Display, Apparatus and Method

Abstract

Methods and devices are presented for converting a dense grid layout of micro LED emitters into a square rectilinear pixel grid layout to achieve compatibility with hardware and software used in imaging and display technologies. In particular, a pattern of regular hexagonal emitter cells for fabrication on III-nitride substrates can be converted into a square pixel array of easily addressable irregular hexagonal three-color pixels. Isolation between adjacent three-color pixels and their constituent emitters can be established to overlap tolerance while maintaining a cell packing density of about 70% and a pixel pitch of about 4.0 μm. Wavelength and quantum efficiency characteristics are shown to be dependent on the photocurrent density, which can be determined by the emitter area specified in the grid layout.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 299,702, entitled "TRI-COLOR PIXEL LAYOUT," filed January 14, 2022, which is incorporated by reference in its entirety.

[0002] This disclosure relates to display technology, and in particular to micro LED emitters for use in heads-up displays and headsets for virtual reality and augmented reality experiences. [Background technology]

[0003] Mobile display devices, such as touch screens or heads-up displays, may incorporate pixel grids or arrays of light generating elements or emitters. Some display devices use sub-micron sized light emitting diodes, or "micro-LEDs," as light sources. Each pixel in the array may be formed as a single micro-LED emitter tuned to a particular wavelength, or color, of light, e.g., one of the primary light colors, i.e., red, green, or blue. Alternatively, each pixel may be formed as a group of micro-LED emitters. The number and arrangement of the constituent micro-LED emitters determines the color and intensity of the light emission from each pixel of the array in response to an electrical signal applied to the emitter. Summary of the Invention

[0004] The present disclosure describes methods and devices that can be used to convert a dense grid layout of micro-LED emitters to a square rectilinear (e.g., substantially square rectilinear) grid layout of micro-LED emitters for compatibility with hardware and software used in imaging and display technologies. In particular, a pattern of regular hexagonal emitter cells for fabrication on a III-nitride substrate can be converted to a square pixel grid of easily addressable (e.g., addressable via a backplane, etc.) irregular three-color pixels. Separation between adjacent three-color pixels, and between their constituent emitters, can be established for overlap tolerance while maintaining, for example, a cell packing density of about 70% and a pixel pitch of, for example, about 4.0 μm. The emitter area can be adjusted to control the photocurrent density, which can in turn affect the wavelength sensitivity and quantum efficiency of the micro-LED during operation.

[0005] In some aspects, the technology described herein relates to a method, the method including converting a grid of regular hexagonal light emitters having sides of equal length and equal angles between the sides into a square grid of pixels having a set of at least four pixels within a boundary having a length dimension equal to a width dimension, and converting the square grid of pixels into a square rectilinear grid of pixels. Each of the pixels from the square rectilinear grid of pixels includes a first irregular hexagonal light emitter, a second irregular hexagonal light emitter, and a third irregular hexagonal light emitter. The square rectilinear grid of pixels includes a first pixel adjacent to the second pixel, the first pixel having a centroid aligned with the centroid of the second pixel along a first direction. The square rectilinear grid of pixels includes a third pixel adjacent to the second pixel, the third pixel having a centroid aligned with the centroid of the second pixel along a second direction orthogonal to the first direction.

[0006] In some aspects, the technology described herein relates to an apparatus including a blue emitter having a hexagonal shape and a blue emitter region, and a green emitter having a hexagonal shape and a green emitter region, where a first side of the green emitter is parallel to a first side of the blue emitter. The apparatus includes a red emitter having a hexagonal shape and a red emitter region that is larger than the blue emitter region and larger than the green emitter region, where the first side and the second side of the red emitter have different lengths.

[0007] In some aspects, the technology described herein relates to an apparatus, the apparatus including a substrate, a III-nitride layer on the substrate, and a layout of tri-color pixels formed in the III-nitride layer, each tri-color pixel having a pixel area. The apparatus includes three monochrome micro LED emitters having different emitter areas. The apparatus includes a metal contact disposed on a corresponding one of the three monochrome micro LED emitters. The metal contact has a contact area. A ratio of the contact area to the area of ​​the corresponding one of the three monochrome micro LED emitters is based on a color of the corresponding one of the three monochrome micro LED emitters.

[0008] In some aspects, the technology described herein relates to a display, the display includes a first plurality of III-nitride blue emitters emitting blue light, each blue pixel having a first area. The display includes a second plurality of III-nitride green emitters emitting green light, each green pixel having a second area. The display includes a third plurality of III-nitride red emitters emitting red light, each red pixel having a third area. The third area is at least 1.5 times larger than the first area and at least 1.5 times larger than the second area.

[0009] In some aspects, the technology described herein relates to a method, the method includes selecting a pixel area, a red luminous flux, and a red wavelength for a red InGaN micro LED emitter in a pixel array of a display, and determining a red emitter area and an operating current density for the red InGaN micro LED emitter. When the red InGaN micro LED emitter operates at an operating current, light is emitted at at least a red luminous flux having a wavelength of at least a red wavelength, and the red emitter area is between 10% and 90% of the pixel area. The method includes fabricating a display including a plurality of red InGaN micro LED emitters.

[0010] In some aspects, the technology described herein relates to a display, the display including a pixel array having a pixel having a pixel area, and a plurality of red InGaN micro light emitting diodes (micro LEDs) in the pixel array. The red InGaN micro LEDs have a red luminous flux, a red wavelength, and a red emitter area between about 10% and about 90% of the pixel area. The display is configured to operate such that the pixel array emits red light with at least a red luminous flux having a wavelength of at least a red wavelength.

[0011] The foregoing summary, as well as other illustrative objects and / or advantages of the present disclosure, and the manner in which they are accomplished, are further described in the following detailed description and accompanying drawings. [Brief description of the drawings]

[0012] [Figure 1A] 1 is a layout of a linear three-color pixel array according to a possible embodiment of the present disclosure. [Figure 1B] FIG. 1B is a close-up view of a single tri-color pixel of the array shown in FIG. 1A, according to a possible embodiment of the present disclosure. [Diagram 2] 2A and 2B show a layout of a regular hexagonal emitter array and a layout of a linear three-color pixel array derived from the layout of the regular hexagonal emitter array according to possible embodiments of the present disclosure. [Diagram 3] 2C is a flow chart of a method for converting the regular hexagonal emitter array shown in FIG. 2A into a rectilinear three-color pixel array shown in FIG. 2B according to a possible embodiment of the present disclosure. [Figure 4] 4 illustrates operations of the method shown in FIG. 3 according to a possible embodiment of the present disclosure. [Diagram 5] 4 illustrates operations of the method shown in FIG. 3 according to a possible embodiment of the present disclosure. [Figure 6] 4 illustrates operations of the method shown in FIG. 3 according to a possible embodiment of the present disclosure. [Figure 7] 4 illustrates operations of the method shown in FIG. 3 according to a possible embodiment of the present disclosure. [Figure 8] 4 illustrates operations of the method shown in FIG. 3 according to a possible embodiment of the present disclosure. [Figure 9] 4 illustrates operations of the method shown in FIG. 3 according to a possible embodiment of the present disclosure. [Figure 10] 4 illustrates operations of the method shown in FIG. 3 according to a possible embodiment of the present disclosure. [Figure 11] 11 is a flowchart of a method for designing a display having the three-color pixel array shown in FIGS. 8, 9, and 10 according to a possible embodiment of the present disclosure. [Figure 12] 1 is a plot illustrating the behavior of a III-nitride red micro LED when operated over a range of current densities, according to possible embodiments of the present disclosure. [Figure 13] 1 is a plot illustrating the behavior of a III-nitride red micro LED when operated over a range of current densities, according to possible embodiments of the present disclosure. [Figure 14] 1 is a plot illustrating the behavior of a III-nitride red micro LED when operated over a range of current densities, according to possible embodiments of the present disclosure. [Figure 15] 1 is a plot illustrating the behavior of a III-nitride red micro LED when operated over a range of current densities, according to possible embodiments of the present disclosure. [Figure 16]1 is a plot illustrating the behavior of a III-nitride red micro LED when operated over a range of current densities, according to possible embodiments of the present disclosure. [Figure 17] 1 is a plot illustrating the behavior of a III-nitride red micro LED when operated over a range of current densities, according to possible embodiments of the present disclosure. [Figure 18] FIG. 4 is a block diagram of a computer system for executing the method shown in FIG. 3 according to a possible embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The elements in the drawings are not necessarily to scale relative to each other and like reference numerals indicate corresponding parts throughout the several views.

