Patent Publication Number: US-11646396-B2

Title: Wavelength converting layer patterning for LED arrays

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/096,010 filed Nov. 12, 2020, which is a continuation of U.S. patent application Ser. No. 16/226,616 filed Dec. 19, 2018, now U.S. Pat. No. 10,879,431, which claims benefit of priority to U.S. provisional patent application 62/609,440 filed Dec. 22, 2017 and to European Patent Application EP18164362.8 filed Mar. 27, 2018. Each of the above-mentioned applications is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Precision control lighting applications can require the production and manufacturing of light emitting diode (LED) pixel systems. Manufacturing such LED pixel systems can require accurate deposition of material due to the small size of the pixels and the small lane space between the systems. The miniaturization of components used for such LED pixel systems may lead to unintended effects that are not present in larger LED pixel systems. 
     Semiconductor light-emitting devices including LEDs, resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials. Typically, III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, composite, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions. 
     III-nitride devices are often formed as inverted or flip chip devices, where both the n- and p-contacts formed on the same side of the semiconductor structure, and most of the light is extracted from the side of the semiconductor structure opposite the contacts. 
     SUMMARY 
     A method for making a patterned wavelength converting layer includes depositing a layer comprising a photoinitiator and a curable material onto a surface and applying a nanoimprint mold on the layer of curable material to form a mesh comprising intersecting walls defining cavities. After applying the nanoimprint mold, the mesh is illuminated with light causing decarboxylation of the photoinitiator to initiate curing of the curable material. After curing the curable material, the nanoimprint mold is removed and a wavelength converting material is deposited in the cavities to form an array of wavelength converting pixels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein: 
         FIG.  1 A  is a top view diagram of a 3×3 pixel matrix; 
         FIG.  1 B  is a top view diagram of a 10×10 pixel matrix; 
         FIG.  1 C  is a diagram of a 3×3 pixel matrix on a sapphire substrate; 
         FIG.  1 D  is a cross-section view diagram of an LED array; 
         FIG.  1 E  is a cross-section view diagram of a light emitting devices; 
         FIG.  1 F  is a method to generate wavelength converting layer segments; 
         FIG.  1 G  is a diagram of a siloxane compound; 
         FIG.  1 H  is a diagram of a nanoimprint lithography mold on converter material; 
         FIG.  1 I  is a diagram of an intermediate step of the nanoimprint lithography mold on converter material of  FIG.  1 H ; 
         FIG.  1 J  is a diagram of a top view of a mesh; 
         FIG.  1 K  is a cross section view of the mesh of  FIG.  1 J ; 
         FIG.  2 A  is a top view of the electronics board with LED array attached to the substrate at the LED device attach region in one embodiment; 
         FIG.  2 B  is a diagram of one embodiment of a two channel integrated LED lighting system with electronic components mounted on two surfaces of a circuit board; 
         FIG.  2 C  is an example vehicle headlamp system; and 
         FIG.  3    shows an example illumination system. 
     
    
    
     DETAILED DESCRIPTION 
     Examples of different light illumination systems and/or light emitting diode (“LED”) implementations will be described more fully hereinafter with reference to the accompanying drawings. These examples are not mutually exclusive, and features found in one example may be combined with features found in one or more other examples to achieve additional implementations. Accordingly, it will be understood that the examples shown in the accompanying drawings are provided for illustrative purposes only and they are not intended to limit the disclosure in any way. Like numbers refer to like elements throughout. 
     It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms may be used to distinguish one element from another. For example, a first element may be termed a second element and a second element may be termed a first element without departing from the scope of the present invention. As used herein, the term “and/or” may include any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it may be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there may be no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element and/or connected or coupled to the other element via one or more intervening elements. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present between the element and the other element. It will be understood that these terms are intended to encompass different orientations of the element in addition to any orientation depicted in the figures. 
     Relative terms such as “below,” “above,” “upper,”, “lower,” “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures. 
     Semiconductor light emitting devices (LEDs) or optical power emitting devices, such as devices that emit ultraviolet (UV) or infrared (IR) optical power, are among the most efficient light sources currently available. These devices (hereinafter “LEDs”), may include light emitting diodes, resonant cavity light emitting diodes, vertical cavity laser diodes, edge emitting lasers, or the like. Due to their compact size and lower power requirements, for example, LEDs may be attractive candidates for many different applications. For example, they may be used as light sources (e.g., flash lights and camera flashes) for hand-held battery-powered devices, such as cameras and cell phones. They may also be used, for example, for automotive lighting, heads up display (HUD) lighting, horticultural lighting, street lighting, torch for video, general illumination (e.g., home, shop, office and studio lighting, theater/stage lighting and architectural lighting), augmented reality (AR) lighting, virtual reality (VR) lighting, as back lights for displays, and IR spectroscopy. A single LED may provide light that is less bright than an incandescent light source, and, therefore, multi-junction devices or arrays of LEDs (such as monolithic LED arrays, micro LED arrays, etc.) may be used for applications where more brightness is desired or required. 
