Textured phosphor conversion layer light emitting diode

• US 8,860,051 B2
• Filed: 11/15/2007
• Issued: 10/14/2014
• Est. Priority Date: 11/15/2006
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Fellows, Natalie N., DenBaars, Steven P., Nakamura, Shuji
• Primary Examiner(s): Tran, Tran
• Application Number:
  US11/940,885
• Publication Number:
  US 20080128730A1
• Time in Patent Office: 2,525 Days
• Field of Search: 257 98-103, 257/E33.061
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/49107 on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 2933/0058 relating to optical field-shaping elements
• CPC Class Codes: H01L 2933/0066 relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/145 with a current-blocking structure
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• CPC Class Codes: H01L 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material
• CPC Class Codes: H01L 33/58 : Optical field-shaping elements
• CPC Class Codes: H01L 33/60 : Reflective elements
• CPC Class Codes: H01L 33/62 : Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

This invention is related to LED Light Extraction for optoelectronic applications. More particularly the invention relates to (Al, Ga, In)N combined with optimized optics and phosphor layer for highly efficient (Al, Ga, In)N based light emitting diodes applications, and its fabrication method. A further extension is the general combination of a shaped high refractive index light extraction material combined with a shaped optical element.

Claims

1. A Light Emitting Diode (LED), comprising:

an LED chip, emitting light at a first wavelength region, wherein the LED chip is grown on a substrate or template and the light is emitted by the LED chip from both front and back sides of the LED chip;

a lead frame, to which the LED chip is attached, wherein the LED chip resides on a transparent plate in the lead frame that allows the light to be extracted out of the LED chip from both the front and back sides of the LED chip;

a molding which acts as a lens, formed on or around the LED chip and optically coupled to the LED chip, wherein the molding is transparent at the first wavelength region; and

a phosphor layer, deposited on top of the molding distant from the LED chip and optically coupled to the molding, the phosphor layer converting the light emitted by the LED chip in the first wavelength region to light in at least a second wavelength region;

wherein at least a portion of a top surface of the phosphor layer is roughened, textured, or patterned, so that the portion of the top surface of the phosphor layer is not normal to the light emitted from the LED chip, to minimize internal reflection of the light within the phosphor layer, thereby increasing total luminous efficacy of the LED; and

wherein a back side of the substrate or template, or the transparent plate upon which the LED chip resides, is roughened, textured or patterned, to increase light extraction from the back side of the LED chip through the transparent plate and through the lead frame.

2. The LED of claim 1, wherein the LED chip is made from a material selected from the group comprising a (Al, Ga, In)N material system, a (Al, Ga, In)As material system, a (Al, Ga, In)P material system, a (Al, Ga, In) AsPNSb material system, a ZnGeN₂ material system, and a ZnSnGeN₂ material system.

3. The LED of claim 1, wherein the molding comprises epoxy, glass, air, and other materials that are transparent at the emission wavelength.

4. The LED of claim 1, wherein at least a portion of a bottom surface of the phosphor layer is shaped.

5. The LED of claim 1, further comprising a transparent electrode on a surface of the LED chip, wherein the transparent electrode comprises a material selected from a group comprising ITO, ZnO, and a thin metal.

6. The LED of claim 5, the LED chip further comprising a current spreading layer.

7. The LED of claim 1, wherein the molding has an inverted cone shape.

8. The LED of claim 1, wherein light is extracted from the LED chip in a direction normal to the emitting surface of the LED chip.

9. The LED of claim 1, further comprising a mirror.

10. The LED of claim 9, wherein the mirror is designed such that light striking the mirror is reflected away from the LED chip.

11. A Light Emitting Diode (LED), comprising:

an LED chip, emitting light at a first wavelength region and having a first refractive index, wherein the LED chip is grown on a substrate or template and the light is emitted by the LED chip from both front and back sides of the LED chip;

a lead frame, to which the LED chip is attached, wherein the LED chip resides on a transparent plate in the lead frame that allows the light to be extracted out of the LED chip from both the front and back sides of the LED chip;

a molding which acts as a lens, formed on or around the LED chip and optically coupled to the LED chip, wherein the molding is transparent at the first wavelength region and has a second refractive index less than the first refractive index, wherein the second refractive index is greater than 1; and

a phosphor layer, deposited on top of the molding distant from the LED chip and optically coupled to the molding, the phosphor layer converting light emitted in the first wavelength region to light in at least a second wavelength region;

wherein at least a portion of a top surface of the phosphor layer is roughened, textured, or patterned, so that the portion of the top surface of the phosphor layer is not normal to the light emitted from the LED chip, to minimize internal reflection of the light within the phosphor layer, thereby increasing total luminous efficacy of the LED; and

wherein a back side of the substrate or template, or the transparent plate upon which the LED chip resides, is roughened, textured or patterned, to increase light extraction from the back side of the LED chip through the transparent plate and through the lead frame.

12. The LED of claim 11, wherein the LED chip is made from a material selected from the group comprising a (Al, Ga, In)N material system, a (Al, Ga, In)As material system, a (Al, Ga, In)P material system, a (Al, Ga, In) AsPNSb material system, a ZnGeN2 material system, and a ZnSnGeN2 material system.

13. The LED of claim 11, wherein at least a portion of a bottom surface of the phosphor layer, the second surface being closer to the LED chip, is also shaped.

14. The LED of claim 11, further comprising a transparent electrode on a surface of the LED chip, wherein the transparent electrode comprises a material selected from a group comprising ITO, ZnO, and a thin metal.

15. The LED of claim 14, the LED chip further comprising a current spreading layer.

16. The LED of claim 11, wherein the molding comprises epoxy, glass, and other materials that are transparent at the emission wavelength.