[0014] Some displays utilize hexagonal micro LED elements fabricated on a semiconductor substrate that includes III-nitride materials with a hexagonal crystal structure. Examples of such III-nitride materials include gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium nitride (AlGaN), aluminum indium nitride (AlInN), aluminum indium gallium nitride (AlInGaN), and other alloys. Each micro LED may correspond to one monochrome emitter, or subpixel, of the display, and a group of three subpixels (e.g., red, green, and blue) may constitute a tri-color pixel.

[0015] In some implementations, the emitters can be formed monolithically, for example, all three colors can be formed on the same epitaxial growth substrate, which can be called a III-nitride substrate. For example, a semiconductor wafer with a GaN buffer (e.g., on sapphire or silicon or bulk GaN) can be used as the epitaxial growth substrate, and micro LEDs of all three colors can be formed on this substrate by a sequence of epitaxial growth operations and other processing operations. The semiconductor wafer can be further processed into a semiconductor die that can be attached to a backplane to form a display.

[0016] A simple layout of an array or grid of hexagonal micro LED emitters can be problematic because the groups of three emitters that form pixels are not properly aligned for ease of addressing. As a result, such arrays may not be compatible with existing software or hardware configured for use with other array shapes in which the pixels are rectilinear, e.g., aligned in both the x and y directions. Furthermore, a regular hexagonal emitter array would create a rectangular pixel array instead of a square pixel array. In other words, if the shape of the hexagonal emitters were regular, with equal sides and equal angles, the pixel placement would be irregular and therefore difficult to access.

[0017] The techniques described below can be implemented to modify the hexagonal shape of the sub-pixels to create a pixel array design that is both nearly square and nearly rectilinear. That is, the emitter shapes are stretched and irregular, resulting in a regular arrangement of pixels. In the resulting layout, the sub-pixels have hexagonal shapes with sides of different lengths, and emitters of different colors have different areas. The cells are still hexagonal, but their shapes are irregular. In one example, the red emitters have an area 1.5 times larger than the areas of the blue and green emitters.

[0018] One technical advantage of converting the pixel layout in this way is that it makes the array of hexagonal emitters compatible with existing technology (e.g., hardware and software) used to program and drive displays. Another technical advantage is that by changing the shape and size of the red emitters, the photocurrent density of the emitted light is changed. This affects the properties of the emitted light, such as peak wavelength, wavelength sensitivity, and quantum efficiency, when the array is operated. Thus, not only is it more convenient to convert the design of the array, but changing the layout can also have a direct operational effect on the capabilities of the display device.

[0019] Figure 1A shows the layout of an example tri-color pixel array 100, according to a possible embodiment of the present disclosure. Figure 1A is a high-level diagram that is further detailed in the following description. Tri-color pixel array 100 is the desired result of a series of transformations described below to address the shortcomings of displays that include an array of regular hexagonal emitters.

[0020] The tri-color pixel array 100 groups emitters 102 into a square array of tri-color pixels 104, one of which is shown in black outline in FIG. 1A. In the illustrated example, the tri-color pixel array 100 is also a rectilinear 3×3 array of tri-color pixels 104. Alternate tri-color pixels 104 have inverted (opposite) orientations. In some implementations, each tri-color pixel 104 has three constituent emitters 102, i.e., sub-pixels, to include triplets of all three primary colors. Each tri-color pixel 104 can be manipulated or scaled to output light of a selected color by adjusting the relative contributions of the three primary color components. The light contribution of each primary color component to create the color of the pixel can be increased or decreased, for example, by adjusting the light intensity of the emitter or the micro-LED cell size, e.g., the area of ​​the cell.

[0021] In some implementations, the constituent emitters 102 of each tri-color pixel 104 are monochrome micro-LED emitters of primary colors of light, such as a green emitter 102G, a blue emitter 102B, and a red emitter 102R. The blue emitter 102B may be characterized by a peak wavelength in the range of about 430 nm to about 490 nm. The green emitter 102G may be characterized by a peak wavelength in the range of about 510 nm to about 570 nm. The red emitter 102R may be characterized by a peak wavelength in the range of about 590 nm to about 680 nm.

[0022] 1B shows an example of a single three-color pixel 104, but enlarged for clarity. In some implementations, each emitter 102 in the three-color pixel 104 has an irregular hexagonal shape, in which six sides s1, s2, s3, s4, s5, and s6 each have a different length, and the angles between adjacent sides are all equal, e.g., 120 degrees. Within each three-color pixel 104, one side, e.g., side s4 of the green emitter 102G, is parallel to a side, e.g., s1, of the red emitter 102R, and another side, e.g., s3 of the green emitter 102G, is parallel to a side, e.g., s6, of the blue emitter 102B. The blue emitter 102B also has a side, e.g., s5, that is parallel to a side, e.g., s2, of the red emitter 102R.

[0023] The irregular hexagonal shapes of the various emitters are formed to square the dimensions of the tri-color pixel array 100, and subsets thereof. Although the hexagonal shapes may appear distorted, the angles between the six sides of each emitter are maintained at approximately 120 degrees, consistent with the crystal structure of the emitter material. The corners of the hexagons can be slightly rounded and still fit the design of the tri-color pixel array 100.

[0024] Specifically, some embodiments may have a wurtzite crystal structure and an LED grown along the c-axis of the wurtzite structure. In such embodiments, the hexagonal emitter may have six sides aligned with the m-axis of the wurtzite structure or with the a-axis of the wurtzite structure. The sides may be vertical, in which case the sides may be m-planes or a-planes, respectively, or they may be tilted, in which case the sides may be semipolar planes along the c-m axis or along the c-a axis, respectively.

[0025] In some implementations, the areas of the component red, green, and blue emitters are different. In the illustrated example, the area of ​​the red emitter 102R is larger than the area of ​​the green emitter 102G, which in turn is larger than the area of ​​the blue emitter 102B. In one possible implementation, the area of ​​the red emitter 102R is about 1.5 times the area of ​​the green emitter 102G and about 1.5 times the area of ​​the blue emitter 102B. In one possible implementation, the area of ​​the red emitter 102R is at least 1.5 times the area of ​​the green emitter 102G and at least 2.0 times the area of ​​the blue emitter 102B. The pixel pitch 106 can be defined as the distance between corresponding emitters of adjacent tri-color pixels 104, for example, the distance between each pair of nearest neighboring green emitters 102G. In the illustrated example, the pixel pitch 106 is approximately 4.0 μm in both the x and y directions.

[0026] The emitters 102 within each tri-color pixel 104 are shown as adjacent in Figures 1A and 1B. However, in some implementations, there may be a space or gap between the parallel sides of adjacent emitters 102. The tri-color pixels 104 are shown spaced apart from one another by a pixel perimeter 108. When the emitters 102 and tri-color pixels 104 are spaced apart from one another, light emission from the tri-color pixel array 100 may be reduced compared to an array in which the emitters 102 and / or tri-color pixels 104 are adjacent. However, such spacing may be desirable for other reasons (e.g., ease of manufacture or added optical isolation).

[0027] FIG. 2A shows an emitter array 200 of regular hexagonal emitters 202 according to possible embodiments of the present disclosure. The emitter array 200 serves as a starting point, which can undergo various transformations to result in the three-color pixel array 100 reproduced in FIG. 2B. In some embodiments, the regular hexagonal emitters 202 are monochrome micro LED cells, and the shape of the regular hexagonal emitters 202 in FIG. 2A is a regular hexagon. That is, the six sides of the regular hexagon, e.g., sides s1, s2...s6, are equal in length, and the six angles between adjacent sides of the regular hexagon, e.g., θ1, θ2...θ6, are each 120 degrees. In some embodiments, each monochrome regular hexagonal emitter 202 emits either red, green, or blue light. The equilateral equiangular emitter centers 203, shown as black circles in FIG. 2A, are each located at the spatial average of the points along the perimeter of the hexagonal cell. An equilateral isometric emitter center 203 can be defined by constructing centerlines that bisect each pair of opposite sides. For example, centerline m1 bisects sides s1 and s4, centerline m2 bisects sides s2 and s5, and centerline m3 bisects sides s3 and s6. The equilateral isometric emitter center 203 is then located at the intersection of the three centerlines m1, m2, and m3.

[0028] Each non-overlapping group of three RGB regular hexagonal emitters 202 can be grouped into an RGB triplet 204. An example RGB triplet 204 is outlined in black in FIG. 2A. The RGB triplet 204 has a triad center 205, symbolized in FIG. 2A by a black triangle. Because the regular hexagonal emitters 202 have a regular hexagonal shape, the triad center 205 is located at the intersection of the three regular hexagonal emitters 202 within the RGB triad 204.

