TECHNICAL FIELD

Subject matter herein relates to solid state light-emitting devices, including electrically accessible light emitting diode (LED) array chips with reduced interaction between emissions of adjacent emitters, devices incorporating one or more LED array chips, and LED displays and illumination apparatuses including such devices, as well as related fabrication methods.

BACKGROUND

LEDs have been widely adopted in various illumination contexts, for backlighting of liquid crystal display (LCD) systems (e.g., as a substitute for cold cathode fluorescent lamps), and for sequentially illuminated LED displays. Applications utilizing LED arrays include automotive headlamps, roadway illumination, light fixtures, and various indoor, outdoor, and specialty contexts. Desirable characteristics of LED devices according to various end uses include high luminous efficacy, long lifetime, and wide color gamut.

Conventional color LCD display systems require color filters (e.g., red, green, and blue) that inherently reduce light utilization efficiency. Sequential illuminated LED displays, which utilize self-emitting LEDs and dispense with the need for backlights and color filters, provide enhanced light utilization efficiency.

Large format multi-color sequentially illuminated LED displays (including full color LED video screens) typically include numerous individual LED panels, packages, and/or components providing image resolution determined by the distance between adjacent pixels or “pixel pitch.” Sequentially illuminated LED displays may include “RGB” three-color displays with arrayed red, green and blue LEDs, or “RG” two-color displays with arrayed red and green LEDs. Other colors and combinations of colors may be used. Large format displays (e.g., electronic billboards and stadium displays) intended for viewing from great distances typically have relatively large pixel pitches and usually include discrete LED arrays with multi-color (e.g., red, green, and blue) LEDs that may be independently operated to form what appears to a viewer to be a full color pixel. Medium-sized displays with relatively shorter viewing distances require shorter pixel pitches (e.g., 3 mm or less), and may include panels with arrayed red, green, and blue LED components mounted on a single electronic device attached to a driver printed circuit board (PCB) that controls the LEDs.

Various LED array applications, including (but not limited to) automotive headlamps, high resolution displays suitable for short viewing distances, and other lighting devices, may benefit from smaller pixel pitches; however, practical considerations have limited their implementation. Conventional pick-and-place techniques useful for mounting LED components and packages to PCBs may be difficult to implement in a reliable manner in high-density arrays with small pixel pitches. Additionally, due to the omnidirectional character of LED and phosphor emissions, it may be difficult to prevent emissions of one LED (e.g., a first pixel) from significantly overlapping emissions of another LED (e.g., a second pixel) of an array, which would impair the effective resolution of a LED array device. It may also be difficult to avoid non-illuminated or “dark” zones between adjacent LEDs (e.g., pixels) to improve homogeneity, particularly while simultaneously reducing crosstalk or light spilling between emissions of the adjacent LEDs. Moreover, addition of various light segregation or light steering structures within a beam path of one or more LEDs may result in reduced light utilization efficiency. The art continues to seek improved LED array devices with small pixel pitches while overcoming limitations associated with conventional devices and production methods.

SUMMARY

The present disclosure relates in various aspects to solid state light emitting devices including a plurality of independently electrically accessible active layer portions that form a plurality of pixels. In certain embodiments, various enhancements may beneficially provide increased contrast (i.e., reduced cross-talk between pixels) and/or promote inter-pixel illumination homogeneity, without unduly restricting light utilization efficiency. Other technical benefits may additionally or alternatively be achieved. Certain enhancements may also promote efficient manufacturability. Exemplary enhancements providing one or more of the foregoing beneficial effects include: aligning recess portions between at least some protruding features with lateral boundaries between pixels; providing different pixels with protruding features of different sizes, shapes, numbers, and/or distributions (i.e., inter-pixel variation); providing individual pixels with protruding features of different sizes and/or shapes (i.e., intra-pixel variation); providing protruding features having lateral faces with an angle of inclination from vertical in a range of from fifteen to forty-five degrees (or another angular subrange disclosed herein); providing protruding features with a width of from about one fifth to about one half of a maximum pixel width (or a maximum active region width); providing an underfill material between pixels for light segregation and mechanical support of pixels; adjusting composition, concentration, particle size and/or distribution of lumiphoric materials among different pixels; and adjusting composition, concentration, particle size and/or distribution of scattering materials among different pixels.

