Wide color gamut adjustable LED device and display system with reduced undesirable color artifacts and method thereof

Abstract

A color-tunable LED system configured to emit light of various peak wavelengths in response to changes in drive current density includes an n-type region, a p-type region, and a multiple quantum well (MQW) region formed between the n-type and p-type regions. The MQW region includes parallel layers, each alloyed with a percentage of indium that enables light emission in the 400-600 nm range, and one or more shaped recesses formed within portions of the parallel layers. Each of the one or more shaped recesses has a lower indium alloy percentage than the rest of the parallel layers. A transition region between the one or more shaped recesses and the rest of the parallel layers has a higher indium alloy percentage, which decreases with distance from the one or more shaped recesses. A monolithic color-tunable LED system allows for the use of a single LED to function as a pixel.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 438,435, filed January 11, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present technology relates to color-tunable light-emitting diodes, LED systems, and LED display systems including such light-emitting diodes, and methods thereof. [Background technology]

[0003] Displays based on inorganic light-emitting diodes (LEDs), particularly the small mini-LEDs and μ-LEDs, are seen by the display industry as emerging successors to displays containing organic light-emitting diodes (OLEDs) for many applications, including both near-eye displays and large form-factor displays viewed from a distance. They offer many advantages, including high efficiency, environmental robustness, scalability, and high brightness.

[0004] However, the development of improved inorganic LEDs and LED displays has been hindered by problems with integrating separately fabricated red, green, and blue LEDs into a functional, controllable LED system capable of emitting light across the entire visible spectrum. Each LED contains layers of an electron-rich n-type region, a hole-rich p-type region, and a multiple quantum well (MQW) region between the n-type and p-type regions. The MQW region is composed of multiple individual quantum wells with smaller energy bandgaps due to alloying, and the multiple individual quantum wells are placed between materials with higher energy bandgaps. The smaller energy bandgap quantum wells confine electrons and holes, facilitating their recombination and corresponding light emission.

[0005] For example, blue and green LEDs are generally based on the III-N material system. Indium is alloyed with GaN in different amounts to narrow the bandgap of the quantum well. While blue light can be generated with quantum wells containing approximately 10% indium, incorporating additional indium leads to longer wavelength emissions, such as green. Using only the III-N material system for blue, green, and red is limited by the difficulty of incorporating the high levels of indium used for red. Increasing the indium concentration creates strain and solubility issues. Traditionally, red emitters instead utilize III-V material systems, with AlInGaP as the primary material. Relying on these heterogeneous material systems, associated with blue, green, and red, respectively, typically requires their separate fabrication and subsequent integration with silicon-based control electronics within the display. This integration typically results in higher costs and more complex manufacturing processes.

[0006] To avoid the need to grow individual LEDs, there are three main approaches to developing more efficient red-emitting and overall visible-emitting color-tunable InGaN LEDs that reduce the integration problems mentioned above: europium doping, the use of porous GaN substrates, or nanowire growth. However, each of these approaches suffers from the problems of complex display fabrication and poor light emission uniformity.

[0007] Furthermore, one of the main challenges facing this type of display is that conventional light-emitting diodes only provide a single, fixed color. Therefore, prior art techniques typically involve printing a set of light-emitting diodes, typically consisting essentially of red, green, and blue colors. This results in the use of multiple emitters to achieve full color reproduction, with the attendant increased complexity and cost of manufacturing and driving circuitry. According to the configuration and method of operation disclosed herein, this problem can be overcome by using novel color-tunable light-emitting diodes that enable full color reproduction and image reconstruction with only one light-emitting diode per pixel. Summary of the Invention [Means for solving the problem]

[0008] Examples of the present technology relate to color-tunable LEDs, LED systems, and display systems that can be essentially monolithic by using a common single-crystal material system configured to emit light of various peak wavelengths in response to changes in drive current density. Both the LEDs and LED systems are preferably fabricated in a single-crystal GaN material system, also referred to as a monolithic system in the examples herein, based on a common process for GaN. Single crystal is defined herein as an ordered arrangement of atoms forming a single wurtzite crystal. The LEDs and LED systems include an n-type region, a p-type region optionally having an electron blocking layer (EBL), and a multiple quantum well (MQW) region formed between the n-type and p-type regions. The MQW region includes parallel layers, each alloyed with a percentage of indium to enable emission in the 400-600 nm range. The MQW region is formed on a first active doped layer or region selectively patterned along one surface with one or more shaped recesses and one or more spacing features to promote controlled color emission in the MQW layer of the MQW region. Each of the one or more portions of the MQW layer of the MQW region that fit into a recess in the first active doped layer has a lower concentration of indium alloy percentage than other portions of the MQW layer of the MQW region, and a transition region between the region that fits into the recess in the first active doped layer and the other portions of the MQW layer has a higher concentration of indium alloy percentage than the region that fits into the first active layer recess, the indium alloy percentage decreasing with distance from one or more such recesses.

[0009] A method for fabricating a color-tunable LED system configured to emit light of various peak wavelengths in response to changes in drive current density includes forming a first active doped n-type layer or a first active doped p-type layer. In various examples, the first active doped n-type layer or the first active doped p-type layer can be etched or otherwise patterned to create various recesses of various shapes, sizes, sidewall angles, or other features and spacing configurations mentioned elsewhere herein. An MQW region is grown on the first active doped n-type layer or the first active doped p-type layer. The MQW region includes parallel layers, each alloyed with a percentage of indium that enables light emission in the 400-600 nm range, and the layers of the MQW region conform to one or more of the shaped recesses formed in the first active doped layer. The portions of the parallel layers that conform to the patterned recesses in the first active doped layer have a lower indium alloy percentage than other portions of the parallel layers. The transition region between the portion of the parallel layers that fits into the recess in the first active layer and the remaining portions of the parallel layers has a higher indium alloy percentage, which decreases with distance from the portion of the parallel layers that fits into the recess. A second active doped layer, opposite in charge to the first active layer, is grown on the MQW region.

[0010] In an example of the present technology, each color-tunable LED can function as a pixel element, with each such LED rapidly switching between two or more emission wavelengths in response to abrupt changes in the corresponding drive current density so that a single color is perceived. Individual pixel elements can be arrayed multiple times to create a complete display system of any desired shape or resolution. Multiple color-tunable LEDs can be combined and arrayed to form a complete, optionally monolithic, LED display system. In another example of the present technology, a functioning pixel element can optionally include multiple monolithic color-tunable LEDs, each with the same or different density or design of recesses patterned in the first active doped layer, and capable of emitting visible light as various colors or a fixed color.

[0011] In another example of the present technology, a color-tunable LED can have additional components added to create the basis of a pixel element. The additional components can take the form of device elements such as, for example, transistors, capacitors, and diodes. The device elements, along with the color-tunable LED, can be electrically connected to form various circuits, for example, current sources and active matrix circuitry for each pixel element. The pixel element can function by rapidly switching each color-tunable LED between two or more emission wavelengths in response to abrupt changes in the corresponding drive current density, so that a single color is perceived. Individual pixel elements can be arrayed multiple times to create a complete color-tunable LED display system of any desired shape or resolution.

[0012] In examples where color-tunable LEDs are included in the pixel elements, additional circuitry may be integrated to provide voltage and current signals to drive the LED array, which together comprise an LED display system. The circuitry may take the form of an external chip or may be integrated on-chip with the LEDs, optionally creating a monolithic LED display system.

[0013] The color-tunable LEDs and color-tunable LED display systems described and claimed herein offer many advantages and can be effectively utilized in several different applications, such as microdisplays and larger-format displays, commercial lighting, and light-based data communications. In particular, examples of the present technology provide color-tunable LEDs that can emit light across the entire visible spectrum without the need for additional color converters. This reduces complexity, provides superior performance, and reduces cost for many applications. Monolithic is defined for some examples herein as a common InGaN / GaN, III-N material system used solely within the same wafer. Variations of examples of the present technology can further provide monolithic color-tunable LEDs without Eu doping, the use of porous GaN substrates, or nanowire growth. Furthermore, in other examples, a single LED can be configured to function as a pixel, rather than using three LEDs that selectively emit red, green, and blue light, a common RGB approach widely used today. Reducing the number of LED subpixels used to form a pixel increases potential display resolution and reduces footprint. This reduced footprint is particularly advantageous for μ-LED displays intended for near-eye applications such as virtual or augmented reality, and it also reduces costs and allows for more efficient manufacturing.