[0029] In order to maximize the packing density of the regular hexagonal emitters 202, it may be advantageous to form a layout of the regular hexagonal emitters 202 as in the emitter array 200. In FIG. 2A, there are no spaces between the regular hexagonal emitters 202. That is, all of the regular hexagonal emitters 202 are adjacent to each other or in contact with each other such that the packing factor characterizing the packing area of ​​the emitter array 200 is 100%. In some examples, the regular hexagonal emitters 202 may be separated from each other by a separation distance such that the regular hexagonal emitters 202 are not adjacent and the packing factor is less than 100%. However, the packing factor of such an emitter array 200 having separated regular hexagonal emitters 202 is still significantly greater than the target of, for example, 60%.

[0030] Another advantage of the hexagonal cell is that a micro-LED emitter formed on a III-nitride substrate (e.g., a gallium nitride (GaN) substrate, or a GaN layer on another type of substrate) exhibits the hexagonal crystal structure of GaN, in which the crystal planes have a separation angle of 120 degrees. That is, the hexagonal shape of the regular hexagonal emitter 202 is inherent to the crystal structure of GaN-based micro-LED cells. In some implementations, other substrate materials can be used, such as other materials with a hexagonal crystal structure, such as silicon carbide (SiC), particularly 4H-SiC.

[0031] One problem with the emitter array 200 shown in Figure 2A is that it is not linear. That is, the emitter centers 203 of adjacent regular hexagonal emitters 202 are aligned only in one direction, e.g., the x-direction and not the y-direction, as shown by the dashed lines connecting adjacent circular emitter centers 203. Similarly, the triplet centers 205 are aligned only in one direction, e.g., the y-direction and not the x-direction, as shown by the dashed lines in Figure 2A connecting adjacent triangular pixel centers 205. This is a result of all other R-G-B triplet 204 being in the opposite orientation relative to adjacent triplet.

[0032] Another problem with the emitter array 200 shown in Figure 2A is that the emitter array 200 is not square. That is, the size of an nxn-subset of the emitter array 200 does not have substantially equal horizontal (width w) and vertical (length l) dimensions in the x- and y-directions, respectively. For example, in Figure 2A, the width w of a 2x2 subset of the emitter array 200 that includes four adjacent RGB triplet 204 is less than its length l, and thus the boundary of the 2x2 subset, shown as a solid box in Figure 2A, is not square. This is shown in more detail in Figure 4.

[0033] FIG. 2B shows, for comparison with FIG. 2A, a tri-color pixel array 100 that is a square linear array of emitters 102 having an irregular hexagonal shape according to a possible embodiment of the present disclosure. In some embodiments, the emitters 102 are monochrome micro LED emitters, and the shape of the emitters 102 in FIG. 2B is an irregular hexagon. That is, the sides of the hexagon, e.g., sides S1, S2, ... S6, are not equal in length. However, despite the irregular hexagonal shape, the angles between adjacent sides of the emitters 102, e.g., θ1, θ2, ... θ6, remain at 120 degrees. In some embodiments, as described above, each of the emitters 102 is a monochrome emitter that emits either red, green, or blue light. The emitter center 213, represented by a black circle, is located at the spatial average of the points along the perimeter of the emitters 102. Despite its irregular shape, the emitter center 213 of the emitter 102 can be found geometrically by constructing three centerlines M1, M2, and M3 and locating their intersections, in a manner similar to that described above for the regular hexagonal emitter 202.

[0034] Each non-overlapping R-G-B triplet of an irregular hexagonal emitter 102 is defined as a tri-color pixel 104. An example tri-color pixel 104 is outlined in black in FIG. 2B. The tri-color pixel 104 has a pixel centroid 215, symbolized in FIG. 2B by a black triangle. Due to the specific shapes of the constituent irregular hexagonal emitters 102, the pixel centroid 215 does not generally coincide with a side or corner, or an intersection 216, of the irregular hexagonal emitter 102. Instead, the pixel centroid 215 is located at the spatial average of each of the emitter centers 213 of the emitters 102 within the tri-color pixel 104. Thus, the pixel centroid 215 is located above an intersection of the irregular hexagonal emitters 102 within the tri-color pixel 104. For the adjacent three-color pixels to the left and right of each three-color pixel 104, the pixel centroids 215 are located below, e.g., offset from, the intersections of the constituent emitters 102 because the adjacent three-color pixels in the x-direction are inverted with respect to the three-color pixel 104.

[0035] In the example shown in FIG. 2B, the three-color pixel array 100 is rectilinear, such that adjacent pixel centroids 215 are substantially aligned in both the x-orthogonal and y-orthogonal directions along the dashed lines shown in FIG. 2B. Such alignment of the pixel centroids 215 allows the pixels 204 to be located along a common axis such that they are easily addressable (e.g., addressable via a backplane). It may therefore be advantageous to arrange the three-color pixels 104 in such a rectilinear array to facilitate programming and application of control signals and to fit conventional displays. These advantages do not require precise alignment of the pixel centroids 215. For example, in the top left pixel 104 where the dashed lines meet, the corner marked by the pixel centroid 215 may be a somewhat rounded corner, and the advantages of the arrangement shown in FIG. 2B over that shown in FIG. 2A apply.

[0036] Moreover, the tri-color pixel array 100 is a square grid array in which the width W of the 3×3 tri-color pixel array 100 is approximately equal to its length L. Furthermore, an n×n subset of the tri-color pixel array 100, for example, any 2×2 pixel array within the tri-color pixel array 100, is also square, having substantially equal horizontal (width) and vertical (length) dimensions in the orthogonal x and y directions, respectively.

[0037] In the three-color pixel array 100 shown in Figure 2B, adjacent three-color pixels 104 are spaced apart from one another by a distance D. Due to the spaces between the three-color pixels 104, the fill factor of the square rectilinear grid shown in Figure 2B is less than 100%, e.g., in the example shown, the fill factor is about 70%. Thus, the packing density of the emitters 102 is somewhat compromised by the square rectilinear arrangement of the three-color pixels 104 in order to achieve the desired alignment.

[0038] FIG. 3 illustrates a method 300 for converting an emitter array 200 into a three-color pixel array 100 according to a possible embodiment of the present disclosure. The method 300 outlines a series of steps for converting an emitter array 200 of regular hexagonal emitters 202 into a square rectilinear three-color pixel array 100 of three-color pixels 104. For illustrative purposes, the operations shown in FIG. 3 are described with reference to a geometric transformation and are illustrated in FIGS. 4 to 9, which are diagrams of intermediate arrays at various stages of the transformation according to some embodiments. The operations of the method 300 may be performed in a different order or may not be performed depending on the particular application. It should be noted that the method 300 may not generate a complete three-color pixel array. It is therefore understood that additional processes may be performed before, during, or after the method 300, and some of these additional processes may be briefly described herein. In a possible embodiment, the method 300 includes operations 302 to 310, which are described below with reference to FIGS. 4 to 10.

[0039] FIG. 4 overlays the graph 400 with the layout of the emitter array 200 shown in FIG. 2A to highlight its shortcomings. FIG. 4 shows that the boundaries of the 3×3 grid of RGB triplet 204 are not square, and that when three-color pixels are defined as RGB triplet 204, the resulting pixel grid is not rectilinear. In FIG. 4, each RGB triplet is represented by a “Y” connecting emitter centers 203. The center of each “Y” coincides with a triplet center 205. The triplet centers 205, represented by black triangles, are collinear in the y direction, but not in the x direction, as shown by the dashed lines. As a result, the pixel grid based on the emitter array 200 is not rectilinear. Furthermore, the emitter array 200 has a width of about 11.6 μm and a length of about 12.8 μm, as measured against the graph 400, indicating that the emitter array 200 is not square.

[0040] At 302, the emitter array 200 of regular hexagonal emitters 202 can be converted into a square emitter array 500 according to a possible embodiment of the present disclosure, as shown in Figure 5. The square emitter array 500 is an intermediate layout that can be computer generated according to a set of design rules. Figure 5 shows the square emitter array 500 as a solid line superimposed on the emitter array 200, which is shown as a dotted line.

[0041] In a possible implementation, the conversion to a square emitter array 500 involves the process of laterally expanding the regular hexagonal emitters 202 to create enlarged hexagonal emitters 502 (three shown: 502-0, 502-1, and 502-2) while maintaining the angle and height of the enlarged hexagonal emitters 502. Because the original emitter array 200 is longer than it is wide, the lateral expansion of the regular hexagonal emitters 202 increases their width, making the emitter array 200 square. Starting from the central axis of the emitter array 200, shown as a dashed line, the right side s3 of the central enlarged hexagonal emitter 502-0 expands or stretches a distance d0 in the +x direction, and the left side of the enlarged hexagonal emitter 502-0 extends the same distance d0 in the -x direction. Meanwhile, the right side of the enlarged hexagonal emitter 502-1, located to the right of the enlarged hexagonal emitter 502-0, extends in the +x direction by a distance d1 that is greater than d0. Similarly, the right side of the enlarged hexagonal emitter 502-2, located to the right of the enlarged hexagonal emitter 502-1, extends in the +x direction by a distance d2 that is greater than d1, and so on. A similar series of lateral extensions in the -x direction can be made for the hexagonal emitters located to the left of the central enlarged hexagonal emitter 502-0. The distances d0, d1, and d2...dn can be selected to make the overall square emitter array 500 and any n x n subset of non-overlapping RGB triplets 504 have square dimensions. For example, the resulting single RGB triplet 504 has substantially equal length and width dimensions, and the 4×4 subset of RGB triplet 504 also has substantially equal length and width dimensions.

