Protective layer for light emitting diodes

Abstract

The particle layer is located above the light output surface of the light emitting diode. The transparent protective layer is located between the light output surface and the particle layer and contacts the light output surface and the particle layer. The particle layer includes a large number of optically scattering or luminescent particles and a thin coating of transparent material coating the large number of particles. The particles are characterized by a D50 greater than about 1.0 μm and less than about 30 μm; the thickness of the coating is less than about 0.20 μm. The thickness of the protective layer is less than about 0.07 μm and includes one or more materials different from the coating material. The protective layer and the coating may each include one or more metal or semiconductor oxides. The oxide precursor of the protective layer material is less reactive than the coating material relative to the corresponding light output surface.

Description

[0001] Priority claim

[0002] This application claims priority to U.S. Non-Provisional Application No. 17 / 066,278, entitled “PROTECTIVE LAYER FOR LIGHT EMITTING DIODES,” filed on October 8, 2020 in the name of inventors Meyer et al. and applicant Lumileds LLC, which is incorporated herein by reference as if set forth in its entirety. Technical Field

[0003] The present invention generally relates to light emitting diodes and phosphor converted light emitting diodes. Background Art

[0004] Semiconductor light emitting diodes and laser diodes (collectively referred to herein as "LEDs") are among the most efficient light sources currently available. The emission spectrum of an LED typically exhibits a single narrow peak at a wavelength determined by the structure of the device and the composition of the semiconductor material from which it is constructed. By appropriately selecting the device structure and material system, an LED can be designed to operate at ultraviolet, visible, or infrared wavelengths.

[0005] The LED may be combined with one or more wavelength converting materials (generally referred to herein as "phosphors") that absorb light emitted by the LED and in response emit light of a longer wavelength. For such phosphor-converted LEDs ("pcLEDs"), the fraction of light emitted by the LED that is absorbed by the phosphor depends on the amount of phosphor material in the path of the light emitted by the LED, for example, on the concentration of the phosphor material in a phosphor layer disposed on or around the LED and the thickness of the layer.

[0006] Phosphor-converted LEDs can be designed so that all light emitted by the LED is absorbed by one or more phosphors, in which case the emission from the pcLED is entirely from the phosphors. In this case, for example, the phosphors can be selected to emit light in a narrow spectral region that is not efficiently produced directly by the LED.

[0007] Alternatively, the pcLED can be designed so that only a portion of the light emitted by the LED is absorbed by the phosphor, in which case the emission from the pcLED is a mixture of the light emitted by the LED and the light emitted by the phosphor. By appropriately selecting the LED, phosphor, and phosphor composition, such a pcLED can be designed to emit, for example, white light having a desired color temperature and desired color rendering characteristics.

[0008] Multiple LEDs can be formed together on a single substrate to form an array. Such an array can be used to form active lighting displays, such as those employed in smartphones and smart watches, computer or video displays, or signage. An array having one or a few or many individual devices per millimeter (e.g., a device spacing of about one millimeter, a few hundred microns, or less than 100 microns, and a spacing of less than 100 microns or only tens of microns or less between adjacent devices) is typically referred to as a miniLED array or microLED array (alternatively, a μLED array). Such a miniLED array or microLED array may also include a phosphor converter as described above in many instances; such an array may be referred to as a pc-miniLED array or a pc-microLED array. In the description that follows, Summary of the invention

[0009] For each of one or more semiconductor light emitting diodes, a corresponding particle layer is located above the corresponding light output surface of each light emitting diode. A corresponding transparent protective layer is located between each light output surface and the corresponding particle layer and contacts each light output surface and the corresponding particle layer. The particle layer includes a large number of optically scattering or luminescent particles and a thin coating of transparent material coating a large number of particles. The particles are characterized in that D50 is greater than about 1.0 μm and less than about 30 μm, and the thickness of the coating is less than about 0.20 μm. The thickness of the protective layer is less than about 0.07 μm and includes one or more materials different from the coating material. The material of the protective layer may include one or more metal or semiconductor oxides, and the coating may include one or more metal or semiconductor oxides. The protective layer material may be characterized in that the reactivity of one or more oxide precursors is less than the reactivity of such oxide precursors that characterizes the coating material relative to the corresponding light output surface. One or more light emitting diodes and the corresponding protective layer and particle layer may be arranged into an LED array, a pcLED array, a miniLED array, a pc-miniLED array, a microLED array, or a pc-microLED array.

[0010] Objects and advantages associated with LEDs, pcLEDs, miniLED arrays, pc-miniLED arrays, microLED arrays, and pc-microLED arrays may become apparent when referring to the example embodiments illustrated in the accompanying drawings and disclosed in the following written description or appended claims.

[0011] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is neither intended to identify key features or essential features of the claimed subject matter nor to be used as an aid in determining the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic cross-sectional view of an example pcLED is shown.

[0013] Figure 2A and Figure 2B Schematic cross-sectional and top views of an example array of pcLEDs are shown, respectively. Figure 2C A schematic top view of an example miniLED or microLED array and an enlarged portion of a 3×3 LED of the array is shown. Figure 2D A perspective view of several LEDs of an example pc-miniLED or pc-microLED array monolithically formed on a substrate is shown.

[0014] Figure 3A shows a schematic top view of an example electronic board upon which a pcLED array may be mounted, and Figure 3B Similarly, the installation Figure 3A An example pcLED array on an electronics board.

[0015] Figure 4A A schematic cross-sectional view of an example array of pcLEDs arranged relative to a waveguide and projection lens is shown. Figure 4B shows the difference between the case without waveguide and Figure 4A The arrangement is similar to the arrangement of .

[0016] Figures 5A to 5C A schematic cross-sectional view of an example LED including a semiconductor LED and a particle layer is shown, with no protective layer between the LED and the particle layer.

