SEMICONDUCTOR LIGHT EMITTING DEVICE LAMP THAT EMITS LIGHT AT LARGE ANGLES
Embodiments of the invention include a plurality of semiconductor light emitting diodes attached to a mount. A plurality of lenses are disposed over the plurality of semiconductor light emitting diodes. A lens disposed over a semiconductor light emitting diode proximate an edge of the mount is rotationally asymmetrical and is shaped such that for a portion of the lens light emitted at an intensity that is half a maximum intensity is emitted at an angle of at least 70° relative to a normal to a top surface of the semiconductor light emitting diode.
This application claims the benefit or priority of and describes relationships between the following applications: wherein this application is a continuation of U.S. patent application Ser. No. 14/366,294, filed Jun. 18, 2014, which is the National Stage of International Application No. PCT/IB2013/050054, filed Jan. 3, 2013, which claims the priority of provisional application 61/587,156 filed Jan. 17, 2012, all of which are incorporated herein in whole by reference.
FIELD OF THE INVENTIONThe present invention relates to a plurality of semiconductor light emitting devices with at least one lens configured to emit light at large angles.
BACKGROUNDSemiconductor light-emitting devices including light emitting diodes (LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes such as surface-emitting lasers (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include
Group III V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III nitride materials. Typically, III nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions.
LED die. While three LEDs 102, 104, and 106 are shown in
The different light distribution patterns produced by the different types of secondary optics combine to produce an efficient light source having a desired illumination pattern. For example, the first LED may include a lens that produces a light distribution pattern with a maximum intensity at the center while the second LED may use a lens that produces a light distribution pattern with a maximum intensity that surrounds the maximum intensity of the pattern produced by the first LED.
SUMMARYIt is an object of the invention to provide a lamp including semiconductor light emitting diodes that emits light at large angles.
Embodiments of the invention include a plurality of semiconductor light emitting diodes attached to a mount. A plurality of lenses are disposed over the plurality of semiconductor light emitting diodes. A lens disposed over a semiconductor light emitting diode proximate an edge of the mount is rotationally asymmetrical and is shaped such that for a portion of the lens light emitted at an intensity that is half a maximum intensity is emitted at an angle of at least 70° relative to a normal to a top surface of the semiconductor light emitting diode.
A method according embodiments of the invention includes forming a plurality of lenses over a plurality of semiconductor light emitting diodes attached to a mount. A first lens formed over a first semiconductor light emitting diode has a different shape than a second lens formed over a second semiconductor light emitting diode. The first semiconductor light emitting diode is located closer to an edge of the mount than the second semiconductor light emitting diode. The first lens is rotationally asymmetrical and is shaped such that for a portion of the first lens, light emitted at an intensity that is half a maximum intensity is emitted at an angle of at least 70° relative to a normal to a top surface of the first semiconductor light emitting diode.
LEDs are attractive, high efficiency alternatives to conventional incandescent light bulbs. In order to mimic the radiation profile of a conventional incandescent light bulb, an LED lamp must emit light at large angles. For example, as illustrated in
In embodiments of the invention, lenses that create large angle light are formed over LEDs at the edge of an array used in an LED lamp. Though the examples below refer to III-nitride LEDs that emit blue or UV light, semiconductor light emitting devices besides LEDs such as laser diodes and semiconductor light emitting devices made from other materials systems such as other III-V materials, III-phosphide, III-arsenide, II-VI materials, ZnO, or Si-based materials may be used in embodiments of the invention.
A metal p-contact is formed on the p-type region. If a majority of light is directed out of the semiconductor structure through a surface opposite the p-contact, such as in a flip chip device, the p-contact may be reflective. A flip chip device may be formed by patterning the semiconductor structure by standard photolithographic operations and etching the semiconductor structure to remove a portion of the entire thickness of the p-type region and a portion of the entire thickness of the light emitting region, to form a mesa which reveals a surface of the n-type region on which a metal n-contact is formed. The mesa and p- and n-contacts may be formed in any suitable manner. Forming the mesa and p- and n-contacts is well known to a person of skill in the art and is not illustrated in
The p- and n-contacts may be redistributed by a stack of insulating layers and metals as is known in the art to form at least two large electrical pads. One of the electrical pads is electrically connected to the p-type region of the semiconductor structure 20 and the other of the electrical pads is electrically connected to the n-type region of the semiconductor structure 20. Electrical pads may be any suitable conductive material including, for example, copper, gold, and alloys. The electrical pads are electrically isolated from each other by a gap which may be filled with an insulating material such as a dielectric, air, or other ambient gas. The p- and n-contacts, the metal/dielectric stack to redistribute the contacts, and the electrical pads are well known in the art and are illustrated in
In order to use the light emitting devices 15 illustrated in
Lenses of different shapes are formed over different devices 15 in the array on mount 30. For example, lenses 18e formed over devices 15e at the center of the array are shaped to direct light out the top of the devices 15e, i.e. perpendicularly out of the plane of
In some embodiments, the lamps of
The structures illustrated in
Having described the invention in detail, those skilled in the art will appreciate that, given the present disclosure, modifications may be made to the invention without departing from the spirit of the inventive concept described herein. For example, different elements of different embodiments may be combined to form new embodiments. Therefore, it is not intended that the scope of the invention be limited to the specific embodiments illustrated and described.