[0042] In a possible implementation, when the original emitter array 200 has a width w that is greater than its length l, the conversion to a square emitter array 500 may involve vertically expanding the height of the regular hexagonal emitters 102 to produce longer emitters, instead of the lateral expansion described above to produce extended emitters 502. In such a case, both the angle and width of the hexagonal emitters 502 are preserved, but the height is increased.

[0043] At 304, the square emitter array 500 can be converted into a square rectilinear tri-color pixel array 600 of tri-color pixels 104 according to a possible embodiment of the present disclosure, as shown in Figure 6. The square rectilinear tri-color pixel array 600 is an intermediate layout that can be computer generated according to a set of design rules. The square rectilinear tri-color pixel array 600 is referred to as a pixel array rather than an emitter array because the repeating elements of the array are the tri-color pixels 104, outlined in black here in Figure 6.

[0044] The three-color pixels 104 form a rectilinear pixel grid when the three-color pixels 104 are collinear in each of two orthogonal directions. Figure 6 shows a square linear tri-color pixel array 600 in solid lines overlaid on a square pixel array 500, which is shown as a dotted line. Like the square emitter array 500, the square linear tri-color pixel array 600 has a 100% fill factor because the three-color pixels 104 are adjacent.

[0045] At 306, the conversion to the square linear three-color pixel array 600 involves a process of further horizontal expansion or contraction of the extended hexagonal emitter 502. By expanding or contracting the selected sides of the emitter, the relative emitter areas occupied within each three-color pixel 104 can be adjusted. In a possible embodiment, by converting to the square linear three-color pixel array 600, an irregular hexagonal emitter 102 is created while maintaining the original 120-degree angle, i.e., while each vertex of the hexagon holds a 120-degree angle. In the example shown in FIG. 6, all sides of the red emitter 102R are expanded, but sides s2, s4, and s6 are expanded by a greater distance E towards the blue emitter 102B, and sides s1, s32, and s5 are expanded by a shorter distance e towards the green emitter 102G. The expansion of the sides of the red emitter 102R causes their emitter areas to expand. Further, all sides of the blue emitter 102B contract, but sides s2, s4, and s6 adjacent to the green emitter 102G contract by a smaller distance e, while sides s1, s3, and s5 contract by a greater distance E. The contraction of the sides of the blue emitter 102B reduces their emitter areas. Additionally, some sides of the green emitter 102G contract and other sides of the green emitter 102G expand. In the illustrated example, sides s2, s4, and s6 adjacent to the red emitter 102R contract by a smaller distance e, while sides s1, s3, and s5 adjacent to the blue emitter 102B expand by an intermediate distance ε, where e < ε < E in this case, and thus the area of the green emitter 102G can increase, decrease, or remain the same. The irregular hexagonal emitters 102R, 102G, and 102B have emitter centers indicated by black circles in FIG. 6. Similar to the regular hexagon of the pixel array 100, the emitter centers associated with the irregular hexagonal emitters 102 are located at the intersections of three centerlines that bisect both sides of the hexagon. The pixel centroid 215 of the three-color pixel 104 is represented by a black triangle in FIG. 6. The pixel centroid 215 is positioned by finding the spatial average of the red emitter center, the green emitter center, and the blue emitter center. The pixel centroids 215 are collinear in both the x-direction and the y-direction that are orthogonal to each other, as indicated by the dashed lines.Thus, the tri-color pixels 104 that make up the square rectilinear tri-color pixel array 600 are made rectilinear by expanding and contracting the various emitters 102 as described above. Note that the intersections where the three irregular hexagonal emitters 102 come together are not rectilinear because they are not collinear in the x-direction.

[0046] In FIG. 6, the expansion and contraction distances E, e, and ε can be selected to produce a desired pixel color, which can be determined by the relative areas of the red emitter 102R, the green emitter 102G, and the blue emitter 102B, which are not equal to one another. When the emitter areas of the red, green, and blue emitters 102R, 102G, and 102B each constitute the same percentage of the pixel area of ​​the three-color pixel 104, as in FIG. 6, the composite pixel color will be uniform across all of the three-color pixels 104 of the square rectilinear three-color pixel array 600. In the illustrated example, the areas of the red and green emitters 102R and 102G are larger than the area of ​​the blue emitter 102B, and therefore the red and green emitters contribute more to the composite pixel color than the blue emitter. In some implementations, the ratio of the red, green, and blue emitter areas can be 3:2:1. However, the relative areas can be changed by different selections of the expansion and contraction distances. In some implementations, the color of a pixel can change when the constituent emitters are illuminated with different power levels, resulting in differences in light intensity among the three emitters.

[0047] At 308, pixel separation can be incorporated into the square rectilinear three-color pixel array 600, as shown in FIG. 7, to create the three-color pixel array 100 according to possible embodiments of the present disclosure. The three-color pixel array 100 includes gaps between each of the adjacent irregular hexagonal three-color pixels 104. In some implementations, the gaps can be formed in the layout of the rectilinear three-color pixel array 100 by constructing a pixel perimeter 108 of constant width D / 2 around each of the three-color pixels 104 such that adjacent three-color pixels 104 are separated from each other by a total pixel separation distance D. In some implementations, the pixel separation distance D can be about 0.25 μm. In FIG. 7, the boundaries of the three-color pixels 104 are shown as solid lines and the pixel perimeter 108 is shown as dotted lines. In some implementations, the pixel perimeter 108 can be formed by shrinking the boundaries of the three-color pixels 104. In some implementations, the pixel perimeter 108 may be formed by expanding the dimensions of the tri-color pixel array 100 to add space between the tri-color pixels 104 .

[0048] In some implementations, the pixel separation distance D can be selected to achieve a desired pixel pitch 106, defined as the distance between corresponding features of adjacent three-color pixels 104, for example, the distance from one green emitter to the next. In some implementations, the desired pixel pitch 106 is about 4 μm or less for a square separated three-color pixel array 100 measuring about 11 μm by 11 μm. When pixel separation is introduced, the resulting separated three-color pixel array 100 has a fill factor of less than 100%. In some implementations, the pixel separation distance D can be selected to meet a minimum design target that specifies, for example, a fill factor of at least 60%.

[0049] At 310, the emitters in each three-color pixel 104 may be separated to create a separated three-color pixel array 800 as shown in FIG. 8 according to possible embodiments of the present disclosure. In some implementations, the separated three-color pixel array 800 includes gaps between adjacent three-color pixels 104 and gaps between adjacent emitters in each three-color pixel 104. In some implementations, the gaps between emitters may be formed in the layout of the separated three-color pixel array 800 by constructing an emitter perimeter 802 of constant width d / 2 around each of the emitters 102 such that adjacent emitters are separated from each other by a total emitter separation distance d. In FIG. 8, the boundary 804 of the emitter 102 is shown as a solid line and the perimeter 802 is shown as a dotted line. In some implementations, the perimeter 802 may be formed by shrinking the boundary of the emitter 102. Using this method, adjacent three-color pixels 104 are separated by a combined separation distance D+d. In some implementations, the perimeter 802 can be formed by expanding a dimension of the separated three-color pixel array 800 to add space between the emitters 102. In some implementations, the perimeter 802 can be formed by shrinking adjacent sides of the emitters 102 without shrinking sides of non-adjacent emitters. Using this method, adjacent three-color pixels 104 are separated by a pixel separation distance D. Using this method, the relative areas of the different color emitters may change, which may change the overall color of the three-color pixel 104 over time.

[0050] In some implementations, the pixel separation distance D and the emitter separation distance d can be selected to achieve a desired pixel pitch 106, e.g., a pixel pitch of about 4.0 μm or less. In some implementations, the pixel separation distance D and the emitter separation distance d can be selected to meet a minimum design goal specifying a fill factor, e.g., a fill factor of at least 60%. In some implementations, the pixel separation distance D and the emitter separation distance d can be selected to achieve a desired total emitter area within each three-color pixel 104, e.g., a total emitter area that is at least about 55% of the pixel area.