[0014] Furthermore, the problems described in the Background section can, in some instances, be addressed by using alternative methods to fabricate LED devices / systems using monolithic, i.e., a common, universal, single-crystal material system, such as single-crystal GaN, to achieve a simpler system. Monolithic is defined herein as a common InGaN / GaN, III-N material system used exclusively for all semiconductor growth on the same wafer. III-N is defined herein as a class of materials that includes GaN and an element that is alloyed with GaN, such as indium or aluminum.

[0015] In other alternative embodiments, light emitting drive schemes are described that can be used to improve and / or mitigate certain undesirable visual artifacts such as (among other things) color breakup.

[0016] In other alternative embodiments, the design and manufacture of LED devices / systems may incorporate tuning of quantum wells to further optimize light emission. By way of example only, quantum wells may be independently configured to emit a wider range of greens and blues to affect a wide color gamut display, as further described herein below. [Brief explanation of the drawings]

[0017] [Figure 1A] 1 is a cross-sectional image of an example of patterned depressions formed along one surface of a first active doped layer (n-type material in this example) prior to forming the final layer. [Figure 1B] FIG. 1B is a perspective view of a portion of FIG. 1A showing various shaped depressions patterned along one side of the first active doped layer (n-type in this example), with dotted edges to represent a cross section of FIG. 1A. [Figure 1C] FIG. 1C is a cross-sectional image of the example color-tunable LED system of FIG. 1B incorporating a first active doped layer (in this example, an n-type material) patterned along one surface with multiple shaped and spaced depressions that facilitate controlled color emission of the MQW layer in the MQW region of the LED. [Figure 2] A CIE 1931 graph showing the wider color gamut of an LED display achieved by individually optimizing each quantum well is shown. [Figure 3] 10 is an example graph showing how a single color-tunable LED can be driven at different current densities to produce different colors of equal intensity by varying the duty cycle and current. [Figure 4A] 1 is an example graph showing the operation of a single color-tunable LED driven to produce a perceived purple color by rapidly alternating between pulsed current densities that produce red and blue wavelength emission. [Figure 4B] 1 is an example graph showing the operation of a single color-tunable LED driven to produce a perceived purple color by rapidly alternating between pulsed current densities that produce red and blue wavelength emission. [Figure 5A] 1 is an example graph showing the operation of a single color-tunable LED driven to produce a visible white light by rapidly alternating between pulsed current densities that produce yellow and blue wavelength emissions. [Figure 5B] 1 is an example graph showing the operation of a single color-tunable LED driven to produce a visible white light by rapidly alternating between pulsed current densities that produce yellow and blue wavelength emissions. [Figure 6A] 1 shows a top view of an array of light emitting diode devices that may be fabricated and / or manufactured in accordance with any of the displays described herein. [Figure 6B] FIG. 5B illustrates the array of light-emitting diode elements shown in FIG. 5A emitting a two-color spatial dithering pattern. [Figure 6C] FIG. 5C shows an array of light-emitting diode elements emitting a two-color spatial dithering pattern with an opposite distribution to that shown in FIG. 5B. [Figure 7] 1 is an example graph showing how a single color-tunable LED can be driven at different current densities to produce different colors of equal brightness by varying the duty cycle and current. [Figure 8A] 1 is a graph of the CIE 1931 color space illustrating an example of the operation of a single color-tunable LED driven to produce a single visible color by rapidly alternating pulse current densities that emit a metameric wavelength pair. [Figure 8B] 1 is a graph of the CIE 1931 color space showing the line of colors that can be reproduced using metamer pairs with equal luminance. [Figure 8C]CEI1931 color space graph showing the color gamut of a display system using a combination of arrays of color-tunable μ-LEDs and arrays of fixed-color μ-LEDs. [Figure 9A] FIG. 1 is a top-level block diagram of a micro-LED display system. [Figure 9B] FIG. 1 is a diagram of a micro-LED pixel element with current and pulse width modulation control. [Figure 9C] FIG. 1 is a diagram of a metamer selection block. [Figure 10] 1 shows an array of light emitting diode elements. [Figure 11] FIG. 1 is a top-level block diagram of a micro-LED display system. [Figure 12] 1 shows an array of light emitting diode elements. [Figure 13] FIG. 1 is a top-level block diagram of a micro-LED display system. DETAILED DESCRIPTION OF THE INVENTION

[0018] As shown in FIGS. 1A, 1B, and 1C, examples of color-tunable LED technology offer several advantages, including providing color-tunable LED systems that can be effectively utilized in several different applications, such as displays, commercial lighting, and communications, and can optionally be fabricated from a single material system.

[0019] 1A , in this example, to create a color-tunable LED system 10(1), a patterned first doped active layer including an n-GaN layer is formed on an initial growth substrate 25, such as, for example, silicon or sapphire, although other types and / or numbers of doped layers and / or substrates may also be used. In this example, the surface of the first active layer 12 is patterned with shaped depressions 18(1a-1c), such as a circle, triangle, square, pentagon, hexagon, or an arrangement of multiple such shapes, having a top diameter of about 150 nm to about 10 μm, a spacing between the depressions 18(1a-1c) of about 150 nm to about 10 μm, and a height or depth difference from the surface of the depressions 18(1a-1c) of less than about 5 μm, enabling color-tunable light emission in the MQW region, although other patterns having other sizes, spacings, and / or shapes may also be used. The sidewalls of the recesses 18 (1a-1c) may be at an angle between 0 and 90 degrees relative to the substrate in some examples, and between 90 and 180 degrees in other examples. As a further example, the sidewalls of the recesses 18 (1a-1c) may have positive, negative, and / or vertical slopes relative to the growth substrate 25. The recesses 18 (1a-1c) are added to adjust the indium content and control the emission spectrum from the LED by differential indium incorporation along different crystal planes. These recesses 18 (1a-1c) locally relax the crystal structure and modify the absorption of indium within the MQW region. The use of shaped recesses 18 (1c) at a 90-degree angle relative to the substrate is expected to enhance short-wavelength, blue emission from the color-tunable LED system 10 (1). On the other hand, the use of shaped depressions 18(1a-b) with a positive slope less than or greater than 90 degrees relative to the substrate, respectively, or shaped depressions with a negative slope, can promote longer wavelength red emission from the color-tunable LED system 10(1). Selective incorporation of different shaped depressions 18(1a-1c) can be used to tune the color emission from the color-tunable LED system 10(1) at a fixed current density.

[0020] The geometry and arrangement of the recesses 18 (1a-1c) shown in FIG. 1A can be formed through typical semiconductor process steps, such as, by way of example, epitaxial growth, dry etching, or wet etching. These process steps are performed in the first doped active layer 12, which is the first electrically active layer in the device. The formation of the recesses 18 (1a-1c) precedes the formation of the MQW region 16. The density and size of these selectively formed shaped recesses 18 (1a-1c) can be advantageously adjusted to modify the indium content to obtain a desired color emission spectrum from the LED.

[0021] The arrangement of the depressions 18 (1a-1c) can take the form of an array, such as, for example, a regular or hexagonal array, as shown in FIG. 1B. One or more of the same or different shaped depressions 18 (1a-1c) can be incorporated into a single LED. The depressions 18 (1a-1c) can take the form of a circle, a triangle, a square, a pentagon, a hexagon, or an arrangement of multiple such shapes.

[0022] Surface treatments can be performed to clean and remove any surface damage that may occur after the creation of the recesses 18 (1a-1c). These surface treatments can take the form of a combination of dry and wet etching or cleaning.