In certain embodiments, an array of LEDs may be formed by growing at least one active layer on a substrate formed of a light-transmissive material, and defining a plurality of intersecting first recesses defined through an entire thickness of the at least one active layer to laterally segregate the at least one active layer into a plurality of active layer portions supported by the substrate. The substrate includes a light injection surface supporting the array of LEDs, and a light extraction surface that generally opposes the light injection surface. A plurality of intersecting second recesses that extends through the light injection surface and may extend through an entire thickness of the substrate serves to (a) define borders between light-transmissive portions of the substrate and (b) reduce crosstalk between the light-transmissive portions. Protruding features of the light extraction surface may be separated by a plurality of intersecting light extraction surface recesses.

In one aspect of the disclosure, a pixelated-LED chip comprises: an active layer comprising a plurality of active layer portions; and a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light-transmissive material, a light injection surface, and a light extraction surface, wherein the light injection surface is arranged between the active layer and the light extraction surface; wherein each active layer portion of the plurality of active layer portions is independently electrically accessible and is configured to illuminate a different substrate portion of the plurality of substrate portions and transmit light through the light extraction surface of the substrate portion, such that the plurality of active layer portions and the plurality of substrate portions form a plurality of pixels; wherein the light extraction surface of each substrate portion comprises a plurality of protruding features and a plurality of light extraction surface recesses, and each protruding feature of the plurality of protruding features is separated from at least one other protruding feature by a light extraction surface recess of the plurality of light extraction surface recesses; and wherein lateral borders between different pixels of the plurality of pixels are aligned with selected light extraction surface recesses of the plurality of light extraction surface recesses.

In certain embodiments, the lateral borders between different pixels of the plurality of pixels are aligned with selected light extraction surface recesses of the plurality of light extraction surface recesses that extend through an entire thickness of the substrate portions.

In certain embodiments, the plurality of protruding features comprises a first group of protruding features comprising a first size, and comprises a second group of protruding features comprising a second size, wherein the second size differs from the first size.

In certain embodiments, the first size and the second size comprise at least one of height, width, or length.

In certain embodiments, the plurality of protruding features comprises a first group of protruding features comprising a first shape, and comprises a second group of protruding features comprising a second shape, wherein the second shape differs from the first shape.

In certain embodiments, each protruding feature of the plurality of protruding features comprises a polyhedral or truncated polyhedral shape with a plurality of inclined lateral faces, and each inclined lateral face of the plurality of inclined lateral faces comprises an angle of inclination from vertical in a range of from about fifteen degrees to about forty-five degrees.

In certain embodiments, each protruding feature of the plurality of protruding features comprises a maximum width of from about one fifth to about one half of a maximum width of a pixel of the plurality of pixels with which each protruding feature is associated.

In certain embodiments, the plurality of substrate portions comprises a plurality of lateral edges; the plurality of protruding features comprises a first group of protruding features positioned adjacent to at least some lateral edges of the plurality of lateral edges, and comprises a second group of protruding features positioned distal from the plurality of lateral edges; and at least some protruding features of the first group of protruding features differ in at least one of (a) size, (b) shape, (c) number, or (d) distribution relative to at least some protruding features of the second group of protruding features.

In certain embodiments, the plurality of substrate portions comprises a plurality of corners; the plurality of protruding features comprises a first group of protruding features positioned adjacent to the plurality of corners, and comprises a second group of protruding features positioned distal from the plurality of corners; and at least some protruding features of the first group of protruding features differ in at least one of (a) size, (b) shape, (c) number, or (d) distribution relative to at least some protruding features of the second group of protruding features.

In certain embodiments, the pixelated-LED chip further comprises at least one lumiphoric material arranged on or over the plurality of protruding features, wherein the at least one lumiphoric material is configured to receive at least a portion of light emitted by the plurality of active layer portions and to responsively generate lumiphor emissions.