     According to embodiments of the disclosed subject matter, LED arrays (e.g., micro LED arrays) may include an array of pixels as shown in  FIGS.  1 A,  1 B , and/or  1 C. LED arrays may be used for any applications such as those requiring precision control of LED array segments. Pixels in an LED array may be individually addressable, may be addressable in groups/subsets, or may not be addressable. In  FIG.  1 A , a top view of a LED array  110  with pixels  111  is shown. An exploded view of a 3×3 portion of the LED array  110  is also shown in  FIG.  1 A . As shown in the 3×3 portion exploded view, LED array  110  may include pixels  111  with a width w 1  of approximately 100 μm or less (e.g., 40 μm). The lanes  113  between the pixels may be separated by a width, w 2 , of approximately 20 μm or less (e.g., 5 μm). The lanes  113  may provide an air gap between pixels or may contain other material, as shown in  FIGS.  1 B and  1 C  and further disclosed herein. The distance d 1  from the center of one pixel  111  to the center of an adjacent pixel  111  may be approximately 120 μm or less (e.g., 45 μm). It will be understood that the widths and distances provided herein are examples only, and that actual widths and/or dimensions may vary. 
     It will be understood that although rectangular pixels arranged in a symmetric matrix are shown in  FIGS.  1 A , B and C, pixels of any shape and arrangement may be applied to the embodiments disclosed herein. For example, LED array  110  of  FIG.  1 A  may include, over 10,000 pixels in any applicable arrangement such as a 100×100 matrix, a 1200×50 matrix, a symmetric matrix, a non-symmetric matrix, or the like. It will also be understood that multiple sets of pixels, matrixes, and/or boards may be arranged in any applicable format to implement the embodiments disclosed herein. 
       FIG.  1 B  shows a cross section view of an example LED array  1000 . As shown, the pixels  1010 ,  1020 , and  1030  correspond to three different pixels within an LED array such that a separation sections  1041  and/or n-type contacts  1040  separate the pixels from each other. According to an embodiment, the space between pixels may be occupied by an air gap. As shown, pixel  1010  includes an epitaxial layer  1011  which may be grown on any applicable substrate such as, for example, a sapphire substrate, which may be removed from the epitaxial layer  1011 . A surface of the growth layer distal from contact  1015  may be substantially planar or may be patterned. A p-type region  1012  may be located in proximity to a p-contact  1017 . An active region  1021  may be disposed adjacent to the n-type region and a p-type region  1012 . Alternatively, the active region  1021  may be between a semiconductor layer or n-type region and p-type region  1012  and may receive a current such that the active region  1021  emits light beams. The p-contact  1017  may be in contact with SiO2 layers  1013  and  1014  as well as plated metal layer  1016  (e.g., plated copper). The n type contacts  1040  may include an applicable metal such as Cu. The metal layer  1016  may be in contact with a contact  1015  which may be reflective. 
     Notably, as shown in  FIG.  1 B , the n-type contact  1040  may be deposited into trenches  1130  created between pixels  1010 ,  1020 , and  1030  and may extend beyond the epitaxial layer. Separation sections  1041  may separate all (as shown) or part of a wavelength converting layer  1050 . It will be understood that a LED array may be implemented without such separation sections  1041  or the separation sections  1041  may correspond to an air gap. The separation sections  1041  may be an extension of the n-type contacts  1040 , such that, separation sections  1041  are formed from the same material as the n-type contacts  1040  (e.g., copper). Alternatively, the separation sections  1041  may be formed from a material different than the n-type contacts  1040 . According to an embodiment, separation sections  1041  may include reflective material. The material in separation sections  1041  and/or the n-type contact  1040  may be deposited in any applicable manner such as, for example, but applying a mesh structure which includes or allows the deposition of the n-type contact  1040  and/or separation sections  1041 . Wavelength converting layer  1050  may have features/properties similar to wavelength converting layer  205  of  FIG.  1 D . As noted herein, one or more additional layers may coat the separation sections  1041 . Such a layer may be a reflective layer, a scattering layer, an absorptive layer, or any other applicable layer. One or more passivation layers  1019  may fully or partially separate the n-contact  1040  from the epitaxial layer  1011 . 
