SOLID-STATE TRANSDUCER ASSEMBLIES WITH REMOTE CONVERTER MATERIAL FOR IMPROVED LIGHT EXTRACTION EFFICIENCY AND ASSOCIATED SYSTEMS AND METHODS
Solid state transducer (“SST”) assemblies with remote converter material and improved light extraction efficiency and associated systems and methods are disclosed herein. In one embodiment, an SST assembly has a front side from which emissions exit the SST assembly and a back side opposite the front side. The SST assembly can include a support substrate having a forward-facing surface directed generally toward the front side of the SST assembly and an SST structure carried by the support substrate. The SST structure can be configured to generate SST emissions. The SST assembly can further include a converter material spaced apart from the SST structure. The forward-facing surface and the converter material can be configured such that at least a portion of the SST emissions that exit the SST assembly at the front side do not pass completely through the converter material.
This application is a divisional of U.S. patent application Ser. No. 13/464,687, filed May 4, 2012, which is incorporated herein by reference in its entirety.
TECHNICAL FIELDThe disclosed embodiments relate to solid-state transducer (“SST”) devices and methods of manufacturing SST devices. In particular, the present technology relates to SST assemblies with remote converter material for improved light extraction efficiency and associated systems and methods.
BACKGROUNDMobile phones, personal digital assistants (“PDAs”), digital cameras, MP3 players, and other portable electronic devices utilize light-emitting diodes (“LEDs”), organic light-emitting diodes (“OLEDs”), polymer light-emitting diodes (“PLEDs”), and other SST devices for backlighting. SST devices are also used for signage, indoor lighting, outdoor lighting, and other types of general illumination.
The SST device 10a can be configured as a “white light” LED, which requires a mixture of wavelengths to be perceived as white by human eyes. LED structures typically only emit light at one particular wavelength (e.g., blue light), and are therefore modified to generate white light. One conventional technique for modulating the light from LED structures includes depositing a converter material (e.g., phosphor) on the LED structure. For example, as shown in
In operation, the LED structures 12 of the SST devices 10a-b emit light having a certain wavelength (e.g., blue light), and the phosphor of the overlying converter material 26 absorbs some of the emitted photons. This absorption promotes the electrons of the converter material 26 to high unstable energy levels, which causes the converter material 26 to emit longer-wavelength photons (e.g., yellow light) when the electrons ultimately relax to their original state. The combination of the emissions from the LED structure 12 and the converter material 26 is designed to appear white to human eyes when the wavelengths of the emissions are matched appropriately. The generated light can be modulated by optional optical features (e.g., encapsulants or lenses 28) positioned over the converter material 26.
In both the LED devices 10a-b shown in
To reduce the effects of the scattered light, the forward-facing surface of the LED structure 12 can be configured to have reflective properties. However, other considerations, such as current spreading, light-extraction efficiency, and electrical characteristics, may lead to sub-optimal reflectivity of the LED structure 12. To reduce reflections off of the face of the LED structure 12, the converter material 26 of the SST device 10b shown in
LED devices have also been designed to include a converter material spaced apart from an LED structure, such as the SST device 10c shown in
Specific details of several embodiments of SST devices and assemblies with remote converter material for improved light extraction efficiency and associated systems and methods are described below. The term “SST device” generally refers to solid-state devices that include a semiconductor material as the active medium to convert electrical energy into electromagnetic radiation in the visible, ultraviolet, infrared, and/or other spectra. For example, SST devices include solid-state light emitters (e.g., LEDs, laser diodes, etc.) and/or other sources of emission other than electrical filaments, plasmas, or gases. SST devices can also include solid-state devices that convert electromagnetic radiation into electricity. The term “light extraction efficiency” generally refers to a ratio of the amount of light extracted from an SST device to the total light generated in the SST device. A person skilled in the relevant art will also understand that the technology may have additional embodiments, and that the technology may be practiced without several of the details of the embodiments described below with reference to
In the embodiment illustrated in
The forward-facing surface 210 and/or the overlying converter material 206 can be shaped to redirect the emissions generally forward toward the opening 214 in a manner that inhibits multiple reflections of the SST emissions off of other surfaces within of the SST assembly 200 and to enhance light extraction from the SST assembly 200. For example, as shown in
The support substrate 202 can be made from various suitable materials for supporting one or more SST devices 204. For example, the support substrate 202 can be made from metals and/or metal alloys (e.g., copper, aluminum, aluminum nitride, etc.) that have a high thermal conductivity to function as a heat sink and thereby decrease the operating temperature of the SST assembly 200. In other embodiments, the support substrate 202 can be made from silicon, sapphire, and/or other suitable nonconductive or conductive materials.
