KR20210052514A - Phosphor conversion LED with high color quality - Google Patents

Abstract

A light emitting diode (LED) device can include an LED die having a first surface on a substrate. A first phosphor layer may be formed on the second surface and sides of the LED die. The second surface can be opposite the first surface. A second phosphor layer may be formed on the first phosphor layer. A second phosphor layer may have a peak emission wavelength (L _pk 2) positioned between the peak emission wavelength (L _pk D) and the first phosphor layer in the emission peak wavelength (L _pk 1) LED die.

Description

Phosphor conversion LED with high color quality

Cross reference to related applications

This application claims the benefit of priority to European Patent Application No. 18201516.4 filed Oct. 19, 2018 and U.S. Patent Application No. 16/119,688 filed Aug. 31, 2018, each of which is in its entirety. Is incorporated herein by reference.

Phosphor converted white LED light emitting diode (LED) devices typically use a blue LED covered with a layer of luminescent materials that partially absorbs blue LED light and emits green, yellow, and red light. The luminescent materials typically include a mixed powder of inorganic materials. In the case of high color quality defined by Commission on Illumination (CIE) as a color rendering index (CRI), the spectral power distribution (SPD) of the light emitted from the LED must closely follow the SPD of the white reference light. do. When the light emitted from the LED is used in combination with camera systems (eg, as a flash), it can be particularly important to avoid sharp peaks and minimums in the SPD.

A light emitting diode (LED) device can include an LED die having a first surface on a substrate. A first phosphor layer may be formed on the second surface and sides of the LED die. The second surface can be opposite the first surface. A second phosphor layer may be formed on the first phosphor layer. A second phosphor layer may have a peak emission wavelength (L _pk 2) positioned between the peak emission wavelength (L _pk D) and the first phosphor layer in the emission peak wavelength (L _pk 1) LED die.

A light emitting diode (LED) device can include an LED die having a first surface on a substrate. A first phosphor layer may be formed on the second surface of the LED die. The second surface can be opposite the first surface. A second phosphor layer may be formed on the first phosphor layer. A second phosphor layer may have a peak emission wavelength (L _pk 2) positioned between the peak emission wavelength (L _pk D) and the first phosphor layer in the emission peak wavelength (L _pk 1) LED die. A reflective coating may be formed on the sides of the LED die, the sides of the first phosphor layer, and the sides of the second phosphor layer.

A more detailed understanding can be obtained from the following description given by way of example in conjunction with the accompanying drawings, in which like reference numbers in the drawings indicate like elements, wherein:
1 is a cross-sectional view illustrating an LED die on a substrate;
2 is a cross-sectional view illustrating forming a first phosphor layer on an LED;
3 is a cross-sectional view illustrating forming a second phosphor layer on the first phosphor layer to form an LED device;
4 is a cross-sectional view illustrating selectively forming a lens around an LED device;
5 is a cross-sectional view illustrating selectively removing portions of a first phosphor layer and a second phosphor layer from an LED device;
6 is a cross-sectional view illustrating forming a reflective coating on the sides of the LED die, the remaining portion of the first phosphor layer, and the remaining portion of the second phosphor layer to form an LED device;
7 is a cross-sectional view illustrating selectively forming a lens around an LED device;
8 is a chart illustrating emission spectra comparing an LED die coated with only a first phosphor layer and an LED die coated with both a first phosphor layer and a second phosphor layer;
9 is a chart illustrating the emission spectra of a second phosphor layer and an LED die.

Examples of different light emitting diode ("LED") implementations will be described more fully below with reference to the accompanying drawings. These examples are not mutually exclusive, and features found in one example may be combined with features found in one or more other examples to achieve additional implementations. Accordingly, it will be understood that the examples shown in the accompanying drawings are provided for illustrative purposes only, and they are not intended to limit the present disclosure in any way. The same numbers refer to the same elements throughout.

Although terms such as first, second, etc. may be used to describe various elements herein, it will be understood that these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

When an element such as a layer, region or substrate is referred to as being “on” or extending “on” another element, it may be directly on the other element or may extend directly onto the other element, or an intervening element It will be understood that) can also exist. Conversely, when an element is referred to as being “directly on” or extending “directly onto” another element, the intervening elements are absent. It will also be appreciated that when an element is referred to as being “connected” or “coupled” to another element, one element may be directly connected or coupled to another element, or intervening elements may be present. Conversely, when one element is referred to as being “directly connected” or “directly coupled” to another element, the intermediate elements are absent. It will be understood that these terms are intended to encompass different orientations of an element other than any orientation shown in the figures.

Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" are used in the drawings. As shown, it may be used herein to describe the relationship between one element, layer, or region and another element, layer, or region. It will be understood that these terms are intended to encompass different orientations of the device other than the orientation shown in the figures.

As described above, in the case of high color quality defined by Commission on Illumination (CIE) as a color rendering index (CRI), the spectral power distribution (SPD) of light emitted from the LED must closely follow the SPD of the white reference light. In order to realize a high CRI, different phosphor materials may have to be applied to emit light of different wavelengths. Emissions from phosphors emitting at shorter wavelengths can be absorbed by phosphors emitting at longer wavelengths. This phosphor-phosphor interaction can reduce efficiency due to photon losses in the conversion processes. The phosphor-phosphor interaction can also increase absorption losses in an LED package comprising one or more LED dies due to redirection of the emitted light back to one or more LED dies.

In some applications, it may be desirable to reduce the local minimum in the SPD adjacent to the blue emission peak of the LED. The emission peak of the phosphor component may have to be close to that of the blue LED. When a phosphor material absorbs photons, it gains energy and enters an excited state. One way a phosphor material relaxes is to lose energy by emitting photons (another way is to lose energy as heat). When the emitted photon has less energy than the absorbed photon, this energy difference is a Stokes shift. Stokes fluorescence is the emission of longer wavelength photons (lower frequency or energy) by molecules that absorb photons of shorter wavelength (higher frequency or energy). That is, the Stokes shift may be the distance between the maximum absorption wavelength and the maximum emission wavelength. Due to the Stokes shift, a large concentration of phosphor material may be required. The reabsorption of the emitted light by other phosphors may need to be reduced as much as possible.

The following description describes systems, methods, and devices for using multiple phosphor layers formed on an LED to reduce the reabsorption of light emitted by the outermost phosphor layer and increase the efficiency of the LED at high CRI. Includes. By using a second phosphor layer having an emission peak positioned between the emission peak of the first phosphor layer and the emission peak of the LED, the wavelength gap between the LED emissions and the emission of the first phosphor layer can be effectively filled.

Referring now to FIG. 1, a cross-sectional view illustrating an LED die 104 on a substrate 104 is shown. The first surface of the LED die 104 may be located on the substrate 102 and the second surface of the LED die may be located opposite the first surface. The LED die 104 may be any type of conventional semiconductor light emitting device and may be formed, attached, or grown on the substrate 102. 1 shows an illustrative example of the type of LED die 104 that may be used and is not intended to limit the description below. The LED die 104 may be a type Ill-nitride LED known in the art. Typically, III-nitride LEDs are sapphire, silicon carbide, III by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. -Prepared by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a nitride, or other suitable substrate. The stack is often formed over a substrate, e.g., one or more n-type layers doped with silicon, one or more light emitting layers in an active region (e.g., a pn diode) formed over an n-type layer or layers, and over the active region And one or more p-type layers formed, for example doped with magnesium. Electrical contacts are formed on the n-type and p-type regions.

In the examples below, the LED die 104 can emit blue or UV light. However, semiconductor light emitting devices other than LEDs such as laser diodes, and other materials such as Ill-V materials, Ill-prints, Ill-arsenides, II-VI materials, ZnO, or Si-based materials Semiconductor light emitting devices made from systems can be used.

The device of FIG. 1 may be formed by growing a type III-nitride semiconductor structure on a substrate 102 as known in the art. Substrate 102 may be sapphire or any suitable substrate such as, for example, SiC, Si, GaN, or a composite substrate. The surface of the substrate 102 on which the type III-nitride semiconductor structure is grown may be patterned, roughened, or textured prior to growth, which may improve light extraction from the device. The surface of the substrate 102 opposite the growth surface (i.e., the surface through which most of the light is extracted in a flip chip configuration) can be patterned, roughened, or textured before or after growth, which is from the device. It can improve the light extraction of.