In certain embodiments, lumiphoric material associated with at least one first pixel of the plurality of pixels differs with respect to at least one of (a) composition, (b) concentration, (c) particle size, or (d) distribution relative to lumiphoric material associated with at least one second pixel of the plurality of pixels.

In certain embodiments, the plurality of substrate portions comprises silicon carbide, and the plurality of active layer portions comprises at least one Group III nitride material.

In certain embodiments, each active layer portion of the plurality of active layer portions includes a separate anode and cathode.

In another aspect of the disclosure, a pixelated-LED chip comprises: an active layer comprising a plurality of active layer portions, wherein each active layer portion of the plurality of active layer portions is independently electrically accessible to form a plurality of pixels; wherein each pixel of the plurality of pixels comprises an anode and a cathode; and an underfill material arranged between (i) lateral sidewalls of the plurality of pixels and (ii) between the anode and the cathode of each pixel of the plurality of pixels.

In certain embodiments, the underfill material comprises a light-altering or a light-reflecting material.

In certain embodiments, the light-altering or light-reflecting material comprises light-altering or light-reflecting particles suspended in a binder.

In certain embodiments, the light-altering or light-reflecting particles comprise titanium dioxide particles and the binder comprises silicone.

In certain embodiments, a weight ratio of titanium dioxide particles to silicone is in the range of 50% to 150%.

In certain embodiments, a width of the underfill material between the lateral sidewalls of the plurality of pixels is no greater than about 60 microns (μm).

In certain embodiments, the width of the underfill material between the lateral sidewalls of the plurality of pixels is in a range of from about 10 μm to about 30 μm.

In certain embodiments, the pixelated-LED chip further comprises a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light-transmissive material.

In certain embodiments, the pixelated-LED chip is devoid of an air gap between the plurality of substrate portions.

In certain embodiments, the plurality of substrate portions comprises silicon carbide.

In certain embodiments, the plurality of substrate portions comprises sapphire.

In another aspect of the disclosure, a pixelated-LED chip for automotive applications and products comprises: an active layer comprising a plurality of active layer portions, wherein each active layer portion of the plurality of active layer portions is independently electrically accessible to form a plurality of pixels; and an underfill material arranged between the plurality of active layer portions, wherein the underfill material comprises a material with a Shore D hardness scale durometer value of at least 40.

In certain embodiments, the underfill material comprises a material with a Shore D hardness scale durometer value in a range of from about 40 to about 100.

In certain embodiments, the underfill material comprises a material with a Shore D hardness scale durometer value in a range of from about 60 to about 80.

In certain embodiments, the underfill material comprises a light-altering or a light-reflecting material.

In certain embodiments, the light-altering or light-reflecting material comprises light-altering or light-reflecting particles suspended in a binder.

In certain embodiments, the light-altering or light-reflecting particles comprise titanium dioxide particles and the binder comprises silicone.

In certain embodiments, each pixel of the plurality of pixels comprises an anode and a cathode.

In certain embodiments, the underfill material is arranged between the anode and the cathode of each pixel of the plurality of pixels.

In certain embodiments, the pixelated-LED chip further comprises a lumiphoric material on the plurality of pixels.

In certain embodiments, the lumiphoric material comprises a material with a Shore D hardness scale durometer value of less than about 40.

In certain embodiments, the pixelated-LED chip further comprises a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light-transmissive material.

In certain embodiments, the plurality of substrate portions comprises silicon carbide.

In certain embodiments, the plurality of substrate portions comprises sapphire.

In another aspect of the disclosure, a pixelated-LED chip comprises: an active layer comprising a plurality of active layer portions; a substrate comprising a plurality of discontinuous substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light-transmissive material; wherein each active layer portion of the plurality of active layer portions is independently electrically accessible and is configured to illuminate a different substrate portion of the plurality of discontinuous substrate portions and transmit light through the substrate portion, such that the plurality of active layer portions and the plurality of discontinuous substrate portions form a plurality of pixels; and a first lumiphoric material on the plurality of pixels.