In certain embodiments, the forward-facing surface 210 can be a highly reflective material 218 (shown in broken lines) to efficiently reflect the emissions toward the front side 208a of the SST assembly 200. The reflective material 218 can be formed on the support substrate 202 using chemical vapor deposition (“CVD”), physical vapor deposition (“PVD”), atomic layer deposition (“ALD”), plating, and/or other suitable formation techniques known in the arts. In other embodiments, the reflective material 218 can also be formed on other surfaces of the SST assembly 200 (e.g., the support surface 216), or the support substrate 202 itself can be formed from the reflective material 218. The reflective material 218 can include gold (Au), copper (Cu), silver (Ag), aluminum (Al), alloys thereof, and/or any other suitable material that reflects emissions from the SST devices 204 and/or the converter material 206. In various embodiments, the reflective material 218 can be selected based on its thermal conductivity and/or the color of light it reflects. For example, silver generally does not alter the color of the reflected light. Gold, copper, or other colored reflective materials can affect the color of the light, and can accordingly be selected to produce a desired color for the light emitted by the SST assembly 200.
Whether reflective or not, the forward-facing surface 210 can carry the converter material 206 such that the emissions (e.g., light) directed toward the back side 208b of the SST assembly 200 irradiate energized particles (e.g., electrons and/or photons) of the converter material 206. The irradiated converter material 206 can emit a light of a certain quality (e.g., color, warmth, intensity, etc.). For example, the irradiated converter material 206 can emit light having a different color (e.g., yellow light) than the light emitted by the SST devices 204 (e.g., blue light). The light emitted by the converter material 206 can combine with the light emitted by the SST devices 204 to produce a desired color of light (e.g., white light).
The converter material 206 can include a phosphor containing a doped yttrium aluminum garnet (YAG) (e.g., cerium (Ill)) at a particular concentration for emitting a range of colors (e.g., yellow to red) under photoluminescence. In other embodiments, the converter material 206 can include neodymium-doped YAG, neodymium-chromium double-doped YAG, erbium-doped YAG, ytterbium-doped YAG, neodymium-cerium double-doped YAG, holmium-chromium-thulium triple-doped YAG, thulium-doped YAG, chromium (IV)-doped YAG, dysprosium-doped YAG, samarium-doped YAG, terbium-doped YAG, and/or other suitable wavelength conversion materials. In further embodiments, the converter material 206 can include silicate phosphor, nitrate phosphor, aluminate phosphor and/or other types of salt or ester based phosphors.
In the embodiment illustrated in
As discussed above, the remotely-positioned converter material 206 is not in direct contact with the SST devices 204, nor do all of the emissions from the SST devices 204 penetrate into or otherwise pass completely through the converter material 206. The converter material 206 therefore experiences less heating from the SST devices 204, which allows for the use of alternative converter materials that may be sensitive to the operating temperatures induced by conventional SST devices. For example, the SST assembly 200 can include organic converter materials, high refractive index silicone, and/or other suitable converter materials that may have heat-sensitive properties. The lower temperatures in the converter material 206 may also increase the operating life of the converter material 206, enhance the efficiency of the converter material 206, and/or may enhance the control over the color of light (i.e., the mixture of wavelengths) emitted by the SST assembly 200.