[0017] FIG. 6A to FIG. 6C A schematic cross-sectional view of an example LED including a semiconductor LED and a particle layer with a protective layer between the LED and the particle layer is shown.

[0018] FIG. 7A to FIG. 7C Steps in an example method for making an example pcLED including a semiconductor LED and a protective layer between a particle layer are schematically illustrated.

[0019] Figure 8 is a graph showing comparative reliability results for LEDs with and without a protective layer between the LED and particle layer.

[0020] The depicted embodiments are shown schematically only; all features may not be shown in full detail or in proper scale; certain features or structures may be exaggerated or reduced relative to other features or structures, or omitted entirely, for the sake of clarity; the drawings should not be considered to be to scale unless explicitly indicated to be to scale. For example, the vertical dimensions or layer thicknesses of individual LEDs may be exaggerated relative to their lateral extents or relative to substrate or phosphor thicknesses. The embodiments shown are examples only and should not be construed to limit the scope of the present disclosure or the appended claims. DETAILED DESCRIPTION

[0021] The following detailed description should be read with reference to the accompanying drawings, in which the same reference numerals throughout the different figures refer to similar elements. The drawings, which are not necessarily to scale, depict selective embodiments and are not intended to limit the scope of the invention. The detailed description illustrates the principles of the invention by way of example, not by way of limitation.

[0022] Figure 1 An example of an individual pcLED 100 is shown, which includes a semiconductor diode structure 102 (collectively referred to herein as an LED) disposed on a substrate 104, and a wavelength conversion structure (e.g., a phosphor layer) 106 disposed on the LED. The semiconductor diode structure 102 generally includes an active region disposed between an n-type layer and a p-type layer. Application of a suitable forward bias across the semiconductor structure results in light emission from the active region. The wavelength of the emitted light is determined by the composition and structure of the active region.

[0023] For example, the LED may be a Group III nitride LED that emits blue, violet, or ultraviolet light. LEDs formed from any other suitable material system and emitting any other suitable wavelength of light may also be used. Other suitable material systems may include, for example, Group III phosphide materials, Group III arsenide materials, and Group II-IV materials.

[0024] Any suitable phosphor material may be used depending on the desired optical output from the pcLED.

[0025] Figure 2A-2B A cross-sectional view and a top view, respectively, of an array 200 of pcLEDs 100 disposed on a substrate 202, each pcLED 100 including a phosphor pixel 106. Such an array may include any suitable number of pcLEDs arranged in any suitable manner. In the illustrated example, the array is depicted as being monolithically formed on a shared substrate, but alternatively, the pcLED array may be formed from separate individual pcLEDs. The substrate 202 may optionally include CMOS circuitry for driving the LEDs, and may be formed from any suitable material.

[0026] like Figure 3A-3B As shown in , the pcLED array 200 can be mounted on an electronic board 300 that includes a power and control module 302, a sensor module 304, and an LED attachment area 306. The power and control module 302 can receive power and control signals from an external source and signals from the sensor module 304, and the power and control module 302 controls the operation of the LEDs based on these signals. The sensor module 304 can receive signals from any suitable sensor, such as from a temperature or light sensor. Alternatively, the pcLED array 200 can be mounted on a board (not shown) separate from the power and control module and the sensor module.

[0027] Optionally, each pcLED may include, or be arranged in combination with, a lens or other optical element positioned adjacent to or disposed on the phosphor layer. Such an optical element (not shown) may be referred to as a "primary optical element". Figure 4A-4B As shown in , pcLED array 200 (e.g., mounted on electronic board 300) can be arranged in combination with secondary optical elements (such as waveguides, lenses, or both) for use in an intended application. Figure 4A In FIG. 4 , light emitted by pcLED 100 is collected by waveguide 402 and directed to projection lens 404. For example, projection lens 404 may be a Fresnel lens. For example, this arrangement may be suitable for use in a motor vehicle headlight. Figure 4B In the embodiment of the present invention, the light emitted by the pcLED 100 is collected directly by the projection lens 404 without the use of an intervening waveguide. This arrangement can be particularly suitable when the pcLEDs can be spaced sufficiently close to each other, and can also be used in automotive headlight and camera flash applications. For example, miniLED or microLED display applications can use the same Figure 4A-4B An optical arrangement similar to the optical arrangement depicted in . In general, any suitable arrangement of optical elements can be used in combination with the pcLEDs described herein, depending on the desired application.

[0028] Figure 1 A may include, for example, more than 10,000 pixels in any applicable arrangement, such as a 100×100 matrix, a 200×50 matrix, a symmetric matrix, an asymmetric matrix, etc. It will also be understood that multiple pixel sets, matrices, and / or panels may be arranged in any applicable format to implement the embodiments disclosed herein.

[0029] although Figure 2A and Figure 2B A 3×3 array of nine pcLEDs is shown, but such an array may include, for example, 102 , 10 3 , 10 4 or more LEDs, such as Figure 2C Each LED 911 (ie, pixel) may have a width w in the plane of the array 900 of, for example, less than or equal to 1 millimeter (mm), less than or equal to 500 micrometers, less than or equal to 100 micrometers, or less than or equal to 50 micrometers. 1 LEDs 911 in array 900 may be arranged in a plane of array 900 with a width w of, for example, hundreds of micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 20 micrometers, less than or equal to 10 micrometers, or less than or equal to 5 micrometers. 2 The streets, lanes or trenches 913 are separated from each other. 1 Yes 1 and w 2 While the illustrated example shows rectangular pixels arranged in a symmetrical matrix, the pixels and arrays may have any suitable shape or arrangement. Multiple separate LED arrays may be combined in any suitable arrangement in any applicable format.

[0030] The dimension w in the array plane 1 LEDs with a side length of less than or equal to about 0.10 mm are often referred to as microLEDs, and an array of such microLEDs may be referred to as a microLED array. 1 LEDs with (eg, side lengths) between about 0.10 mm and about 1.0 mm are often referred to as miniLEDs, and arrays of such miniLEDs may be referred to as miniLED arrays.

