrate 420), and η out This refers to the external coupling efficiency of light from the waveguide through the output coupler 440 towards the user's eye. Therefore, it can be improved by increasing η. EQE η in η outOne or more of these factors can be used to improve the overall efficiency η of the waveguide-based display. tot .

[0097] An optical coupler (e.g., input coupler 430 or coupler 532) that couples light emitted from a light source to a waveguide may include, for example, a grating, a lens, a microlens, or a prism. In some embodiments, light from a small light source (e.g., a micro-LED) can be coupled directly (e.g., end-to-end) from the light source to the waveguide without using an optical coupler. In some embodiments, the optical coupler (e.g., a lens or a parabolic reflector) can be fabricated on the light source.

[0098] The aforementioned light source, image source, or other display may include one or more LEDs. For example, each pixel in the display may include three sub-pixels, which include a red micro-LED, a green micro-LED, and a blue micro-LED. Semiconductor light-emitting diodes typically include an active light-emitting layer within multiple semiconductor material layers. These multiple semiconductor material layers may include different compound materials, or the same substrate material with different dopants and / or different doping densities. For example, these multiple semiconductor material layers typically include an n-type material layer, an active layer, and a p-type material layer, and the active layer may include multiple heterostructures (e.g., one or more quantum wells). These multiple semiconductor material layers may be grown on a surface of a substrate with a specific orientation.

[0099] Photons can be generated in a semiconductor LED (e.g., a micro-LED) with a certain internal quantum efficiency through the recombination of electrons and holes within an active layer (e.g., the active layer comprising one or more semiconductor layers). The generated light can then be extracted from the LED in a specific direction or within a specific solid angle. The ratio of the number of emitted photons extracted from the LED to the number of electrons passing through the LED is called the external quantum efficiency, which describes how efficiently the LED converts injected electrons into photons extracted from the device. The external quantum efficiency can be proportional to the injection efficiency, internal quantum efficiency, and extraction efficiency. The injection efficiency refers to the proportion of electrons injected into the active region that pass through the device. The extraction efficiency is the proportion of photons generated in the active region that escape from the device. Improving the internal and external quantum efficiencies can be challenging for LEDs, especially for micro-LEDs with reduced physical dimensions. In some embodiments, to increase the light extraction efficiency, mesas comprising at least some of the plurality of semiconductor material layers can be formed.

[0100] Figure 7AAn example of an LED 700 with a vertical mesa structure is shown. LED 700 can be a light emitter in light sources 510, 540, or 642. LED 700 can be a micro-LED made of inorganic materials (e.g., multiple layers of semiconductor materials). Layered semiconductor light-emitting devices can include multiple layers of III-V semiconductor materials. III-V semiconductor materials can include one or more Group III elements combined with Group V elements, such as aluminum (Al), gallium (Ga), or indium (In), and Group V elements such as nitrogen (N), phosphorus (P), arsenic (As), or antimony (Sb). When the Group V element in a III-V semiconductor material includes nitrogen, the III-V semiconductor material is referred to as a Group III nitride material. The layered semiconductor light-emitting device can be fabricated by growing multiple epitaxial layers on a substrate using techniques such as vapor-phase epitaxy (VPE), liquid-phase epitaxy (LPE), molecular beam epitaxy (MBE), or metal-organic chemical vapor deposition (MOCVD). For example, multiple semiconductor material layers can be grown layer by layer on a substrate with a specific lattice orientation (e.g., polar orientation, non-polar orientation, or semi-polar orientation). This substrate can be, for example, a GaN substrate, a gallium arsenide (GaAs) substrate, or a gallium phosphide (GaP) substrate, or a substrate including but not limited to sapphire, silicon carbide, silicon, zinc oxide, boron nitride, lithium aluminate, lithium niobate, germanium, aluminum nitride, lithium gallium oxide, partially substituted spinel, or a quaternary tetragonal oxide sharing a β-LiAlO2 structure, wherein the substrate can be cleaved in a specific direction to expose specific planes as growth surfaces.

[0101] exist Figure 7AIn the example shown, LED 700 may include a substrate 710, which may include, for example, a sapphire substrate or a GaN substrate. A semiconductor layer 720 may be grown on the substrate 710. The semiconductor layer 720 may include a III-V material (e.g., GaN) and may be p-doped (e.g., doped with magnesium (Mg), calcium (Ca), zinc (Zn), or barium (Be)) or n-doped (e.g., doped with silicon (Si) or germanium (Ge)). One or more active layers 730 may be grown on the semiconductor layer 720 to form active regions. The active layer 730 may include a III-V material layer, such as one or more indium gallium nitride (InGaN) layers, one or more AlGaInP layers, and / or one or more GaN layers, which may form one or more heterostructures, such as one or more quantum wells or MQWs. A semiconductor layer 740 may be grown on the active layer 730. Semiconductor layer 740 may comprise a III-V group material (e.g., GaN) and may be p-doped (e.g., doped with Mg, Ca, Zn, or Be) or n-doped (e.g., doped with Si or Ge). One of semiconductor layers 720 and 740 may be a p-type layer, and the other may be an n-type layer. Semiconductor layers 720 and 740 sandwich an active layer 730 to form a light-emitting region. For example, LED 700 may comprise an InGaN layer located between a magnesium-doped p-type GaN layer and an n-type GaN layer doped with silicon or oxygen. In some embodiments, LED 700 may comprise an AlGaInP layer located between a zinc-doped or magnesium-doped p-type AlGaInP layer and an n-type AlGaInP layer doped with selenium, silicon, or tellurium.

[0102] In some embodiments, an electron blocking layer (EBL) may be grown. Figure 7A (Not shown in the image) to form a layer between the active layer 730 and at least one of the semiconductor layer 720 or semiconductor layer 740. EBL can reduce electron leakage current and improve the efficiency of the LED. In some embodiments, a heavily doped semiconductor layer 750, for example, P, can be formed on the semiconductor layer 740. + Semiconductor layer or P ++ A semiconductor layer, and this heavily doped semiconductor layer can be used as a contact layer for forming ohmic contacts and reducing the contact impedance of the device. In some embodiments, a conductive layer 760 may be formed on the heavily doped semiconductor layer 750. The conductive layer 760 may, for example, comprise an indium tin oxide (ITO) or an Al / nickel (Ni) / gold (Au) film. In one example, the conductive layer 760 may comprise a transparent ITO layer.

[0103] To contact the semiconductor layer 720 (e.g., an n-type GaN layer) and to more effectively extract light emitted from the active layer 730 from the LED 700, multiple semiconductor material layers (including heavily doped semiconductor layer 750, semiconductor layer 740, active layer 730, and semiconductor layer 720) can be etched to expose the semiconductor layer 720 and form a mesa structure including layers 720 to 760. This mesa structure can confine charge carriers within the device. Etching the mesa structure allows the formation of multiple mesa sidewalls 732 orthogonal to these growth planes. A passivation layer 770 can be formed on the multiple mesa sidewalls 732 of the mesa structure. The passivation layer 770 may include an oxide layer (e.g., a silicon dioxide (SiO2) layer) and can serve as a reflector to reflect the emitted light away from the LED 700. A contact layer 780 may be formed on the semiconductor layer 720. This contact layer may include a metal layer, such as Al, Au, Ni, titanium (Ti), or any combination thereof, and may serve as one electrode of the LED 700. Furthermore, another contact layer 790, such as an Al / Ni / Au metal layer, may be formed on the conductive layer 760, and this other contact layer 790 may serve as another electrode of the LED 700.

[0104] When a voltage signal is applied to contact layers 780 and 790, electrons and holes can recombine in the active layer 730, where recombination can induce photon emission. The wavelength and energy of the emitted photons can depend on the band gap between the valence and conduction bands in the active layer 730. For example, an InGaN active layer can emit green or blue light, an aluminum gallium nitride (AlGaN) active layer can emit blue to ultraviolet light, and an AlGaInP active layer can emit red, orange, yellow, or green light. The emitted photons can be reflected by the passivation layer 770 and can exit the LED 700 from the top (e.g., conductive layer 760 and contact layer 790) or the bottom (e.g., substrate 710).

[0105] In some embodiments, the LED 700 may include one or more other components (e.g., lenses) on its light-emitting surface (e.g., substrate 710) to focus or collimate the emitted light or couple the emitted light into a waveguide. In some embodiments, the LED may include a mesa of another shape, such as planar, conical, semi-parabolic, or parabolic, and the base of the mesa may be circular, rectangular, hexagonal, or triangular. For example, the LED may include a mesa with a curved shape (e.g., parabolic shape) and / or a non-curved shape (e.g., conical shape). The mesa may be truncated or non-truncated.

[0106] Figure 7BThis is a cross-sectional view of an example LED 705 with a parabolic mesa structure. Similar to LED 700, LED 705 may include multiple semiconductor material layers, such as multiple III-V semiconductor material layers. These semiconductor material layers may be epitaxially grown on a substrate 715, such as a GaN substrate or a sapphire substrate. For example, a semiconductor layer 725 may be grown on the substrate 715. Semiconductor layer 725 may include a III-V material (e.g., GaN) and may be p-doped (e.g., doped with Mg, Ca, Zn, or Be) or n-doped (e.g., doped with Si or Ge). One or more active layers 735 may be grown on semiconductor layer 725. Active layer 735 may include a III-V material layer, such as one or more InGaN layers, one or more AlGaInP layers, and / or one or more GaN layers, which may form one or more heterostructures, such as one or more quantum wells. Semiconductor layer 745 may be grown on active layer 735. Semiconductor layer 745 may comprise a III-V group material (e.g., GaN) and may be p-doped (e.g., doped with Mg, Ca, Zn, or Be) or n-doped (e.g., doped with Si or Ge). One of semiconductor layer 725 and semiconductor layer 745 may be a p-type layer and the other may be an n-type layer.

[0107] To make contact with semiconductor layer 725 (e.g., an n-type GaN layer) and to more effectively extract light emitted from active layer 735 from LED 705, multiple semiconductor layers can be etched to expose semiconductor layer 725 and form a mesa structure comprising layers 725 to 745. This mesa structure can confine charge carriers within the injection region of the device. Etching this mesa structure can result in the formation of multiple mesa sidewalls (also referred to herein as facets), which may be non-parallel to multiple growth planes (which are associated with the crystal growth of layers 725 to 745), or in some cases, these mesa sidewalls may be orthogonal to these growth planes.

[0108] like Figure 7BAs shown, LED 705 may have a mesa structure including a flat top. A dielectric layer 775 (e.g., SiO2 or silicon nitride (SiNx)) may be formed on multiple facets of the mesa structure. In some embodiments, dielectric layer 775 may include multiple dielectric material layers. In some embodiments, a metal layer 795 may be formed on dielectric layer 775. Metal layer 795 may include one or more metals or metal alloys, such as Al, silver (Ag), Au, platinum (Pt), Ti, copper (Cu), or any combination thereof. Dielectric layer 775 and metal layer 795 may form a mesa reflector that can reflect light emitted from active layer 735 toward substrate 715. In some embodiments, the mesa reflector may be parabolic in shape to serve as a parabolic reflector that can at least partially collimate the emitted light.