[0023] Referring to FIG. 1C, MQW region 16 is formed on first doped active layer 12 and includes parallel layers of GaN alloyed with a percentage of indium that enables an emission range between 400 and 600 nm. A typical indium percentage may be 18%, for example. The regions of the parallel layers of MQW region 16 that fit into the underlying recesses 18 (1a-1c) have a lower density of indium alloy percentage than the regions of the parallel layers of MQW region 16 that do not fit into the recesses 18 (1a-1c). These other regions of the parallel layers of MQW region 16 that do not fit into the recesses 18 (1a-1c) are also referred to herein as planar MQWs. Furthermore, in this example, the transition region 22 in FIG. 1C between the portion of the parallel layer that fits into the recess 18(1a-c) and other regions of the parallel layer that are located outside the parallel layer that fits into the recess 18(1a-1c) has a higher concentration of indium alloy percentage, which decreases in other regions of the parallel MQW layer as the distance from the recess 18(1a-1c) increases.

[0024] The sides of the recesses 18 (1a-1c) may be semipolar or nonpolar crystal planes with low indium content due to differences in the sticking coefficient of indium during growth. The semipolar or nonpolar MQWs within the recesses 18 (1a-1c) of the parallel layers of the MQW region 16 are thinner than the planar MQWs or other portions of the parallel layers of the MQW region 16. The reduced indium concentration in the parallel layers of the MQW region 16 that fit into the recesses 18 (1a-1c) compared to the designed planar MQW 16 is accompanied by a "transition zone" or transition region 22 with a higher indium concentration that forms in the MQWs of the MQW region 16 adjacent to the recesses 18 (1a-1c). The indium concentration is highest at the periphery of the recesses 18 (1a-1c) and decreases with distance from the recesses 18 (1a-1c) to the level of the indium alloy initially incorporated into the designed planar MQW.

[0025] In this example, the indium-poor semipolar or nonpolar MQWs in the MQW region 16 inside the recesses 18 (1a-1c) may have 5-15% indium, whereas the planar MQWs in the transition regions 22 closest to each of the recesses 18 (1a-1c) have an indium concentration reaching 30-50%, decreasing with increasing distance from the recesses 18 (1a-1c) to the designed 18% indium concentration in the rest of the parallel layers of the MQW region 18. This localized indium increase is not detrimental to the electron-hole recombination efficiency, as would be the case with intentionally high indium content growth of continuous planar MQWs. This is because these locally increased regions are strain-relieved due to the recesses 18 (1a-1c).

[0026] A second active doped layer of opposite charge type is formed on MQW region 16. In this example, the second active doped layer is a p-type AlGaN EBL layer 20 with p-type GaN layer 14, although other types and / or numbers of layers may be used, and in some examples, the EBL layer is optional. EBL layer 20 is a p-type AlGaN layer located on the portions of the parallel layer that fit into all of shaped depressions 18 (1a-1c) and on other regions of the parallel layer outside those shaped depressions 18 (1a-1c). By way of example, p-type EBL 20 (FIG. 1C), which will be discussed in more detail below, may be a 5% aluminum-containing p-AlGaN layer, although other types and / or numbers of electron blocking layers may be used. p-GaN layer 14 is subsequently formed on p-type EBL 20, although other types and / or numbers of layers may be formed. As the higher temperature p-GaN 14 grows on top, the higher surface mobility leads to filling of the depressions 18 (1a-1c) shown in the example of FIG. 1C.

[0027] In the final structure, these shaped depressions 18 (1a-1c) are located adjacent to and between these two opposing charge regions, the first active layer 12 and the second active layer 14, and recombination of these charges occurs in the InGaN layers of the MQW region 16 to generate light. The depressions 18 (1a-1c) facilitate a method for easily injecting charge into the InGaN layers of the MQW region 16, especially at low currents. The depressions 18 (1a-1c) are combined with a mechanism for modifying the indium content in each indium gallium (InGaN) layer in the MQW region 16 within or around each depression 18 (1a-1c). Charges recombine preferentially in the indium-rich regions first, resulting in longer wavelength light emission.

[0028] Once the layer structure of the color-tunable LED system 10(1) is grown, the LED or other optoelectronic device can be fabricated, for example, conventionally. In forming the LED, patterning specific areas can be done, for example, by photolithography, with photoresist acting as a mask. Dry etching can then be used to selectively remove the p-type layer 14, EBL 20, and MQW region 16 that are free of photoresist to access the n-type GaN first active layer 12. The etching process forms the individual LED structures. Additionally, a top metal or other conductor (not shown) can be deposited on the p-type GaN layer 14 to form the anode. This is followed by another metal layer or other conductor (not shown) deposited on the n-type GaN layer 12, which serves as the cathode.

[0029] Color-tunable LEDs and LED systems, optionally in a common single-crystal material system, also referred to as monolithic, are fabricated according to examples of the present technology to produce light emission of desired colors across the visible spectrum, ranging from about 640 nm to about 425 nm. The color-tunable LED system depicted in FIG. 1C illustrates one example of the present technology. In this example, a low current density applied to the color-tunable LED system 10(1) produces red light emission. As the current density increases, the light emission significantly blue-shifts. This results in a color change from red to orange, yellow, green, and then blue. For smaller LEDs, a lower current is used to change the color emission compared to larger LEDs. This is because smaller LEDs have a higher current density for the same applied current as larger LEDs. As an example, for a 35 μm color-tunable LED, the current density is approximately 6×10 for red and blue, respectively. -5 ~Approx. 8×10 -2 mA / μm 2 ranges from

[0030] The emission range of the color-tunable LEDs and LED systems described herein can be tuned to emit longer or shorter wavelengths as a function of the planar indium percentage utilized. Increasing the indium percentage, such as from 18% to 25%, in the planar MQWs of MQW region 16 increases the indium content of the semipolar or nonpolar MQWs in the portion of MQW region 16 within recesses 18 (1a-1c), as well as the localized indium composition in the planar MQWs near recesses 18 (1a-1c). This shifts the overall range of light wavelengths that can be generated from one of color-tunable LED systems 10 (1) to longer wavelengths at both low and high current densities. In contrast, if the indium percentage of the designed planar MQWs in MQW region 16 is reduced, for example from 18% to 15%, recesses 18 (1a-1c) and transition region 22, which have the same incorporation density, will similarly shift the range of generated wavelengths to shorter values ​​at both low and high current densities. As less indium is incorporated into the semipolar or nonpolar MQWs in the portions of MQW region 16 within recesses 18 (1a-1c), the corresponding indium-rich regions in transition region 22 of MQW region 16 will also have less indium content.

[0031] In addition to designing three regions with substantially defined indium content, it may be desirable to modify some MQW layers with different indium content to effectively create four or more regions tuned to desired wavelength emissions and affect the variation curve of the reproducible color gamut emitted by the LED in response to changes in current density. For example, in one embodiment, reducing the indium content of the deeper and lower horizontal MQW layers can shift the emission color curve 301 toward emerald green, expanding the color gamut, as shown in FIG. 2.

[0032] In addition to engineering the shape and number of shaped recesses 18 (1a-1c) included in each color-tunable LED system 10 (1) to modify light emission, there are other techniques that can be used in conjunction with or independently. For example, individual quantum wells within the MQW region 16 may be designed to have unique indium concentrations. The unique indium concentration in each quantum well within the MQW region 16 modifies light emission. Generally, in conventional LEDs, the quantum wells within the MQW region 16 closest to the second doped region 14 are primarily responsible for light emission at low applied current densities, while quantum wells closer to the first doped region 12 contribute light emission only at high current densities.