[0031] Arrays of LEDs, miniLEDs, or microLEDs, or portions of such arrays, may be formed as segmented monolithic structures in which individual LED pixels are electrically isolated from one another by trenches and / or insulating materials. Figure 2DA perspective view of an example of such a segmented monolithic array 1100 is shown. The pixels in the array are separated by trenches 1130, which are filled to form n-contacts 1140. The monolithic structure is grown or disposed on a substrate 1114. Each pixel includes a p-contact 1113, a p-GaN semiconductor layer 1112, an active region 1111, and an n-GaN semiconductor layer 1110. A wavelength converter material 1117 may be deposited on the semiconductor layer 1110 (or other intervening layers as applicable). A passivation layer 1115 may be formed within the trenches 1130 to separate at least a portion of the n-contact 1140 from one or more layers of semiconductor. The n-contact 1140 or other material within the trenches may extend into the converter material 1117 so that the n-contact 1140 or other structure or material provides a complete or partial optical isolation barrier 1120 between pixels.

[0032] Each LED (pixel) in the LED array can be individually addressable, can be addressable as part of a group or subset of pixels in the array, or can be non-addressable. Therefore, for any application that requires or benefits from fine-grained intensity, spatial and temporal control of light distribution, the luminescent pixel array is useful. These applications may include, but are not limited to, precise special patterning of the emitted light from a pixel block or individual pixels. Depending on the application, the emitted light can be spectrally distinct, adaptive over time, and / or environmentally responsive. The luminescent pixel array can provide pre-programmed light distribution with various intensity, space, or time patterns. The emitted light can be based at least in part on received sensor data and can be used for optical wireless communication. The associated electronic devices and optical devices can be distinct at the pixel, pixel block, or device level.

[0033] For a variety of different reasons, it may be desirable to form a particle layer 505 on the light output surface 102D of a semiconductor LED 102 (including the active light emitting region 102A between one or more semiconductor layers 102B and one or more semiconductor layers 102C). The particle layer 505 includes a thin transparent coating 505B on particles 505A. The particles 505A can be optically scattering particles or luminescent particles or both, and can include any suitable material or materials (e.g., glass, ceramic, crystalline or polycrystalline, etc.). In some examples, the particle layer 505 forms a wavelength conversion phosphor layer on the light output surface of the LED; the coating 505B can be used to bond the particles 505A to each other and to the light output surface 102D (e.g., as Figure 5A15 / 802,273 and 16 / 887,618). By selecting a coating material with a suitably large refractive index, the scattering efficiency of phosphor layer 505 can be increased, which can be beneficial, for example, for increasing the contrast between adjacent light emitting diodes of an array (e.g., as disclosed in U.S. Application No. 16 / 887,618). In some examples, particle layer 505 can be arranged to adhere separate wavelength conversion phosphor layer 106 to light output surface 102D of LED 102 (e.g., as disclosed in U.S. Application No. 16 / 887,618). Figure 5B In some examples, the particle layer 505 is index matched or nearly index matched to the light output surface of the LED 102D, such that the particle layer 505 acts as an optical coupling structure that enhances the extraction of light from the LED 102 through the light output surface 102D (e.g., as Figure 5C 16 / 597,455). Each of the three patent applications mentioned in this paragraph is incorporated by reference in its entirety.

[0034] The particles 505A are typically submicron to micron-sized, for example, characterized by a D50 (i.e., a median lateral dimension) greater than about 0.10 μm and less than about 20 μm. The particles 505A can be applied to the light output surface 102D in any suitable manner, such as by spraying, deposition, etc. Then, a coating 505B is deposited onto the particles 505A and portions of the light output surface 102D. The coating 505B is deposited using a conformal deposition process so that it coats all sides of the particles 505A while remaining sufficiently thin (e.g., less than about 0.30 μm); if allowed to proceed, the deposited coating material 505B can fill the gaps between the particles 505A. Typically, atomic layer deposition (ALD) or other suitable chemical vapor deposition (CVD) processes are used to deposit the coating material 505B. A typical ALD reaction is divided into (at least) two parts. In the first step, an oxide precursor (metal or semiconductor) is fed into the reactor and adsorbs and / or reacts with reactive groups on the surface; substantially all unreacted or unadsorbed precursor molecules are removed by reactor purge. In the second step, an oxygen source (e.g., water or ozone) is fed into the reactor and reacts with a metal or semiconductor source on the particle surface; the reactor purge substantially removes all remaining oxygen source molecules and hydrolysis products formed by the condensation reaction. Due to the self-limiting nature of the surface reaction, these two steps lead to the formation of an atomic layer (or monolayer). These atomic layer reaction steps are repeated multiple times to form the final ALD coating. The stepwise nature of the ALD process also allows conformal coatings to be formed on and in structures with large aspect ratios (e.g., phosphor particles). The ALD process also allows layers of different components to be deposited by continuously feeding different oxide precursors into the reactor to form multi-component layers or nano-laminated materials with customized optical properties.