[0109] Electrical contacts 765 can be formed on semiconductor layer 745, and electrical contacts 785 can be formed on semiconductor layer 725 to serve as multiple electrodes. Both electrical contacts 765 and 785 can include conductive materials such as Al, Au, Pt, Ag, Ni, Ti, Cu, or any combination thereof (e.g., Ag / Pt / Au or Al / Ni / Au), and these electrical contacts can serve as multiple electrodes for LED 705. Figure 7B In the example shown, electrical contact 785 can be an n-contact, and electrical contact 765 can be a p-contact. Electrical contact 765 and semiconductor layer 745 (e.g., a p-type semiconductor layer) can be formed to reflect light emitted from active layer 735 back to a back reflector of substrate 715. In some embodiments, electrical contact 765 and metal layer 795 comprise one or more of the same materials and can be formed using the same process. In some embodiments, an additional conductive layer (not shown) may be included between electrical contacts 765 and 785 and these semiconductor layers as an intermediate conductive layer.

[0110] When a voltage signal is applied to electrical contacts 765 and 785, electrons and holes can recombine in the active layer 735. This recombination can induce photon emission, thus producing light. The wavelength and energy of the emitted photons can depend on the band gap between the valence and conduction bands in the active layer 735. For example, an InGaN active layer can emit green or blue light, while an AlGaInP active layer can emit red, orange, yellow, or green light. The emitted photons can propagate in many different directions and can be reflected by mesa reflectors and / or back reflectors, and can, for example, from... Figure 7B The bottom side (e.g., substrate 715) shown is away from LED 705. One or more other auxiliary optical components, such as lenses or gratings, may be formed on the light-emitting surface (e.g., substrate 715) to focus or collimate the emitted light and / or couple the emitted light into the waveguide.

[0111] When forming (e.g., etching) a mesa structure, the multiple facets of the mesa structure (e.g., multiple mesa sidewalls 732) may contain defects that can reduce the internal quantum efficiency of the LED. These defects include, for example, unsatisfied bonds, chemical contamination, and structural damage (e.g., structural damage during dry etching). For example, at these facets, the atomic lattice structure of multiple semiconductor layers may abruptly end, where some atoms of the semiconductor material may lack multiple neighbors to which multiple bonds can attach. This results in "dangling bonds," characterized by unpaired valence electrons. These dangling bonds generate multiple energy levels that would not normally exist within the band gap of the semiconductor material, leading to nonradiative electron-hole recombination at or near multiple facets of the mesa structure. Therefore, these defects may become multiple recombination centers, where electrons and holes may be confined until they nonradiatively recombine.

[0112] As described above, the internal quantum efficiency is the ratio of radiative electron-hole recombination in the active region where photons are emitted. The internal quantum efficiency of an LED depends on the relative rates of competing radiative (light-generating) recombination and non-radiative (loss) recombination occurring in the active region of the LED. Non-radiative recombination processes in the active region can include Shockley-Reid-Hall (SRH) recombination at defect sites and eeh / ehh Auger recombination, which is a non-radiative process involving three charge carriers. The internal quantum efficiency of an LED can be determined by the following equation:

[0113]

[0114] Where A is the rate of SRH recombination, B is the rate of bimolecular (radiative) recombination, and C is the rate of Auger recombination, and N is the charge carrier density (i.e., charge carrier concentration) in the active region.

[0115] Figure 8 The relationship between the light emission power and current density of a light-emitting diode is shown. For example... Figure 8 As shown in curve 810, the light emission power of micro-LED devices may be lower when the current density (and therefore the charge carrier density N) is low, where, according to equation (2), the relatively high nonradiative SRH recombination can lead to a lower external quantum efficiency when the charge carrier density N is low. Figure 8 As shown in curve 820, the optical emission power can increase with increasing current density (and therefore charge carrier density N). This is because, according to equation (2), when the charge carrier density N is high, radiative recombination can occur at a higher rate (∝N) than nonradiative SRH recombination.2 (Increase.) For example... Figure 8 As shown in curve 830, as the current density further increases, the optical emission power can increase at a slower rate, and therefore the external quantum efficiency may also decrease. This is because, for example, according to equation (2), when the charge carrier density N is sufficiently high, nonradiative Auger recombination can occur at a rate higher than radiative recombination (∝N). 2 Higher speed (∝N) 3 )Increase.

[0116] Auger recombination is a nonradiative process involving three charge carriers. Auger recombination can be a major cause of efficiency degradation and can be direct or indirect. For example, direct Auger recombination occurs when electrons and holes recombine, but it does not produce light; instead, either electrons are lifted higher in the conduction band or holes are pushed deeper in the valence band. For a given injection current density J, the efficiency degradation can be reduced by decreasing the charge carrier density N in the active region, which can be written as:

[0117] J = qd eff (AN+BN 2 +CN 3 (3)

[0118] Where, d eff The effective thickness of the active region is d. Therefore, according to equation (3), for a given injection current density, the effect of Auger recombination can be reduced by decreasing the charge carrier density N, thereby improving the IQE of the LED. Reducing the charge carrier density can be achieved by increasing the effective thickness d of the active region. eff This can be achieved by, for example, growing multiple quantum wells (MQWs). Alternatively, the effective thickness of the active region can be increased by using an active region comprising a single thick double heterostructure (DH).

[0119] One factor affecting the effective thickness of the active region is the internal field E present in the quantum well. qw (For example, strain-induced internal fields). Internal field E qw This can localize charge carriers and reduce the overlap integral between multiple carrier wavefunctions, potentially decreasing the radiative efficiency of LEDs. Some LEDs, including heterostructures (e.g., quantum wells), can possess strong internal strain-induced piezoelectric fields in the carrier transport direction. These strain-induced internal fields can shift electron and hole energy levels (thus altering the band gap) and move electrons and holes to opposite sides of the quantum well, thereby reducing spatial electron-hole overlap and decreasing radiative recombination efficiency, and thus lowering the internal quantum efficiency of the LED.

[0120] While Auger recombination due to high current density (and high charge carrier density) may be an inherent process dependent on material properties, nonradiative SRH recombination depends on material characteristics and quality, such as the defect density in the active region. (See above regarding...) Figure 7A and Figure 7B As described, LEDs can be fabricated by etching mesa structures within multiple active layers to confine charge carriers within the device's injection region and expose the n-type material beneath these active layers for electrical contact. Etching the mesa structures allows for the formation of multiple mesa sidewalls orthogonal to the growth plane. As described above, due to this etching, the active region near the exposed sidewalls may have a higher defect density, such as dislocations, pores, grain boundaries, vacancies, inclusions, etc. These defects can introduce energy states with deep or shallow energy levels into the band gap. Charge carriers may be trapped in these energy states until they nonradiatively recombine. Therefore, the active region near these sidewalls can have a higher SRH recombination rate compared to the bulk region farther from these exposed sidewalls.

[0121] Parameters that can influence the effect of nonradiative surface recombination on LED efficiency include, for example, the surface recombination velocity (SRV) S, the carrier diffusion coefficient (diffusivity) D, and the carrier lifetime τ. The high recombination velocity near multiple sidewall surfaces, due to high defect density, can depend on the number of excess carriers (especially minority carriers) in that region. A high recombination velocity can deplete carriers in that region. Depletion of carriers in that region can lead to carrier diffusion from surrounding regions with higher carrier concentrations into that region. Therefore, the amount of surface recombination can be limited by the surface recombination velocity S (at which carriers move to the region near the multiple sidewall surfaces). The carrier lifetime τ is the average time a carrier can remain in an excited state after electron-hole generation and before recombination with another carrier. The carrier lifetime τ typically depends on the carrier concentration and recombination velocity in the active region. The carrier diffusion coefficient (diffusivity) D of the material, along with the carrier lifetime τ, can determine the carrier diffusion length. The carrier diffusion length is the average distance a carrier travels from the point of generation until it recombines. This carrier diffusion length L characterizes the width of the region adjacent to the sidewall surface of the active region, where surface recombination significantly contributes to carrier loss. Charge carriers injected into or diffused into multiple regions (within a few carrier diffusion lengths from the sidewall surface) may experience higher SRH recombination rates.

[0122] Higher current density (e.g., in amperes / cm²) 2The higher current density (in units) can be associated with a lower surface recombination rate because surface defects may become increasingly saturated at higher carrier densities. Therefore, the surface recombination rate can be reduced by increasing the current density. Furthermore, the carrier diffusion length of a given material can vary with the current density at which the device operates. However, LEDs typically cannot operate at high current densities. Increasing current injection can also lead to a decrease in the efficiency of micro-LEDs due to the higher Auger recombination rate and lower conversion efficiency at higher temperatures (which is caused by self-heating at higher current densities).

[0123] For conventional large-area LEDs used in lighting and backlighting applications (e.g., those with an area of ​​approximately 0.1 mm), 2 Approximately 1mm 2 In a micro-LED (with a lateral device area), the sidewall surfaces are located at the far end of the device. Devices can be designed such that little or no current is injected into the region within the minority carrier diffusion length of the mesa sidewalls, resulting in a low sidewall surface area to volume ratio and a low overall SRH recombination rate. However, in micro-LEDs, the LED size is reduced to a value comparable to or on the same order of magnitude as the minority carrier diffusion length, and because a large portion of the total active region may fall within the minority carrier diffusion length from the LED sidewall surfaces, the increased surface area to volume ratio can lead to a high carrier surface recombination rate. Therefore, more injected carriers will experience a higher SRH recombination rate. This can cause the LED leakage current to increase with decreasing LED size, and the LED efficiency to decrease with decreasing LED size, and / or the peak efficiency operating current to increase with decreasing LED size. For example, for a first LED with a 100 μm × 100 μm × 2 μm mesa, the sidewall surface area to volume ratio can be approximately 0.04. However, for the second LED with a 5μm × 5μm × 2μm mesa, the ratio of sidewall surface area to volume can be approximately 0.8, which is about 20 times higher than that of the first LED. Therefore, under similar surface defect densities, the SRH recombination rate of the second LED can also be about 20 times higher. Consequently, the efficiency of the second LED may be significantly reduced.

[0124] Compared to some other light-emitting materials (e.g., group III nitride materials), AlGaInP materials can exhibit high surface recombination rates and minority carrier diffusion lengths. For example, red AlGaInP LEDs can typically achieve high light-emitting rates at reduced carrier concentrations (e.g., approximately 10⁻⁶). 17 cm -3 Up to 10 18 cm -3Operating under these conditions, it can therefore have a relatively long carrier lifetime τ. The carrier diffusion rate D in the active region of the undoped quantum well of a red AlGaInPLED can also be quite large. Therefore, in some devices, the carrier diffusion length is... For example, the surface area can be from about 10 μm to 25 μm or longer. Furthermore, the surface recombination rate of AlGaInP materials can be an order of magnitude higher than that of group III nitride materials. Therefore, compared to LEDs made of group III nitride materials (e.g., blue and green LEDs made of GaN), the internal and external quantum efficiencies of AlGaInP-based red LEDs can decrease even more significantly as the device size decreases.