[0051] Referring to FIG. 9, possible embodiments of the present disclosure may incorporate a separation material between adjacent pixels and / or between adjacent emitters to form a gap. FIG. 9 shows a cross-sectional view 900 of a portion of a tri-color pixel 104 including one green emitter 102G and one red emitter 102R. As described above, the tri-color pixel 104 may be constructed on a substrate 902 that may include GaN or another III-nitride material. Each micro LED emitter 102 may have an InGaN-containing active region, e.g., an InGaN quantum well. The red emitter 102R may have an InGaN quantum well with an indium composition greater than 20% (e.g., 25%, 30%, or 35%). In some implementations, one or more of the micro LED emitters, e.g., emitters 102R and 102G, may have somewhat sloping sidewalls such that the base of the emitter 102 is wider than the top surface of the emitter 102, causing the emitter 102 to have a mesa-shaped profile. In a top-down view, the footprint, or "projected footprint," of the emitter 102 coincides with the area of ​​the base of the emitter 102. The tri-color pixel 104 may have corresponding footprints that include the footprints of the red, green, and blue emitters of its constituent emitters 102R, 102G, and 102B, respectively.

[0052] A pixel isolation region 904 can be formed in the substrate 902 to form a gap next to the three-color pixel 104 or next to the green emitter 102G. The pixel isolation region 904 optically isolates the green emitter 102G from an adjacent emitter of the three-color pixel 104 adjacent to the left of the green emitter 102G. The pixel isolation region 904 can be formed around a pixel or around a subpixel. In some implementations, the pixel isolation region 904 can be made of an electrically insulating or dielectric material or dielectric stack, which can include, for example, one or more of silicon dioxide (SiO2), silicon nitride (SiN), silicon oxynitride (SiON), aluminum oxide (AlO2), tantalum oxide (TaO2), or titanium oxide (TiO2). In some implementations, the pixel isolation regions 904 may be made of a reflective material, such as a metal or metal stack including one or more of silver (Ag), aluminum (Al), gold (Au), titanium (Ti), nickel (Ni), platinum (Pt), or combinations thereof. In some implementations, the pixel isolation regions 904 may be made of a dichroic mirror material. In some implementations, the pixel isolation regions 904 may combine a dielectric layer and a reflective layer. The depth, shape (e.g., angle), and reflectivity of the pixel isolation regions 904 may be configured to facilitate reducing optical crosstalk between pixels or subpixels, i.e., to prevent light emitted at one pixel or subpixel from propagating laterally through the pixel isolation regions 904 to another pixel or subpixel.

[0053] Some implementations may include a method of jointly configuring pixel isolation regions 904 and sub-pixel layout. In some implementations, one or more figures of merit may be selected from among light extraction efficiency, i.e., luminous flux or luminance, light output expressed as either radiometric or photometric, pixel-to-pixel crosstalk, and external quantum efficiency (EQE). For each of the figures of merit, a target value may be provided. The pixel isolation regions 904 and the micro LED area may then be configured to meet the target value associated with the figure of merit. The pixel pitch 106 and / or the total area of ​​the tri-color pixel 104 may be further constraints.

[0054] In the example, the figures of merit for a 4 × 4 μm pixel area can be specified as follows: (1) less than 5% of the light emitted by the pixel propagates laterally to adjacent pixels, and (2) the luminance of the red subpixel is at least 0.1 W / cm 2 (3) the wavelength of the red subpixel should be at least 620 nm. In this example, the optical isolation can be configured (e.g., its width and depth can be varied) to reduce crosstalk and achieve (1), then the area of ​​the red subpixel can be determined to achieve (2) as taught herein, then the blue and green subpixel areas can be determined from the remaining pixel area, and finally a pixel layout can be determined that achieves the desired areas.

[0055] The pixel layouts shown herein may correspond to the shapes of various elements. For example, in some implementations, the pixel layout may correspond to the footprint of the subpixel, i.e., the shape of the base of the micro-mesa that forms the subpixel. In some implementations, the pixel layout may correspond to the shape of the active area of ​​the subpixel (e.g., red, green, and blue quantum wells). In some implementations, the pixel layout may correspond to the shape of the photolithography mask used to fabricate the subpixel. In some implementations, the mask may have a hexagonal shape as taught herein, and the resulting micro-LEDs may have a shape that is somewhat distorted from the shape of the photolithography mask (e.g., a hexagon with rounded vertices or corners).

[0056] Note that FIG. 9 further illustrates the size of metal contacts 906 (two are shown, 906G and 906R) for corresponding emitters 102G and 102R, respectively. The metal contacts 906 are disposed on corresponding emitters formed in the substrate 902. The metal contacts 906 provide access to the emitters 102 for transmitting electrical signals. In the illustrated example, the metal contacts 906G and 906R are approximately the same size for both the green emitter 1202G and the red emitter 102R, even though the corresponding areas of the emitters 102G and 102R are significantly different. Thus, the ratio of contact area to emitter area is color dependent; i.e., the ratio of contact area to emitter area is based on the color of the emitter.

[0057] FIG. 10 illustrates a three-color pixel array 1000 having an emitter separation of distance d, a pixel separation of distance D, and metal contacts 906 according to a possible embodiment of the present disclosure. In FIG. 10, the boundaries of the separated emitters 102 are shown as dotted lines, and the outlines of the metal contacts 906 are shown as solid lines. In some embodiments, the metal contacts 906 are made differently sized for each of the emitters 102 such that the metal contacts 906G, 906R, and 906B have unequal contact areas. Furthermore, the size of the metal contacts 906 may not be the same as the corresponding emitter areas. For example, as illustrated in FIG. 10, even though the emitter 102R has the largest emitter area of ​​the three emitter areas, the metal contact 906R is the smallest of the three metal contacts. The size of the metal contacts 906 may be selected to satisfy design rules governing the minimum contact width, such as 0.3 μm.

[0058] Some embodiments of the present disclosure benefit from display designs using red III-nitride micro-LEDs with improved pixel configurations due to the special properties of III-nitride red micro-LEDs, which in particular can be characterized by relatively large variations in internal quantum efficiency (IQE) and light emission wavelength as a function of input current density.

[0059] Such a display design may proceed according to method 1100 shown in FIG. 11, according to possible embodiments of the present disclosure. Method 1100 outlines a sequence of operations for fabricating a display having a three-color pixel array 100 including a dedicated red emitter 102. For illustrative purposes, the operations shown in FIG. 11 will be described with reference to the characteristics of the red emitter 102 as described in FIGS. 12 through 17. FIGS. 12 through 17 illustrate the characteristics of the operating current density J according to some embodiments. op11 is a plot illustrating the behavior of a red emitter 102 when operated at or near 1104. The operations of method 1100 may be performed in a different order, or not, depending on the particular application. It is noted that method 1100 may not produce a complete three-color pixel array 100. Thus, it is understood that additional processes may be performed before, during, or after method 1100, and some of these additional processes may be briefly described herein. In a possible implementation, method 1100 includes operations 1102 through 1106, which are described below with reference to FIGS. 11 through 17.

[0060] At 1102, in possible embodiments, a desired pixel area, maximum optical crosstalk, minimum red wavelength, and minimum red luminous flux can be selected for a red micro LED emitter 102R in a pixel array of a display, such as in a three-color pixel array 100. In some embodiments, the red micro LED emitter can include an indium gallium nitride (InGaN) light emitting layer. The current density J op Then, J op It can be determined that a red micro-LED operating at 1000 nm emits light with at least a red luminous flux and with a wavelength at least as long as the red wavelength. In designing such a display, the luminous flux and wavelength parameters can be further combined with constraints on the area of ​​the display based on a desired selection of pixel pitch 106 or based on a desired pixel area. In some implementations, the pixel area is approximately 5×5 μm 2 The area of ​​the slit 24 may be selected to be equal to or smaller than the area of ​​the slit 24

[0061] At 1104, in possible implementations, the optical isolation features can be configured to facilitate a reduction in optical crosstalk such that the crosstalk is lower than a maximum optical crosstalk. The maximum optical crosstalk can be expressed as follows: Less than 50% (e.g., less than 20%, less than 10%, less than 5%, less than 2%, less than 1%, or less than 0.1%) of the optical power emitted by a pixel propagates laterally to another pixel. At least 20% (e.g., at least 50%, at least 80%, at least 90%, at least 95%, at least 99%, or at least 99.9%) of the light emitted by the emitter of the tri-color pixel 104 exits the display within the footprint of the tri-color pixel. For a display having a pixel pitch 104 equal to P, at least 20% (e.g., at least 50%, at least 80%, at least 90%, at least 95%, at least 99%, or at least 99.9%) of the light emitted by the emitter of the tri-color pixel 104 exits the display within a circle of radius P referenced to the centroid 215 of the tri-color pixel 104 (e.g., the centroid 215 of a polygon that encloses the pixel footprint).