Claims
1. A structure comprising:
- a plurality of semiconductor light emitting diodes attached to a mount; and
- a plurality of lenses disposed over the plurality of semiconductor light emitting diodes, wherein a lens disposed over a semiconductor light emitting diode proximate an edge of the mount is rotationally asymmetrical and is shaped such that for a portion of the lens, light emitted at an intensity that is half a maximum intensity is emitted at an angle of at least 70° relative to a normal to a top surface of the semiconductor light emitting diode.
2. The structure of claim 1 wherein a lens disposed over a semiconductor light emitting diode proximate a center of the mount is rotationally symmetrical and is shaped such that light emitted at an intensity that is half a maximum intensity is emitted at an angle less than 70° relative to a normal to a top surface of the semiconductor light emitting diode.
3. The structure of claim 1 wherein the lens disposed over a semiconductor light emitting diode proximate an edge of the mount is shaped such that for a portion of the lens, light emitted at an intensity that is half a maximum intensity is emitted at an angle of at least 80° relative to a normal to a top surface of the semiconductor light emitting diode.
4. The structure of claim 1 further comprising a shell disposed over the plurality of light emitting diodes, wherein:
- the structure is configured such that light escapes the shell at an angle of 135° relative to a normal to a top surface of the mount; and
- an amount of light emitted at an angle of 135° relative to a normal to the top surface of the mount is at least 5% of an amount of light emitted at an angle where an intensity of light emitted is at a maximum.
5. The structure of claim 1 wherein the plurality of lenses comprise silicone lenses molded over the plurality of semiconductor light emitting diodes.
6. The structure of claim 1 further comprising a shell disposed over the plurality of semiconductor light emitting diodes.
7. The structure of claim 6 wherein the shell comprises a material that causes scattering of light.
8. The structure of claim 6 wherein the shell extends below a bottom of the mount.
9. The structure of claim 6 wherein the shell and the lens disposed over a semiconductor light emitting diode proximate an edge of the mount are configured such that light escapes the shell at an angle relative to a normal to a top surface of the mount of 135°.
10. A method comprising:
- forming a plurality of lenses over a plurality of semiconductor light emitting diodes attached to a mount, wherein:
- a first lens formed over a first semiconductor light emitting diode has a different shape than a second lens formed over a second semiconductor light emitting diode;
- the first semiconductor light emitting diode is located closer to an edge of the mount than the second semiconductor light emitting diode; and
- the first lens is rotationally asymmetrical and is shaped such that for a portion of the first lens, light emitted at an intensity that is half a maximum intensity is emitted at an angle of at least 70° relative to a normal to a top surface of the first semiconductor light emitting diode.
11. The method of claim 10 wherein the second lens is shaped such that light emitted at an intensity that is half a maximum intensity is emitted at an angle of less than 70° relative to a normal to a top surface of the second semiconductor light emitting diode.
12. The method of claim 10 wherein forming a plurality of lenses comprises:
- positioning a mold over the mount, the mold having indentations corresponding to the plurality of semiconductor light emitting diodes; filling a space between the mold and the mount with silicone; and
- curing the silicone.
13. The method of claim 10 wherein forming a plurality of lenses comprises forming individual lenses over individual semiconductor light emitting diodes before attaching the plurality of semiconductor light emitting diodes to the mount.
14. The method of claim 10 further comprising disposing a shell over the plurality of semiconductor light emitting diodes.
15. The method of claim 14 wherein the shell comprises a material that causes scattering of light.
16. The method of claim 14 wherein the shell extends below a bottom of the mount.
17. The method of claim 14 wherein:
- the shell and the lens disposed over a semiconductor light emitting diode proximate an edge of the mount are configured such that light escapes the shell at an angle relative to a normal to a top surface of the mount of 135°; and
- an amount of light emitted at an angle of 135° relative to a normal to the top surface of the mount is at least 5% of an amount of light emitted at an angle where an intensity of light emitted is at a maximum.
Type: Application
Filed: Sep 11, 2015
Publication Date: Dec 31, 2015
Inventor: SERGE JOEL ARMAND BIERHUIZEN (SAN JOSE, CA)
Application Number: 14/851,657