[0125] Figure 9 The surface recombination rates of various III-V semiconductor materials are shown. Figure 9 The multiple bars 910 show the range of SRV values ​​for various reported group III-V semiconductor materials, while the symbols 920 on the bars 910 indicate the common SRV or average SRV. Box 930 shows the general trend of surface recombination rate as a function of the material band gap (i.e., bandgap). Figure 9 As shown, the SRV(S~10) in InP 5 (cm / s) or SRV in GaN (S less than about 0.5 × 10 cm / s) 5 Compared to (cm / s), SRV (S~10) in GaAs 6 The surface recombination rate of AlGaInP materials is relatively high (cm / s). 6 (cm / s) can be at least higher than the surface recombination rate of group III nitride materials (e.g., <10 cm / s). 5 The SRV is an order of magnitude higher than that of aluminum alloys (e.g., AlGaInP). Furthermore, in aluminum-containing alloys, the SRV can increase significantly with the Al fraction. For example, the SRV can increase from (Al... 0.1 Ga 0.9 ) 0.5 In 0.5 P approximately 10 5 cm / s increased to Al 0.51 In 0.49 P approximately 10 6 cm / s.

[0126] Furthermore, nitride LEDs can operate at much higher non-equilibrium carrier concentrations compared to phosphide LEDs, resulting in a significantly shorter carrier lifetime. Consequently, the carrier diffusion length in the active region of a group III nitride LED is significantly shorter than that of a phosphide LED. In this respect, phosphide LEDs (e.g., AlGaInP-based red micro-LEDs) can combine higher SRV with a longer carrier diffusion length, and therefore can exhibit much higher surface recombination and a much higher efficiency degradation than group III nitride LEDs.

[0127] Figure 10A Examples of external quantum efficiency versus current density for different AlGaInP red LEDs with different physical dimensions are shown. Curves 1010, 1020, 1030, 1040, 1050, and 1060 represent the external quantum efficiency of LEDs with lateral dimensions of 15 × 15 μm. 2 22×22μm 2 50×50μm 2 100×100μm 2 150×150μm 2 and 350×350μm 2 The EQE of AlGaInP red LED varies with current density. Figure 10A The results show that EQE depends on LED size. At the same current density, a larger LED exhibits a higher EQE than a smaller LED. Figure 10A Curves 1010, 1020, and 1030 in the figure also show that when the lateral dimension of the LED is, for example, greater than about 100 × 100 μm... 2 At the same time, the EQE of LEDs can be similar.

[0128] Figure 10B Examples of current-voltage (IV) curves for different AlGaInP red LEDs with different physical dimensions are shown. Curves 1012, 1022, 1032, 1042, 1052, and 1062 show LEDs with lateral dimensions of 15 × 15 μm. 2 22×22μm 2 50×50μm 2 100×100μm 2 150×150μm 2 and 350×350μm 2 The IV curve of an AlGaInP red LED. At the same current, the series resistance and forward voltage of the LED can increase as the chip size decreases. Figure 10B It was shown that even when the chip size was reduced to approximately 15×15μm 2At the same time, it does not significantly reduce the forward and reverse leakage current characteristics. This suggests that the lower EQE of small LEDs may not be caused by a decrease in current injection efficiency (which is caused by an increase in leakage current). Figure 10A and Figure 10B This suggests that the lower EQE of small LEDs may be mainly caused by non-radiative surface recombination.

[0129] Non-radiative surface recombination can be reduced by using suitable dielectric materials to passivate the surface, such as SiO2 and SiN. x Alternatively, aluminum oxide (Al₂O₃) can be used. SRV can be reduced by chemically etching away heavily defective surface material. Alternatively or additionally, surface recombination can be reduced by decreasing lateral carrier mobility. For example, lateral carrier mobility can be reduced by using ion implantation to disrupt the semiconductor lattice outside the central portion of the micro-LED. Ion implantation reduces the number of electrons reaching the sidewall surfaces of the micro-LED, and thus reduces the amount of surface recombination. Attacking semiconductor materials with high-energy ions can have two effects. First, the conductivity of the semiconductor lattice may decrease, so the current does not diffuse through the entire structure in all directions, but instead passes vertically through the central region in a funnel shape. Second, the diffusivity in the attacked region is reduced, preventing carriers from moving laterally very far. Therefore, both the diffusivity D and the carrier diffusion length L can be reduced by ion implantation.

[0130] Alternatively or additionally, the lateral carrier mobility can be reduced by using quantum well intermixing to alter the composition of multiple regions outside the central portion of the semiconductor layer within the micro-LED. Quantum well intermixing can be used to increase the band gap in the outer regions of the semiconductor layer by implanting ions into these outer regions and subsequently annealing them to mix the ions with atoms already present in those regions. Therefore, quantum well intermixing can also reduce the number of electrons reaching the sidewall surfaces of the micro-LED, and thus reduce the amount of surface recombination.

[0131] Despite these efforts to reduce surface recombination, the efficiency of micro-LEDs typically decreases as the mesa size shrinks due to non-radiative surface recombination, while the peak efficiency operating current density typically increases. The overall electro-optical power conversion efficiency of the device (known as wall-plug efficiency) can be low.

[0132] According to certain embodiments, AlGaInP red micro-LEDs can include various structures and material compositions such that current can be confined to a small local region where radiative recombination can occur. This local region can have a lateral linear dimension of approximately 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 8, 1 / 10, or smaller than the lateral linear dimension of the micro-LED (e.g., the lateral linear dimension of the mesa structure of the micro-LED). Therefore, carrier diffusion from the active region to the sidewall regions can be reduced, and thus non-radiative surface recombination in the sidewall regions can be reduced, thereby improving quantum efficiency. In some embodiments, current localization and current confinement can be achieved, for example, through local breakdown or other current holes in a barrier layer for confining the current injection region, and a lightly p-doped active layer for suppressing lateral carrier diffusion to the surface region, or any combination thereof.

[0133] In some embodiments, the barrier layer may include, for example, a thyristor, a tunnel junction, a heterojunction, etc. The barrier layer may be located close to the active region, for example, within a certain carrier diffusion length or one carrier diffusion length from the active region. Local contacts on the barrier layer (e.g., pointed p-contacts, submicron p-contacts, or filaments), when properly biased, can generate a high electric field in a localized region of the barrier layer, causing localized breakdown of the barrier layer, allowing current to be injected into the active region through the localized breakdown region. The localized breakdown region can serve as a current aperture to confine current injection to a small area. In some embodiments, current injection can be localized by ion implantation, etching, oxidation, etc.

[0134] Lightly p-doped active layers can suppress lateral diffusion of charge carriers to the surface region, allowing charge carriers injected into the active region through small current holes to be retained within a small area of ​​the active layer. For example, light p-doping in the active region can form a hole depletion region, which reduces hole diffusion to the sidewall regions. Light p-doping in the active region can also move trapped states further away from the Fermi level. Therefore, the hole concentration at the sidewalls can be reduced, and thus surface recombination can be decreased. Current localization in the active region can induce self-heating of the semiconductor, which can further reduce carrier diffusion to the sidewalls of the active region with increasing temperature. Furthermore, due to current confinement and localization, light emission will occur in localized regions, which can promote efficient light extraction and external coupling from the micro-LED. Therefore, the overall external quantum efficiency of the micro-LED can be significantly improved.

[0135] Figure 11AAn example of a micro-LED 1100 is shown. The micro-LED 1100 can be an example of an LED 700. The micro-LED 1100 may include an n-type semiconductor layer 1150, such as an aluminum indium phosphide (AlInP) layer or an AlGaInP layer doped with selenium, silicon, or tellurium. The n-type semiconductor layer 1150 may, for example, be grown on a GaAs substrate or an aluminum gallium arsenide (AlGaAs) layer. One or more active layers 1140 may be grown on the n-type semiconductor layer 1150 to form active regions. For example, the plurality of active layers 1140 may include one or more gallium indium phosphide (GaInP) layers and one or more AlGaInP layers, which may form one or more heterostructures, such as one or more quantum wells or MQWs, wherein the GaInP layer may be a quantum well and the AlGaInP layer may be a quantum barrier layer. Intrinsic layers 1130 may be formed on these active layers 1140. Intrinsic layer 1130 can be an electron blocking layer, a cladding layer, or a separate confinement layer, and may include, for example, an intrinsic AlGaInP layer. Intrinsic layer 1130 can confine charge carriers and reduce electron leakage current to improve LED efficiency. A p-type layer 1120 can be formed on intrinsic layer 1130. p-type layer 1120 may include, for example, an AlInP or AlGaInP layer doped with zinc or magnesium. A p-type layer 1110 can be formed on p-type layer 1120. p-type layer 1110 may include, for example, a GaP layer, GaInP layer, AlInP layer, or AlGaInP layer doped with zinc or magnesium. p-type layer 1110 may be heavily doped and can be used as a contact layer for forming ohmic contacts with metal electrodes and reducing the contact impedance of the device. A p-contact layer 1160 can be formed on p-type layer 1110 as an anode. The p-contact layer 1160 may, for example, comprise a metal layer (e.g., Al, Au, Ni, Ti, or any combination thereof), or indium tin oxide (ITO), or an Al / Ni / Au film. Passivation layers 1190 may be formed on multiple sidewalls of the micro-LED 1100. Passivation layers 1190 may comprise an oxide layer (e.g., a SiO2 layer) or another dielectric layer, and may function as a reflector to reflect emitted light out of the micro-LED 1100 as described above. Although Figure 11A The vertical mezzanine structure is shown, but the micro-LED 1100 can include different mezzanine shapes, such as conical mezzanine shapes, parabolic mezzanine shapes, inwardly inclined mezzanine shapes, or outwardly inclined mezzanine shapes.

[0136] When the p-type layer 1110 (e.g., through p-contact layer 1160) and n-type semiconductor layer 1150 (e.g., through p-contact layer 1160) are connected to the p-type semiconductor layer 1110 (e.g., through p-contact layer 1160) and the n-type semiconductor layer 1150 (e.g., through p-contact layer 1160) are connected to the p-type semiconductor layer 1110 (e.g., through p-contact layer 1150) and the n-type semiconductor layer 1150 (e.g., through p-contact layer 1160) are connected to the p-type semiconductor layer 1110 (e.g., through p-contact layer 1160) and the n-type semiconductor layer 1150 (e.g., through p-contact layer 1160) are connected to Figure 11AWhen a voltage signal is applied to the cathode (not shown), electrons and holes can be injected into the active layer 1140 and recombine within it, where recombination can induce photon emission. The emitted photons can be reflected by the passivation layer 1190 and exit the micro-LED 1100 from the top (e.g., the p-contact layer 1160 side). As described above, the internal and external quantum efficiencies of the micro-LED 1100 may be low, at least due to losses caused by non-radiative surface recombination.