[0035] In some examples, coating material 505B includes one or more metal or semiconductor oxides. Examples of suitable materials may include, for example, Al 2 O 3 , HfO 2 、SiO 2 , Ga 2 O 3 ,GeO 2 SnO 2 CrO 2 、TiO 2 、 2 O 5 , Nb 2 O 5 、V 2 O 5 , Y 2 O 3 or ZrO 2In ALD and other CVD processes, various oxide precursors are used (in gaseous form) which react to deposit the desired material on the surface. Examples of oxide precursors include, for example, one or more metal or semiconductor halides, amides, alkylamides, or alkoxides, or other metals, semiconductors, or organometallic compounds (organometallic compounds that include at least one bond between carbon and a metal or metalloid). Examples of specific precursors may include, but are not limited to: Al(CH 3 ) 3 , HAl(CH 3 ) 2 、Hf(N(CH 3 ) 2 ) 4 、Hf(N(CH2CH 3 ) 2 ) 4 、TaCl 5 、Ta(N(CH 3 ) 2 ) 5 、ZrCl 4 、Zr(N(CH 3 ) 2 ) 4 、TiCl 4 、Ti(OCH 3 ) 4 、Ti(OEt) 4 、SiCl 4 , H 2 N(CH 2 ) 3 、Si(OEt) 3 、Si(OEt) 4 , tert-(butylimino)-tris(diethylamino)-niobium, or tris(ethylcyclopentadienyl)yttrium.

[0036] However, it has been observed that in some instances, exposing the light output surface 102D (typically the surface of a III-V semiconductor) to certain oxide precursors can degrade the surface, resulting in reduced device lifetime or reliability. For example, in the case of using trimethylaluminum (TMA; Al(CH 3 ) 3 ) Al is deposited on the light output surface of GaN-based light-emitting diodes 2 O 3 Thereafter, such degradation is significant.It would be desirable to reduce or prevent such degradation of the light output surface 102D during deposition of the coating material 505B.

[0037] Therefore, the light emitting device 100 including the semiconductor LED 102 (including the active region 102A and the semiconductor layers 102B and 102C) and the particle layer 505 may further include a protective layer 103 (e.g., such as a protective layer 103) between and in contact with the light output surface 102D and the particle layer 505 on its light emitting surface 102D. Fig. 6A , 6B 6C). The particle layer 505 is located above the light output surface 102D and includes a plurality of particles 505A and a thin coating 505B. The particles 505A can be optically scattering, luminescent, or both, and are characterized by a D50 (i.e., median size) greater than about 0.10 μm and less than about 20 μm. The coating 505B of transparent material coats the particles 505A and has a thickness of less than about 0.30 μm, or less than about 0.20 μm, or less than about 0.10 μm. The transparent protective layer 103 is located between the light output surface 102D and the particle layer 505 and contacts the light output surface 102D and the particle layer 505. The thickness of the protective layer 103 is less than about 0.07 μm, less than about 0.05 μm, less than about 0.03 μm, or less than about 0.020 μm, and includes one or more materials different from the coating material. In examples where protective layer 103 includes multiple materials, those materials may be arranged as multiple discrete sub-layers of protective layer 103; in such examples, the thickness of each of those layers may be less than about 0.020 μm, or less than about 0.010 μm.

[0038] Multiple LEDs 102 with multiple corresponding protective layers 103 and particle layers 505 can be arranged as an LED array, a miniLED array, or a microLED array. If arranged as a miniLED array, each LED 102 has a lateral dimension of less than about 1.0 mm and is separated from adjacent LEDs 102 of the array by less than about 0.10 mm. If arranged as a microLED array, each LED 102 (i) has a lateral dimension of less than about 0.10 mm or less than about 0.05 mm, and (ii) is separated from adjacent light-emitting diodes of the array by less than about 0.05 mm, less than about 0.020 mm, or less than about 0.010 mm. In some examples, each LED 102 of the array has a combined thickness of layers 102A / 102B / 102C that is less than about 5.0 μm.

[0039] In many examples, the material of protective layer 103 includes one or more metal or semiconductor oxides; in many examples, coating 505B includes one or more metal or semiconductor oxides. The material of protective layer 103 is characterized by one or more oxide precursor reactivity relative to the corresponding light output surface 102D being less than the reactivity of such oxide precursors characterizing the material of coating 505B. By selecting such a material, degradation of the light output surface can be reduced or eliminated. The less active oxide precursor of protective layer 103 can react and form a less degraded or non-degraded layer of light output surface 102D. In the case where light output surface 102D is so protected, its corresponding oxide precursor can be used to form coating 505B without degrading (or further degrading) the light output surface 102D; the presence of protective layer 103 prevents such degradation (or further degradation), and protective layer 103 protects light output surface 102D from contact with the oxide precursor of coating 505B.

[0040] In some examples, the material of the protective layer 103 may include a material selected from the group consisting of HfO 2 、SiO 2 , Ga 2 O 3 ,GeO 2 SnO 2 CrO 2 , Nb 2 O 5 、TiO 2 、 2 O 5 、V 2 O 5 , Y 2 O 3 and ZrO 2 Layers of those materials, and especially multiple layers of different materials selected from those materials, are known to form dense, pinhole-free layers that are nearly impermeable to air (such as water) or trimethylaluminum (TMA, an aluminum oxide precursor). Such an impermeable layer may be desirable for forming protective layer 103. In some examples, the material of coating 505B may include a layer consisting of Al 2 O 3 , HfO 2 、SiO 2 , Ga 2 O 3 ,GeO 2 SnO 2 CrO 2 , Nb 2 O 5 、TiO 2 、 2 O5 、V 2 O 5 , Y 2 O 3 and ZrO 2 The selection of one or more specific materials for the protective layer 103 may be limited by the material used for the high refractive index material 505B. For example, if TiO 2 As the high refractive index material 505B, the protective layer 505B will be made of different materials, wherein the corresponding oxide precursor has a higher reactivity than TiO 2 In some examples, the light output surface 102D is GaN, AlN, AlGaN alloy, GaP, AlGaP, AlInGaP alloy, or other III-V semiconductor material surface. In some examples, the protective layer 103 includes HfO 2 , and coating 505B includes Al 2 O 3 .

[0041] In some examples (e.g., Fig. 6A ), particles 505A include luminescent particles, and particle layer 505 forms a corresponding phosphor wavelength conversion layer of a corresponding light emitting diode. Coating material 505B adheres particles 505A to each other and to light output surface 102D. This arrangement is similar to Figure 5A An arrangement in which a protective layer 103 is added between the light output surface 102D and the wavelength conversion phosphor layer 505.