     The epitaxial layer  1011  may be formed from any applicable material to emit photons when excited including sapphire, SiC, GaN, Silicone and may more specifically be formed from a III-V semiconductors including, but not limited to, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, II-VI semiconductors including, but not limited to, ZnS, ZnSe, CdSe, CdTe, group IV semiconductors including, but not limited to Ge, Si, SiC, and mixtures or alloys thereof. These example semiconductors may have indices of refraction ranging from about 2.4 to about 4.1 at the typical emission wavelengths of LEDs in which they are present. For example, III-Nitride semiconductors, such as GaN, may have refractive indices of about 2.4 at 500 nm, and III-Phosphide semiconductors, such as InGaP, may have refractive indices of about 3.7 at 600 nm. Contacts coupled to the LED device  1200  may be formed from a solder, such as AuSn, AuGa, AuSi or SAC solders. 
     The n-type region may be grown on a growth substrate and may include one or more layers of semiconductor material that include different compositions and dopant concentrations including, for example, preparation layers, such as buffer or nucleation layers, and/or layers designed to facilitate removal of the growth substrate. These layers may be n-type or not intentionally doped, or may even be p-type device layers. The layers may be designed for particular optical, material, or electrical properties desirable for the light emitting region to efficiently emit light. Similarly, the p-type region  1012  may include multiple layers of different composition, thickness, and dopant concentrations, including layers that are not intentionally doped, or n-type layers. An electrical current may be caused to flow through the p-n junction (e.g., via contacts) and the pixels may generate light of a first wavelength determined at least in part by the bandgap energy of the materials. A pixel may directly emit light (e.g., regular or direct emission LED) or may emit light into a wavelength converting layer  1050  (e.g., phosphor converted LED, “PCLED”, etc.) that acts to further modify wavelength of the emitted light to output a light of a second wavelength. 
     Although  FIG.  1 B  shows an example LED array  1000  with pixels  1010 ,  1020 , and  1030  in an example arrangement, it will be understood that pixels in an LED array may be provided in any one of a number of arrangements. For example, the pixels may be in a flip chip structure, a vertical injection thin film (VTF) structure, a multi junction structure, a thin film flip chip (TFFC), lateral devices, etc. For example, a lateral LED pixel may be similar to a flip chip LED pixel but may not be flipped upside down for direct connection of the electrodes to a substrate or package. A TFFC may also be similar to a flip chip LED pixel but may have the growth substrate removed (leaving the thin film semiconductor layers un-supported). In contrast, the growth substrate or other substrate may be included as part of a flip chip LED. 
     The wavelength converting layer  1050  may be in the path of light emitted by active region  1021 , such that the light emitted by active region  1021  may traverse through one or more intermediate layers (e.g., a photonic layer). According to embodiments, wavelength converting layer  1050  or may not be present in LED array  1000 . The wavelength converting layer  1050  may include any luminescent material, such as, for example, phosphor particles in a transparent or translucent binder or matrix, or a ceramic phosphor element, which absorbs light of one wavelength and emits light of a different wavelength. The thickness of a wavelength converting layer  1050  may be determined based on the material used or application/wavelength for which the LED array  1000  or individual pixels  1010 ,  1020 , and  1030  is/are arranged. For example, a wavelength converting layer  1050  may be approximately 20 μm, 50 μm or 1200 μm. The wavelength converting layer  1050  may be provided on each individual pixel, as shown, or may be placed over an entire LED array  1000 . 
     Primary optic  1022  may be on or over one or more pixels  1010 ,  1020 , and/or  1030  and may allow light to pass from the active region  101  and/or the wavelength converting layer  1050  through the primary optic. Light via the primary optic may generally be emitted based on a Lambertian distribution pattern such that the luminous intensity of the light emitted via the primary optic  1022 , when observed from an ideal diffuse radiator, is directly proportional to the cosine of the angle between the direction of the incident light and the surface normal. It will be understood that one or more properties of the primary optic  1022  may be modified to produce a light distribution pattern that is different than the Lambertian distribution pattern. 
     Secondary optics which include one or both of the lens  1065  and waveguide  1062  may be provided with pixels  1010 ,  1020 , and/or  1030 . It will be understood that although secondary optics are discussed in accordance with the example shown in  FIG.  1 B  with multiple pixels, secondary optics may be provided for single pixels. Secondary optics may be used to spread the incoming light (diverging optics), or to gather incoming light into a collimated beam (collimating optics). The waveguide  1062  may be coated with a dielectric material, a metallization layer, or the like and may be provided to reflect or redirect incident light. In alternative embodiments, a lighting system may not include one or more of the following: the wavelength converting layer  1050 , the primary optics  1022 , the waveguide  1062  and the lens  1065 . 
     Lens  1065  may be formed form any applicable transparent material such as, but not limited to SiC, aluminum oxide, diamond, or the like or a combination thereof. Lens  1065  may be used to modify the a beam of light to be input into the lens  1065  such that an output beam from the lens  1065  will efficiently meet a desired photometric specification. Additionally, lens  1065  may serve one or more aesthetic purpose, such as by determining a lit and/or unlit appearance of the multiple LED devices  1200 B. 