[0033] In the color-tunable LED system 10 (1), shaped recesses 18 (1a-1c) interrupt the planar MQW region 16, but the parallel-layered, semipolar or nonpolar MQWs of the MQW region 16 located within the recesses 18 (1a-1c) are thin and have a low indium concentration, while the MQWs of the MQW region 16 adjacent to the shaped recesses 18 (1a-1c) form a transition region 22 with a high indium concentration. At low applied current densities, carrier injection occurs primarily by lateral injection from the shaped recesses 18 (1a-1c) into the transition region 22, which has a higher indium content. As the applied bias and corresponding current density increase, light generation occurs primarily by vertical injection into the planar MQW layer 16 away from the shaped recesses 18 (1a-1c) and the transition region, resulting in shorter wavelength emission. At higher current densities, further energy band bending, occupancy of excited states within the quantum wells, and occupancy of the MQW layers 16 conforming to the shaped recesses 18 (1a-1c) occurs, resulting in shorter wavelength emission. Engineering the indium content of each MQW within the MQW region 16 based on the method of current injection is extremely useful in designing the emission range, especially at moderate or high injection currents. At low current densities, emission is less dependent on the vertical distance between each quantum well within the MQW region 16 due to the lateral current injection mechanism.

[0034] Tailoring the indium content of each MQW within the MQW region 16 can be advantageous for better tailoring green and blue emission, contributing to improved and / or wider coverage of the visible color space, as shown in FIG. 2. In an exemplary embodiment, the quantum wells closest to the second doped region 14 retain a standard amount of indium, resulting in an increased indium concentration in the transition region 22 located near the shaped recesses 18 (1a-1c) corresponding to the desired longer wavelength emission. Quantum wells located further from the second doped region 14 within the MQW region 16 may have a 1-15% lower indium content compared to the quantum wells closest to the second doped region 14. Quantum wells with lower indium content located further from the second doped region 14 may function to enhance shorter wavelength emissions, such as green and blue, as vertical current injection becomes dominant at high current densities.

[0035] It should be understood that the wide color gamut shown in Figure 2 may be applicable to any and / or all color gamuts disclosed herein. In particular, the color gamuts shown in Figures 4, 5, and 8A-8C may be expanded (e.g., in the green and / or blue regions) based on the methods, techniques, and systems disclosed herein.

[0036] By individually optimizing and designing the quantum wells within the MQW region 16 to enhance blue emission, the parabolic coverage of the color gamut in the green and blue color spaces can be expanded from the unoptimized color gamut coverage 300 to the expanded optimized color gamut coverage 301.

[0037] Color-tunable LED systems 10(1) with individually optimized quantum wells within MQW region 16 can similarly be formed using selective growth or selective etching, followed by surface treatment and regrowth of MQW region 16 and second doped region 14. Alternatively, a strain-controlled buffer layer disposed beneath MQW region 16 can be designed so that V-groove or V-pit shaped depressions 18(1a) are nucleated on existing dislocations and formed during growth of MQW region 16.

[0038] In one method of operating an LED in one of the exemplary color-tunable LED systems shown in FIG. 1C, a positive bias is applied to the anode and the cathode is held at ground. Alternatively, the cathode can be held at a negative bias relative to the grounded p-contact. When such a bias is applied, holes are injected from the p-type GaN region 14 into the MQWs in the MQW region 16 and recombine with electrons to generate light. However, before this occurs, in some instances, the holes must first overcome an energy barrier provided by an optional EBL (electron blocking layer) 20. The use of an EBL 20 between the p-type GaN layer 14 and the MQW region 16 creates a large barrier for electrons and a smaller barrier for holes. The semipolar or nonpolar plane of the recess 18 (1a-1c) in one of the exemplary designed color-tunable LED systems 10 (1) has a reduced internal piezoelectric field, thereby reducing the barrier to holes provided by the EBL 20. This allows holes (h+) to be injected laterally rather than vertically into the indium-rich MQWs, more easily resulting in longer wavelengths, such as red light emission. Further increases in current density allow holes to be injected vertically, populating the planar MQWs located away from each recess 18 (1a-1c), producing shorter wavelength colors, such as green. Further increases in current density result in continued band bending, combined with hole population of the thin MQWs within each recess 18 (1a-1c), producing even shorter wavelengths, such as blue. These mechanisms achieve current-driven, color-tunable emission.

[0039] Taking advantage of the current-controlled color tunability of the color-tunable LED system 10(1), a pulsed current drive scheme can be advantageously used. Controlling the duty cycle and current level of the applied current can provide brightness control for each monolithic color-tunable LED system 10(1). To achieve equal color brightness, red has the highest duty cycle at a low current density. Blue operates at a high current density and has the lowest duty cycle of any color. Intermediate colors operate at currents and duty cycles separated by red and blue. The drive differences for red, blue, and green for equal brightness are graphically illustrated (not to scale) in Figure 3. Adjusting the duty cycle and current density for each wavelength allows the eye or detector to integrate over a period so that the perceived intensity appears the same for each color. The current applied over a period can take many forms, including, but not limited to, a square wave, a sine wave, or a ramp.

[0040] By utilizing a duty cycle and current density tailored for each desired emission wavelength / color, a full-color emission can be achieved from the LED system 10(1) and the color-tunable LEDs of a pixel in an LED display system. Traditionally, three LEDs are used to form a pixel, with each LED emitting either red, green, or blue. Uniquely enabled by color-tunable LEDs fabricated in accordance with examples of the present technology, the number of individual LEDs used in a pixel can be reduced to as few as one. One or more color-tunable LED systems 10(1) can be driven such that multiple pulsed wavelengths are emitted during each period of the duty cycle, resulting in the perception of a single observed color. An example of such an approach may include emitting red and blue light in a single period, producing purple or pink light, due to the color-mixing characteristics of Figures 4A and 4B. Color gamut 400 represents the range of a single emission wavelength / color. The current density duration of red (401) and blue (402) controls the weight of each wavelength, determining the color of the emission during that period (403). By increasing the blue current density duration relative to the current density duration used to balance the intensity with red, purple is emitted. By increasing the red current density duration relative to the current density duration used to balance the intensity with blue, pink is emitted. A similar principle can be used between green and red wavelengths to emit yellow / orange hues, or between blue and green wavelengths for cyan hues. Mixing blue (402) and yellow (405) wavelengths can be utilized in conventional lighting to emit white light (406) that appears to the observer, as shown in Figures 5A and 5B. Mixing wavelengths to generate different colors in a single period is possible using the color-tunable LED system 10(1), allowing a single LED to act as a pixel. Instead of fixed operating points for red, green, and blue, the color tunability of the color-tunable LED system 10(1) allows any color to be generated using rapidly varying currents in a single cycle. This allows a single LED to function as a single pixel element with full color capabilities.

[0041] Having the color-tunable LED system 10(1) function as a single pixel element can be realized in various display architectures. By way of example, pixel elements can be arranged together to form a passive matrix to form a display system. Additionally, additional device elements can be included with the color-tunable LED system 10(1) to form the basis of the pixel element. An example of this is a transistor integrated with the color-tunable LED system 10(1) to form the basis of the pixel element, but many other device elements, such as additional transistors, resistors, and capacitors, may also be integrated. These pixel elements, including device elements, can be similarly arranged to form an LED display system, such as a device element including a transistor electrically connected to an LED to control its operating state, including on / off, brightness, etc. If the transistor or other device element connected to the LED in the LED display system uses the same material system as the LED, these example display systems include a common single-crystal material or monolithic color-tunable LED display system. The pixel elements arranged to form a display system may further be integrated with additional circuitry, such as, by way of example, a driver circuit to provide voltage and current to the array. This additional driver circuitry can take the form of an external chip and circuit, or it can take the form of circuitry that is monolithically integrated into a common single crystal material with the color-tunable LED.

[0042] Thus, as shown and described by the examples herein, examples of the present technology provide color-tunable, optionally common single-crystal material or monolithic LED systems and LED display systems that can be effectively utilized in several different applications, such as displays, commercial lighting, and communications. In particular, examples of the present technology provide for the integration of color-tunable LEDs without the need for color converters. This feature reduces the complexity of the LED system and provides better performance in terms of improved brightness and efficiency. Examples of the present technology can provide color-tunable LEDs without Eu doping, the use of porous GaN substrates, or nanowire growth.