[0137] Figure 11BAn example of a micro-LED 1105 with improved external quantum efficiency according to certain embodiments is shown. Like the micro-LED 1100, the micro-LED 1105 may include a mesa structure. The mesa structure of the micro-LED 1105 may have lateral linear dimensions of less than about 100 μm, less than about 50 μm, less than about 20 μm, less than about 10 μm, less than about 5 μm, less than about 3 μm, less than about 2 μm, or smaller. The mesa structure of the micro-LED 1105 may include, for example, an n-type layer 1165 grown on a GaAs substrate or an AlGaAs layer. The n-type layer 1165 may, for example, include an AlInP layer or an AlGaInP layer doped with selenium, silicon, or tellurium. One or more active layers 1155 may be grown on the n-type layer 1165 to form an active region. Multiple active layers 1155 may include, for example, one or more GaInP layers (e.g., quantum well layers) and one or more AlGaInP layers (e.g., barrier layers), which may form one or more heterostructures, such as one or more quantum wells or MQWs. Optionally, a layer 1145 may be formed on these active layers 1155. Layer 1145 may be an electron blocking layer, a cladding layer, or a separate confinement layer, and may include, for example, an intrinsic layer or a p-type AlGaInP layer. Layer 1145 may confine charge carriers within the active region and reduce electron leakage current to improve the efficiency of the micro-LED 1105. A p-type layer 1135 may be formed on layer 1145. The p-type layer 1135 may, for example, include an AlInP or AlGaInP layer doped with zinc or magnesium. A thin n-type layer 1125 may be formed on the p-type layer 1135. The n-type layer 1125 may, for example, comprise an AlInP layer or an AlGaInP layer doped with selenium, silicon, or tellurium. A p-type layer 1115 may be formed on the n-type layer 1125. The p-type layer 1115 may, for example, comprise a GaP layer, a GaInP layer, an AlInP layer, or an AlGaInP layer doped with zinc or magnesium. The p-type layer 1115 may be heavily doped and may be used as a contact layer for forming ohmic contacts and reducing the contact impedance of the device. A p-contact layer 1175 may be formed on the p-type layer 1115 as an anode. The p-contact layer 1175 may, for example, comprise a metal layer (e.g., Al, Au, Ni, Ti, or any combination thereof), or an indium tin oxide (ITO) or Al / Ni / Au film. Passivation layers 1195 may be formed on multiple sidewalls of the micro-LED 1105. The passivation layer 1195 may include an oxide layer (e.g., a SiO2 layer) or another dielectric layer, and this passivation layer can be used as a reflector to reflect the emitted light out of the micro-LED 1105 as described above. Although Figure 11BThe vertical mezzanine structure is shown, but the micro-LED 1105 can include different mezzanine shapes, such as conical mezzanine shapes, parabolic mezzanine shapes, inwardly inclined mezzanine shapes, or outwardly inclined mezzanine shapes.

[0138] exist Figure 11B In the micro-LED 1105 shown, p-type layer 1115, n-type layer 1125, and p-type layer 1135 can form a barrier layer with a PNP structure. p-type layer 1115, n-type layer 1125, p-type layer 1135, and n-type layer 1165 can form a thyristor, which includes a pn junction between p-type layer 1115 and n-type layer 1125, an np junction between n-type layer 1125 and p-type layer 1135, and a pn junction (or pin structure) between p-type layer 1135 and n-type layer 1165. When a positive voltage signal is applied to the p-contact layer 1175 relative to n-type layer 1165, these pn junctions can be forward biased, while the np junction between n-type layer 1125 and p-type layer 1135 can be reverse biased. Therefore, the np junction can prevent current from flowing from p-type layer 1115 to n-type layer 1165. When a negative voltage signal is applied to the p-contact layer 1175 relative to the n-type layer 1165, the np junctions can be forward biased, while these pn junctions can be reverse biased to prevent current from flowing from the n-type layer 1165 to the p-type layer 1115. When a sufficiently high forward bias voltage signal is applied between the p-contact layer 1175 and the n-type layer 1165, the np junctions can be in a breakdown state to conduct current, allowing the thyristor to be in a forward conducting state. The thyristor can remain in the forward conducting state until the forward current drops below a threshold (referred to as the "holding current"). For example, the thyristor can be turned off when it is reverse biased.

[0139] like Figure 11B As shown, the p-contact layer 1175 may include a structure 1176, such as a pointed structure, a filamentary structure, a tapered tip structure, a V-shaped structure, or other submicron structures. In some embodiments, the structure 1176 may extend into the p-type layer 1115 to form a localized and tapered contact with the p-type layer 1115. Therefore, when a high voltage signal is applied to the p-contact layer 1175, a high electric field can be established in the region near the structure 1176 due to the small localized contact between the structure 1176 and the p-type layer 1115. This can cause breakdown in a small region of the np junction between the n-type layer 1125 and the p-type layer 1135 to turn on the thyristor. The small breakdown region can be localized near the structure 1176. This localized small breakdown region may have a smaller lateral linear dimension than the micro-LED 1105 (e.g., Figure 11BThe lateral linear dimension of the mesa structure shown is approximately 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 8, 1 / 10, or smaller. In this respect, charge carriers (e.g., holes) can be injected into the active layer 1155 only through localized small breakdown regions and can combine with electrons in small localized regions within the active layer 1155 to emit photons. The emitted photons can be reflected by the passivation layer 1195 and can exit the micro-LED 1105 from the top (e.g., p-contact layer 1175). Due to the lower mobility of holes compared to electrons, recombination centers in the active layer 1155 can be located close to the p-type layer 1135 (or layer 1145) and the localized small breakdown regions.

[0140] The micro-LED 1105 can be configured such that the distance between the barrier layer (or the np junction between the n-type layer 1125 and the p-type layer 1135) and the active layer 1155 can be less than some carrier diffusion length, such as less than about twice the carrier diffusion length, less than about one micrometer, or less than several hundred nanometers. Therefore, carriers (e.g., holes) injected into the active layer 1155 through localized small breakdown regions can diffuse only a short distance laterally without diffusing before recombinating with other carriers (e.g., electrons) to emit photons. In this respect, the injected carriers may not reach the sidewall regions of the active layer 1155, thus reducing non-radiative surface recombination.

[0141] As described above, other barrier layers or other techniques can also be used to achieve current localization. For example, tunnel junctions, heterojunctions, heterobars that induce band bending to form tunnel contacts, Schottky barriers, or other barrier layers can be used to achieve current localization. In some embodiments, current localization can be achieved using current holes formed, for example, through localized oxidation, localized ion implantation, localized etching, etc.

[0142] Figure 12An example of a micro-LED 1200 with improved external quantum efficiency according to certain embodiments is shown. The micro-LED 1200 may include a mesa structure having a lateral linear dimension of less than about 100 μm, less than about 50 μm, less than about 20 μm, less than about 10 μm, less than about 5 μm, less than about 3 μm, less than about 2 μm, or smaller. The mesa structure of the micro-LED 1200 may include an n-type layer 1260, such as an AlInP layer or AlGaInP layer doped with selenium, silicon, or tellurium. The n-type layer 1260 may be grown on, for example, a GaAs substrate or an AlGaAs layer. One or more active layers 1250 may be grown on the n-type layer 1260 to form an active region. Multiple active layers 1250 may include, for example, one or more GaInP layers (e.g., as quantum well layers) and one or more AlGaInP layers (e.g., as quantum barrier layers), which may form one or more heterostructures, such as one or more quantum wells or MQWs. Optionally, a layer 1240 may be formed on these active layers 1250. Layer 1240 may be an electron blocking layer, a cladding layer, or a separate confinement layer, and may include, for example, an intrinsic layer or a p-type AlGaInP layer. Layer 1240 may confine charge carriers within the active region and reduce electron leakage current to improve LED efficiency. A p-type layer 1230 may be formed on layer 1240. The p-type layer 1230 may, for example, include an AlInP or AlGaInP layer doped with zinc or magnesium. An n-type layer 1210 may be formed on the p-type layer 1230. The n-type layer 1210 may, for example, comprise an AlInP layer, GaP layer, GaInP layer, or AlGaInP layer doped with selenium, silicon, or tellurium. In some embodiments, the n-type layer 1210 and the p-type layer 1230 may be heavily doped, such that a thin depletion layer can be formed between the n-type layer 1210 and the p-type layer 1230 to form a tunnel junction 1220. In some embodiments, a tunnel barrier layer comprising a higher bandgap material may be formed between the n-type layer 1210 and the p-type layer 1230 to form the tunnel junction 1220. The tunnel junction 1220 may serve as a carrier barrier layer. An electrode layer 1205 may be formed on the n-type layer 1210. The electrode layer 1205 may, for example, comprise a metal layer (e.g., Al, Au, Ni, Ti, or any combination thereof), or an indium tin oxide (ITO) or Al / Ni / Au film. Passivation layers 1290 may be formed on multiple sidewalls of the micro-LED 1200. The passivation layer 1290 may include an oxide layer (e.g., a SiO2 layer) or another dielectric layer, and the passivation layer may be used as a reflector to reflect the emitted light out of the micro-LED 1200 as described above. Although Figure 12The vertical mezzanine structure is shown, but the micro-LED 1200 can include different mezzanine shapes, such as conical mezzanine shapes, parabolic mezzanine shapes, inwardly inclined mezzanine shapes, or outwardly inclined mezzanine shapes.

[0143] exist Figure 12 In the micro-LED 1200 shown, the n-type layer 1210, p-type layer 1230, and n-type layer 1260 can form an NPN structure. When the micro-LED 1200 is forward biased, the tunnel junction 1220 can be reverse biased. Reverse bias can generate a favorable band alignment for electron tunneling through the tunnel junction, which effectively injects holes into the active layer 1250. The electrode layer 1205 can include a structure 1206, such as a pointed structure, a filamentary structure, a tapered tip structure, a V-shaped structure, or another submicron structure. Therefore, when a high voltage signal is applied to the electrode layer 1205, a high electric field can be established in a local region near the structure 1206 due to the small local contact between the structure 1206 and the n-type layer 1210, which can generate a small local tunnel through the tunnel junction 1220. This local tunnel can have a smaller lateral linear dimension than the micro-LED 1200 (e.g., Figure 12 The lateral linear dimensions of the mesa structure shown are approximately 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 8, 1 / 10, or smaller. In this respect, charge carriers can be injected into the active layer 1250 only through small local tunnels and can recombine in local regions within the active layer 1250 to emit photons. The emitted photons can be reflected by the passivation layer 1290 and can exit the micro-LED 1200 from the top. Due to the lower mobility of holes compared to electrons, recombination centers in the active layer 1250 can be located close to the p-type layer 1230 (or layer 1240) and local tunnels.