       FIG.  1 C  shows a cross section of a three dimensional view of a LED array  1100 . As shown, pixels in the LED array  1100  may be separated by trenches which are filled to form n-contacts  1140 . The pixels may be grown on a substrate  1114  and may include a p-contact  1113 , a p-GaN semiconductor layer  1112 , an active region  1111 , and an n-Gan semiconductor layer  1110 . It will be understood that this structure is provided as an example only and one or more semiconductor or other applicable layers may be added, removed, or partially added or removed to implement the disclosure provided herein. A wavelength converting layer  1117  may be deposited on the semiconductor layer  1110  (or other applicable layer). 
     Passivation layers  1115  may be formed within the trenches  1130  and n-contacts  1140  (e.g., copper contacts) may be deposited within the trenches  1130 , as shown. The passivation layers  1115  may separate at least a portion of the n-contacts  1140  from one or more layers of the semiconductor. According to an implementation, the n-contacts  1140 , or other applicable material, within the trenches may extend into the wavelength converting layer  1117  such that the n-contacts  1140 , or other applicable material, provide complete or partial optical isolation between the pixels. 
       FIG.  1 D  shows an example pixel array  1200  manufactured in accordance with the techniques disclosed herein may include light-emitting devices  1270  that include a GaN layer  1250 , active region  1290 , solder  1280 , and pattern sapphire substrate (PSS) pattern  1260 . Wavelength converting layers  1220  may be disposed onto the light emitting devices  1270  in accordance with the techniques disclosed herein to create pixels  1275 . 
     Optical isolation materials  1230  may be applied to the wavelength converting layer  1220 . A wavelength converting layer may be mounted onto a GaN layer  1250  via a pattern sapphire substrate (PSS) pattern  1260 . The GaN layer  1250  may be bonded to or grown over an active region  1290  and the light-emitting device  1270  may include a solder  1280 . Optical isolator material  1240  may also be applied to the sidewalls of the GaN layer  1250 . 
     As an example, the pixels  1275  of  FIG.  1 D  may correspond to the pixels  111  of  FIG.  1   b   . When the pixels  111  or  1275  are activated, the respective active regions  1290  of the pixels may generate a light. The light may pass through the wavelength converting layer  1220  and may substantially be emitted from the surface of the wavelength converting layer  1220 . 
       FIG.  1 E  shows components of the pixel array of  FIG.  1 D  prior to the wavelength converting layer  1220  being placed on the light emitting devices  1270 . 
       FIG.  1 F  shows a method  1400  for generating a wavelength converting layer with a sol-gel or siloxane binder. As shown at step  1410  a wavelength converting layer may be deposited onto a surface. The surface may be any applicable surface such as a support surface such as a glass support surface, a tape such as a stretchable tape, a blue tape, a white tape, a UV tape, or any other surface configured to hold the wavelength converting layer. The surface may contain walls to hold the wavelength converting layer material. 
     The wavelength converting layer may include a plurality of optically isolating particles such as, but not limited to phosphor grains with or without activation from rare earth ions, zinc barium borate, aluminum nitride, aluminum oxynitride (AlON), barium sulfate, barium titanate, calcium titanate, cubic zirconia, diamond, gadolinium gallium garnet (GGG), lead lanthanum zirconate titanate (PLZT), lead zirconate titanate (PZT), sapphire, silicon aluminum oxynitride (SiAlON), silicon carbide, silicon oxynitride (SiON), strontium titanate, titanium oxide, yttrium aluminum garnet (YAG), zinc selenide, zinc sulfide, and zinc telluride, diamond, silicon carbide (SiC), single crystal aluminum nitride (AlN), gallium nitride (GaN), or aluminum gallium nitride (AlGaN) or any transparent, translucent, or scattering ceramic, optical glass, high index glass, sapphire, alumina, III-V semiconductors such as gallium phosphide, II-VI semiconductors such as zinc sulfide, zinc selenide, and zinc telluride, group IV semiconductors and compounds, metal oxides, metal fluorides, an oxide of any of the following: aluminum, antimony, arsenic, bismuth, calcium, copper, gallium, germanium, lanthanum, lead, niobium, phosphorus, tellurium, thallium, titanium, tungsten, zinc, or zirconium, polycrystalline aluminum oxide (transparent alumina), aluminum oxynitride (AlON), cubic zirconia (CZ), gadolinium gallium garnet (GGG), gallium phosphide (GaP), lead zirconate titanate (PZT), silicon aluminum oxynitride (SiAlON), silicon carbide (SiC), silicon oxynitride (SiON), strontium titanate, yttrium aluminum garnet (YAG), zinc sulfide (ZnS), spinel, Schott glass LaFN21, LaSFN35, LaF2, LaF3, LaF10, NZK7, NLAF21, LaSFN18, SF59, or LaSF3, Ohara glass SLAM60 or SLAH51, and may comprise nitride luminescent material, garnet luminescent material, orthosilicate luminescent material, SiAlON luminescent material, aluminate luminescent material, oxynitride luminescent material, halogenide luminescent material, oxyhalogenide luminescent material, sulfide luminescent material and/or oxysulfide luminescent material, luminescent quantum dots comprising core materials chosen from cadmium sulfide, cadmium selenide, zinc sulfide, zinc selenide, and may be chosen form SrLiAl 3 N 4 :Eu (II) (strontium-lithium-aluminum nitride: europium (II)) class, Eu(II) doped nitride phosphors like (Ba,Sr,Ca)2Si5-xAlxOxN8:Eu, (Sr,Ca)SiAlN3:Eu or SrLiAl3N4:Eu, or any combination thereof. 