The semiconductor structure includes a light emitting or active region sandwiched between an n-type region and a p-type region. The n-type region 16 may be grown first and may contain multiple layers of different composition and dopant concentration. The n-type region 16 is designed to facilitate removal of preparation layers, such as buffer layers or nucleation layers, and/or n-type or growth substrates that may not be intentionally doped, and the light emitting region efficiently It may include n-type or even p-type device layers designed for specific optical, material, or electrical properties desirable to emit light. A light emitting or active region 18 is grown over the n-type region 16. Examples of suitable light emitting regions 18 include a single thick or thin light emitting layer, or multiple quantum well light emitting regions comprising multiple thin or thick light emitting layers separated by barrier layers. do. Next, the p-type region 20 may be grown on the light emitting region. Like the n-type region, the p-type region can include multiple layers of different composition, thickness, and dopant concentration, including intentionally undoped layers or n-type layers.

After growth, a p-contact may be formed on the surface of the p-type region 18. The p-contact 21 may include a reflective metal and a plurality of conductive layers such as a guard metal that may prevent or reduce electromigration of the reflective metal. The reflective metal is often silver, but any suitable material or materials can be used. The p-contact 21, the p-type region 20, and a portion of the active region 18 may be removed to expose a portion of the n-type region 16 in which the n-contact 22 is formed. . The n-contact 22 and p-contact 21 may be electrically isolated from each other by a gap 25 that may be filled with a dielectric such as an oxide of silicon or any other suitable material. Multiple n-contact vias can be formed. The n-contact 22 and the p-contact 21 are not limited to the arrangement shown in FIG. 1. The n-contacts 22 and p-contacts 21 can be redistributed to form bond pads having a dielectric/metal stack as known in the art.

To make electrical connections to the LED die 104, one or more interconnects 26 and 28 may be formed or electrically connected on the n-contacts 22 and p-contacts 21. Interconnect 26 may be electrically connected to n-contact 22. Interconnect 28 may be electrically connected to p-contact 21. Interconnects 26 and 28 may be electrically isolated from n-contact 22 and p-contact 21 and from each other by dielectric layer 24 and gap 27. Interconnects 26 and 28 may be, for example, solder, stud bump, gold layer, or any other suitable structure. The semiconductor structure, n-contact 22, p-contact 21, and interconnects 26 and 28 are shown as LED structure 104 in the following figures. The substrate 102 may be thinned or completely removed. The surface of the substrate 102 exposed by the thinning is patterned, textured, or roughened to improve light extraction.

Turning now to FIG. 2, a cross-sectional view is shown illustrating forming the first phosphor layer 202 on the LED die 104. The first phosphor layer 202 may be applied to the second surface and sides of the LED die 104. The first phosphor layer 202 may have a thickness ranging from approximately 1 μm to approximately 150 μm.

The first phosphor layer 202 can be formed using a conventional deposition process. In one example, the first phosphor layer 202 may be a sheet disposed on top of the LED die 104 and then processed to conform to the shape of the LED die 104. A combination of vacuum and heat can be used to laminate the first phosphor layer 202 to the LED die 104.

One of ordinary skill in the art will recognize that the first phosphor layer 202 need not be in the form of a laminate sheet; It can be applied in liquid or paste form through spray coating, molding, screen printing, or the like. For example, the first phosphor layer 202 is CVD (chemical vapor deposition), PECVD (plasma-enhanced CVD), ALD (atomic layer deposition), evaporation (evaporation), sputtering, chemical solution deposition (chemical solution deposition), It may be conformally formed on the LED die 104 using a conventional deposition process such as spin-on deposition, or other similar processes.

The first phosphor layer 202 is, for example, conventional phosphors, organic phosphors, quantum dots, organic semiconductors, II-VI or Ill-V semiconductors, II-VI or Ill-V It may include a wavelength converting material, which may be semiconductor quantum dots or nanocrystals, dyes, polymers, or other materials that emit light. The first phosphor layer 202 may comprise a transparent material such as silicon mixed with a wavelength converting material.

The wavelength converting material can absorb light emitted by the LED die 104 and can emit one or more different wavelengths of light. The unconverted light emitted by the LED die 104 may be part of the final spectrum of light extracted from the structure, but need not.

In one example, LED die 104 may be a blue-emitting LED with a peak emission wavelength of _{L pk D.}

In one example, the first phosphor layer 202 may comprise a yellow-emission wavelength converting material, a green-emission wavelength converting material, and a red-emission wavelength converting material having a combined peak emission wavelength _{of L pk 1.}

The first phosphor layer 202 may comprise one or more phosphor powders in silicon. For example, the first phosphor layer 202 may include GaLuAG, SCASN, and CASN. The mass ratio of the materials in the first phosphor layer 202 may be approximately 20% SCASN: 80% CASN. The ratio of GaLuAG to total red mass in the first phosphor layer 202 may be approximately 8.47.