[0062] At 1106, a pixel layout can be determined that includes a red micro LED emitter area, the pixel area being near a desired pixel area, and the pixel layout promoting the red micro LED to emit at least a minimum red luminous flux that is at least a minimum red wavelength. Additionally, at 1104, an operating current of a red InGaN micro LED emitter, such as emitter 102R, can be determined according to possible embodiments of the present disclosure. In some embodiments, the pixel area can be specified such that the red subpixel has a red emitter area between about 10% and about 90%, or between about 20% and about 80%, or between about 20% and about 50% of the pixel area. In some embodiments, a maximum emitter area can be specified, such that the red subpixel has a red emitter area that is smaller than the maximum emitter area (e.g., about 0.5 μm 2 , 1 μm 2 , 2 μm 2 Less than or equal to 3 μm 2) red emitter area. In some implementations, the red subpixel has an area of ​​at least 15% (e.g., at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, or at least 50%) of the total pixel area. In some implementations, operations 1104 and 1106 can be performed in concert, whereby the optical isolation features and pixel layout can be jointly configured to promote the above-mentioned properties. Thus, by utilizing a sufficiently large emitter, or subpixel, some implementations can provide sufficient luminous flux at a sufficient wavelength when the InGaN micro LED emitter is operated at a determined operating current. The luminous flux from a subpixel can be expressed as a photocurrent density, defined as the photocurrent emitted by the device (e.g., by the red subpixel) divided by the area of ​​the device (e.g., the emitter area of ​​the red subpixel). By way of example, a luminous flux density of about 1×1 μm 2 A red subpixel with an emitter area of ​​1.0 mm and emitting about 10 nW of light at 620 nm would have a current of about 0.5 A / cm 2 It emits a photocurrent density of

[0063] In some embodiments, the red subpixels have a current density of at least about 0.1 Amperes / cm 2 (For example, about 0.2 amperes / cm 2 , 0.5 ampere / cm 2 , 1 ampere / cm 2 , 2 amps / cm 2 , 5 amps / cm 2 , or 10 amps / cm 2) photocurrent density with an external quantum efficiency of at least 2% (e.g., at least 3%, at least 4%, at least 5%, at least 7.5%, at least 10%, at least 12.5%, at least 15%, at least 20%, or at least 25%). In some implementations, the red subpixel can emit light with a peak wavelength of at least 590 nm (e.g., 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, or 650 nm), or with a dominant wavelength of at least 590 nm (e.g., 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, or 650 nm). A sufficiently long red wavelength can facilitate a display with a sufficient color gamut, e.g., at least sRGB, or at least DCI-P3.

[0064] The wavelength sensitivity and / or efficiency versus current density can be affected by the epitaxial structure of the III-nitride layers, for example, by the composition or thickness of the quantum well and the surrounding barrier layers.

[0065] At 1108, a display including a plurality of red InGaN micro LED emitters 102R according to embodiments of the present disclosure can be fabricated. The manufacture of the display can use established semiconductor processing techniques, and the display design specifies a pixel array layout that can be realized as a photolithography mask. The mask is created according to the pixel array layout, e.g., a three-color pixel array 100, including dimensions of selected pixel areas and red emitter areas. The mask can then be used to pattern the micro LED emitters 102R in the InGaN layer of the substrate 902, as shown in FIG. 9. In some embodiments, the emitters 102R can be spaced apart by a selected pixel pitch 106. Once the display is fabricated with appropriately sized red InGaN micro LED emitters, the display can be operated at a determined operating current.

[0066] 12 shows a plot 1200 of relative external quantum efficiency (EQE) as a function of the base 10 logarithm of the red current density J according to some embodiments of the present disclosure. FIG. 12 shows the calculated relative EQE for III-nitride red micro-LEDs when operating at various current densities. op Near , the EQE has a negative slope, so increasing the current density decreases the EQE.

[0067] FIG. 13 shows a plot 1300 of experimentally measured relative EQE data for a red III-nitride LED having similar behavior to that shown in FIG. 12. The operating current density J op =10A / cm 2 For 100A / cm 2 Approximately a ten-fold increase in current density to is accompanied by a relative EQE decrease of about 30%.

[0068] 14 shows a plot 1400 of the peak wavelength of a III-nitride red micro-LED as a function of current density J according to some embodiments of the present disclosure. op When operated near , the wavelength has a negative slope, thus indicating that increasing the current density causes the wavelength to shift to shorter wavelengths, which changes the color of the light being emitted by the red micro-LED, and therefore the color of the pixel.

[0069] FIG. 15 shows a plot 1500 of experimentally measured peak wavelength data for a red III-nitride LED having similar behavior to FIG. 14. The operating current density J op =10A / cm 2 For 100A / cm 2 Approximately a ten-fold increase in current density to 0.1 is accompanied by a wavelength shift of approximately 30 nm.

[0070] It may be desirable for red micro-LEDs to operate at a sufficiently long wavelength with a sufficiently high EQE. Thus, for a given operating current applied to a red micro-LED, the current density J opIt may be desirable to increase the area of ​​the red micro-LEDs to reduce

[0071] Thus, some embodiments provide a three-color pixel layout in which the three-color pixel has a large red emitter. In contrast to displays in which the emitters within a pixel may have similar areas, some embodiments of the present disclosure have a red emitter whose area is significantly larger (e.g., at least about 1.5 times, 1.75 times, 2 times, 2.25 times, 2.5 times, or 3 times) than the areas of the blue and green emitters. Some embodiments have a red "fill factor," or the percentage of the total area of ​​the pixel that is covered by the red emitter, in the range of at least about 15% to about 50% (e.g., about 20%, 25%, 30%, 35%, 40%, 45%, or 50%).

[0072] Table I shows 15 examples of pixel shapes along with the dimensions and fill factor for each micro LED color. The pitch, radius, and area dimensions in Table 1 are in μm, and "ff" indicates the fill factor. For "area ratio", R / B is the ratio of the red emitter area to the blue emitter area, and R / G is the ratio of the red emitter area to the green emitter area. The values ​​listed in Table 1 are for circular emitters for simplicity, but similar values ​​can be achieved with hexagonal pixels, polygonal pixels, irregular polygonal pixels, and pixels of any shape.

[0073] [Table 1]

[0074] Table I: Emitter dimensions for various pixel pitches 16 shows a device having wavelength sensitivity to current density according to some embodiments of the present disclosure. In plot 1600, the wavelength is proportional to log 10 The wavelength is shown as a function of the current density J on a scale of 100 nm. The wavelength is approximately linear as a function of the logarithm of the current density. For the operating current density J opAround 10x increase in J is associated with a 10 nm decrease in wavelength. Some embodiments are characterized by a combination of a large sensitivity to current density and a large red emitter area. The sensitivity to current density may refer to the wavelength, IQE, or EQE of the device. The sensitivity can be, for example, a function of the operating current density J op The device can be characterized when operated at a particular current density, such as by: In some embodiments, the device has a wavelength sensitivity to current density of at least 10 nm per decade (e.g., 10 nm, 15 nm, 20 nm, 25 nm, or 30 nm per decade). Thus, the current density can be characterized as the operating current density J op A ten-fold increase from will shift the wavelength by at least 10 nm (eg, 15 nm, 20 nm, 25 nm, or 30 nm).

[0075] 17 shows a device having EQE wavelength sensitivity to current density according to some embodiments of the present disclosure. In plot 1700, the relative EQE (in arbitrary units) is plotted as log 10 Current density J on the scale op as a function of the operating current density J op In the vicinity, an increase in J by a factor of 10 is associated with a 10% decrease in EQE. In some embodiments, the device has a relative EQE sensitivity, or relative IQE sensitivity, to current density of at least 10% per decade (e.g., 10%, 15%, 20%, 25%, or 30% per decade). Thus, when the current density is less than the operating current density J op A ten-fold increase from reduces the EQE by at least 10% (e.g., about 10%, 15%, 20%, 25%, or 30%).

[0076] The current sensitivity in Figures 16 and 17 is shown as the deformation of the curve over a factor of 10 and the local slope of the curve at the operating point (J op The derivative of the curve at ) can be considered instead, which is a broader definition if the curve is not linear over a factor of ten of the current density.

[0077] Methods 300 and 1100 may be automated or partially automated, and thus may be performed as a computer-implemented method using computer system 1800 shown in Figure 18. That is, acts 302 through 310 and / or acts 1102 through 1108 may be encoded in a computer program, such as application 1812, that may be executed by one or more processors 1852, e.g., microprocessors, in computer system 1800.