     The wavelength converting layer may include binder material such that the binder material is either siloxane material or sol-gel material or hybrid combinations of sol-gel and siloxane, as well as polysilazane precursor polymers in combination with siloxanes. Siloxane material and/or sol-gel material may be as a binder as such material may be configured to remain functional under the high flux and temperature requirements of LED pixels and pixel arrays. 
     Siloxane material may be siloxane polymer where siloxane is a functional group in organosilicon chemistry with the Si—O—Si linkage, as shown in  FIG.  1 G  via compound  1500 . Parent siloxanes may include oligomeric and polymeric hydrides with the formulae H(OSiH 2 ) n OH and (OSiH 2 ) n . Siloxanes may also include branched compounds, the defining feature of which may be that each pair of silicon centres is separated by one oxygen atom. Siloxane material may adopt structures expected for linked tetrahedral (“sp 3 -like”) centers. The Si—O bond may be 1.64 Å (vs Si—C distance of 1.92 Å) and the Si—O—Si angle may be open at 142.5°. Siloxanes may have low barriers for rotation about the Si—O bonds as a consequence of low steric hindrance. 
     A siloxane binder may be formed via a condensation reaction such that molecules join together by losing small molecules as byproducts such as water or methanol. Alternatively or in addition, a siloxane binder may be formed via ring-opening polymerization such that the terminal end of a polymer chain acts as a reactive center where further cyclic monomers can react by opening its ring system and form a longer polymer chain. The condensation reaction and/or the ring-opening polymerization may be considered a form of chain-growth polymerization. 
     A sol-gel binder may be created via a sol-gel process using a wet-chemical technique. In such a process a solution may evolve gradually towards the formation of a gel-like network containing both a liquid and a solid phase. Precursors such as metal alkoxides and metal chlorides, which undergo hydrolysis and polycondensation reactions, may be used during the sol-gel process. The solution (sol) may contain colloids and a colloidal dispersion may be a solid-liquid and/or liquid/liquid mixture, which contains solid particles, dispersed in various degrees in a liquid medium. A sol-gel binder may be formed via a condensation reaction such that molecules join together by losing small molecules as byproducts such as water or methanol. Precursor polymers such as polysilazanes and polysilazane-siloxane hybrid materials may also be used as binders. Polysilzanes are precursor polymers containing the —HN—Si motif which is highly reactive with silanols (Si—OH) and alcohols (C—OH) to form siloxane bonds (Si—O—) with elimination of ammonia (NH3). Polysilazane-based precursor liquids are commercially available as “Spin-On-Glass” materials. They are typically used to cast SiO2 dielectric films. 
     The binder to bind a wavelength converting layer may need to experience rapid curing and low volatility in order facilitate a nanoimprint lithography (NIL) process as disclosed herein. Accordingly, the wavelength converting layer may contain a photoinitiator, and the photoinitiator may be used to catalyze the curing process of the binder. A NIL process may be applied to the wavelength converting layer to segment the wavelength converting layer into wavelength converting layer segments that can be applied to light emitting devices. As shown in  FIG.  1 F , at step  1420 , a NIL mold may be applied to the wavelength converting layer.  FIG.  1 H  illustrates a cross-sectional view of a NIL mold  1610  being applied to a wavelength converting layer  1620 . As shown, the NIL mold  1610  may be deposited such that wavelength converting layer  1620  changes its form to that of the mold  1610 . It should be noted that the space between the teeth of the mold  1610  may correspond to the spacing required to place wavelength converting layer segments onto spaced light emitting devices. 
     At step  1430  of  FIG.  1 F , the wavelength converting layer may be cured. The curing may be conducted using a UV radiation or a combination of UV radiation and a thermal cure. All or portions of the wavelength converting layer may be exposed to UV radiation such that those sections can be cured. UV light may be emitted onto the wavelength converting layer from any applicable direction and may be applied through the NIL mold if the mold is fully or partially transparent. 