In another example, the first phosphor layer 202 may comprise a mixture of a green-emission wavelength converting material and a red-emission wavelength converting material. The green-emission wavelength converting material may include cerium-activated garnets having a chemical composition _{of (Y,Gd,Lu) 3} (Al,Ga) ₅ O _{12 :Ce.} The green-emission wavelength converting material may include silicates and oxynitrides, such as SiAlON, activated with europium. The red-emission wavelength converting material may include europium activated, nitrides, such as CASN, SCASN and BSSN, and quantum dots.

In another example, the first phosphor layer 202 may comprise a mixture of green-emission wavelength converting materials and red-emission wavelength converting materials. Green-emission wavelength converting materials may include GaLuAG and GaYAG. Red-emission wavelength converting materials may include SCASN and CASN, where the mass ratio of SCASN to CASN is approximately 20:80. The ratio of the total mass of the green-emission wavelength converting materials to the total mass of the red-emission wavelength converting materials is approximately 8.47 and may range from 5 to 10.

Referring now to FIG. 3, a cross-sectional view is shown illustrating forming a second phosphor layer 302 on a first phosphor layer 202 to form an LED device 300. The second phosphor layer 302 may be applied to the top and sides of the first phosphor layer 202. The second phosphor layer 302 can be formed using any of the techniques described above with reference to the formation of the first phosphor layer 202. The second phosphor layer 302 may have a thickness in the range of approximately 10 μm to approximately 150 μm.

The second phosphor layer 302 is, for example, conventional phosphors, organic phosphors, quantum dots, organic semiconductors, II-VI or Ill-V semiconductors, II-VI or Ill-V It may include a wavelength converting material, which may be semiconductor quantum dots or nanocrystals, dyes, polymers, or other materials that emit light. The second phosphor layer 302 may comprise a transparent material such as silicon mixed with a wavelength converting material.

The wavelength converting material may absorb light emitted by the LED die 104 and/or the first phosphor layer 202 and may emit light of one or more different wavelengths. The unconverted light emitted by the LED die 104 and/or the first phosphor layer 202 may be part of the final spectrum of light extracted from the structure, but need not.

The second phosphor layer 302 may comprise one or more phosphor materials having a peak emission wavelength L _{pk 2 between L pk} D and L _pk 1 (i.e., L _pk D <L _pk 2 <L _{pk 1 ).} . In one example, the peak emission wavelength L _pk 2 may be approximately 100 nm larger than _{L pk D and approximately 100 nm smaller than L pk} 1 (i.e., L _pk D + 100 nm <L _pk 2 <L _{pk 1-100} nm). . In another example, the peak emission wavelength L _pk 2 may be approximately 50 nm larger than _{L pk D and approximately 50 nm smaller than L pk} 1 (i.e., L _pk D + 50 nm <L _pk 2 <L _{pk 1-50} nm). .

In another example, the peak emission wavelength L _pk 2 may be approximately 10 nm larger than _{L pk D and approximately 10 nm smaller than L pk} 1 (i.e., L _pk D + 10 nm <L _pk 2 <L _pk 1-10 nm). . This range of L _pk 2 is desirable when the first phosphor layer 202 comprises a mixture of a green-emission wavelength converting material (green) and a red-emission wavelength converting material (red) with a green: red mass ratio ≥1. can do.

In another example, the peak emission wavelength of the second phosphor layer is approximately 460 nm. The peak emission wavelength of the second phosphor layer may be approximately 10 nm, 20 nm, 30 nm, or 40 nm greater than _{L pk D.} The peak emission wavelength of the second phosphor layer may be approximately 10-20 nm longer than _{L pk D.} In another embodiment, L _pk 2 may be approximately 10-30 nm longer than _{L pk D.} In another embodiment, L _pk 2 may be approximately 20-40 nm longer than _{L pk D.} Preferably, L _pk 2 is within 440 nm to 490 nm, more preferably within 450 nm to 470 nm, and most preferably within 455 nm to 465 nm.

The second phosphor layer 302 may include Sr ₃ MgSi ₂ O ₈ :Eu powder in silicon. The mass phosphor of the second phosphor layer 302 relative to the mass silicon may be equal to one.