[0043] As with the exemplary embodiments described herein, each color-tunable LED can function as a pixel element, each capable of rapidly switching between two or more emission wavelengths in response to rapid changes in its corresponding drive current density, resulting in the perception of a single color by the human eye. Individual light-emitting diode pixel elements can be arranged in large numbers, as shown in FIG. 6A, to create a complete display system of any desired shape or resolution. Multiple color-tunable LEDs can be combined and arranged to form a complete, optionally monolithic, LED display system. In other examples of this technology, a functioning pixel element can optionally include two or more monolithic color-tunable LEDs, each with shaped recesses 18 (1a-1c) of the same or different density or design patterned in the first active doped layer 12, capable of emitting visible light of various or fixed colors.

[0044] In other examples of the present technology, color-tunable LEDs can have additional components added to create the basis of pixel elements. The additional components can take the form of device elements such as, for example, transistors, capacitors, and diodes. The device elements, along with the color-tunable LED system 10(1), can be electrically connected to form various circuits, such as, for example, current sources and active matrix circuitry for each pixel element. The pixel elements can function such that each color-tunable LED system 10(1) rapidly switches between two or more emission wavelengths in response to corresponding rapid changes in drive current density, resulting in a single color perceived by the eye. Individual pixel elements can be arrayed multiple times to create a complete color-tunable LED display system of any desired shape or resolution.

[0045] In instances where the color-tunable LED system 10(1) is included in a pixel element, additional circuitry may be integrated to provide voltage and current signals to drive the LED array, which together may comprise an LED display system. The circuitry may take the form of an external chip, or may be integrated on-chip with the LEDs, optionally creating a monolithic LED display system.

[0046] The color-tunable LED system 10(1) and color-tunable LED display systems described and claimed herein offer many advantages and can be effectively utilized in several different applications, such as microdisplays and larger format displays, commercial lighting, and light-based data communications. In particular, examples of the present technology provide color-tunable LEDs that can emit light across the entire visible spectrum without the need for additional color converters. This reduces complexity, provides superior performance, and reduces cost for many applications.

[0047] Additionally, in other examples, a single color-tunable LED system 10(1) can be configured to function as a pixel, or brightness center, either alone or in conjunction with adjacent subpixels, rather than the typical RGB approach of selectively emitting red, green, and blue LEDs commonly used in the past. Reducing the number of LED subpixels used to form a pixel increases potential display resolution and reduces footprint. This footprint reduction is particularly advantageous for μ-LED displays intended for near-eye applications such as virtual or augmented reality. It also reduces costs and allows for more efficient manufacturing.

[0048] As shown in FIG. 6A, multiple color-tunable light-emitting diode (LED) elements 610 can be arranged in an array 600 to form an image reconstruction and color reproduction electronic display according to one embodiment of the present application. Each LED can be tuned to emit a given color from a range of colors. This color tunability is enabled by current density, as more fully described in U.S. Patent Application Publication US 2022 / 0367754 A1, the entire contents of which are incorporated herein. For example, a first color 310 (shown in FIG. 8A) may be selected and emitted in an exemplary LED element, such as the LED element 610 shown in FIG. 6A. This LED element 610 can then be tuned to a second (or subsequent) color 320 for another period of time. If this other color(s) is / are switched back to the first color and then quickly switched back to another color, the human visual system (HVS) perceives this as a combined color 330. This process is well known in the art as field sequential color (FSC). In this embodiment, a first field 1 and a second field 2 are repeatedly alternated over time as shown in Figure 7. In some embodiments, the time-varying application of current can be set to a frequency greater than 48 Hz. Such a rate tends to correspond to the flicker fusion frequency of HVS.

[0049] The color of the LED 610 is set by the current, according to the process taught in U.S. Patent Application Publication US 2022 / 0367754 A1. The brightness (i.e., the amount of energy emitted) is set by the pulse width. This second process is also known in the art as pulse width modulation. The combination of these two processes can be applied in novel ways to these LED displays disclosed herein and in commonly owned U.S. Patent Application Publication US 2022 / 0367754 A1. Because the temporally mixed (FSC) color point 330 can be reproduced with other emission color points 340 and 350, there is a range of other color combinations known in the art as metamers. In Figure 8A, metamers for color point 330 are colors on the range of possible colors between first color 310 and second color 350 on one side of color arc 300, and colors corresponding to these metamers are between first color 320 and second color 340 on the other side of color arc 300. This means that theoretically, there are an infinite number of metamer combinations for each color point 330. In practice, in a digital quantization system, only a finite number are available, depending on the bit depth of the limiting function block.

[0050] One well-known problem with FSC technology is a phenomenon called color break-up, often manifesting as a "rainbow edge." Color break-up occurs when the viewer's gaze moves across the screen and colors no longer blend together. Engineers have explored various solutions. The most common approach is to increase the field rate. A drawback of this approach is that power consumption increases with rate. Utilizing the novel features of this application in combination with a better understanding of HVS, the most satisfactory approach is disclosed herein.

[0051] FIG. 6B shows the LED light-emitting element array 600 of FIG. 6A , including a two-color pattern—for example, the first color 340 (from the first LED emitter) and the second color 350 (from the second LED emitter) shown in FIG. 8A . These two colors are spatially mixed by the HVS to produce the perceived color point 330. Note further that (in other embodiments), the first LED emitter can emit color point 340 in field 1. In the following field 2, the same LED emitter 610 can emit color point 350, as shown in FIG. 6C . Thus, in a single LED emitter 610, the LEDs are operating in a field sequential color (FSC) reproduction that is perceived by the HVS as color point 330. The combination of a spatial pattern, known in the art as spatial dithering, and an FSC sequence creates a novel color spatiotemporal dither pattern, powerfully resolving the color breakup problem that is difficult to solve using FSC alone.

[0052] It should be understood that not all colors have a metameric range. For some colors, i.e., colors that lie along a single emission wavelength / color 300 range or colors that lie along the purple 360 ​​line (e.g., magenta 365 shown in FIG. 8B), there is only one set of emission color combinations that can be mixed to reproduce the desired perceived color. Because colors that lie along a single emission wavelength range have a curved range in color space, any two non-identical emission colors can reproduce a perceived color within the curved boundary. Therefore, the system uses the same colors for both the field and pattern of the spatiotemporal dither. That is, there may be no dither pattern available (except in the mathematical sense of a degenerate pattern).

[0053] While most colors have a range of available metamers, some metamer combinations may be more desirable for a given application. For example, in some embodiments, it may be desirable to use metamers that result in the smallest perceived luminance difference, allowing spatiotemporal dither patterns to appear smooth and uniform in the luminance channel of an HVS. In some cases, it may be desirable to select the metamer pair that consumes the least amount of power, given that the emitted color is controlled by current. These different choices are sometimes referred to as metamer policies.

[0054] Approximately in the center of the color gamut is a line 370 of colors to be reproduced; colors on this line have equal luminance characteristics, which are used when metamer pairs with approximately equal y values ​​are selected. For colors on either side, one emitting color must be brighter than the other, resulting in a luminance difference. For these colors, it may be best to select a metamer pair whose y value multiplied by the desired luminance is substantially equal in perceived luminance. The resulting metamer pair has similar luminance, which reduces the likelihood of visible spatiotemporal artifacts.

[0055] 9A is a top-level block diagram 900 of one possible embodiment of drive electronics for a display contemplated by the present application. Traditionally, displays transmit color information for each pixel in digital values ​​R*G*B* quantized with tristimulus gamma. These may be converted to linear RGB values ​​by a gamma conversion function block 910. This may be a simple look-up table (LUT), as described in detail in U.S. Pat. No. 8,411,022, incorporated herein by reference. This may be followed by a novel metamer selection function block 920.