     The UV light may produce a rapid curing process via the use of a catalyst to expedite the reactions required to complete the cure. The UV light may emit onto a photoinitiator contained in the wavelength converting layer and the photoinitiator may react with the UV light. The photoinitiator may be, for example, a salt created by interactions of bases with an acid that is capable of undergoing photodecarboxylation. The photoinitiator may be a salt compound created when an acid and a base pair up to form a neutral species. 
     The photoinitiator may be configured to undergo the photodecarboxylation process when UV light is emitted onto the photoinitiator. A compound contained in the photoinitiator, such as an organic acid, may react with the light such that it decomposes by losing carbon dioxide (CO2). Such decarboxylation may effectively remove the acid from the photoinitiator and a byproduct of the decarboxylation may be, for example, a super base along with other non-acidic residues. The super base may be, for example, 1,5-diazabicyclo [5.4.0] undec-5-ene (DBU), 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD). The super base may have properties such that it seeks other molecules to park excess electrons which may lead to catalytic action on reactive chain ends or crosslinkable substrates of the sol-gel or siloxane binder. 
     The super base or other non-acidic residues may be removed from the wavelength converting layer by evaporation or further decomposition during a thermal cure or postbake. 
     As shown at step  1440  of  FIG.  1 F , the nanoimprint mold may be removed from the wavelength converting layer as the wavelength converting layer may contain wavelength converting layer segments that are shaped during the curing process. At step  1450  of  FIG.  1 F  wavelength converting layer segments may be sized and placed such that they can be attached to an array of light emitting devices such as the array of light emitting devices  1201  of  FIG.  1 E  to produce the pixel array  1200  of  FIG.  1 D . It will be noted that a separation step may be required to separate the wavelength converting layer to form the wavelength converting layer segments and may include any applicable such as sawing, etching, laser etching, or the like. It will also be noted that the wavelength converting layer segments may be attached to light emitting devices via any applicable transfer method such as by using a transfer tape, transfer substrate, or the like. 
       FIG.  1 I  shows an intermediate step of the cross-sectional view of a NIL mold  1610  being applied to a wavelength converting layer  1620 , of  FIG.  1 I . As shown, the wavelength converting layer  1620  may be partially formed such that wavelength converting layer  1620  corresponds to the portion that is cured with, for example, via UV light such that the photoinitiator experiences decarboxylation. A second wavelength converting layer  1630  may be partially formed such that it may be experiencing decarboxylation. A byproduct of super base  1631  may remain at this intermediate step, as shown. 
     According to an implementation of the disclosed subject matter, direct printing using ink jet or similar printing machines may be used to deposit a wavelength converting layer onto light emitting devices. A pattern may be generated on a releasable substrate such as a photolith or imprint litho. Atomic layer deposition (ALD) may be used to pattern a layer using, for example, liftoff to remove the undesirable areas. Kateeva or similar printers can be used to print each layer with, for example, a TiOx layer at the below a phosphor layer. Notably, such direct printing may require the phosphor particles to be significantly smaller than space made available via the nozzles. Accordingly, 1 um or less phosphor particle size may be used for such a deposition. 
     According to an implementation of the disclosed subject matter,  FIG.  1 J  shows a top view and  FIG.  1 K  shows a cross-sectional view of a mesh wall  1715  that may be generated to provide a structure for a wavelength converting layers  1220  of  FIG.  1 D  when manufacturing the pixel array of  FIG.  1 D . The mesh wall  1715  may contain cavities  1714  with space that correspond to the space between light emitting devices  1270  of  FIG.  1 E  such that the mesh wall is spaced for the cavities  1714  to align with the light emitting devices  1270  of  FIG.  1 E  prior to the attaching the wavelength converting layers  1220  of  FIG.  1 D . The mesh walls may be formed using a nanoimprint (NIL) lithography process or a contact print process. A NIL process may be used to generate the mesh walls by depositing a mesh wall material onto a surface and applying a nanoimprint mold onto the material. The mesh wall material may be cured using thermal curing or using UV light and the nanoimprint mold may be removed from the mesh wall material. The resulting mesh wall may be deposited onto the pixel array to create supports for the deposition of a wavelength converting layers  1220  of  FIG.  1 D . Alternatively, the mesh film may be generated contact printing photonic columns with, for example, sacrificial PMMA or with UV curable material. 
       FIG.  2 A  is a top view of an electronics board with an LED array  410  attached to a substrate at the LED device attach region  318  in one embodiment. The electronics board together with the LED array  410  represents an LED system  400 A. Additionally, the power module  312  receives a voltage input at Vin  497  and control signals from the connectivity and control module  316  over traces  418 B, and provides drive signals to the LED array  410  over traces  418 A. The LED array  410  is turned on and off via the drive signals from the power module  312 . In the embodiment shown in  FIG.  2 A , the connectivity and control module  316  receives sensor signals from the sensor module  314  over trace  418 C. The pixels in LED array  410  may be generated in accordance with the steps outlined in  FIG.  1 F  and may be based on the techniques disclosed herein related to  FIGS.  1 G-I . 