[0144] The micro-LED 1200 can be configured such that the distance between the tunnel junction 1220 and the active layer 1250 can be less than some carrier diffusion length, such as less than about twice the carrier diffusion length, less than about one micrometer, or less than several hundred nanometers. For example, the p-type layer 1230 and layer 1240 can be thin. Therefore, carriers injected into the active layer 1250 through small local tunnels can diffuse only a short distance laterally before recombinating to emit photons. In this respect, the injected carriers may not reach the sidewall regions of the active layer 1250, thus reducing non-radiative surface recombination and improving quantum efficiency.

[0145] As described above, other techniques can also be used to localize carrier injection. For example, a heterojunction can be used as a barrier layer and can be combined with small electrode structures (e.g., structures 1176 or 1206) to confine the current to a small local region. In another example, a selective oxide layer with small unoxidized regions can be used to form a current hole. In another example, a current hole can be formed by selective ion implantation in a semiconductor layer. In yet another example, a current hole can be formed by selective etching in a semiconductor layer. The current hole can have a lateral linear dimension of about 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 8, 1 / 10, or smaller than the lateral linear dimension of the micro-LED (e.g., the lateral linear dimension of the mesa structure of a micro-LED).

[0146] Additionally or alternatively, in some embodiments, the quantum well layer and / or quantum barrier layer in the micro-LED (e.g., micro-LED 1105 or micro-LED 1200) may be p-doped. For example, the active layer (e.g., the quantum well layer) may be lightly p-doped with zinc or magnesium. In some embodiments, the active layer may be p-doped such that the integral of the acceptor concentration within the quantum well may be equal to or greater than the integral of the surface state density above the sidewall surface region of the quantum well. For example, the doping concentration may be about 10. 17 / cm 3 Or higher, for example, at approximately 5×10 17 / cm 3 With approximately 1×10 19 / cm 3 Between. Because the active region is uniformly lightly doped, the micro-LED may not experience performance degradation. The p-doped active layer can suppress the lateral diffusion of injected carriers (e.g., holes) into the mesa sidewall region, so that carriers injected into the active layer 1155 or 1250 through small current holes can be retained in a small region within the active layer 1155 or 1250. For example, light p-doping in the active layer 1155 or 1250 can form a hole depletion region in the active layer 1155 or 1250. This hole depletion region can reduce hole diffusion into the mesa sidewall region. P-doping can also advantageously alter the energy band in the active layer near the mesa sidewall region to reduce the carrier concentration at the mesa sidewall region, thereby reducing surface recombination. In some embodiments, the quantum barrier layer may also be p-doped to improve hole transport and increase hole injection efficiency in the quantum well.

[0147] Figure 13AAn example of an energy band diagram for an n-doped active layer is shown. n-doping can cause band bending of the conduction band 1310 and valence band 1320 at the sidewall surfaces of the n-doped active layer. Due to this band bending at the sidewall surfaces, the Fermi level 1330 at the sidewall surfaces can approach the trap state 1340 formed by defects. Therefore, the hole concentration at the sidewall surfaces of the n-doped active layer can be high, leading to high nonradiative surface recombination.

[0148] Figure 13B An example of an energy band diagram for a p-doped active layer is shown. P-doping can cause band bending at the sidewall surfaces of the p-doped active layer, affecting the conduction band 1360 and valence band 1370. Due to this band bending at the sidewall surfaces, the Fermi level 1380 at the sidewall surfaces can be further removed from the trap states 1390 formed by defects. Therefore, the hole concentration at the sidewall surfaces can be reduced, thus minimizing nonradiative surface recombination.

[0149] Due to localized carrier injection through small current holes and / or suppression of carrier diffusion in the active layer via p-doping, carriers can be confined to regions of the active layer away from multiple sidewall surfaces. Current localization in the active region can also induce self-heating of the semiconductor, which can further reduce carrier diffusion towards the sidewalls with increasing temperature, due to decreased carrier mobility and diffusivity at higher temperatures. Furthermore, due to current confinement and localization, light emission can occur in small localized regions, which can facilitate more efficient external optical coupling from micro-LEDs.

[0150] Figure 14AA schematic diagram 1400 includes an example illustrating the current-voltage (IV) curves of an AlGaInP-based red micro-LED according to certain embodiments. The micro-LED may have the configuration described with respect to, for example, micro-LED 1105, and may include a thyristor. Curve 1410 shows the IV curve of the micro-LED as the bias voltage gradually increases. Curve 1420 shows the IV curve of the micro-LED as the bias voltage gradually decreases. Curves 1410 and 1420 show that the micro-LED can behave in a manner similar to a thyristor. As shown, as the forward bias voltage increases from approximately 3.5V, the micro-LED can be in a forward blocking mode, where the forward leakage current can increase until the forward bias voltage reaches a breakdown voltage 1405 close to approximately 5V and the current reaches a latch-up current 1430 (e.g., approximately 2μA). At the breakdown voltage 1405, the micro-LED can be turned on, and the forward bias voltage can decrease significantly while the current can remain at approximately the latch-up current 1430. When the forward bias voltage is increased and the micro-LED is turned on, the current can increase to a higher level (e.g., 10 μA), while the forward bias voltage remains relatively low (e.g., below about 2.5 V). The micro-LED can remain on until the bias voltage drops to a level where the current is below the holding current 1440 (e.g., below about 2 μA).

[0151] Figure 14B Includes illustrations according to certain embodiments Figure 14A The schematic diagram 1450 shows the external quantum efficiency of an example AlGaInP-based red micro-LED as a function of injection current. Curve 1460 shows the relationship between the external quantum efficiency of the micro-LED and the injection current as the bias voltage increases. Curve 1470 shows the relationship between the external quantum efficiency of the micro-LED and the injection current as the bias voltage decreases. Figure 14B The results show that the external quantum efficiency can reach a high maximum when the micro-LED is turned on after the forward bias voltage exceeds the breakdown voltage (e.g., about 5V) and the current reaches the latch-up current (e.g., above 2μA). As the micro-LED remains on and the bias voltage increases, the external quantum efficiency begins to decrease, indicating that losses due to Auger recombination may increase due to the high current density in small localized regions within the active layer.

[0152] Figure 15A Includes illustrations according to certain embodiments Figure 14AThe diagram 1500 illustrates the output power of the emitted light from an example AlGaInP-based red micro-LED as a function of injection current. Curve 1510 shows the relationship between the output power of the emitted light from the micro-LED and the injection current as the bias voltage increases. Curve 1520 shows the relationship between the output power of the emitted light from the micro-LED and the injection current as the bias voltage decreases. Figure 15A This demonstrates that when the micro-LED is turned on after the forward bias voltage exceeds the breakdown voltage and the current reaches the latch-up current (e.g., above 2 μA), the output power can increase significantly (e.g., by more than 10 times). As the micro-LED remains on and the bias voltage is further increased, the output power of the emitted light can continue to increase, but the external quantum efficiency may decrease.

[0153] Figure 15B Including according to certain embodiments Figure 14A The example of an AlGaInP-based red micro-LED shown is illustrated in schematic diagram 1550, which displays the normalized output spectrum of emitted light at different current levels. Curve 1560 shows the output spectrum of emitted light when the injection current is at 0.5 μA, 0.8 μA, and 1 μA. Curve 1570 shows the output spectrum of emitted light when the injection current is higher than the latch-up current (e.g., at 3 μA, 5 μA, 8 μA, 20 μA, 30 μA, and 50 μA). Figure 15B The study showed that when the injection current is increased from 1 μA to 3 μA, there is a shift in the operating mode, in which the center wavelength of the emitted light can be shifted (e.g., shifted by about ten nanometers) to a longer wavelength, and the output spectrum can be significantly broadened.

[0154] Figure 16 Including according to certain embodiments Figure 14A Image 1600 shows the luminescent pattern of an example AlGaInP-based red micro-LED. The mesa structure of the micro-LED is indicated by circle 1610. The central electrode contact area is indicated by circle 1620. Image 1600 shows that light emission is highly localized in a small region 1630, which is offset from the central electrode contact area.

[0155] A one-dimensional or two-dimensional array of the LEDs described above can be fabricated on a wafer to form a light source (e.g., light source 642). For example, a driving circuit (e.g., driving circuit 644) can be fabricated on a silicon wafer using complementary metal-oxide-semiconductor (CMOS) technology. Multiple LEDs and driving circuits on multiple wafers can be diced and then bonded together, or multiple LEDs and driving circuits on multiple wafers can be bonded at the wafer level and then diced. Various bonding techniques can be used to bond the LEDs and driving circuits, such as adhesive bonding, metal-to-metal bonding, metal-oxide bonding, wafer-to-wafer bonding, die-to-wafer bonding, hybrid bonding, etc.

[0156] Figure 17A An example of a die-to-wafer bonding method for an LED array according to certain embodiments is shown. Figure 17A In the example shown, the LED array 1701 may include a plurality of LEDs 1707 on a carrier substrate 1705. The carrier substrate 1705 may include various materials, such as GaAs, indium phosphide (InP), GaN, AlN, sapphire, silicon carbide (SiC), Si, etc. Prior to bonding, the plurality of LEDs 1707 may be fabricated, for example, by growing various epitaxial layers, forming mesa structures, and forming electrical contacts or electrodes. These epitaxial layers may include various materials, such as GaN, InGaN, (AlGaIn)P, (AlGaIn)AsP, (AlGaIn)AsN, (AlGaIn)Pas, (Eu:InGa)N, (AlGaIn)N, etc., and these epitaxial layers may include n-type layers, p-type layers, and active layers including one or more heterostructures (e.g., one or more quantum wells or MQWs). The electrical contacts may include various conductive materials, such as metals or metal alloys.

[0157] Wafer 1703 may include a substrate layer 1709 having a plurality of passive integrated circuits or a plurality of active integrated circuits (e.g., driver circuitry 1711) fabricated thereon. Substrate layer 1709 may, for example, include a silicon wafer. Driver circuitry 1711 may be used to control the operation of LEDs 1707. For example, the driver circuitry for each LED 1707 may include a 2T1C pixel structure having two transistors and one capacitor. Wafer 1703 may also include a bonding layer 1713. Bonding layer 1713 may include various materials, such as metals, oxides, dielectrics, copper-tin alloys (CuSn), titanium-gold alloys (AuTi), etc. In some embodiments, a patterned layer 1715 may be formed on the surface of bonding layer 1713, wherein patterned layer 1715 may include a metal mesh made of a conductive material (e.g., Cu, Ag, Au, Al, etc.).