[0042] In some examples (e.g., Figure 6B 50A; particles 505A may be, but need not be, luminescent particles. Coating material 505B adheres particles 505A to each other, to light output surface 102D, and to phosphor layer 106; particle layer 505 is used to adhere wavelength conversion layer 106 to protective layer 103, and thereby to LED 102. This arrangement is similar to Figure 5B arrangement in which a protective layer 103 is added between the light output surface 102D and the adhesion / particle layer 505.

[0043] In some examples (e.g., Figure 6C ), the refractive index of coating material 505B can match or approximately match the refractive index of light output surface 102D. In such an example, particle layer 505 acts as an optical coupling structure that enhances the extraction of light from LED 102 through light output surface 102D. This arrangement is similar to Figure 5CAn arrangement in which a protective layer 103 is added between the light output surface 102D and the optical coupling structure 505. Note that in some examples, the particle layer 505 can also serve as an optical coupling structure (e.g., Figure 6C as shown) and an adhesive layer (e.g., as Figure 6B shown).

[0044] Any of the LEDs 102 or arrays described above can be fabricated by first forming a protective layer 103 on the light output surface 102D, and then forming a particle layer 505 on the protective layer 103. The particle layer 505 is typically formed by first applying particles 505A to the protective layer 103, and then depositing a coating material layer 505B (e.g., FIG. 7A to FIG. 7C In Fig. 7A In the cross-sectional view of FIG. 1 , a protective layer 103 has been formed on the light output surface 102D of the semiconductor LED 102 using ALD or other suitable CVD process. Figure 7B In the embodiment, a single layer of particles 505A is deposited on the protective layer 103 using any suitable process (e.g., by sedimentation); in other examples, multiple layers of particles 505A may be deposited. Figure 7C In the embodiment, the high refractive index material 505B can be deposited, for example, by ALD, to form a conformal coating on the particles, such as Figure 7C As shown in (and described above). Figure 8 shows the HfO 2 Comparative reliability results for LEDs with protective layer 103. When operated at 85°C and 1 amp, the protected LEDs almost fully recovered after about 50 hours of operation, while the unprotected LEDs showed significant, irreversible degradation.

[0045] In some examples, protective layer 103 includes one or more metal or semiconductor oxides and may be formed using atomic layer deposition or chemical vapor deposition using one or more corresponding protective layer oxide precursors. In some examples, coating 505B includes one or more metal or semiconductor oxides and is formed using atomic layer deposition or chemical vapor deposition using one or more corresponding coating oxide precursors that are different from the one or more protective layer oxide precursors. The reactivity exhibited by the protective layer oxide precursor relative to the corresponding light output surface 102D is less than the reactivity of such oxide precursor exhibited by the one or more coating oxide precursors. In other words, the formation of protective layer 103 causes less damage to light output surface 102D than the damage that would have occurred by forming coating 505B; in some instances, the formation of protective layer 103 may not cause damage at all. The presence of protective layer 103 during deposition of coating 505B reduces or prevents damage to light output surface 102D by coating oxide precursors.

[0046] In some examples, (i) the protective layer includes HfO 2 (ii) the protective layer oxide precursor includes tetrakis(dimethylamino)hafnium (Hf(NMe 2 ) 4 )、Tetrakis(ethylmethylamino)hafnium(Hf(NMET) 4 ), or tetrakis(diethylamino)hafnium (Hf(NEt 2 ) 4 ), (iii) the coating comprises Al 2 O 3 , and (iv) a coating oxide precursor comprising trimethylaluminum (Al(CH 3 ) 3 ) or dimethylaluminum hydride (HAl(CH 3 ) 2 )

[0047] In some examples, the material selection of the protective layer 103 and the high refractive index material 505B may be limited by the reaction conditions permitted by the deposition process. In some examples, the array of LEDs 102 may be mounted on a drive or control circuit substrate (e.g., a CMOS TFT substrate) before forming the protective layer 103 and the particle layer 505. Because some or all of the electronic components on the circuit substrate cannot withstand excessive heating, in some examples, the protective layer 103 and the coating are formed at a temperature below about 150°C.

[0048] This disclosure is illustrative, and not restrictive. Further modifications will be apparent to those skilled in the art in view of this disclosure, and are intended to fall within the scope of the appended claims.

[0049] In addition to the foregoing, the following example embodiments are within the scope of the present disclosure or the appended claims.

[0050] Example 1. A device comprising: (a) one or more semiconductor light emitting diodes, each semiconductor light emitting diode having a corresponding light output surface; (b) a corresponding particle layer located above each light output surface and comprising a plurality of optically scattering or luminescent particles and a thin coating of a transparent material coating the plurality of particles, the plurality of optically scattering or luminescent particles being characterized by a D50 greater than about 0.10 μm and less than about 20 μm, the coating having a thickness less than about 0.30 μm; and (c) a corresponding transparent protective layer located between and in contact with each light output surface and the corresponding particle layer, the protective layer having a thickness less than about 0.07 μm and comprising one or more materials different from the coating material.

[0051] Example 2. The device of Example 1, wherein: (i) the material of each protective layer comprises one or more metal or semiconductor oxides, (ii) the coating comprises one or more metal or semiconductor oxides, and (iii) the material of each protective layer is characterized by one or more oxide precursor reactivity relative to the corresponding light output surface being less than the reactivity of such oxide precursor characterizing the coating material.