In certain embodiments, the first lumiphoric material comprises one or more materials including cyan, green, amber, yellow, orange, and/or red peak emission wavelengths.

In certain embodiments, the first lumiphoric material is continuous on the plurality of discontinuous substrate portions.

In certain embodiments, the first lumiphoric material comprises a plurality of light segregation elements that are registered between pixels of the plurality of pixels.

In certain embodiments, the pixelated-LED chip further comprises an underfill material between pixels of the plurality of pixels and registered with the plurality of light segregation elements.

In certain embodiments, the pixelated-LED chip further comprises a second lumiphoric material over the first lumiphoric material and the plurality of light segregation elements.

In certain embodiments, the first lumiphoric material comprises phosphor particles and scattering particles.

In certain embodiments, the scattering particles comprise at least one of fused silica, fumed silica, or titanium dioxide particles.

In another aspect of the disclosure, a pixelated-LED chip comprises: an active layer comprising a plurality of active layer portions, wherein each active layer portion of the plurality of active layer portions is independently electrically accessible to form a plurality of pixels; and a first lumiphoric material on the plurality of pixels, wherein the first lumiphoric material comprises a plurality of light segregation elements that are registered between pixels of the plurality of pixels.

In certain embodiments, the first lumiphoric material comprises one or more materials including cyan, green, amber, yellow, orange, and/or red peak emission wavelengths.

In certain embodiments, the first lumiphoric material is continuous on the plurality of pixels.

In certain embodiments, the pixelated-LED chip further comprises an underfill material between pixels of the plurality of pixels and registered with the plurality of light segregation elements.

In certain embodiments, the pixelated-LED chip further comprises a second lumiphoric material over the first lumiphoric material and the plurality of light segregation elements.

In certain embodiments, the plurality of light segregation elements comprises cuts in the first lumiphoric material.

In another aspect of the disclosure, a pixelated-LED chip comprises: an active layer comprising a plurality of active layer portions; and a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light-transmissive material, a light injection surface, and a light extraction surface, wherein the light injection surface is arranged between the active layer and the light extraction surface; wherein each active layer portion of the plurality of active layer portions is independently electrically accessible and is configured to illuminate a different substrate portion of the plurality of substrate portions and transmit light through the light extraction surface of the substrate portion, such that the plurality of active layer portions and the plurality of substrate portions form a plurality of pixels; wherein at least one substrate portion of the plurality of substrate portions comprises: a first protruding feature comprising a first angle between two opposing faces; and a second protruding feature comprising a second angle between two opposing faces, wherein the second angle is larger than the first angle.

In certain embodiments, the second angle exceeds the first angle by at least fifteen degrees.

In certain embodiments, the second angle is about ninety degrees and the first angle is about sixty degrees.

In certain embodiments, the second protruding feature is closer to a pixel sidewall than the first protruding feature.

In certain embodiments, the first protruding feature and the second protruding feature comprise silicon carbide.

In another aspect of the disclosure, a pixelated-LED chip comprises: an active layer comprising a plurality of active layer portions; and a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light-transmissive material, a light injection surface, and a light extraction surface, wherein the light injection surface is arranged between the active layer and the light extraction surface; wherein each active layer portion of the plurality of active layer portions is independently electrically accessible and is configured to illuminate a different substrate portion of the plurality of substrate portions and transmit light through the light extraction surface of the substrate portion, such that the plurality of active layer portions and the plurality of substrate portions form a plurality of pixels; wherein the light extraction surface of each substrate portion comprises a light extraction surface recess between pixel sidewalls of the plurality of pixels; and the pixelated-LED chip further comprises a reflective layer on the pixel sidewalls.

In certain embodiments, the reflective layer comprises at least one of a metal reflector, a dielectric reflector, and combinations thereof.