       FIG.  2 B  illustrates one embodiment of a two channel integrated LED lighting system with electronic components mounted on two surfaces of a circuit board  499 . As shown in  FIG.  2 B , an LED lighting system  400 B includes a first surface  445 A having inputs to receive dimmer signals and AC power signals and an AC/DC converter circuit  412  mounted on it. The LED system  400 B includes a second surface  445 B with the dimmer interface circuit  415 , DC-DC converter circuits  440 A and  440 B, a connectivity and control module  416  (a wireless module in this example) having a microcontroller  472 , and an LED array  410  mounted on it. The LED array  410  is driven by two independent channels such as first channel  411 A and second channel  411 B. In alternative embodiments, a single channel may be used to provide the drive signals to an LED array, or any number of multiple channels may be used to provide the drive signals to an LED array. 
     The LED array  410  may include two groups of LED devices. In an example embodiment, the LED devices of group A are electrically coupled to a first channel  411 A and the LED devices of group B are electrically coupled to a second channel  411 B. Each of the two DC-DC converters  440 A and  440 B may provide a respective drive current via single channels  411 A and  411 B, respectively, for driving a respective group of LEDs A and B in the LED array  410 . The LEDs in one of the groups of LEDs may be configured to emit light having a different color point than the LEDs in the second group of LEDs. Control of the composite color point of light emitted by the LED array  410  may be tuned within a range by controlling the current and/or duty cycle applied by the individual DC/DC converter circuits  440 A and  440 B via a single channel  411 A and  411 B, respectively. Although the embodiment shown in  FIG.  2 B  does not include a sensor module (as described in  FIG.  2 A ), an alternative embodiment may include a sensor module. 
     The illustrated LED lighting system  400 B is an integrated system in which the LED array  410  and the circuitry for operating the LED array  410  are provided on a single electronics board. Connections between modules on the same surface of the circuit board  499  may be electrically coupled for exchanging, for example, voltages, currents, and control signals between modules, by surface or sub-surface interconnections, such as traces  431 ,  432 ,  433 ,  434  and  435  or metallizations (not shown). Connections between modules on opposite surfaces of the circuit board  499  may be electrically coupled by through board interconnections, such as vias and metallizations (not shown). As disclosed herein, the pixels in LED array  410  may be generated in accordance with the steps outlined in  FIG.  1 F  and may be based on the techniques disclosed herein related to  FIGS.  1 G-I . 
     According to embodiments, LED systems may be provided where an LED array is on a separate electronics board from the driver and control circuitry. According to other embodiments, a LED system may have the LED array together with some of the electronics on an electronics board separate from the driver circuit. For example, an LED system may include a power conversion module and an LED module located on a separate electronics board than the LED arrays. 
     According to embodiments, an LED system may include a multi-channel LED driver circuit. For example, an LED module may include embedded LED calibration and setting data and, for example, three groups of LEDs. One of ordinary skill in the art will recognize that any number of groups of LEDs may be used consistent with one or more applications. Individual LEDs within each group may be arranged in series or in parallel and the light having different color points may be provided. For example, warm white light may be provided by a first group of LEDs, a cool white light may be provided by a second group of LEDs, and a neutral white light may be provided by a third group. 
       FIG.  2 C  shows an example vehicle headlamp system  300  including a vehicle power  302  including a data bus  304 . A sensor module  307  may be connected to the data bus  304  to provide data related to environment conditions (e.g. ambient light conditions, temperature, time, rain, fog, etc.), vehicle condition (parked, in-motion, speed, direction), presence/position of other vehicles, pedestrians, objects, or the like. The sensor module  307  may be similar to or the same as the sensor module  314  of  FIG.  2 A . AC/DC Converter  305  may be connected to the vehicle power  302 . 