[0052] Example 3. A device according to any one of Examples 1 or 2, wherein (i) the material of the protective layer comprises HfO 2 、SiO 2 , Ga 2 O 3 ,GeO 2 SnO 2 CrO 2 , Nb 2 O 5 、TiO 2 、 2 O 5 、V 2 O 5 , Y 2 O 3 and ZrO 2 One or more materials selected from the group consisting of: (ii) the material of the coating comprises Al 2 O 3 , HfO 2 、SiO 2 , Ga 2 O 3 ,GeO 2 SnO 2 CrO 2 , Nb 2 O 5 、TiO 2 、 2 O 5 、V 2 O 5 , Y 2 O 3 and ZrO 2 One or more materials selected from the group consisting of: (i) each light output surface is a surface of GaN, AlN, AlGaN alloy, GaP, AlGaP or AlInGaP alloy material.

[0053] Example 4. The device according to any one of Examples 1 to 3, wherein the protective layer comprises HfO 2 , and the coating includes Al 2 O 3 .

[0054] Example 5. The device of any of Examples 1 to 4, wherein the one or more semiconductor light emitting diodes form an array of semiconductor light emitting diodes having corresponding light output surfaces, each light emitting diode (i) having a lateral dimension of less than about 1.0 mm, and (ii) being separated from adjacent light emitting diodes of the array by less than about 0.10 mm.

[0055] Example 6. The device of any of Examples 1 to 5, wherein the one or more semiconductor light emitting diodes form an array of semiconductor light emitting diodes having corresponding light output surfaces, each light emitting diode (i) having a lateral dimension of less than about 0.10 mm, and (ii) being separated from adjacent light emitting diodes of the array by less than about 0.05 mm.

[0056] Example 7. The device of any of Examples 1 to 6, wherein each light emitting diode has a combined thickness of the n-type doped layer, the active layer, and the p-type doped layer that is less than about 5 μm thick.

[0057] Example 8. The device of any of Examples 1 to 7, wherein the plurality of particles comprises luminescent particles, and each particle layer forms a respective phosphor wavelength conversion layer of a respective light emitting diode.

[0058] Example 9. The device of any of Examples 1 to 8 further comprises a respective phosphor wavelength conversion layer on and in contact with the respective particle layer, each particle layer adhering the respective wavelength conversion layer to the respective protective layer.

[0059] Example 10. The device of any of Examples 1 to 9, wherein the refractive index of the coating material matches or approximately matches the refractive index of each light output surface.

[0060] Example 11. A method for forming a device as described in any of Examples 1 to 10, the method comprising: (A) forming a corresponding transparent protective layer on a corresponding light output surface of each of one or more semiconductor light emitting diodes and in contact with each light output surface, the protective layer having a thickness of less than about 0.07 μm; and (B) forming a corresponding particle layer on the corresponding protective layer on each light output surface and in contact with the corresponding protective layer, each protective layer comprising a plurality of optically scattering or luminescent particles and a thin coating of a transparent material coating the plurality of particles, the plurality of optically scattering or luminescent particles being characterized by a D50 greater than about 0.10 μm and less than about 20 μm, the coating having a thickness of less than about 0.30 μm, the protective layer comprising one or more materials different from the coating material.

[0061] Example 12. The method of Example 11, wherein: (A') the protective layer comprises one or more metal or semiconductor oxides and is formed by atomic layer deposition or chemical vapor deposition using one or more corresponding protective layer oxide precursors; (B') the coating comprises one or more metal or semiconductor oxides and is formed by atomic layer deposition or chemical vapor deposition using one or more corresponding coating oxide precursors different from the one or more protective layer oxide precursors; and (C) the one or more protective layer oxide precursors exhibit a reactivity with respect to the corresponding light output surface that is less than the reactivity of such oxide precursor exhibited by the one or more coating oxide precursors.

[0062] Example 13. The method of Example 12, wherein the oxide precursor comprises one or more metal or semiconductor halides, amides, alkylamides, or alkoxides, or organometallic compounds.

[0063] Example 14. The method according to any one of Examples 12 or 13, wherein the one or more protective layer oxide precursors or the one or more coating precursors may include one or more of the following: Al(CH 3 ) 3 , HAl(CH 3 ) 2 、Hf(N(CH 3 ) 2 ) 4 、Hf(N(CH2CH 3 ) 2 ) 4 、TaCl 5 、Ta(N(CH 3 ) 2 ) 5 、ZrCl 4 、Zr(N(CH 3 ) 2 ) 4 、TiCl 4 、Ti(OCH 3 ) 4 、Ti(OEt) 4 、SiCl 4 , H 2 N(CH 2 ) 3 、Si(OEt) 3 、Si(OEt) 4 , tert-(butylimino)-tris(diethylamino)-niobium, or tris(ethylcyclopentadienyl)yttrium.

[0064] Example 15. The method according to any one of Examples 12 to 14, wherein (i) the protective layer comprises HfO2 (ii) the protective layer oxide precursor includes tetrakis(dimethylamino)hafnium (Hf(NMe 2 ) 4 )、Tetrakis(ethylmethylamino)hafnium(Hf(NMET) 4 ), or tetrakis(diethylamino)hafnium (Hf(NEt 2 ) 4 ), (iii) the coating comprises Al 2 O 3 , and (iv) a coating oxide precursor comprising trimethylaluminum (Al(CH 3 ) 3 ) or dimethylaluminum hydride (HAl(CH 3 ) 2 )

[0065] Example 16. The method of any one of Examples 11 to 15 further comprises adhering a corresponding phosphor wavelength conversion layer to the corresponding protective layer on each light output surface using a corresponding particle layer, the corresponding phosphor wavelength conversion layer being located on and in contact with the corresponding particle layer.

[0066] Example 17. The method of any of Examples 11 to 16, wherein each respective protective layer and coating layer is formed at a temperature below about 150°C.

[0067] It is intended that equivalents of the disclosed example embodiments and methods should fall within the scope of the present disclosure or the appended claims.It is intended that the disclosed example embodiments and methods, and their equivalents, may be modified while remaining within the scope of the present disclosure or the appended claims.