[0158] LED array 1701 can be bonded to wafer 1703 via bonding layer 1713 or patterning layer 1715. For example, patterning layer 1715 may include metal pads or bumps made of various materials (e.g., CuSn, gold-tin alloy (AuSn), or nanoporous Au) that can be used to align a plurality of LEDs 1707 in LED array 1701 with corresponding driving circuits 1711 on wafer 1703. In one example, LED array 1701 may be oriented toward wafer 1703 until the plurality of LEDs 1707 contact the corresponding metal pads or bumps corresponding to the plurality of driving circuits 1711. Some or all of the plurality of LEDs 1707 may be aligned with the plurality of driving circuits 1711 and then bonded to wafer 1703 via patterning layer 1715 using various bonding techniques (e.g., metal-to-metal bonding). After multiple LEDs 1707 have been bonded to wafer 1703, the carrier substrate 1705 can be removed from the multiple LEDs 1707.

[0159] Figure 17B An example of a wafer-to-wafer bonding method for an LED array according to certain embodiments is shown. Figure 17B As shown, the first wafer 1702 may include a substrate 1704, a first semiconductor layer 1706, a plurality of active layers 1708, and a second semiconductor layer 1710. The substrate 1704 may include various materials, such as GaAs, InP, GaN, AlN, sapphire, SiC, Si, etc. The first semiconductor layer 1706, the plurality of active layers 1708, and the second semiconductor layer 1710 may include various semiconductor materials, such as GaN, InGaN, (AlGaIn)P, (AlGaIn)AsP, (AlGaIn)AsN, (AlGaIn)Pas, (Eu:InGa)N, (AlGaIn)N, etc. In some embodiments, the first semiconductor layer 1706 may be an n-type layer, and the second semiconductor layer 1710 may be a p-type layer. For example, the first semiconductor layer 1706 may be an n-doped GaN layer (e.g., doped with Si or Ge), while the second semiconductor layer 1710 may be a p-doped GaN layer (e.g., doped with Mg, Ca, Zn, or Be). Multiple active layers 1708 may include, for example, one or more GaN layers, one or more InGaN layers, one or more AlGaInP layers, etc., which can form one or more heterostructures, such as one or more quantum wells or MQWs.

[0160] In some embodiments, the first wafer 1702 may further include a bonding layer. The bonding layer 1712 may include various materials, such as metals, oxides, dielectrics, CuSn, AuTi, etc. In one example, the bonding layer 1712 may include a plurality of p-contacts and / or a plurality of n-contacts (not shown). In some embodiments, the first wafer 1702 may also include other layers, such as a buffer layer between the substrate 1704 and the first semiconductor layer 1706. This buffer layer may include various materials, such as polycrystalline GaN or AlN. In some embodiments, a contact layer may be present between the second semiconductor layer 1710 and the bonding layer 1712. This contact layer may include any suitable material for providing electrical contact with the second semiconductor layer 1710 and / or the first semiconductor layer 1706.

[0161] The first wafer 1702 can be bonded to the wafer 1703, which includes the drive circuitry 1711 and the bonding layer 1713 as described above, via bonding layer 1713 and / or bonding layer 1712. Bonding layers 1712 and 1713 can be made of the same material or different materials. Bonding layers 1713 and 1712 can be substantially planar. The first wafer 1702 can be bonded to the wafer 1703 by various methods, such as metal-to-metal bonding, eutectic bonding, metal-oxide bonding, anodic bonding, thermocompression bonding, ultraviolet (UV) bonding, and / or fusion bonding.

[0162] like Figure 17B As shown, the first wafer 1702 can be bonded to the wafer 1703 with its p-side (e.g., the second semiconductor layer 1710) facing downwards (i.e., towards the wafer 1703). After bonding, the substrate 1704 can be removed from the first wafer 1702, and the first wafer 1702 can then be processed from the n-side. This processing may include, for example, forming certain mesa shapes for the respective LEDs, and forming a plurality of optical components corresponding to the respective LEDs.

[0163] Figures 18A-18D An example of a hybrid bonding method for an LED array according to certain embodiments is shown. This hybrid bonding typically includes wafer cleaning and activation, high-precision alignment of multiple contacts of one wafer with multiple contacts of another wafer, dielectric bonding of dielectric materials at the surfaces of the multiple wafers at room temperature, and metallic bonding of the multiple contacts by annealing at elevated temperatures. Figure 18A This shows a substrate 1810 on which multiple passive or active circuits 1820 are fabricated. (See above regarding...) Figure 17A and Figure 17BAs described, substrate 1810 may, for example, comprise a silicon wafer. Multiple circuits 1820 may comprise multiple driving circuits for an LED array. The bonding layer may comprise multiple dielectric regions 1840 and multiple contact pads 1830, these contact pads being connected to the multiple circuits 1820 via multiple electrical interconnects 1822. Contact pads 1830 may, for example, comprise Cu, Ag, Au, Al, tungsten (W), molybdenum (Mo), Ni, Ti, Pt, palladium (Pd), etc. The dielectric material in the dielectric regions 1840 may comprise silicon carbon nitride (SiCN), SiO2, SiN, Al2O3, hafnium dioxide (HfO2), zirconium dioxide (ZrO2), tantalum pentoxide (Ta2O5), etc. The bonding layer may be planarized and polished using, for example, chemical mechanical polishing, where planarization or polishing may cause depressions (bowl-shaped profiles) in the contact pads. The surface of the bonding layer may be cleaned and activated by, for example, ion (e.g., plasma) or fast atom (e.g., Ar) beam 1805. The activated surface can be atomically cleaned and reactive to facilitate the formation of direct bonds between multiple wafers, for example, when multiple wafers are in contact at room temperature.

[0164] Figure 18B The above describes, for example, the materials made thereon. Figure 7A , Figure 7B , Figure 17A and Figure 17BThe micro-LED 1870 array is described on a wafer 1850. Wafer 1850 can be a carrier wafer and may include, for example, GaAs, InP, GaN, AlN, sapphire, SiC, Si, etc. The micro-LED 1870 may include an n-type layer, an active region, and a p-type layer epitaxially grown on wafer 1850. These epitaxial layers may include the various III-V group semiconductor materials described above, and these epitaxial layers may be processed from the p-type layer side to etch multiple mesa structures, such as generally vertical structures, parabolic structures, or conical structures. Passivation layers and / or reflective layers may be formed on multiple sidewalls of the mesa structures. Multiple p-contacts 1880 and multiple n-contacts 1882 may be formed in a dielectric material layer 1860 deposited on the multiple mesa structures, and the multiple p-contacts may form electrical contacts with the p-type layer and the multiple n-contacts may form electrical contacts with the n-type layer. The dielectric material in the dielectric layer 1860 may include, for example, SiCN, SiO2, SiN, Al2O3, HfO2, ZrO2, Ta2O5, etc. The p-contacts 1880 and n-contacts 1882 may include, for example, Cu, Ag, Au, Al, W, Mo, Ni, Ti, Pt, Pd, etc. A bonding layer may be formed on the top surfaces of the plurality of p-contacts 1880, the plurality of n-contacts 1882, and the top surface of the dielectric layer 1860. This bonding layer may be planarized and polished, for example, using chemical mechanical polishing, where polishing can cause depressions in the plurality of p-contacts 1880 and n-contacts 1882. The bonding layer may then be cleaned and activated, for example, by an ion (e.g., plasma) or fast atom (e.g., Ar) beam 1815. The activated surface may be atomically cleaned and reactive to facilitate the formation of direct bonding between the multiple wafers when they are in contact, for example, at room temperature.

[0165] Figure 18CA room-temperature bonding process for bonding dielectric materials in multiple bonding layers is illustrated. For example, after surface activation of a bonding layer comprising multiple dielectric regions 1840 and multiple contact pads 1830, and a bonding layer comprising multiple p-contacts 1880, multiple n-contacts 1882, and a dielectric material layer 1860, a wafer 1850 and multiple micro-LEDs 1870 can be flipped over and brought into contact with a substrate 1810 and multiple circuits formed thereon. In some embodiments, a compressive pressure 1825 can be applied to the substrate 1810 and the wafer 1850, causing the multiple bonding layers to be pressed against each other. Due to surface activation and the depressions in the contacts, the multiple dielectric regions 1840 and the dielectric material layer 1860 can come into direct contact due to surface attraction and can react and form chemical bonds between them, because surface atoms can have dangling bonds and can be in an unstable energy state after activation. Therefore, the dielectric material in the dielectric region 1840 and the dielectric material layer 1860 can be bonded together under heat treatment or pressure or without heat treatment or pressure.

[0166] Figure 18D An annealing process is illustrated for bonding multiple contacts in multiple bonding layers after the dielectric material in the multiple bonding layers has been bonded. For example, contact pads 1830 can be bonded to p-contacts 1880 or n-contacts 1882 by annealing at a temperature of, for example, about 200°C to 400°C or higher. During the annealing process, heat 1835 can cause the multiple contacts to expand more than the dielectric material (due to their different coefficients of thermal expansion (CTE)), and thus close the recessed gaps between these contacts, allowing contact pads 1830 to contact p-contacts 1880 or n-contacts 1882 and forming a direct metallic bond at the activated surface.

[0167] In some embodiments where the bonded wafer comprises materials with different coefficients of thermal expansion (CTE), dielectric materials bonded at room temperature can help reduce or prevent misalignment of contact pads caused by different thermal expansions. In some embodiments, to further reduce or avoid misalignment of contact pads at high temperatures during annealing, trenches may be formed between multiple micro-LEDs or between multiple groups of micro-LEDs through a portion or all of the substrate prior to bonding.

[0168] After bonding multiple micro-LEDs to multiple driving circuits, the substrate on which the multiple micro-LEDs are fabricated can be thinned or removed, and various auxiliary optical components can be fabricated on the light-emitting surfaces of the multiple micro-LEDs to, for example, extract, collimate, and redirect light emitted from the active regions of the multiple micro-LEDs. In one example, multiple microlenses can be formed on the multiple micro-LEDs, each microlens corresponding to a corresponding micro-LED, and can help improve light extraction efficiency and collimate the light emitted by the micro-LED. In some embodiments, the auxiliary optical components can be fabricated in the substrate or in the n-type layer of the multiple micro-LEDs. In some embodiments, the auxiliary optical components can be fabricated in a dielectric layer deposited on the n-type side of the multiple micro-LEDs. Examples of auxiliary optical components can include lenses, gratings, antireflection (AR) coatings, prisms, photonic crystals, etc.

[0169] Figure 19 An example of an LED array 1900 having a plurality of auxiliary optical components fabricated thereon, according to certain embodiments, is shown. The LED array 1900 can be constructed using, for example, the methods described above. Figures 17A to 18D Any suitable bonding technique described herein, used to bond an LED chip or wafer to a silicon wafer (including circuitry fabricated thereon). Figure 19 In the example shown, the LED array 1900 can be used as described above. Figures 18A to 18D The wafer-to-wafer hybrid bonding technology described herein is used for bonding. The LED array 1900 may include a substrate 1910, which may be, for example, a silicon wafer. Multiple integrated circuits 1920 (e.g., multiple LED driver circuits) may be fabricated on the substrate 1910. The multiple integrated circuits 1920 may be connected to the p-contacts 1974 and n-contacts 1972 of multiple micro-LEDs 1970 via multiple interconnects 1922 and multiple contact pads 1930, wherein the multiple contact pads 1930 may form metallic bonds with the p-contacts 1974 and n-contacts 1972. A dielectric layer 1940 on the substrate 1910 may be bonded to a dielectric layer 1960 via fusion bonding.