[0056] To simplify the metamer selection and luminance calculation problems, RGB values ​​may be converted to any of several tristimulus values ​​known in the art, one of which is luminance, e.g., xyY, or a functional equivalent. The xy values ​​are used to select an unscaled metamer pair and the relative luminance ratio between them. This relative luminance value is further scaled by the relative luminance used to obtain the desired luminance value. This relative luminance is determined taking into account the different inherent energies emitted by LEDs at different emission wavelengths due to differences in the current used to control the emission color. After the metamer pair is selected, only one emission color is selected for each pixel per field. In addition to the emission color value (i.e., the desired current), there is also a desired luminance value (i.e., the desired pulse width). Both of these values ​​may be in digital form.

[0057] In one embodiment, it may be advantageous to select the metamer policy and metamer pair selection "offline," i.e., using mathematical formulas on a computer or manually, for a selected set of colors to be reproduced. In online hardware, the color space set may be stored in a larger lookup table that is used directly, or in a smaller lookup table (LUT) for interpolating metamer pairs between selected pre-computed metamers. Such an arrangement has the advantages of not only simplifying the computation, but also making the selection from the range of available metamer pairs causal and decidable, when otherwise it may be an ill-posed problem.

[0058] The high-level metamer selection block 920 shown in Figure 9A is shown in more detail in Figure 9C. The input is linearized RGB data that is converted to xyY color space by color space converter block 921 according to methods well known in the art. The x and y values ​​are the chromaticity coordinates of the input color on the CIE 1931 color space 300 shown in Figures 8A and 8B. The Y value is the luminance of that color point.

[0059] The xy color points are used as indexes into a metamer lookup table (MLUT) block 922, which outputs the relative luminance of the metamer pair and the maximum luminance value (MaxY) that such a color can have. The relative luminance of the metamer pair defines where the color lies along the line of colors that the metamer pair can reproduce. Given that the color-tunable LED system 10(1) may have different light output efficiencies at different emitted colors, the relative luminance can also encode and compensate for this. Therefore, it is useful to determine the selected metamer pair and its corresponding relative luminance value offline and store it in the MLUT block 922. The third value stored and retrieved is the maximum luminance (MaxY) that a color at a given xy color point can have.

[0060] The ratio of a color's Y to MaxY may then be used to scale the relative intensities of the two colors of the metameric pair by intensity scaling block 923 as follows: Relative luminance X (Y / MaxY) = luminance value

[0061] The color and luminance values ​​are passed to a spatiotemporal pattern generation block 924 which may select one color of the pair to emit given the field and pixel location, which may be the checkerboard pattern shown in Figures 6B and 6C, or any other pattern deemed desirable in a particular implementation of this embodiment.

[0062] The color and brightness values ​​are passed to a digital-to-analog converter 930 shown in Figure 9A. A color-tunable micro light-emitting diode (μ-LED) array 940 receives and stores the analog voltages to control the current and pulse width of each pixel.

[0063] FIG. 9B shows an LED pixel element with its drive and control circuit 945. It should be understood that this is only one schematic diagram, and that one skilled in the art could design functionally equivalent circuits in other ways. The pixel element and its drive and control circuit 950 may consist of a micro-LED 941 connected in series with an adjustable constant current supply element 942 and a power switch 943. The adjustable constant current supply element 942 may be controlled by a voltage held by a sample-and-hold circuit 944, which receives a voltage value from a color value signal. The power switch 943 may be controlled by a comparator circuit element 946, which compares a pulse-width modulated (PWM) value obtained from a sample-and-hold circuit 947 with a pulse-width modulated ramp generated by a pulse-width ramp generator 950. The timing of the sample-and-hold circuit may be controlled by a common data scan signal, such as that used in active matrix display backplanes.

[0064] FIG. 10 shows a μ-LED array 1000 including orthogonally arranged color-tunable μ-LED emitters 1010 and a less densely arranged array of fixed-color μ-LED emitters 1020. Referring to FIG. 10 and FIG. 8C , which illustrates the CIE 1931 chromaticity diagram, the color-tunable μ-LED emitters 1010 may be tunable along the “yellow line” 390 between wavelengths substantially red 350 and green 380, while the fixed-color μ-LED emitters 1020 may be substantially blue 320. This layout is substantially optimized for the way HVS utilizes long wavelengths along the right side of the CIE 1931 chromaticity diagram shown in FIG. 8C to obtain high-resolution luminance information. It should be understood that very short wavelength blue light, around approximately 950 nm, is not well sampled by the eye and is not focused when the long wavelengths are in focus.

[0065] Of course, many other layouts are possible and are contemplated as being within the scope of this application.

[0066] 11 shows a high-level block diagram of a display system implementing one embodiment of the present application. The gamma-quantified R*G*B* tristimulus color values ​​can be input to a gamma correction lookup table (LUT) 910 to output linear RGB values. These values ​​are stored in a line buffer 1120, and the data is provided to a sub-pixel rendering (SPR) block 1125. The SPR block 1125 utilizes an SPR filter. The blue color plane values ​​may be filtered using the following filter kernel: 0.25 0.25 0.25 0.25

[0067] This filter provides an average blue color that is mapped to the surrounding color-tunable μ-LEDs 1010, but since the μ-LEDs 1010 may not be able to provide the desired blue light needed for full color reproduction, the blue light can be provided by the blue μ-LEDs 1020.

[0068] The red (R) and green (G) values ​​may optionally be modified using the following filter kernel that samples the blue color plane: -1 -1 -1 -1 +8 -1 (divide by 8 scaled by blue brightness) -1 -1 -1

[0069] Adding this value to the red and green values ​​provides a means of reconstructing the high spatial frequency luminance contribution that the blue value would have provided if the blue μ-LED sub-pixels had the same density (resolution) as the color-tunable μ-LEDs.

[0070] The R'G'B' data from the SPR is passed to the LUT 1130, which maps the data to values ​​used by the combination of color-tunable and fixed-color μ-LEDs in the μ-LED array 1140. The R / G color is based on the ratio of R' to G', which specifies a given hue along the "yellow line." The R+G value is the desired brightness value as a percentage of pulse-width modulation. This value adjusts the brightness of the combined red (R') and green (G') values, as well as the efficiency of the color-tunable μ-LEDs 1010 at each given R / G value. The B" value is the desired brightness value as a percentage of pulse-width modulation, adjusted based on the efficiency of the blue μ-LEDs 520 at each given B" value. The advantage of using a LUT instead of a complex mathematical algorithm is that the LUT 1130 can be programmed for different μ-LED arrays, reducing manufacturing costs by using the same image processor design.

[0071] The digital values ​​from the LUT 1130 are passed to a digital-to-analog (D / A) converter 1150, which provides analog voltages used by the drivers 1140 of the μ-LED array.

[0072] The color-tunable μ-LED 1010 includes a driver circuit as shown in FIG. 5B and detailed above. The fixed blue μ-LED 1020 can eliminate the color value sample-and-hold circuit and have a driver that provides a fixed-value constant current source.

[0073] Fig. 12 shows a top view of a μ-LED array 1200 including an array of color-tunable μ-LED emitters 1210 arranged in an orthogonal pattern and fixed-color μ-LED emitters 1220 arranged at the same density. Referring to Fig. 12 and Fig. 8C showing the CIE 1931 chromaticity diagram, the color-tunable μ-LEDs 1210 may be tunable between wavelengths substantially red 350 and green 380, i.e., along the "yellow line" 390, while the fixed-color μ-LEDs 1220 may be substantially blue 320. The system achieves full color reproduction and image reconstruction by using two sub-pixels per pixel, where an input pixel can be mapped to a color-tunable μ-LED and an adjacent fixed blue-emitting μ-LED.