In another aspect of the disclosure, a pixelated-LED chip for automotive applications and products comprises: an active layer comprising a plurality of active layer portions; and a substrate comprising a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light extraction surface; wherein each active layer portion of the plurality of active layer portions is independently electrically accessible and is configured to illuminate a different substrate portion of the plurality of substrate portions and transmit light through the light extraction surface of the substrate portion, such that the plurality of active layer portions and the plurality of substrate portions form a plurality of pixels; wherein the light extraction surface of each substrate portion comprises at least one first light extraction surface recess and at least one second light extraction surface recess; and wherein the at least one second light extraction surface recess is aligned with a street between adjacent pixels of the plurality of pixels; and the pixelated-LED chip includes at least one of the following features (i) or (ii): (i) the at least one first light extraction surface recess extends deeper into the substrate than the at least one second light extraction surface recess, or (ii) the second light extraction surface recess comprises a wider bottom than the first light extraction surface recess.

In certain embodiments, the at least one first light extraction surface recess extends deeper into the substrate than the at least one second light extraction surface recess.

In certain embodiments, the second light extraction surface recess comprises a wider bottom than the first light extraction surface recess.

In another aspect of the disclosure, a method for fabricating a pixelated-LED lighting device for automotive applications and products comprises: defining a plurality of recesses or streets through an active layer on a substrate to form a plurality of active layer portions, wherein the substrate comprises (i) a light injection surface proximate to a plurality of active layer portions, and (ii) a light extraction surface generally opposing the light injection surface, wherein recesses or streets of the plurality of recesses or streets are (a) defined through the light injection surface and less than an entire thickness of the substrate and (b) arranged generally between the plurality of active layer portions, and the substrate includes a plurality of anode-cathode pairs in conductive electrical communication with the plurality of active layer portions; mounting the substrate over a mounting surface; thinning the substrate after said mounting of the substrate over the mounting surface; removing portions of the substrate through an entire thickness of the substrate along a plurality of regions registered with the plurality of recesses or streets to form a plurality of discontinuous substrate portions.

In certain embodiments, each active layer portion of the plurality of active layer portions is configured to illuminate a different light-transmissive portion of a plurality of light-transmissive portions and transmit light through the light extraction surface, such that the plurality of active layer portions and the plurality of discontinuous substrate portions form a plurality of pixels, and pixels of the plurality of pixels comprise a maximum pixel width; and the method further comprises forming a plurality of protruding features in the light extraction surface, wherein each protruding feature of the plurality of protruding features comprises a width in a range of from about one fifth to about one half of the maximum pixel width.

In certain embodiments, the method further comprises applying a first lumiphoric material to the light extraction surface.

In certain embodiments, the method further comprises removing a portion of the first lumiphoric material that is registered between pixels of the plurality of pixels to form a plurality of light segregation elements.

In certain embodiments, the method further comprises applying a second lumiphoric material over the first lumiphoric material and the plurality of light segregation elements.

In certain embodiments, the method further comprises planarizing the plurality of anode-cathode pairs prior to the mounting of the substrate over the mounting surface.

In certain embodiments, the method further comprises applying an underfill material between the substrate and the mounting surface, between the plurality of anode-cathode pairs, and between the plurality of active layer portions before the thinning of the substrate.

In another aspect of the disclosure, a method for fabricating a pixelated-LED lighting device for automotive applications and products comprises: defining a plurality of recesses or streets through an active layer on a substrate to form a plurality of active layer portions, wherein the substrate comprises (i) a light injection surface proximate to the plurality of active layer portions, and (ii) a light extraction surface generally opposing the light injection surface, wherein recesses or streets of the plurality of recesses or streets are (a) defined through the light injection surface and less than an entire thickness of the substrate and (b) arranged generally between the plurality of active layer portions, and the substrate includes a plurality of anode-cathode pairs in conductive electrical communication with the plurality of active layer portions; mounting the substrate over a mounting surface; applying an underfill material between the substrate and the mounting surface, between the plurality of anode-cathode pairs, and between the plurality of active layer portions; and thinning the substrate after applying the underfill material between the substrate and the mounting surface.

In certain embodiments, the method further comprises removing portions of the substrate along a plurality of regions, wherein some regions of the plurality of regions are registered with the plurality of recesses or streets.