[0078] The system 1800 includes a computing system 1802. The computing system 1802 may also be referred to as a client computing device or client device. The computing system 1802 is a device having an operating system 1810. In some examples, the computing system 1802 includes a personal computer, a mobile phone, a tablet, a netbook, a laptop, a smart appliance (e.g., a smart TV), or a wearable device. The computing system 1802 may be any computing device with input device(s) 1830, such as a mouse, a trackpad, a touch screen, a keyboard, a virtual keyboard, a camera, etc. The computing system 1802 may include output device(s) 1824, such as a display (monitor, touch screen, headset, heads-up display, etc.) that allows a user to see and select displayed content. The computing system 1802 may include one or more processors, such as a CPU / GPU 1832, configured to execute one or more machine-executable instructions, or portions of software, firmware, or a combination thereof, formed within a substrate. One or more of the processors, e.g., CPU / GPU 1832, can be semiconductor-based microprocessors. That is, the processors can include semiconductor materials capable of executing digital logic. The computing system 1802 may include one or more memory devices 1804. The memory devices 1804 may include a main memory that stores information in a format that can be read and / or executed by the CPU / GPU 1832. The memory devices 1804 can store applications or modules (e.g., operating system 1810, applications 1812, pixel grid generation application 1818, etc.) that perform certain operations when executed by the CPU / GPU 1832.

[0079] The operating system 1810 is system software that manages the computer's hardware and software resources and provides common services to computing programs. In some examples, the operating system 1810 is operable to run on a personal computer, such as a laptop, netbook, or desktop computer. In some examples, the operating system 1810 is operable to run on a mobile computer, such as a smartphone or tablet, a watch, a headset, or other wearable computing device. The operating system 1810 may include multiple modules configured to provide common services and manage the resources of the computing system 1802. The computing system 1802 may include one or more input devices 1830 that allow a user to select content. Non-exclusive example input devices 1830 include a keyboard, a mouse, a touch-sensitive display, a trackpad, a trackball, a biometric sensor, an eye movement tracking device, and the like. The computing system 1802 may include one or more output devices 1824 that allow a user to view web pages and / or receive audio or other visual output.

[0080] The computing system 1802 may include applications 1812, which represent specially programmed software configured to perform various functions. One of the applications may be a pixel grid generator application 1818. The pixel grid generator application 1818 may be configured to generate and / or convert pixel grid information according to the operations of the method 300 and / or according to the operations of the method 1100.

[0081] In some examples, the computing system 1802 may communicate with a server computing system 1850 via a network 1840. The server computing system 1850 may be one or more computing devices in the form of a number of different devices, such as, for example, a standard server, a group of such servers, or a rack server system. In some examples, the server computing system 1850 may be a single system that shares components such as a processor and memory. The network 1840 may include the Internet and / or other types of data networks, examples of which include a local area network (LAN), a wide area network (WAN), a cellular network, a satellite network, or other types of data networks. The network 1840 may also include any number of computing devices (e.g., computers, servers, routers, network switches, etc.) configured to receive and / or transmit data within the network 1840. The network 1840 may further include any number of wired and / or wireless connections.

[0082] The server computing system 1850 may include one or more processors 1852 formed within the substrate, an operating system (not shown), and one or more memory devices 1854. The memory devices 1854 may represent any type (or types) of memory (e.g., RAM, flash, cache, disk, tape, etc.). In some examples (not shown), the memory devices 1854 may include external storage, e.g., memory that is physically remote from but accessible by the server computing system 1850. The server computing system 1850 may include one or more modules or engines that represent specially programmed software. For example, the server computing system 1850 may include a system for managing and accessing user account(s) 1860. The user account 1860 may include data that a user has requested to be synchronized between devices, such as the computing system 1802. The synchronized data may include session data 1862. The session data 1862 may enable a user to resume browsing activity after switching devices. The user account 1860 may also include profile data 1864. The profile data 1864 may include, with the user's consent, information describing the user. The profile data 1864 may also include data identifying the user (e.g., username and password). The user account 1860 may also include synchronized saved locations storage 1866. The saved locations storage 1866 may be a data store of the user's saved locations across devices. For example, as part of a synchronization activity, the local saved locations storage 1826 may be transmitted from the computing system 1802 to the server computing system 1850 and stored in the saved locations storage 1866.

[0083] The foregoing disclosure provides different embodiments or examples for implementing different features of the provided subject matter. To simplify the disclosure, specific examples of components and arrangements are described below. They are of course merely examples and are not intended to be limiting. For example, the formation of a first feature on a second feature in the following description may include embodiments in which the first feature and the second feature are formed in direct contact, and may also include embodiments in which an additional feature between the first feature and the second feature may be formed, and the first feature and the second feature are configured not to be in direct contact.

[0084] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present disclosure. As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used herein, the term "comprising" and variations thereof are used synonymously with the term "including" and variations thereof and are open-ended terms. As used herein, the term "optional" or "optionally" means that the subsequently described feature, event, or circumstance may or may not occur, and the description includes instances when the feature, event, or circumstance occurs and instances when it does not. As used herein, ranges may be expressed as from "about" one particular value and / or to "about" another particular value. When such a range is expressed, the embodiment includes from the one particular value and / or to the other particular value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are meant both in relation to the other endpoint, and independent of the other endpoint.

[0085] As used herein, the singular may include the plural unless the context clearly indicates otherwise in a particular instance. Spatially relative terms (e.g., "over," "above," "upper," "under," "beneath," "below," "lower," etc.) may be used to describe the relationship of one element or feature to another element or feature. Spatially relative terms are intended to encompass various orientations of the device in use or operation in addition to the orientation shown in the figures. The device may be otherwise oriented (rotated 90 degrees or to other orientations) and the spatially relative descriptors used herein may be interpreted accordingly as well. In some embodiments, the relative terms "above" and "below" may include vertically above and vertically below, respectively. In some embodiments, the term "adjacent" may include laterally adjacent or horizontally adjacent.

[0086] In some embodiments of the present disclosure, the terms "about" and "substantially" can refer to a particular quantity value that varies within 20% of the value (e.g., ±1%, ±2%, ±3%, 4%, ±5%, ±10%, ±20% of the value). These values ​​are merely examples and are not intended to be limiting. The terms "about" and "substantially" can refer to a percentage of a value as would be interpreted by one of ordinary skill in the relevant art(s) given the teachings herein.

[0087] Some embodiments may be implemented using various semiconductor processing and / or packaging technologies. Some embodiments may be implemented using various types of semiconductor processing technologies associated with semiconductor substrates, including, but not limited to, silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide (SiC), etc.

[0088] As described herein, certain features of the described embodiments have been illustrated, but numerous modifications, substitutions, changes, and equivalents will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes that fall within the scope of the embodiments. It is to be understood that these are presented by way of example only, and not by way of limitation, and that various changes in form and details may be made. Any part of the apparatus and / or method described herein may be combined in any combination, except in mutually exclusive combinations. The embodiments described herein may include various combinations and / or subcombinations of the functions, components, and / or features of the different embodiments described.

[0089] In the foregoing description, when an element is referred to as being on, connected to, electrically connected to, coupled to, or electrically coupled to another element, it will be understood that the element may be directly on, directly connected to, or directly coupled to another element, or there may be one or more intervening elements. In contrast, when an element is referred to as being directly on, directly connected to, or directly coupled to another element, there are no intervening elements. Throughout the detailed description, elements that are shown to be directly on, directly connected to, or directly coupled may be so referenced, even if the terms directly on, directly connected, or directly coupled are not used. The claims of this application may be amended to recite the exemplary relationships, if any, described in the specification or shown in the drawings.

[0090] It will be understood that the Detailed Description section, and not the Abstract section, is intended to be used to interpret the claims. The Abstract section may set forth one or more, but not all, possible embodiments of the present disclosure as contemplated by the inventor(s), and is thus not intended to limit the scope of the subject claims in any way.

Claims

1. a first plurality of Group III-nitride blue emitters emitting blue light, each blue pixel having a first area; a second plurality of Group III-nitride green emitters emitting green light, each green pixel having a second area; a third plurality of Group III-nitride red emitters emitting red light, each red pixel having a third region; The third region is at least 1.5 times larger than the first region and at least 1.5 times larger than the second region.

2. 10. The display of claim 1, wherein each III-nitride emitter includes at least one InGaN-containing quantum well.

3. 10. The display of claim 1, wherein the first plurality of emitters, the second plurality of emitters, and the third plurality of emitters are monolithically formed on a III-nitride substrate.

4. 10. The display of claim 1, wherein the red emitter is operated at a current having an associated red current density, the red emitter being characterized by a wavelength shift of at least 10 nm per decade of current density relative to the red current density.