[0068] In the foregoing detailed description, various features in several example embodiments may be combined together for the purpose of streamlining the disclosure. This method of disclosure should not be interpreted as reflecting the following intention: any claimed embodiment requires more features than those explicitly listed in the corresponding claim. On the contrary, as reflected in the appended claims, the subject matter of the invention may lie in less than all the features of a single disclosed example embodiment. Therefore, the present disclosure should be interpreted as implicitly disclosing any embodiment with any suitable subset of one or more features - these features are shown, described or claimed in this application - the said any suitable subset includes those subsets that may not be explicitly disclosed herein. The "suitable" subset of features only includes features that are neither incompatible nor mutually exclusive with respect to any other features of the subset. Therefore, the appended claims are hereby incorporated into the detailed description as a whole, wherein each claim itself is a separately disclosed embodiment. In addition, each of the appended dependent claims should be interpreted - only for the purpose of disclosure by the said incorporation of the claim into the detailed description - as if written in multiple dependent forms and subordinate to all the preceding claims that do not contradict it. It should also be noted that the cumulative scope of the appended claims may but does not necessarily cover all the subject matter disclosed in this application.

[0069] The following interpretations shall apply to the present disclosure and the appended claims. Unless expressly stated otherwise, the words "include", "comprising", "having" and their variations, wherever they appear, shall be understood as open terms, with the same meaning as if a phrase such as "at least" were appended after each instance thereof. The article "a" shall be interpreted as "one or more", unless "only one", "single" or other similar limitations are expressly stated or implied in a particular context; similarly, the article "the" shall be interpreted as "one or more of...", unless "only one of...", "single of..." or other similar limitations are expressly stated or implied in a particular context. The conjunction "or" shall be interpreted as inclusive, unless: (i) it is otherwise expressly stated, for example, by using "or...or...", "only one of..." or similar language; or (ii) two or more of the listed alternatives are understood or disclosed (implicitly or explicitly) as being incompatible or mutually exclusive in a particular context. In the latter case, "or" will be understood to cover only those combinations involving non-mutually exclusive alternatives. In one example, each of "dog or cat", "one or more of dogs or cats", and "one or more dogs or cats" will be interpreted as one or more dogs without any cats, or one or more cats without any dogs, or one or more of each. In another example, each of "dog, cat or mouse", "one or more of dogs, cats or mice", and "one or more dogs, cats or mice" will be interpreted as (i) one or more dogs without any cats or mice, (ii) one or more cats without any dogs or mice, (iii) one or more mice without any dogs or cats, (iv) one or more dogs and one or more cats without any mice, (v) one or more dogs and one or more mice without any cats, (vi) one or more cats and one or more mice without any dogs, or (vii) one or more dogs, one or more cats, and one or more mice. In another example, each of “two or more of dogs, cats, or mice” or “two or more dogs, cats, or mice” would be interpreted as (i) one or more dogs and one or more cats without any mice, (ii) one or more dogs and one or more mice without any cats, (iii) one or more cats and one or more mice without any dogs, or (iv) one or more dogs, one or more cats, and one or more mice; “three or more,” “four or more,” etc. would be similarly interpreted.

[0070] For purposes of this disclosure or the appended claims, when terminology is employed in connection with numerical quantities, such as "approximately equal to," "substantially equal to," "greater than about," "less than about," and the like, standard conventions regarding measurement precision and significant figures shall apply unless a different interpretation is expressly stated. With respect to zero quantities described by phrases such as "substantially prevented," "substantially absent," "substantially eliminated," "approximately equal to zero," "negligible," and the like, each such phrase shall mean a case in which the quantity in question has been reduced or minimized to such an extent that, in the context of the intended operation or use of the disclosed or claimed apparatus or method, the overall behavior or performance of the apparatus or method, for practical purposes, is indistinguishable from that which would have occurred if the zero quantity had been substantially completely removed, was exactly equal to zero, or was otherwise exactly zero.

[0071] For purposes of this disclosure and the appended claims, any labeling of elements, steps, limitations, or other parts of embodiments, examples, or claims (e.g., first, second, third, etc., (a), (b), (c), etc., or (i), (ii), (iii), etc.) is for clarity purposes only and should not be interpreted as implying any kind of ordering or priority of the parts so labeled. If any such ordering or priority is intended, it will be explicitly listed in the embodiments, examples, or claims, or in some instances, it will be implicit or inherent based on the specific content of the embodiments, examples, or claims. In the appended claims, if it is intended to invoke the provisions of 35 USC § 112(f) in a device claim, then the word "means" will appear in the device claim. If it is intended to invoke those provisions in a method claim, then the words "step for..." will appear in the method claim. Conversely, if the words "means" or "step for..." do not appear in a claim, then the provisions of 35 USC § 112(f) are not intended to be invoked for use in that claim.

[0072] If any one or more disclosures are incorporated herein by reference, and such incorporated disclosures conflict with the present disclosure in part or in whole, or differ in scope from the present disclosure, then to the extent of the conflict, the broader disclosure, or the broader definition of terms, the present disclosure shall prevail. If such incorporated disclosures conflict with each other in part or in whole, then to the extent of the conflict, the disclosure of the later date shall prevail.

[0073] An abstract is provided as needed to aid those searching for a specific subject matter within the patent document. However, the abstract is not intended to imply that any particular claim necessarily covers any element, feature, or limitation listed therein. The scope of the subject matter covered by each claim should be determined solely by the listing of that claim.