In certain embodiments, the method further comprises removing portions of the substrate through an entire thickness of the substrate along the plurality of regions registered with the plurality of recesses or streets to form a plurality of discontinuous substrate portions.

In certain embodiments, the method further comprises separating the plurality of discontinuous substrate portions, the underfill material, and the plurality of anode-cathode pairs from the mounting surface.

In another aspect of the disclosure, a method for fabricating a pixelated-LED lighting device for automotive applications and products comprises: defining a plurality of recesses or streets through an active layer to form a plurality of active layer portions; depositing a plurality of anode-cathode pairs on the plurality of active layer portions to form a plurality of individually electrically accessible pixels; mounting the plurality of pixels over a mounting surface; applying a first lumiphoric material to the plurality of pixels; and removing at least a portion of the first lumiphoric material between each pixel of the plurality of pixels to form a plurality of light segregation elements.

In certain embodiments, removing at least a portion of the first lumiphoric material comprises passing a saw blade across the first lumiphoric material.

In certain embodiments, the method further comprises applying a second lumiphoric material over the first lumiphoric material and the plurality of light segregation elements.

In certain embodiments, the method further comprises applying an underfill material within the plurality of recesses or streets and between the plurality of anode-cathode pairs after mounting the plurality of pixels over the mounting surface.

In certain embodiments, the method further comprises a plurality of substrate portions supporting the plurality of active layer portions.

In certain embodiments, the method further comprises removing the plurality of substrate portions before applying the first lumiphoric material.

In certain embodiments, the method further comprises applying a second lumiphoric material over the first lumiphoric material and the plurality of light segregation elements.

In another aspect of the disclosure, a lighting device comprises at least one pixelated-LED chip, wherein the at least one pixelated-LED chip comprises: an active layer comprising a plurality of active layer portions, wherein each active layer portion of the plurality of active layer portions is independently electrically accessible to form a plurality of pixels; and an underfill material arranged between lateral sidewalls of the plurality of pixels; wherein the at least one pixelated-LED chip is configured to project at least one image onto a surface.

In certain embodiments, the underfill material comprises at least one of an insulating material, light-altering particles suspended in a binder, or light-reflecting particles suspended in a binder.

In certain embodiments, the at least one image includes at least one of alphanumeric characters, symbols, different colors, still images, and moving images such as videos.

In certain embodiments, individual pixels or subgroups of pixels of the plurality of pixels are configured to be selectively activated or deactivated to form the at least one image.

In certain embodiments, each pixel of the plurality of pixels is configured to be simultaneously activated or deactivated to provide general illumination.

In certain embodiments, the surface comprises an upright surface of a billboard or a sign.

In certain embodiments, the lighting device comprises an indoor lighting device including at least one of an area light, a downlight, a high-bay or low-bay lighting fixture, a suspended lighting fixture, a troffer, a wall-mounted or ceiling-mounted fixture, track lighting, a table or floor lamp, or a light bulb.

In certain embodiments, the lighting device comprises an outdoor lighting device including at least one of an area light, a street or roadway light fixture, a canopy light fixture, a soffit light fixture, a parking garage lighting fixture, flood lighting, and a wall-mounted or ceiling-mounted outdoor fixture.

In certain embodiments, the lighting device comprises a display backlight configured to provide localized dimming for a display screen.

In certain embodiments, the lighting device comprises a portable or hand-held lighting device including at least one of a flashlight, a personal computer, a tablet, a phone, or a watch.

In certain embodiments, any of the foregoing devices or device fabrication methods (or other devices and methods as disclosed herein) may be for non-automotive products and applications.

In certain embodiments, any of the foregoing devices or device fabrication methods (or other devices and methods as disclosed herein) may be for automotive products and applications.

In another aspect, any of the foregoing aspects, and/or various separate aspects and features as described herein, may be combined for additional advantage. Any of the various features and elements as disclosed herein may be combined with one or more other disclosed features and elements unless indicated to the contrary herein.

Other aspects, features and embodiments of the present disclosure will be more fully apparent from the ensuing disclosure and appended claims.