Referring now to FIG. 4, a cross-sectional view is shown illustrating selectively forming a lens 402 around an LED device 300. The lens 402 may contact the substrate 102 and the second phosphor layer 302. Lens 402 may extend laterally beyond LED device 300. Lens 402 may comprise a transparent material to improve extraction of light from LED device 300. Lens 402 may be formed using conventional deposition techniques. The lens 402 may include one or more of PMMA, polycarbonate, silicone, and HRPC. One or more portions of the lens may be aluminum coated.

Referring now to FIG. 5, a cross-sectional view illustrating selectively removing portions of the first phosphor layer 202 and the second phosphor layer 302 from the LED device 300 shown in FIG. 3 is shown.

Portions of the first phosphor layer 202 and the second phosphor layer 302 may be removed using a conventional etching or blasting process. For example, portions of the first phosphor layer 202 and the second phosphor layer 302 may be removed using reactive ion etching (RIE), plasma etching, or a selective etching process.

The remainder of the first phosphor layer 202 may have sidewalls 504 that are substantially flush with the sidewalls 502 of the LED die 104. The remainder of the second phosphor layer 302 may have sidewalls 506 that are substantially flush with the sidewalls 502 of the LED die 104.

Referring now to FIG. 6, reflection on the sides of the LED die 104, the remaining portion of the first phosphor layer 202, and the remaining portion of the second phosphor layer 302 to form the LED device 600. A cross-sectional view illustrating forming the coating 602 is shown.

The reflective coating 602 can be formed using a conventional deposition process. In one example, the reflective coating 602 is disposed on the sides of the LED die 104 and the remaining portions of the first phosphor layer 202 and the second phosphor layer 302 and then the LED die 104 and the first It may be a sheet that is treated to adhere to the remaining portions of the phosphor layer 202 and the second phosphor layer 302. A combination of vacuum and heat can be used to laminate the reflective coating 602 to the LED die 104 and the remaining portions of the first phosphor layer 202 and the second phosphor layer 302.

One of ordinary skill in the art will recognize that the reflective coating 602 need not be in the form of a laminate sheet; It can be applied in liquid or paste form through spray coating, molding, screen printing, or the like. For example, the first reflective coating 602 can be applied to the LED die 104 using a conventional deposition process such as CVD, PECVD, ALD, evaporation, sputtering, chemical solution deposition, spin-on deposition, or other similar processes. It may be formed on the substrate 102 adjacent to.

The reflective coating 602 may include a metal such as Ti, Au, or Ag. In one example, the reflective coating 602 may include TiO ₂ powder in a silicon matrix.

The reflective coating 602 may have a top surface that is substantially flush with the top surface of the remaining portion of the second phosphor layer 302.

Referring now to FIG. 7, a cross-sectional view is shown illustrating selectively forming a lens 702 around an LED device 600. Lens 702 may contact substrate 102, reflective coating 602, and second phosphor layer 302. Lens 702 may extend laterally beyond LED device 600. Lens 702 may comprise a transparent material to improve extraction of light from LED device 600. Lens 702 can be formed using conventional deposition techniques. The lens 702 may include one or more of PMMA, polycarbonate, silicone, and HRPC. One or more portions of the lens may be aluminum coated.

Referring now to FIG. 8, a first emission spectrum 802 of an LED die 104 coated with only the first phosphor layer 202 and coated with both the first phosphor layer 202 and the second phosphor layer 302. A chart illustrating the second emission spectrum 804 of the LED die 104 is shown. The first emission spectrum 802 and the second emission spectrum 804 may represent the same LED wavelength and the same color coordinates.

The first emission spectrum 802 and the second emission spectrum 804 may be normalized to the blue LED die 104 emission. As can be seen, the LED die 104 in combination with the first phosphor layer 202 and the LED die 104 in combination with both the first phosphor layer 202 and the second phosphor layer 302 are both Emits light with spectral peaks between blue light (450-490 nm) and red light (635-700 nm). The first phosphor layer 202 used to generate the first emission spectrum 802 and the first phosphor layer 202 used to generate the second emission spectrum 804 may be composed of the same phosphor materials. It should be noted that there is. However, the specific phosphor concentrations of each first phosphor layer 202 can be varied to produce the same color point. It should also be noted that the application of the second phosphor layer 302 may alter the emission of the first phosphor layer 202 due to the reflection of light that may be absorbed and converted by the first phosphor layer 202.

The local minimum of the SPD along the blue emission peak of the LED die 104 at approximately 470 nm with two phosphor layers can be increased compared to the case with only the first phosphor layer 202. This can be seen in Table 1 below.