[0170] The substrate (not shown) of the LED chip or wafer can be thinned or removed to expose the n-type layer 1950 of the micro-LED 1970. Various auxiliary optical components, such as spherical microlenses 1982, gratings 1984, microlenses 1986, anti-reflection layers 1988, etc., can be formed in or on the n-type layer 1950. For example, a spherical microlens array can be etched in the semiconductor material of the micro-LED 1970 using a grayscale mask and a photoresist that has a linear response to the exposed light, or using an etching mask formed by thermal reflow of a patterned photoresist layer. These auxiliary optical components can also be etched in a dielectric layer deposited on the n-type layer 1950 using similar photolithography techniques or other techniques. For example, a microlens array can be formed in a polymer layer by thermal reflow of a polymer layer patterned using a binary mask. The microlens array in the polymer layer can be used as an auxiliary optical component or as an etching mask to transfer the outline of the microlens array into a dielectric or semiconductor layer. The dielectric layer may include, for example, SiCN, SiO2, SiN, Al2O3, HfO2, ZrO2, or Ta2O5. In some embodiments, the micro-LED 1970 may have multiple corresponding auxiliary optical components, such as microlenses and anti-reflective coatings, microlenses etched in semiconductor materials and microlenses etched in dielectric material layers, microlenses and gratings, spherical lenses and aspherical lenses, etc. Figure 19 The image shows three different auxiliary optical components to illustrate some examples of multiple auxiliary optical components that can be formed on multiple micro-LEDs 1970. This does not necessarily mean that different auxiliary optical components can be used simultaneously for each LED array.

[0171] The embodiments disclosed herein can be used as components of an artificial reality system, or can be implemented in conjunction with an artificial reality system. An artificial reality is a form of reality that has been adjusted in some way before being presented to a user. This artificial reality may include, for example, virtual reality, augmented reality, mixed reality, or some combination and / or derivative thereof. Artificial reality content may include fully generated content or generated content combined with acquired (e.g., real-world) content. Artificial reality content may include video, audio, haptic feedback, or some combination thereof, and any one of these may be presented in a single channel or multiple channels (e.g., stereoscopic video that creates a three-dimensional effect for the viewer). Additionally, in some embodiments, the artificial reality may also be associated with applications, products, accessories, services, or some combination thereof, which are used, for example, to create content in the artificial reality and / or otherwise for use in the artificial reality (e.g., to perform activities in the artificial reality). Artificial reality systems that deliver artificial reality content can be implemented on a variety of platforms, including HMDs connected to host computer systems, standalone HMDs, mobile devices or computing systems, or any other hardware platform capable of delivering artificial reality content to one or more viewers.

[0172] Figure 20 This is a simplified block diagram of an example electronic system 2000 for implementing some of the examples of the various examples disclosed herein, such as an HMD device. The electronic system 2000 can be used as an electronic system in the aforementioned HMD device or other near-eye displays. In this example, the electronic system 2000 may include one or more processors 2010 and a memory 2020. The one or more processors 2010 may be configured to execute instructions for performing operations at multiple components and may be, for example, a general-purpose processor or microprocessor suitable for implementation within a portable electronic device. The one or more processors 2010 may be communicatively coupled to multiple components within the electronic system 2000. To achieve this communicative coupling, the one or more processors 2010 may communicate with other illustrated components via a bus 2040. The bus 2040 may be any subsystem suitable for transmitting data within the electronic system 2000. The bus 2040 may include multiple computer buses and additional circuitry for transmitting data.

[0173] The memory 2020 may be coupled to one or more processors 2010. In some embodiments, the memory 2020 may provide both short-term and long-term storage and may be divided into multiple units. The memory 2020 may be volatile (e.g., static random access memory (SRAM) and / or dynamic random access memory (DRAM)) and / or non-volatile (e.g., read-only memory (ROM), flash memory, etc.). Furthermore, the memory 2020 may include a removable storage device, such as a secure digital (SD) card. The memory 2020 may provide storage for computer-readable instructions, data structures, program modules, and other data for the electronic system 2000. In some embodiments, the memory 2020 may be distributed across different hardware modules. A set of instructions and / or code may be stored on the memory 2020. These instructions may take the form of executable code that can be executed by the electronic system 2000, and / or may take the form of source code and / or installable code that, when compiled and / or installed on the electronic system 2000 (e.g., using any of the various common compilers, installers, compression / decompression utilities, etc.), may take the form of executable code.

[0174] In some embodiments, memory 2020 may store a plurality of application modules 2022 to 2024, which may include any number of applications. Examples of applications may include game applications, conferencing applications, video playback applications, or other suitable applications. These applications may include depth detection or eye-tracking capabilities. Application modules 2022 to 2024 may include specific instructions to be executed by one or more processors 2010. In some embodiments, some or portions of the applications in application modules 2022 to 2024 may be executed by other hardware modules 2080. In some embodiments, memory 2020 may additionally include secure memory, which may include additional security controls to prevent copying or other unauthorized access to security information.

[0175] In some embodiments, memory 2020 may include an operating system 2025 loaded therein. Operating system 2025 may be operable to initiate the execution of instructions provided by application modules 2022 through 2024, and / or manage other hardware modules 2080 and multiple interfaces with a wireless communication subsystem 2030, which may include one or more wireless transceivers. Operating system 2025 may be adapted to perform other operations on various components of electronic system 2000, including threading, resource management, data storage control, and other similar functions.

[0176] The wireless communication subsystem 2030 may include, for example, infrared communication devices, wireless communication devices and / or chipsets (e.g., The electronic system 2000 may include one or more antennas 2034 for wireless communication, either as part of the wireless communication subsystem 2030 or as a separate component coupled to any part of the system. Depending on the desired functionality, the wireless communication subsystem 2030 may include separate transceivers for communicating with base transceiver stations, as well as other wireless devices and access points. This may include communication with different data networks and / or network types, such as wireless wide-area networks (WWANs), wireless local area networks (WLANs), or wireless personal area networks (WPANs). A WWAN may be, for example, a WiMax (IEEE 802.16) network. A WLAN may be, for example, an IEEE 802.11x network. A WPAN may be, for example, a Bluetooth network, an IEEE 802.15x network, or some other type of network. The techniques described herein can also be used in any combination of WWAN, WLAN, and / or WPAN. The wireless communication subsystem 2030 can allow data exchange with the network described herein, other computer systems, and / or any other devices. The wireless communication subsystem 2030 may include means for transmitting or receiving data using one or more antennas 2034 and one or more wireless links 2032, such data being, for example, identifiers of HMD devices, location data, geographic maps, heat maps, photographs, or videos. The wireless communication subsystem 2030, one or more processors 2010, and memory 2020 may, at least together, include a portion of one or more means for performing some of the functions disclosed herein.

[0177] Embodiments of the electronic system 2000 may also include one or more sensors 2090. One or more sensors 2090 may include, for example, an image sensor, accelerometer, pressure sensor, temperature sensor, proximity sensor, magnetometer, gyroscope, inertial sensor (e.g., a module combining an accelerometer and a gyroscope), ambient light sensor, or any other similar module operable to provide sensory output and / or receive sensory input (e.g., a depth sensor or position sensor). For example, in some embodiments, one or more sensors 2090 may include one or more inertial measurement units (IMUs) and / or one or more position sensors. The IMU may generate calibration data indicating an estimated position of the HMD device relative to an initial position of the HMD device based on received measurement signals from one or more of the plurality of position sensors. The position sensors may generate one or more measurement signals in response to movement of the HMD device. Examples of position sensors may include, but are not limited to, one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor for detecting movement, a sensor for error correction of the IMU, or any combination thereof. The position sensors may be located external to the IMU, internal to the IMU, or any combination thereof. At least some sensors can use structured light patterns for detection.

[0178] Electronic system 2000 may include display module 2060. Display module 2060 may be a near-eye display and may present information from electronic system 2000, such as images, videos, and various commands, to a user in a graphical manner. This information may originate from one or more application modules 2022 to 2024, virtual reality engine 2026, one or more other hardware modules 2080, any combination thereof, or any other suitable device used (e.g., via operating system 2025) to interpret graphical content for the user. Display module 2060 may use LCD technology, LED technology (e.g., including OLED, ILED, μ-LED, AMOLED, TOLED, etc.), light-emitting polymer display (LPD) technology, or some other display technology.

[0179] Electronic system 2000 may include user input / output module 2070. User input / output module 2070 allows a user to send action requests to electronic system 2000. An action request may be a request to perform a specific action. For example, an action request may be to start or end an application, or to perform a specific action within an application. User input / output module 2070 may include one or more input devices. Example input devices may include a touchscreen, touchpad, one or more microphones, one or more buttons, one or more dial pads, one or more switches, keyboard, mouse, game controller, or any other suitable device for receiving action requests and transmitting the received action requests to electronic system 2000. In some embodiments, user input / output module 2070 may provide haptic feedback to the user based on instructions received from electronic system 2000. For example, haptic feedback may be provided upon receiving an action request or upon the execution of an action request.

[0180] Electronic system 2000 may include camera 2050, which can be used to capture photos or videos of a user, for example, to track the user's eye position. Camera 2050 may also be used to capture photos or videos of the environment, for example, for VR, AR, or MR applications. Camera 2050 may, for example, include a complementary metal oxide-semiconductor (CMOS) image sensor with millions or tens of millions of pixels. In some embodiments, camera 2050 may include two or more cameras that can be used to acquire 3D images.

[0181] In some embodiments, the electronic system 2000 may include a plurality of other hardware modules 2080. Each of the plurality of other hardware modules 2080 may be a physical module within the electronic system 2000. While each of the plurality of other hardware modules 2080 may be permanently configured as a structure, some of the plurality of other hardware modules 2080 may be temporarily configured to perform a particular function or be temporarily activated. Examples of the plurality of other hardware modules 2080 may include, for example, audio output and / or input modules (e.g., microphones or speakers), near field communication (NFC) modules, rechargeable batteries, battery management systems, wired / wireless battery charging systems, etc. In some embodiments, one or more functions of the plurality of other hardware modules 2080 may be implemented in software.

[0182] In some embodiments, the memory 2020 of the electronic system 2000 may also store a virtual reality engine 2026. The virtual reality engine 2026 can execute applications within the electronic system 2000 and receive position information, acceleration information, velocity information, predicted future position, or any combination thereof from various sensors of the HMD device. In some embodiments, the information received by the virtual reality engine 2026 can be used to generate signals (e.g., display instructions) provided to the display module 2060. For example, if the received information indicates that the user has looked to the left, the virtual reality engine 2026 can generate content for the HMD device reflecting the user's movement in the virtual environment. Additionally, the virtual reality engine 2026 can perform actions within the application in response to received action requests from the user input / output module 2070 and provide feedback to the user. The provided feedback may be visual, auditory, or haptic feedback. In some embodiments, one or more processors 2010 may include one or more GPUs capable of executing the virtual reality engine 2026.