5. 10. The display of claim 1, wherein the red emitter is operated at a current having an associated red current density, the red emitter being characterized by a relative external quantum efficiency (EQE) variation with respect to the red current density of at least 10% per decade of current density.

6. 10. The display of claim 1, wherein the red emitter is characterized by an internal quantum efficiency of at least 15% and a wavelength of at least 610 nm when the display is in operation.

7. 10. The display of claim 1, wherein the red emitter is characterized by an EQE of at least 3% and a wavelength of at least 610 nm when the display is in operation.

8. The red emitter must provide at least 0.1 Ampere / cm when the display is in operation. ２ 10. The display of claim 1, characterized by a light output current density of at least 610 nm and a wavelength of at least 610 nm.

9. The display of claim 1 , wherein the red emitters are characterized by a fill factor of at least 15%.

10. a blue emitter having a hexagonal shape and a blue emitter area; a green emitter having a hexagonal shape and a green emitter area, a first side of the green emitter being parallel to a first side of the blue emitter; 13. A device comprising: a red emitter having a hexagonal shape and a red emitter area that is larger than the blue emitter area and larger than the green emitter area, a first side and a second side of the red emitter having different lengths.

11. The device of claim 10 , wherein the first side of the red emitter is parallel to a second side of the green emitter.

12. The device of claim 10 , wherein the second side of the red emitter is parallel to a second side of the blue emitter.

13. The device of claim 12 , wherein the length of the second side of the red emitter is equal to the length of the second side of the blue emitter.

14. The device of claim 12 , wherein the second side of the red emitter is separated from the second side of the blue emitter by a gap.

15. 11. The device of claim 10, wherein an angle between adjacent sides of the red emitters, an angle between adjacent sides of the green emitters, and an angle between adjacent sides of the blue emitters is 120 degrees.

16. selecting a pixel area, red luminous flux, and red wavelength for a red indium gallium nitride (InGaN) micro-LED emitter in a pixel array of the display; determining a red emitter area and an operating current density of the red InGaN micro LED light emitter, wherein when the red InGaN micro LED emitter is operated at the operating current density, light is emitted at at least the red luminous flux having a wavelength of at least the red wavelength, and the red emitter area is between 10% and 90% of the pixel area; manufacturing a display comprising a plurality of said red InGaN micro-LED emitters.

17. The method of claim 16, wherein the red wavelength is at least 600 nm.

18. The pixel area is 5×5 μm ２ The method of claim 16, wherein the

19. The ratio of the red luminous flux to the red pixel area is at least 0.1 Amperes / cm ２ 17. The method of claim 16, wherein:

20. selecting a target pixel area, target optical crosstalk, target luminous flux, and target wavelength for red indium gallium nitride (InGaN) micro-LED emitters within a pixel array of a display; determining an optical isolation configuration, a pixel layout, and an operating current density of the red InGaN micro LED emitter; the pixel layout having an area proximate the target pixel area; when the red InGaN micro LED emitter is operated at the operating current density, light is emitted at at least the target luminous flux having a wavelength of at least the target wavelength; the optical isolation arrangement promotes optical crosstalk from the pixel to an adjacent pixel of the pixel array that is less than the target optical crosstalk; manufacturing a display comprising the optical isolation arrangement and a plurality of the red InGaN micro-LED emitters.

21. 21. A display made by the method of claim 20, comprising: a pixel array having a pixel area; a plurality of red indium gallium nitride (InGaN) micro light emitting diodes (micro LEDs) in the pixel array, the red InGaN micro LEDs having a red luminous flux, a red wavelength, and a red emitter area between 10% and 90% of the pixel area; The display is configured to operate such that the pixel array emits red light with at least the red luminous flux having a wavelength of at least the red wavelength.

22. 22. The display of claim 21, wherein the red InGaN micro-LEDs are formed on a III-nitride semiconductor substrate that includes at least one InGaN-containing quantum well.

23. Further comprising a plurality of green InGaN micro LEDs and a plurality of blue InGaN micro LEDs; 22. The display of claim 21, wherein the red InGaN micro-LEDs, the green InGaN micro-LEDs, and the blue InGaN micro-LEDs are monolithically formed on a III-nitride substrate.

24. 22. The display of claim 21, wherein the red InGaN micro-LEDs are characterized by a wavelength shift of at least 10 nm per decade of current relative to operating current density.

25. 22. The display of claim 21, wherein the red InGaN micro-LEDs are characterized by a relative external quantum efficiency (EQE) variation with operating current density of at least 10% per decade of current.

26. converting a grid of regular hexagonal light emitters having sides of equal length and equal angles between said sides into a square grid of pixels having a set of at least four pixels within a boundary having a length dimension equal to a width dimension; and transforming the square grid of pixels into a square rectilinear grid of pixels, each of the pixels from the square rectilinear grid of pixels including a first irregular hexagonal light emitter, a second irregular hexagonal light emitter, and a third irregular hexagonal light emitter, the square rectilinear grid of pixels being: a first pixel adjacent to a second pixel, the first pixel having a centroid aligned with a centroid of the second pixel along a first direction; a third pixel adjacent to the second pixel, the third pixel having a centroid aligned with the centroid of the second pixel along a second direction orthogonal to the first direction.

27. 27. The method of claim 26, wherein the regular hexagonal light emitter and the irregular hexagonal light emitter each have six sides, three centerlines bisecting opposite ones of the six sides, and an emitter center point located at an intersection of the three centerlines.

28. 28. The method of claim 27, wherein the centroid of each of the square rectilinear grid of pixels is located at a spatial average of the emitter center points of the first irregular hexagonal light emitter, the second irregular hexagonal light emitter, and the third irregular hexagonal light emitter of each of the square rectilinear grid of pixels.

29. 30. The method of claim 28, wherein the centroids of each of the square rectilinear grid of pixels do not intersect with any sides of the first irregular hexagonal light emitter, the second irregular hexagonal light emitter, or the third irregular hexagonal light emitter of each of the square rectilinear grid of pixels.

30. 27. The method of claim 26, wherein the first irregular hexagonal light emitter is a red emitter, the second irregular hexagonal light emitter is a green emitter, and the third irregular hexagonal light emitter is a blue emitter.

31. 31. The method of claim 30, further comprising adjusting relative emitter areas of the red emitter, the green emitter, and the blue emitter to form a composite color tri-color emitter.

32. 32. The method of claim 31 , wherein adjusting the relative emitter areas comprises adjusting the side lengths of the first irregular hexagonal light emitter, the second irregular hexagonal light emitter, and the third irregular hexagonal light emitter to expand or contract corresponding emitter areas.

33. 32. The method of claim 31 , wherein adjusting the relative emitter areas comprises expanding an area of ​​the red emitter and shrinking areas of the green and blue emitters.

34. 27. The method of claim 26, wherein each pixel in the square grid of pixels includes three laterally extended hexagonal emitters, each having an emitter width and an emitter height, the emitter width being greater than the emitter height.

35. 35. The method of claim 34, wherein at least two of the emitter widths in each pixel are different.

36. forming isolated pixels within said square grid of pixels; 27. The method of claim 26, further comprising: forming a separation between the separated pixels at a selected separation distance.

37. A substrate; a Group III nitride layer on the substrate; a layout of three-color pixels formed in the III-nitride layer, each three-color pixel having a pixel area and including three monochrome micro-LED emitters having different emitter areas; 14. An apparatus comprising: a metal contact disposed on a corresponding one of three monochrome micro LED emitters, the metal contact having a contact area, a ratio of the contact area to the emitter area of ​​the corresponding one of the three monochrome micro LED emitters based on a color of the corresponding one of the three monochrome micro LED emitters.

38. 40. The apparatus of claim 37, further comprising a pixel isolation region in the III-nitride layer that defines a pixel separation distance D between adjacent pixels.

39. 40. The apparatus of claim 38, wherein the pixel separation distance D is greater than an emitter separation distance d between adjacent micro LED emitters.

40. 38. The device of claim 37, wherein the metal contacts have a minimum width of 0.3 μm.

41. 40. The device of claim 37, wherein a total area occupied by the monochrome micro-LED emitters in each tri-color pixel is at least 55% of the pixel area.

42. 38. The device of claim 37, wherein the pixel pitch of the three-color pixels is 4.0 μm or less.

43. the monochrome micro LED emitter includes a red emitter; 40. The apparatus of claim 37, wherein the ratio associated with a red emitter is less than the ratio associated with other monochrome micro LED emitters.

44. 40. The apparatus of claim 37, wherein a color of a pixel of each tri-color emitter is determined by the relative emitter areas of the three monochrome micro-LED emitters.

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