     The power module  312  (AC/DC converter) of  FIG.  2 C  may be the same as or similar to the AC/DC converter  412  of  FIG.  2 B  and may receive AC power from the vehicle power  302 . It may convert the AC power to DC power as described in  FIG.  2 B  for AC-DC converter  412 . The vehicle head lamp system  300  may include an active head lamp  331  which receives one or more inputs provided by or based on the AC/DC converter  305 , connectivity and control module  306 , and/or sensor module  307 . As an example, the sensor module  307  may detect the presence of a pedestrian such that the pedestrian is not well lit, which may reduce the likelihood that a driver sees the pedestrian. Based on such sensor input, the connectivity and control module  306  may output data to the active head lamp  331  using power provided from the AC/DC converter  305  such that the output data activates a subset of LEDs in an LED array contained within active head lamp  331 . The subset of LEDs in the LED array, when activated, may emit light in the direction where the sensor module  307  sensed the presence of the pedestrian. These subset of LEDs may be deactivated or their light beam direction may otherwise be modified after the sensor module  207  provides updated data confirming that the pedestrian is no longer in a path of the vehicle that includes vehicle head lamp system. The pixels in an LED array in the active head lamp  331  may be generated in accordance with the steps outlined in  FIG.  1 F  and may be based on the techniques disclosed herein related to  FIGS.  1 G-I . 
       FIG.  3    shows an example system  550  which includes an application platform  560 , LED systems  552  and  556 , and optics  554  and  558 . The pixels in LED systems  552  and  556  may be generated in accordance with the steps outlined in  FIG.  1 F  and may be based on the techniques disclosed herein related to  FIGS.  1 G-I . The LED System  552  produces light beams  561  shown between arrows  561   a  and  561   b . The LED System  556  may produce light beams  562  between arrows  562   a  and  562   b . In the embodiment shown in  FIG.  3   , the light emitted from LED System  552  passes through secondary optics  554 , and the light emitted from the LED System  556  passes through secondary optics  558 . In alternative embodiments, the light beams  561  and  562  do not pass through any secondary optics. The secondary optics may be or may include one or more light guides. The one or more light guides may be edge lit or may have an interior opening that defines an interior edge of the light guide. LED systems  552  and/or  556  may be inserted in the interior openings of the one or more light guides such that they inject light into the interior edge (interior opening light guide) or exterior edge (edge lit light guide) of the one or more light guides. LEDs in LED systems  552  and/or  556  may be arranged around the circumference of a base that is part of the light guide. According to an implementation, the base may be thermally conductive. According to an implementation, the base may be coupled to a heat-dissipating element that is disposed over the light guide. The heat-dissipating element may be arranged to receive heat generated by the LEDs via the thermally conductive base and dissipate the received heat. The one or more light guides may allow light emitted by LED systems  552  and  556  to be shaped in a desired manner such as, for example, with a gradient, a chamfered distribution, a narrow distribution, a wide distribution, an angular distribution, or the like. 
     In example embodiments, the system  550  may be a mobile phone of a camera flash system, indoor residential or commercial lighting, outdoor light such as street lighting, an automobile, a medical device, AR/VR devices, and robotic devices. The LED System  400 A shown in  FIG.  2 A  and vehicle head lamp system  300  shown in  FIG.  2 C  illustrate LED systems  552  and  556  in example embodiments. 
     The application platform  560  may provide power to the LED systems  552  and/or  556  via a power bus via line  565  or other applicable input, as discussed herein. Further, application platform  560  may provide input signals via line  565  for the operation of the LED system  552  and LED system  556 , which input may be based on a user input/preference, a sensed reading, a pre-programmed or autonomously determined output, or the like. One or more sensors may be internal or external to the housing of the application platform  560 . Alternatively or in addition, as shown in the LED system  400  of  FIG.  2 A , each LED System  552  and  556  may include its own sensor module, connectivity and control module, power module, and/or LED devices. 
     In embodiments, application platform  560  sensors and/or LED system  552  and/or  556  sensors may collect data such as visual data (e.g., LIDAR data, IR data, data collected via a camera, etc.), audio data, distance based data, movement data, environmental data, or the like or a combination thereof. The data may be related a physical item or entity such as an object, an individual, a vehicle, etc. For example, sensing equipment may collect object proximity data for an ADAS/AV based application, which may prioritize the detection and subsequent action based on the detection of a physical item or entity. The data may be collected based on emitting an optical signal by, for example, LED system  552  and/or  556 , such as an IR signal and collecting data based on the emitted optical signal. The data may be collected by a different component than the component that emits the optical signal for the data collection. Continuing the example, sensing equipment may be located on an automobile and may emit a beam using a vertical-cavity surface-emitting laser (VCSEL). The one or more sensors may sense a response to the emitted beam or any other applicable input. 
     In example embodiment, application platform  560  may represent an automobile and LED system  552  and LED system  556  may represent automobile headlights. In various embodiments, the system  550  may represent an automobile with steerable light beams where LEDs may be selectively activated to provide steerable light. For example, an array of LEDs may be used to define or project a shape or pattern or illuminate only selected sections of a roadway. In an example embodiment, Infrared cameras or detector pixels within LED systems  552  and/or  556  may be sensors (e.g., similar to sensors module  314  of  FIG.  2 A and  307    of  FIG.  2 C ) that identify portions of a scene (roadway, pedestrian crossing, etc.) that require illumination. 
     Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs).