WO2020128626A1 - Extraction de lumière améliorée au moyen d'une couche adhésive entre une del et un convertisseur - Google Patents

Extraction de lumière améliorée au moyen d'une couche adhésive entre une del et un convertisseur Download PDF

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Publication number
WO2020128626A1
WO2020128626A1 PCT/IB2019/001370 IB2019001370W WO2020128626A1 WO 2020128626 A1 WO2020128626 A1 WO 2020128626A1 IB 2019001370 W IB2019001370 W IB 2019001370W WO 2020128626 A1 WO2020128626 A1 WO 2020128626A1
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Prior art keywords
substrate
light emitting
adhesive layer
emitting device
layer
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PCT/IB2019/001370
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English (en)
Inventor
Venkata Ananth TAMMA
Kentaro Shimizu
Vernon K. WONG
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Lumileds Holding B.V.
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Priority claimed from US16/230,876 external-priority patent/US10804440B2/en
Application filed by Lumileds Holding B.V. filed Critical Lumileds Holding B.V.
Publication of WO2020128626A1 publication Critical patent/WO2020128626A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/50—Wavelength conversion elements
    • H01L33/501—Wavelength conversion elements characterised by the materials, e.g. binder
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/02—Use of particular materials as binders, particle coatings or suspension media therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/50—Wavelength conversion elements
    • H01L33/505—Wavelength conversion elements characterised by the shape, e.g. plate or foil
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
    • H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
    • H01L25/04—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
    • H01L25/075—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00
    • H01L25/0753—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00 the devices being arranged next to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
    • H01L2933/0008—Processes
    • H01L2933/0033—Processes relating to semiconductor body packages
    • H01L2933/0041—Processes relating to semiconductor body packages relating to wavelength conversion elements

Definitions

  • a typical light-emitting diode may include a glue layer between different layers of die LED such as, for example, between a substrate and a wavelength converting layer.
  • the glue layer may have a lower refractive index than both the substrate and the wavelength converting layer.
  • the critical angle for Total Internal Reflection may be low (e.g., ⁇ 52 degrees). This TIR causes a reduction in power transmitted from die substrate to the wavelength converting layer.
  • the glue layer may behave as a channel to guide photons along the interface between the substrate and wavelength converting layer. This channel may eventually cause leaking of photons from the edge of the LED.
  • An adhesive layer may include a plurality of short chain molecules, each of die plurality of the short chain molecules including a first end and a second end such that the distance between the first end and second end is less than 100 nm and such that first end is configured to attach to a first surface and the second end is configured to attach to a second surface.
  • Another adhesive layer may include a nanostructured layer imposing a local phase gradient that increases a critical angle for total internal reflection for light incident on the adhesive layer at an interface between layers bonded to each other by the adhesive layer and each having a higher index of refraction than the adhesive layer.
  • Another adhesive layer is disclosed that combines the features of the two adhesive layers summarized above.
  • Light emitting devices disclosed herein may advantageously employ any of the adhesive layers summarized above to attach a transparent substrate to a wavelength converter.
  • the adhesive layers increase the transmission of light from die substrate into the wavelength converter, compared to conventional adhesive layers.
  • An adhesive layer comprising short chain molecules may be very thin, frustrating total internal reflection at the adhesive layer interface.
  • the nanostructured layer increases the critical angle for total reflection at the interface, thus also reducing total internal reflection.
  • FIG. 1 A is a diagram of a portion of an example light emitting device showing an adhesive layer comprising short chain molecules bonding a transparent substrate to a wavelength converting layer;
  • FIG. IB is a diagram of an example light emitting device comprising layers as shown in FIG. 1 A;
  • FIG. 1C is a flow diagram for generating part of a light emitting device
  • FIG. 1 D is a diagram of an example light emitting device as in FIG. 1 B, comprising a nanostructured layer within the adhesive layer.
  • FIG. 1 E compares transmission of light from a substrate to a wavelength converting layer through a conventional adhesive layer and through an example adhesive layer comprising short chain molecules and a nanostructured layer.
  • FIG. 1 F shows an example multi nanophotonic structure that may be employed in nanostructured layers as described herein.
  • FIG.2 A is a diagram showing an example light emitting diode device
  • FIG. 2B is a diagram showing multiple LED devices
  • FIG. 3 is a diagram of an example application system.
  • Relative terns 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 elenent, 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 die figures.
  • LEDs Semiconductor light emitting devices or optical power emitting devices, such as devices that emit ultraviolet (UV) or infrared (JR) optical power, are among the most efficient light sources currently available (hereinafter“LEDs”). These 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.
  • UV ultraviolet
  • JR infrared
  • light sources e.g., flash lights and camera flashes
  • HUD heads up display
  • horticultural lighting street lighting
  • torch for video
  • general illumination e.g., home, shop, office and studio lighting, theater/stage lighting and architectural lighting
  • AR augmented reality
  • VR virtual reality
  • a single LED may provide light that is less bright than an incandescent light source, and, therefore, multijunction 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.
  • LEDs dial increase optical power transmitted through an adhesive layer and, thereby, improve die total flux emitted by the LED are disclosed herein.
  • the adhesive layer may be designed such that photon leaking from a side of the LED is reduced.
  • Adhesive layer composition, and nanostructure layers that increase transmitted optical power are disclosed.
  • substrates may be connected to wavelength converting layers using a glue layer without the chain link molecules disclosed herein.
  • glue layers typically have a thickness between .5 and 3 micrometers.
  • Such glue layer is typically an organic silicone with a refractive index that varies from 1.4 to 1.6, depending on the material type and composition.
  • the refractive index of the substrate (e.g., sapphire) and wavelength converting layers is typically higher than the refractive index such a glue layer.
  • typical values of refractive index (n) a t a wavelength 450nm are 1.78, 1.41 and 1.76, for sapphire, such typical glue layers, and wavelength converting layers, respectively.
  • TIR Total Internal Reflection
  • 9c 52.4 degrees when using typical glue layers.
  • TIR causes a reduction in foe power transmitted from substrate (e.g., sapphire) to the wavelength converting layer, through the glue layer.
  • substrate e.g., sapphire
  • typical glue layers can also exhibit channel behavior to guide photons along the interface of such glue layers and foe substrate, foe photons eventually leaking out from such a glue layer, at foe edge of the LED.
  • the TIR and the leaking of photons reduce the total flux emitted by an LED in foe forward direction.
  • the LEDs disclosed herein may include adhesive material with short chain molecules that allow the reduction of thickness of foe adhesive layer.
  • the thickness may be reduced to less than lOOnm or may be less than 1 (him such that it approaches near zero thickness.
  • foe LEDs disclosed herein may include a nanostructure layer disposed at foe interface between an adhesive layer and a substrate such that the nanostructure layer modifies foe critical angle for total internal reflection (TIR) to allow increased emission.
  • Fig. I A shows example short chain molecules 103.
  • Short chain molecules may include any short polymer chain such that at each end of the chain is a linker molecule.
  • short chain molecules may include short DNA strands that have linker molecules on each end.
  • short chain molecules include, but are not limited to, alkyl chains such as octyl phosphonic acid, decyl phosphonic acid, or octadecy lphosphonic acid but terminated on both ends by a phosphonic acid, carboxylic acid, and/or thiol groups.
  • carboxylic acids are found to react with aluminum oxides via a topotactic reaction such dial die carboxyl ate acts as a bridging ligand. This reaction allows for carboxy!ate-fimctiona!ized alumina nanoparticles to be prepared directly from boehmite (AIOOH).
  • LED layers 100A as shown in Fig. 1 A include a substrate 120 and an adhesive layer 104 which includes short chain molecules 103 and that connects the substrate 120 to a wavelength converting layer 102.
  • Fig 1 B shows LED device 100B which includes the LED layers 100A as well as device that includes an epitaxial grown semiconductor layers 130.
  • the epitaxial grown semiconductor layers 130 may include a first contact 131 and a second contact 132 separated by a gap 133 which may be an airgap or may be filled with dielectric material.
  • a p-type layer 134 may be proximate to an active layer 135 and an n-type layer 136.
  • the active layer 135 may be configured to emit light distal from the contacts 131 and 132 such that light beams emitted from the active layer 135 are generally emitted towards the substrate 120.
  • the LED device 100 is presented in a simplified form for ease of understanding of the invention, knowing that one possessing an ordinary skill in the pertinent arts would understand the other elements included wi Ain an LED.
  • the epitaxial grown semiconductor layers 130 may be formed from any applicable material configured to emit photons when excited including sapphire, SiC, GaN, Silicone and may more specifically be formed from a 111-V semiconductors including, but not limited to, AIN, AIP, 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 Aereof. These example materials may have indices of refraction ranging from about 2.4 to about 4.1 at the typical emission wavelengths of LEDs in which Aey are present
  • Aluminum nitride may be used and is a wide band gap (6.01-6.05 eV at room temperature) material.
  • AIN may have refractive indices of about 1.9- 2.2 (e.g., 2.165 at 632.8 nm).
  • HI-Nitride semiconductors such as GaN, may have refractive indices of about 2.4 at 500 nm, and 111 -Phosphide semiconductors, such as InGaP, may have refractive indices of about 3.7 at 600 nm.
  • An example gallium nitride (G&N) layer may take the form of a layer of pGaN .
  • GaN is a binary III/V direct bandgap semiconductor commonly used in light-emitting diodes. GaN may have a crystal structure with a wide band gap of 3.4 eV that makes the material ideal for applications in optoelectronics, high-power and high-frequency devices. GaN can be doped with silicon (Si) or with oxygen to create an n-type GaN and with magnesium (Mg) to create a p-type GaN as is used in the present example.
  • the active layer 135 is the region where light is emitted as electroluminescence occurs.
  • Contacts 131 and/or 132 coupled to the LED device 100 may be formed from a solder, such as AuSn, AuGa, AuSi or SAC solders.
  • LED device 100B of Fig. 1 B may be a high brightness emitter or a medium power emitter such as a chip scale package (CSP) die with a sapphire substrate.
  • adhesive layer 104 with short chain molecules 103 may be located between substrate 120 and wavelength con voting layer 102.
  • the substrate 120 may include a smooth LES that enables deposition of the adhesive layer 104 with short chain molecules
  • the substrate 120 may comprise sapphire which is an aluminum oxide (AbO?) also known as corundum and can exhibit properties including being very hard, strong, easy to machine flat, a good electrical insulator, and an excellent thermal conductor.
  • Sapphire is generally transparent when produced synthetically, with die blue color in naturally occurring sapphires (and the red in rubies, which are another form of corundum) comes from impurities in the crystal lattice.
  • the sapphire may be replaced with gallium nitride (GaN).
  • GaN gallium nitride
  • the semiconductor layers 130 may be in the region where light is emitted as electroluminescence occurs.
  • the sidewalls of the substrate 120 may be covered by sidewall material 140.
  • the sidewall material 140 may also cover one or more layers of the semiconductor layers 130 such that either the same sidewall material 140 covers die substrate 120 and die semiconductor layers 130 or a different material may cover die sidewalls of the substrate 120 than the semiconductor layers 130.
  • the sidewall material 140 may be any applicable reflecting or scattering material.
  • the sidewall material 140 may be a distributed Bragg reflector (DBR).
  • DBR distributed Bragg reflector
  • a flip chip of chip scale package (CSP) LED with a sapphire substrate is described, although the principles and teaching herein may be applied to any applicable LED design.
  • a sapphire based CSP emitter with a smooth light escape surface (LES) may allow deposition of adhesive layer 104 with short chain molecules 103 such that light emitted from the active layer 135 is incident upon the adhesive layer 104 with short chain molecules 103, via the sapphire substrate.
  • LES smooth light escape surface
  • Di represents die thickness of the adhesive layer 104 with short chain molecules 103.
  • the thickness Dl may be as small as possible and may be less than 1 OOnm or more preferably may be less than lOnm, or more preferably may approach zero. This small thickness Dl (e.g., approaching zero) may be obtained by use of the chain molecules 103 that provide the required amount of adhesion from the adhesive layer 104 while allowing its thickness to approach zero.
  • the adhesive layer 104 may include polymer materials with short molecular length or short length/chain polymer (collectively“short chain molecules 103”). As disclosed, the thickness of the adhesive layer 104 may be less than lOOnm, less than lOnm and preferably may approach 0. At such thickness, which are sub wavelength, the effect of Frustra te TIR (FTIR) will begin to dominate due to the tunneling of photons through the adhesive layer 104 thickness between the substrate 120 and wavelength converting layer 102.
  • the effect of FTIR with the disclosed implementation may be such that the lower refractive index of the adhesive layer 104 can be considered a potential barrio:, through which photons can tunnel.
  • the tunneling of the photons may negate or mitigate the effect of TIR such that the critical angle is effectively increased. Alternatively or in addition, die tunneling via the FTIR effect may negate or mitigate the photon leaking caused by channels created at typical adhesive layers.
  • Fig. 1C shows a flow diagram lOOC that outlines the steps 111 and 112 for manufacturing LED layers 100A and/or LED device 100B.
  • an adhesive layer with short chain molecules may be applied to a substrate.
  • the adhesive layer with short chain molecules may be applied via any applicable manner such as pouring, depositing (e.g., Atomic layer deposition (ALD)) chemical application, mesh deposition, or the like.
  • ALD Atomic layer deposition
  • a wavelength converting layer may be applied to the adhesive layer.
  • the wavelength converting layer may be applied in any applicable manner such as by pouring, depositing (e.g., Atomic layer deposition (ALD)) chemical application, mesh deposition, or the like.
  • a substrate e.g., 120 of Fig. 1 B
  • wavelength converting layer e.g., 102 of Fig. IB
  • SOM organosilane self-assembled monolayer
  • the evanescent waves and/or photons in the substrate region can tunnel through the adhesive layer, increasing the overall flux emitted by the LED,
  • the tunneling probability may be exponentially dependent on the thickness and properties of the adhesive layer or the gap occupied the adhesive layer as well as the wavevector of light. Accordingly, the total flux of the LED dependent on the product, or other applicable relationship, of the wavevector and adhesive layer/gap,
  • a nanostructure layer may be deposited at the interface between an adhesive layer and a substrate of an LED such that the adhesive layer attaches the substrate to a wavelength converting layer.
  • the adhesive layer may form a viable bond between the substrate and the wavelength converting layer and may have a low retractive index such as. for example, between 1.41-4.5.
  • the adhesive layer may include a nanostructure layer, as disclosed herein, and may also include one or more types of silicone.
  • the wavelength converting layer may be a ceramic phosphor platelet or any other applicable material that con verts the wavelength of light incident upon the layer, as disclosed herein.
  • a nanostructure layer may be deposited on top of a substrate at the interface between an adhesive layer and the substrate.
  • the nanostructure layer can be metamaterials or metasurfaces composed of cylinders or cubes made up of large refractive index materials such as titanium dioxide, gallium nitride or silicon.
  • the nanostructure layer may transmit radiation incident upon a substrate (e.g., radiation originating from an LED active layer) and extend the TISR critical angle beyond the natural TIR critical angle created by the change in refractive index (RI) (i.e, high RI of the substrate to low R1 of the adhesive layer).
  • RI refractive index
  • the nanostructure layer has a local phase gradient at the location where the light beams strike tire inter face of the nanostructure layer.
  • Equation 1 shows the general law of reflection and refraction: [0040]
  • the subscript ⁇ refers to the media loca ted a t the top of interface (i.e., the adhesive material) and T refers to media of incidence with is the local
  • phase gradient imposed by the nanostructure layer The critical angle can he shown by Equation 2.
  • Equation 2 can be applied such that the critical angle of TIE. can be modified using the local gradient of phase (i.e., of a nanostructure layer as disclosed herein) imposed by the nanostructure. For example, for an operating wavelength of 450nm and ofnt
  • nanostructure layer is arranged such that it has a local phase gradient with a slope sufficient to increase the TISR critical angle.
  • the example critical angle 6c :::: ⁇ 83 degrees is equivalent to having an effective refractive index of 1.765.
  • a nanostructure layer provides a modified effective RI of 1.765 for the adhesive layer by modifying the critical angle to be 6c "83 degrees.
  • This change in critical angle allows emission of light through the adhesive layer with a nanostructure layer as if the RI of the adhesi ve layer is an effective higher RI wh ich more closely matches the RI of the substrate and/or wavelength converting layer and, thus results in decreased reflection.
  • a nanostructure layer may include meta-surfaces, plasmonic nanostructures, meta- molecules, photonic crystals, and/or other applicable nanostructures.
  • photonic crystals and meta-surfaces may be periodic arrangements of meta-atoms and/or nanoantennas.
  • a meta-atom nanostructure lay er may include an array of meta-atoms.
  • a nanoantenna nanostructure layer may include one or more nanoantennas. Nanostmctared layers, as disclosed herein, may incorporate the design of LED devices with nano scale optical antennas placed on an LED surface (e.g., a sapphire substrate) and/or within an adhesive layer.
  • the nanostractured layers disclosed herein may include nanoantennas placed in a predetermined arrangement with an optimized local phase gradient within an adhesive layer.
  • a nanostruetured layer may include photonic materials incorporated into photonic crystals and/or meta-surfaces which may include meta-atoms and/or nanoantennas such that the largest dimension for a meta-atom or nanoantennas is less than 1 OOOnm.
  • nanoantennas can be implemented as an array of nanoparticles located in the nanostructure layer, as further disclosed herein.
  • the nanoantennas may be arranged in either periodic or a- periodic patterns.
  • a meta- surface is composed of meta-atoms with the meta-atoms combined together and interacting to gi ve the meta-surface unique optical properties.
  • the size of individual meta-surfaces may be sub-wavelength or may be formed at the same order of wavelength of use.
  • a nanostroctuied layer can include nanoantennas that are distributed throughout a host dielectric medium. The sizes of the nanoantennas may be a sub-wavelength of order of wavelength.
  • a nanostructured layer may be designed with a configuration so that its optical properties have a resonance or controllable properties at one or more wavelengths such that the configuration causes the TIR critical angle of incident based on the configuration of the nanostructure layer. This may be achieved by tuning die structure and chemical composition of the nanostructure layer so as to simultaneously excite electric and magnetic dipoles, quadrupoles and higher order multipoles within the nanostructure layer. The simultaneous excitation of the dipoles and higher order multipoles may provide the local phase gradient at the nanostructure layer to increase the TIR critical angle of the adhesive layer.
  • Fig. ID shows a LED device 100D which may be a high brightness emitter or a medium power emitter such as a chip scale package (CSP) die with a sapphire substrate.
  • LED device 100D may be similar to LED device 100B of Fig. 1C.
  • adhesive layer 105 with a nanostructure layer 110 may be located between substrate 120 and wavelength converting layer 102.
  • the substrate 120 may include a smooth LES that enables deposition of the adhesive layer 105 with a nanostructure layer 110.
  • the substrate 120 may comprise sapphire which is an aluminum oxide (AI2O3) also known as corundum and can exhibit properties including being very hard, strong, easy to machine flat, a good electrical insulator, and an excellent thermal conductor.
  • AI2O3 aluminum oxide
  • Sapphire is generally transparent when produced synthetically with the blue color in naturally occurring sapphires (and the red in rubies, which are another form of corundum) comes from impurities in the crystal lattice.
  • the sapphire may be replaced with gallium nitride (GaN).
  • the semiconductor layers 130 may be in the region where light is emitted as
  • the sidewalls of the substrate 120 may be covered by sidewall material 140.
  • the sidewall material 140 may also cover one or more layers of the semiconductor layers 130 such that either the same sidewall material 140 covers the substrate 120 and the semiconductor layers 130 or a different material may cover the sidewalls of the substrate 120 than the semiconductor layers 130.
  • the sidewall material 140 may be any applicable reflecting or scattering material.
  • the sidewall material 140 may be a distributed Bragg reflector (DBR).
  • DBR distributed Bragg reflector
  • a flip chip of chip scale package (CSP) LED with a sapphire substrate is described, although the principles and teaching herein may be applied to any applicable LED design.
  • a sapphire based CSP emitter with a smooth light escape surface (LES) may allow deposition of adhesive layer 105 with a nanostructure layer 110 such that light emitted from the active layer 135 is incident upon the adhesive layer 105 with a nanostructure layer 1 10 via the sapphire substrate.
  • the LED device 100D includes components and/or layers that are the same as LED device lOOB, as indicated by the same reference numbers.
  • Fig. 1 E shows an LED device I00E with a substrate 120A, adhesive layer 105 A* and wavelength converting layer 102 A.
  • the RI of the substrate I20A and wavelength converting layer 102A may be higher than the Rl of the adhesive layer 105A such that the TIR critical angle Oc :::: 52.4.
  • the light beam 107A may traverse the substrate 120A and may be incident upon the adhesive layer 105A at an angle greater than the TIR critical angle 6c - 52.4, such as at 60 degrees. Accordingly, the light beam 107 A maybe reflected, as shown.
  • Fig. IE also shows an LED device 100F with a substrate 120B, adhesive layer 105B, and wavelength converting layer 102B.
  • the adhesive layer 105B includes a nanostructure layer 110B configured with an optimized local phase gradient of the adhesive layer 105B.
  • the Rl of the substrate 120B and wavelength converting layer 102B may be higher than the Rl of the adhesive layer 105B material without the nanostructure layer HOB.
  • the TIR critical angle through die adhesive layer 105 B may be greater than Oc :::: 52.4 and may be, for example, Oc :::: -83 degrees.
  • a light beam 107B may traverse the substrate 120A and may be incident upon the adhesive layer 105B at the same angle as light beam 107 A was incident upon the adhesive layer 105A of LED device 100E (i.e., 60 degrees according to this example). Based on the increased critical angle of Oc - -83 degrees provided by the nanostructure layer 11 OB, the light beam 107B may be passed through the adhesive layer 105B without being reflected and may be incident upon the wavelength converting layer 102B.
  • Photonic crystals and/or meta-surfaces in a nanostructure layer may be configured with a spatial gradient of phase.
  • the nanoantenna may be formed from nanocylinders, nano-cones, or nano-cones with vertical or coaxial dimmers, arranged in either a hexagonal or rectangular lattice. The lattice period may be sub-wavelength or larger than wavelength.
  • the nanoantennas may be Huygen’s meta-atoms or support waveguide modes. A Huygen’s nanostructure layer with spatial variation of radius can also be used to achieve the desired narrowing of die beam.
  • Each photonic crystal or meta-surface may present a certain amount of beam bending properties such that incident beams can be shaped to the required angular distribution.
  • interfering modes within the meta-atom or nanoantenna provide additional control of the light emitted through the nanostructure layer, using structural parameters.
  • Nanoantennas may be formed or arrayed as single nano-photonic structures such that the same nanoantenna is repeated numerous times to form a nanostructured layer.
  • nanoantennas may be formed or arrayed as multi nano-photonic structures such that an array of nanoan tennas is repeated numerous times to form a nanostructured layer.
  • Figure IF illustrates an example multi nano-photonic structure 145.
  • the multi nano-photonic structure 145 includes nano-cylinders 141 and 142 such that the different nano-cylinders 141 and 142 have one or more different properties when compared to each other.
  • nano-cylinder 142 is smaller in volume than the nano-cylinder 141.
  • This multi nano-photonic structure may be arrayed such that nanostructure layer 110 of Fig.
  • ID includes multiple iterations of multi nano-photonic structure 145 (in one, two, or three dimensions).
  • Each small multi nano- photonic structure 145 of a nanostructure layer 110 may contribute to the optimized local phase gradient at the location where a light beam strikes the nanostructure layer 110.
  • the design and placement of nanostructure layer 110 may selected by an optimizer.
  • the nanostructure layer may include nano-cylinders or nano-cones of titanium dioxide with heights of 150nm, 250nm or 600nm.
  • the radii of the cylinders may be varied in the lateral axes and can be in the range from 50nm to 120nm with periodicities ranging from 250nm to 300nm.
  • Different unit cells with different periods and radii distributions can be arranged on a substrate surface.
  • the position of such spheres can be optimized using conventional optimization software to improve the overall flux emitted by an LED.
  • nanostructures may only be optimized to work within a desired wavelength such as, for example, a blue LED emission spectral region (center wavelengths varying from 440-450 nm with bandwidths of 30-50nm).
  • side reflectors 140 may be non-specularly reflective nanostructured layers designed to further enhance light output through
  • nanostructured layer 110 is a nanostructured layer 110.
  • side reflectors 140 may be nanostructured layers designed such that light incident on them at low angles of incidence (e.g., normal or near normal) is reflected at a large oblique angle of reflection toward nanostructured layer 110 at an angle of incidence on nanostructured layer 110 within the range of angles transmitted through the adhesive layer.
  • a back reflector located between the active region and the contacts may be a nanostmctured layer designed such that light incident on it at large oblique angles is reflected at a low angle of reflection toward the adhesive layer at an angle of incidence within the range for transmission through adhesive layer.
  • Nanostmctured ide reflectors as just described may be used in combination with a nanostmctured back as just described.
  • Nanostmctured side reflectors and back reflectors as just described may take die form of a nanostmctured photonic layer designed to steer angular radiation.
  • a nanostmctured side or back reflector may include or consist of a photonic crystal, metamaterial, metasurface or subwavelength gratings of asymmetric scattering elements (also referred to herein as nanoantennas), by way of non-limiting example only.
  • the main junction of such a nanostmctured side or back reflector is to reflect radiation incident upon it from a given angular range to a chosen angular range. This restricted angular range may be chosen to direct as much light as possible from the rear surface or sides of the LED toward the adhesive layers at angles of incidence less than the critical angle for total internal reflection at the interface with the adhesive layer.
  • Such a nanostmctured back or side reflector may comprise scattering elements formed into, or arrayed, into unit cells. Each unit cell may provide beam bending to the light incident on the side reflector. By suitably arranging a multitude of different unit cells with different beam bending properties, tire light may be shaped to the required angular distribution.
  • the reflective beam-benders may be arranged in a periodic two-dimensional pattern or grating, for example, and may be formed of background material encapsulating or otherwise containing one or more scattering elements and positioned adjacent to substrate 120.
  • the plurality of scattering elements may be surrounded by the background material.
  • a specular reflector may be adjacent to the background material distal to substrate 120.
  • Asymmetrical scattering may be achieved, for example, by using asymmetric scattering elements designed to link the reflected fields from the specular reflector to the scattered fields from scattering elements. Interference between these fields causes light to be scattered in a particular direction. Die arrangement of scattering elements may produce a spatial gradient of phase.
  • a unit cell for a periodic array of beam benders in a nanostmctured side reflector may be rectangular in dimensions and include a series of layers including a specular reflector, one or more scattering elements, and background material as described above. Periodicity may be centered on a wavelength in use, such as for example the peak wavelength emitted by the LED (e.g., 450 nm).
  • one or mote scattering elements may be positioned adjacent to substrate layer 120 distal to die specular reflector and / or one or more scattering elements may be places in contort, or near contact, with the specular reflector.
  • the scattering elements may be of any suitable height and width and may be formed, for example, from silicon (Si) or titanium oxide (TiCh), or a combination thereof.
  • the background material may be a low refractive index material, such as magnesium fluoride (MgFr), for example.
  • the specular reflector if present, may be a metal mirror, for example a gold or silver mirror, a dielectric mirror, or a Bragg reflector, for example.
  • the scattering elements may take the form of any of the scattering elements described herein.
  • a scattering element may comprise a single light scatterer (a single dipole), or an array of light scatterers (dipoles) that maybe configured analogously to a yagi-uda antenna, for example.
  • a scattering element may be designed as two interfering Huygen’s meta-atoms.
  • the scattering elements may be selected to satisfy the first Kerker’s conditions so that the magnetic and electric dipole radiation cancel in the backward direction yielding a large forward scatter, referred to as Huygen’s meta-atoms.
  • a scattering element may be formed as a two-dimensional scatterer, such as a grating, for example, or a three-dimensional scatter.
  • An example three-dimensional scatter may be a nano-cylinder.
  • Other geometrical scatterers may also be employed includes L-shaped scatterers, for example.
  • the scattering elements may be formed, for example, from nano-cylinders, nanocones, or nano-cuboids arranged for example in either a hexagonal or a rectangular lattice.
  • the lattice period may be sub-wavelength or larger than wavelength.
  • interfering modes within the meta-atom or nanoantenna provide additional control of the scattered modes using structural parameters.
  • the scattering elements may also be formed from photonic metamaterial (PM), also known as an optical metamaterial, which is a type of electromagnetic metamaterial that interacts with light, covering terahertz (THz), infrared (IR) or visible wavelengths.
  • PM photonic metamaterial
  • the materials employ a periodic, cellular structure.
  • the subwavelength periodicity distinguishes photonic metamaterials from photonic band gap or photonic crystal structures.
  • the cells are on a scale that is magnitudes larger than atoms, yet much smaller than the radiated wavelength, and are on the order of nanometers. In metamaterials, cells take the role of atoms in a material that is homogeneous at scales larger than the cells, yielding an effective medium model.
  • FIG.2A is a diagram of an LED device 200 in an example embodiment
  • the LED device 200 may include one or more epitaxial layers 202, an active layer 204, and a substrate 206.
  • an LED device may include a wavelength converter layer and/or primary optics.
  • die active layer 204 may be adjacent to the substrate 206 and emit light when excited.
  • the epitaxial layers 202 may be proximal to the active layer 204 and/or one or more intermediate layers may be between the active layer 204 and epitaxial layers 202.
  • the substrate 206 may be proximal to the active layer 204 and/or one or more intermediate layers may be between die active layer 204 and substrate 206.
  • the active layer 204 «nits light into the substrate 206.
  • the adhesive layer 105 of Fig. ID or the nanostructure layer 110 may be placed between substrate 206 and wavelength converting layer 206C, to implement techniques disclosed herein.
  • FIG. 2B shows a cross-sectional view of a lighting system 220 including an LED array 210 with pixels 201A, 201B, and 201C.
  • the LED array 210 includes pixels 201 A, 201 B, and 201C each including a respective substrate 206B active layer 204B and an epitaxial layer 202B.
  • Pixels 201 A, 201B, and 201C, in the LED array 210 may be formed using array segmentation, or alternatively using pick and place techniques and may, for example, emit light at different peak wa velengths such as red, green, and blue.
  • the spaces 203 shown between one or more pixels 201 A, 201B, and 201 C may include an air gap or may be filled by a material such as a metal material which may be a contact (e.g., n- contact).
  • secondary optics such as one or mote lenses and/or one or more waveguides may be provided.
  • wavelength converting layers 210A, 210B, and 210C may be placed above respective pixels 201 A, 201B, and 201B and may be attached by respective adhesive layers and/or nanostructure layers.
  • the respective adhesive layers may include chain link molecules and/or nanostructure layers, as disclosed herein.
  • the pixels 201 A, 201 B, and 201C may each correspond to a different color output (e.g., red, green, blue).
  • the LED device 200 or pixels 201 A, 201B, and 201C may be single wavelength emitters and may be powered individually or via as an array.
  • FIG. 3 shows an example system 550 which includes an application platform 560 and LED systems 552 and 556.
  • the LED system 552 produces light beams 561 shown between arrows 561a and 561b.
  • the LED system 556 may produce light beams 562 between arrows 562a and 562b.
  • the LED system 552 and 556 may be part of an automobile and may emit infrared (IR) light communication beams such that an oncoming vehicle in the path of the light beams 561 and/or 562 is able to receive communication from the automobile.
  • 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 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
  • One or more sensors may be internal or external to the housing of die application platform 560.
  • application platform 560 sensors and/or IED 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 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.
  • sensing equipment may be located on an automobile and may emit a beam using a vertical-cavity surface-emitting laser (VCSEL).
  • VCSEL vertical-cavity surface-emitting laser
  • the one or more sensors may sense a response to the emitted beam or any other applicable input

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Power Engineering (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Led Device Packages (AREA)
  • Led Devices (AREA)

Abstract

L'invention concerne une couche adhésive qui peut comprendre une pluralité de molécules à chaîne courte, la pluralité de molécules à chaîne courte comprenant chacune une première extrémité et une seconde extrémité telles que la distance entre la première extrémité et la seconde extrémité est inférieure à 100 nm et telles que la première extrémité est configurée pour se fixer à une première surface et la seconde extrémité est configurée pour se fixer à une seconde surface. L'invention concerne également une autre couche adhésive qui peut comprendre une couche nanostructurée imposant un gradient de phase local qui fait augmenter un angle critique de réflexion interne totale de lumière incidente sur la couche adhésive au niveau d'une interface entre des couches liées l'une à l'autre par la couche adhésive et ayant chacune un indice de réfraction supérieur à celui de la couche adhésive. L'invention concerne également une autre couche adhésive qui combine les caractéristiques des deux couches adhésives résumées ci-dessus.
PCT/IB2019/001370 2018-12-21 2019-12-21 Extraction de lumière améliorée au moyen d'une couche adhésive entre une del et un convertisseur WO2020128626A1 (fr)

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US16/230,876 2018-12-21
US16/230,876 US10804440B2 (en) 2018-12-21 2018-12-21 Light extraction through adhesive layer between LED and converter
EP19157215 2019-02-14
EP19157215.5 2019-02-14

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