The individual SST devices 204 can include an SST structure 220 carried by a substrate 222. The substrate 222 can be comprised of generally similar materials as the support substrate 202 (e.g., polymers, silicon, metals, metal allows, etc.) and/or other suitable substrate materials. The SST structure 220 can be formed using metal organic chemical vapor deposition (“MOCVD”), molecular beam epitaxy (“MBE”), liquid phase epitaxy (“LPE”), and/or hydride vapor phase epitaxy (“HVPE”), and/or other suitable epitaxial growth techniques known in the arts. In certain embodiments, the SST structure 220 can be formed on a growth substrate and subsequently attached to the substrate 222. In other embodiments, the SST structure 220 can be formed directly on the substrate 222, and therefore the substrate 222 can be made from sapphire and/or other suitable materials for growth substrates. In further embodiments, the substrate 222 can be omitted, and the SST structure 220 can be mounted directly on support substrate 202 (e.g., using a chip-on-board approach).
The SST structure 220 can include an active region between two semiconductor materials. For example, a first semiconductor material can include a P-type semiconductor material (e.g., a P-type gallium nitride (“P-GaN”)), and a second semiconductor material can include an N-type semiconductor (e.g., an N-type gallium nitride (“N-GaN”)). In selected embodiments, the first and second semiconductor materials can individually include at least one of gallium arsenide (GaAs), aluminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), gallium (III) phosphide (GaP), zinc selenide (ZnSe), boron nitride (BN), aluminum gallium nitride (AlGaN), and/or other suitable semiconductor materials. The active region can include a single quantum well (“SQW”), MQWs, and/or a bulk semiconductor material. The term “bulk semiconductor material” generally refers to a single grain semiconductor material (e.g., InGaN) with a thickness between approximately 10 nanometers and approximately 500 nanometers. In certain embodiments, the active region can include an InGaN SQW, GaN/InGaN MQWs, and/or an InGaN bulk material. In other embodiments, the active region can include aluminum gallium indium phosphide (AlGaInP), aluminum gallium indium nitride (AlGaInN), and/or other suitable materials or configurations. In certain embodiments, the SST structure 220 can be configured to emit light in the visible spectrum (e.g., from about 390 nm to about 750 nm), in the infrared spectrum (e.g., from about 1050 nm to about 1550 nm), and/or in other suitable spectra.
As further shown in
Several embodiments of the SST assembly 200 shown in
The SST assembly 200 shown in
In the embodiment illustrated in
Any one of the SST assemblies described above with reference to
From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. For example, in
Claims
1. A method of making a solid state transducer (SST) assembly having a front side from which emissions exit the SST assembly and a back side opposite the front side, the method comprising:
- forming a converter material having a thickness on a forward-facing surface of a support substrate, wherein the forward-facing surface is directed toward an opening of the support substrate at the front side of the SST assembly; and
- mounting an SST structure on a portion of the support substrate spaced apart from the converter material, the SST structure being configured to generate SST emissions, wherein at least a portion of the SST emissions pass through less than the thickness of the converter material before exiting the SST assembly.
2. The method of claim 1 wherein:
- mounting the SST structure comprises positioning the SST structure on a surface of the support substrate facing generally toward the back side of the SST assembly; and
- forming the converter material comprises positioning the converter material a greater distance from the front side of the SST assembly than the SST structure.
3. The method of claim 1 wherein:
- mounting the SST structure comprises positioning the SST structure on a surface of the substrate facing generally toward the front side of the SST assembly; and
- forming the converter material comprises positioning the converter material laterally apart from the SST structure at an angle facing generally toward the front side.
4. The method of claim 1, further comprising forming a cover feature over the SST structure, wherein the cover feature is configured to direct the SST emissions generally toward the converter material.
5. The method of claim 1, further comprising forming a reflective material on the forward-facing surface, wherein the converter material is on the reflective material of the forward-facing surface.
6. The method of claim 1, further comprising forming the support substrate, the support substrate including a flanged portion and an opening at the front side of the SST assembly, the flanged portion having a support surface facing generally toward the back side of the SST assembly and configured to carry the SST structure, wherein the forward-facing surface is positioned toward the back side of the SST assembly relative to the support surface and configured to direct emissions through the opening.