The color rendering index CRI(Ra) for the SPD of the LED die 104 with two phosphor layers is a CRI of 94.2 compared to the CRI(Ra) of 91.4 for the LED die 104 with only the first phosphor layer 202 Ra). The local minimum of the SPD along the blue emission peak of the LED die 104 with two phosphor layers is 48% of the LED peak compared to 38.2% of the LED peak height of the LED die 104 with only the first phosphor layer 202. Can be increased to

Referring now to FIG. 9, a chart illustrating the emission spectra of the second phosphor layer 302 and the LED die 104 is shown. As described above, the second phosphor layer 302 is an LED die 104 in the L _pk D and the first phosphor layer 202 of the L _pk peak emission wavelength between 1 L _pk 2 (i.e., L _pk D < L _pk 2 <L _pk 1). This chart shows an example where L _pk 2 is approximately 460 _{nm or L pk} D + 20 nm. L _pk 2 can also be approximately L _pk D + 10 nm.

While features and elements have been described in specific combinations above, one of ordinary skill in the art will understand that each feature or element may be used alone or in any combination with other features and elements. In addition, the methods described herein may be implemented as a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include read only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks. And removable disks, magnetic optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs).

Claims (20)

As a light emitting diode (LED) device,
An LED die configured to emit blue or UV light having a peak emission wavelength;
A first phosphor layer disposed on the LED die and configured to emit green, yellow, and red light; And
A second phosphor layer disposed on the first phosphor layer and configured to emit light having a peak emission wavelength of approximately 10 to 50 nanometers from the peak emission wavelength of the LED die
Containing, LED device. The LED device of claim 1, wherein the peak emission wavelength of the LED die is approximately 440 nanometers. The LED device of claim 1, wherein the peak emission wavelength of the second phosphor is approximately 10 nanometers longer than the peak emission wavelength of the LED die. The LED device of claim 1, wherein the peak emission wavelength of the second phosphor is approximately 10 nanometers to 20 nanometers longer than the peak emission wavelength of the LED die. The LED device of claim 1, wherein the peak emission wavelength of the second phosphor is approximately 20 nanometers to 40 nanometers longer than the peak emission wavelength of the LED die. The LED device of claim 1, wherein the peak emission wavelength of the second phosphor layer is approximately 460 nanometers. The method of claim 1,
The LED device further comprising a lens surrounding the LED die, the first phosphor layer, and the second phosphor layer. The LED device of claim 1, wherein the first phosphor layer is comprised of GaLuAG, GaYAG, SCASN, and CASN in silicon. The LED device of claim 8, wherein the mass ratio of SCASN to CASN is approximately 20:80. 9. The LED device of claim 8, wherein the ratio of total green mass to total red mass is approximately 8.47. The LED device of claim 8, wherein the ratio of the total green mass to the total red mass is greater than 5 and less than 10. The LED device of claim 1, wherein the second phosphor layer is comprised of Sr ₃ MgSi ₂ O ₈ :Eu in silicon. The method of claim 1,
The LED die having a first surface in contact with the first phosphor layer; The first phosphor layer having a second surface in contact with the second phosphor layer, the second surface facing the first surface; And
A reflective coating formed on side surfaces of the LED die, side surfaces of the first phosphor layer, and side surfaces of the second phosphor layer
Further comprising, the LED device. 14. The LED device of claim 13, wherein the reflective coating comprises TiO _{2 in silicon.} The LED device of claim 1, wherein the spectral power distribution (SPD) of the LED device comprises a local minimum at approximately 470 nanometers. The LED device of claim 15, wherein the SPD emission of the LED device at approximately 470 nanometers is increased compared to the SPD emission of the LED device without the second phosphor layer. As a light emitting diode (LED) device,
An LED die configured to emit blue or UV light;
A first phosphor layer disposed on the LED die and configured to emit green, yellow, and red light; And
A second phosphor layer disposed on the first phosphor layer and configured to emit light having a peak emission wavelength greater than 440 nanometers and less than 490 nanometers
Containing, LED device. 18. The LED device of claim 17, wherein the peak emission wavelength of the second phosphor layer is greater than 450 nanometers and less than 470 nanometers. 18. The LED device of claim 17, wherein the peak emission wavelength of the second phosphor layer is greater than 455 nanometers and less than 465 nanometers. 18. The LED device of claim 17, wherein the peak emission wavelength of the second phosphor layer is approximately 460 nanometers.

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