[0183] In various implementations, the aforementioned hardware and modules can be implemented on a single device or on multiple devices that can communicate with each other using wired or wireless connections. For example, in some implementations, some components or modules (e.g., GPU, Virtual Reality Engine 2026, and applications (e.g., tracking applications)) can be implemented on a console separate from the head-mounted display device. In some implementations, a console can be connected to or support more than one HMD.

[0184] In alternative configurations, the electronic system 2000 may include different and / or additional components. Similarly, the functionality of one or more of these components may be distributed across multiple components in a manner different from that described above. For example, in some embodiments, the electronic system 2000 may be modified to include other system environments, such as AR system environments and / or MR environments.

[0185] The methods, systems, and apparatus discussed above are examples. Various embodiments may appropriately omit, substitute, or add various processes or components. For example, in alternative configurations, the described methods may be performed in a different order than that described, and / or various stages may be added, omitted, and / or combined. Furthermore, features described with respect to certain embodiments may be combined in various other embodiments. Different aspects and elements of these embodiments may be combined in a similar manner. Moreover, technology is evolving, and therefore many of the various elements are examples that do not limit the scope of this disclosure to those specific examples.

[0186] Numerous specific details are set forth in this specification to provide a thorough understanding of various embodiments. However, these embodiments may be practiced without these specific details. For example, well-known circuits, processes, systems, structures, and techniques are shown without unnecessary detail to avoid obscuring these embodiments. This specification provides exemplary embodiments only and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the foregoing description of these embodiments will provide those skilled in the art with a description for conditionally carrying out the various embodiments. Various modifications to the function and arrangement of the various elements may be made without departing from the spirit and scope of this disclosure.

[0187] Furthermore, some embodiments are described as multiple processes, depicted as flowcharts or block diagrams. While each diagram may describe multiple operations as a sequential process, many operations may be performed in parallel or simultaneously. Additionally, the order of these operations can be rearranged. Processes may have additional steps not included in the diagrams. Furthermore, embodiments of these methods can be implemented using hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware, or microcode, program code or code segments for performing associated tasks can be stored in a computer-readable medium such as a storage medium. A processor can execute the associated tasks.

[0188] It will be apparent to those skilled in the art that substantial variations can be made to suit specific requirements. For example, custom or dedicated hardware may be used, and / or specific elements may be implemented in hardware, software (including portable software such as applets), or both. Furthermore, connectivity to other computing devices, such as network input / output devices, may be employed.

[0189] Referring to the accompanying drawings, multiple components that may include a memory may include non-transitory machine-readable media. The terms "machine-readable media" and "computer-readable media" can refer to any storage medium that participates in providing data that enables a machine to operate in a particular manner. In the embodiments provided above, various machine-readable media may relate to providing instructions / code to multiple processing units and / or one or more other devices for execution. Additionally or alternatively, machine-readable media may be used to store and / or carry these instructions / code. In many embodiments, a computer-readable medium is a physical and / or tangible storage medium. Such a medium can take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Common forms of computer-readable media include, for example, magnetic and / or optical media such as compact disks (CDs) or digital versatile disks (DVDs), punched cards, paper tape, any other physical media with a perforated pattern, random access memory (RAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), flash memory (FLASH-EPROM), any other memory chip or cassette, a carrier wave as described below, or any other medium from which a computer can read instructions and / or code. Computer program products may include code and / or machine-executable instructions that can represent procedures, functions, subroutines, programs, routines, application programs (Apps), subroutines, modules, software packages, classes, or any combination of instructions, data structures, or program statements.

[0190] Those skilled in the art will understand that any of a variety of different techniques and methods can be used to represent the information and signals used to transmit the messages described herein. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be mentioned throughout the foregoing description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or optical particles, or any combination thereof.

[0191] As used herein, the terms “and” and “or” can have a variety of meanings, which are also expected to depend at least in part on the context in which the terms are used. Generally, “or” when used in an associative list (e.g., A, B, or C) is intended to mean A, B, and C (used herein in an inclusive sense), and A, B, or C (used herein in an exclusive sense). Additionally, the term “one or more” as used herein can be used to describe any feature, structure, or property in its singular form, or can be used to describe some combination of features, structures, or properties. However, it should be noted that this is merely an illustrative example, and the claimed subject matter is not limited to this example. Furthermore, the term “at least one of” when used in an associative list (e.g., A, B, or C) can be interpreted as meaning any combination of A, B, and / or C, such as A, AB, AC, BC, AA, ABC, AAB, AABBCCC, etc.

[0192] Furthermore, while certain embodiments have been described using specific combinations of hardware and software, it should be recognized that other combinations of hardware and software are also possible. Some embodiments may be implemented using only hardware, or only software, or a combination of hardware and software. In one example, the software may be implemented using a computer program product containing computer program code or instructions that can be executed by one or more processors to perform any or all of the multiple steps, operations, or processes described herein, wherein the computer program may be stored on a non-transitory computer-readable medium. The various processes described herein may be implemented on the same processor or on different processors in any combination.

[0193] When a device, system, component, or module is described as being configured to perform certain operations or functions, such configuration can be achieved, for example, by designing electronic circuitry to perform the operations, by programming programmable electronic circuitry (e.g., a microprocessor) to perform the operations (e.g., by executing computer instructions or code), or by a processor or core programmed to execute code or instructions stored on a non-transitory storage medium, or any combination thereof. Multiple processes can communicate using various technologies, including but not limited to conventional technologies for inter-process communication, and different pairs of processes can use different technologies, or the same pair of processes can use different technologies at different times.

[0194] Therefore, the specification and drawings should be considered illustrative rather than restrictive. However, it is apparent that additions, omissions, deletions, and other modifications and variations may be made therein without departing from the broader spirit and scope set forth in the claims. Thus, although specific embodiments have been described, these embodiments are not intended to be limiting. Various modifications and equivalents are within the scope of the appended claims.

Claims

1. A miniature light-emitting diode, comprising: First n-type semiconductor layer; An active region, wherein the active region is located on the first n-type semiconductor layer; A first p-type semiconductor layer is located on the active region; A carrier barrier region, wherein the carrier barrier region is located on the first p-type semiconductor layer; as well as An electrode comprising a conical structure that contacts the carrier barrier region and is configured to apply an electric field to a local region of the carrier barrier region to cause breakdown in the local region of the carrier barrier region.

2. The miniature light-emitting diode according to claim 1, wherein, The carrier barrier region includes: A second n-type semiconductor layer, wherein the second n-type semiconductor layer is located on the first p-type semiconductor layer; and A second p-type semiconductor layer is located on top of the second n-type semiconductor layer. The second p-type semiconductor layer, the second n-type semiconductor layer, and the first p-type semiconductor layer form a PNP device.

3. The miniature light-emitting diode according to claim 2, wherein, The PNP device and the first n-type semiconductor layer form a thyristor.

4. The miniature light-emitting diode according to claim 1, wherein: The carrier barrier region includes an n+ semiconductor layer, which is located on the first p-type semiconductor layer; The first p-type semiconductor layer includes a p+ semiconductor layer; as well as The n+ semiconductor layer and the first p-type semiconductor layer form a tunnel junction.

5. The miniature light-emitting diode according to claim 1, wherein, The carrier barrier region includes: A tunnel barrier layer, wherein the tunnel barrier layer is located on the first p-type semiconductor layer; A second n-type semiconductor layer is located on top of the first p-type semiconductor layer. The tunnel barrier layer has a higher band gap than the first p-type semiconductor layer and the second n-type semiconductor layer.

6. The miniature light-emitting diode according to claim 1, wherein, The carrier barrier region includes a heterojunction or a Schottky barrier.

7. The miniature light-emitting diode according to claim 1, wherein, The carrier barrier region includes a heterogeneous barrier that causes band bending to form a tunneling contact.

8. The miniature light-emitting diode according to claim 1, wherein, The distance between the carrier barrier region and the active region is less than the carrier diffusion length of the active region.

9. The miniature light-emitting diode according to claim 1, wherein, The active region includes an AlGaInP quantum well and is configured to emit red light.

10. The miniature light-emitting diode according to claim 1, wherein, The active region includes at least one of a p-doped quantum barrier layer or a p-doped quantum well layer.

11. The miniature light-emitting diode according to claim 10, wherein, The p-doped quantum well layer is characterized by an acceptor concentration of 1×10⁻⁶. 17 / cm 3 With 1×10 19 / cm 3 between.

12. The miniature light-emitting diode according to claim 1, wherein, The conical structure includes a conical tip that extends into the carrier barrier region.

13. The miniature light-emitting diode according to claim 1, wherein, The micro LED is characterized by having a linear dimension of less than 20 μm.

14. The miniature light-emitting diode according to claim 1, wherein, The local region of the carrier barrier region is characterized in that its linear size is less than one-third of the linear size of the micro-LED.

15. A miniature light-emitting diode, comprising: First n-type semiconductor layer; An active region is located on the first n-type semiconductor layer, and the active region includes at least one p-doped quantum well; A first p-type semiconductor layer is located on the active region; A current-limiting structure, the current-limiting structure including a local current hole and configured to inject carriers into the active region through the local current hole; as well as Electrode, the electrode being located on the local current hole of the current limiting structure, The current-limiting structure includes a carrier barrier layer; The electrode includes a conical structure that contacts the carrier barrier layer and is configured to apply an electric field to a local region of the carrier barrier layer to cause breakdown in the local region of the carrier barrier layer, thereby forming the local current hole.

16. The miniature light-emitting diode according to claim 15, wherein, The carrier barrier layer includes: A second n-type semiconductor layer, wherein the second n-type semiconductor layer is located on the first p-type semiconductor layer; and A second p-type semiconductor layer is located on top of the second n-type semiconductor layer. The second p-type semiconductor layer, the second n-type semiconductor layer, the first p-type semiconductor layer, and the first n-type semiconductor layer form a thyristor.

17. The miniature light-emitting diode according to claim 15, wherein, The carrier barrier layer comprises a heterojunction.

18. The miniature light-emitting diode according to claim 15, wherein, The carrier barrier layer includes a tunnel junction.

19. The miniature light-emitting diode according to claim 15, wherein, The p-doped quantum well is characterized by an acceptor concentration of 1×10⁻⁶. 17 / cm 3 and 1×10 19 / cm 3 between.

20. The miniature light-emitting diode according to claim 15, wherein, The local current aperture is characterized in that its linear dimension is less than one-third of the linear dimension of the micro LED.

21. The miniature light-emitting diode according to claim 15, wherein, The active region includes an AlGaInP layer and is configured to emit red light.

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