7. The method of claim 6, further comprising forming the forward-facing surface of the substrate such that the forward-facing surface is configured to direct SST emissions toward the front side of the SST assembly.
8. The method of claim 1 mounting the SST structure comprises positioning the SST structure on a surface of the support substrate such that at least a portion of SST emissions that exit the SST assembly at the front side do not pass completely through the thickness of the converter material.
9. The method of claim 1 wherein the thickness of the converter material is such that more SST emissions reflect from an outer surface of the converter material than pass through the converter material.
10. A method of operating a solid-state transducer (SST) assembly having a front side and a back side opposite the front side, the method comprising:
- generating emissions with an SST structure directed generally toward a converter material on a forward-facing surface of a support substrate, the converter material being spaced apart from the SST structure and having a thickness;
- stimulating the converter material with the emissions generated by the SST structure; and
- extracting emissions from the front side of the SST assembly via an opening in the support substrate, wherein at least a portion of the emissions that exit the SST assembly do not pass completely through the thickness of the converter material.
11. The method of claim 10 wherein:
- generating emissions from the SST structure includes generating emissions directed generally toward the back side of the SST assembly, wherein the forward-facing surface is positioned toward the back side of the SST assembly relative to the SST structure; and
- the method further comprises directing the emissions generally toward the front side through the opening using the converter material and/or the forward-facing surface.
12. The method of claim 10 wherein:
- generating emissions from the SST structure includes directing emissions generally toward the front side of the SST assembly, wherein the forward-facing surface is spaced laterally outward from the SST structure and is angled toward the front side; and
- the method further comprises directing the emissions from the SST structure toward the forward-facing surface via a cover feature.
13. The method of claim 12 wherein directing the emissions from the SST structure toward the forward-facing surface via the cover feature further comprises:
- directing a first portion of the emissions laterally outward in a first direction via a first lobe of the cover feature; and
- directing a second portion of the emissions laterally outward in a second direction different from the first direction.
14. The method of claim 10, further comprising reflecting the emissions from the forward-facing surface toward the opening via a reflective portion of the forward-facing surface, wherein the converter material is on the reflective portion.
15. The method of claim 10 wherein extracting emissions from the front side of the SST assembly comprises reflecting the emissions from the SST structure once from an outer surface of the converter material before exiting the SST assembly.
16. The method of claim 10 wherein the thickness of the converter material is such that more SST emissions reflect from an outer surface of the converter material than pass completely through the converter material.
17. A method of making a light emitting diode (LED) assembly having a front side from which emissions exit the LED assembly and a back side opposite the front side, the method comprising:
- forming a wavelength converter material having a thickness on a forward-facing surface of a support substrate, wherein the forward-facing surface is directed toward an opening of the support substrate at the front side of the LED assembly; and
- mounting an LED structure on a portion of the support substrate spaced apart from the wavelength converter material, wherein, when the LED structure generates light, at least a portion of light that exits the LED assembly at the front side does not pass completely through the thickness of the wavelength converter material.
18. The method of claim 17 wherein the thickness of the wavelength converter material is such that more light reflects off of an outer surface of the wavelength converter material than passes completely through the wavelength converter material.
19. The method of claim 17, further comprising:
- forming a reflective material on the forward-facing surface of the substrate before forming the wavelength converter material thereon.
20. The method of claim 17 wherein mounting the LED structure comprises mounting the LED structure on a surface that generally faces the back side of the LED assembly such that, when the LED structure generates light, the light initially travels generally toward the back side of the LED assembly where the light strikes an outer surface of the wavelength converter material and reflects toward the front side to exit the LED assembly.
Type: Application
Filed: May 23, 2019
Publication Date: Sep 12, 2019
Inventors: Martin F. Schubert (Mountain View, CA), Vladimir Odnoblyudov (Eagle, ID)
Application Number: 16/420,463