[0074] FIG. 13 shows a high-level block diagram of a display system implementing one embodiment of the present application. The gamma-quantized R*G*B* tristimulus color values ​​are input to a LUT 1330, which maps the data to values ​​utilized by a combination of color-tunable and fixed μ-LEDs in a μ-LED array 1340. The R / G color is based on the ratio of R to G that specifies a given hue along the "yellow line." The R+G value is the desired luminance value as a percentage of pulse-width modulation. This value adjusts the luminance of the combined red (R) and green (G) values ​​as well as the efficiency of the color-tunable μ-LEDs 1210 at each given R / G value. The B" value is the desired luminance value as a percentage of pulse-width modulation, adjusted based on the efficiency of the blue μ-LEDs 1220 at each given B" value. The advantage of using a LUT instead of complex mathematical algorithms is that the LUT1330 can be programmed for different μ-LED arrays and the same image processor design can be used, reducing manufacturing costs.

[0075] Enumeration of Embodiments The following embodiments are presented to illustrate certain aspects of the present disclosure and are not intended to limit its scope. Use of the words "include," "includes," and / or "including" hereinafter encompasses all meanings of "comprise," "comprises," "comprising," "consisting of," "comprising essentially of," and / or the like.

[0076] A first embodiment includes an LED system capable of emitting light of various peak wavelengths in response to changes in drive current density, the system including one or more pixel elements each including one or more LEDs, each of the one or more LEDs including: a first active doped layer on a substrate, the first active doped layer selectively patterned with recesses of one or more shapes and having one or more spacing configurations along one surface opposite the substrate to promote controlled color emission in the MQW layers of the MQW region; MQW regions formed across one surface of the first active doped layer, each MQW layer alloyed with a percentage of indium that promotes controlled color emission, the portion of the MQW layer that fits in the recess having a lower indium alloy percentage than other portions of the MQW layer, the indium alloy percentage decreasing with distance from the portion of the MQW layer that fits in the recess; and a second active doped layer formed over the MQW region, the second active doped layer being opposite in charge to the first active doped layer.

[0077] A second embodiment includes any of the first embodiments, and further includes a transition region between each of the portions of the MQW layer that fit into the recesses and each of the other portions of the MQW layer, the transition region having a higher concentration of indium alloy percentage than the other portions of the MQW layer.

[0078] The third embodiment includes any one of the first and second embodiments, and further includes an electron blocking layer included in the second active doped layer.

[0079] A fourth embodiment includes any one of the first to third embodiments, and further includes that the recess has an inner surface angled at an angle of 0 to 90 degrees relative to the substrate.

[0080] A fifth embodiment includes any one of the first to fourth embodiments, and further includes that the recess has an inner surface angled at an angle of 90 degrees to 180 degrees relative to the substrate.

[0081] A sixth embodiment includes any of the first to fifth embodiments, and further includes that the recesses are spaced apart from one another by a distance between 150 nm and 10 μm.

[0082] A seventh embodiment includes any of the first to sixth embodiments, and further includes that the difference in depth between each of the recesses is less than about 5 μm.

[0083] An eighth embodiment includes any of the first to seventh embodiments, and further includes that the one or more shapes of the periphery of the depression include one or more circles, triangles, squares, pentagons, or hexagons.

[0084] A ninth embodiment includes any one of the first to eighth embodiments, and further includes that the LED system is formed entirely from a common single material system.

[0085] A tenth embodiment includes any of the first to ninth embodiments, and further includes one or more drive circuit elements coupled to each of the one or more pixel elements.

[0086] An eleventh embodiment includes any (or none) of the first through tenth embodiments, and is a method of making an LED system capable of emitting light of various peak wavelengths in response to changes in drive current density, the method including forming one or more pixel elements each including one or more LEDs, the forming including providing a first active doped layer on a substrate, and selectively patterning the first active doped layer along one surface opposite the substrate with recesses in one or more shapes and having one or more spacing configurations to promote controlled color emission in the MQW layer of the MQW region. forming MQW regions across a surface of one of the first active doped layers, each of the MQW layers being alloyed with a percentage of indium that promotes controlled color emission, the portion of the MQW layer that fits into the recess having a lower indium alloy percentage than other portions of the MQW layer, the alloy percentage of indium decreasing with distance from the portion of the MQW layer that fits into the recess; and forming a second active doped layer over the MQW region, the second active doped layer being opposite in charge to the first active doped layer.

[0087] A twelfth embodiment includes any (or none) of the first through eleventh embodiments, and further includes providing a transition region between each of the portions of the MQW layer that fit into the recess and each of the other portions of the MQW layer, the transition region having a higher concentration of indium alloy percentage than the other portions of the MQW layer.

[0088] A thirteenth embodiment includes any (or none) of the first through twelfth embodiments, and further includes forming an electron blocking layer between the MQW region and the second active doped layer.

[0089] A thirteenth embodiment includes any (or none) of the first to twelfth embodiments, and further includes the recess having an inner surface angled at between 0 and 90 degrees relative to the substrate.

[0090] A fourteenth embodiment includes any (or none) of the first to thirteenth embodiments, and further includes that the recess has an inner surface angled at between 90 degrees and 180 degrees relative to the substrate.

[0091] A fifteenth embodiment includes any (or none) of the first to fourteenth embodiments, and further includes the depressions being spaced apart from one another by a distance between 150 nm and 10 μm.

[0092] A sixteenth embodiment includes any (or none) of the first through fifteenth embodiments, and further includes that the difference in depth between each of the recesses is less than about 5 μm.

[0093] A seventeenth embodiment includes any (or none) of the first through sixteenth embodiments, and further includes that the one or more shapes of the perimeter of the depression include one or more of a circle, a triangle, a square, a pentagon, or a hexagon.

[0094] An eighteenth embodiment includes any (or none) of the first through seventeenth embodiments, and further includes the LED system being formed entirely from a common single material system.

[0095] A nineteenth embodiment includes any (or none) of the first through eighteenth embodiments, and further includes forming one or more drive circuit elements coupled to each of the one or more pixel elements.

[0096] A twentieth embodiment includes any (or none) of the first through nineteenth embodiments, and is a method for controlling one or more colored emissions, the method including providing an LED system including a first active doped layer, an MQW region, and a second active doped layer, the first active doped layer being selectively patterned along one surface opposite the substrate with recesses having one or more spacing configurations in one or more shapes to promote controlled color emissions in the MQW layer of the MQW region, the MQW region extending across one surface of the first active doped layer. wherein each of the MQW layers is alloyed with a percentage of indium that promotes controlled color emission, the portion of the MQW layer that conforms to the recess having a lower concentration of indium alloy percentage than other portions of the MQW layer, the alloying percentage of indium decreasing with distance from the portion of the MQW layer that conforms to the recess; a second active doped layer is formed on the MQW region that is opposite in charge to the first active doped layer; and the method further includes varying the application of current to the LED system over time to change the one or more color emissions.

[0097] A 21st embodiment includes any (or none) of the 1st to 20th embodiments, and further includes that varying the application of current over time further includes varying the duty cycle and current level for each wavelength of emitted light.

[0098] A 22nd embodiment includes any (or none) of the 1st to 21st embodiments, and further includes that the varying the application of current over time has a frequency greater than 48 Hz.

[0099] A 23rd embodiment includes any (or none) of the 1st to 22nd embodiments, and further includes wherein the varying the application of current over time further includes mixing two or more wavelengths, each having a unique current level and duty cycle within a single time period.

[0100] A twenty-fourth embodiment includes any (or none) of the first through twenty-third embodiments, and is an LED system capable of emitting light of various peak wavelengths in response to changes in drive current density, the system including one or more pixel elements each including one or more LEDs, each of the one or more LEDs including a first active doped layer on a substrate selectively patterned with recesses of one or more shapes and having one or more spacing configurations along one surface opposite the substrate to promote controlled color emission in an MQW layer of the MQW region. and a second active doped layer formed on the MQW region, the second active doped layer being opposite in charge to the first active doped layer.

[0101] The twenty-fifth embodiment includes any one (or none) of the first to twenty-fourth embodiments, and further includes an electron blocking layer between the MQW region and the second active doped layer.