Claims

1. A device comprising: (a) one or more semiconductor light emitting diodes, each semiconductor light emitting diode having a respective light output surface, (b) a respective particle layer located above each light output surface and comprising a plurality of optically scattering or luminescent particles and a thin coating of a transparent material coating the plurality of particles, the plurality of optically scattering or luminescent particles being characterized by a D50 greater than 0.10 μm and less than 20 μm, the coating having a thickness less than 0.30 μm, and (c) a respective transparent protective layer located between and in contact with each light output surface and the respective particle layer, the protective layer having a thickness of less than 0.05 μm and comprising one or more materials different from the coating material; wherein: (i) the material of each protective layer comprises one or more metal or semiconductor oxides, (ii) the coating comprises one or more metal or semiconductor oxides, and (iii) the material of each protective layer is characterized in that the reactivity of one or more oxide precursors relative to the corresponding light output surface is less than the reactivity of such oxide precursors characterizing the coating material.

2. The device according to claim 1, wherein: (i) the material of the protective layer includes one or more materials selected from the group consisting of HfO2, SiO2, Ga2O3, GeO2, SnO2, CrO2, Nb2O5, TiO2, Ta2O5, V2O5, Y2O3 and ZrO2, (ii) the material of the coating includes one or more materials selected from the group consisting of Al2O3, HfO2, SiO2, Ga2O3, GeO2, SnO2, CrO2, Nb2O5, TiO2, Ta2O5, V2O5, Y2O3 and ZrO2, and (iii) each light output surface is a surface of GaN, AlN, AlGaN alloy, GaP, AlGaP, or AlInGaP alloy material.

3. The device of claim 2, wherein the protective layer comprises HfO2 and the coating comprises Al2O3.

4. The device of claim 1 , wherein the one or more semiconductor light emitting diodes form a semiconductor light emitting diode array having corresponding light output surfaces, each light emitting diode (i) having a lateral dimension less than 1.0 mm and (ii) being separated from adjacent light emitting diodes in the array by less than 0.10 mm.

5. The device of claim 1, wherein each light emitting diode has a combined thickness of the n-type doped layer, the active layer, and the p-type doped layer that is less than 5 μm thick.

6. The device of claim 1, wherein the plurality of particles comprises luminescent particles and each particle layer forms a respective phosphor wavelength conversion layer of a respective light emitting diode.

7. The device of claim 1, further comprising a respective phosphor wavelength converting layer on and in contact with the respective particle layer, each particle layer adhering the respective wavelength converting layer to the respective protective layer.

8. The device of claim 1, wherein the coating material has an index of refraction that matches or nearly matches the index of refraction of each light output surface.

9. A method comprising: (A) forming a corresponding transparent protective layer on a corresponding light output surface of each of the one or more semiconductor light emitting diodes in contact with each light output surface, the protective layer having a thickness of less than 0.05 μm, and (B) forming a respective particle layer on and in contact with the respective protective layer on the respective protective layer on each light output surface, each particle layer comprising a plurality of optically scattering or luminescent particles and a thin coating of a transparent material coating the plurality of particles, the plurality of optically scattering or luminescent particles being characterized by a D50 greater than 0.10 μm and less than 20 μm, the coating having a thickness less than 0.30 μm, the protective layer comprising one or more materials different from the coating material; in: (A') the protective layer comprises one or more metal or semiconductor oxides and is formed by atomic layer deposition or chemical vapor deposition using one or more corresponding protective layer oxide precursors, (B') the coating comprises one or more metal or semiconductor oxides and is formed by atomic layer deposition or chemical vapor deposition using one or more corresponding coating oxide precursors different from the one or more protective layer oxide precursors, and (C) the one or more protective layer oxide precursors exhibit a reactivity relative to the corresponding light output surface that is less than the reactivity of such oxide precursor exhibited by the one or more coating oxide precursors.

10. The method of claim 9, wherein the oxide precursor comprises one or more metal or semiconductor halides, amides, alkylamides, or alkoxides, or organometallic compounds.

11. The method of claim 9, wherein (i) the material of the protective layer comprises one or more materials selected from the group consisting of HfO2, SiO2, Ga2O3, GeO2, SnO2, CrO2, Nb2O5, TiO2, Ta2O5, V2O5, Y2O3 and ZrO2, (ii) the material of the coating comprises one or more materials selected from the group consisting of Al2O3, HfO2, SiO2, Ga2O3, GeO2, SnO2, CrO2, Nb2O5, TiO2, Ta2O5, V2O5, Y2O3 and ZrO2, and (iii) each light output surface is a GaN, AlN, AlGaN alloy, GaP, AlGaP, or AlInGaP alloy material surface.

12. The method of claim 11, wherein (i) the protective layer comprises HfO2, (ii) the protective layer oxide precursor comprises one or more of tetrakis(dimethylamino)hafnium (Hf(NMe2)4), tetrakis(ethylmethylamino)hafnium (Hf(NMET)4), or tetrakis(diethylamino)hafnium (Hf(NEt2)4), (iii) the coating comprises Al2O3, and (iv) the coating oxide precursor comprises one or more of trimethylaluminum (Al(CH3)3) or dimethylaluminum hydride (HAl(CH3)2).

13. The method of claim 9, wherein the one or more semiconductor light emitting diodes form a semiconductor light emitting diode array having corresponding light output surfaces, each light emitting diode (i) having a lateral dimension less than 1.0 mm and (ii) being separated from adjacent light emitting diodes in the array by less than 0.10 mm.

14. The method of claim 9, wherein each light emitting diode has a combined thickness of the n-type doped layer, the active layer, and the p-type doped layer that is less than 5 μm thick.

15. The method of claim 9, wherein the plurality of particles comprises luminescent particles and each particle layer forms a respective phosphor wavelength conversion layer of a respective light emitting diode.

16. The method of claim 9, further comprising adhering a corresponding phosphor wavelength conversion layer to the corresponding protective layer on each light output surface using a corresponding particle layer, wherein the corresponding phosphor wavelength conversion layer is located on and in contact with the corresponding particle layer.

17. The method of claim 9, wherein the coating material has an index of refraction that matches or nearly matches the index of refraction of each light output surface.

18. The method of claim 9, wherein each respective protective layer and coating layer is formed at a temperature below 150°C.

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