[0102] A 26th embodiment includes any (or none) of the first through 25th embodiments and further includes a method for controlling a μ-LED display, the μ-LED display including a plurality of LED elements, each LED element including a plurality of MQW regions, each such MQW region selectively doped to emit one or more desired color wavelengths, each LED element emitting a perceived single color wavelength that is a composite color of the desired color wavelengths of each MQW region, the method including driving a first LED element for a first period to emit the first color in a first field, and driving the first LED element for a second period to emit a second color in a second field to affect a field sequential color that includes a perceived composite color of the first color and the second color.

[0103] A 27th embodiment includes any (or none) of the first to 26th embodiments, and further includes the first color of the first field and the second color of the second field forming a first metamer for a single perceived color wavelength.

[0104] A 28th embodiment includes any one (or none) of the first to 27th embodiments, and further includes a second LED element adjacent to the first LED element being driven in a first field to emit a second color, and being driven in a second field to emit the first color.

[0105] A twenty-ninth embodiment includes any (or none) of the first to twenty-eighth embodiments, and further includes the μ-LED display affecting spatial dither.

[0106] A thirtieth embodiment includes any (or none) of the first to twenty-ninth embodiments, and further includes the μ-LED display affecting a field sequential color sequence.

[0107] A thirty-first embodiment includes any (or none) of the first to thirtieth embodiments, and further includes the first LED element being driven for a third period to emit a third color in a third field, the first element being driven for a fourth period to emit a fourth color in a fourth field, and the third color and the fourth color being perceived as the same color as the first metamer.

[0108] A thirty-second embodiment includes any (or none) of the first to thirty-first embodiments, and further includes that the desired perceived color can be rendered by a range of metamers selectable from a first set of colors and a second set of colors.

[0109] A thirty-third embodiment includes any (or none) of the first to thirty-second embodiments, and further includes that the metamers selected to render the desired perceived color include metamers that result in the smallest perceived luminance difference.

[0110] A thirty-fourth embodiment includes any (or none) of the first to thirty-third embodiments, and further includes that the metamer selected to render the desired perceived color includes a minimum power metamer.

[0111] A thirty-fifth embodiment includes any (or none) of the first through thirty-fourth embodiments, and further includes a μ-LED display including a plurality of LED elements, each LED element including a plurality of MQW regions, each such MQW region selectively doped to emit one or more desired color wavelengths, each LED element emitting a perceived single color wavelength that is a composite color of the desired color wavelengths of each MQW region, the μ-LED display further including a metamer selection block receiving image input data, the image input data indicating a desired color to be rendered and a desired brightness, the metamer selection block calculating a metamer selection and a brightness to be rendered by said LED element and at least one adjacent LED element, and said LED element and at least one adjacent LED element rendering the desired color and desired brightness in a spatiotemporal scheme.

[0112] A thirty-sixth embodiment includes any (or none) of the first to thirty-fifth embodiments, and further includes the LED element and the at least one LED element rendering a first color and a second color, respectively, and the first color and the second color forming a metamer for a desired color to be rendered.

[0113] A thirty-seventh embodiment includes any (or none) of the first to thirty-sixth embodiments, and further includes the LED elements and at least one LED element being assigned relative brightness values ​​to render a desired brightness.

[0114] A thirty-seventh embodiment includes any (or none) of the first to thirty-sixth embodiments, and further includes that the metamer selection block further includes a lookup table of pre-computed metamers.

[0115] A thirty-eighth embodiment includes any one of the first to thirty-seventh embodiments (or none of them), and further includes that the metamer selection block further includes a spatiotemporal pattern generation block.

[0116] A thirty-ninth embodiment includes any (or none) of the first to thirty-eighth embodiments, and further includes the spatiotemporal pattern generation block selecting the color and brightness of each LED element according to an LED pattern including a μ-LED display.

[0117] A fortieth embodiment includes any (or none) of the first to thirty-ninth embodiments, and further includes that the LED pattern includes one of a group, and the group includes an array of LED elements, a checkerboard of LED patterns.

[0118] A forty-first embodiment includes any (or none) of the first to fortieth embodiments, and further includes that the μ-LED display further includes a sub-pixel rendering (SPR) block.

[0119] A 42nd embodiment includes any (or none) of the 1st to 41st embodiments, and further includes that the SPR filter includes a kernel that affects sub-pixel rendering to adjacent LED elements.

[0120] Having thus described the basic concepts of the present technology, it will be apparent to those skilled in the art that the above detailed disclosure is intended to be given by way of example only, and not by way of limitation. Although not expressly stated herein, it will be apparent to those skilled in the art that various changes, improvements, and modifications are conceivable and intended. These changes, improvements, and modifications are intended to be suggested by this specification and are within the spirit and scope of the present technology. Furthermore, the described order of process elements or sequences, or the use of numbers, letters, or other designations, are therefore not intended to limit the scope of the present invention.

Claims

1. 1. A method for controlling a μ-LED display, the μ-LED display including a plurality of LED elements, each LED element including a plurality of MQW regions, each such MQW region capable of selectively emitting one or more desired color wavelengths, each LED element emitting a perceived single color wavelength that is a composite color of the desired color wavelengths of each MQW region, the method comprising: driving a first LED element for a first period of time to emit a first color in a first field; driving the first LED elements for a second period to emit a second color in a second field to affect a field sequential color comprising a perceived composite color of the first color and the second color; The method comprising:

2. 2. The method of claim 1, wherein the first color of the first field and the second color of the second field form a first metamer for the perceived single color wavelength.

3. 3. The method of claim 2, wherein a second LED element adjacent to the first LED element is driven in the first field to emit the second color and is driven in the second field to emit the first color.

4. The method of claim 3 , wherein the μ-LED display affects spatial dither.

5. The method of claim 4, wherein the μ-LED display affects a field sequential color sequence.

6. 3. The method of claim 2, wherein the first LED element is driven for a third period to emit a third color in a third field, and the first element is driven for a fourth period to emit a fourth color in a fourth field, and the third color and the fourth color are perceived as the same color as the first metamer.

7. The method of claim 2 , wherein the desired perceived color can be rendered by a range of metamers selectable from a first set of colors and a second set of colors.

8. The method of claim 7 , wherein the metamers selected to render the desired perceived color include metamers that include the smallest difference in perceived luminance.

9. The method of claim 7 , wherein the metamer selected to render the desired perceived color comprises the metamer with the lowest power.

10. A μ-LED display comprising a plurality of LED elements, each LED element comprising a plurality of MQW regions, each such MQW region being selectively doped to emit a desired color wavelength, each LED element emitting a perceived single color wavelength that is a composite of the desired color wavelengths of each MQW region, the μ-LED display comprising: a metamer selection block receiving image input data, the image input data indicating a desired color to be rendered and a desired brightness; the μ-LED display, wherein the metamer selection block calculates a metamer selection and a brightness to be rendered by the LED element and at least one adjacent LED element, and the LED element and the at least one adjacent LED element render the desired color and the desired brightness in a spatiotemporal scheme.

11. 11. The μ-LED display of claim 10, wherein the LED element and the at least one LED element render a first color and a second color, respectively, the first color and the second color forming a metamer for the rendered desired color.

12. The μ-LED display of claim 11 , wherein the LED elements and the at least one LED element are assigned relative brightness values ​​to render the desired brightness.

13. The μ-LED display of claim 12, wherein the metamer selection block further comprises a look-up table of pre-calculated metamers.

14. The μ-LED display of claim 13 , wherein the metamer selection block further comprises a spatiotemporal pattern generation block.

15. The μ-LED display of claim 14, wherein the spatiotemporal pattern generation block selects the color and brightness of each LED element according to an LED pattern comprising the μ-LED display.

16. The μ-LED display of claim 14, wherein the LED pattern comprises one of a group, the group comprising an array of LED elements, a checkerboard of LED patterns.

17. The μ-LED display of claim 16, further comprising a sub-pixel rendering (SPR) block.

18. The μ-LED display of claim 17, wherein the SPR block includes a plurality of SPR filters, each of the SPR filters including a kernel that affects sub-pixel rendering to adjacent LED elements.

Images